Capillaries

Capillaries

smallest blood vessels

What does red blood cells of Capillaries pass through?

Single file

What are site-specific functions of Capillaries?

Lungs, Small Intestines, Endocrine gland, & Kidneys

Capillaries - Lungs 

oxygen enters blood & carbon dioxide leaves 

Capillaries - Small Intestines

receive digested nutrients

Capillaries - Endocrine gland

pick up hormones

Capillaries - Kidneys 

remove the nitrogenous wastes 

What are the three types of Capillaries?

Continuous, Fenestrated, & Sinusoids

Continuous Capillaries

Most common (skin & muscle) & Least permeable

Where does Continuous Capillaries occurs?

Most organs

What join epithelial cells in Continuous Capillaries? 

Tight junctions & desmosomes 

What does Continuous Capillaries have?

Intercellular Clefts

Intercellular Clefts

gaps of unjoined membrane

What does Intercellular cleft allow?

small molecules in & out of capillaries

Fenestrated Capillaries

Large fenestrations (pores) & Increase permeability.

What are Fenestrated Capillaries joined by?

Tight Junctions & desmosomes

What does Fenestrated Capillaries have?

pores in their endothelium

Where does Fenestrated Capillaries occur?

In areas of active absorption or filtration (high rates of exchange) in Small intestine, Glomeruli of Kidneys, Endocrine glands

Sinusoids 

wide & leaky capillaries found in some organs & most permeable

What describes the structural features of sinusoids?

usually fenestrated with wide open intercellular clefts

have a large diameter & twisted course

Where does sinusoids occur?

In special locations: bone marrow, liver, & spleen

What are the low-permeability capillaries? 

Blood-Brain barrier

What does blood-brain barrier capillaries have?

complete tight junctions

What is not present in blood-brain barrier capillaries? 

Intercellular clefts 

What pass through the blood-brain barrier capillaries?

Only vital molecules (glucose, O2, CO2)

What are allowed through blood-brain barrier capillaries?

Oxygen, Carbon dioxide, & some anesthetics

Capillary Beds 

network of capillaries running through tissues 

What is the name of the ring of skeletal muscle in Capillary Beds?

Precapillary Sphincters

Precapillary Sphincters

regulate the flow of blood to tissues

Capillary Beds tendons & ligaments are….

poorly vascularized

Capillary Beds Epithelia and Cartilage are…. 

avascular 

Arterioles Dilated

blood flows through capillaries

Arterioles constricted

no blood flows through capillaries