What are the main functions of the circulatory system?
Key Terms
How does the circulatory system regulate body temperature?
Blood vessels can undergo vasoconstriction and vasodilation. In cold temperatures, arterioles near the skin become narrow, or constrict, to limit h...
Describe the general structure of the human heart.
A human heart has four chambers, with the left and the right atrium positioned above the left and the right ventricle. The atria and ventricles are...
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| Term | Definition |
|---|---|
What are the main functions of the circulatory system? | Circulate oxygen, nutrients, hormones, fluids, and ions to body tissues. Remove carbon dioxide. Remove metabolic wastes, such as urea. Aid in thermoregulation. |
How does the circulatory system regulate body temperature? | Blood vessels can undergo vasoconstriction and vasodilation. In cold temperatures, arterioles near the skin become narrow, or constrict, to limit heat loss. In hot temperatures, arterioles widen, or dilate, to allow heat to dissipate from the body's surface. |
Which type of muscle allows for variation in blood vessel diameter depending on the ambient temperature? | Smooth muscle lining the arteries and arterioles allows vasodilation and vasoconstriction to occur. Since smooth muscle is controlled by the autonomic nervous system, these thermoregulatory functions are involuntary. |
On a cold winter day, a woman leaves her office and begins a long walk to her car. How would her blood vessels respond? | Surface arterioles would vasoconstrict, reducing blood flow to the skin in an attempt to conserve heat. Long periods of vasoconstriction are usually interrupted by brief vasodilatory cycles to avoid the excessive restriction of blood flow. |
At 1 PM on a hot summer afternoon, a teenager goes outside to sunbathe. How would his blood vessels respond? | Surface arterioles would vasodilate, carrying blood close to the external environment in an attempt to dissipate heat. Vasodilation can explain the flushed red face of a person who has become overheated. |
Describe the general structure of the human heart. | A human heart has four chambers, with the left and the right atrium positioned above the left and the right ventricle. The atria and ventricles are separated by valves. The right side of the heart contains deoxygenated blood, while blood on the left side is oxygenated. |
What structural and functional differences distinguish an atrium from a ventricle? | Structurally, atria are smaller and located superior to the ventricles. Functionally, atria receive blood that returns to the heart and pump it to the ventricles, while ventricles pump blood to the rest of the body. |
In order, list the structures that blood will contact between the vena cava and the aorta. Do not include valves. | After returning to the heart via the vena cava, blood will contact the: Right atrium Right ventricle Pulmonary artery Lung Pulmonary vein Left atrium Left ventricle From the left ventricle, it exits the heart through the aorta. |
Name the two valves in the heart that separate an atrium from a ventricle. | The tricuspid valve is situated between the right atrium and the right ventricle. The bicuspid or mitral valve separates the left atrium from the left ventricle. Both of these structures are classified as atrioventricular valves. |
After blood is oxygenated in the lungs, which vessel carries it back to the heart? | Pulmonary vein Unlike the vast majority of venous circulation, the pulmonary vein carries oxygenated blood. Remember that veins are defined as vessels that transport blood toward the heart, not as vessels that carry oxygen-depleted blood. |
A certain heart malformation prevents the mitral valve from closing properly. How would this condition affect blood flow? | Some of the blood leaving the left atrium would leak back in instead of fully progressing to the left ventricle. Such defects can cause the heart to work harder to counteract the defective valve, causing stress and long-term impairments in blood flow. |
Define: systolic pressure | The blood pressure measured when the ventricles are contracting and blood is being pumped. Of the two pressure measurements, systolic pressure is larger and is given as the numerator. In the standard reading of '120 over 80,' the systolic pressure is 120 mmHg. |
Define: diastolic pressure | The blood pressure measured when the ventricles are relaxed and no blood is being pumped. Of the two pressure measurements, diastolic pressure is smaller and is given as the denominator. In the standard reading of '120 over 80,' the diastolic pressure is 80 mmHg. |
Name the main components present in arterial walls. | Arteries have thick walls that contain endothelium, elastic connective tissue, and smooth muscle. The elastic fibers allow arteries to stretch in diameter, while smooth muscle functions in vasoconstriction and vasodilation. |
What are the two major types of arteries, and where is each type located in the circulatory system? | Arteries are classified as either elastic or muscular. Elastic arteries are those that attach directly to the heart, namely the aorta and pulmonary artery. Muscular arteries are more distant from the heart and carry blood to systemic organs. |
Describe the structural differences between elastic and muscular arteries. | Elastic arteries contain more connective fibers, such as collagen and elastin. This allows for expansion to accommodate blood that is pumped from the heart. Muscular arteries contain more smooth muscle, as they need to constrict or dilate to control blood flow to a specific region of the body. |
What is the function of arterioles? | They connect directly to arteries and control blood flow to the capillaries. Structurally, they are smaller than arteries but otherwise similar. Arterioles are the primary site of vasoconstriction. |
Describe the similarities between arterial and venous walls. | Like arteries, veins contain an inner lining of endothelium, as well as smooth muscle and connective tissue. |
Describe the differences between arterial and venous walls. | Venous walls are thinner than arterial walls. As a result, the lumen or interior of a vein is larger than that of an artery, allowing it to hold more blood. Specifically, veins contain less elastic tissue and less smooth muscle than arteries. Veins also have one-way valves, which prevent blood from traveling away from the heart. |
What is the function of venules? | They collect blood from the capillaries and carry it to the veins. Structurally, they are smaller than veins but otherwise similar. |