3.5. Responses in the Human3.5.3 Musculoskeletal system

At the end of this section you should be able to .. Y NDescribe the functions of the skeleton:Explain the division of the skeleton into two parts – the axial and appendicular.Axial: Know the component parts of the axial skeletonDescribe the position and function of discs in relation to vertebrae.Know the groups of vertebraeAppendicular: Describe the components of the appendicular skeletonDescribe the parts of the pectoral girdle and the attached appendagesDescribe the parts of the Pelvic girdle and attached appendages;Long bone: Describe the macroscopic anatomy of a long bone:Describe the structure and function of Cartilage:Describe the structure and function of compact bone:Describe the structure and function of Spongy boneJoints: Explain the classification, location and function of jointsExplain the role of cartilage and ligaments in joints.Describe the role of tendonsDescribe the general relation of muscles to the skeleton (antagonistic muscle pairs) Contemporary IssueDescribe one example of a musculoskeletal disorder from the following: arthritis and osteoporosis;Give one possible cause, prevention and treatment

Key WordsVertebrae, thoracaic, axial, appendicular, pectoral, pelvic, osteocytes, osteoporosis

Musculoskeletal system (Summary)

The skeleton is divided into two parts – the axial skeleton and appendicular skeleton.

Axial skeleton:

skull, (details of the

skull not required)

vertebrae: Cervical

(17), Thoracic (12),

Lumbar (5), and

coccyx (4). Discs of

cartilage found

between each

vertebra

ribs: 12 pairs

sternum (breast bone).

Appendicular skeleton:

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3.5. Responses in the Human3.5.3 Musculoskeletal system

The appendicular skeleton consists of the Pectoral and pelvic girdles and their attached

limbs.

Pectoral girdle:

Clavicle (collar bone)

Scapula (shoulder blade)

Attached appendages (limbs): humerous, radius, ulna, carpal, metacarpal, digits

(fingers) containing phalanges.

Pelvic girdle;

Innominate bones (hip bones) attached to the sacrum surrounding a cavity.

Attached appendages: Femur, patella, tibia, fibula, tarsals, metatarsals, digits (toes)

containing phalanges.

Bones

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Functions of the skeleton: Framework of the body Protection of internal organs Assists in movement

3.5. Responses in the Human3.5.3 Musculoskeletal system

Structure of long bone

A long bone contains a hollow centre region called the medullary cavity, containing yellow bone

marrow that stores fat.

Cartilage covers the tips of bones in joints, reducing friction, and acting as a shock absorber.

It is composed of protein fibres and is flexible

Compact bone consists of living cells (osteocytes) Consists of living cells which are embedded in a

matrix of calcium salts and a protein called collagen. It is supplied by blood vessels and nerve fibres.

It is very dense and is found mainly at the outer edge of bones. Gives strength and rigidty

Spongy bone consists of a network of thin, bony columns and plates, along with spaces filled with

marrow [red or yellow]. It gives moderate strength to bones but makes them lighter. These spaces

are filled with red bone marrow that produces blood cells and yellow bone marrow that contains fat-

storage tissue.

JOINTS

Joints are found where bone meets bone.

Structure of a synovial joint:

Synovial joints e.g. Hinge e.g. knee or elbow, Ball and socket e.g. hip or shoulder

Tendons and ligaments

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Synovial fluid: Lubricates the joint

Cartilage: Prevents wear and tear of bones

Cartilage prevents the wear and tear of bone

Ligaments join bone to bone. Elastic to allow movement Tough

Classification Location Function

Imovable Between skull bones

No movementProtection

Slightly movable

Between vertebraeBetween hip bones

Allow limited movementFlexibility

Synovial (free moving)

Knee, elbow, hip, shoulder

Allows free movement

3.5. Responses in the Human3.5.3 Musculoskeletal system

Antagonistic Muscles

Two muscles which cause opposite effects are known as antagonistic pairs of muscles. Muscles can only contract and relax and thus need to work in pairs.

Example:In the human arm:

One muscle (Biceps) bends the joint and brings the limb towards the body, The other muscle (Triceps) straightens the joint and

extends the limb

Contemporary Issue

Osteoporosis:Osteoporosis is a disease of the

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What is Osteoporosis

Osteoporosis means ‘porous bones’ and results in a loss of bone density. Osteoporosis usually affects the whole skeleton, causing bones to be more easily broken, particularly in the hip, spine and wrist . Osteoporosis causes pain, disability, curvature of the spine and loss of height. Osteoporotic bones may appear normal on the outside, inside they have large gaps in structure which means they can break very easily.

compact bone surrounds a large central cavity called the medullary cavity.

Spongy bone is usually found at the ends of long bones. It consists of an inner mesh with large spaces filled with red bone marrow, protein (collagen) and calcium salts. This inner mesh forms a framework like a honeycomb.

This structure of compact and spongy bone maximises strength while minimising weight.

Osteoporosis occurs when spaces in the spongy bone becomes bigger, making it fragile and easy to break.

called OSTEOBLASTS.

Bone also changes in structure and undergoes mineralisation (becomes impregnated with calcium).

By the age of about 30, maximum bone density is reached. From then on worn-out old bone is broken down by cells called OSTEOCLASTS.

Osteoporosis is caused when more bone is lost than is made and results in a loss of bone density.

OS T EOPOR

RISK FACTORSGender, Family history, Nutrition, Physical inactivity,

Smoking, Excess alcohol, Age

3.5. Responses in the Human3.5.3 Musculoskeletal system

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compact bone surrounds a large central cavity called the medullary cavity.

Spongy bone is usually found at the ends of long bones. It consists of an inner mesh with large spaces filled with red bone marrow, protein (collagen) and calcium salts. This inner mesh forms a framework like a honeycomb.

This structure of compact and spongy bone maximises strength while minimising weight.

Osteoporosis occurs when spaces in the spongy bone becomes bigger, making it fragile and easy to break.

called OSTEOBLASTS.

Bone also changes in structure and undergoes mineralisation (becomes impregnated with calcium).

By the age of about 30, maximum bone density is reached. From then on worn-out old bone is broken down by cells called OSTEOCLASTS.

Osteoporosis is caused when more bone is lost than is made and results in a loss of bone density.

Normal honeycomb structure of spongy bone

Osteoporotic spongy bone

PREVENTION

Eat a diet rich in Calcium

Eat a diet rich in Vitamin D

Engage in weight bearing physical activity e.g. walking, cycling, jogging, football, hockey

Do not smoke

Moderate alcohol intake

Osteoporosis affects both women and men and can occur at any age but most typically affects women after the menopause.

The female hormone oestrogen has a protective effect on bones and inhibits the breakdown of bone tissue. Oestrogen deficiency is the main reason for bone loss in post menopausal women.

TREATMEMNT

TEST FOR OSTEOPOROSISA bone density scan called a

DEXA SCAN

Calcium and vitamin D supplements

Biophosphonates – non hormonal drugs

Hormone replacement therapy – post menopausal women

Exercise