lecture 13 & 14 capillaries and viens + cardiovascular control mechanisms

functions of lymphatic system include:

• returning fluid to the cardiovascular system 

• clearing proteins from interstitial fluid 

• role in absorption of fat in the intestines  

• role in immune system 

emphasis on site of exchange

capillaries

• the site of exchange between the circulatory system and interstitial fluid 

fluid flow across capillary wall

capillary length

lymph capillaries in the tissue spaces

lymphatic system

edema

the accumulation of fluid in the interstitial fluid

• if lymphatic drainage is compromised, fluid will accumulate

• if balance of pressures between capillary hydrostatic and osmotic pressures may favor movement of fluid into interstitial space:

  • increased capillary pressure (typically due to increased venous pressure)

  • decreased plasma protein concentration (e.g. liver failure)

  • increased interstitial fluid protein (leakage, tissue damage) 

venules and veins return blood to heart

• low resistance

• pressure is low coming out of the capillaries

several factors assist with the return of blood of heart

• valves

• skeletal muscle pump

• respiratory pump

most of the blood is in systemic veins

the factors that influence cardiac output

factors that influence mean arterial pressure with 2 main pathways : one for cardiac output & another for total peripheral resistance

distribution of cardiac output at rest:

look at what happens if one vascular bed changes; if the system does not adjust, the blood flow changes to the others too!

block diagram of baroreceptor reflex

location of baroreceptors 

baroreceptors and the orthostatic response: arterial pressure stays constant, even with gravity causing blood to pool in the lower part of the body

baroreceptor reflex maintains pressure

tonic control of arteriolar diameter

organ blood flow