Which type of vessel connects arterioles to venules?
Capillaries, the smallest and most numerous blood vessels, arise from arterioles and converge into venules. They form the site of gas and nutrient exchange with the tissues.
Key Terms
Which type of vessel connects arterioles to venules?
Capillaries, the smallest and most numerous blood vessels, arise from arterioles and converge into venules. They form the site of gas and nutrient ...
A student observes a circulatory structure that is lined with endothelium, has valves, and can vasoconstrict. Which type of blood vessel is this?
vein
Only veins have valves to prevent backflow. Arteries, veins, and arterioles can all vasoconstrict to some degree, and all blood vessels ...
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| Term | Definition |
|---|---|
Which type of vessel connects arterioles to venules? | Capillaries, the smallest and most numerous blood vessels, arise from arterioles and converge into venules. They form the site of gas and nutrient exchange with the tissues. |
Which process provides the pressure that propels blood into arteries? | Contraction of the ventricles. Vasoconstriction can also alter blood pressure and control the flow of blood to specific tissues; however, it occurs mainly in the arterioles. |
Which process provides the pressure that carries blood back to the heart through veins? | The contraction of nearby skeletal muscle compresses veins, propelling blood forward. Veins can also alter their pressure by constricting or dilating. In the lower part of the body, gravity opposes proper venous blood flow. To prevent blood from traveling backwards, veins contain one-way valves. |
Which type of blood vessel has the lowest pressure? | Veins Pressure is highest in the arteries and decreases in the same order as the circulatory structure itself: arterioles, capillaries, venules, veins. |
In which type of vessel does blood flow the slowest? | In the capillaries. According to the continuity equation, fluid velocity and cross-sectional area of a vessel are inversely related. Since all of the body's capillaries combine to have an extremely large area, blood moves through them slowly. |
A student observes a circulatory structure that is lined with endothelium, has valves, and can vasoconstrict. Which type of blood vessel is this? | vein Only veins have valves to prevent backflow. Arteries, veins, and arterioles can all vasoconstrict to some degree, and all blood vessels possess endothelium. |
A student observes a circulatory structure that directly connect to capillaries, carries blood away from the heart, and can vasoconstrict. Which type of blood vessel is this? | arteriole Only venules and arterioles directly connect to the capillaries, and only the arterial system carries blood away from the heart. Arterioles often control their diameter via vasoconstriction. |
What is the primary difference between pulmonary and systemic vessels? | Systemic veins carry deoxygenated blood, while systemic arteries contain blood that has been oxygenated. The reverse is true for pulmonary circulation. Pulmonary circulation refers to bloodflow between the heart and the lungs, while systemic circulation provides blood to the rest of the body. |
What function do capillary beds serve? | They provide a site where oxygen, carbon dioxide, nutrients, and wastes are exchanged between blood and interstitial fluid. |
Which two opposing pressures control the movement of fluid between capillaries and tissues? | Hydrostatic pressure Osmotic pressure Hydrostatic pressure is synonymous with blood pressure and promotes the movement of fluid out of the capillaries. Osmotic pressure is controlled by solute concentration and promotes the return of fluid from the tissues. |
What name is given to osmotic pressure that is specifically produced by proteins? | Oncotic pressure In the circulatory system, proteins have a unique ability to generate osmotic pressure, since they are too large to leave the capillaries. Albumin is a notable example of such a protein. |
Which transport method is used in the capillary exchange of most gases and solutes? | diffusion In general, diffusion is favored by small, nonpolar substances. Oxygen and nutrients flow from the blood, where their concentration is relatively high, to the interstitial fluid. Carbon dioxide and waste flow from the insterstitial fluid to the blood. |
How is the circulatory system involved in thermoregulation? | Vasoconstriction and vasodilation function to control body temperature. In hot conditions, vessels dilate to bring blood close to the outside environment and facilitate heat loss. Cold conditions promote constriction to keep blood close to the warmer core. Indirectly, plasma also provides fluid that diffuses into the interstitium and eventually comprises sweat. |
How do capillary walls differ from the walls of other types of blood vessels? | Capillary walls consist only of a single layer of endothelium. This thin-walled structure facilitates the diffusion of gases and solutes. Since capillaries do not contain smooth muscle, they cannot vasoconstrict. |
In which part of a capillary bed does hydrostatic pressure predominate? | At the arterial end, closest to the heart. Since hydrostatic pressure is simply another name for blood pressure, it is highest at the beginning of a capillary bed. As fluid is pushed outward, it decreases and eventually is surpassed by osmotic pressure. |
Which type of pressure would be disrupted by a condition that introduced large holes or gaps to capillary walls? | Osmotic, or oncotic, pressure. Osmotic pressure in a capillary bed is maintained by proteins, which are too large to leave the vessels. If capillary walls became more permeable to large molecules, this function would be altered, disrupting the flow of fluid back into the capillary. |
What is/are the site(s) of blood oxygenation and detoxification in the fetus, and how does this differ from adult circulation? | In adult circulation, gas exchange occurs within the lungs, while detoxification of blood is performed by the liver. In the fetus, both of these functions are performed by the placenta. For this reason, adaptations of the fetal circulatory system exist to bypass both the lungs and the liver. |
Which structures are connected by the ductus arteriosus? | The ductus arteriosus directly connects the pulmonary artery to the aorta. Much of fetal blood does not even reach the pulmonary artery, but this adaptation ensures that any blood that does reach this vessel will still bypass the lungs. |
Which structures are connected by the ductus venosus? | The ductus venosus directly connects the umbilical vein to the inferior vena cava. This adaptation allows oxygenated blood from the placenta to bypass the liver. |
What is the function of the foramen ovale? | This is a hole between the fetal atria that allows oxygenated blood to travel directly from the right atrium to the left atrium. (Normally, in adults, the blood in the right atrium is deoxygenated. In a fetus, however, this blood was already oxygenated in the placenta.) Along with the ductus arteriosus, the foramen ovale causes fetal blood to bypass the lungs. |
Why are adaptations to fetal pulmonary circulation necessary? | Fetal lungs are underdeveloped and fluid-filled, so they are bypassed by fetal circulation. Additionally, a fetus receives oxygen from maternal blood, not the external environment; this renders the lungs unnecessary. |
What may occur if the ductus arteriosus does not close properly after birth? | Oxygenated blood from the aorta may flow back to the lungs, resulting in high pulmonary pressure and difficulty breathing. This condition is known as "patent ductus arteriosus" and can lead to congestive heart failure. |