Mechanical stress stimulates the deposition of mineral salts and collagen fibers within bones. Calcium, the predominant mineral in bone, cannot be absorbed from the small intestine if vitamin D is lacking. Vitamin K supports bone mineralization and may have a synergistic role with vitamin D. Magnesium and fluoride, as structural elements, play a supporting role in bone health. Omega-3 fatty acids reduce inflammation and may promote production of new osseous tissue. Growth hormone increases the length of long bones, enhances mineralization, and improves bone density. Thyroxine stimulates bone growth and promotes the synthesis of bone matrix. The sex hormones (estrogen in women; testosterone in men) promote osteoblastic activity and the production of bone matrix, are responsible for the adolescent growth spurt, and promote closure of the epiphyseal plates. Osteoporosis is a disease characterized by decreased bone mass that is common in aging adults. Calcitriol stimulates the digestive tract to absorb calcium and phosphate. Parathyroid hormone (PTH) stimulates osteoclast proliferation and resorption of bone by osteoclasts. Vitamin D plays a synergistic role with PTH in stimulating the osteoclasts. Additional functions of PTH include promoting reabsorption of calcium by kidney tubules and indirectly increasing calcium absorption from the small intestine. Calcitonin inhibits osteoclast activity and stimulates calcium uptake by bones.
osteoporosis
disease characterized by a decrease in bone mass; occurs when the rate of bone resorption exceeds the rate of bone formation, a common occurrence as the body ages
1. Wolff’s law, which describes the effect of mechanical forces in bone modeling/remodeling, would predict that ________
A) a right-handed pitcher will have thicker bones in his right arm compared to his left.
B) a right-handed cyclist will have thicker bones in her right leg compared to her left.
C) a broken bone will heal thicker than it was before the fracture.
D) a bed-ridden patient will have thicker bones than an athlete.
A
2. Calcium cannot be absorbed from the small intestine if ________ is lacking.
A) vitamin D
B) vitamin K
C) calcitonin
D) fluoride
A
3. Which one of the following foods is best for bone health?
A) carrots
B) liver
C) leafy green vegetables
D) oranges
C
4. Which of the following hormones are responsible for the adolescent growth spurt?
A) estrogen and testosterone
B) calcitonin and calcitriol
C) growth hormone and parathyroid hormone
D) thyroxine and progesterone
A
5. With respect to their direct effects on osseous tissue, which pair of hormones has actions that oppose each other?
A) estrogen and testosterone
B) calcitonin and calcitriol
C) estrogen and progesterone
D) calcitonin and parathyroid hormone
D
1. If you were a dietician who had a young female patient with a family history of osteoporosis, what foods would you suggest she include in her diet? Why?
Since maximum bone mass is achieved by age 30, I would want this patient to have adequate calcium and vitamin D in her diet. To do this, I would recommend ingesting milk and other dairy foods, green leafy vegetables, and intact canned sardines so she receives sufficient calcium. Intact salmon would be a good source for calcium and vitamin D. Other fatty fish would also be a good vitamin D source.
2. During the early years of space exploration our astronauts, who had been floating in space, would return to earth showing significant bone loss dependent on how long they were in space. Discuss how this might happen and what could be done to alleviate this condition.
Astronauts floating in space were not exerting significant pressure on their bones; they were “weightless.” Without the force of gravity exerting pressure on the bones, bone mass was lost. To alleviate this condition, astronauts now do resistive exercise designed to apply forces to the bones and thus help keep them healthy.