Histology Test

Question 1

An oophorectomized monkey is treated with high doses of estrogen. Which of the following changes is most likely to occur in the endometrium after 1 year of treatment?

Accepted Answer

Hyperplasia

Answer

Estrogen is a potent mitogen for endometrial cells, stimulating their proliferation. In an oophorectomized monkey, the absence of endogenous progesterone to counterbalance estrogen's effects, combined with high doses of exogenous estrogen, will lead to continuous stimulation of endometrial cell division. This sustained proliferation results in an increase in the number of endometrial cells, a process known as hyperplasia.

Question 2

Which of the following muscle cell components helps spread the depolarization of the muscle cell membranes throughout the interior of muscle cells?

Accepted Answer

T tubule

Answer

T-tubules (transverse tubules) are invaginations of the muscle cell membrane (sarcolemma) that penetrate deep into the muscle fiber. Their primary function is to rapidly transmit the action potential (depolarization) from the sarcolemma to the interior of the muscle cell, ensuring that all myofibrils contract simultaneously. This allows for efficient and coordinated muscle contraction.

Question 3

A new drug is developed that prevents the demyelinization occurring in the progress of multiple sclerosis. The drug protects the cells responsible for the synthesis and maintenance of myelin in the central nervous system. These cells are most likely which of the following?

Accepted Answer

Oligodendrocyte

Answer

Oligodendrocytes are the glial cells responsible for synthesizing and maintaining the myelin sheath in the central nervous system (CNS). Myelin insulates axons, allowing for rapid and efficient nerve impulse conduction. In multiple sclerosis, the immune system attacks and damages myelin in the CNS, leading to demyelination. Therefore, a drug protecting these cells would target oligodendrocytes.

Question 4

A 10-year-old boy undergoes an appendectomy. Granulation tissue develops normally at the incision site. Tissue remodeling begins at this site with degradation of collagen in the extracellular matrix by which of the following proteins?

Accepted Answer

Metalloproteinase

Answer

Tissue remodeling, including the degradation of collagen and other extracellular matrix components, is primarily carried out by a family of enzymes called matrix metalloproteinases (MMPs). These zinc-dependent endopeptidases break down various components of the extracellular matrix, including collagen, playing a crucial role in wound healing, tissue development, and disease processes.

Question 5

In which of the following nuclear structures is DNA actively transcribed to rRNA?

Accepted Answer

Nucleolus

Answer

The nucleolus is a distinct sub-organelle within the nucleus primarily responsible for the synthesis of ribosomal RNA (rRNA) and the assembly of ribosomal subunits. It contains the ribosomal DNA (rDNA) genes, which are actively transcribed into rRNA by RNA polymerase I. Therefore, the nucleolus is the specific site where DNA is actively transcribed to rRNA.

NBME Practice Test

NBME Practice Test

Histology Test