1. The
SKELETAL
SYSTEM

2. THE SKELETAL SYSTEM: OVERVIEW
I. INTRODUCTION
The organs of the skeletal system include the bones and the structures that connect bones to other structures, including ligaments, tendons, and cartilages.
The adult skeleton is composed of 206 separate bones.

3. Division of skeleton Axial skeleton Includes the bones of:
skull, vertebral column, and rib cage.
These bones are involved in protection, support, and carrying other body parts.
Appendicular skeleton
Bones of upper & lower limbs and the girdles (shoulder bones and hip bones) that attach them to the axial skeleton.
Involved in locomotion and manipulation of the environment.
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4. AXIAL SKELETON
Appendicular
SKELETON
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5. AXIAL SKELETON 1) Skull: 28 irregular shaped bones from the skull.
The skull consists of two major division:
Cranium is formed by eight bones.
Face is formed by fourteen bones.

6. AXIAL SKELETON 2) VERTEBRAL COLUMN Divided into 5 main regions
Cervical spine (7)
Thoracic spine (12)
Lumbar spine (5)
Sacrum (5)
Coccyx (4)
The 5 sacrum vertebrae and 4 coccyx vertebrae are fused to form one solid bone.

7. Cervical, Thoracic, Lumbar, Sacrum and Coccyx

8. AXIAL SKELETON THORAX 12 pairs of ribs Joined to thoracic vertebrae
Top 10 ribs joined to sternum
Remaining two have “free” ends – ‘floating’

9. APPENDICULAR SKELETON
Forms mainly the extremities of the body and their connections to the axial skeleton
Consists of
- limbs (arms & legs)
- shoulder and pelvic girdles

10. Bone Classification 4 types of bones: Femur  Long Bones Short Bones
Much longer than they are wide.
All bones of the limbs except for the patella (kneecap), and the bones of the wrist and ankle.
Consists of a shaft plus 2 expanded ends.
Short Bones
Roughly cube shaped.
Bones of the wrist and the ankle.
Carpal Bones
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11. Bone Classification Types of bones: Flat Bones Irregular Bones
Thin, flattened, and usually a bit curved.
Scapulae, sternum, (shoulder blades), ribs and most bones of the skull.
Irregular Bones
Have weird shapes that fit none of the 3 previous classes.
Vertebrae, hip bones, 2 skull bones ( sphenoid and the ethmoid bones).
Sternum
Sphenoid Bone

12. Parts of long bone
1) diaphysis: main shaft like structure, its hollow cylindrical shape, its functions of providing strong support bone.
2) epiphysis: both end of long bone, epiphysis have a bulbous shape that provide generous space near joint.
For muscle attachment and give stability of joint.

13. Parts of long bone
3) articular cartilage thin layer of hyaline cartilage that covers joint surface.
4) Periosteum: dense white fibrous membrane that cover bone except at joint surface and anchoring bone to muscles.
5) Marrow cavity: a tubelike hollow space in the diaphysis of long bone.
6) endosteum: a thin epithelial membrane that line the medullry cavity.

14. Long Bone Structure
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15. Composition of bone matrix
Inorganic salts: the hardness of bone result from the deposition of high specialized chemical crystal of calcium and phosphorous called hydroxyapatite, the process called calcification in addition to mg, Na, sulphate and fluoride.
Organic substance: collagenous fiber and mixture protein and poly saccarids called ground substance, provide support and adhesion between cellular and fiberous.
Chondroitin and glucosamine are required for repair and maintenance of bone and cartilage.

16. Composition of bone matrix
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17. Types of bone cells 1. Osteoblasts
Bone-forming cells found in all bone surfaces Bone-building cells.
Synthesize and secrete collagen fibers and other organic components of bone matrix.
serve as a framework for the deposition of calcium and phosphate calcification
The blue arrows indicate the osteoblasts. The yellow arrows indicate the bone matrix they’ve just secreted.

18. Types of bone cells 2. Osteoclasts Giant multinucleate cells
Responsible for the active erosion of bone minerals
Contain large numbers of mitochondria and lysosomes

19. Types of bone cells
3. Osteocytes—mature, nondividing osteoblast surrounded by matrix, lying within lacunae
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21. Bone Marrow
Specialized type of soft, diffuse connective tissue; called myeloid tissue
Site for the production of blood cells
Found in medullary cavities of long bones and in the spaces of spongy bone

22. Microscopic Structure of Compact Bone
Contains many cylinder-shaped structural units called osteons, or Haversian systems
Four types of structures make up each osteon:
Lamella—concentric, cylinder-shaped layers of calcified matrix
Lacunae—small spaces containing tissue fluid in which bone cells are located between hard layers of the lamella

23. Microscopic Structure of Compact Bone
Canaliculi—ultrasmall canals radiating in all directions from the lacunae and connecting them to each other and to the Haversian canal
Haversian canal—extends lengthwise through the center of each osteon and contains blood vessels and lymphatic vessels

24. Microscopic Structure of Compact Bone
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25. Bone Marrow
Two types of marrow are present during a person’s lifetime:
Red marrow
Found in virtually all bones in an infant’s or child’s body
Functions to produce red blood cells
Yellow marrow
As an individual ages, red marrow is replaced by yellow marrow
Marrow cells become saturated with fat and are no longer active in blood cell production

26. Bone Marrow
The main bones in an adult that still contain red marrow include the ribs, bodies of the vertebrae, the humerus, the pelvis, and the femur
Yellow marrow can alter to red marrow during times of decreased blood supply, such as with anemia, exposure to radiation, and certain diseases

27. Functions of Bone
Support—bones form the framework of the body and contribute to the shape, alignment, and positioning of the body parts
Protection—bony “boxes” protect the delicate structures they enclose
Movement—bones with their joints constitute levers that move as muscles contract
Mineral storage—bones are the major reservoir for calcium, phosphorus, and other minerals
Hematopoiesis—blood cell formation is carried out by myeloid tissue

28. Regulation of Blood Calcium Levels
Skeletal system (cont.)
Homeostasis of calcium ion concentration essential for the following:
Bone formation, remodeling, and repair
Blood clotting
Transmission of nerve impulses
Maintenance of skeletal and cardiac muscle contraction

29. Regulation of Blood Calcium Levels
Mechanisms of calcium homeostasis
Parathyroid hormone
Primary regulator of calcium homeostasis
Stimulates osteoclasts to initiate breakdown of bone matrix and increase blood calcium levels
Increases renal absorption of calcium from urine
Stimulates vitamin D synthesis

30. Mechanisms of calcium homeostasis (cont.)
Calcitonin
Protein hormone produced in the thyroid gland
Produced in response to high blood calcium levels
Stimulates bone deposition by osteoblasts
Inhibits osteoclast activity
Far less important in homeostasis of blood calcium levels than parathyroid hormone

31. Fracture Types Open (compound)  bone ends penetrate the skin.
Closed (simple)  bone ends don’t penetrate the skin.
Spiral  ragged break caused by excessive twisting forces. Sports injury/Injury of abuse
Greenstick bone breaks incompletely. One side bent, one side broken. Common in children whose bone contains more collagen and are less mineralized

33. Clinical Conditions Osteomalacia
Literally “soft bones.”
Includes many disorders in which osteoid is produced but inadequately mineralized.
Causes can include insufficient dietary calcium
Insufficient vitamin D fortification or insufficient exposure to sun light.
Rickets
Children's form of osteomalacia
More detrimental due to the fact that their bones are still growing.
Signs include bowed legs, and deformities of the pelvis, ribs, and skull.
What about the above x-ray is indicative of rickets?

34. Clinical Conditions Osteomyelitis
Inflammation of bone and bone marrow caused by pus-forming bacteria that enter the body via a wound (e.g., compound fracture) or migrate from a nearby infection.
Fatal before the advent of antibiotics.

35. Clinical Conditions Osteoporosis
Osteoporosis is a disease that thins and weakens the bones to the point that they become fragile and break easily. Women and men with osteoporosis most often break bones in the hip, spine, and wrist, but any bone can be affected. You can't "catch" osteoporosis or give it to someone else.

36. Any questions ???
The end