Unit 3B

Human Form & Function

Body systems

The skeleton

Study Guide

Read:• Our Human Species (3rd edtn)

Chapter 4, sections 1-8, 13-14Complete:• Human Biological Science Workbook

Topic 13 – The Skeleton

Skeletal system• The skeletal system consists of the bones,

joints, ligaments and cartilages in the body.

• The functions of the skeletal system are to: – protect and support the internal organs, – provide anchor points for the muscles to

allow movement,– produce blood cells.

The microscopic structure of bone

Prof Alan Boyde, Wellcome Images

Bone• Bone is classified as a connective tissue.• It has a brittle, calcified matrix with many

collagen fibres, giving bones a degree of pliability.

• Several types of cells occur in bone. These include osteoblasts, which are young, bone-forming cells, and osteocytes, which are mature cells contained in cavities (lacunae).

• Bone has a rich blood supply.

There are two types of bone – compact bone, which is very hard and dense, and spongy bone, which is porous, consisting of a network of small bony plates.

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Compact bone

Spongy bone

Compact bone• Compact bone consists of Haversian

systems. A Haversian system comprises circular layers of bone (lamellae) surrounding a central Haversian canal, which carries blood and lymph vessels.

Haversian systems

M I Walker, Wellcome Images

Haversian systemHaversian canal

Concentric lamellae

Haversian systems

Central canal

Lacunae housing mature osteocytes

Wellcome Photo Library

Concentric lamellae

The skeleton

Bone classificationBones can be classified according to their shape and their structure.Classification by shape• Long bone – e.g. Thigh bone (femur)• Short bone – e.g. wrist bones (carpals)• Flat bone – e.g. shoulder blade (scapula)• Irregular bone – e.g. vertebrae• Sesamoid bones develop in tendons – e.g. kneecap (patella)

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Long bone

Short bones

Irregular bone

Flat bones

Bones classified by structure

Epiphysis

Diaphysis

Spongy or cancellous

bone

Compact or dense

boneM I Walker, Wellcome Images

D Gregory & D Marsgall, Wellcome Images

The Miles Kelly Art library, Wellcome Images

Structure of a long bone

Epiphysis

Diaphysis

Spongy or cancellous bone

Compact or dense bone

Articulating cartilageGrowth cartilage

Marrow cavity Periosteum

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Axial & appendicular skeleton

Axial skeleton– Skull– Vertebral column

(backbone)– Ribcage

Appendicular skeleton– Pectoral girdle– Upper limbs– Pelvic girdle– Lower limbs

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Vertebral column

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7 cervicalvertebrae

12 thoracicvertebrae

5 lumbarvertebrae

5 fused sacral vertebrae

Coccyx3-5 vertebrae

Cervical vertebrae

Thoracic vertebrae

Lumbar vertebrae

Structure of a vertebra

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Body

Transverse process

Spinous process

Articulating surface

Vertebral foramen

Intervertebral disc

Ribcage

Gray’s Anatomy

Anterior Posterior

Sternum

Costal cartilage

Pelvic girdle

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Pectoral girdle

Clavicle

Scapula

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Joints

Joint classification• Joints can be classified by their structure and the

amount of movement they allow.

Structure Joint cavity MovementFibrous None NoneCartilaginous None None or slightSynovial Present Freely movable

Types of joints

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Immovable fibrous joint

Slightly movable cartilaginous joint

Movable synovial joint

The structure of a synovial joint

Wellcome Photo Library

Articulating cartilage

Joint cavity

Bursa

Synovial membrane

Fibrous capsule

Can you name these ligaments of the knee joint?

Synovial joints

Synovial joints have a joint cavity and are classified according to the type of movement they allow.

Flexion Extension

Rotation

Rotation

AdductionAdduction

Abduction

Hinge joint

Ball & socket joint

Pivot joint

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