Capillaries

Capillary

A tiny blood vessel where substances are exchanged between the blood and the body cells.

Metarteriole

Short vessels that link arterioles and capillaries. Serves as a regulator of blood flow. Contains individual smooth muscle cells that form precapillary sphincters at the entrance to the capillary bed, controlling access based on the tissue's metabolic needs

Continuous capillaries

most common type of capillary. Continuous tube with small intercellular clefts

Fenestrated Capillaries

Tiny blood vessels with small pores, or "windows." The pores allow larger molecules to pass through, making them leakier than continuous capillaries. They are found in the kidneys, small intestine, pancreas, and endocrine glands

Sinusoid Capillaries

Larger, irregular capillaries with gaps in the walls, allows for the exchange of large molecules, including plasma proteins and blood cells. Found in the liver and spleen

Starling forces

A balance between hydrostatic and osmotic pressures on both sides of a membrane, essential for maintaining proper fluid volumes and solute concentrations inside and outside the vasculature

Blood hydrostatic pressure (FILTRATION)

-Drives fluid out of capillary
-High on arterial end of capillary (36 mmHg), low on venous end (16 mmHg)

Interstitial fluid osmotic pressure

pressure created by proteins present in the interstitial fluid; pulls fluid out of capillaries. Constant at 1 mmHg

Blood colloid osmotic pressure

The largest driving force for pulling fluid from the interstitial spaces back into the capillaries. Due to the presence of plasma proteins too large to exit capillaries. Averages 26 mmHg in both venous and arterial ends

Interstitial fluid hydrostatic pressure

outward push of interstitial fluid against outside of capillary walls. mmHg is close to zero except in cases of edema

Reabsorption

-blood colloid osmotic pressure
-interstitial fluid hydrostatic pressure

Filtration

-Blood hydrostatic pressure
-Interstitial fluid osmotic pressure

What percent of filtered fluid is reabsorbed?

85%