Correctly order the following key steps in the process of endochondral ossification
1. Chondrocytes die.
2. Osteoblasts build the bone collar on the external surface of the bone.
3. Perichondrium is invaded by blood vessels.
4. In the primary ossification center, osteoblasts replace calcified cartilage with early spongy bone.
5. Perichondrial cells differentiate into osteogenic cells then into osteoblasts.
A) 4, 3, 2, 1, 5 B) 3, 5, 2, 1, 4 C) 3, 1, 2, 3, 5 D) 3, 1, 4, 5, 2
Answer: B
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A) replacement of destroyed tissue by the same kind of cells B) formation of scar tissue C) proliferation of fibrous connective tissue D) inflammation
Spongy bone contains ________
A) lamellar bone B) osteons C) trabeculae D) osseous lamellae
Which of the following events occurs first?
A) The myosin head binds ATP and detaches from actin. B) The myosin head pivots toward the M line. C) Calcium ions are released from the sarcoplasmic reticulum. D) Calcium binds to troponin. E) Myosin cross-bridges attach to actin.
If the medulla of a lymph node is damaged, what components of the lymphoid system will be affected?
A) B cells B) NK cells C) T cells D) None; this region does not produce any types of lymphocytes. E) All of the answers are correct.