Question

Which blood vessels have the smallest diameter?
A. Capillaries
B. Arterioles
C. Venules
D. Lymphatic

Answer 1

Hint: These blood vessels transport blood between the arterioles and the venules to supply certain elements to the tissues having a very little diameter and are the part of the human circulatory system.

Complete answer:
The capillaries are the smallest blood vessels that have a diameter of around 5-10 micrometers. They are known as the smallest blood vessels of the body.

Additional Information:
 -Blood vessels are part of the circulatory system that helps in the transportation of blood throughout the body.
-They transfer not only blood but also nutrients, and oxygen to various body tissues.
-The blood vessels remove waste products and carbon dioxide from the tissues of the body.
-The functions of all the body tissues are dependent upon the blood vessels.
-The blood vessels are of five types: arteries, arterioles, capillaries, venules, and veins.
-Capillaries are also called microvessels which help in exchanging various substances.
-It helps in supplying oxygenated blood and removing the deoxygenated blood from the body.
-An arteriole is also a small blood vessel but larger than the capillaries, they developed from an artery.
-Venules supply blood from capillaries to the larger venules and veins.
-The lymphatic system is a part of the circulatory system and the immune system.
-The lymphatic system helps in maintaining the fluid balance in the body.

So, the correct answer is ‘Capillaries’.
Note: Capillaries were observed and described from the frog’s lungs in 1661 by Marcello Malpighi. Capillaries are of three types: continuous (continuous endothelial cell lining which allows smaller molecules to pass), fenestrated (have pores (fenestrae) in the endothelium), and sinusoidal (open-pore capillary called sinusoid having wide pores on the endothelium). It is also called a discontinuous capillary.