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organs of the cardiovascular system that form a closed circuit of tubes that carries blood from the heart to the body cells and back again. They are arteries, arterioles, capillaries, venules, and veins.
Strong, elastic vessels that carry blood away from the heart, under high pressure. They are the largest of the vessels. They have the greatest amount of smooth muscle in their walls.
3 Artery tunics
Tunica interna (intima) - innermost - composed of simple squamous epithelium called endothelium - epithelial tissue lines the inside of hollow organs.
Tunica media - middle layer. This layer is much thicker in arteries than in veins. Smooth muscle
Tunica externa (adventitia) - outermost layer - fibrous connective tissue. Cells supply vessels their nutrients.
Both arteries and veins have these 3 layers
provides smooth surface that allows blood cells and platelets to flow without being damaged. Helps prevent blood clotting by secreting biochemicals that inhibit platelet aggregation. May also help regulate blood flow by secreting substances that either dilate or constrict blood vessels, like nitric oxide.
Middle tunic layer of artery. The bulk of the arterial wall. Includes smooth muscle fibers and a thick layer of elastic connective tissue that gives the vessel a tough elasticity to withstand force of blood pressure and can stretch to accommodate the sudden increase in blood volume.
Adventitia. Thin outer layer of artery. Chiefly consists of connective tissue with irregular elastic and collagenous fibers. Attaches artery to the surrounding tissues. Also contains minute vessels (vasa vasorum) that give rise to capillaries and provide blood to the more external cells of the artery wall.
smaller branches of arterioles that join with capillaries
Sometimes, they join with venules and bypass capillaries.
smallest diameter blood vessel. Connect the smallest arterioles and smallest venules. They have a single layer of epithelial cells. Walls are semipermeable, and substances in blood are exchanged for substances in the tissue fluid surrounding the cells.
Provide the vital function of exchanging gases, nutrients and metabolic by-products between blood and tissue fluid.
Walls of capillaries have slits as openings. The largest of the openings are of the liver, spleen, and red bone marrow.
formed by muscles - they may close a capillary by contracting or open it by relaxing. Responds to the demands of the cells the capillary supplies. Rings of smooth muscle that control the flow of blood into capillaries.
Most important means of transfer. Substances soluble in lipid (oxygen, CO2, fatty acids) can diffuse through most areas of the cell membranes that make up the capillary wall because the membranes are largely lipid.
Lipid-insoluble substance - H2O, Na ions, and Cl ions, diffuse through pores in the cell membranes into the capillary wall.
Colloid osmotic pressure
plasma proteins trapped in the capillaries create an osmotic pressure that draws water into the capillaries.
Close-ended vessels that collect the excess fluid and return it through lymphatic vessels to the venous circulation.
becoming swollen and painful. Caused by too much fluid to leak out of capillaries to overwhelm lymphatic drainage.
carry blood back to the atria. Also function as blood reservoirs, useful in times of blood loss. Venous constriction help maintain blood pressure by returning more blood to the heart - seen in hemorrhaging. They have larger blood reservoirs.
Interior leaf Valves
Veins have semilunar vavles which project inward from their linings. 2 leaflets pushed closed is blood begins to back up in a vein. Aid in returning blood to the heart. Prevent backflow in veins. Not in arteries. Blood under high pressure from the beat of the heart, is pushed in 1 direction. Pressure diminishes at the ends of capillary beds, so veins have valves to prevent backflow.
Lowest pressure in arteries achieved when ventricles relax. Pressure in walls drops.
Deposits of fatty material form in the intima and inner lining of the arterial walls making the lumen much smaller
the fatty deposits that protrude into the lumens of the vessels and interfere with blood flow.
Alternate expanding and recoiling of the arterial wall - felt in an artery close to the surface. Best place is the left brachial artery.
Artery point used to take a radial pulse. Equal to the rate at which the left ventricle contracts and can be used to determine heart rate.
volume of blood that enters the arterial system. Average is 70mm. It is the difference b/w end-diastolic volume (EDV) and end-systolic volume (ESV).
Volume discharged from the ventricle per minute - calculated by taking stroke volume x heart rate. 70mm x 72bpg = 5040 mL/minute. Limited by the amount of blood returning to the ventricles.
the sum of the formed elements and plasma volumes in the vascular system. Usually 5L or 8% of body weight in kilograms. A hemorrhage my reduce blood volume, blood pressure drops. Transfusion may reestablish normal pressure. Volume can also fall if fluid balance is upset. Microgravity in outerspace.
a physical property that derives from the ease with which its molecules flow past one another. The greater the viscosity, the greater the resistance to flow. Can be increased by blood cells and plasma proteins. Greater force is needed to move it, so blood pressure rises. Anemia may decrease viscosity and lower blood pressure. Excess rbc's increase viscosity and increase blood pressure.
of the medulla oblongata - sends sympathetic impulses - helps maintain normal blood pressure. Control of vasoconstriction and vasodilation.
Venous blood flow
Pressure in venular ends of capillaries, so other factors like skeletal muscle contraction and breathing movements, comes into play. Blood is squeezed out of the abdominal veins and forced into thoracic veins. Venoconstriction helps to maintain blood pressure by forcing blood out of the venous blood reservoir.
opposite of each cusp is a swelling in the aortic wall - 2 of the sinuses give rise to the coronary arteries that feed the heart blood supply.
supplies blood to the tissues of the upper limb and head. gives rise to the right common carotid
portion of the descending aorta branches off bronchial, pericardial, and esophageal arteries. Other branches are the mediastinal arteries and posterior intercostal arteries.
give rise to gastric, splenic and hepatic arteries. Supply the digestive tract, the spleen, the liver.
Female - paired with ovarian arteries - supply the ovaries.
Men - spermatic arteries. Pass through the inguinal canal to supply the testes.
Common iliac arteries
supply blood to lower regions of the abdominal wall, pelvic organs and lower extremities.
Rise from subclavian arteries in base of neck. Supply vertebrae, their ligaments and muscles.
enlargement near each internal carotid artery. Contain baroreceptors that control blood pressure.
Flow and order of vessels
Arteries - next largest in diameter
arterioles - get smaller and smaller
Capillary bed - vessels that have 1 cell thick walls. Lumen is really small, so rbc's have to squish to get through. Exchange of wastes and respiratory gases depends on diffusion. Location is from the sphincter to the post-capillary venules.
Precapillary sphincter - ring that may close or open a capillary.
Precapillary arterioles - smallest of the artery vessels
veins - empty to the superior and inferior vena cavae into the rt. atrium
Nail bed test
The nail bed is all capillary bed and it should be pinkish. when pressing it, it will turn white. When let go, it should return to the pink color. It's a quick idea of how circulation is working.
Arterial blood flow
Due to contraction of the heart. Flow is directed by physical hydrostatic pressure.
Palpation of heart beat that can be felt at carotid artery, brachial artery, the radial pulse (normal place), tibial, femoral. It's a momentary expansion in response to blood being pushed, so after capillary beds enter post-capillary vein, to venules to veins, the pressure decreases.
Venous blood pressure
To keep it moving toward the heart, it relies on:
skeletal muscle movements (squeezing vessels keeps blood moving in right direction to heart)
respiratory movements - like a bellows - inhalation pushes the diaphragm down, so it pushes on veins and keep blood moving.
measurement of pressure in arteries. 110-120 over 70-80 mm Hg is normal range. Upper - systolic pressure (greatest pressure due to contraction), lower # is diastolic pressure (heart not exerting/contracting - baseline).
Used to take blood pressure. Listen with stethoscope. Pump up around left brachial artery - 1st major artery off the aorta (fresh pressure). Listen for 1st sound - systolic. When no more sounds - diastolic.
Near epidemic in the US. High blood pressure. Anything over 135/90 mm Hg. Over time, overstretched arteries can become leaky, and can cause aneurysm, platelets can stick causing thrombus. Fluid can build up causing bilateral edema in lower limbs - people with cankles.
Sinuses, vascular sinuses
Vessels (especially veins) with large lumens that serve as blood reservoirs.
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