CH 20 Flashcards
Arteries
Carry blood away from heart (efferent)
Veins
Carry blood back to heart
(afferent)
flat, thin, no crinkle
Capillaries
connect smallest arteries to veins.
exchange, gas, nutrients, and waste
tunica interna (tunica intima)
Endothelium:
Lines the blood vessel and is exposed to blood.
acts as a selectively permeable barrier. secretes chemicals that stimulate dilation or constriction of the vessel.
Endothelium
repels blood cells and platelets (prostacyclin) that may adhere and form a blood clot.
Leukocyte can leave stream into tissue?
diapedesis or emigration
Tunica media
vasomotion:
- middle layer
- smooth muscle, collagen, elastic tissue.
- Vasomotion: changes in diameter of the blood vessel brought by smooth muscle.
Tunica externa
vaso vasorum:
- outermost layer
- small vessels that supply blood to at least the outer half of larger vessels.
Arteries are sometimes called
resistance vessels
Conducting (elastic or large) arteries
- biggest arteries
- aorta, common carotid, subclavian, pulmonary trunk, and common iliac arteries.
- expand during systole, recoil during diastole which lessens fluctuation in blood pressure.
distributing (muscular or medium) arteries
- distributes blood to specific organs.
- brachial, femoral, renal, and splenic arteries
- smooth muscle layers 3/4 of wall thickness
resistance (small) arteries
- Arterioles: smallest arteries (control amount of blood to various organs) leading into capillary bed
- thicker tunica media and very little tunica externa
Metarterioles (control profusion)
- short vessels that link arterioles to capillaries.
- muscle cells form a precapillary sphincter about entrance to capillary
Aneurysm
weak point in an artery or the heart wall.
-forms a thin walled, bulging sac that pulsates with each heartbreak and may rupture at any time.
Dissecting aneurysm
blood accumulates between the tunics of the artery and separates them, usually because of degeneration of the tunica media.
cause of aneurysm?
result from congenital weakness of the blood vessels or result of trauma or bacterial infections such as syphilis.
-most common cause os atherosclerosis and hypertension
capillaries
site where nutrients, wastes and hormones pass between the blood and tissue fluid though the walls of the vessels.
(exchange vessels)
Where are capillaries absent or scarce?
tendons, ligaments, epithelia, cornea, and lens of the eye.
-other funds? to exchange nutrients synovial or aqueous.
continuous capillaries
occur in most tissues (lead to muscles or brain, glucose)
fenestrated capillaries
kidneys, small intestine
- organs that require rapid absorption or filtration.
- endothelial cells riddled with holes called filtration pores (fenestrations)
- monomers
Sinusoids (discontinuous capillaries)
liver, bone marrow, spleen
- irregular blood-filled spaces with large fenestrations.
- allow proteins (albumin), clotting factors, and new blood cells to enter the circulation.
When capillaries open
capillaries are well perfused with blood and egg in exchanges with the tissue fluid
when sphincters closed
- blood bypasses the capillaries
- flows through thoroughfare channel to venule
postcapillary venules
smallest veins
-more porous than capillaries so also exchange fluid with surrounding tissues.
muscular venules
up to 1mm in diameter
-one or two layers of smooth muscle in tunica media
Medium veins
up to 10mm in diameter
-thin tunica media and thick tunica externa
varicose veins result in part from the failure of these valves:
venous valves
Venous Sinuses
veins with thin walls, large lumens, and no smooth muscle
-not capable of vasomotion
Large veins
Larger than 10mm
-smooth muscle in all 3 tunics
Ex’s: venae cavae, pulmonary veins, internal jugular veins, and renal veins.
Varicose vains
blood pools in the lower legs in people who stand for long periods stretching the veins.
-hereditary weakness, obesity, and pregnancy also promote problems.
Hemorrhoids
varicose veins of the anal canal (valsalva)
Circulatory routes: simplest and most common
heart-arteries-arterioles-capillaries-venules-veins
-passes through 1 network of capillaries from when it leaves heart and back
Portal system
blood flows through 2 consecutive capillary networks before backlit o heart.
- between hypothalamus and anterior pituitary
- in kidneys
- between intestines to liver
Anastomosis
the point where two blood vessels merge
Arteriovenous anastomosis (shunt)
- artery flows directly into vein by passing capillaries
- fingertips, toes
Venous anastomosis
- most common
- one vein empties directly into another
- reason vein blockage is less serious than arterial blockage
Arterial anastomosis
- 2 arterial merge
- provides collateral routes of blood supply to a tissue
- coronary circulation and around joints
Blood supply to a tissue can be expressed in terms of ____ and ____
Flow and perfusion
Blood flow
the amount of blood flowing through an organ, tissue, or blood vessel in a given time (mL/min)
Perfusion
the flow per given volume or mass of tissue in a given time (mL/min/g)
At rest, total flow is quite _____, and is equal to the cardiac output.
Exersize?
constant
5.25L/min
15L/min (the pump)
Hemodynamics
physical principles of blood flow based on pressure and resistance.
-the greater the pressure difference between 2 points, the greater the flow; the greater the resistance the less the flow.
Blood pressure
measure at_____ of arm using _____________.
the force that blood exerts against a vessel wall
-brachial artery; sphygmomanometer
systolic pressure
peak at arterial BP taken during ventricular contraction. artery is maximally stretched,
Diastolic pressure
minimum arterial BP taken during ventricular relaxation between heart beats. artery recoils.
normal BP in young adult
120/75mm Hg
Pulse pressure
difference between systolic and diastolic pressure.
-measures elasticity and recoil of arteries.
~40 is normal. above 60 may indicate cardiovascular disease.
Mean arterial pressure (MAP)
the mean pressure one would obtain ny taking measurements at several intervals throughout the cardiac cycle (70-100 good)
Hypertension
high BP
- chronic is resting BP>140/90
- can weaken small arteries and cause aneurysms
Hypotension
chronic low resting BP
- caused by blood loss, dehydration, anemia
- inadequate perfusion to tissues (necrosis)
one of the body chief mechanisms in preventing excessive blood pressure is the ability of the arteries to ______ and _______ during the cardiac cycle.
stretch and recoil
importance of arterial elasticity
expansion and recoil maintains steady flow of blood through cardiac cycle
- smoothes out pressure fluctuations
- decerases stress on small arteries
Why does BP rise with age?
- arteries less distensible and absorb less systolic force
- loss of elastic fibers
BP is determines by:
cardiac output, blood volume, and peripheral resistance
Peripheral resistance
the opposition to flow that blood encounters in vessels away from the heart.
- blood viscosity
- vessel length
- vessel radius
1.Blood viscosity
- RBC count and albumin concentration elevate viscosity the most.
- decreased viscosity with anemia and hypoproteinemia speed flow
- increased viscosity with polycythemia and dehydration slow flow
2.Vessel length
- the farther liquid travels through a tube, the more cumulative friction it encounters.
- pressure and flow decline with distance
- adiopse
3.Vessel radius
most powerful influence over flow
-only significant was of controlling peripheral resistance.
Vasomotion
change in vessel radius
Vasoconstriction
by muscular effort that results in smooth muscle contraction
Vasodialtion
by relaxation of the smooth muscle
-atherosclerosis
Vessel radius affects ________
blood velocity
Laminar flow
flows in layers, faster in center
From aorta to capillaries, blood velocity decreases for 3 reason:
- greater distance, more friction to reduce speed.
- smaller radii of arterioles and capillaries offers more resistance.
- farther from heart, the number of vessels and their total cross-sectional area become greater and greater (divergence)
From capillaries to vena cava, flow increases again
- decreases resistance going from capillaries to veins
- convergence
______ are the most significant point of control over peripheral resistance and flow.
Arterioles
- highly capable of vasomotion
- arterioles produce half of the total peripheral resistance.
_______ a quick and powerful way of altering blood pressure and flow
3 ways of controlling?
Vasomotion
- local control
- Neural control
- Hormonal control
Autoregulation
the ability of tissues to regulate their own blood supply
Metabolic theory of autoregulation
if tissue is inadequately perfused, wastes accumulate (K+, lactic aside, CO2) simulating vasodilation which increases perfusion.
- blood stream delivers oxygen and removes metabolites
- when wastes are removed, vessels constrict
Vasoactive chemicals
____, ____, ____ stimulate vasodilation
Endothelial cells secrete _______ and ______ and________
- substances secreted by platelets, endothelial cells, and perivascular tissue to stimulate vasomotion.
- histamine, bradykinin, prostaglandins
- prostacyclin, nitric oxide (vasodilators), and endothelia’s (vasoconstrictor)
Reactive hyperemia
if blood supply cut off (wastes increase) then restores, flow increases above normal
Angiogenesis
growth of new blood vessels
- regrowth of uterine lining, around coronary artery obstructions in, in exercised (aerobic) muscle, and malignant tumors, adipose
- regression
- controlled by growth factors
________ center of medulla oblongata exerts _______ control over blood vessels through the body.
Vasomotor; sympathetic
____________ respond only to local and hormonal control due to lack of innervation.
precapillary sphincters
Vasomotor center is the integrating center for 3 autonomic reflexes.
- baroreflexes
- chemoreflexes
- medullary ischemic reflex
Baroreflex
- increases in BP detected by _____.
- signals sent to brainstem by way of _________
am automatic, negative feedback response to changes in BP.
- carotid sinuses
- glossopharyngeal nerve (blood flout brain)
Chemoreflex
an autonomic response to changes i blood chemistry.
-especially pH, and concentration of O2 and CO2
Chemoreceptors called ____ bodies and _____ bodies.
aortic; carotid
- located in aortic arch, subclavian arteries, external carotid arteries.
- processed in medulla
Primary role
adjust respiration to changes in blood chemistry
secondary role
vasomotion
- hypoxemia, hypercapnia, etc.
- stimulate breathing
Medullary ischemic reflex
automatic response to a drop in perfusion of the brain.
-medulla monitors own blood supply
other brain centers can affect vasomotor center
stress, anger, and arousal can also increase BP
hormones influence BP
- some through their ____
- some by regulating ___
- vasoactive effects
- water balance
Angiotensin 2
potent vasoconstrictor
- raises BP
- promotes Na+ and water retention by kidneys
- increases blood volume and pressure
- renin (kidneys)-angiotensin 1-angiotensin 2 (lungs)
Atrial natriuretic peptide
increases urinary sodium excretion
- reduces blood volume and promotes vasodilation
- lowers BP
____ promotes water retention and raises BP
ADH
-vasoconstrictor
Epinephrine and norepinephrine effects:
most blood vessels
-bind to a-adernergic receptors (vasoconstriction)
skeletal and cardiac blood vessels
-nid to b-andernergic receptors (vasodilation)
Localized vasoconstriction
if a specific artery constricts, the pressure downstream drops, pressure upstream rises
-enables routing blood to different organs as needed.
most important blood in body is in?
capillaries
capillary exchange
two way movement of fluid across capillary walls
-water, oxygen, glucose, amino acids, lipids, minerals, antibodies, hormones, wastes, carbon dioxide, ammonia.
mechanisms involved in capillary exchange?
- diffusion
- transcytosis
- filtration
- reabsorption
____ the most important form of capillary exchange.
diffusion
capillary diffusion can only occur is:
-the solute can permeate the plasma membranes of the endothelial cell or find passages large enough to pass through (filtration pores and intracellular clefts)
lips soluble substances
steroid hormones, O2, and CO2 diffs easily through plasma membranes
water soluble substances
glucose and electrolytes must pass through filtration pores and intracellular clefts
Transcytosis
endothelial cells pick up material on one side if the plasma membrane by pinocytosis or receptor mediated endocytosis, transport vesicles across cell, and discharge material on other side by exocytosis
-important for fatty acids, albumin, and some hormones (insulin)
Blood hydrostatic pressure
drives fluid out of capillary
-high on arterial end. low on venous end
Colloid osmotic pressure
oncotic pressure:
draws fluid into capillary
-results from plasma proteins (albumin) more in blood
=net COP (blood COP-tissue COP)
Hydrostatic pressure
physical force exerted against a surface by a liquid (ex: BP)
Capillaries absorb about ____ of the fluid they filter.
Other ____ is absorbed by the _______ and returned to the blood
85%
15%
lymphatic system
Edema
tje accumulation of excess fluid in a tissue.
-occurs when fluid filters into a tissue faster than it is absorbed.
3 primary causes of edema
increased capillary filtration
-kidney and heart failure, histamine release, old age, poor venous return, highBP
reduced capillary absorption
-Hypoproteinemia, liver disease, dietary protein deficiency
Obstructed lymphatic drainage
-surgical removal of lymph nodes
Tissue necrosis
oxygen delivery and waste removal impaired
pulmonary edema
suffocation threat
cerebral edema
headaches, nausea, seizures, and coma
severe edema or circulatory shock
excess fluid in tissue spaces causes low blood volume and low blood pressure
Venous return
- pressure gradient
- _____ drains blood from head and neck.
- ______ in the limbs
the flow of blood back to the heart
- BP most important, 7-13mm Hg venous pressure to heart, venules 12-18mm to central venous pressure: point where the venae cavae enter the heart.
- gravity
- skeletal muscle pump
Thoracic (respiratory) pump
inhalation-thoracic cavity expands and thoracic pressure decreases, abdominal pressure increases forcing blood upward.(central venous pressure fluctuates)
-2mm Hg (inhalation), 6mm Hg (exhalation)
Ways exercise increases venous return:
- heart beats faster and harder, increasing CO and BP.
- vessels of skeletal muscles, lungs, and heart dilate and increase flow.
- increased respiratory rate, increases action of thoracic pump.
- increased skeletal muscle pump.
Venous pooling
occurs with inactivity
- pressure not enough to force blood up
- with prolonged standing, CO may be low enough to cause dizziness
- jet pilots wear pressure suits
Circulatory shock
any state in which cardiac output is insufficient to meet the body’s metabolic needs
Cardiogenic shock
inadequate pumping of heart (MI)
Low venous return
cardiac output is low because too little blood is returning to the heart
3 principle forms of circulatory shock:
- Hypovolemic shock
- Obstructed venous return shock
- Venous pooling (vascular) shock
Hypovolemic shock
most common
-loss of blood volume; trauma, burns, dehydration
Obstructed venous return shock
tumor or aneurysm compresses a vein
Venous pooling (vascular) shock
Long periods of standing, sitting, or widespread vasodilation
Neurogenic shock
loss of vasomotor tone, vasodilation.
-causes from emotional shock to brainstem injury
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: if a person faints and falls to horizontal position, gravity restores blood flow to the brains.
Decompensated shock
- triggers when the compensated shock mechanism fails.
- life threatening positive feedback loops occur.
- condition gets worse causing damage to cardiac and brain tissue.
Cerebral arteries dilate as systemic BP___, constricts as BP _____.
drops
rises
main chemical stimulus
pH
Hypercapnia
CO2 levels increase in brain , pH decreases, triggers vasodilation
Hypocapnia
raises pH, stimulates vasoconstriction
-occurs with hyperventilation, may lead to ischemia, dizziness, and sometimes syncope.
Transient ischemic attacks (TIA’s)
brief episodes of cerebral ischemia
- caused by spasms of diseased cerebral arteries
- dizziness, loss of vision, weakness, paralysis, headache, or aphasia.
- lasts from a moment to a few hours.
- often early warning of impending stroke.
Stroke or cerebral vascular accident
sudden death of brain tissue caused by ischemia
-atherosclerosis, thrombosis, ruptured aneurysm.
Hypertension
most common cardiovascular disease affecting about 30% of americans over 50
-silent killer
Primary hypertension
obesity, sedentary behavior, diet, nicotine
Secondary hypertension
secondary to other disease
-kidney disease, hyperthyroidism
Prevent hypertension
- lose weight
- limit alcohol
- exercise
- reduce salt intake (elderly)
- No smoking
- manage stress
