circulation Flashcards
important anatomy of arterioles, capillaries and veins (3)
- arterioles have muscular walls that can relax and dilate sever fold
- capillaries exchange fluid, nutrients, etc btwn blood and interstitial fluid- thin porous walls
- Venis are reservoir for blood. Thinner walls low pressure) but muscular and contractable
where blood is located at any given time (7)
- 84% systemic circulation;
- 64% veins
- 13% arteries
- 7% systemic arterioles and capillaries
- 16% lungs and heart
- 7% heart
- 9% lungs
2 types of blood flow
- laminar blood flow = long smooth blood vessels (max velocity in center)
- turbulent blood flow = when blood passes over obstruction, or sharp turn - occurs in large arteries (not small)
critical closing pressure
3- def, what causes it to occur and purpose
- pressure at which blood vessels may collapse (and unable to maintain blood flow) if pressure falls below critical value (20 mmHg)
- vessel will collapse when intravascular elastic and muscular forces in vascular wall, coupled with extravascular tissue pressure exceed intravascular distending pressure
- the point of this is to ration blood because we have 5L- not enough to fill all capillaries
blood vessel compliance (capacitance 3)
- vascular compliance is total quantity of blood that can be stored in portion of circulation for each mmH rise in pressure
- compliance = distensibility * vol
- result of collagen and elastin in walls
order of compliance (most -> least)
veins > aorta > arteries > arterioles
delayed compliance (def)
a vessel exposed to increased blood volume initially exhibits increase in P then progressive stretching of smooth muscle allows pressure to return to normal over minutes to hours (eg blood transfusion)
pulse pressure (2 def, and factors that affect it)
- diff btwn systolic and diastolic pressures (120-80 =40 mmHg)
- affected by stroke vol and compliance of arterial tree
diff btwn arterial and venous distensibility and gravitys effects (2)
- veins are 8x more distensible than arteries
2. venous return above the heart relies on gravity
neural factors controlling peripheral circulation (4)
- sympathetic/ parasympathetic
- arterial baroreceptors
- cardiopulmonary receptors
- CNS response*
- sympathetic vasoconstrictor- controlled by medula oblongotta (parasympathetic is relatively unimportant)
- arterial baroreceptors are sensitive to stretch; receptors sense p increases => release chemicals which cause vasodilation to decrease pressure
- cardiopulmonary receptors are sensitive to stretch; receptors sense p increases => release chemicals which decrease blood pressure
- CNS ischemic response - most important, and only kicks in if abp falls below 50 mmHg, we faint, which allows brain to get blood it needs
hormonal control of peripheral circulation
- epinepherine/ norepinephrine
- renin-angiotensene- aldosterone
- vasopressin
- Atrial natriuretic peptide
- epinephrine/ norepinephrine - increase BP by vasoconstriction
- renin-angiotense-aldosterone -in kidneys, decrease in arterial P eventually increases BP by salt retention
- vasopressin- antidiuretic hormone
- ANP - increase blood volume => more peeing (and therefore decreases BV and BP)
innervation of BV (2)
- arteries are inn by sympathetic NS
2. veins and capillaries have no innervation
lymph system (3)
- returns fluid, proteins and large particulate matter from interstitial space to blood (venous system!!)
- major route for absorption of fat in the GI system
- penetrates all tissues except: bone, CNS, superficial skin and endomysium of muscle
