3.5.3 Responses in the Human
[C] Musculoskeletal System
Objectives – What you will need to know from this section
 Describe the structure & function of the musculoskeletal system.
 Name components of axial skeleton -- skull / vertebra / ribs / sternum
 State the position & function of discs in vertebrae.
 State the components of the appendicular skeleton – pectoral / pelvic girdle & limbs
 Outline the macroscopic anatomy of a long bone including: medullary cavity, compact bone, spongy bone and cartilage.

 State the function of the following: cartilage / compact bone / spongy bone -- including red & yellow marrows.
 Classify, locate & state the function of joint types --
Immovable, slightly free-moving, and synovial.
 Outline disorders from: arthritis/osteoporosis, include the
Causes / Prevention and Treatment
 Outline the role of cartilage & ligaments.
 Outline the role of tendons.
 Outline the general relation of muscle to skeleton.
 State an example of an antagonistic pair of muscles.

Response in the Human
Musculoskeletal System
Skeletons provide
 support ,
 protection of internal organs
 and a rigid frame for movement .

 The human skeleton has 206 bones, which can be divided into two parts: axial and appendicular.
 Axial skeleton – skull, ribs
(12 pairs), sternum
(breastbone) & vertebrae
(backbone).
 Appendicular skeleton – pectoral and pelvic girdles, and their attached limbs
(arms and legs)

Axial skeleton
 skull, ribs (12 pairs),
 sternum (breastbone)
 vertebrae (backbone).
 The spine (vertebral column, backbone) is a series of 33 bones
(vertebrae).

OUR SPINE -- VERTEBRAE

LEARNING CHECK
• Give 4 functions of your skeleton.
• Name the 2 main parts our skeleton is divided into.
• The axial skeleton is composed of which bones?
• The appendicular skeleton is composed of which bones?
• What is a vertebra?
• Name the sections of your spine.

Appendicular skeleton 1
 pectoral girdle
 attached limb (arm)

Appendicular skeleton 2
 pelvic girdle
 attached limb (leg)

Appendicular skeleton

LEARNING CHECK
• What is your pectoral girdle?
• What is your pelvic girdle?
• What is the difference between the metacarpals and the carpals?
• What is the difference between the metatarsals and the tarsals?
• Where are these bones :
Ulna / humerus / femur / patella /clavicle ?

BONE STRUCTURE
 A long bone contains a hollow centre region called the medullary cavity, containing yellow bone marrow that stores fat.
 The periosteum is a tough fibrous layer surrounding each bone.
 Cartilage covers the tips of bones in joints, reducing friction, and acting as a shock absorber.

 Compact bone consists of living cells (osteocytes) embedded in a matrix of calcium salts and a protein called collagen.
 It is very dense and is found mainly at the outer edge of bones.

 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 .
 Red marrow makes blood cells
(red, white and platelets).

LEARNING CHECK
• What is the hollow centre of a long bone called?
• Distinguish between compact and spongy bone
• Distinguish between red and yellow marrow
• What is an osteocyte?
• Why are the tips of bones covered in cartilage?

JOINTS
 A joint is where the two bones meet.
 Ligaments hold the bones together at joints.
 There are three main types of joint : immovable, partially movable and movable.

TYPES OF JOINT

 Immovable joint — bones are fused, e.g. skull, pelvis.
TYPES OF JOINT
 Partially movable joint — bones slide over each other, e.g. wrist, ankle, spine.

TYPES OF JOINT
 Free moving ( synovial ) joint —Ball-and-socket and Hinge.
 Synovial fluid lubricates a joint and acts as a cushion.
 Ball-and-socket joint
– allows movement in most directions, e.g. hip, shoulder.
 Hinge joint
– allows movement in one plane only, e.g. elbow, knee, finger, toe.

Ball-and-socket joint – Shoulder.

Hinge joint – Knee.

Bones of the Hand and Wrist.

LEARNING CHECK
• What is a joint?
• What holds your bones together?
• Name the 3 main types of joint.
• Give an example of a fused joint.
• Give an example of a partially movable joint
• What is a synovial joint?
• Distinguish between a ball-and-socket joint and a hinge joint.

MUSCLES
 Muscles pull on bones and so provide movement .
 Muscles are attached to a bone by tendons .
 Muscles can only pull
[when they contract ]
 they cannot push.

 Muscles can only pull
[when they contract ], they cannot push.
 For this reason, they are always arranged in pairs (called antagonistic pairs ) that operate in different directions,
 e.g the biceps and triceps, which control arm movement.

humerus biceps ulna radius

humerus biceps ulna radius

triceps relaxes bone pulled upward

biceps humerus radius ulna triceps

biceps relaxes bone pulled downward

LEARNING CHECK
• Explain the terms “contract” and “relax” as applied to muscles.
• Why are muscles arranged in antagonistic pairs?
• Name the pair of muscles that move the lower arm.
• Distinguish between tendon and ligament

Arthritis – A Bone Disorder
 Arthritis is a painful disorder where there is inflammation in one or more joints, resulting in swelling, warmth, pain and restricted movement.
Possible Causes
 Many diseases can be a cause of arthritis, e.g. gout, TB and infections of the synovial membranes
 Cartilage can degenerate through wear and tear , and old age.

Prevention
 could be through good diet ,
 care in selection of footwear ,
 not putting the bones and joints under excessive stress during exercise .
Treatment
 can be with aspirin to reduce the swelling and pain,
 in severe cases, replacement with an artificial joint [e.g. the head of the femur in a hip joint].

LEARNING CHECK
• Arthritis is a bone disorder.
• What are its symptoms?
• What are its possible causes?
• What treatment is used for it?
• What might be done to lessen the chances of it?