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The Skeletal System Essay

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Introduction

Axial portion of the skeleton, appendicular portion of the skeleton, functions of the skeleton, relationship between the skeletal system and the muscular system, sexual differences in skeletons, clinical conditions and disorders that affect the skeleton, works cited.

Movement is vital for all of you because it provides you with the opportunity to live your lives to the full. Just as other human beings, you fall and stand up to continue moving forward. But what provides you with this opportunity? It is your skeletal system. It does not only facilitate your physical activity but also supports and protects your bodies. This system consists of hundreds of bones that are full of calcium, which makes them strong enough to carry your weight. Bones are connected with the help of joints that facilitate motion. The majority of you were born with about 300 bones that fuse with the course of time so that now you have only 206 bones. They all are divided into two parts: axial and appendicular skeletons.

Your axial portion of skeleton is composed of “the skull, the vertebral column, and the thoracic cage” ( Skeletal System: Bones and Joints 120). Due to its location, it manages to protect your brain and spinal cord from injuries. In addition to that, it supports the organs in the ventral body cavity so that you do not need to carry them in your hands.

Twenty-two bones that are separated into two parts form the skull. You have 8 bones of the cranial cavity that are known as braincase. They surround your brain so that you do not hurt it when fall or receive a headnut. The rest of the bones (there are 14 of them) form your face. They are tightly connected to one another so that your nose is always in the right place. The only exception is the mandible that makes chewing possible. Otherwise, how would you eat? Minimal movement can also be observed within the middle ears. Each of them includes 3 auditory ossicles that are hidden deep in your head.

The vertebral column, or backbone, usually consists of “7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 1 sacral bone, and 1 coccyx bone” ( Skeletal System: Bones and Joints 125). It is the central axis of the skeleton that has four major curvatures. Normally, the cervical and the lumbar regions curve anteriorly. The thoracic, as well as the sacral and coccygeal regions, curves posteriorly. However, considering the way you sit, abnormal curvatures are widespread.

The thoracic or the rib cage protects your organs and supports them. All in all, human beings have 24 ribs that are divided into 12 pairs, but you can recount them to make sure. They are categorized according to their attachment to the sternum. Thus, a direct attachment by costal cartilages is true (1-7); an attachment by a common cartilage is false (8-12); and the absence of attachment resorts to floating ribs (11-12). The sternum, or breastbone, consists of three parts: “the manubrium, the body, and the xiphoid process” ( Skeletal System: Bones and Joints 129).

Your appendicular skeleton consists of the bones of limbs and girdles so that you have:

• “4 bones in the shoulder girdle (clavicle and scapula each side).
• 6 bones in the arm and forearm (humerus, ulna, and radius).
• 58 bones in the hands (carpals 16, metacarpals 10, phalanges 28, and sesamoid 4).
• 2 pelvis bones.
• 8 bones in the legs (femur, tibia, patella, and fibula).
• 56 bones in the feet (tarsals, metatarsals, phalanges, and sesamoid)” (“The Axial & Appendicular Skeleton” par. 4).

What would you be without this part of skeleton? Imagine that it is a big 3D puzzle, gathering all these bones together in a right order, you will build your arms and legs with all details. These are all movable parts that allow you to run, dance, write, and even hug your nearest and dearest. Even though the axial skeleton seems to be more important because it is connected with your brain, the appendicular portion of the skeleton contains about 60% of all your bones, which means that its importance should not be undervalued.

As you have already understood, your skeleton maintains a lot of different functions. Some of them, such as movement and support, were already mentioned. But let us discuss them all in detail.

• Support. Your bodies are supported by the skeleton so that you can change your position to vertical one and stand strait. Without it, you would be able only to lie because of the gravitation. This function is provided by many bones but the long ones seem to be the leaders in this competition. For instance, those that are in legs, support the trunk. Similarly, vertebras support one another so that eventually the firs one provides support to the skull. In addition to that, they support the organs and ensure that they do not change their positions.
• Protection. The skeleton also protects you. For example, the skull prevents fatal brain injuries. The rib cage protects such vital organs as the heart and lungs. It also takes care of your abdominal organs ensuring that they develop normally.
• Movement. The function of bodily motion allowed you to come here today. However, it is critical to remember that it is maintained not only due to the bones but also with the help of the muscular system.
• Mineral and energy storage. From the outer side of your bones, there is a tissue that serves as a storage. It gathers calcium and phosphorus and withdraws them to maintain appropriate blood levels. In addition to that, mature bones store yellow marrow. It consists of fat almost totally and provides you with energy for various activities.
• Blood-cell formation. The inner core of your bones takes part in the formation of blood cell and platelet. It is known as bone marrow or red marrow. Platelet is vital for you because it ensures your ability to heal wounds while blood cells spread oxygen and destroy infectious cells (CAERT 3).

Have you ever thought of the way our movement are maintained? Even a simple nod of the head requires the cooperation between the skeletal and muscular systems. Muscles ensure movement of our body through the attachment to the bones. All in all, there are about 700 of them, which is an enormous amount that comprises about 50% of your weight.

So what happens in your body when you moves? When you want to move, your brain sends a message for the body to release energy. In medical terms, it is called adenosine triphosphate. Affecting your muscles, it makes them contract or shorten. Shortened muscles pulls bones at their insertion point. Thus, the angle between the bones connected by a joint shortens. Relaxation is maintained when the opposing muscle extends and pulls a bone to its initial position.

Human skeletons seem to be similar, as they contain the same bones. However, you should remember that their characteristics differ depending on the gender. For example, women have lighter pelvis bones that form a shorter cavity with less dimensions. It has less prominent marking for muscles and more circular pelvic brim. The sacral bones of men are longer and narrower, which makes them more massive. Their femur is also longer and heavier. Its texture is rough unlike women’s smooth.

Muscle marking is more developed and shaft is less oblique. The head of men’s femur is larger and trochanters are more prominent. The femoral neck angle in males is more than 125 and in females is less than 125. Women’s sternum is less than twice the length of manubrium and larger in men. Differences in skull include greater capacity, thicker walls, more marked muscular ridges, prominent air sinuses, smoother upper margin of orbit, less vertical forehead, and heavier cheekbones in males.

Hopefully, it will never affect any of you but the skeleton may be affected by tumours that cause bone defects. People may have skeletal developmental disorders including gigantism, dwarfism, osteogenesis imperfecta, and rickets lead to abnormal body sizes, brittle bones, and growth retardation. Bacterial infections cause inflammation and lead to bone destruction.

Decalcification, including the known to you osteoporosis, reduces bone tissue and softens bones. Joint disorders often deal with inflammation. For instance, arthritis. They are often influenced by age and physical activity. In this way, degradation of joints is observed in the elderly but can be delayed due to regular exercises. The abnormal curvatures of the spine may also cause health issues. That is why you should pay attention to your back posture and avoid kyphosis (a hunchback condition), lordosis (a swayback condition), and scoliosis (an abnormal lateral curvature).

CAERT. Structures and Functions of the Skeletal System . 2014. Web.

Skeletal System: Bones and Joints. 2012. Web.

“ The Axial & Appendicular Skeleton. ” TeachPE , 2017. Web.

• Phototransduction Process and Optical Imaging
• "Cellular Metabolism and Disease" by DeBerardinis et al.
• Articular and Muscular Systems
• The Muscular System of a Human Body
• Aspects of the Skeletal System
• Neuropsychological Tests Reliability Following Concussion
• Physicians, Their Roles and Responsibilities
• Prevalence of Sleep Disorders among Medical Students
• Human Physical Performance Under Adverse Conditions
• Tongue and Why It Is Unique
• Chicago (A-D)
• Chicago (N-B)

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Bibliography

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Review Questions

Which function of the skeletal system would be especially important if you were in a car accident?

• storage of minerals
• protection of internal organs
• facilitation of movement
• fat storage

Bone tissue can be described as ________.

• dead calcified tissue
• the skeletal system
• dense, hard connective tissue

Without red marrow, bones would not be able to ________.

• store phosphate
• store calcium
• make blood cells
• move like levers

Yellow marrow has been identified as ________.

• an area of fat storage
• a point of attachment for muscles
• the hard portion of bone
• the cause of kyphosis

Which of the following can be found in areas of movement?

• hematopoiesis
• yellow marrow

The skeletal system is made of ________.

• muscles and tendons
• bones and cartilage
• vitreous humor
• minerals and fat

Most of the bones of the arms and hands are long bones; however, the bones in the wrist are categorized as ________.

• short bones
• sesamoid bones
• irregular bones

Sesamoid bones are found embedded in ________.

Bones that surround the spinal cord are classified as ________ bones.

Which category of bone is among the most numerous in the skeleton?

• sesamoid bone

Long bones enable body movement by acting as a ________.

• counterweight
• resistive force

Which of the following occurs in the spongy bone of the epiphysis?

• bone growth
• bone remodeling
• shock absorption

The diaphysis contains ________.

• the metaphysis
• spongy bone
• compact bone

The fibrous membrane covering the outer surface of the bone is the ________.

Which of the following are incapable of undergoing mitosis?

• osteoblasts and osteoclasts
• osteocytes and osteoclasts
• osteoblasts and osteocytes
• osteogenic cells and osteoclasts

Which cells do not originate from osteogenic cells?

• osteoblasts
• osteoclasts
• osteoprogenitor cells

Which of the following are found in compact bone and cancellous bone?

• Haversian systems
• Haversian canals

Which of the following are only found in cancellous bone?

• Volkmann’s canals
• calcium salts

The area of a bone where the nutrient foramen passes forms what kind of bone marking?

Why is cartilage slow to heal?

• because it eventually develops into bone
• because it is semi-solid and flexible
• because it does not have a blood supply
• because endochondral ossification replaces all cartilage with bone

Why are osteocytes spread out in bone tissue?

• They develop from mesenchymal cells.
• They are surrounded by osteoid.
• They travel through the capillaries.
• Formation of osteoid spreads out the osteoblasts that formed the ossification centers.

In endochondral ossification, what happens to the chondrocytes?

• They develop into osteocytes.
• They die in the calcified matrix that surrounds them and form the medullary cavity.
• They grow and form the periosteum.
• They group together to form the primary ossification center.

Which of the following bones is (are) formed by intramembranous ossification?

• the metatarsals
• the flat bones of the cranium

Bones grow in length due to activity in the ________.

• epiphyseal plate
• perichondrium
• medullary cavity

Bones grow in diameter due to bone formation ________.

• in the medullary cavity
• beneath the periosteum
• in the epiphyseal plate
• within the metaphysis

Which of the following represents the correct sequence of zones in the epiphyseal plate?

• proliferation, reserved, maturation, calcification
• maturation, proliferation, reserved, calcification
• calcification, maturation, proliferation, reserved
• calcification, reserved, proliferation, maturation

A fracture can be both ________.

• open and closed
• open and transverse
• transverse and greenstick
• greenstick and comminuted

How can a fractured diaphysis release fat globules into the bloodstream?

• The bone pierces fat stores in the skin.
• The yellow marrow in the diaphysis is exposed and damaged.
• The injury triggers the body to release fat from healthy bones.
• The red marrow in the fractured bone releases fat to heal the fracture.

In a compound fracture, ________.

• the break occurs at an angle to the bone
• the broken bone does not tear the skin
• one fragment of broken bone is compressed into the other
• broken bone pierces the skin

The internal and external calli are replaced by ________.

• hyaline cartilage
• trabecular bone
• osteogenic cells

The first type of bone to form during fracture repair is ________ bone.

Wolff’s law, which describes the effect of mechanical forces in bone modeling/remodeling, would predict that ________

• a right-handed pitcher will have thicker bones in his right arm compared to his left.
• a right-handed cyclist will have thicker bones in her right leg compared to her left.
• a broken bone will heal thicker than it was before the fracture.
• a bed-ridden patient will have thicker bones than an athlete.

Calcium cannot be absorbed from the small intestine if ________ is lacking.

Which one of the following foods is best for bone health?

• leafy green vegetables

Which of the following hormones are responsible for the adolescent growth spurt?

• estrogen and testosterone
• calcitonin and calcitriol
• growth hormone and parathyroid hormone
• thyroxine and progesterone

With respect to their direct effects on osseous tissue, which pair of hormones has actions that oppose each other?

• estrogen and progesterone
• calcitonin and parathyroid hormone

When calcium levels are too high or too low, which body system is primarily affected?

• skeletal system
• endocrine system
• digestive system
• nervous system

All of the following play a role in calcium homeostasis except

• parathyroid hormone

Which of the following is most likely to be released when blood calcium levels are elevated?

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Musculoskeletal system

Author: Gordana Sendić, MD • Reviewer: Jana Vasković, MD Last reviewed: November 03, 2023 Reading time: 28 minutes

The musculoskeletal system (locomotor system) is a human body system that provides our body with movement , stability, shape, and support. It is subdivided into two broad systems: 

• Muscular system , which includes all types of muscles in the body. Skeletal muscles, in particular, are the ones that act on the body joints to produce movements. Besides muscles, the muscular system contains the tendons which attach the muscles to the bones.
• Skeletal system , whose main component is the bone . Bones articulate with each other and form the joints , providing our bodies with a hard-core, yet mobile, skeleton. The integrity and function of the bones and joints is supported by the accessory structures of the skeletal system; articular cartilage , ligaments , and bursae .

Besides its main function to provide the body with stability and mobility, the musculoskeletal system has many other functions; the skeletal part plays an important role in other homeostatic functions such as storage of minerals (e.g., calcium) and hematopoiesis, while the muscular system stores the majority of the body's carbohydrates in the form of glycogen.

This article will introduce you to the anatomy and function of the musculoskeletal system.

Muscular system

Muscle contraction, functions of the muscular system, functions of the skeletal system, osteoporosis, muscular dystrophy, related articles.

The muscular system is an organ system composed of specialized contractile tissue called the muscle tissue . There are three types of muscle tissue, based on which all the muscles are classified into three groups: 

• Cardiac muscle , which forms the muscular layer of the heart ( myocardium ) 
• Smooth muscle , which comprises the walls of blood vessels and hollow organs 
• Skeletal muscle , which attaches to the bones and provides voluntary movement. 

Based on their histological appearance, these types are classified into striated and non-striated muscles; with the skeletal and cardiac muscles being grouped as striated , while the smooth muscle is non-striated . The skeletal muscles are the only ones that we can control by the power of our will, as they are innervated by the somatic part of the nervous system . In contrast to this, the cardiac and smooth muscles are innervated by the autonomic nervous system , thus being controlled involuntarily by the autonomic centers in our brain .

Skeletal muscles

The skeletal muscles are the main functional units of the muscular system. There are more than 600 muscles in the human body. They vary greatly in shape in size, with the smallest one being the stapedius muscle in the inner ear, and the largest one being the quadriceps femoris muscle in the thigh. 

The skeletal muscles of the human body are organized into four groups for every region of the body:

• Muscles of the head and neck , which include the muscles of the facial expression , muscles of mastication , muscles of the orbit , muscles of the tongue , muscles of the pharynx , muscles of the larynx , and muscles of the neck
• Muscles of the trunk , which include the muscles of the back , anterior and lateral abdominal muscles , and muscles of the pelvic floor
• Muscles of the upper limbs , which include muscles of the shoulder , muscles of the arm , muscles of the forearm and muscles of the hand
• Muscles of the lower limbs , which include hip and thigh muscles , leg muscles and foot muscles

The fact that there are more than 600 muscles in the body can be quite intimidating. If you’re tired of all the big, comprehensive anatomy books, take a look at our condensed muscle anatomy reference charts , which contain all the muscle facts in one place organized into neat tables!

Structurally, the skeletal muscles are composed of the skeletal muscle cells which are called the myocytes (muscle fibres, or myofibrils ). Muscle fibers are specialized cells whose main feature is the ability to contract. They are elongated, cylindrical, multinucleated cells bounded by a cell membrane called sarcolemma . The cytoplasm of skeletal muscle fibers ( sarcoplasm ), contains contractile proteins called actin and myosin. These proteins are arranged into patterns, forming the units of contractile micro-apparatus called sarcomeres . 

Each muscle fiber is enclosed with a loose connective tissue sheath called endomysium . Multiple muscle fibers are grouped into muscle fascicles or muscle bundles, which are encompassed by their own connective tissue sheath called the perimysium . Ultimately, a group of muscle fascicles comprises a whole muscle belly which is externally enclosed by another connective tissue layer called the epimysium . This layer is continuous with yet another layer of connective tissue called the deep fascia of skeletal muscle, that separates the muscles from other tissues and organs. 

This structure gives the skeletal muscle tissue four main physiological properties:

• Excitability - the ability to detect the neural stimuli ( action potential );
• Contractibility - the ability to contract in response to a neural stimulus;
• Extensibility - the ability of a muscle to be stretched without tearing; 
• Elasticity - the ability to return to its normal shape after being extended.

Learn everything about the skeletal muscle structure with our articles, video tutorials, quizzes and labelled diagrams.

The most important property of skeletal muscles is its ability to contract . Muscle contraction occurs as a result of the interaction of myofibrils inside the muscle cells. This process either shortens the muscle or increases its tension, generating a force that either facilitates or slows down a movement. 

There are two types of muscle contraction; isometric and isotonic. A muscle contraction is deemed as isometric if the length of the muscle does not change during the contraction, and isotonic if the tension remains unchanged while the length of the muscle changes. There are two types of isotonic contractions: 

• Concentric contraction , in which the muscle shortens due to generating enough force to overcome the imposed resistance. This type of contraction serves to facilitate any noticeable movement (e.g. lifting a barbell or walking on an incline).
• Eccentric contraction , in which the muscle stretches due to the resistance being greater than the force the muscle generates. During an eccentric contraction, the muscle maintains high tension. This type of contraction usually serves to slow down a movement (e.g. lowering a barbell or walking downhill).

The sequence of events that results in the contraction of a muscle cell begins as the nervous system generates a signal called the action potential . This signal travels through motor neurons to reach the neuromuscular junction , the site of contact between the motor nerve and the muscle. A group of muscle cells innervated by the branches of a single motor nerve is called the motor unit .

The incoming action potential from the motor nerve initiates the release of acetylcholine (ACh) from the nerve into the synaptic cleft , which is the space between the nerve ending and the sarcolemma. The ACh binds to the receptors on the sarcolemma and triggers a chemical reaction in the muscle cell. This involves the release of calcium ions from the sarcoplasmic reticulum , which in turn causes a rearrangement of contractile proteins within the muscle cell. The main proteins involved are actin and myosin, which in the presence of ATP, slide over each other and pull on the ends of each muscle cell together, causing a contraction. As the nerve signal diminishes, the chemical process reverses and the muscle relaxes.

A tendon is a tough, flexible band of dense connective tissue that serves to attach skeletal muscles to bones. Tendons are found at the distal and proximal ends of muscles, binding them to the periosteum of bones at their proximal ( origin ) and distal attachment ( insertion ) on the bone. As muscles contract, the tendons transmit the mechanical force to the bones, pulling them and causing movement.

Being made of dense regular connective tissue, the tendons have an abundance of parallel collagen fibers, which provide them with high tensile strength (resistance to longitudinal force). The collagen fibers within a tendon are organized into fascicles, and individual fascicles are ensheathed by a thin layer of dense connective tissue called endotenon . In turn, groups of fascicles are ensheathed by a layer of dense irregular connective tissue called epitenon . Finally, the epitenon is encircled with a synovial sheath and attached to it by a delicate connective tissue band called mesotenon .

Learn more about the microstructure of tendon in this study unit:

The main function of the muscular system is to produce movement of the body. Depending on the axis and plane, there are several different types of movements that can be performed by the musculoskeletal system. Some of the most important ones include:

• Flexion and extension : movement of decreasing or increasing the angle between the bones involved in the movement, respectively. This motion takes place in the sagittal plane around a frontal axis. An example of flexion is bending the leg at the knee joint , whereas extension would be straightening knee from a flexed position.
• Adduction and abduction : movements of bringing the parts of the body towards or away from the midline, respectively. These movements are carried out in the frontal plane around a sagittal axis. For example, abduction of the arm at the shoulder joint involves moving the arm away from the side of the body, while adduction involves bringing it back towards the body.
• Rotation is the movement in which a part of the body rotates around its vertical (longitudinal) axis in the transverse plane. This movement is defined relative to the midline, where internal rotation involves rotating the segment towards to the midline, while external rotation involves moving it away from the midline. Examples include lateral or medial rotation of the thigh .
• Supination and pronation are special types of rotatory movements usually used to describe the movements of the forearm . Supination is essentially a lateral rotation of the forearm which turns the palms anteriorly (if the arm is anatomical position) or superiorly, when the elbow is flexed. These movements are also sometimes used to describe movements in the ankle and foot , in which supination means rolling the foot outwards, while pronation means rolling the foot inwards.

Both during movement and stationary positions, muscles contribute to the overall support and stability of joints . Many muscles and their tendons pass over joints and thereby stabilize the articulating bones and hold them in position. In addition, the muscles also play an important role in maintaining posture . While the movements occur mainly due to muscles intermittently contracting and relaxing, the posture is maintained by a sustained tonic contraction of postural muscles. These muscles act against gravity and stabilize the body during standing or walking. The postural muscles include the muscles of the back and abdominal muscles.

Another important function of muscles is heat production . Muscle tissue is one of the most metabolically active tissues in the body, in which approximately 85 percent of the heat produced in the body is the result of muscle contraction. This makes the muscles essential for maintaining normal body temperature. 

Wondering what’s the best way to learn and understand the functional anatomy of the muscles? Check out our 3D muscle anatomy videos !

To improve your understanding of muscular system terminology, take a closer look at some commonly used roots, prefixes and suffixes related to the muscular system in the video below.

How well do you know the main muscles of the body? Test your knowledge with our quiz in different difficulty levels!

Skeletal system

The adult human skeleton is composed of 206 bones and their associated cartilages. The bones are supported by ligaments, tendons, bursae, and muscles. The bones of the body are grouped within the two distinct divisions:

• Axial skeleton , that includes the bones along the long axis of the body. The axial skeleton consists of the vertebral column , bones of the head and bones of the thoracic cage .
• Appendicular skeleton , that involves the bones of the shoulder and pelvic girdle , as well as the bones of the upper and lower extremities .

Bones are rigid structures made of calcified dense connective tissue. Bone tissue is composed of a mineralized bone matrix that consists of type 1 collagen fibers dispersed throughout the ground substance . The cellular component of the bones is represented by three types of specialized bone cells called osteocytes, osteoblasts and osteoclasts . 

The bones consist of two distinct layers that differ in histological appearance and characteristics; 

• Compact (cortical) bone is the outer much denser layer of the bone which gives it its smooth, white, and solid appearance. The outer surface of the compact bone is covered with a layer of dense connective tissue called the periosteum. On its inner surface, the compact bone is covered with endosteum , which is the boundary between the compact and spongy bones .
• Spongy (cancellous) bone is the deep airy layer of the bone. Unlike the compact bone, spongy bone is highly vascularized and more metabolically active. It is typically found within the ends of long bones and in the vertebrae. In certain bones, like the hip bone , sternum or femur, the central part of spongy bone houses the bone marrow, which is the site of hematopoiesis in the adult.

Types of bones

Bones can be classified according to their shapes as follows:

• Long bones have a tubular shape, with a longer longitudinal and a shorter transverse diameter. They are composed mostly of compact bone, while the spongy bone and bony marrow fill the ends of the bones. Examples of long bones include the humerus , ulna , tibia and clavicle . 
• Short bones have a roughly cuboid or round shape, and only contain a thin layer of compact bone surrounding the spongy bone. Examples include the tarsal and carpal bones .
• Flat bones are mostly thin, flattened and usually curved. They contain two parallel layers of compact bones surrounding a layer of spongy bone. Examples include most of the skull bones , scapula , sternum and sacrum .
• Sesamoid bones are small, rounded unique types of bones that are embedded in muscle tendons where the tendon passes over a joint. The largest sesamoid bone in the body is the patella , but several other smaller sesamoid bones can be found in the hand and foot, usually in close proximity to the joints.
• Irregular bones do not fit into any of the other categories. Generally, irregular bones contain foramina through which soft tissue and neurovascular structures pass. Examples include the vertebrae , hip bone and some bones of the skull.

Wondering how to cut time in learning the bones of the body? Try our skeletal system quizzes !

A typical long bone consists of a long shaft ( diaphysis ) that extends into a neck ( metaphysis ) and head ( epiphysis ) on its proximal and distal ends. It also features various markings and formations that give passage to neurovascular structures, as well as the attachment sites to the ligaments and tendons. Some of those features include:

• Sulcus – a shallow groove on the bone surface (e.g. radial sulcus of humerus)
• Condyle – rounded articular area (e.g. lateral condyle of tibia)
• Epicondyle – eminence superior to a condyle (medial epicondyle of femur)
• Crest – ridge of bone (e.g. iliac crest)
• Facet – smooth, flat area, usually covered with cartilage (e.g. articular facet on vertebrae)
• Foramen – passage through a bone (e.g. foramen magnum on the occipital bone)

Cartilage is a flexible connective tissue found in multiple organ systems of the body. Cartilage is composed of specialized cells called chondrocytes , collagen fibers and abundant ground substance rich in proteoglycan and elastin fibers.

Cartilage is classified into the following types based on its composition:

• Hyaline cartilage is composed of type II collagen and an abundance of ground substance, which gives it a glossy appearance. It is the most abundant type of cartilage found in joints (articular cartilage), as well as the nose, larynx , trachea and ribs .
• Elastic cartilage is similar to hyaline cartilage but contains more elastic fibers. It is found in structures such as the pinna of the ear , auditory tube and epiglottis .
• Fibrocartilage is composed of plenty of collagen fibers type I and a smaller amount of ground substance. Examples of fibrocartilage include intervertebral discs , pubic and other symphyses.

The musculoskeletal system specifically contains articular cartilage, a type of cartilage that lines the articulating surfaces of bones. The articular cartilage provides congruence to the articulating bones and allows them to bear weight and glide over each other with very little friction. 

Each bone of the musculoskeletal system is connected to one or more bones via a joint . Joints provide a fulcrum to the bones, on which they pivot and thereby allow movements of body parts. However, movement is not a necessary attribute of a joint as some joints do not move, such as joints between the bones of the skull. The integrity or stability of a joint is provided by several factors including the bony congruence and structures that cross the joint, such as tendons and ligaments.

Based on the type of tissue that holds the neighboring bones together and the range of motion they exhibit, joints can be classified into the following:

• Synovial joints are freely mobile joints in which the bones are not in direct contact, but are separated by a potential space called the synovial cavity . The synovial cavity is lined by a synovial membrane that secretes the synovial fluid which nourishes and lubricates the articulating surfaces in order to reduce friction. The articulating bones in most synovial joints are lined with hyaline cartilage. These joints usually have a wide range of motion, which is defined by the joint capsule, the supporting ligaments and muscles that cross the joint. Examples of synovial joints include the knee, shoulder, sternoclavicular and elbow joints .
• Fibrous joints are the articulations in which the bones are connected by dense fibrous connective tissue. The bones in fibrous joints are firmly held together so that the joint allows negligible movement. Fibrous joints are found between the cranial sutures , the distal tibiofibular and cuboideonavicular joints.
• Cartilaginous joints are articulations in which the bones are connected by cartilage. The bones have a range of motion between synovial and fibrous joints. Cartilaginous joints are subdivided into synchondrosis (e.g. costochondral joints ) and symphysis joints (e.g. pubic symphysis).

According to the movements they allow and/or the shape of their articulating surface, the synovial joints can be further subdivided into 6 major types:

• Ball and socket joints (e.g. hip joint )
• Condyloid joints (e.g. metacarpophalangeal joint)
• Hinge joints (e.g. elbow joint)
• Pivot joints (e.g. atlanto-axial joint)
• Saddle joints (e.g. carpometacarpal joint)
• Plane joints (e.g. acromioclavicular joint )

Ligaments are fibrous bands made of dense regular connective tissue which are similar in structure to tendons. Unlike the tendons that connect muscles to bone, the ligaments connect bone to bone . Besides the musculoskeletal system, the ligaments are also found in many other parts of the body, where they usually stabilize and hold internal organs in place and transmit neurovascular structures.

In the musculoskeletal system, ligaments stabilize the articulating bones and reinforce the joints. Depending on their anatomic position relative to the joint capsule, ligaments are classified into:

• Capsular ligaments are essentially thickenings of the joint capsule that form either elongated bands or triangular structures. These ligaments serve to reinforce the integrity of the joint capsule. An example of the capsular ligament is the iliofemoral ligament of the hip joint.
• Intracapsular ligaments are the ligaments that lie internal to the joint capsule. These ligaments reinforce the connection of the articulating surfaces of the joint, but allow a far wider range of motion than other ligaments. Examples include anterior and posterior cruciate ligament of the knee joint.
• Extracapsular ligaments are ligaments that lie outside the joint capsule. These ligaments provide the most stability to the articulating bones, and are important for preventing dislocations. Extracapsular ligaments can lie in close proximity (e.g. medial collateral ligament of the ankle joint ) or a bit further from the joint capsule ( vertebral ligaments ).

Bursae are small sac-like outpouchings of the joint cavity lined by synovial membrane. They are found around the joints, providing cushioning of the associated bones, tendons and muscles and reducing friction between adjacent structures.

The majority of synovial bursae are located near the large joints of the arms and legs. For example, one of the bursae of the knee joint is the suprapatellar bursa , found superior to the patella, between the femur and the tendon of the quadriceps femoris muscle . The suprapatellar bursa allows for these structures to slide over each other without friction during flexion and extension of the knee joint.

To improve your understanding of skeletal system terminology, take a closer look at some commonly used roots, prefixes and suffixes related to the skeletal system in the video below.

Time for a skeletal system workout with our integrated quiz!

The skeletal system serves a variety of functions. The bones give the shape to the body and provide the site of attachment to muscles, tendons, ligaments and cartilage. These tissues function together as a whole to generate a force that provides the biomechanical basis of movement .

Due to its structural integrity, the skeletal system protects the internal organs, most importantly the brain, which is surrounded by the skull, as well as the heart and lungs , which are protected by the rib cage. 

Moreover, the skeletal system serves several metabolic functions . The bones are the storage site of important minerals, most notably calcium and phosphorus. This makes the bones essential for balancing calcium levels in the blood, which is regulated by adjusting the rate of bone resorption.

Lastly, the bone marrow found in spongy bone is the site of hematopoiesis , which is a process of production of new blood cells. Cells that are produced in the bone marrow are red blood cells, platelets and white blood cells, such as monocytes, granulocytes and lymphocytes .

We created a custom summary quiz about the anatomy and histology of the main features of the musculoskeletal system. You can adjust and filter individual structures to make this quiz your own!

Clinical correlation

There is a variety of conditions that affect the muscles, bones, and joints. Disorders of the musculoskeletal system may range from diseases to minor physical disabilities. The following are some clinical conditions of the musculoskeletal system:

Osteoporosis is a condition that affects bone strength (the word osteoporosis literally means "porous bones"). It is a condition in which the bones become fragile and brittle, leading to a higher risk of fractures than in normal bone. As a result, even a minor bump or accident can cause serious fractures.

Osteoporosis is the “bone of the old”, especially, in women. The hard, rock-like quality of bone is dependent upon calcium. When too much calcium is dissolved from bones or not enough is replaced, bones lose density and are easily fractured. Estrogen, the female sex hormone, helps maintain proper calcium levels in bones. Once the ovaries stop producing the hormone, women are at higher risk of developing osteoporosis. A collapse of bony vertebrae of the spinal column results in loss of height and stooped posture. Hip fractures are a common occurrence.

Sarcopenia is a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength with a risk of adverse outcomes such as physical disability, poor quality of life and death.

Arthritis is a group of conditions affecting the joints . These conditions cause damage to the joints, usually resulting in pain and stiffness due to aging. Arthritis can affect many different parts of the joint and nearly every joint in the body.

As an individual ages, the joint tissues become less resilient to wear and tear and start to degenerate. This degeneration manifest as swelling, pain, and often-times, loss of mobility of joints. Changes occur in both joint soft tissues and the articulating bones, a condition called osteoarthritis . A more serious form of disease is called rheumatoid arthritis . The latter is an autoimmune disease wherein the body produces antibodies against joint tissues causing chronic inflammation resulting in severe joint damage, pain and immobility.

Muscular dystrophy is a group of muscle diseases that weaken the musculoskeletal system and hamper locomotion. Muscular dystrophies are characterized by progressive skeletal muscle weakness , defects in muscle proteins, and the death of muscle fibres (muscle cells) and tissue.

It is a group of inherited diseases in which the muscles that control movement progressively weaken. The prefix, dys-, means abnormal, while the root, -trophy, refers to maintaining normal nourishment, structure and function. The most common form in children is called Duchenne muscular dystrophy and affects only males. It usually appears between the ages of 2 to 6 and the afflicted live typically into late teens to early 20s.

Other conditions involving the musculoskeletal system include:

• Lupus erythematosus
• Myasthenia gravis
• Rotator cuff tear
• Carpal tunnel syndrome
• Osteomalacia

References:

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
• Netter, F. (2019). Atlas of Human Anatomy (7th ed.). Philadelphia, PA: Saunders.
• Standring, S. (2016). Gray's Anatomy (41st ed.). Edinburgh: Elsevier Churchill Livingstone.
• Ross, Lawrence M; Lamperti, Edward D, eds. (2006). Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. 
• R.M.H McMinn: Last's anatomy (Regional and Applied), 9th edition, Ana-Maria Dulea (2014

Illustrations:

• Musculoskeletal system - Irina Münstermann
• Eccentric and concentric muscle contractions (diagram) - Yousun Koh

Articles within this topic:

• Ball and socket joint
• Complete list of bone markings
• Ellipsoid joint
• Head and neck anatomy
• Hinge-joint
• How to learn all muscles with quizzes and labeled diagrams
• Intercostal muscles
• Lateral abdominal muscles
• Learn skull anatomy with skull bones quizzes and diagrams
• Lower limb anatomy
• Muscle anatomy reference charts
• Muscles of the neck: An overview
• Muscles of the trunk
• Musculoskeletal system development
• Parietal bone
• Pectoralis minor muscle
• Pivot joint
• Rectus abdominis muscle
• Synovial membrane
• Upper limb muscles and movements

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Chapter 11 Answers: Skeletal System

11.2 introduction to the skeletal system: review questions and answers.

• What is the skeletal system? How many bones are there in the adult skeleton? The skeletal system is the organ system that provides an internal framework for the human body. In adults, the skeleton contains 206 bones.
• Describe the composition of bones. Bones are made of dense connective tissues, mainly the tough protein collagen. Bones also contain blood vessels, nerves, and other tissues. Bones are hard and rigid due to deposits of calcium and other mineral salts within their living tissues.
• Besides bones, what other organs are included in the skeletal system? Besides bones, the skeletal system includes cartilage and ligaments.
• Identify the two major divisions of the skeleton. The two major divisions of the skeleton are the axial skeleton, which includes the skull, spine, and rib cage; and the appendicular skeleton, which includes the appendages and the girdles that attach them to the axial skeleton.
• List several functions of the skeletal system. Answers may vary. Sample answer: Functions of the skeletal system include supporting the body, giving the body shape, protecting internal organs, allowing the body to move, producing blood cells, storing minerals, helping maintain mineral homeostasis, and producing endocrine hormones.
• Self-marking
• If a person has a problem with blood cell production, what type of bone tissue is most likely involved? Explain your answer. Red marrow, because that is where blood cells are produced in the bone.
• What are three forms of homeostasis that the skeletal system regulates? Briefly explain how each one is regulated by the skeletal system. The skeletal system helps maintain mineral homeostasis by regulating the level of calcium and other minerals in the blood by storing or releasing them from bones as needed. This process also helps maintain homeostasis in blood pH because the minerals are basic. Bones also regulate blood glucose and fat deposition through the secretion of the endocrine hormone osteocalcin.
• What do you think would happen to us if we did not have ligaments? Explain your answer. Answers may vary. Sample answer:  Ligaments hold bones together and keep them in place, so without ligaments we would be a pile of bones and internal organs inside a bag of skin.
• What is a joint? How is cartilage related to joints? Identify one joint in the human body and describe its function. Answers may vary. Sample answer:  A joint is an area where two or more bones meet. Cartilage covers the ends of bones at joints, creating a smooth surface for the bones to move over. The elbow is a joint in the human body that allows the bones to move like a lever in order to bend and straighten the arm.

11.3 Divisions of the Skeletal System: Review Questions and Answers

• What are the advantages of an S-shaped vertebral column? The advantages of an S-shaped vertebral column include allowing it to absorb shocks and to distribute the weight of the body.
• What is the rib cage? What is its function?  What types of ribs are there? The rib cage includes 12 thoracic vertebrae, the sternum, and 12 pairs of ribs. Its function is to hold and protect the organs of the upper part of the trunk, including the heart and lungs.
• Explain the advantage of having some ribs that are not attached directly to the sternum. Answers may vary. Sample answer:  The false ribs and floating ribs are not attached directly to the sternum. This allows them to move more easily to accommodate the movements of breathing.
• What is the shoulder girdle? Why does it allow considerable upper limb mobility? The shoulder girdle attaches the upper limbs to the trunk of the body. It includes a right and left clavicle and a right and left scapula. The shoulder girdle allows considerable upper limb mobility because it is connected to the axial skeleton only by muscles.
• Describe some of the similarities between the upper limbs and the lower limbs. Answers may vary. Sample answer: Both the upper limbs and lower limbs have 30 bones. Also, both limbs have one bone in the top of the limb and two bones in the bottom of the limb. Finally, both the hands and feet have 14 phalanges.
• Describe the pelvic girdle and the bones it contains. The pelvic girdle is the part of the skeleton that attaches the legs to the trunk of the body and supports the organs of the abdomen. It consists of two halves that are fused together in adults. Each half consists of three bones: the ilium, pubis, and ischium.

11.4 Structure of Bone: Review Questions and Answers

• Describe osseous tissue. Osseous tissue is the main tissue in bones. It is a type of connective tissue consisting mainly of a collagen matrix that is mineralized with calcium and phosphorus crystals.
• Why are bones hard, but not brittle? Bones are hard but not brittle because they are made of a combination of flexible collagen and mineral crystals.
• Compare and contrast the compact and spongy bone. The two main types of osseous tissue are compact bone tissue and spongy bone tissue. Both types consist of the same kinds of cells, but the cells have different arrangements in the two types of bone. As a result, compact bone is smooth and dense, whereas spongy bone is porous and light. Compact bone makes up the outer layer of bones, whereas spongy bone is found inside many bones.
• What non-osseous tissues are found in bones? Non-osseous tissues found in bones include nerves, blood vessels, bone marrow, and periosteum.
• List four types of bone cells and their functions. Four types of bone cells are osteoblasts, which form new organic bone matrix and mineralize it; osteoclasts, which break down bone; osteocytes, which regulate the formation and breakdown of bone; and osteogenic cells, which form new bone cells.
• Identify six types of bones. Give an example of each type. The six types of bones are long bones such as limb bones, short bones such as wrist bones, sesamoid bones such as the patella, sutural bones in skull sutures, and irregular bones such as vertebrae.
• Compare and contrast yellow bone marrow and red bone marrow. Answers may vary. Sample answer:  Yellow and red bone marrow are both found in the marrow cavity of bones, but yellow marrow is mostly fat and red marrow produces blood cells. All marrow in newborns is red, but much of it changes to yellow marrow in adults.
• Which type of bone cell divides to produce new bone cells? Where is this cell type located?  Osteogenic cells, which are located in the periosteum covering the bone.
• Where do osteoblasts and osteocytes come from? How are they related to each other? Osteoblasts are produced by osteogenic cells. Osteocytes, in turn, arise from osteoblasts that have become trapped in bone matrix.
• Which type of bone is embedded in tendons? Sesamoid bone.

11.5 Bone Growth, Remodeling, and Repair: Review Questions and Answers

• Outline how bone develops starting early in the fetal stage, and through the age of skeletal maturity.  Early in the development of a human fetus, the skeleton is made almost entirely of cartilage. The relatively soft cartilage gradually turns into hard bone in the process called ossification. It begins at a primary ossification centre in the middle of bone and later also occurs at secondary ossification centres in the ends of bone. Ossification of some bones continues through childhood, until the late teens or early twenties when skeletal maturity occurs. After that, bones can no longer grow in length because the areas of ossification have met and fused.
• Describe the process of bone remodeling. When does it occur? Bone remodeling is the process in which osteoclasts resorb bone and osteoblasts make new bone to replace it. It occurs continuously throughout life, with about ten per cent of bone mass being remodeled each year in adults.
• What purposes does bone remodeling serve? Bone remodeling serves several purposes. It shapes the skeleton, repairs tiny flaws in bones, and helps maintain mineral homeostasis in the blood.
• Define bone repair. How long does this process take? Bone repair is the natural process in which a bone repairs itself following a bone fracture. This process may take several weeks.
• Explain how bone repair occurs. In the process of bone repair, periosteum (the connective tissue covering bone) produces precursor cells that develop into osteoblasts. Then the osteoblasts form new bone matrix to heal the fracture.
• Identify factors that may affect bone repair. Bone repair may be affected by diet, age, pre-existing bone disease, or other factors.
• If there is a large region between the primary and secondary ossification centres in a bone, is the person young or old? Explain your answer. If there is a large region between the primary and secondary ossification centres in a bone, the person is young, mostly likely well under 18 years of age. This is because as a person grows older, the primary and secondary ossification centres grow towards each other and eventually meet and fuse around the ages of 18 to 25.
• If bones can repair themselves, why are casts and pins sometimes necessary in the process? Answers may vary. Sample answer:  Bones can repair themselves, but casts and pins are sometimes needed to hold the pieces of the broken bone together in the right positions so that they can fuse together correctly.
• When calcium levels are low, which type of bone cell causes the release of calcium to the bloodstream? Osteoclasts.
• Which tissue and bone cell type are primarily involved in bone repair after a fracture?  After a bone fracture, the periosteum produces cells that develop into osteoblasts, which form new bone tissue.
• Describe one way in which hormones are involved in bone remodeling. Answers will vary. Sample answer:  Growth hormone regulates the rate at which osteoblasts create new bone during bone remodeling.

11.6 Joints: Review Questions and Answers

• What are joints? Joints are locations at which bones of the skeleton connect with one another.
• What are two ways that joints are commonly classified? Joints can be classified structurally or functionally, but there is significant overlap between the two types of classifications.
• How are joints classified structurally? The structural classification of joints depends on the type of tissue that binds the bones to each other at the joint. There are three types of joints in the structural classification: fibrous, cartilaginous, and synovial joints.
• Describe the functional classification of joints. The functional classification of joints is based on the type and degree of movement that they allow. There are three types of joints in the functional classification: immovable, partly movable, and movable joints.
• How are movable joints classified? Movable joints are classified according to the type of movement they allow.
• Name the six classes of movable joints. Describe how they move and give an example of each. The six classes of movable joints are pivot, hinge, saddle, plane, condyloid, and ball-and-socket joints. A pivot joint allows one bone to rotate around another. A hinge joint allows back and forth movement like the hinge of a door. A saddle joint allows two different types of movement. For example, the thumb is a saddle joint that permits the thumb to move toward and away from the index finger and also to cross over the palm toward the little finger. A plane joint allows two bones to glide over one another. A condyloid joint is one in which an oval-shaped head on one bone moves in an elliptical cavity in another bone, allowing movement in all directs except rotation around an axis. A ball-and-socket joint allows the greatest range of movement of any movable joint. It allows forward and backward as well as upward and downward motions. It also allows rotation in a circle.
• Which specific type of moveable joint do you think your knee joint is? Explain your reasoning. Answers may vary. Sample answer:  I think the knee joint is a hinge joint like the elbow because it allows back and forth movement like a hinge.
• Explain the difference between cartilage in a cartilaginous joint and cartilage in a synovial joint. Cartilage in a cartilaginous joint actually holds the bones together, whereas in a synovial joint, the cartilage covers the ends of the bones which are held together by ligaments.
• Why are fibrous joints immovable? Fibrous joints are immovable because they are made of dense connective tissue rich in collagen fibres, which does not allow movement.
• What is the function of synovial fluid? Synovial fluid cushions the ends of bones.

11.7 Disorders of the Skeletal System: Review Questions and Answers

• A definition of osteoporosis Osteoporosis is an age-related disorder in which bones lose mass, weaken, and break more easily than normal bones. The basic cause of osteoporosis is an imbalance between bone formation and bone resorption in bone remodeling that results in a net loss of bone mass.  In simpler terms, osteoporosis occurs when the creation of new bone doesn’t keep up with the loss of old bone.This may occur as a side effect of other disorders or certain medications.
• Causes Osteoporosis causes bones to become weak and brittle — so brittle that a fall or even mild stresses such as bending over or coughing can cause a fracture. Osteoporosis-related fractures most commonly occur in the hip, wrist or spine.
• Dangers of living with the disease Osteoporosis is dangerous because it often leads to bone fractures. Osteoporosis itself is rarely fatal and generally doesn’t even cause symptoms, but complications of fractures often are debilitating and may lead to death.
• Canadian osteoporosis statistics
• Risk factors Risk factors for osteoporosis include older age, female sex, European or Asian ancestry, family history of osteoporosis, short stature and small bones, smoking, alcohol consumption, lack of exercise, vitamin D deficiency, poor nutrition, and consumption of soft drinks.
• Diagnosis Osteoporosis is diagnosed by measuring a patient’s bone density and comparing it with the normal level of peak bone density of a young adult reference population of the same sex as the patient.
• Treatment Osteoporosis is often treated with medications such as bisphosphonates that may slow or even reverse bone loss. The only way to prevent osteoporosis is to eliminate risk factors that can be controlled through changes of behavior, such as undertaking weight-bearing exercise if you have been sedentary.
• Why is it important to build sufficient bone mass in your young adult years? Answers may vary. Sample answer:  Osteoporosis results from the loss of bone mass after the peak years of the 30s. If sufficient bone mass is not developed before and during that time, your peak bone mass will start out lower and you will be at greater risk for osteoporosis as bone mass declines in your later years.
• Explain the difference in cause between rheumatoid arthritis and osteoarthritis. Rheumatoid arthritis is an autoimmune disease that arises when the body’s immune system attacks the joints. Osteoarthritis, on the other hand, is caused by mechanical stress on the joints with insufficient repair of cartilage.
• Debunk the myth: Osteoarthritis is caused by physical activity, so people who are equally active are equally susceptible to it.  False, because OA is generally caused by insufficient repair of cartilage, which does not happen equally in the general population, therefore exercise would not necessarily have the same effect on joints in different individuals.
• Explain how we know that estrogen generally promotes production of new bone. Estrogen protects the adult skeleton against bone loss by slowing the rate of bone remodeling and by maintaining a focal balance between bone formation and resorption.

13.8 Case Study Conclusion and Chapter 13 Summary: Review Questions and Answers

• Why does the rib cage need to be flexible? Why can it be flexible?   Answers may vary. Sample answer:  The rib cage needs to be flexible because it needs to expand and contract with breathing movements. It is able to be flexible because true ribs are attached to the sternum by cartilage, which creates partly movable joints. Also, false ribs and floating ribs are attached by cartilage to true ribs or to muscles in the abdominal wall, respectively. This also allows them the flexibility to move as the person breathes.
• In general, what do “girdles” in the skeletal system do?   Answers may vary. Sample answer:  The shoulder and pelvic girdles both function to connect the limbs to the axial skeleton.
• Would swimming be more effective as an exercise for preventing osteoporosis or as a treatment for osteoarthritis? Explain your answer.   Answers may vary. Sample answer:  Swimming is likely more of an effective treatment for osteoarthritis than a way to prevent osteoporosis, because it is not a weight-bearing exercise. That means it is gentle on the joints, which is needed when a person has osteoarthritis because they have lost cartilage that cushions the joints. To prevent osteoporosis, weight-bearing exercise such as running or weight training is needed because it causes stress on the bones which stimulates bone building. This helps prevent the loss of bone mass that occurs in osteoporosis.
• Explain why some of the vertebrae become misshapen in the condition called dowager’s hump (or kyphosis).   Answers may vary. Sample answer:  A dowager’s hump is typically caused by osteoporosis, which is a disorder involving the loss of bone mass. This causes compression fractures in the thoracic vertebrae, because the bones are brittle and fracture easily even without a major injury. These compression fractures result in the misshapen vertebrae seen in a dowager’s hump.
• Explain why osteoarthritis often involves inflammation in the joints.  Osteoarthritis often involves inflammation in the joints because the cartilage in the joints breaks down. As cells lining the joint attempt to remove these breakdown products, inflammation results.
• Osteoporosis can involve excess bone resorption, as well as insufficient production of new bone tissue. What are the two main bone cell types that carry out these processes, respectively?  Osteoclasts carry out bone resorption and osteoblasts produce new bone tissue.
• Describe two roles that calcium in bones play in the body.   Answers may vary. Sample answer:  Calcium helps make bones hard in order to support and protect the body. Also, bones serve as a storage site for calcium, so that calcium can be released from bones when the level of calcium in the blood is too low.

Human Biology Copyright © 2020 by Christine Miller is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

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Skeletal System Questions & Answers

Hi Everyone!! This article will share Skeletal System Questions & Answers. In my previous post, I have shared the objective type questions and answers of Skeletal System so, make sure to check this post as well.

Skeletal System Questions & Answers

Question 1: what is a skeletal system state its functions..

Answer: A system in which framework of bones provides structure and support for a body is a skeletal system. Functions of the Skeletal System are:

• Gives basic shape and structure to the body.
• Protects internal organs.
• Enable us to perform various bodily functions.
• Blood cells are produced within the red bone marrow present in some bones.
• Minerals such as calcium and phosphorous are stored in some bones.

Question 2: Define:

(a) joint answer: a joint is where two or more bones meet. it enables the movement of bones and provides support to the body., (b) skeleton answer: the skeletal system is made of bones and is called the skeleton., question 3: give reasons:, (a) regular exercise keeps bones and muscles strong. answer: bones and muscles becomes strong when muscles push against bones during physical activity. thus, regular exercise keeps muscles and bones strong., (b) the skeleton of a child has more bones than the skeleton of an adult. answer: the skeleton of a child has 270 bone and as the child grows some bones fuses together to form larger bone and therefore an adult has 206 bones., (c) muscles and bones are different but are closely linked. answer: muscles are softer than bones. but some muscles are attached closely to the bones which are also known as skeletal muscles. these muscles help in proper functioning of the bone. the muscles and the skeletal system together form the musculoskeletal system of the body., (d) the bones of the skull are immovable except lower jaw. answer: all the other bones in the skull are firmly attached to one another by sutures. sutures are rigid immovable connections holding bones tightly to one another forming cranium that protects the brain and facial bones. lower jaw is the only movable joint as it forms the lower part of mouth whose function is also to chew food., (e) babies are advised to drink milk, eat cheese and spinach. answer: milk cheese and spinach contain nutrients such as proteins, fats, vitamins and minerals in a large amount, which help in the growth and development of bones. these nutrients also help to make bones stronger., question 4: observe the given picture and answer the questions:, (a) identify the structure shown above..

Answer: Backbone / vertebral column/spine.

(b) How many bones are present in the above structure?

Answer: 33 bones are present.

(c) Which organ does the above structure protect?

Answer: Spinal cord

Question 5: Differentiate between Pelvic girdle and Pectoral girdle.

Question 6: Give one example of the following:

(a) a movable joint.

Answer: Knee joint/ shoulder joint/ elbow joint

(b) Immovable joints

Answer: Joints of the skull

Question 7: How are bones classified on the basis of shape and size?

Answer: Based on shape and size, bones are classified into four types:

Question 8: Name the parts of skeleton and its functions.

Answer: Our skeleton is made up of five main parts: 1. The skull

• It is made up of 22 bones.
• Only the lower jaw is immovable.
• Protects the brain enclosed within.
• Thin flat and curved bones in the chest region forming a cage.
• It is made up of 12 pairs of bones called ribs.
• First 10 pairs of ribs are attached to a long bone called sternum or breastbone in front and to the backbone behind.
• Last two pairs of ribs are only attached to the backbone behind and are called floating ribs.
• It protects internal organs such as heart and lungs from injuries and shock.

3. Backbone or vertebral column

• The backbone is made up of 33 vertebrae.
• It protects the spinal cord
• Helps us to stand upright and maintain our balance.

4. Limbs Humans have – i. Forelimbs (upperlimbs or arms): Humerus is a long bone present in the upper arm. ii. Hind limbs (lower limbs or legs): Femur present in the thigh is the longest bone in the human body. Limbs enable us to perform various activities such as running, walking, swimming, jumping, drawing, writing etc.

5. Girdles The skeleton has two girdles – i. Pectoral girdle or the shoulder girdle is formed by the joining of bones in the shoulder region. It attaches the upper limb to the remaining parts of the body skeleton. ii. Pelvic girdle is formed by joining of the bones in hip region. It attaches the lower limbs to the remaining parts of the body skeleton.

Question 9: Differentiate between cartilage and bones.

Question 10: Differentiate between Ligaments and Tendons?

So, these were Skeletal System Questions & Answers.

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