Chapter 19: Blood Vessels Flashcards
What are the three major types of blood vessels?
arteries, capillaries, veins
Tunica Intima
inner most layer; endothelium (simple squamous epithelium)
Tunica Media
middle; smooth muscle; elastic fibers; allows for vasoconstriction and vasodilation
Tunica Externa
aka tunica adventitia; loosely wooven collagen fibers, nerve fibers (Sympathetic NS) and lymphocytes; larger vessels have their own blood supply (vasa vasorum)
What is the thickest layer of arteries?
tunica media
What is the thickest layer of veins?
fibrous collagenous
Elastic Arteries
thick walled; large vessels near the heart; low resistance; more elastic tissue than smooth muscle in tunica media; serve as pressure resevoirs (expand and recoil) to maintain blood flow during diastole; ex) aorta, pulmonary trunk, common carotid artery, subclavian artery, and common iliac artery
Muscular Arteries
distributing arteries; deliver blood to body organs; tunica media with more smooth muscle than elastic tissue; banded by internal and external elastic membranes
Arterioles
resistance vessels; small lumen (high resistance); rgulate blood flow into capillary beds
Vasoconstriction
vasocontriction of smooth muscle cells constrict lumen which increases resistance which reduces blood flow
Vasodilation
of smooth muscle cells dilates lumen which decreases lumen which incrases blood flow
Capillaries
smallest blood vessels; walls of tunica intima (1 layer of endothelial cells) surrounded by a basement membrane); function as sites of exchange (gases, nutrients, hormones, metabolic wastes) between blood and interstitial fluid;
What are the three types of capillaries
continuous cappillary; fenestrated capillary; sinusoid capillary
Continuous Capillary
least permeable and most common; abundant in skin, muscles, lungs and CNS; often associated with pericytes; most have intercellular clefts (gaps that allow limited passage)
Pericytes
contractile stem cells that generate new vessels or scar, help control capillary permeability and stabilizer capillary walls
Fenestrated Capillary
have large fenestrations (pores) that increae permeability; occurs in areas of active filtration (kidney) or absorption (sm. intestine) and areas of endocrine hormone secretion
Fenestrations
swiss like holes that tunnel through endothelial cells
Sinusoid Capillary
most permeable; in limited location; occur in liver, bone marrow, spleen and adrenal medulla; lg. intercellular clefts and fenestrations; allow lg molecules and even cells to pass; macrophages
Capillary Beds
networds of 10-20 capillaries; branch from terminal arteriole and empty into postcapillary venule; blood flow controlled by arterioles diameter which is regualted by SNS and local chemical conditions
What are the two additional features of capillary beds of mesenteries?
vascular shunt and precapillary sphincters
Vascular Shunts
consists of metarteriole and thouroughfare channel that directly connects terminal arteriole and post capillary venules
Precapillary Sphincters
smooth muscle bands that regulate blood flow thru true capillaries; controlled by local chemcial conditions only
Venules
form when capillaries unite
Veins
fromed when venules unite; lg diameter lumen accomodates a large blood volume (blood resevoir); venous valves (folds of tunica intima) located in veins of extremeties and prevent backflow
Vascular Anastomoses
interconnected network of blood vessels; provide alternate paths for blood to reach a body region
Arterial Anastomoses
occur arround joints, abdominal organs, heart and brain
Venous Anastomoses
extremely abundant
Arteriovenous Anastomoses
vascular shunts of mesentries
Varicose Veins
valve failure
Hemorroids
varicose anal veins
Aneuryism
wall of a vessel (artery or vein) is very thin and pops; may bleed out quickly if an artery
Arteriosclerosis
something that is decreasing the elasticity of the arteries
Artheroscleroisis
fat deposit
Blood Flow
volume of blood per unit of time (ml/min)
Blood pressure
force exerted by blood against the wall of a vessel; mm/Hg
Resistance
opposition to blood flow; a measure of friction the blood encounters; greatest in peripheral (systemic) circulation
What are the three sources of resistance in blood vessels?
viscosity, vessel length, vessel diameter
Viscosity
thickness of blood; increase viscosity = increased resistance
Vessel Length
long vessel = increased resistance
Vessel Diameter
resistance increases as diameter decreases; most important factor
F =
delta P divided by TPR
Flow Rate of Blood
F; is directly proportional to the pressure gradients (delta P); if delta P increases then F increases; if delta P decreases then F decreases; it is indirectly proportional to vasciular resistance (TPR); if TPR increase then F decreases; if TPR decreases then F increases
Which vessels are primarily involved in vasoconstriction/vasodialation?
arterioles
Resistance
R or TPR: is far more important that delta P in regualting local blood flow bc R can be easily changed via vasoconstriction (increase R) and vasodilation (decrease R)
Blood Pressure
blood always flows from areas of increased blood pressure to areas of decreased blood pressure
Arterial BP
is pulsatile in the elastic arteries near the heart; BP is highest during ventricular systole (systolic P about 120 mmHg); BP is lowest during ventricular diastole (diastolic P bout 80 mmHg)
Pulse Pressure
systolic P (pressure) - Diastolic P; if BP is 120/70 pulse pressure is 50
Mean Arterial Pressure
MAP; diastolic P + pulse pressure/3; if BP is 120/70 and PP 50 then MAP is 86.7 mmHg
Vital Signs
body temp; respiratory rate (about 12 per minute); pulse (measured in radial artery); BP (measured in brachial artery; via ausculatarory method using a sphygmomanoametery; varies depending on where it is taken; 1st sound soft tapping, second sound sounds of kerotkoff disappear)
Capillary BP
about 35-17 mmHg and no longer pulsatile
Venous BP
about 17-0 mmHg and continuous (no pulsing); pressure too low to preomote adequate return
Modifications that Promote Venous Return
large lumens (decrease resistance); valves (prevent backflow); muscular pump (skeletal muscle activity, pushes blood up and valves keep blood up); respiratory pump (pressures changes in ventral blood cavity during breathing); sympathetic venoconstriction (SNS reduces volume of blood in veins)
Regulating BP
need to keep BP high enough for adequate tissue perfusion (blood flow) but low enough to prevent damage to vessels; BP varies directly with cardiac output, peripheral resistance (TPR), and blood volume; regulatory mechanisms target one or more of these
Short Term Regulation
neural controls; targets CO and TPR; cardiovascular center of medulla oblongata
If cardioacceleratory center increases CO…
then SNS increases HR and force of contraction which causes BP to increase
In cardioinhibitory center decreases CO…
it decreases BP; PNS lowers HR and force of contraction
Increased SNS activity…
causes vasoconstriction which increases TPR which increases BP
Decrased SNS activity…
causes vasodilation which lead sot decreased TPR which decreases BP
Baroreceptors
stretch receptors; located in carotid sinuses and aortic arch; monitors changes in BP; most important
Chemoreceptors
carotid and aortic bodies located near baroreceptors; monitors blood pH
Higher Brain Centers
hypothalamus; involved in fight or flight; exercising, or change in body temp
Short Term Regulation
hormonal controls; target TPR
Epinephrine and Norepinephrine
causes vasoconstriction whihc leads to increased TPR which leads to increased BP
Angiotensin II
leads to vasoconstriction which increases TPR which increases BP
Atrial Natrivretic Peptide
leads to vasodilation which leads to decreased TPR which leads to decreased BP
ADH
only when BP dangerously low; leads to vasoconstriction which leads to increased TPR which leads to increased BP
Long Term Regulation
kidgeys; targets blood volume
Direct Renal Mechanism
alters blood volume directly WITHOUT help of hormones
Indirect Renal Mechanism
renin-angiotensin-aldosterone mechanism); stimulates aldosterone release (increased Na absorption); stimulates increased ADH release (increase h2o absorption); increased thirst; vasoconstriction; overall increasing blood volume
Hypertension
chronoically elevated BP; systolic > 130 mmhg and/or diastolic >80mmHg
Primary Hypertension
what 90% of people with hypertension has; they do NOT know the cause; may be a culmination of things
Secondary Hypertension
what 10% of people with hypertension has; identified cause
Hypotension
BP falls below 90/60 mmHg
Circulatory Shock
inadequate blood volume which means blood cannot circualte normally; includes- hypovolemic shock, vascular shock, and cardiogenic shock
Hypovolemic Shock
most common; lg scale blood/fluid loss
Vascular Shock
loss of vasomotor tone which leds to decreased peripheral resistance
Cardiogenic Shock
inadequate circulation due to pump failure (multiple myocardial infarctions)
Intrinsic COntrol of Tissue Perfusion
autoregulation; control is entirely from within the tissues or organ
Short Term Autoregulation
local chemical condictions alterla local blood flow to organs and tissues as needed
Long Term Autoregulation
number of blood vessels in a region increases (angiogensis) and existing ones enlarge
Extrinsic Controls of Tissue Perfusion
control is from outside tissue or organ; act via DND nerves and hormones to maintain MAP and Redistribite blood during exercise; decrease blood flow from kidneys and digestive organs
Velocity of blood flow is fastest…
where cross sectional area of the vascular bed is least (aorta)
Velocity of blood flow is slowest…
where cross sectional area of the vascular bed is greatest (capillaries); slow flow allows time for exhange of nutrients and wastes
Capillary Exchange
movement of materials between blood and interstitial fluid; gases and lipid soluble molecules diffuse thru endothelial cells; water soluble solutes (amino acids and sugars) pass thru intercellular clefts or fenestrations; large molecules (proteins) transported cia cesivles
Bulk Flow
movement of fluids across capillary walls
Hydrostatic Pressure
HP; force exerted by blood against capillary wall
Osmotic Pressure
OP; force created by plasma proteins that can not leave the capillary
What is bulk flow due to?
differences between HP and OP at eaither end of capullar bed
HP and Capillaries
pushes fluid out of capillaries (filtration) at arteriole end
Colloidal OP and Capillaries
sucks fluid into capillaries (reabsorption) at venule end
What happens to excess fluid?
it is reabsorbed by lymphatic capillaries and returned to blood stream
Edema
abnormal accumulation of fluid in interstitial space resulting from imbalances of pressure that drive bulk flow or bloackage of a lymphatic vessel
