What is the central blood containing space surrounded by the tunics?
What are Capillaries composed of?
Endothelium with sparse basal lamina.
What is the Tunica Interna (Intima)?
Endothelial layer that lines the lumen of all vessels.
What is the Tunica Media?
Smooth muscle and elastic fiber layer, regulated by sympathetic nervous system.
What does the Tunica Media control?
Vasoconstriction/vasodilation of vessels.
What is the Tunica Externa (Adventitia)?
Collagen fibers that protect and reinforce vessels.
What is the Vasa Vasorum?
Vessels of the vessels - larger veseels contain this. Nourish the external tissues of the blood vessel wall.
What are Elastic (Conducting) Arteries?
Thick walled arteries near the heart. Aorta and its major branches. Large lumen allow low-resistance conduction of blood. Contain elasin in all three tunics. Act as pressure reservoirs - expand and recoil as blood is ejected from the heart.
What are Muscular (Distributing) Arteries?
Distal to elastic arteries, deliver blood to body organs, have thick tunica media with more smooth muscle, active in vasoconstruction.
What are Arterioles?
Small arteries, lead to capillary beds, control flow into capillary beds via vasodilation and vasoconstriction.
What are Capillaries?
Microscopic blood vessels, walls of thin tunica intima, one cell thick. Size only allows one RBC at a time.
Where are Capillaries found?
In all tissues except for cartilage, epithelia, cornea and lens of eye.
What is the funciton of Capillaries?
Exchange of gases, nutrients, wastes, hormones etc.
Abundent capillaries in the skin and muscles, continuous capillaries of the brain - forms the blood brain barrier.
What is Fenestrated Capillaries?
Some endothelial cells contain pores (fenestrations), more permeable then continuous capillaries. Functions in absorption or filtrate formation (small intestines, endocrine glands, and kidneys).
What are Sinusoidal 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, and spleen.
What are Venules?
Formed when capillary beds unite. Allow fluids and WBC's to pass from the bloodstream to tissues. Large ones have one or two layers of smooth muscle (tunica media).
What are Postcapillary Venules?
Smallest venules, composed of endothelium and a few pericytes.
What are Veins?
Formed when venules converge. Composed of three tunics.
What are Capacitance Vessels?
Blood reservoirs that contain 65% of the blood supply.
Do veins or arteries have lower blood pressure and thinner walls?
What are the special adaptations veins have in returning blood to the heart?
Large-diameter lumes, which offer little resistance to flow. Valves (resembling semilunar heart valves), which prevent backflow of blood.
What is Venous Sinuses?
Specialized, flattened veins with extremely thin walls (e.g., coronary sinus of the heart dural sinuses of the brain).
What are Vascular Anastomoses?
Merging blood vessels, more common in veins than arteries. Provdes alternate pathways (collateral channels) for blood to reach a given body region. If one branch is blocked, the collateral channel can supply the area with adequate blood supply.
What is Resistance?
Opposition to floow. Measures of the amount of friction blood encounters. Referred to as peripheral resistance (PR).
What are the three important sources of resistance?
Blood viscosity, total blood vessel length, blood vessel diameter.
What factors remain relatively constant in resistance?
Blood viscosity, and blood vessel length.
What is Blood Viscosity?
The stickiness of the blood due to formed elements and plasma proteins.
What is Blood Vessel Lenght?
The longer the vessel, the greater the resistance encountered.
What are the major determinants of Peripheral Resistance?
What does Atherosclerosis effect?
Increases resistance and disrupts blood flow to cause turbulence.
What is directly proportional to Blood Flow (F)?
Blood hydrostatic pressure gradient. - If P increases, BF speeds up.
What is Blood Flow inversely proportional with?
Peripheral Resistance (R). - If R increases, blood flow decreases.
What is Resistance more important in influencing local blood flow?
It is easily changed by altering blood vessel diameter.
What is Systemic Blood Pressure?
Blood flow caused by the pumping action of the heart, pressure results when flow is opposed by resistance.
Where is Systemic Pressure highest?
In the Aorta.
Where does Systemic Pressure decline?
Throughout the pathway.
What is Systemic Pressure in the right atrium?
What is Arterial Blood Pressure?
Reflects two factors of the arteries close to the heart. The elasticity (compliance or distensibility), and the amount of blood forced into them at any given time.
What is Systolic Pressure?
Pressure exerted on arterial walls during ventricular contraction.
What is Diastolic Pressure?
Lowest level of arterial pressure.
What is Mean Arterial Pressure?
(MAP), Pressure that propels the blood to the tissues (average blood pressure in an individual).
What factors aid in venous return?
Respiratory pump, muscular pump and vasconstriction of veins under sympathetic control.
What is the Respiratory Pump?
Pressure changes created during breathing move blood towards the heart by squeezing abdominal veins as thoracic veins expand.
What is the Muscular Pump?
Contraction of skeletal muscles "milk" blood toward the heart and valves prevent backflow.
What is Short Term control of blood pressure?
Neural and hormonal controls - counteract functuations in blood pressure by altering peripheral resistance.
What are the Adrenal Medulla Hormones?
Norepinephrine and Epinephrine increase blood pressure - cause vasoconstriction and increase cardiac output.
What is Antidiuretic Hormone?
ADH, (Vasopressin) - Causes intense vasoconstriction in cases of extremely low BP. Increases BP.
What is Angiotensin II?
Kidney release of renin generates angiotensis II, which causes vasoconstriction. Increase BP.
What is Atrial Natriuretic Peptide?
ANP - Causes blood volume and pressure to decline (produced by atria of the heart0.
What is Nitric Oxide?
NO - is a brief but potent vasodilator. Decrease BP.
What is Inflammatory Chemical?
EX - Histamine - vasodilator, decreases BP.
What is Alcohol?
Causes BP to drop by inhibiting ADH.
What are Vital Signs?
Pulse and blood pressure, along with respiratory rate and body temperature.
What is Pulse?
Pressure wave caused by the expansion and recoil of elastic arteries. Varies with health, body position, and activity.
What is routinely used to take pulse?
What is Systolic Pressure?
First sound heart measuring blood pressure, normally 110 - 140 mm Hg.
What is Diastolic Pressure?
When sound disappears is recoreded, usually 70 - 80 mm Hg.
What is Hypothension?
Low blood pressure, systolic pressure below 100 mg Hg. Often associated with long life and lack of cardiovascular illness.
What is Orthostatic Hypothension?
Temporary low BP and dizziness when suddenly rising from a sitting or reclining position.
What is Chronic Hypotension?
Hint of poor nutrition and warning sign for Addision's disease (adrenal isnsufficiency) or hypothyroidism.
What is Acute Hypotension?
Important sign of circulatory shock.
What is Hypertension?
High blood pressure, sustained elevated arterial pressure of 140/90 or higher. May be transient adaptations during fever, physical exertion, and emotional upset. Often persistent in obese people.
What is Autoregulation?
Automatic adjustment of blood flow to each tissue in proportion to its requirements at any given point in time.
What is Angiogenesis?
Occurs when short term autoregulation cannot meet tissue nutrient requirements. Either the number of vessels to a region increases or existing vessels enlarge.
When is Angiogenesis common in the heart?
A coronary vessel is occluded, throughout the body in people in high-altitude areas.
What is Circulatory Shock?
Any condition in which blood vessels are inadequately filled, or blood cannot circulate normally. Results in inadequate blood flow to meet tissue needs.