Question

Choose the correct answer from the alternatives given.
The cells constituting walls of blood capillaries are known as:
a. Endothelial cells
b. Cord
c. Oxyntic cells
d. Plasma cells

Answer 1

Hint: Blood capillaries are the smallest blood vessels in the body. They help to connect veins and arteries and help in exchange of blood, gases and nutrients between the blood and tissues. There are three types of blood capillaries, continuous, fenestrated and sinusoidal capillaries.

Complete answer:
Capillaries are the smallest blood vessels in the human body. They help to connect veins and arteries and help in exchange of blood, gases and nutrients. Their function is to carry out the microcirculation in the body along with many other functions. These capillaries are of three types:
• Continuous capillaries: These are non-perforated capillaries which allow only small molecules to pass through them. They are mostly present in muscle, skin, and nerve tissues.
• Fenestrated capillaries: These are perforated capillaries that allow small molecules to pass through them. They are present in intestines, kidneys, and endocrine glands.
• Sinusoidal capillaries: These capillaries have large open pores. The pores are large enough to allow blood cells to pass through. They are mostly located in bone marrow, lymph nodes, and spleen.

> The blood capillaries are made up of endothelial cells which are supported by subendothelium consisting of basement membrane and connective tissues. Endothelial cells are derived from mesodermal cells. Mesodermal cells are one of the three germ layers which are formed during the early embryonic stage, gastrulation.

Functions of endothelial cells:
• They control the vascular wall functions.
• They take part in homeostatic functions.
• Endothelial precursor cells or EPC from the marrow and pre-existing blood vessels migrate to the site of injury or tumor growth.
• In the brain, these cells form a blood to brain barrier.
• They also have adhesive properties.
• They adjust in number and accommodate themselves according to the requirement.

Hence, the correct answer is option (A).

Note: Damage of endothelial cells or increased endothelin can lead to endothelium dysfunction. It can also be caused by several conditions such as hypertension, diabetes, smoking, and physical inactivity. A few symptoms of endothelial dysfunction are chest pain, shortness of breath, tiredness.