| Question | Answer |
| What carries oxygenated blood away from the heart; except for pulmonary circulation and umbilical vessels of a fetus? | Arteries |
| What contact tissue cells and directly serve cellular needs | Capillaries |
| What carry deoxygenated blood toward the heart ? | Veins |
| In Tunica intima,
Endothelium lines the lumen of all | vessels |
| In Tunica media,Smooth muscle and sheets of elastin.
Sympathetic vasomotor nerve fibers control | vasoconstriction and vasodilation of vessels |
| In Tunica externa ,Collagen fibers protect and reinforce
Larger vessels contain | vasa vasorum to nourish the external layer |
| These are large thick-walled arteries with elastin in all three tunics
Eg: Aorta and its major branches
Large lumen offers low-resistance
Act as pressure reservoirs—expand and recoil as blood is ejected from the heart | Elastic (Conducting) Arteries |
| Distal to elastic arteries; deliver blood to body organs
Have thick tunica media with more smooth muscle
Active in vasoconstriction | Muscular (Distributing) Arteries and Arterioles |
| Smallest arteries
Lead to capillary beds
Control flow into capillary beds via vasodilation and vasoconstriction | Arterioles |
| Microscopic blood vessels
Walls of thin tunica intima, one cell thick
Pericytes help stabilize their walls and control permeability | Capillaries |
| Abundant in the skin and muscles
Tight junctions connect endothelial cells
Intercellular clefts allow the passage of fluids and small solutes | Continuous Capillaries |
| The least permeable capilllary ? | Continuous capillaries of the brain |
| More permeable than continuous capillaries
Function in absorption or filtrate formation (small intestines, endocrine glands, and kidneys) | Fenestrated Capillaries |
| Fewer tight junctions, larger intercellular clefts, large lumens
Usually fenestrated
Allow large molecules and blood cells to pass between the blood and surrounding tissues
Found in the liver, bone marrow, spleen | Sinusoidal Capillaries |
| Interwoven networks of capillaries form the microcirculation between arterioles and | venules |
| What directly connects the terminal arteriole and a postcapillary venule | Vascular shunt |
| 10 to 100 exchange vessels per capillary bed
Branch off the metarteriole or terminal arteriole | True capillaries |
| Regulated by local chemical conditions and | vasomotor nerves |
| Precapillary sphincters regulate blood flow into | true capillaries |
| Formed when capillary beds unite
Very porous; allow fluids and WBCs into tissues | Venules |
| Formed when venules converge
Have thinner walls, larger lumens compared with corresponding arteries | veins |
| veins Blood pressure is lower than in | arteries |
| veins have a _____________ ___________ which consist of collagen fibers and elastic networks | Thin tunica media and a thick tunica externa |
| veins contain | 65% of blood supply |
| Adaptations that ensure return of blood to the heart
Large-diameter lumens offer little resistance
Valves prevent backflow of blood
Most abundant in veins of the limbs | veins |
| Venous sinuses | flattened veins with extremely thin walls |
| Force per unit area exerted on the wall of a blood vessel by the blood | Blood pressure (BP) |
| Resistance (peripheral resistance) | Opposition to flow
Measure of the amount of friction blood encounters |
| Three important sources of resistance | Blood viscosity
Total blood vessel length.
Blood vessel diameter |
| The “thickness” of the blood due to formed elements and plasma proteins | Blood viscosity |
| The longer the vessel, the greater the resistance encountered | Blood vessel length |
| Small-diameter arterioles are the major determinants of | peripheral resistance |
| Abrupt changes in diameter or fatty plaques from atherosclerosis dramatically increase resistance
Disrupt laminar flow and cause turbulence
Resulting in a | bruit |
| Blood flow (F) is directly proportional to the blood (hydrostatic) pressure gradient (P)
If P increases, | blood flow speeds up |
| Blood flow is inversely proportional to peripheral resistance (R)
If R increases, blood flow | decreases |
| Is highest in the aorta
Declines throughout the pathway
Is 0 mm Hg in the right atrium | Systemic pressure |
| pressure exerted during ventricular contraction | Systolic pressure |
| lowest level of arterial pressure | Diastolic pressure |
| difference between systolic and diastolic pressure | Pulse pressure |
| pressure changes created during breathing move blood toward the heart by squeezing abdominal veins as thoracic veins expand | Respiratory “pump”: |
| contraction of skeletal muscles “milk” blood toward the heart and valves prevent backflow | Muscular “pump” |
| The main factors influencing blood pressure: | Cardiac output (CO)
Peripheral resistance (PR)
Blood volume |
| cardiac output isDetermined by venous return and | neural and hormonal controls |
| Resting heart rate is maintained by the cardioinhibitory center via the | parasympathetic vagus nerves |
| neural and hormonal controls
Counteract fluctuations in blood pressure by altering peripheral resistance | short term blood pressure |
| renal regulation
Counteracts fluctuations in blood pressure by altering blood volume | Long-term blood pressure |
| A cluster of sympathetic neurons in the medulla that oversee changes in blood vessel diameter
Maintains vasomotor tone (moderate constriction of arterioles)
Receives inputs from baroreceptors, chemoreceptors, and higher brain centers | Vasomotor center |
| Baroreceptors taking part in the carotid sinus reflex | protect the blood supply to the brain |
| Baroreceptors taking part in the aortic reflex help maintain | adequate blood pressure in the systemic circuit |
| Chemoreceptors respond to rise in CO2, drop in | pH or O2 |
| Adrenal medulla hormones norepinephrine (NE) and epinephrine cause generalized | vasoconstriction and increase cardiac output |
| generated by kidney release of renin, causes vasoconstriction | Angiotensin II |
| what causes blood volume and blood pressure to decline, causes generalized vasodilation. Lower BP | ANP + BNP |
| A in arterial bp | release of renin |
| Renin produces the production of | angiotensin II |
| Angiotensin II is a potent | vasoconstrictor |
