Mass transport Flashcards
(15 cards)
The need for a circulartory system
SA to vol ratio is not large enough for diffusion alone to supply cells with O2 & nutrients
-Single-celled organisms can gain this directly from diffusion
Structures of the heart
Atrium- thin walls & elastic, stretch when filled with blood
–Ventricle- Thick & muscular walls to pum blood around the body
-Left atrium wall is thicker because it has to pump blood a mauch greater distsnace, so requires a higher prease and more force full contraction
The cardiac cycle-Atrial systole
-The walls of the atria contract
-Pressure increases forcing the atrioventricular valve open
-Blood is forced into ventricles
The cardiac cycle-Ventricular systole
-Walls of ventricles contract
-Pressure exceeds atrial pressure forcing the AV valve to shut
-Pressure increases forcing semilunar valves open, forcing blood out of the heart
The cardiac cycle-Diastole
-Atrial and ventricles relaxed
-Blood flows into the heart
-Pressure in the atria increases until AV valve opens
-Blood flows into ventricles
-Semi-lunar valves are shut
Arteries structure
-Thick walls to withstand high-pressure
-Elastic tissue, stretch & recoil smoothing blood flow
-Smooth muscle-vary blood flow
-Smooth endothelium-reduce friction of blood flow
Arterioles structure
Branch off arteries
-Thinner & less muscular wall
-Feed blood into capillaries
Capillary structure
Smallest blood vessel
-Walls are one cell thick for rapid exchange of substances
-Small lumen- forcing blood to travel slowly, more opportunity for diffusion to occur
Veins
-Valves to prevent backflow
-Large lumen to maximise vol of blood carried
-Thin wall as under low-pressure
Formation of tissue fluid
-At the arteriole end of the capillary high hydrostatic pressure, pushes molecules out of the capillary
-Proteins stay in the blood, creating a low water potential in capillaries
-Lower hydrostatic pressure at the venule end, so less fluid pushed out of the capillary
-Still lower WP in capillary so water flows into capillary from tissue fluid
-Overall more fluid leaves the capillary than returns, leaving tissue fluid
Odema
If blood pressure is high then greater hydrostatic pressure at arterioles. Pushing more fluid out of capillaries, and fluid accumulates around tissues
The function of tissue fluid
Liquid containing O2 and nutrients, serving tissues with solutes in exchange for waste & CO2
Lymphatic system
-Tissue fluid enters lymph capillaries
-Large molecules can enter the lymphatic system through large pores
-Lymph renters bloodstream close to the heart
-Returning any proteins that have escaped from the blood
Blood vs plasma
-Blood consists of plasma, RBC, and other molecules, and transports them around the body
-Plasma is the liquid portion of blood containing water and solvents, transport medium for dissolved substances
