Capillaries

What are continuous capillaries?

Most numerous, with a single layer of endothelium connected to a basement membrane.

Intercellular clefts: Allow movement of glucose, amino acids, and ions.

What are fenestrated capillaries?

Single layer of endothelium connected to a basement membrane with fenestrations and intercellular clefts.

Location: Kidneys, small intestines, endocrine glands.

Function: Allow movement of smaller proteins.

What are sinusoids?

Single layer of incomplete endothelium and basement membrane, with large fenestrations and intercellular clefts.

Location: Liver, bone marrow, spleen.

Function: Allow movement of RBCs, WBCs, and larger proteins.

What are the components of the capillary structure?

- Capillary bed

- Arteriole

- Metarteriole

- Thoroughfare channel

- Precapillary sphincters

- Post-capillary venules

What is a portal system, and can you give an example?

Blood flows through two capillary beds, separated by a portal vein.

Examples:

- Hypothalamo-hypophyseal portal system: Connects hypothalamus and pituitary.

- Hepatic portal system: Connects digestive organs to liver.

What is an anastomosis?

The merging of two or more vessels to feed or drain a capillary bed.

Types:

- Arterial anastomosis (e.g., superior and inferior epigastric arteries supply the abdominal wall)

- Venous anastomosis (e.g., cephalic, brachial, basilic veins drain the upper limb)