Pulmonary and Systemic Circuits
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MCAT Biology › Pulmonary and Systemic Circuits
Which vessel carries blood away from the right ventricle of the heart?
Pulmonary arteries
Pulmonary veins
Aorta
Superior vena cava
Explanation
The pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs for oxygenation. Arteries always carry blood away from the heart, while veins always carry blood toward the heart. The pulmonary arteries are the only arteries to carry deoxygenated blood. After traveling to the lungs, blood is returned to the left atrium via the pulmonary veins, the only veins to carry oxygenated blood.
The aorta carries blood from the left ventricle to the body for systemic circulation. The vena cavae return the blood from systemic circulation to the right atrium. The superior vena cava returns blood from the head upper extremities, while the inferior vena cava returns blood from the abdomen and lower extremities.
An obstruction in the pulmonary artery would cause an immediate increase in blood pressure which region?
Right ventricle
Right atrium
Pulmonary veins
Left ventricle
Explanation
When an obstruction causes a restriction of flow, increased pressure will occur upstream of the blockage. In the cardiopulmonary system blood flows from the right atrium to the right ventricle, then through the pulmonary artery, lungs, and pulmonary vein, before re-entering the heart at the left atrium.
Should a blockage occur in the pulmonary artery, blood will pool behind the blockage (upstream) in the right ventricle, increasing the pressure in this chamber.
Which structures contain deoxygenated blood?
Right ventricle and pulmonary arteries
Right and left atria
Superior vena cava and left ventricle
Pulmonary veins and right ventricle
Explanation
When blood returns to the heart via the superior and inferior vena cavae, it is deoxygenated. It remains this way as it passes through the right atrium, the right ventricle, and the pulmonary arteries, through which it travels to the lungs to conduct gas exchange with the alveoli. Both the right ventricle and the pulmonary artery contain deoxygenated blood.
All of the other answer choices contain at least one component that carries oxygenated blood.
The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the sub-arachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.
Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma.
Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma.
According to the passage, the cerebral vein will ultimately drain into which structure?
Superior vena cava
Aorta
Left ventricle
Foramen spinosum
None of these
Explanation
All of the venous blood will ultimately drain into the vena cava. From the vena cava, blood is then drained into the right atrium, the right ventricle, the pulmonary artery and finally to the lungs to exchange carbon dioxide for oxygen.
Hemoglobin is the principal oxygen-carrying protein in humans. It exists within erythrocytes, and binds up to four diatomic oxygen molecules simultaneously. Hemoglobin functions to maximize oxygen delivery to tissues, while simultaneously maximizing oxygen absorption in the lungs. Hemoglobin thus has a fundamentally contradictory set of goals. It must at once be optimized to absorb oxygen, and to offload oxygen. Natural selection has overcome this apparent contradiction by making hemoglobin exquisitely sensitive to conditions in its microenvironment.
One way in which hemoglobin accomplishes its goals is through the phenomenon of cooperativity. Cooperativity refers to the ability of hemoglobin to change its oxygen binding behavior as a function of how many other oxygen atoms are bound to the molecule.
Fetal hemoglobin shows a similar pattern of cooperativity, but has unique binding characteristics relative to adult hemoglobin. Fetal hemoglobin reaches higher saturation at lower oxygen partial pressure.
Because of cooperativity, adult and fetal oxygen-hemoglobin dissociation curves appear as follows.
Beyond its ability to carry oxygen, hemoglobin is also effective as a blood buffer. The general reaction for the blood buffer system of hemoglobin is given below.
H+ + HbO2 ←→ H+Hb + O2
Hemoglobin binding to oxygen is dependent on oxygen partial pressure, as depicted in the above graph. Where is oxygen partial pressure likely to be the highest?
Lung capillaries
Aorta
Tissue arterioles
Capillaries
Venules
Explanation
Oxygen partial pressure is likely to be highest in the lung capillaries, as this is where oxygen will be "loaded" on to hemoglobin molecules for transportation to the tissues. Since binding affinity increases with oxygen partial pressure, one would also expect red blood cells in lung capillaries to bind the strongest to oxygen, which allows hemoglobin saturation in the lungs.
The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the sub-arachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.
Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma.
Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma.
The meningeal artery received its blood supply from which specific structure?
Left ventricle
Right ventricle
Right atrium
Pulmonary artery
Inferior vena cava
Explanation
Oxygen-rich blood will enter the left atrium, left ventricle, aorta, then to the systemic circulation including the brain.
Which heart chamber is more muscular and why?
The left ventricle requires more muscle because it must keep blood in the aorta at a high pressure
The left ventricle requires more muscle because it must pump more blood than the right ventricle
The right ventricle requires more muscle because it must keep blood entering the lungs at higher pressure than blood entering the aorta
The right ventricle requires more muscle because it must pump more blood than the left ventricle
Explanation
The left ventricle is more muscular than the right ventricle because it must keep the blood in the aorta at high pressure. The high blood pressure in the aorta helps to continue pushing the rest of the blood in the general circulation through the body and back to the heart. The blood in the pulmonary artery is actually at lower pressure than blood in the aorta, since pulmonary capillaries would easily rupture otherwise.
Note that both ventricles pump the same volume of blood, as any blood passing through one ventricle will ultimately return to the other. Blood can be thought of as the current flow in a series circuit.
A man is diagnosed with increased pulmonary capillary resistance. As a result, which part of the heart would be expected to increase in muscle mass?
Right ventricle
Left ventricle
Right atrium
Left atrium
Right ventricle and left atrium
Explanation
Increased pulmonary resistance means that it will be more difficult to pump blood into the lungs. The right ventricle, which performs this function, will compensate by increasing in muscle mass. The left atrium will not increase in muscle mass because it receives blood from the lungs and pumps blood into the left ventricle; its muscle mass will likely be unaffected.
What is the proper path of a drop of blood through the vascular system, starting in the right atrium?
Right atrium, right ventricle, pulmonary arteries, lungs, pulmonary veins, left atrium, left ventricle, aorta, arteries, arteriorles, capillaries, venules, veins, vena cavae
Right atrium, left atrium, pulmonary arteries, lungs, pulmonary veins, right ventricle, left ventricle, aorta, arteries, arteriorles, capillaries, venules, veins, vena cavae
Right atrium, right ventricle, aorta, arteries, arteriorles, capillaries, venules, veins, vena cavae, left atrium, left ventricle, pulmonary arteries, lungs, pulmonary veins
Right atrium, left atrium, aorta, arteries, arteriorles, capillaries, venules, veins, vena cavae, right ventricle, left ventricle, pulmonary arteries, lungs, pulmonary veins
Explanation
The correct path of a drop of blood through the vascular system is right atrium, right ventricle, pulmonary arteries, lungs, pulmonary veins, left atrium, left ventricle, aorta, arteries, arteriorles, capillaries, venules, veins, vena cavae.
The right atrium and ventricle transfer deoxygenated blood to the lungs via the pulmonary arteries. Blood is oxygenated and returned to the left artium via the pulmonary veins. The left ventricle then pumps the oxygenated blood to the body, exiting the heart through the aorta. Systemic circulation flows through arteries, then arterioles, then capillaries where gas exchange occurs to tissues. Blood is then returned to the heart through venules and veins, which merge into the superior and inferior vena cavae and empty into the right atrium to complete the circuit.
Which of the following paths correctly orders blood flow through the systemic circuit of the circulatory system?
Left ventricle, aorta, vena cavae, right atrium
Right ventricle, pulmonary arteries, pulmonary veins, left atrium
Left ventricle, aorta, pulmonary veins, right atrium
Right ventricle, aorta, vena cava, left atrium
Explanation
The heart is composed of two circuits: the pulmonary circulation on the right side of the heart, and the systemic circulation on the left side of the heart. Keep in mind that these simplified pathways are ignoring the arterioles, capillaries, and venules that are present in each circulation.
Pulmonary circulation is ordered from the right ventricle to the pulmonary arteries, through the lungs, to the pulmonary veins, and reenters the heart in the left atrium.
Systemic circulation is ordered from the left ventricle to the aorta, through the structures of the body, to the superior or inferior vena cava, and reenters the heart in the right atrium.