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Blood vessels contain 3 layers
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Tunica interna is in direct contact with
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--- SP Blood Vessel
Exam #2
| Question | Answer |
|---|---|
| Blood vessels contain 3 layers | 1. Tunica externa 2. Tunica media 3. Tunica interna |
| Tunica interna is in direct contact with | blood flow |
| lumen | opening |
| Elastic or conducting arteries are found | closest to the heart |
| Capillaries usually connect | arterioles and venules |
| Capillaries branch to form | extensive networks |
| Flow of blood through a network is regulated by | smooth muscle |
| CAPILLARY EXCHANGE | KNOW THE U-SHAPED TUBE AND WHAT GOES ON - LOOK AT NOTES |
| Elastic or conducting arteries are found | closest to the heart |
| Capillaries usually connect | arterioles and venules |
| Capillaries branch to form | extensive networks |
| Flow of blood through a network is regulated by | smooth muscle |
| CAPILLARY EXCHANGE | KNOW THE U-SHAPED TUBE AND WHAT GOES ON - LOOK AT NOTES |
| Vein shape and thickness compared to arteries | Thinner : farther away from the heart. Cannot maintain shape, sometimes collapses |
| Venules drain | capillary blood and return blood to the heart |
| Smallest venules are located | closest to the capillaries |
| Venules have __ junctions | loosely organized junctions |
| Venules function as the site for | exchange of nutrients, wastes, movement of white blood cells from bloodstream -> inflammed/infected tissue |
| As venules grow larger | their walls thicken and lose the ability to exchange with interstitial fluid |
| Venules are | group of capillaries within a tissue that reunite to form small vessels |
| Veins are | blood vessels that carry blood from tissue back to the heart |
| Vein ratio of wall thickness to diameter | wall thickness |
| Tunica interna is made up of two layers | 1. endothelium (inner) 2. interal elastic lamina (outside) |
| Endothelium of interna lines the | inner surface of cardiovascular, influences blood flow, secreting chemical mediators that affect vessel contraction, capillary permeability |
| Internal elastic lamina function | facilitates diffusion through tunica interna to media |
| Internal elastic lamina looks like | swiss cheese |
| Endothelium of interna is composed of which cells | simple squaimous |
| Deep inside the endothelium of the interna is the __ membrane | basement |
| basememnt membrane function | anchors endothelium to tissue, supports base for tensile strength and resilience for stretch + recoil |
| Tunica media description and composed of | thick layer, composed of smooth muscle cells/elastic fibers. |
| Where are smooth muscle cells found in the 3 layers | tunica media |
| Primary function of smooth muscle cells | encircles lumen like ring on finger, regulates diameter of lumen |
| The regulation of the diameter of lumen is important for influencing | blood flow and pressure |
| Tunica externa composed of | elastic/collagen fibers |
| External Elastic Lamina function | separates the tunica externa from tunica media, anchors vessel to surrounding tissues |
| External externa contains | nerves that supply tissue of vessel walls |
| Arteries carry blood | away from the heart |
| What layer is significantly different in arteries | tunica media |
| What supplies smooth muscle of arteries | sympathetic ganglionic axons of ANS |
| An increase in ANS stimulation -> | contraction of smooth muscle of arteries |
| A contraction has what affect on the lumen | narrowing of lumen and squeezing the arterial wall |
| Vasoconstriction | Decrease in diameter of the lumen |
| A decrease in ANS stimulation -> | relaxation of smooth muscle of arteries |
| A relaxation has what affect on the lumen | Lumen is more open and no pressure on arterial wall |
| Vasodilation | Increase in diameter of the lumen |
| Vasospasm occurs when | an artery or arteriole is damaged |
| Vasospasm limits | blood flow through the damaged vessel wall and helps reduce blood loss if the vessel is small |
| Elastic arteries are the | largest diameter arteries in the body |
| How are elastic arteries characterized | thick tunica media dominated by elastic fibers |
| Elastic artery function | propel blood onward while the ventricles are relaxing |
| As blood is ejected from heart into elastic arteries, their walls | stretch easily to accommodate the pressure from the blood |
| Pressure reservoir | As elastic fibers stretch, they momentarily store mechanical energy |
| How do elastic articles propel blood and when | When ventricles are relaxed, the arteries recoil |
| Elastic arteries are also called ___ because | conducting arteries, because they conduct blood from heart to muscular arteries |
| muscular arteries are (size-wise) | medium-sized |
| Tunica media of muscular arteries contain | more smooth muscle and fewer elastic fibers (which makes their walls really thick) |
| Because the tunica media of muscular arteries is thick | it is capable of greater vasoconstriction + vasodilation |
| Elastic artery wall compared to diameter | 10% of vessel's total diameter AA |
| Muscular artery wall compared to diamter | 25% of vessel's total diameter AA |
| Muscular arteries are also called ___ because | distributing arteries because they distribute blood to organs |
| Anastamoses is a | Union of branches of two or more ARTERIES that supply the same body region |
| Anastomoses provide | alternative routes for blood to reach a tissue or organ |
| Collateral circulation | the alternative circulatory route of blood flow to a body part through anastomoses |
| Arteries that do not anastomoses are called | end arteries |
| Obstruction of an end artery leads to | necrosis of that segment |
| necrosis | death |
| Arterioles | Small arteries |
| Elastic arteries -> | muscular arteries - > arterioles -> capillaries |
| Conducting arteries -> | distributing arteries -> arterioles -> capillaries |
| Size of arterioles | microscopic |
| Function of arterioles | Regulates the flow of blood into capillary networks (which conntrols SVR since it regulates diameter) |
| Terminal end of arteriole is called | metartieriole |
| Metarterioles narrow towards | capillary junctions |
| What happens at metarteriole-capillary junction | the muscle cell farthest away forms the precapillary sphincter |
| precapillary sphincter function | monitors the blood flow into the capillary |
| What layer of the arteriole contains the sympathetic nerves | Externa |
| Key role of arterioles | Regulates blood flow from arteries to capillaries by regulating resistance |
| Resistance | opposition to blood flow |
| Resistance is mainly due to | the friction that occurs between blood + inner walls of blood vessel |
| The smaller the blood vessel, the ___ the resistance | the greater |
| Contraction -> vaso____ -> ? resistance -> ? blood flow | constriction, higher, lower |
| Relaxation -> vaso____ -> ? resistance -> ? blood flow | lower, higher |
| Vasoconstriction causes ? blood pressure | higher |
| Vasodilation causes ? blood pressure | lower |
| Capillaries are | the smallest of blood vessels |
| Capillary connect | arterial outflow from heart to venous return |
| Primary function of capillary | exchange of substances between blood and interstitial fluid |
| Tissues with lower metabollic activity | contain fewer capillaries |
| Capillaries are absent in | cornea, lens, and cartilage |
| Capillaries lack the layers | tunica media and tunica externa |
| capillary walls are composed | 1 layer of endothelial cells and a basement membrane |
| Exchange of materials occur ONLY | through walls of capillaries and beginning of venules |
| Exchange cannot happen anywhere else because | their layers are too thick |
| Capillary bed | a network of 10-100 capillaries that arise from a single metarteriole |
| Blood can flow through capillary network from an arteriole into a venule by | 1. capillaries 2. thoroughfare channel |
| 1. Capillary flow | blood -> arteriole -> capillary -> venules |
| Junction present in between metaarteriole and capillaries are | precapillary sphincters |
| When precapillary sphincters are relaxed | blood flows into capillaries |
| when precapillary sphincters are contracted | blood flow is decreased or stopped |
| 2. Thoroughfare channel | Provides direct route for blood to go from arteriole to venule BYPASSES capillary |
| Autoregulation | The ability of a tissue to automatically adjust its blood flow to meet metabollic demands |
| Three types of capillaries | 1. Continuous 2. Fennestrated 3. Sinusoids |
| Continuous capillaries | Endothelial cells, separated only by intercellular clefts. |
| Intercellular clefts prevent | substances from diffusing |
| Intercellular clefts are found | in the brain |
| Blood brain barrier contains | continuous capillaries |
| Fenestrated capillaries contain | many small holes |
| holes of fenestrated capillaries allow | greater exchange of materials |
| Fenestrated capillaries are found in | kidneys, where filtration occurs |
| Sinusoids contain | large holes, incomplete/absent membrane and large intercellular clefts |
| Large holes of sinusoids | are so leaky that large molecules and blood cells can pass through as well |
| Portal system | Blood passes from one capillary network to another through a vein |
| Mission of the entire cardiovascular system is | to keep blood flowing through capillaries and allow capillary exchange |
| At any given time ___% of blood is continually exchanging materials | 7% |
| Most capillary exchange occur through the process of | simple diffusion |
| Water-soluble substances diffuse across capillary walls through | intercellular clefts or fenestrations |
| Lipid soluble substances diffuse through | lipid bi-layer |
| What cannot pass through capillary walls of continuous and fenestrated | plasma proteins, red blood cells |
| Transcytosis | When substances are enclosed in pinocytic vessicles that first enter via endocytosis, then move across the cell and exit on other side via exocytosis |
| Transcytosis is mainly for substances that | are large, lipid-soluble or other substances that cannot cross capillary wall |
| Whether fluid leaves or enters the cell depends on | balance of pressure |
| filtration | when pressure that push fluid out of capillary exceeds the pull of fluid into capillary |
| reabsorbtion | when pressure that pulls fluid into capillary exceeds fluid that pushes fluid out of capillary |
| vein layers compared to arteries | tunica interna and tunica media are much thinner |
| Veins lack | external and internal elastic laminae |
| Because veins lack external and internal elastic laminae | they can stretch, but are not structured to withstand high pressure |
| Lumen of vein compared to artery | larger |
| Why do veins look flat | very thin walls |
| Average blood pressure in veins compared to arteries | considerably lower |
| Speed of blood flow in veins | slow, steady |
| Speed of blood flow in arteries | rapid |
| What do veins contain that arteries do not | valves |
| Valves are | Thin folds of tunica interna that form flaplike cusps |
| Valve function | prevents backflow of blood |
| The low blood pressure of veins allows blood flow to be | slow, and tend to try to back up |
| Venous sinus | vein within endothelium wall that has no smooth muscle to alter its diameter |
| What is replaced in venous sinus | surrounding dense connective tissue replaces tunica media and tunica externa in providing protection |
| Venous return | the volume of blood that flows back into the heart via systemic veins |
| Venous return is generally assisted by | contraction of heart muscle |
| Blood pressure is measured in | mm Hg |
| Venous sinus quoted in notes | flattened veins with thin walls (only endothelium) |
| problems with venous return | pressure pushing blood up is barely enough to overcome gravity |
| Two mechanisms that assist venous return | 1. skeletal muscle pump 2. respiratory pump |
| Skeletal muscle pump steps. | 1. At rest- valves are open 2. Contraction of muscles- milking 3. Relaxation of muscles- valves closer to heart close, farther from heart opens because pressure in foot is higher than in leg |
| Respiratory pump | 1. Inhaling- abdominal veins compressed, blood moves from abdominal into thoracic veins into atria. 2. exhalation- valves prevent backflow of blood from thoracic into abdominal |
| Largest portion of your blood is | at rest |
| Largest portion of your blood is located | in systemic veins and venules |
| Systemic arteries hold about __% of blood | 13% of blood |
| pulmonary blood vessels hold about _% of blood | 9% |
| Capillaries hold about _% of blood | 7 |
| heart chamber holds about _% of blood | 7 |
| because systemic veins and venules contain a large % of blood volume they function as | blood reservoirs |
| blood from blood reservoirs can be | diverted quickly if needed |
| Principal blood reservoirs are the veins of | abdominal organs, and skin |
| Blood flow is | the volume blood that flows through any tissue in a given time |
| Blood flow is measured in | mL/min |
| Total blood flow is equal to | cardiac output |
| Cardiac output is | the volume of blood that circulates through blood vessels each minute |
| Cardiac output depends on | heart rate and stroke volume |
| How cardiac output is distributed depends on 2 factors | 1. pressure difference that drives blood flow into tissue 2. resistance to blood flow |
| Blood flows from ___ to ___, meaning that the greater the pressure difference, ___ | higher, lower the greater the blood flow |
| Blood pressure | pressure exerted by blood on walls of blood vessel |
| Blood pressure is generated by the contraction of | ventricles |
| Blood pressure is HIGHEST in | aorta and large systemic arteries |
| Average blood pressure | 120/80 |
| what are the numbers 120/80 stand for | 120 = systole 80 = diastole |
| Systolic blood pressure is | the highest blood pressure attained in arteries during systole |
| diastolic blood pressure is | the lowest arterial blood pressure attained during diastole |
| resistance is frequently referred to as | peripheral resistance |
| blood viscosity | thickness of blood, stickiness |
| As distance increases between the heart and blood vessel, the blood pressure becomes | lower |
| Total blood less than 5 L tend to | lower blood pressure |
| Total blood more than 5L tend to | increase blood pressure |
| Vascular resistance | opposition of blood flow due to friction between blood and the wall |
| Vascular resistance depends on 3 things | 1. Size of lumen 2. Blood viscosity 3. Total blood vessel length |
| 1. Size of lumen | The smaller the size of the lumen, the greater the resistance is to blood flow |
| 2. Blood viscosity | The higher the blood viscosity, the higher resistance |
| Blood viscosity is the ratio of | red blood cells to plasma |
| Conditions that increases blood viscosity | dehydration and polycythemia |
| Conditions that decrease blood viscosity | loss of plasma proteins, anemia, hemmorrhage |
| 3. Total blood vessel length | Resistance to blood flow length is directly proportional to length of blood vessel |
| Systemic vascular resistance is also known as | total peripheral resistance |
| systemic vascular resistance refers to | all vascular resistances offered by systemic blood vessels |
| Resistance in large blood vessels compared to small blood vessels | smaller |
| Cardiovascular center is located in the | medulla oblongata |
| Cardiovascular center helps regulate | heart rate and stroke volume |
| Cardiovascular center controls | neural and hormonal negative feedback systems that regulate blood flow to specific tissues |
| Cardiovascular center receives input from both | higher brain regions and sensory receptors |
| Nerve impulses descend from ____ in order to | cerebral cortex, limbic system, and hypothalamus affect the cardiovascular center |
| Three main types of sensory receptors that provide input to the cardiovascular center are | 1. proprioceptors 2. baroreceptors 3. chemoreceptors |
| Proprioceptors monitor | movements of joints and muscles |
| Proprioreceptors send impulse to cardiovascular center during | physical activity |
| Proprioreceptors input to the cardiovascular center accounts for | rapid increase in heart rate (exercise) |
| barroreceptors monitor | changes in pressure and stretch in walls of blood vessels |
| chemoreceptors monitor | concentration of various chemicals in blood |
| Output from the cardiovascular center flows along | sympathetic and parasympathetic neurons of ANS |
| Opposing sympathetic and parasympathetic function | influences control of the heart |
| Output from cardiovascular center sends impulses to | smooth muscle in blood vessel wall through the body via vasomotor nerves |
| vasomotor nerves | how output from cardiovascular center sends impulses to smooth muscle in blood vessel wall |
| vasomotor tone | moderate state of vasoconstriction due to impulse from cardiovascular center to smooth muscle in blood vessel wall |
| Sympathetic stimulation of most veins result in | constriction and movement of blood out of venous blood resevoirs |
| Nervous system regulates blood pressure via two types of reflexes | 1. baroreceptor reflex 2. chemoreceptor reflex |
| baroreceptor reflex are located in | the aorta, carotid, and large arteries |
| When blood pressure falls, the baroreceptors send | are stretched less and send impulses at slower rate, which results in decrease in parasympathetic stimulation |
| When increase in blood pressure, baroreceptors send | send impulses at faster rate, and increases parasympathetic stimulation |
| Chemoreceptor reflexes are located | close to baroreceptors in structures called carotid bodies and aortic bodies |
| Examples of what chemoreceptors would detect | hypoxia acidosis hypercapnia |
| hypoxia | low O2 |
| acidosis | increase in H+ |
| hypercapnia | excess CO2 |
| Hormones that regulate blood pressure | 1. renin-angiotensin-aldosterone system 2. epinephrine and norepinephrine 3. ADH 4. atrial natriuretic peptide |
| Renin-angiotensin-aldosterone system detects when | blood volume to the kidneys is low |
| Renin-angiotensin-aldosterone system steps | 1. renin + angiotensin-converting enzyme -> angiotensin II |
| angiotensin II ____ blood pressure | raises by 1. causing vasoconstriction 2. secretes aldosterone |
| aldosterone function | reabsorbs Na and water |
| Epinephrine and norepinephrine affect on blood pressure | increase rate and force of heart contractions, vasodilate arteries in skeletal muscle to increase blood flow |
| ADH affect on blood pressure | prevents dehydration and decreased blood volume, vasoconstricts. |
| Atrial natriuretic peptide affect on blood pressure | lowers blood pressure by causing vasodilation and promoting the loss of salt and water in urine |
| ADH and atrial natriuretic peptides are | OPPOSITE EFFECTS |
| Pulse | Traveling pressure wave |
| How is pulse created | the alternate expansion and recoil of elastic arteries after each contraction of the left ventricle |
| Pulse is strongest in | the arteries closest to the heart |
| Pulse is weakest in | arterioles |
| Pulse disappears in | capillaries |
| Pulse may be felt in | any artery that lies near the surface of the body |
| Common pulse points are | 1. Superficial temporal artery 2. Facial artery 3. Common carotid artery 4. brachial artery 5. Radial artery 6. Femoral artery 7. Popliteal artery 8. Dorsal artery |
| Pulse is generally the same as | heart rate |
| Normal pulse is | 70-80 bpm |
| Tachycardia | rapid resting heart rate that is 100+ bpm |
| Bradycardia | slow resting heart rate that is less than 50 bpm |
| Blood pressure is measured by a device called | sphygmomanometer |
| sphygmomanometer consists of | rubber cuff connected to a rubber bulb that is used to inflate the cuff and a meter used to register the pressure in the cuff |
| Process of taking blood pressure | 1. Inflating enough pressure to close the artery 2. First sound that is hurt is when the artery is opened enough to allow blood to flow through (systolic pressure) 3. when the sound stops it is called diastolic pressure |
| The sounds heard while taking blood pressure is called | Korotkoff sounds |
| Pulse pressure is the difference between | systolic and diastolic pressure |
| Pulse pressure value is normally | 40 mm Hg |
| atherosclerosis | condition that greatly increases pulse pressure |
| Circulatory routes | routes that the body is organized to carry blood to specific organs |
| The two main circulatory routes are | pulmonary and systemic |
| colloid pressure | pressure that pulls fluid into capillary |
| capillary blood pressure | pressure that pushes out of the capillary |
| Cardiovascular center sends impulses to smooth muscle via | vasomotor nerves |
| baroreceptors located in | aorta |
| chemoreceptors located in | carotid bodies next to baroreceptors |
| blood pressure is clinically defined as pressure that | is exerted in the left ventricle during systole and pressure remaining in arteries during diastole |
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