Chapter 15 - Capillaries and Lymphatic system

Why can capillaries perform nutrient/waste exchange?

capillary walls are thin (single cell layer thick) = lower distance gas has to travel

walls contain pores to allow for exchange easier

What two structures do capillaries have to control flow at a tissue bed?

1. metarteriole

2. precapillary sphincters

What are the 3 types of capillaries? Whats the diff?

1. continuous capillaries - simple diffusion; permeable

2. fenestrated capillaries - contains fenestrations, higher permeablability

3. sinusoids - large fenestration; extremely permeable

What are continuous capillaries permeable to?

H20, small solutes, glucose

What are the narrow gaps between adjacent endothelial cells in capillaries called?

intracellular clefts

Where are fenestrated capillaries found in the body?

kidneys, small intestine, endocrine organs

Where are continuous capillaries found in the body?

muscles, lungs, central nervous system; they are the most abundant

Where are sinusoids found in the body?

bone marrow, spleen, liver

What are sinusoids permeable to?

almost everything; proteins and cells

What aids the veins in returning blood back to the heart?

pumps and valves (fight gravity)

What two pumps aid the veins? Whats the diff?

skeletal muscle pump - contraction of skeletal muscle in lower limbs propel blood

respiratory pump - decreased thoracic pressure/increased abdominal pressure pushes blood in abdominal veins into thoracic veins towards atria

At rest, what percent of blood is in veins and venules?

60-65%

What 3 exhanges’s methods are used in the capillaries?

1. simple diffusion

2. transcytosis

3. bulk flow

What is the most important method of capillary exchange? What does it exchange?

simple diffusion; gases/nutrients/fluid

What does bulk flow regulate in the capillaries?

pressure and movement of large amounts of molecules in or out of capillary beds

What does bulk flow move?

large volumes of solutes in fluid together in the same direction

What are the two kinds of bulk flow?

1. filtration - bulk movement of H20/solutes from capillaries INTO interstitial fluid

2. reabsorption - bulk movement of H20/solutes from interstitial fluid INTO capillaries

What are starling forces?

net pressure that determines movement of fluid - net filtration pressure

What are the 4 kinds of starling forces? Give brief description

1. capillary hydrostatic pressure (Pc) - pressure of fluid on barrier

2. interstitial fluid hydrostatic pressure (Pif) - pressure of fluid outside vessel wall

3. plasma colloid osmotic pressure (πp) - amount of solutes in blood plasma

4. interstitial fluid colloid osmotic pressure (πif) - amount of solutes in interstitial fluid

What is the net filtration pressure formula?

NFPa = (Pc + πif) - (πp + Pif)

NFPv = (Pc + πif) - (πp + Pif)

What starling force is always 0?

interstitial fluid colloid osmotic pressure (πif)

What does a positive net filtration pressure mean? What about negative?

filtration; reabsorption

What two starling forces are filtration?

1. capillary hydrostatic pressure

2. interstitial fluid colloid osmotic pressure

What two staring forces are reabsorption?

1. interstitial fluid hydrostatic pressure

2. plasma colloid osmotic pressure

What is a capillary?

blood vessel that are the sites of nutrient and waste exchange (endothelium and basement membrane)

What is the lymphatic system?

a system that picks up excess fluid filtered by capillaries

What is the fluid inside vessels of the lymphatic system called?

lymph

How much excess fluid aren’t reabsorbed by the capillaries?

3 liters

What are the functions of the lymphatic system?

1. drains excess interstitial fluid

2. returns filtered plasma proteins back to blood

3. carries out immune responses

4. transports dietary lipids

What structures transport dietary lipids into blood?

lacteals