anatomy and physiology i unit 4: the skeletal system physiology of the skeletal system
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Anatomy and Physiology IUnit 4: The Skeletal System
Physiology of the Skeletal System
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
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.
Parts of the Skeletal System
• Axial skeleton– Skull and bones that support it– Includes vertebra and ribs– 80 bones
• Appendicular skeleton– Limbs– 126 bones
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.
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
Joints
• Cartilage covers ends of movable bones– Reduces friction
• Lubricated by fluid from capillaries
Cartilage
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
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
Bone Structure
Haversian System
• Structure of compact bone
• Rings of bone tissue with blood vessels and nerves in the center
Haversian System
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
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
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.
Homeostatic Imbalances
Osteomalacia
•“Rickets” of adults.•Due to a lack of vitamin D.•Calcium is not deposited in the bones.•Bones become brittle.
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.
Age Related DysfunctionsArthritis:
Osteoarthritis- 90% of pop. By age 40chronic inflammation of articular cartilagecan be normal age-dependent change can also be pathology due to ?
Age-related changesdecrease blood supplytrauma
Osteoarthritis
Osteoporosis
Decline in Bone DensityBone Resorption > Bone Deposition
Increase Risk for Fracturecompression fractures of vertebraehip fractures
Role of calcium, vitamin D, estrogen, exerciseCalcitonin vs. Parathyroid Hormone
Osteoporosis