Chapter 20 detailed flashcards

Layers of blood vessel wall

tunica interna, tunica media, tunica external

Tunica Interna

endothelium, simple squamous epithelium. Functions: selectively permeable, vasomotor, smooth to prevent RBC from sticking, clotting mechanisms

Tunica Media

smooth muscle, often the thickest layer, function: provides vasomotion

Tunica Externa

or tunica adventitia. Functions: anchors blood vessel, passage for nerves and lymphatics

arteries…

have more muscle than veins, resistance vessels: withstand high BP, maintains BP

Conducting (elastic or large) arteries

aorta, common carotid artery, pulmonary trunk, common iliac a. elastic fibers vasavasorum. expand with ventricle systole and recoil with diastole. prevents BP decline to low between heart beats.

Distributing (muscular or medium) arteries

ex: racial artery, femoral artery. many layers of smooth muscle.

Small (resistance) artery

arterolies, lumen changes due to endocrine, nervous stimuli.

What is an aneurysm

weakened thin vessel walls. abnormal bulging of bv, pulsates with heartbeat, abdominal aorta, renal artery, circle of willis. hemorrhage (pressure on structures) , sending aortic aneurysm; etiologies,arteriosclerois + HTN, infections, congenital defect

metarterioles

link between arterioles + capillaries, smooth muscle cells act as pre capillary sphincters, perfusion with sphincter open

Arterial sense organs

sensory receptors, functions: monitor Bp and chemistry. sends info to brainstem. regulates HR, vasomotion, respiration.

Carotid Sinuses; Baroreceptor (stretch)

with high blood pressure leads to AP’s via X decrease HR. negative S-ANS leads to increase vasodilation which leads to decrease BP

Carotid + Aortic Bodies

monitor pH, Co2 ans O2…chemoreceptors send afferent info via CN IX and X

what are the different types of capillaries

continuous, fenestrated, ans sinusoids

what is continuous capillary

most tissues, tight junctions

intercellular clefts

4 nm wide; diffusion of H2O, glucose

no clefts in brain

what is fenestrated capillary

large filtration pores, 20-100 nm, organs that filter/absorb materials

ex: kidneys, endocrine glands, small intestine

what is sinusoids

irregular spaces filled with blood 30-40 um. allows passage of proteins (albumin) new RBC

ex: liver, bone marrow, spleen

Arterial bvs

general term that takes blood from heart

veins are capacitance vessels….

blood distribution in resting adult, majority of capillaries (90%) empty. veins contain 65% of blood

why can veins hold more blood than arteries

veins have less muscle and elastin tissues than arteries. they easily expand to serve as a blood resviour.

what are the different types of veins

postcapillary venules, muscular venules, medium sized veins, venous sinuses, large veins,.

postcapillary venules

for fluid exchange, WBC emigration

Muscular venules

up to 1 mm

Medium sized veins

named: ulnar, radial, saphenous veins.

venous valves present

venous sinuses

thin walls, large lumen, no smooth muscle, coronary + dural

large veins

more than 10 mm diameter. smooth m present, vena cavae, pulmonary veins, internal jugular veins, renal veins

Venous Valves

medium veins: infolding of the tunica internal that forms flaps to prevent back flow of blood

skeletal muscle pump: skeletal muscle contractions force blood through valves

Varicose Veins

venous pooling ruptured valves. due to long periods of standing, obesity, pregnancy, hereditary weak valves. signs: edema of legs, feet, pain, throbbing, hot and inflamed

different types of circulatory routes

simplest, portal, arteriovenous anastomosis, venous anastomosis, arterial anastomosis

simplest (most common) circulatory route

heart → arteries →capillaries → veins → heart

portal circulatory routes

2 consecutive capillary beds. kidneys, hypothalamus-pituitary, intestines-liver.

arteriovenous anastomosis

(shunt bypass capillaries) fingers, toes ears, palms.

venous anastomosis

veins empties into vein

arterial anastomosis

2 arteries merge heart, brain, joints. provides collateral blood supply

Mechanisms to return blood to the heart

1. skeletal muscle pump: muscle contraction and valves

2. gravity; veins of head + neck. sitting/standing

3. pressure gradient: generated by heart. primary force for venous return, venules (12-18mm hg) central venous return = 4.6 mm Hg at vena cavae

4. Thoracic pump: blood from abdomen → thorax. acts on the IVC

5. Cardiac suction: during ventricular systole, increase atrial space to draw blood in

Sedentary affects on venous return

decreased venous pressure can cause venous pooling which leads to increase venous pooling, decreased perfusion to brain, syncope.

Circulatory shock

inadequate cardiac output

cardiogenic shock

decrease or no blood ejected, ex MI

Low venous return shock

deficient in blood return

hypovolemic shock

most common, decreased blood volume, dehydration, burns, hemorrhage.

Obstructed venous return shock

tumor, aneurysm

Venous pooling shock

normal blood volume, increased blood in limbs due to sitting or standing

neurogenic shock

acute loss of vasomotor tone → vasodilation. es: brainstem trauma, or emotional trauma.

compensated shock

syncope restores cerebral blood flow hypotension triggers baroreceptor reflex → increase S- ANS output → increase HR → vasoconstriction and increased BP. stimulates renin secretion by kidneys → RAAS

decompensated shock

progress of insult → inadequate compensatory mechanism → decreased BP. increased HR leads to decreased coronary flow and ventricular filling → decreased myocardial function → decreased BP. increased vascular resistance + increased contractility → increased myocardial oxygen need and decrease O2. decreased myocardial function _> decreased BP

blood flow through the brain

stable, constant blood glow of 700-750 ml/min. pH and Co2 are the primary mechanisms

Hypercapnia

decreased pH often due to lack of blood flow → vasodilation. increased blood flow → increased pH o NL. decreased pH called acidosis. increased pH called alkalosis. H

Hypocapnia

increased pH often due to lack of C02 (hyperventilation) → vasoconstriction, dizziness, maybe syncope (passing out)

TIAs

transient ischemic attacks, stroke

Hypercholesterolemia

sleep apnea, chocking

blood flow through skeletal muscles

highly variable and dependent on level of physical activity. at rest entire skeletal muscle system may be 1 L/min. vigorous exercise can increase as much as 20L/min. local waste materials induce vasodilation (No, H+, CO2, lactic acid,

Pulmonary Blood Flow

only arteries with deoxygenated blood, low pressure (25/10 mm Hg) low velocity circuit. low capillary pressure, low oncotic pressure (slow flow velocity to allow time for gas exchange, absorption of fluids in capillaries) pulmonary arteries vasoconstriction when hypoxic

what is blood flow

amount of blood moving through a region per amount of time (mL/min). through an organ, tissue, or Bv.

Perfusion

flow?mas of tissue (organ) (mL/min/g)

blood flow dependent on

pressure and resistance

systolic pressure

break BP in ventricular systole

diastolic pressure

min BP in ventricular diastole

normal BP

120/75

what range does HTN start

135/90

hypotension causes

hemorrhage, dehydration, anemia, sepsis

MAP

DP + PP (pulse pressure) / 3 → indicates degree of O2 to all tissues

principles of BP

1. cardiac output: HR + SV

2. Blood Volume: kidneys by filtering the blood

3. resistance to flow; due to friction between blood and walls of blood vessels

blood viscosity

due to albumin and RBC

Anemia; hypoproteinemia

decrease viscosity, decrease resistance

polycythemia; dehydration

increased viscosity, increased resistance

arterioles

most significant bv

vasomotor, adjust bv radius

effects due to friction between blood + bv walls

vasodilation

increase radius increase flow due to decrease friction causes decrease BP…decrease SANS input

vasoconstriction

decrease radius, decrease flow due to increase in friction, increase SANA input

systemic blood flow velocity

aorta: fastest flow decrease at capillaries and increase at vena cavae. venous blood flow slower than arteries. arterioles; most significant to change peripheral R and blood flow velocity

local mechanism

metabolic theory of auto regulation.

tissues are hypoxic → wastes accumulate

C02, H+, K+, lactic acid, adenosine

vasodilation

vasoactive chemicals act on cells (endothelial cells, platelets, with exercise/trauma/inflammation → vasodilation)

reactive hyperemia: blood flow increase greater than normal (come in from cold)

angionogenesis: new blood vessel growth due to hypoxia, seen with pregnancy/uterine lining/coronary bypass growth, cancer

Neural

baroreflex

chemoreflex

medullary ischemic reflex

baroreflex (high BP)

baroreceptor → CN IX → medulla obl cardioregulatory nuclei.

decrease HR, decrease CO

negative vasomotor ctr; decrease SANS output to dilate peripheral arteries and veins decrease BP

doesn’t work for chronic HTN

chemoreflex

monitor CO2, O2, pH b y carotid and aortic bodies.

primary task to adjust respiratory system

secondary; stimulate vasomotor

hypoxemia, hypercapnia or acidosis

general vasoconstriction → increase BP increase lung perfusion + gas exchange

medullary ischemic reflex

automatic ANS response to correct decrease blood flow to brain

cardioaccelaratory center; increase HR and contraction force → increase CO

vasomotor center; peripheral vasoconstriction

increase BP increase greater blood flow to the brain

BP + Flow regulation, hormonal control

1. angiotension II : vasoconstrictor, increase BP

2. aldosterone : “salt saving” Na+ retention by kidneys → increase H2O → blood volume + increase BP

3. ADH : increase H2O retention, increase BP

4. ANP: opposes aldosterone, Na+ excretion, decrease BP

5. E, NE: a-adrengic r on bv → vasoconstriction increase BP; b-adrenergic r on coronary + skeletal muscle bvs → vasodilation + increase blood flow

purposes for vasomotion

1. continuously altering blood pressure throughout the body

2. managing perfusion and regional blood flow. changes in peripheral resistance, reroutes blood flow to different tissues and organs

Hypertension (HTN)

most common CVS disease

at least 30% of people 50+

leads to stroke, heart + kidney failure

increase after load → hypertrophy, excessive stench

decrease contractile force

endothelium damage → plaques + arteriosclerosis

• feedback cycle → HTN worsens