Question

19) Macrophages (1 point) a) Are small cells that secrete histamine b) Include T-cells and B-cells c) Produce melanin d) None of the above 20) Cells that resorb bone matrix are: (1 point) a) Osteoblasts b) Osteocytes Osteoids d) None of the above 21) Circumferential lamellae (1 point) a) form layers around a vascular channel b) form layers in small struts c) form layers around the surface of bone underneath the periosteum d) None of the above 22) Which of the following does not directly or indirectly require an energ source? a) Primary active transport

Answer 1

19.Option a is the correct answer.

Macrophages are small cells that secrete histamine.

Generally secrete means producing and discharge (release). When macrophages are activated by bacterial endotoxins through an enzyme histidine decarboxylase, they produce histamine and in a study when human lung macrophages are isolated and cultured for 24 hours, the macrophages acquired the capacity to release histamine.

So, option a will be the correct answer. The other options are not correct because macrophages does not include T-cells and B-cells and they do not produce melanin.

20. Option d is the correct answer.

Cells that resorb bone matrix are none of the above given. So, the cells that resorb bone matrix are generally osteoclasts. These osteoclasts are multinucleated and large cells with an abundant amount of cytoplasm, they lie in the cavities on the surface of the bone.

21. Option c is the correct answer.

Circumferential lamellae forms layers around the surface of bone underneath the periosteum.

Circumferential lamellae generally run around the circumference of the bone. Periosteum is a layer which is dense made up of vascular connective tissue that envelops the bone except at few areas such as surface of the joints.

So, basically circumferential lamellae is divided into two parts they are:

Inner circumferential lamellae that is seen on the inner side of the compact bone tissue and

Outer circumferential lamellae that is located on the outside.