phisology unit 2

long bones

• job: support weight + enable movement

• curved to increase shatter resistance

short bones

• job: provide stability to joints that bear weight

• roughly cubed shaped

flat bones

• job: protect internal organs

• thin, flat, usually curved

irregular bones

• have complicated shapes that don’t fit any bone category

seasmoid bones

• job: protect tendons that run over joints from stress and wear

• short rounded, buried within tendons

funcs of skeletal system

• protects by encasing essential organs

• supports bearing weight of body

• stores minerals to be released into bloodstream + fats in yellow bone marrow

• manufactures red + white blood cells from red bone marrow

• movement of joints for bones

fracture repair

1. bone breaks, blood leaks

2. hematoma (blood clot) forms around broken bone

3. soft callus forms, fibrocartilage forms a temporary bridge between the broken bones

4. hard callus forms, osteoblasts replace soft callus with new bone

5. bone remodels, extra weak/broken bone is removed + replaced with stronger and organized bone

bone remodeling

1. Bone resorption: osteoclasts break down old or damaged bone, releasing acids and enzymes that dissolve the bone. Minerals, such as calcium and phosphate, can be released into the blood.

2. Reversal/transition: osteoclasts stop working, the area is prepared for new bone to be formed.

3. Bone formation: osteoblasts move into the area, producing new bone tissue called osteoid which contains proteins such as collagen.

4. Mineralization: minerals such as calcium and phosphate are deposited into the new bone, making the bone hard and strong.

5. Maintenance: some osteoblasts become osteocytes, which are mature bone cells + help monitor and maintain the bone.

excitability tissue

muscle’s ability to respond to stimuli (motor neurons, electricity

contractility tissue

muscle’s ability to shorten

extensibility tissue

muscle’s ability to be stretched without tearing

elasticity tissue

muscle’s ability to return to it’s original shape after being stretched

blood calcium is too LOW

• Stimulus: Blood calcium levels drop.

• Sensor/Receptor: Parathyroid glands detect the low calcium.

• Response: Parathyroid glands release PTH.

• Effect: PTH causes calcium to be added to the blood → blood calcium increases.

blood calcium is too HIGH

• Stimulus: Blood calcium is too high ↑

• Sensor: Thyroid gland

• Response: Thyroid releases calcitonin

• Effect: Calcium is moved into bone → blood calcium decreases

composition of bone organic

• 35% osteoid (ground substance + collagen)

• provides flexibility + tensile (pulling) strength

• lack of collagen = brittle bone disease

composition of bone inorganic

• 65% mineral salts (calcium)

• provides bone strength + hardness to resist compression

• lack of mineral salts = rickets