18-4: Capillary dynamics and blood diseases Flashcards
tissue perfusion
blood flow through tissues, depending on need at the time
how do arterioles control tissue perfusion?
arterioles’ main function is to control peripheral resistance by changing diameter - this regulates blood flow to each organ
autoregulation
organs regulate their own blood flow by varying the diameter (resistance) of their arterioles, based on their need at the time
capillary dynamics
movement of fluid by bulk flow, while gas exchange is going on
The velocity of blood flow is _ in the aorta and _ in the capillaries
fastest; slowest (to allow adequate time for exchange of material btwn blood and body tissue)
How are materials (O2, CO2, nutrients) exchanged?
diffusion
filtration
movement of fluid and solutes out of hte capillaries into the interstital fluid
What 2 forces do capillary dynamics depend on?
hydrostatic pressure (water pushing) and osmotic pressure (solutes sucking)
capillary hydrostatic pressure
HPc pressure of the water in blood pushing fluid out of vessels
interstitial fluid osmotic pressure
OPif large proteins in the interstitial fluid draw water towrads them (sucking fluid out of capillaries and into tissues)
reabsorption
movement of fluid from interstitial fluid back into capillaries
capillary osmotic pressure
OPc large plasma proteins in blood suck fluid from interstitial spaces back into the capillaries
interstitial fluid hydrostatic pressure
HPif pressure of water in interstitial spaces pushing fluid back into the capillaries
What two forces does filtration depend on?
HPc and OPif
What two forces does reabsorption depend on?
OPc and HPIf
net filtration pressure
shows whether fluid will enter or leave capillaries (eg. whether net result is filtration or absorption)
NFP equation
NFP = filtration - reabsorption
NFP = (HPc + OPif) - (OPc + HPif)
if answer is positive - net filtration
if answer is negative - net reabsorption
NFP at the arterial end of the capillary is net __, and NFP at the venus end of the capillary is net __.
filtration; reabsorbtion
Some of the fluid filtered at the arterial end is returned to the CV system by ___.
lymphatic vessels
edema
when filtration exceeds reabsoprtion, there is an abnormal increase in interstitial fluid, causing tissues to swell
The heart is a _ pump, serving _ distinct circulations: _.
double; two; pulmonary circulation and systematic circulation
pulmonary circulation
short loop that runs from heart to lungs and back to heart; serves to bring blood into contact with air sacs in lungs so gas exchange can occur
What two chambers are involved in pulmonary circulation?
right ventricle and left atrium
What are the steps of pulmonary circulation?
Deoxy blood leaves R ventricle > pulmonary trunk > R and L pulmonary arteries > lungs
Inside lungs they divide into smaller arteries > arterioles > pulmonary capillaries where exchange of gasses occurs (CO2 passes from blood into alveoli of lungs, O2 diffuses from lungs into blood)
pulmonary capillaries > pulmonary venules > drain into 2 large pulmonary veins that carry oxy blood away from lungs
4 pulmonary veins return oxy blood to the L atrium of heart, completing the circut
systematic circulation
long loop that delivers food and O2 to all body tissues while removing CO2 and wastes
What two chambers are involved in systematic circulation?
L ventricle and R atrium
What are the steps of systematic circulation?
oxy blood is pumped from L ventricle to aorta
first two branches are coronary arteries supplying the heart muscle itself
the aorta arches upward and curves and runs downward as the descending aorta until it reaches the pelvis, where it splits into the common iliac arteries serving the lower extermities
All systematic arteries branch off from the aorta to supply each body organ; inside the organ they divide into arterioles and then capillary beds to exchange gasses and nutrients
nutrient poor, deoxy blood collects in venules, which unite to form systematic veins
Carry blood back to R atrium through inferior vena cava, superior vena cava, and coronary sinus
shock
failure of cardiovascular system to deliver adequate amount of O2 and nutrients to meet the needs of body tissue; if it persists, cells die and organs are damaged
What is the main symptom of shock?
Low SBP (< 90)
also cool, clammy, pale skin, sweating, thready (weak but rapid) pulse, thirst, confusion, tachycardia, low urine output
hypovolemic shock
due to loss of blood from an acute hemorrhage or excessive fluid loss (vomitting, diarrhea, burns, dehydration)
cardiogenic shock
inadequate cardiac function (MI, inflammation of heart, malfunctioning valves, etc) - heart-initated shock
neurogenic shock
loss of vasomotor tone caused by anesthesia, CNS damage, drugs, etc - results in widespread vasodilation - nerve-initated shock
anaphylactic shock
severe allergic reaction - histamine causes vasodilation and increased vessel permeability (eg. bee sting)
septic sock (or toxic shock)
tissue injury caused by bacterial toxins (vasodilators)
aneurysm
thin, weaked seciton of blood vessel that balloons outward; high risk of rupture causing massive hemorrhage, shock, stroke or even death
(can be caused by atherosclerosis, congenital vessel defect, trauma, syphylis; repaired with a graft or stent)
hypertension
chronically high blood pressure (SBP > 140 or DBP > 90)
cause usually unknown, but contributing factors include diet high in sodium, fat, and chlolesterol, obesity, age, race, stress, smoking, and heredity
controlled by dietary changes, exercise, weight loss, stop smoking, manage stress, take anti-hypertensive drugs
What is the danger of hypertension?
heart has to work harder to pump against high resistance > myocardium enlarges and needs more O2 (if it can’t get it, can result in angina or myocardial infarction)
strain on cerebral artery may lead to stroke; may also lead to renal failure and vascular disease
