Lesson 10 - Blood Vessels and Circulation Flashcards
fluid filters out of the arterial end of capillaries and _____ re-enters venous ends
osmotically
hydrostatic pressure (HP) is..
_____at arterial end and ____ at venous end
high on the arterial end of the capillary and low on the venous end
capillary hydrostatic pressure (CHP) drives…
fluid out of the capillary
interstitial hydrostatic pressure (IHP) drives…
fluid into the capillary
deltaHP =
CHP - IHP
capillary HP - interstitial HP
colloid osmotic pressure (COP) draws….
fluid into the capillary
what does the drawing of water by the colloid osmotic pressure result from?
more plasma proteins in blood
oncotic pressure
net colloid osmotic pressure
oncotic pressure/deltaCOP =
COP = colloid osmotic pressure
blood COP - tissue COP
net filtration pressure (NFP)
the difference between…
the difference between net hydrostatic pressure and net osmotic pressure
net filtration pressure (NFP) equation
(CHP - IHP) - (BCOP - ICOP)
at the arterial end of the capillary the NFP is….
greater than zero
what does it mean when the NFP is greater than zero? (2)
- net hydrostatic pressure is greater than the net osmotic pressure
- fluid moves OUT of the capillary into the interstitial fluid
and the venous end of the capillary, the NFP is…
less than zero
what does it mean when the NFP is less than zero? (2)
- net osmotic pressure is greater than net hydrostatic pressure
- fluid moves INTO the capillary and out of the interstitial fluid
at the arterial end of capillaries, the balance of hydrostatic and oncotic pressures results in…(2)
(1) net filtration pressure (deltaNFP) (2) of 13mmHg out
at the venous end, the balance of hydrostatic and oncotic pressure results in….(2)
(1) net reabsorption pressure (2) of 7 mmHg inward
at the venous end, blood pressure is low so….
oncotic pressure overrides hydrostatic pressure
capillaries _____ _____ fluid at the arterial end and _____ it at the venous end
gives off, reabsorbs
capillaries reabsorb about _____ of the fluid they filter
85%
what two locations have major differences in capillary filtration/reabsorption?
- glomeruli of the kidneys
- alveolar capillaries in the lungs
the glomeruli of kidneys is devoted to…
filtration
the alveolar capillaries in the lungs are devoted to…
absorption, so fluid doesn’t fill the air spaces
variations in capillary filtration and reabsorption: resting tissue (4)
- most precapillary sphincters are constricted
- capillaries are collapsed
- BP is low
- reabsorption dominates
variations in capillary filtration and reabsorption: active tissue (2)
- capillary pressure rises
- filtration dominates
variations in capillary filtration and reabsorption: traumatized tissue
- release substances that increase permeability and filtration
edema
accumulation of excess fluid in a tissue
three primary causes of edema
- increased capillary filtration
- reduced capillary reabsorption
- obstructed lymphatic drainage
three primary causes of edema: increased capillary filtration (4)
can be caused by…
- kidney failure
- histamine
- old age
- poor venous return
three primary causes of edema: reduced capillary reabsorption (3)
can be caused by…
h.ld.dpd
- hypoproteinemia
- liver disease
- dietary protein deficiency
three primary causes of edema: obstructued lymphatic drainage
surgical removal of lymph nodes
pathological consequences of edema (4)
- tissue death
- pulmonary edema
- cerebral edema
- severe edema can cause circulatory shock
pathological consequences of edema: tissue death
oxygen delivery and waste removal are impaired
pathological consequences of edema: pulmonary edema (2)
- fluid in the lungs
- suffocation threat
pathological consequences of edema: cerebral edema (4)
this causes…?
- headaches
- nausea
- seizures
- come
pathological consequences of edema: severe edema
excess fluid in tissue spaces causes low blood volume and low blood pressure
venous return
flow of blood back to the heart
five mechanisms of venous return
- pressure gradient
- gravity
- skeletal muscle pump
- thoracic pump
- cardiac suction
what is the most important force in venous return?
blood pressure
central venous pressure
pressure where the venae cavae enter the heart, about 5 mmHg
venule pressure value
12-18 mmHg
gravity drains blood from where?
the head and neck
skeletal muscle pump (2)
(1) contracting limb muscles squeeze blood out of compressed portions of the veins, and (2) valves keep blood moving toward the heart
the thoracic (respiratory) pump (4)
(1) inhalation expands the thoracic cavity, (2) thoracic pressure on the inferior vena cava decreases, (3) abdominal pressure on the inferior vena cava increases, (4) and blood is forced upward toward the heart
blood flows faster with _____
inhalation
central venous pressure fluctuates during respiration due to the _____ ______
thoracic pump
central venous pressure during inhalation
2 mmHg
central venous pressure during exhalation
6 mmHg
cardiac suction
during contraction of the ventricles, valves are pulled slightly downward by the chordae tendineae and atrial space expands slightly drawing blood in
reasons exercise increases venous return (4)
- heart beats faster and harder, increasing CO and BP
- vessels dilate to increase flow
- increased respiratory rate means increased action of the thoracic pump
- increased skeletal muscle pump
reason venous pooling occurs with inactivity
venous pressure not enough to force blood back upward
what could potentially happen with prolonged standing?
CO may be low enough to cause dizziness or syncope
how can you prevent venous pooling?
periodically tensing leg muscles
circulatory shock
any state in which cardiac output (CO) is insufficient to meet the body’s metabolic needs
all forms of circulatory shock fall into these two categories
- cardiogenic shock
- low venous return (LVR) shock
three major forms of low venous return (LVR) shock
- hypovolemic shock
- obstructed venous return shock
- venous pooling shock
most common LVR shock
hypovolemic shock
hypovolemic shock
loss of blood volume due to trauma, burns, and dehydration
obstructed venous return shock
tumor or aneurysm compresses and vein and impedes its blood flow
venous pooling shock
long periods of standing, sitting, or widespread vasodilation
venous pooling shock: neurogenic shock
results from sudden loss of vasomotor tone causing vesseles to dilate
possible causes of neurogenic shock (2)
- brainstem trauma
- emotional shock
septic shock
bacterial toxins trigger vasodilation and increased capillary permeability
anaphylactic shock
severe immune reaction to antigen, histamine release, generalized vasodilation, increased capillary permeability
compensated shock
several homeostatic mechanisms bring about spontaneous recovery
ex. a person faints and falls to a horizontal position, gravity restores blood flow to the brain
decompensated shock
when compensation fails
ex. life-threatening positive feedback loops occur (myocardial ischemia causes infarction and decreases CO which slows blood flow to cause disseminated intravascular coagulation (DIC) to reduce venous return)
condition worsens and causes damage to cardiac and brain tissue
blood flow to what organ fluctuates less than any of the others?
the brain, 700ml/min
_____ of deprivation to the brain causes loss of consciousness
SECONDS
how long does the brain have to go without blood flow to cause irreversible damage?
four to five minutes
total blood flow in the brain is constant but…
blood is shifted to active brain areas from moment to moment
what regulates its own blood flow?
the brain
cerebral arteries _____ as systemic BP drops, _____ as BP rises
dilate, constrict
what is the main chemical stimulus to the brain to recognize BP?
pH
- not sure if I interpreted this correctly
poor _____ leads to to Co2 accumulation in the brain
perfusion (hypercapnia occurs)
hypercapnia in the brain leads to…(2)
- pH decrease
- triggers vasodilation
hypocapnia of the brain leads to…(4)
pi.sv.owh.ids.
- pH increase
- stimulates vasoconstriction
- occurs with hyperventilation
- may lead to ischemia, dizziness, syncope
transient ischemic attacks (TIAs)
brief episodes of cerebral ischemia
symptoms of TIAs (6)
- dizziness
- vision loss
- weakness
- paralysis
- headache
- aphasia (inability to understand or produce speech)
how long can TIAs last?
a moment to a few hours
what are often early warning signs of an impending stroke?
TIAs - transient ischemic attacks
what are TIAs caused by?
caused by spasms of diseased cerebral arteries
stroke (cerebral vascular accident CVA)
sudden death of brain tissue caused by ischemia
what can cause a stroke? (3)
- atherosclerosis
- thrombosis
- ruptured aneurysm
effects of a stroke (4)
b.p.ls.ls
- blindness
- paralysis
- loss of sensation
- loss of speech
blood flow of skeletal muscles at rest (2)
- arterioles constrict, most capillary beds are shut down
- total flow about 1L/min
blood flow of skeletal muscle during exercise (2)
- arterioles dilate in response to muscle metabolites such as lactate, CO2, H+
- blood flow can increase 20-fold as blood is diverted from the digestive and urinary organs
muscular contraction impedes flow by…
compressing blood vessels
_____ contraction causes fatigue faster than intermittent _____ contractions
isometric, isotonic
pressure in pulmonary arteries is only…
25/10 mmHg
why is pulmonary blood flow so much slower?
allows more time for has exchange
oncotic pressure overrides blood pressure in the pulmonary circuit, meaning…(2)
- pulmonary capillaries absorb fluid (almost no filtration)
- prevents fluid accumulation in alveoli
the unique response of the lungs to hypoxia (2)
- pulmonary arteries constrict in diseased area(s) of the lung that are receiving less O2 from the outside
- redirects flow to better ventilated region of the lung
lungs response to hypoxia is the opposite of the systemic arteries, they…
dilate in response to hypoxia to increase tissue perfusion
