Question

Which one is single cell in thickness
A) Venule
B) Arteriole
C) Blood capillary
D) Artery

Answer 1

Hint: Arteries, veins, arterioles, capillaries and venules all belong to the category of blood vessels present in the human body. Each plays a particular role in the circulation of blood. Their function is to carry oxygen and nutrients along the body.

Complete answer:
We are well aware of the fact that all the options mentioned above are blood vessels. Arteries possess thick walls with multiple layers while the capillary is made up of a single layer made from endothecium.

Let us explore each option and reach the right answer.
A) Venules- In blood vessels parts and organs unite to form veins, and are known as venules. Their function is to return the blood to the heart.
B) Arteriole- These are the smallest arteries. Its primary function is to regulate the flow and intravascular pressure. A unique feature of it is that it actively responds to the physical stimuli and also responds to the change in chemical environment. These possess muscular walls.
C) Blood capillary – It is a small blood vessel that has a single cell thick wall. These are the smallest blood vessels. They transport blood between the venules and arterioles and connect them. Tissues that are very active possess a lot of capillaries in them like the kidney and lungs.
D) Artery- The blood flows in an artery with high pressure. These are present deep in the body. Its walls in the body are thick and tough. It’s lumen is constricted and valves are absent in arteries. These are pinkish in appearance. At the time when blood is not present in them they do not collapse as they have thick walls.

Venules, arteriole and artery possess thick walls that are made up of three layers which are –Tunica externa, tunica media and tunica interna. From the above discussion it becomes clear that blood vessels possess single cell thickness.

Therefore the correct answer is option ‘C’.

Note:
- Vasa vasorum is the blood capillary that is present in the walls of blood vessels which supply oxygenated blood and nutrients.
- Blood capillaries were discovered by Macello Malpighi in 1661 while examining the brain and other major organs.