1. Anatomy and Physiology I
Unit 7: The Skeletal System
Physiology of the Skeletal System

2. Skeletal System
• Bones are made of several
tissues
• Primarily made of collagen and
hydroxyapatite -
Ca10(PO4)6(OH)2
• About 206 bones in the human
body

3. Functions of Skeletal System
• SUPPORT: Hard framework that supports and anchors
the soft organs of the body.
• PROTECTION: Surrounds organs such as the brain and
spinal cord.
• MOVEMENT: Allows for muscle attachment therefore
the bones are used as levers.
• STORAGE: Minerals and lipids are stored within bone
material.
• BLOOD CELL FORMATION: The bone marrow is
responsible for blood cell production.

4. Parts of the Skeletal System
• Axial skeleton
– Skull and bones that support it
– Includes vertebra and ribs
– 80 bones
• Appendicular skeleton
– Limbs
– 126 bones

5. Features of a Long Bone:
Epiphysis: Ends of the
bone.
Diaphysis: The shaft of
the bone which surrounds
the medullary cavity.
Articular Cartilage:
Cushions the ends of the
bones and allows for
smooth movement.
Epiphyseal Plate:
Areas made of cartilage
allowing for the growth of
the bone.

6. Joints
• Where bone meets bone
• Ligament – holds bone to bone
• Types of joints:
– Immovable - skull
– Ball-and-socket - shoulder
– Hinge - knee
– Pivot – forearm
– Gliding - vertebrae

7. Joints
• Cartilage covers ends of movable bones
– Reduces friction
• Lubricated by fluid from capillaries

8. Cartilage

9. Bone Structure
• Periosteum – hard outer covering
– Cells for growth and repair
• Compact bone – hard strong layer
– Bone cells, blood vessels, protein with Ca and P
• Spongy bone – at ends of long bones
– Has small open spaces to lighten weight
• Marrow cavity – hollow in middle of long bones

10. Bone Marrow
• Red marrow – produces blood cells and
clotting factors
– Found in humerus, femur, sternum, ribs,
vertebrae, pelvis
– Produces RBC 2 million per second
• Yellow marrow – stores fat
– Found in many bones

11. Bone Structure

12. Haversian System
• Structure of compact bone
• Rings of bone tissue with blood vessels
and nerves in the center

13. Haversian System

14. Bone Development
• Initial skeleton of cartilage in infants
• Replaced with bone by osteoblasts
• More than 300 bones at birth – fuse to 206
• Always growing and breaking down
– Osteoblasts – form new bone cells
– Osteoclasts – break bone cells down
– Osteocytes – mature bone cells

15. Broken Bones
• Fracture is a break of the bone
• Simple or Complex fracture
• Regrowth of bone:
– Spongy bone forms in first few days
– Blood vessels regrow and spongy bone hardens
– Full healing takes 1-2 months

16. Homeostatic Imbalances
Rickets
•Disease of children due to a lack of vitamin D.
•Calcium is not deposited in bones.
•Bones become soft.
•Bowing of the bones, and other deformities occur.

17. Homeostatic Imbalances
Osteomalacia
•“Rickets” of adults.
•Due to a lack of vitamin D.
•Calcium is not deposited in the bones.
•Bones become brittle.

18. Homeostatic Imbalances
Osteoporosis
•Bone reabsorption is greater than bone deposition.
•Due to any of the following:
•Lack of estrogen in women.
•Lack of exercise to stress the bones.
•Inadequate intake of calcium and phosphorus.
•Abnormalities of vitamin D metabolism.
•Loss of muscle mass.

19. Age Related Dysfunctions
Arthritis:
Osteoarthritis- 90% of pop. By age 40
chronic inflammation of articular cartilage
can be normal age-dependent change
can also be pathology due to ?
Age-related changes
decrease blood supply
trauma

20. Osteoarthritis

21. Osteoporosis
Decline in Bone Density
Bone Resorption > Bone Deposition
Increase Risk for Fracture
compression fractures of vertebrae
hip fractures
Role of calcium, vitamin D, estrogen, exercise
Calcitonin vs. Parathyroid Hormone

22. Osteoporosis