Anatomy Exam

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Date Submitted: 09/29/2012 03:32 PM

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1.) What is the endochondral ossification? In endochondral ossification, who are the two runners? Did each runner begin the race at the same time? What is in the lead? How does the race end? Be sure to describe any cells that are involved in this race.

Endochondral ossification is one of the two essential processes during fetal development by which bone tissue is created. In endochondral ossification the two runners of the race to create bone would be chondrocytes and osteoblasts. Starting with hyaline cartilage, the chondrocytes are the first off the starting line and begin to grow, making the center increase in size. The bone begins to calcify and the enlarge chondrocytes then die leaving hollow cavities within the cartilage. Blood vessels then penetrate the cartilage. Fibroblasts, the underdog from behind, migrating with the blood vessels turn in osteoblast. The osteoblasts begin manufacturing bone out of the enlarged hyaline cartilage. Therefore Osteoblast take the lead and first with the production of mature bone.

2.) What might account for Markus’s normal blood calcium levels? Describe any feedback loops, if appropriate.

Normally the level of calcium in the blood is carefully controlled. When the calcium level in the blood drops, the bone releases calcium to bring the level back to homeostasis. When the blood calcium level gets too high, the extra calcium is stored in the bones or is passed out of the body in urine and/or stool. A negative feedback loop is a type of control where the feedback helps to correct an error. In this case, the negative feedback loop is used to compensate for a shortage or a large amount of calcium.

3.) Given what you know about muscle contraction and neurophysiology, why are we willing to sacrifice bone density to maintain blood calcium?

The calcium in the blood is very beneficial. Calcium in the blood plays a role in the contraction of muscles, hormone secretion, and the relaxation and tightening of blood...