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172 Cards in this Set
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blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood. Blood leaves the heart by way of the pulmonary trunk and aorta, these vessels branch repeatadly, forming the vessels that distribute blood to body organs
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Arteries
Page 429 |
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Within the arteries further branching occurs, creating several hundred million tiny arteries called...
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Arterioles
Page 429 |
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Arterioles provide blood to more than 10 billion of these...
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Capillaries
Page 429 |
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Click here for a key point
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Chemical and gaseous exchange between the blood and interstitial fluid occurs across capillary walls
Tissue cells rely on cpillary diffusion to obtain nutrients and oxygen and to remove metabolic wates such as carbon dioxide and urea. Page 429 |
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The smallest vessels of the venous system
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Venules
Page 429 |
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Venules, the smallest vessels of the venous system merge to form what....
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Veins
Page 429 |
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Blood passes through medium to large viens before reaching what structures......
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1.The venae cavae
(in the systemic circit) 2.The pulmonary viens (in the pulmonary circuit) |
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The innermost layer of a blood vessel
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Tunica intima or tunica interna
Page 429 |
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The middle layer of a blood vessel. Contains smooth muschle tissue in a framework of collagen and elastic fibers.
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Tunica media
When the smooth muscles contract, vessel diameter decreases; when they relax, vessel diametr increases Page 429 |
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The outer layer of a blood vessel. It froms a sheath of connective tissue around the vessel.
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Tunica externa or tunica adventitia
Its collagen fibers may intertwine with those of adjacent tissues, stabilizing and anchoring the blood vessel Page 429 Page 429 |
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Arterial smooth muscle is under the control of the sympathetic division of the autonomic nervous system. When stimulated, these muscles in the vessel wall contract and the artery constricts in a process called...
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Vasoconstriction
Page 429 |
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Relaxation increases the diameteer of the artery and its central opening the lumen, in a process called....
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Vasodilation
Page 429 |
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Large, extremely resilient vessels with diameters of up to 2.5 cm (1 in) Some examples are the pulmonary trunk and the aorta, and thier major arterial branches.
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Elastic arteries
Page 430 |
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These arteries distribute blood to skeletal muscles and internal organs. A typical muscular artery has a diameter of approximately 0.4 cm (0.15 in.) The external carotid arteries of the neck are one example.
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Muscular arteries
Page 430 |
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These are much smaller than the muscular arteries and have an internal diameter of about 30 um
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Arterioles
Page 430 |
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Click here for a key point
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Capillaries are the only blood vessels whose walls permit exchange between the blood and the surrounding interstitial fluid. The average diameter is 8 um very close to that of a red blood cell.
Page 430 |
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Capillaries do not function as individual units but as part of an interconnected network called...
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a capillary bed
Page 431 |
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The entrance to each capillary is guarded by a band of smooth muscle. Contraction of the smooth muscle fibers narrows the diameter of the capillary's entrance and reduces the blood flow. This is called a....
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Precapillary sphincter
Page 432 |
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A cyclical change in blood flow within any given capillary is intermittent rather than a steady and constant stream. The result of this is called
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Vasomotion
the spontaneous oscillation in tone of blood vessels, independent of heart beat, innervation or respiration. Page 432 |
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a network of streams that both branch out and reconnect, such as blood vessels or leaf veins
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Anastomosis
Page 433 |
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Under certian conditions, blood completely bypasses a capillary bed through an....
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Arteriovenous anastomosis
A blood vessel that connects an arteriole directly to a venule without capillary intervention. Page 433 |
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is when more than one artery fuses before giving rise to arterioles. An arterial anastomosis in effect provides an insurance policy for capillary beds: If one artery is compressed or blocked, the others can continue to deliver blood to the capillary bed, and dependent tissues will not be damaged.
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Arterial anastomosis
Page 433 |
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Click here for a key point
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Veins collect blood from all tissues and organs and return it to the heart.
Page 433 |
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Click here for a key point
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Viens are classified on the basis of their internal diameters
Page 433 |
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The smallest of the viens resembling expanded capillaries
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Venules
Any smaller than 50 um lack a tunica media altogether. Page 433 |
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These viens range from 2 mm to 9 mm in diameter, (comparable in size with muscular arteries).
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Medium-sized veins
In these veins, the tunica media contains several smooth muscle layers, and the relatively thick tunica externa has longitudinal bundles of elastic and collagen fibers. Page 433 |
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These viens include the two venae cavae and their tributaries in the abdominopelvic thoracic cavities.
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Large veins
In these vessels, the thin tunica media is surrounded by a thick tunica externa compossed of elastic and collagenous fibers. Page 433 |
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Click here for a key point
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Veins have relatively thin walls because they need not withstand much pressure. in venules and medium sized veins the pressure is so low that it cannot overcome the force of gravity.
Page 433 |
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Medium sized veins contain folds of endothelium that function like the valves in the heart, preventing the backflow of blood. These structures are called....
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Valves
Page 433 |
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Another word for pressure difference
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Pressure gradient
Page 434 |
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Click here for a key point
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The flow rate is directly proportional to the pressure difference: the greater the difference in pressure, the faster the flow
Page 434 |
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The largest presure difference (or presure gradient) is found in the systemic circuit between the base of the aorta (where blood leaves the left ventricle) and the entrance to the right atrium (where blood returns to the heart). This presure difference is called
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Circulatory pressure
Averages about 100 mm Hg. This relitively high circulatory pressure is needed primarily to force blood through the arterioles and into the capillaries. Page 434 |
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Circulatory pressure is dived into three components
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1.Arterial pressure (routinely measured on a person's arm and referred to as blood presure)
2.Capillary pressure 3.Venous pressure Page 434 |
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Any force that opposes movement
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Resistance
Page 434 |
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The resistance of the entire cardiovascular system.
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Total peripheral resistance
Page 435 |
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The resistance of the arterial system is
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Peripheral resistance
Page 435 |
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Sources of peripheral resistance include....
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1.Vascular resistance
2.Viscosity 3.Turbulence Page 435 |
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The resistance of the blood vessels to blood flow
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Vascular resistance
The most important factor in vascular resistance is friction between the blood and the vessel walls. Page 435 |
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The resistance to flow resulting from interactions among molecules and suspended materials in a liquid
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Viscosity
Page 435 |
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A disorder in which the hematocrit is redueced due to inadequate production of hemoglobin, RBC's, or both.
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Anemia
Page 435 |
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Blood flowing at high rates, irregular surfaces caused by injury or disease processes, or sudden changes in vessel diameter upset the smooth flow of the blood, creating eddies and swirls. This phenomenon is called...
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Turbulence
Page 435 |
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The peak blood pressure measured during ventricular systole
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Systolic pressure
Page 435 |
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The minimum blood pressure at the end of ventricular diastole
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Diastolic pressure
Page 435 |
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A rhythmic pressure oscillation that accompanies each heartbeat
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Pulse
Page 435 |
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The difference between the systolic and diastolic pressure
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Pulse pressure
Page 435 |
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When diastole begins and blood pressures fall, the arteries recoil to their original dimensions. Because the aoritc semilunar valve prevents the return of blood to the heart, arterial recoil adds an extra push to the flow of blood. The magnitude of this phenomenon is called...
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Elastic rebound
Page 436 |
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What is the presure at the start of the venous system
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18 mm Hg
Page 436 |
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What is the blood pressure when it reaches a precapillary sphincter
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about 35 mm Hg
Page 436 |
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The presure of blood within a capillary bed
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Capillary pressure
Page 436 |
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Thin walled, valved structures that carry lymph
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Lymphatic vessels
Page 436 |
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Capillary exchange has 4 important functions
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1.Maintaining constant communication between plasma and interstitial fluid
2.Speeding the distribution of nutrients, hormones, and dissolved gases throughout tissues 3.Assisting the movement of insoluble lipids and tissue proteins that cannot cross capillary walls 4.Flushing bacterial toxins and other chemical stimuli to lymphoid tissues and organs that function in providing immunity to disease. Page 436 |
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Capillary hydrostatic pressure (CHP)
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Greatest at the arteriolar end (35 mm Hg) and least at the venous end (18 mm Hg)
Page 437 |
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The movement of water across a selectively permeable memberane separating two solutions with different solute concentrations
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Osmosis
Page 437 |
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The pressure that must be applied to a solution to prevent the inward flow of water across a semipermeable membrane.[1]
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Osmotic pressure
Page 437 |
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An abnormal accumulation of interstitial fluids in the tissues
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Edema
Page 437 |
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A net movement of water from the interstitial fluid to the bloodstream increasing blood volume is called
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A recall of fluids
Page 437 |
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What is the approximate pressure at the entrance to the right atrium of the venous system
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2 mm Hg
Page 437 |
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Two factors help overcome gravity and propel venous blood toward the heart
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1.Muscular compresion
2.The respiratory pump Page 439 |
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Three variable factors influence tissue blood flow
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1.Cardiac output
2.peripheral resistance 3.blood pressure Page 439 |
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Mechanisms involved in the regulation of cardiovascular function include the following
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1.Autoregulation
2.Neural mechanisms 3.Endocrine mechanisms Page 439 |
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Factors that promote the dilation of precapillary sphincters are called....
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Vasodilators
Page 440 |
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Factors that stimulate the constriction of precapillary sphincters are called....
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Vasoconstrictors
Page 440 |
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This center increases cardiac output through sympathetic innervation
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Cardioacceleratory center
Page 440 (reference chapter 12) |
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This center reduces cardiac output through parasympathetic innervation
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Cardioinhibitory center
Page 440 |
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This center controls the diameters of arterioles through sympathetic innervation.
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Vasomotor center
Inhibition of the vasomotor center leads to vasodilation (dialation of arterioles) reducing peripheral resistance. Stimulation of the vasomotor center causes vasoconstriction (constriction of peripheral arterioles). Page 440 |
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Very strong stimulation of the vasomotor center causes
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Venoconstriction (constriction of peripheral veins)
Page 441 |
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Baroreceptor reflexes respond to changes in
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Blood pressure
Page 441 |
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Chemoreceptor reflexes respond to changes in
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chemical composition
Page 441 |
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These receptors monitor the degree of stretch in the walls of expandable organs
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Baroreceptors
Page 441 |
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Pockets in the walls of the aorta adjacent to the heart
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Aortic sinuses
Baroreceptors involved in cardiac regulation are located in the aortic sinuses and in the walls of the carotid sinuses, and in the wall of the right atrium Page 441 |
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Expanded chambers near the bases of the internal carotid arteries of the neck
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Carotid sinuses
Baroreceptors involved in cardiac regulation are located in the aortic sinuses and in the walls of the carotid sinuses, and in the wall of the right atrium Page 441 |
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Autonomic reflexes that adjust cardiac output and peripheral resistance to maintaiin normal arterial pressures.
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Baroreceptor reflexes
Page 441 |
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This reflex responds to changes in carbon dioxide, oxygen, or pH in blood and cerebrospinal fluid. They can be found in the carotid bodies (located in the neck and near the carotid sinuses) and in the aortic bodies (near the arch of the aorta), where they monitor the chemical composition of the arterial blood
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Chemoreceptor reflexes
Additional chemoreceptors on the surface of the medulla oblongata monitor the composition of the cerebrospinal fluid (CSF) Page 442 |
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Click here for a key point
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Chemoreceptors are activated by a drop in pH or in plasma, O2, or by a rise in CO2. Any of these changes leads to a stimulation of the cardioacceleratory and vasomotor centers,
Page 443 |
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Large reservoirs of slowly moving venous blood in the liver, bone marrow, and skin
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Venous reserve
This venous compensation can restore normal arterial pressures and peripheral blood flow after losses of 15-20 percent of total blood volume Page 445 |
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An acute circulatory crisis marked by low blood pressure (Hypotension) and inadequate peripheral blood flow.
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Shock
Page 446 |
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Composed of arteries and veins that transport blood between the heart and the lungs. This circuit begins at the right ventricle and ends at the left atrium.
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The pulmonary circuit
Page 446 |
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This circuit is composed of arteries that transport oxygenated blood and nutrients to all other organs and tissues and veins that return deoxygenated blood to the heart. This circuit begins at the left ventricle and ends at the right atrium.
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Systemic circuit
Page 446 |
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The start of the pulmonary circit after traveling through the right atrium and right ventricle
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Pulmonary trunk
Page 447 |
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Coming off the pulmonary trunk curving over the superior border of the heart and branching in two directions one left and one right
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Left and right pulmonary arteries
Page 447 |
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The left and right pulmonary arteries branch repeatadly, giving rise to smaller and smaller arteries. The smallest branches, the pulmonary arterioles, provide blood to capillary networks that surround small air pockets, or....
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Alveoli
Page 447 |
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As oxygenated blood leaves the alveolar capillaries, it enters venules, which in turn unite to form larger vessels leading to the
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Pulmonary veins
These 4 viens (two from each lung) empty into the left atrium completing the pulmonary circuit Page 447 |
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The first systemic vessel and largest artery is the aorta. This part of the aorta begins at the aortic semilunar valve of the left ventricle.
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Ascending aorta
Page 448 |
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This part of the aorta curves across the superior surface of the heart conecting the ascending aorta with the desending aorta
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Aortic arch
Page 448 |
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The part of the aorta after the arotic arch
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Descending aorta
Page 448 |
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Three elastic arteries the brachiocephalic trunk along with the left common carotid artery and left subclavian artery origante along the aortic arch and provide blood where....
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The head, neck, shoulders, and upper limbs
We have only one brachiocephalic trunk (on the right side of the body) and that the left common carotid and left subclavian arteries arise separately from the aortic arch |
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The brachiocephalic trunk ascends for a short distance befor branching to form...
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The right common carotid artery and right subclavian artery
Page 448 |
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The subclavian arteries provide blood where....
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To the arms, chest wall, shoulders, back, and central nervous system
Page 450 |
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Before a subclavian artery leaves the thoracic cavity, it gives rise to 3 other major arteries. What are they?
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1.Internal thoracic artery
2.Vertebral artery 3.Thyrocervical trunk Page 450 |
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This artery supplies the pericardium and anterior wall of the chest and branches off the subclavian artery
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Internal thoracic artery
Page 450 |
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This artery supplies the brain and spinal cord and branches off the subclavian artery
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Vertebral artery
Page 450 |
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This artery branches off the subclavian artery and provides blood to the muscles and other tissues of the neck, shoulder, and upper back
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Thyrocervical trunk
Page 450 |
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After the subclavian artery passes the first rib it gets a new name....
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Axillary artery
Page 450 |
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This artery crosses the axilla (armpit) to enter the arm where the name changes from Axillary artery to....
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Brachial artery
Page 450 |
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The brachial artery provides blood to the arm before branching into these two arteries
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Radial artery and Ulnar artery
Page 450 |
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The radial artery and ulnar arteries connect at the palm to form anastomoses which are called the...
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Palmar arches
Page 450 |
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The palmar aarches is where the arteries in the fingers form from these arteries are called
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Digital arteries
Page 450 |
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This major artery can usually be located by pressing gently along either side of the windpipe (trachea) until a strong pulse is felt
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External carotid artery
Page 450 |
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This artery suplies blood to the pharynx, esophagus, larynx, and face
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External carotid artery
Page 450 |
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These arteries enter the skull to deliver blood to the brain and eyes
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Internal carotid artery
Page 450 |
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Latin: 'great hole') is one of the several oval or circular apertures in the base of the skull (the foramina), through which the medulla oblongata (an extension of the spinal cord) enters and exits the skull vault.
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Foramen magnum
Page 450 |
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The vertebral arteries ascend within the transverse foramina of the cervical vertebrae, penetrating the skull at the foramen magnum. Inside the cranium, they fuse to form this large artery which continues along the ventral surface of the brain
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Basilar artery
Page 450 |
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The interior carotids and the basilar artery are interconnected in what is called
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The cerebral arterial circle
(Circle of Willis) This is a ring shaped anastomosis that encircles the stalk of the pituitary gland. Due to this the brain can receive blood from either the carotid or the vertebral arteries and the chances for a serious interruption of circulation is reduced. Page 450 |
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The descending aorta is continuous with the aortic arch. The diaphragm divedes the descending aorta into a supior and inferior called....
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Thoracic aorta (superior)
Abdominal aorata (inferior) Page 451 |
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Near the diapharagm these arteries deliver blood to the muscular diaphragm which separates the thoracic and abdominopelvic cavities
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Phrenic arteries
Page 451 |
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These three vessels branching off the anterior wall of the abdominal aorta provide blood to all of the digestive organs whithin the abdominopelvic cavity
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1.Celiac trunk
2.Superior mesenteric artery 3.Inferior mesenteric artery These arteries divide further to supply individual structures within the abdominal cavity. Page 453 |
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This artery branching off the abdominal aorta into the abdominal cavity divides into three branches supplying blood to the liver, gallbladder, stomach, and spleen.
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Celiac trunk
Page 453 |
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This artery branching off the abdominal aorta into the abdominal cavity supplies blood to the pancreas, small intestine, and most of the large intestine
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Superior mesenteric artery
Page 453 |
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This artery branching off the abdominal aorta into the abdominal cavity delivers blood to the last portion of the large intestine and rectum
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Inferior mesenteric
Page 453 |
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Originating between the superior and inferior mesenteric arteries these become testicular arteries in males and ovarian arteries in females
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Gonadal arteries
Page 453 |
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These arteries arise along the lateral surface of the abdominal aorta and travel behind the peritoneal lining to reach the suprarenal glands and kidneys
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Suprarenal arteries and renal arteries
Page 453 |
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These arteries begin on the posterior surface of the aorta and supply the spinal cord and the abdominal wall
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Lumbar arteries
Page 454 |
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Near the level of vertebra L4, the abdominal aorta divides to form a pair of muscular arteries. These arteries carry blood to the pelvis and lower limbs
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Common iliac arteries
Page 454 |
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As the common iliac artery travels along the inner surface of the ilium it divides to form this artery that supplies smaller arteries of the pelvis
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Internal iliac artery
Page 454 |
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As the common iliac artery travels along the inner surface of the ilium it divides to form this artery that enters the lower limb
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External iliac artery
Page 454 |
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Once in the thigh the external iliac artery branches forming these two arteries...
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Femoral and Deep Femoral
Page 454 |
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When it reaches the back of the knee the femoral artery becomes the...
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Popliteal artery
Page 454 |
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The popliteal artery almost immediately branchs to form these there arteries
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1.Anterior tibial
2.Posterior tibial 3.Fibular Page 454 |
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At the ankle, the anterior tibial artery becomes the
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Dorsalis pedis artery
Page 454 |
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The posterior tibial artery divides in two and along with the dorsal pedis artery conects with two anastomoses. This arrangement produces an arch of viens on the top of the foot and an arch of viens on the bottom of the foot called
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Dorsal arch (top of foot)
Planter arch (bottom of foot) Page 454 |
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This large diameter short vien recieves blood from two regions the head and neck, and the upper limbs, shoulders, and chest
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Superior vena cava (SVC)
Page 454 |
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Small veins in the neural tissue of the brain empty into a network of thin walled channels called
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Dural sinuses
Page 454 |
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The largest of the dural sinuses located within the fold of the dura mater lying between the cerebral hemisphere
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Superior sagittal sinus
Page 454 |
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Most of the blood leaving the brain passes through one of the dural sinuses and leaves the skull through one of these veins
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Internal jugular viens
This vien runs parallel to the common carotid artery in the neck. Page 454 |
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These veins collects blood from the superficial structures of the head and neck.
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External jugular veins
Page 456 |
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These veins travel just beneath the skin, and a pulse can sometimes be detected at the base of the neck. This pulse is called
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Jugular venous pulse (JVP)
Page 456 |
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These veins drain the cervical spinal cord and the posterior surface of the skull, descending within the transverse foramina of the cervical vertebrae alongside the vertebral arteries
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Vertebral veins
Page 456 |
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A venous network in the palms collects blood from the digital veins. These vessels drain into these two veins that continue to run up the arm
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Cephalic and basilic vein
Page 456 |
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This superficial vien passes from the cephalic vein, medially and a t an oblique angle, to connect to the basilic vein
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Median cubital vein
(the medial cubital is the vein from which venous blood samples are typically collected) Page 456 |
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The deeper veins of the forearm consist of these two veins
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Radial and ulnar
Page 456 |
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The radial and ulnar veins fuse after crossing the elbow becoming the
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brachial vein
Page 456 |
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As the brachial vein continues toward the trunk, it joins the basilic vein before entering the axilla and becomes the
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Axillary vein
Page 456 |
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Click here for a key point
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The cephalic vein drains into the axillary vein at the shoulder
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The axillary vein then continues into the trunk, at the level of the first rib it becomes the
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Subclavian vein
Page 456 |
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After traveling a short distance inside the thoracic cavity, the subclavian meets and merges with the external and internal jugular veins of that side. This fusion creates the large
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Brachiocephalic vein
Also known as the innominate vein Page 456 |
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Near the heart , the two brachiocephalic veins (one on each side of the body) combine to create teh
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Superior vena cava
Page 456 |
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The superior vena cava receives blood from the thoracic body wall through the
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Azygos vein
Page 456 |
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the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart. It collects most of the veous blood from organs inferior to the diaphragm
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Inferior vena cava
Page 457 |
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Blood leaving the capillaries in the sole of each foot collects inot a network of veins called
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Plantar veins
Page 457 |
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Plantar veins supply the
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Plantar venous arch
Page 457 |
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The planter network provides blood to these three dep veins of the leg
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1.Anterior tibial vein
2.Posterior tibial vein 3.Fibular vein Page 457 |
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This vein drains blood from capillaries on the superior surface of the foot
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Dorsal venous arch
Page 457 |
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The dorsal venous arch is drained by two superficial veins
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1.The great saphenous vein
2.The small saphenous vein Surgeons often use segments of the great saphenous vein, the largest superficial vein, as a bypass vessel during coronary bypass surgery Page 457 |
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Behind the knee, the small saphenous, tibial, and fibular veins unite to form this vein
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The popliteal vein
Page 457 |
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When the popiteal vein reaches the femur it becomes the
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Femoral vein
Page 457 |
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Before penetrating the abdominal wall, the great saphenous and this vein join to form the femoral vein.
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Deep femoral vein
Page 457 |
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The femoral vein penetrates the body wall and emerges into the pelvic cavity as the
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External iliac vein
Page 457 |
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As the external iliac travels across the inner surface of the ilium, it is joined by this vein that drains the pelvic organs
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Internal iliac vein
Page 457 |
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The external iliac and internal iliac results in this vein that then meets its counterpart from the opposite side to form the inferior vena cava
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The common iliac vein
Page 458 |
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Click here for a key point
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In addition, the inferior vena cava receives blood from the gonadal, renal, suprarenal, phrenic, and hepatic veins before reaching the right atrium
Page 458 |
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Instead of traveling directly to the inferior vena cava, blood leaving the capillaries supplied by the celiac, superior, and inferior mesenteric arteries flows to the liver through the
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Hepatic portal system
Page 458 |
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A blood vessel connecting two capillary beds is called a
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Portal vessel
Page 458 |
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The network formed by the blood vessels that connect two capillary beds is called
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A portal system
Page 458 |
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Click here for a key point
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In the circulatory system of animals, a portal venous system occurs when a capillary bed drains into another capillary bed through veins. Both capillary beds and the blood vessels that connect them are considered part of the portal venous system.
Page 458 |
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Click here for a key point
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Blood in the hepatic portal vessels is quite different in coposition from that in other systemic veins because it contains substances absorbed by the digestive tract, including high concentrations of glucose and amino acids, various wastes, and an occasional toxin.
The hepatic portal system delivers blood containing these compounds to the liver, where liver cells absorb them for storage, metabolic conversion, or excretion. Page 458 |
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Blood from capilaries along the lower portion of the large intestine enters this vein
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The inferior mesenteric vein
Page 459 |
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On their way toward the liver, veins from the spleen, the lateral border of the stomach and the pancreas fuse with the inferior mesenteric forming this vein
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The splenic vein
Page 459 |
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This vein also drains the lateral border of the stomach, through an anastomosis with one of the branches of the splenic vein
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The superior mesenteric vein
In addition, the superior mesenteric collects blood from the entire small intestine and two-thirds of the large intestine. Page 459 |
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The fussion of the superior mesenteric and splenic veins form the
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Hepatic portal vein
Page 459 |
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The hepatic portal vein recieves blood from these veins that drain the medial border of the stomach and the cystic vein from the gallbladder
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Gastric veins
Page 459 |
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This vein travels from the gallbladder to the gastric veins
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Cystic vein
Page 459 |
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Click here for a key point
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The hepatic portal system ends where the hepatic portal vein empties into the liver capillaries
Page 459 |
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After passing through the liver capillaries, blood collects in the hepatic veins, which empty into the inferior vena cava. Because blood goes to the liver before returning to the heart, The composition of the blood in the systemic circulation remains relatively stable, regardless of the digestive activities under way
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A structure within the uterine wall where the maternal and fetal circulatory systmes are in close contact
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Placenta
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The fetus's blood reaches the placenta through a pair of arteries that arise from the internal iliac arteries before entering the umbilical cord. These arteries are called...
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Umbilical arteries
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At the placenta, the blood gives up co2 and wastes and picks up oxygen and nutrients.
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Blood returning from the placenta flows through an
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umbilical vein
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The umbilical vein reaches the developing liver of the fetus. Some of the blood flows through capillary networks within the liver; the rest bypass the liver capillaries and reaches the inferior vena cava within the ductus venosus
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In the fetus, the ductus venosus shunts a significant majority (80%) of the blood flow of the umbilical vein directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.
When the placental connection is broken at birth, blood flow through the umbilical vessels ceases, and they soon degenerate Page 461 Page 460 |
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This interatrail opening is associated with an elongate flap that acts as a valve. Blood can flow freely from the right atrium to the left atrium, but any backflow will close the valve and isolate the two chambers. Thus blood can enter the heart at the right atrium and bypass the pulmonary circuit. This interatrial opening is called the
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Foramen ovale
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a shunt connecting the pulmonary artery to the aortic arch. It allows most of the blood from the right ventricle to bypass the fetus' fluid-filled lungs, protecting the lungs from being overworked and allowing the left ventricle to strengthen. There are two other fetal shunts, the ductus venosus and the foramen ovale.
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Ductus arteriosus
Over 90 percent of the blood leaving the right ventricle passes through the ductus arteriosus and enters the systemic circuit rather than continuing to the lungs of the fetus (a fetus lungs are in a colapsed state) Page 461 |
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a shunt connecting the pulmonary artery to the aortic arch. It allows most of the blood from the right ventricle to bypass the fetus' fluid-filled lungs, protecting the lungs from being overworked and allowing the left ventricle to strengthen. There are two other fetal shunts, the ductus venosus and the foramen ovale.
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Ductus arteriosus
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