Histology Testbank: Vessels 1a

Instructions: For each histology question, pick the one best answer. This histology test bank is also useful for the histology questions on the USMLE (USMLE step 1).

1.
At what level of the vascular tree does gas exchange occur?
a. Capillary
b. Arteriole
c. Venule
d. Elastic artery
e. Muscular artery

Answer: a

Capillaries are very thin walled in order to easily allow the exchange of gases. Gaseous exchange between the blood and tissues occurs at the level of the capillaries.

Arterioles are small branches of arteries with only one or two layers of smooth muscle in the tunica media. Arterioles regulate the amount of blood going into the capillary bed.

Venules are small branches of veins.

Elastic arteries are the arteries leaving the heart and the major branches. The aorta is an elastic artery.

Most of the named arteries are muscular arteries (with the exception of the aorta and the major branches off the aorta). The dividing line between elastic arteries and muscular arteries is not clear cut. However, a pronounced internal elastic membrane and external elastic membrane are distinguishing characteristics of muscular arteries.

Histology hint from Sarah Bellham: Elastic arteries also have an internal elastic membrane. However, there is so much elastic material in the tunica intima of an elastic artery, that a single, discrete internal elastic membrane is not visible.

2.
Which layer in an artery is primarily skeletal muscle?
a. Tunica intima
b. Tunica media
c. Tunica externa
d. All of the above
e. None of the above

Answer: e

The tunica intima is the innermost layer of a blood vessel. It is lined by endothelium

The tunica media is the middle layer of a blood vessel. The tunica media is primarily smooth muscle.

The tunica externa or tunica adventitia is the outer layer of a blood vessel. In large vessels, the tunica adventitia contains vasa vasorum (blood vessels) and nervi vascularis (nerves).

3.
Which of the following is NOT a distinguishing feature between larger veins and arteries?
a. Veins have valves whereas arteries do not have valves
b. The tunics in veins are not as clearly delimited as are the tunics in arteries
c. The walls in veins are thinner than the walls in arteries
d. The lumen of a vein is smaller than the lumen of an artery
e. None. All of the above are true

Answer: d

Veins have valves whereas arteries do not have valves. The tunics in veins are
not as clearly delimited as are the tunics in arteries. The walls in veins are
thinner than the walls in arteries. The lumen of a vein is larger than the lumen of
an artery.

4.
In which structure are things moved across the epithelium via pinocytotic vesicles?
a. Continuous capillaries
b. Fenestrated capillaries
c. Sinusoidal capillaries
d. AV anastomoses
e. Venous sinus

Answer: a

A characteristic of continuous capillaries is that things are transported across the epithelium via pinocytotic vesicles.

A characteristic of fenestrated capillaries is the presence of pores or fenestrae.

Sinusoidal capillaries (sinusoids) are wide leaky capillaries. They are found in the liver, spleen, and bone marrow.

An arteriovenous anastomoses (AV anastomoses or AV shunt) is a direct route between arteries and veins. It bypasses the capillary bed.

A venous sinus is a venous space lined by endothelium. A venous sinus surrounding the brain exists which is called the dural sinus.

5.
What is a thoroughfare which is a an intermediate between an arteriole and capillary?
a. Metcapillary
b. Metartery
c. Metvenule
d. Metarteriole
e. None of the above

A metarteriole is a thoroughfare that can be considered an intermediate between an arteriole and capillary is a metarteriole.

6.
Which layer in an artery contains the endothelium?
a. Tunica intima
b. Tunica media
c. Tunica externa
d. All of the above
e. None of the above

Answer: a

The tunica intima is the innermost layer of a blood vessel. It is lined by endothelium

The tunica media is the middle layer of a blood vessel. The tunica media is primarily smooth muscle.

The tunica externa or tunica adventitia is the outer layer of a blood vessel. In large vessels, the tunica adventitia contains vasa vasorum (blood vessels) and nervi vascularis (nerves).

7.
What do you call the simple squamous epithelium that lines the blood vessels?
a. Epithelioid tissue
b. Mesothelium
c. Endothelium
d. Transitional
e. Pseudostratified

Answer: c

Epithelial tissue has cells that are very tightly packed together. There is always a free surface associated with epithelial tissue. If a tissue is composed of a conglomeration of cells in tightly packed together, but it does not have a free surface, the tissue is called epithelioid tissue. An example of epithelioid tissue is the parenchyma of the adrenal gland.

Mesothelium is simple squamous epithelium that lines the abdominal cavity, the pericardial cavity, and the thoracic cavity.

Endothelium is simple squamous epithelium that lines the vascular system.

Transitional epithelium is seen in the urinary tract. Transitional epithelium has dome shaped cells on the apical surface.

Pseudostratified epithelium is a type of epithelium that has cells which all touch the basement membrane. Pseudostratified epithelium is only one cell layer thick. Pseudostratified epithelium appears stratified, but it is not really stratified. Thus the name. The prefix "pseudo" means false, such as pseudonym or pseudo-science.

8.
In which of the following is a portal system NOT found?
a. Kidney
b. Liver
c. Muscle
d. Brain
e. None of the above is correct; a portal system is found in all of the above

Answer: c

The normal flow of blood is as follows: artery - arteriole - capillary - post capillary venule -vein. However, exceptions to this pattern of blood flow exist.

The phenomenon when a vein is between two capillary beds is called a venous portal system. An example of this is the hepatic portal system. Another example of a venous portal system is seen in the brain between the hypothalamus and pituitary.

The phenomenon when an arteriole is between two capillary beds is called an arterial portal system. This is seen in the kidney.

9.
What is the brachial artery?
a. Capillary
b. Arteriole
c. Venule
d. Elastic artery
e. Muscular artery

Answer: e

Capillaries are very thin walled in order to easily allow the exchange of gases. Gaseous exchange between the blood and tissues occurs at the level of the capillaries.

Arterioles are small branches of arteries with only one or two layers of smooth muscle in the tunica media. Arterioles regulate the amount of blood going into the capillary bed.

Venules are small branches of veins.

Elastic arteries are the arteries leaving the heart and the major branches. The aorta is an elastic artery.

Most of the named arteries are muscular arteries (with the exception of the aorta and the major branches off the aorta). The dividing line between elastic arteries and muscular arteries is not clear cut. However, a pronounced internal elastic membrane and external elastic membrane are distinguishing characteristics of muscular arteries.

Histology hint from Sarah Bellham: Elastic arteries also have an internal elastic membrane. However, there is so much elastic material in the tunica intima of an elastic artery, that a single, discrete internal elastic membrane is not visible.

10.
Which of the following is a distinct structure found specifically in the liver, spleen, and bone marrow?
a. Continuous capillaries
b. Fenestrated capillaries
c. Sinusoidal capillaries
d. AV anastomoses
e. Venous sinus

Answer: c

A characteristic of continuous capillaries is that things are transported across the epithelium via pinocytotic vesicles.

A characteristic of fenestrated capillaries is the presence of pores or fenestrae.

Sinusoidal capillaries (sinusoids) are wide leaky capillaries. They are found in the liver, spleen, and bone marrow.

An arteriovenous anastomoses (AV anastomoses or AV shunt) is a direct route between arteries and veins. It bypasses the capillary bed.

A venous sinus is a venous space lined by endothelium. A venous sinus surrounding the brain exists which is called the dural sinus.