Chapt 18, pt 3 - Capillary Exchange & Fluid Movement

How do capillary walls differ from other blood vessels?

Capillaries consist only of a single endothelial cell layer and basement membrane.

Why are capillary walls so thin?

Thin walls allow efficient exchange of gases, nutrients, and wastes.

What are the three types of capillaries?

Continuous capillaries, fenestrated capillaries, and sinusoidal capillaries.

What are continuous capillaries?

Capillaries with uninterrupted endothelial lining allowing only small molecules to pass.

Where are continuous capillaries commonly found?

In muscles, skin, lungs, and the central nervous system.

What are fenestrated capillaries?

Capillaries with pores that allow rapid exchange of larger molecules.

Where are fenestrated capillaries found?

Kidneys, endocrine glands, and small intestine.

What are sinusoidal capillaries?

Large irregular capillaries with gaps allowing passage of large proteins and cells.

Where are sinusoidal capillaries found?

Liver, spleen, and bone marrow.

What are the three main mechanisms of capillary exchange?

Diffusion, filtration, and osmosis.

What is diffusion in capillaries?

Movement of molecules from an area of high concentration to low concentration.

What substances move by diffusion across capillaries?

Oxygen, carbon dioxide, glucose, and waste products.

What is filtration?

Movement of fluid out of capillaries due to hydrostatic pressure.

What is osmosis?

Movement of water across a membrane due to osmotic pressure differences

What is hydrostatic pressure?

The pressure exerted by fluid against the walls of a container or vessel.

What is capillary hydrostatic pressure?

The pressure of blood pushing fluid out of capillaries.

What is colloid osmotic pressure?

The pressure created by plasma proteins pulling water into capillaries.

What plasma protein is most responsible for osmotic pressure?

Albumin.

What is net filtration pressure?

The balance between hydrostatic pressure pushing fluid out and osmotic pressure pulling fluid in.

What happens when hydrostatic pressure exceeds osmotic pressure?

Fluid moves out of the capillary into tissues.

What happens when osmotic pressure exceeds hydrostatic pressure?

Fluid moves from tissues back into the capillary.

What is edema?

The accumulation of excess fluid in tissues causing swelling.

What causes edema?

Increased hydrostatic pressure, decreased plasma proteins, blocked lymph drainage, or increased capillary permeability