Histology Testbank: Blood Vessels 4a
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).
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.
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).
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.
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