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Anatomy 2 Ch4

Arteries and veins and all that stuff

QuestionAnswer
Angiogenesis the growth of new blood vessels
Arteries carry blood from the heart to the tissues.
Arterioles are small arteries that connect to capillaries.
Capillaries are the site of substance exchange between the blood and body tissues.
Venules connect capillaries to larger veins.
Veins convey blood from the tissues back to the heart.
Vaso vasorumare small blood vessels that supply blood to the cells of the walls of the arteries and veins. (supply oxygen to the cells lining larger vessels
The functional properties of arteries are... elasticity and contractility.
Elasticity allows arteries to accept blood under great pressure from the contraction of the ventricles and to send it on through the system.
Contractility allows arteries to increase or decrease lumen size and to limit bleeding from wounds.
Do blood vessels relax? Blood vessels never relax, unless you’re dead. In vasodilation, they don’t contract as much
3 major layers of arteries. Tunica interna (intima), Tunica media, Tunica externa
Tunica interna (intima) endothelium, basement membrane, internal elastic lamina
Tunica media circular smooth muscle & elastic fibers
Tunica externa elastic & collagen fibers
Blood vessels only have _____response. sympathetic. Vascular smooth muscle is innervated by sympathetic nervous system
Sympathetic Innervation increase in stimulation causes muscle contraction or vasoconstriction: decreases diameter of vessel; decrease in stimulation or presence of certain chemicals causes vasodilation
cause vasodilation nitric oxide, K+, H+ and lactic acid
Elastic Arteries Large arteries w/more elastic fibers&less smooth muscle •Able to receive blood under pressure&propel it onward.•Called conducting arteries because they conduct blood from the heart to medium sized muscular arteries.•They function as a pressure reservoir.
Muscular Arteries Medium-sized arteries with more muscle than elastic fibers in tunica media•Capable of greater vasoconstriction and vasodilation to adjust rate of flow(walls are relatively thick–called distributing arteries because they direct blood flow)
Arterioles Small arteries delivering blood to capillaries•Metarterioles form branches into capillary bed
to bypass capillary bed... precapillary sphincters close & blood flows out of bed in thoroughfare channel
vasomotion is intermittent contraction & relaxation of sphincters that allow filling of capillary bed 5-10 times per minute
Post capillary sphincters don’t exist
Microcirculation Microscopic vessels that connect arterioles to venules•Found near every cell in body but more extensive in highly active tissue (muscles, liver, kidneys, & brain)•Capillary walls composed of a single layer of cells (endothelium) and a basement membrane
Continuous capillaries skeletal & smooth, connective tissue and lungs
Fenestrated capillaries kidneys, small intestine, ciliary process & endocrine glands
Sinusoids liver, bone marrow, & spleen
Holes in sinusoids for... liver and spleen is to take RBC out of circulation to break down ect
No capillaries in our joints because they’d be shredded. Also not in cornea because it would obstruct light
Venules Small veins collecting blood from capillaries•Tunica media contains only a few smooth muscle cells & scattered fibroblasts(porous endothelium allows WBC emigration)
Veins Same three tunics as arteries –thinner tunica interna and media and a thicker tunica externa–less elastic tissue and smooth muscle–thinner-walled than arteries–contain valves to prevent the backflow of blood
Vascular (venous) sinuses veins with very thin walls with no smooth muscle to alter their diameters. •Ex. coronary sinus of the heart
Veins have... Proportionally thinner walls than same diameter artery•Still adaptable to variationsin volume & pressure•Valves are thin folds of tunica interna designed to prevent backflow
Anastomoses Union of 2 or more arteries supplying the same body region–blockage of only one pathway has no effect
Collateral circulation Alternate route of blood flow through an anastomosis
end arteries Arteries that do not anastomose
Occlusion of an end artery .. interrupts the blood supply to a whole segment of an organ, producing necrosis (death) of that segment.
Blood Distribution 60% of blood volume at rest is in systemic veins and venules–functions as a blood reservoir
blood is diverted from reservoir in times of need increased muscular activityproduces venoconstriction•hemorrhage causes venoconstriction to help maintain blood pressure
Capillary Exchange Diffusion, Transcytosis, Bulk flow
Diffusion (most important method) Substances such as O2, CO2, glucose, amino acids, hormones, and others diffuse down their concentration gradients.–all plasma solutes except large proteins pass freely across
Transcytosis passage of material across endothelium in tiny vesicles by endocytosis and exocytosis (large, lipid-insoluble molecules such as insulin or maternal antibodies passing through placental circulation to fetus)
Bulk Flow Movement of large dissolved/suspended material in same direction–move in response to pressure•from area of high pressure to low–faster rate of movement than diffusion or osmosis•Most important for regulation of relative volumes of blood&interstitial fluid
Filtration movement of material into interstitial fluid•promoted by blood hydrostatic pressure & interstitial fluid osmotic pressure
Reabsorption movement from interstitial fluid into capillaries•promoted by blood colloid osmotic pressure
balance of hydrostatic,interstituial,blood colloid pressure... net filtration pressure
Net Filtration Pressure Whether fluids leave or enter capillaries depends on net balance of pressures–net outward pressure of 10 mm Hg at arterial end of a capillary bed–net inward pressure of 9 mm Hg at venous end of a capillary bed
About 85% of the filtered fluid is returned to the capillary– escaping fluid and plasma proteins are collected by lymphatic capillaries (3 liters/day)
Edema An abnormal increase in interstitial fluid if filtration exceeds reabsorption
result of excess filtration increased blood pressure (hypertension)•increased permeability of capillaries allows plasma proteins to escape
result of inadequate reabsorption decreased concentration of plasma proteins lowers blood colloid osmotic pressure
Filtration/reabsorption issue Often not noticeable until 30% above normal
Hemodynamics Cardiac output, blood volume, viscosity, resistance, and elasticity of arteries.
As blood leaves the aorta and flows through systemic circulation its pressure progressively falls to 0 mm Hg by the time it reaches the right atrium
Resistance refers to the opposition to blood flow as a result of friction between blood and the walls of the blood vessels.
Vascular resistance depends on the diameter of the blood vessel, blood viscosity, and total blood vessel length.
Systemic vascular resistance(also known as total peripheral resistance) all of the vascular resistances offered by systemic blood vessels; most resistance is in arterioles, capillaries, and venules due to their small diameters.
Blood Pressure Pressure exerted by blood on walls of a vessel –caused by contraction of the ventricles–highest in aorta (120/80)
with distance from left ventricle... Pressure falls steadily in systemic circulation
Pressure entering capillaries 35 mm Hg
Pressure entering the right atrium 0 mm Hg
If decrease in blood volume is over 10%... BP drops
Velocity of Blood Flow Speed of blood flow in cm/sec is inversely related to cross-sectional area–blood flow is slower in thearterial branches
Blood flow in aorta is 40 cm/sec
flow in capillaries is .1 cm/sec
Blood flow becomes faster when ... vessels merge to form veins
Circulation time is time it takes... a drop of blood to travel from right atrium back to right atrium
Venous Return Volume of blood flowing back to the heart from the systemic veins
Venous Return depends on... pressure difference from venules (16 mm Hg) to right atrium (0 mm Hg)–tricuspid valve leaky andbuildup of blood on venousside of circulation
Skeletal muscle pump– contraction of muscles & presence of valves
Respiratory pump– decreased thoracic pressure and increased abdominal pressure during inhalation, moves blood into thoracic veins and the right atrium
Resistance Friction between blood and the walls of vessels
Average blood vessel radius •smaller vessels offer more resistance to blood flow•cause moment to moment fluctuations in pressure
Total blood vessel length •the longer the vessel, the greater the resistance to flow•200 miles of blood vessels for every pound of fat
Systemic vascular resistance (SVR) blood vessel radius and length total–arterioles control BP by changing diameter
Role of cardiovascular center help regulate heart rate & stroke volume–specific neurons regulate blood vessel diameter
Cardiovascular center (CV) a group of neurons in the medulla that regulates heart rate, contractility, and blood vessel diameter.
CV overview input from higher brain regions&sensory receptors –output from CV flows along sympathetic ¶sympathetic fibers–Sympathetic impulses along cardioaccelerator nerves increase heart rate&contractility–Parasym impulses along vagus nerves decrease heartrate
The sympathetic division also continually... sends impulses to smooth muscle in blood vessel walls via vasomotor nerves. The result is a moderate state of tonic contraction or vasoconstriction, called vasomotor tone.
Syncope Fainting or a sudden, temporary loss of consciousness not due to trauma–due to cerebral ischemia or lack of blood flow to the brain
vasodepressor syncope = sudden emotional stress
situational syncope = pressure stress of coughing, defecation, or urination
drug-induced syncope = antihypertensives, diuretics, vasodilators and tranquilizers
orthostatic hypotension = decrease in BP upon standing
Chemoreceptor Reflexes Carotid bodies and aortic bodies
Carotid bodies and aortic bodies... detect changes in blood levels of O2, CO2, and H+ (hypoxia, hypercapnia or acidosis )–causes stimulation of CV–increases sympathetic stimulation to arterioles & veins–vasoconstriction and increase in blood pressure Also changes breathing rate
Renin-Angiotensin-Asldosterone System (RAAS) A decrease in BP or decreased blood flow to kidney results in a release of renin from kidney which results in the formation angiotensin II (AII)
AII a potent vasoconstrictor (↑ SVR), causes release of aldosterone
Aldosterone increases reabsorption of Na+ in the kidneys which increases H2O reabsorption
Epinephrine & norepinephrine Decreased BP results in a release of epinephrine and norepinephrine from the adrenal medulla–Increases heart rate & force of contraction–Causes vasoconstriction in skin & abdominal organs–Vasodilation in cardiac & skeletal muscle
ADH release from posterior pituitary causes vasoconstriction
Atrial natriuretic peptide(ANP) lowers BP; causes vasodilation & loss of salt and water in the urine
Autoregulation The ability of a tissue to automatically adjust its own blood flow to match its metabolic demand for supply of O2 and nutrients and removal of wastes is called.
Local factors cause changes in each capillary bed important for tissues that have major increases in activity (brain, cardiac & skeletal muscle)
Local changes in response to physical changes warming & decrease in vascular stretching promotes vasodilation
Vasoactive substances released from cells alter vessel diameter (K+, H+, lactic acid, nitric oxide); systemic vessels dilate in response to low levels of O2–pulmonary vessels constrict in response to low levels of O235
Hypovolemic shock due to loss of blood or body fluids (hemorrhage, sweating, diarrhea)–venous return to heart declines & output decreases
Cardiogenic shock caused by damage to pumping action of the heart (MI, ischemia, valve problems or arrhythmias)
Vascular shock causing drop inappropriate vasodilation -- anaphylatic shock, septic shock or neurogenic shock (head trauma)
Obstructive shock caused by blockage of circulation (pulmonary embolism)
Systemic circulation left side heart to body & back to heart
Hepatic Portal circulation capillaries of GI tract to capillaries in liver
Pulmonary circulation right-side heart to lungs & back to heart
Fetal circulation from fetal heart through umbilical cord to placenta & back
External carotid arteries supplies structures external to skull as branches of maxillary and superficial temporal branches
Internal carotid arteries (contribute to Circle of Willis)– supply eyeballs and parts of brain
Created by: Devtemrys
 

 



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