The Skeletal System

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Skeletal system…

• Is made up of hard tissues like bone and cartilages. • Gives form and shape to animal body • The skeleton of a living animal is made up living

structures of bones. • The bones have blood vessels, lymphatic vessels

and nerves. • They are subject to disease, repair themselves and

adjust to changes during stress.

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Functions of Bones

1.Protection: of some vital organs from the external damages -important function

CNS is protected by the skull and vertebral column; the heart and lungs by rib cage; and pelvis protects the internal parts of urogenital system.

2.Rigidity and form to the body: animals without a skeleton of some type have little or no regular form. Gives a basis for the external structure and appearance of most animals.

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3.Act as lever: in the vertebrates, locomotion, defense, offense, grasping, and other activities .Almost without exception, these levers are made of bone and are integral parts of skeleton.

4.Storage of minerals: -dynamic storage area for minerals, particularly calcium and phosphorous.

5.Site for blood formation: blood formation is not strictly a function of bone proper, but of the marrow found within the marrow cavity of long bones and within the spongy substance of all young bones.

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Classification of bones

Any bone may be classified into one of the following groups:  

I. Long bones: • relatively cylindrical in shape with two extremities

called epiphyses.• Metaphysis between each epiphysis and the diaphysis.• A long bone grows in length only at the epiphyseal

cartilage which is located within the metaphysis. •  

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Long bone

Epiphysis

Epiphysis

Diaphysis

Metaphysis

Metaphysis

MedullaryCavity

• Examples of long bones - pectoral limb, humerus, radius, ulna, metacarpals, phalanges; pelvic limb, femur, fibula, tibia, metatarsals and phalanges.

2. Short bones

• Somewhat cuboid in shape i.e approximately equal in all dimensions.

• No marrow cavity. • Found in complex joints such as the carpus (knee) and

tarsus (hock).• Example of short bones: Patella.

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• Function: - for variety of movement - absorption of shock

3.Flat bones• relatively thin and expanded in two dimensions. • Consist of two plats of compact substance, lamina

externa and lamina interna, • Separated by diploe. • Example -frontal base of skull, scapula and pelvic

bones• Functions: - protects vital organs such as brain, the

heart and lungs.• - many provide large areas for muscle attachment.

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4. Sesamoid bones: they are developed along the course of tendons. Example: Patella (knee cap) is the largest sesamoid in the body.

Functions: -reduces friction or change the course of tendons. - may change the angle of the pull of muscles and

this give a greater mechanical advantage. 5. Pneumatic bones: they contain air spaces or sinuses that

communicate with the exterior. Example: long bones of bird, frontal bones and maxillary bones of the skull.

 

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6. Irregular bones: are unpaired bones located on the median plane and include

the vertebrae and some of the unpaired bones of the skull.Functions: - protection, support and muscle attachment.

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Bored????

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TWO PARTS OF SKELETAL SYSTEM

For better understanding the skeletal system can be divided into two part:

1. Axial skeleton 2. Appendicular skeleton. 

1.AXIAL SKELETON is made up of skull, and vertebral column sternum

and ribs. The table below indicates the bones of the axial skeleton by regions.

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C TL

S

Cd

RibsStermun

Skull

Axial Skeleton of cattle

Skull

• Forms basis for head

• Made of - cranial bones

- Facial bones

• Protects brain

• Support sense organs

• Digestive & respiratory system startsAnato/Skelsyst/pj 15

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Cranial bones

Facial Bones

Skull of cattle

Diploe

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Bored again???

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Vertebral column

• Made of unpaired irregular bones

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Divided into:• Cervical vertebrae (C)• Thoracic vertebrae (T)• Lumbar vertebrae (L)• Sacral vertebrae (S)• Coccygeal vertebrae (Cd)

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Vertebral formulaCow: C7 T13 L6 S5 cd18-20

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Sternum

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Ribs

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2.APPENDICULAR SKELETON:

Is made of

1. Pectoral limb or fore limb

2. Pelvic limb or hind limb

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Still bored???

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Pectoral limb

Scapula

Humerus

Ulna

Radius

CarpusMetacarpus

Digits

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Pelvic Limb

Pelvis

Femur

Tibia & fibula

Tarsus

Metatarsus

digits

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Avian skeleton

skull

Neck

Digits

Radius & Ulna

Humerus

Pelvic bone Femur

TibiaSternumribs

Metacarpus

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Skeleton of goat

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Skeleton of pig