Capillaries consist of:


a. three thin tunics.
b. only a thin tunica intima with a well-developed internal elastic lamina.
c. a thin sheet of endothelium with a basal lamina.
d. stratified epithelium.

Verified step by step guidance

1. Identify the structure and function of capillaries in the circulatory system.
2. Understand that capillaries are the smallest blood vessels and are involved in the exchange of materials between blood and tissues.
3. Recognize that capillaries have a simple structure to facilitate efficient exchange of gases, nutrients, and waste products.
4. Recall that capillaries are composed of a single layer of endothelial cells and a basal lamina, which allows for easy diffusion.
5. Eliminate options that do not match the known structure of capillaries, focusing on the presence of a thin sheet of endothelium with a basal lamina.

Key Concepts

Capillary Structure

Capillaries are the smallest blood vessels in the body, primarily composed of a single layer of endothelial cells. This thin structure allows for efficient exchange of gases, nutrients, and waste products between blood and surrounding tissues. Unlike larger blood vessels, capillaries lack the additional layers of smooth muscle and connective tissue, making them uniquely suited for their role in microcirculation.

Tunica Intima

The tunica intima is the innermost layer of blood vessels, including capillaries. In capillaries, this layer consists solely of endothelial cells and a thin basal lamina, which provides structural support. This simplicity is crucial for facilitating the rapid exchange of substances, as it minimizes the distance that molecules must travel between blood and tissues.

Endothelial Cells

Endothelial cells line the interior surface of blood vessels, including capillaries. These cells play a vital role in maintaining vascular health, regulating blood flow, and controlling the permeability of the vessel wall. In capillaries, the thinness of the endothelial layer is essential for allowing the diffusion of oxygen, carbon dioxide, and other small molecules between the blood and surrounding tissues.