Question

In: Anatomy and Physiology

Select ALL That Apply .Osteoclasts: A.are derived from osteoblast, the osteogenic cells of developing bone. B.are...

Select ALL That Apply

.Osteoclasts:

A.are derived from osteoblast, the osteogenic cells of developing bone.

B.are giant, multinucleated cells with several nuclei and produce a secretion rich in acid phosphatase.

C.are essential for stabilizing the blood calcium level during chronic blood hypocalcemia.

D.are derived from osteogenic cells

E.only occur in regions of developing bone.

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Control of calcium metabolism is accomplished by the effect of several hormone on several different organs. Which of the following is true concerning the control of calcium metabolism?

A.PTH (parathyroid hormone) causes an increase in plasma calcium by its actions on bone and the kidney.

B.Calcitriolcauses an increase in absorption of calcium from the lumen of the digestive tract.

C.Calcitonin causes a decrease in plasma calcium by suppression bone resorption.

D.When plasma calcium increases, PTH decreases and calcitonin increases.

E.PTH can rapidly increase plasma calcium level by its action on the osteocytic membrane system.

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.Which of the following statements would be true concerningcompounds involved in calcium metabolism?

A.The most life-threating consequence of hypocalcemia is reduced blood clotting.

B.Vitamin D can be synthesized from a cholesterol derivative in the skin when exposed to sunlight.

C.PTH facilitates the activation of vitamin D which is necessary for the absorption of calcium and phosphate in the gut.

D.1,25 dihydroxycholecalciferol is the carrier protein for calcium in the blood.

E.The most rapid response to hypocalcemia is the activation of the osteocytic membrane system by PTH.

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.Endochondral bone:

A.development proceeds from masses of hyaline cartilage with shapes similar to future bony structures.

B.growth proceeds from a specialized region at the ends of the diaphys is called the epiphyseal plate.

C.is first laid down as a membrane like layer of primitive connective tissue that remains soft and membrane like throughout life.

D.is derived from the articular cartilage of the epiphysis.

E.is composed of only compact bone and cannot form the cancellous (spongy) bone found the epiphysis of long bone.

Expert Solution

1. Osteoclasts are are huge multinucleated osteocytes derived from osteoblasts (A,D), responsible for bone resorption (with the help of acid phosphatase (B)), required for the regulation of blood calcium levels (C). Hence, A, B, C and D are correct.

2. Answer: A.PTH (parathyroid hormone) causes an increase in plasma calcium by its actions on bone and the kidney. ; C.Calcitonin causes a decrease in plasma calcium by suppression bone resorption; D.When plasma calcium increases, PTH decreases and calcitonin increases.; E.PTH can rapidly increase plasma calcium level by its action on the osteocytic membrane system.

Explanation: Becuase of A and C, an increase in calcium levels will lead to a decrease in PTH and an increase in calcitonin. Calcitriol increases calcium absorption in the kidney, not the lumen of the digestive tract.

3. All are correct. Reduced blood clotting is due to hypocalcemia. PTH converts 25-hydroxycholecalciferol, which is inactive Vitamin D, into its active form.

4. Endochondral bone develops from the replacement of the hyaline cartilage (A). Ossification starts from the primary center of ossification,i.e. the middle of diaphysis, which proceeds to the secondary center, the epiphyseal plate (B). Hence, the answers are A, B, and C.

Sydney Mullin answered 1 year ago

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