lifestyle health and risk Flashcards
why do larger organisms require a circulatory system
diffusion distances too great
high energy requirements
what does a mass transport system help to do
maintain diffusion grad
ensure effective cell activity
bring substances quickly from 1 exchange site to another
why does water flow easily
cohesion- attraction of water molecules to each other (pull each other along)
adhesion- water h bonds to other molecules (eg side of vessel)
why is water a good solvent
polar
surrounds charged particles
pos attracted to O
neg attracted to H
surrounded molecules break apart (dissolved)
what are arterioles
arteries branch into them
transport blood to caps
what are venules
transport blood from caps to veins
what are the 3 layers of artery and vein walls
- endothelium
- smooth muscle and elastic tissue
- outer wall
describe the endothelium layer
one cell thick
lines lumen of all blood vessels
reduces friction for free blood flow
highly folded in arteries so can expand under high pressure
describe the smooth muscle and elastic tissue layer
withstand high pressure
muscle contraction contracts the lumen and can divert blood flow away from certain locations
elastic tissue maintains blood pressure and stretches and recoils to even out any fluctuations
thicker in arteries as higher pressure
describe the outer wall
contains collagen
protects from damage by overstretching
what is the structure of veins
thinner smooth muscle and elastic tissue layer
wider lumen so blood returns to the heart at adequate speed. less friction between blood and endothelium
valves to prevent back flow
no pulse cos further from heart
what is the structure of capillaries
thin permeable walls as substances leave blood to reach tissues
narrow lumen so rbc pass in single file so blood travels slowly so more time for diffusion
wall is a single layer of endothelial cells with pores to allow plasma to leak and wbc
what is the cardiac muscle
thick muscular layer
makes walls of heart
what are coronary arteries
supply cardiac muscle w oxygenated blood
branch off from aorta
why do atria have thinner muscular walls than vents
dont need to contract as hard
only pumping blood to vents
why does the left vent have the thickest walls
oxy blood to body
larger contraction
for higher pressure
what does the vena cava do
pumps deoxygenated blood from body to right atrium
what does the pulmonary artery do
pumps deoxygenated blood from the right ventricle to the lungs
