Chapter 13: bone health and calcium Flashcards
Bone structure
Provides strength to support the body, allows for flexibility,
What percentage of bones is minerals
65%, make up the hardness of bones
Bone mineral density=
bone strength
What percentage of bones is organic structures
35% provide strength, durability and flexibility (mostly collagen
Collagen
fibrous protein in bone tissue
Two types of bone tissue
cortical and trabecular
Cortical bone
very dense tissue on the outer surface of the bone, makes up 80% of the skeleton
Trabecular bone
Scaffolding on the inside of bones, supports the cortical bone and makes up 20% of the skeleton
Bone growth
determines bone size, begins in the womb, continues into early adulthood
completed at 14 for girls and 17 for boys
Bone modeling
Determines the bone shape, begins in the womb and continues into early adulthood, 90% of woman’s bone density achieved by 17, majority of man’s during their 20s, peak bone density is 30
Bone remodeling
Maintains integrity of bone, replaces old bone with new bone to maintain mineral balance, involves bone resorption and formation, occurs predominantly in adulthood (density stable in 30’s starts irreversible decline (resorption exceeds formation)
Bone weakening over time
osteoclast > osteoblast activity as we age
calcium
most abundant mineral in the body
Calcium in bones
99% in bones
forms a matrix on collagen (hydroxyptite)
gives strength and rigidity, continuously remodeling
Calcium in body fluids
1% in body fluids , extracellular and intracellular compartments
what does calcium play a role in
chronic disease prevention, body weight
Calcium reabsorption
requires vitamin D, is enhanced in an acid environment (duodenum)
Functions of calcium
- form and maintain bones and teeth
- Assist with acid-base balance
- Transmission of nerve impulses
- Assist in muscle contraction
more mentions: blood pressure, initiate blood clotting, regulating various hormones and enzymes. Promotes weight loss?
Low blood calcium
Signals th parathyroid glands to secrete parathyroid hormone into the blood
High blood calcium
signals the thyroid gland to secrete cacitonin
Vitamin D in calcium absorption
stimulates calcium reabsorption from the kidneys into the blood, stimulated by the parathyroid hormone, and enhances the calcium reabsorption in the intestines, and stimulates osteoclast cells to break down bone releasing calcium into the blood (increase in blood calcium levels, and parathyroid hormone secretion inhibited)
Calcitonin
inhibits the activation of vit D, prevents calcium reabsorption in the kidneys, limits calcium absorption in the intestines, and inhibits osteoclast cells from breaking doen
calcium recommended dietary allowance
varies with age and gender from 1000 mg to 1300 mg per day
Calcium bioavailability
degree to which we absorb/utilize the nutrient, depends on the amount of dietary calcium and vit D
