Blood Vessels BIOl 244

artery

blood vessel that pumps away from heart

• arioles: empty into capillaries, smallest ___

• oxygen rich when systemic

capillaries

blood vessel that is the smallest in body, responsible for gas exchange of materials

• venules: smallest veins in body

veins

converage to carry blood to heart

• oxygen poor when systemic and vise versa

tunica intima

• contact with blood

• contains endothelium

• layer of blood vessel

tunica media

• bulkiest layer

• mostly circularly arranged smooth muscle

• regulated by vasomotor nerve fibers of ANS (allows for dilation or constriction)

tunia adventitia

• outermost blood vessel layer

• composed of loosely woven collagen fibers

• vasa vasorum

vasa vasorum

network of tiny blood vessels that nourish external tissue of large vessels

elastic arteries

thick walled arteries near the heart

• aorta and major branches

• largest in diameter, low resistance

• contain a shit tone of elastin

• expand and recoil to accomodate changes

muscular arteries

deliver blood to specific body organs

• distal to elastic arteries

• smaller internal diameter

• thickest tunica media of all vessels

arterioles

smallest arteries

• larger have all 3 tunics with the media being mainly smooth muscle

• smaller lead into capillary beds - single layer of smooth muscle around endothelial lining

capillaries

microscopic in size; smallest blood vessels

• only have thin tunica interna

• RBC pass through single file

• most highly vascular tissues

• pericytes

pericytes

smooth muscle cell responsible for permiability of capillary

capillaries

role of these are to exchange materials between blood and interstitial fluids

• gases, nutrients, hormones

continuous capillaries

capillary found in skin and muscle

• provide uninterrupted lining

  • cells joined by tight junctions

• contain pinocytotic vesticles

intercellular clefts

• gaps of unjoined membrane

• allow limited passage of fluids and small solutes

• characteristic of capillary

fenestrated capillaries

• contain fenestrations in some of the endothelial cells

  • covered by a thin membrane

fenestrated capillaries

capillaries that are

• much more permeable to fluids and small solutes

• found where capillary absorption or filtration occurs

sinusoids

capillaries that is

• highly notified, leaky

• found in bone marrow, lymphoid tissue, endocrine organs, liver

• large irregular shaped lumens

microcirculation

blood flows from an arteriole through a capillary bed to a venule

vascular shunt

short vessel that directly connects the arteriole and venule at opposite ends of the bed

• vessel within capillary bed
  

true capillaries

exchange occurs here

• vessel within capillary bed

metarteriole-thoroughfare channel

venule at the opposite ends of bed

terminal arterioles

feed capillary bed that leads into metarteriole

thoroughfare

met arteriole is continuous with the ________ channel

post-capillary venule

drains to the bed

pre-capillary sphincters

cuffs off smooth muscle fibers

• surround root of each capillary at metarteriole

• act as valves

true capillaries

____ _____ branch off the metarteriole and return to thoroughfare channel

venules

formed when capillaries unite

post capillary venules

the smallest venule that is porous

• fluid and white blood cells move easily from bloodstream through the wall

larger venules

one or two layers of smooth muscle cell

veins

thin vessel walls

• low pressure system

veins

contain

• large lumens

• venous valves that form folds in the tunica interna

• 65% of total blod supply is found here

varicose veins

dilated veins due to incompetent valves

• hereditary

• prolonged standing, obesity, pregnancy

• result: blood pools in lower limbs, valves weaken

vascular anastomoses

created when vascular channels unit

collateral channels

alternative pathways for blood to reach a given body region

arterial anastomoses

vascular channels that unite around joints, abdominal organs, brain, and the heart

• contain collateral channels

arteriovenous anastomoses

vascular channel that unites

• metarteriole-thoroughfare channel shunts off the capillary beds

venous anatomoses

vascular channel unite

• interconnect more freely

• common

blood flow

volume of blood flowing through a vessel, an organ, or the entire circulation in a given period of time

• measured in ml/min

CO

entire vascular system = blood flow is equivalent to ___

varies

blood flow in an organ ___ and depends on need

Blood pressure

force per unit area exerted on a vessel wall by blood

• measured is mmHg

pressure gradient

driving force in pushing blood through the circulatory system

resistance

• opposite to flow

• measure of friction blood encounters as it apsses throug the vessels

  • blood viscosity

  • total blood vessel length

  • blood vessel length

constant, not resistance, inversely related

what blood viscosity, total blood vessel length, and blood vessel length contribute to blood flow

difference in pressure/ resistance

equation for blood flow

• inversely proportionate to resistance

systemic blood pressure

• blood moves from area of high pressure to low pressure

• greatest at aorta and lowest at right atrium

arterial blood pressure

related by two factors

• elastic arteries close to the heart can be stretched

• volume of blodo forced thorugh them at any time

pulsatile flow

blood pressure rises and falls in the elastic arteries near the heart

systolic blood pressure

peak pressure required to eject blood from the left ventricle into the aorta

• avg. 120 mmHg

diastolic blood pressure

lowest level of pressure maintained during relaxation and filling

• avgs 70-80 mmHg

SBP - DBP

equation for pulse pressure

Mean arterial pressure (MAP)

the pressure that propels the blood to the tissues

• = DBP + (pulse pressure/3)

capillary blood pressure

blood pressure is low due to

• fragility

• extreme permeability

venous blood pressure

• steady pressure, about 15 mmHg

• pressure alone is not enough to stimulate adequate ___ return

venous return

three adaptations that are necessary for _____ ____

• respiratory pump

• skeletal muscle pump

• smooth muscle

respiratory pump

associated with pressure changes in body cavity during breathing

skeletal muscle pump

contraction of skeletal muscles squeezing veins, forcing blood back to heart

smooth muscle

constricts as a result of sympathetic control which increases venous return

cardiac output, peripheral resistance, blood volume

three major factors that regulate blood pressure

short term mechanisms

counteract moment-to-moment fluctuations in blood pressure by altering peripheral resistance

• for maintaining blood pressure

• neural and hormonal

neural

maintain adequate mean arterial pressure by altering diameters of blood vessels and distribution in certain organs

• baroreceptors

• chemoreceptors

vasomotor center

oversees changes in diameter of blood vessels

• located in medulla oblongata

• transmits impulses along vasomotor fibers to innervate muscle

constriction, relaxation

sympathetic input = ______

decreased sympathetic impulses = slight ___

• in vasomotor center

baroreceptor

regulates vasomotor activity via this pressure sensitive mechanoreceptor

• respond to changes in arterial pressure and stretch

• located in carotid and aortic arch

chemoreceptors

regulate vasomotor activity via receptors that respond to changes in blood levels of solutes

• respond to changes in O2, CO2, and H+

• located in the aortic arch and large arteries of neck

higher brain center

vasomotor regulator in cerebral cortex and hypothalamus send signals to medulla oblongata to modify blood pressure

adrenal medulla hormones

increase vasocrontriction and increase CO

atrial natriuretic peptide (ANP)

decrease blood volume and blood pressure

antidiuretic hormone (ADH)

increase blood volume and in high amounts causes vasoconstriction

angiotension II

stimulates vasoconstriction and stimulates aldosterone release

nitric oxide

causes vasodilation

renal regulation

counteract fluctations of blood pressure by altering blood volume

increase

if blood pressure is high, renal regulation will ___ rate of fluid filtration at the kidney

• blood volume decreases and blood pressure falls

renin-angiotensin mechanism

if blood pressure is low, renal regulation will use this mechanism

• aldosterone is released to increase blood volume and blood pressure