Answer the following question given this paragraph: The structure of the different types of blood vessels reflects their function or layers. There are three distinct layers, or tunics, that form the walls of blood vessels (Figure 40.16). The first tunic is a smooth, inner lining of endothelial cells that are in contact with the red blood cells. The endothelial tunic is continuous with the endocardium of the heart. In capillaries, this single layer of cells is the location of diffusion of oxygen and carbon dioxide between the endothelial cells and red blood cells, as well as the exchange site via endocytosis and exocytosis. The movement of materials at the site of capillaries is regulated by vasoconstriction, narrowing of the blood vessels, and vasodilation, widening of the blood vessels; this is important in the overall regulation of blood pressure. Veins and arteries both have two further tunics that surround the endothelium: the middle tunic is composed of smooth muscle and the outermost layer is connective tissue (collagen and elastic fibers). The elastic connective tissue stretches and supports the blood vessels, and the smooth muscle layer helps regulate blood flow by altering vascular resistance through vasoconstriction and vasodilation. The arteries have thicker smooth muscle and connective tissue than the veins to accommodate the higher pressure and speed of freshly pumped blood. The veins are thinner walled as the pressure and rate of flow are much lower. In addition, veins are structurally different than arteries in that veins have valves to prevent the backflow of blood. Because veins have to work against gravity to get blood back to the heart, contraction of skeletal muscle assists with the flow of blood back to the heart. Q: Three distinct layers or tunics form the walls of what structures; the first is a smooth, inner lining of endothelial cells in contact with the red blood cells? Choices: - lungs - white blood cells - alveoli - blood vessels A:
blood vessels
Answer the following question given this paragraph: At each level of a food chain, a lot of energy is lost. Only about ten percent of the energy passes to the next level. Where does that energy go? Some energy is given off as heat. Some energy goes into animal wastes. Energy also goes into growing things that another consumer can't eat, like fur. It's because so much energy is lost that most food chains have just a few levels. There's not enough energy left for higher levels. Q: Loss of energy is the reason that what typically has few levels? Choices: - humans - the atmosphere - video games - food chain A:
food chain
Q: Answer the following question given this paragraph: groups of angiosperms: the monocots and the eudicots. Seed food reserves are stored outside the embryo, in the form of complex carbohydrates, lipids or proteins. The cotyledons serve as conduits to transmit the broken-down food reserves from their storage site inside the seed to the developing embryo. The seed consists of a toughened layer of integuments forming the coat, the endosperm with food reserves, and at the center, the well-protected embryo. Most flowers are monoecious or bisexual, which means that they carry both stamens and carpels; only a few species selfpollinate. Monoecious flowers are also known as "perfect" flowers because they contain both types of sex organs (Figure 26.14). Both anatomical and environmental barriers promote cross-pollination mediated by a physical agent (wind or water), or an animal, such as an insect or bird. Cross-pollination increases genetic diversity in a species. Q: Monoecious flowers are also known as "perfect" flowers because they contain both types of what organ? Choices: - vascular organ - respiratory organ - phloem - sex organ A:
A: sex organ
Question: Answer the following question given this paragraph: The combustion of propane gas produces carbon dioxide and water vapor. Q: The combustion of propane gas produces carbon dioxide and what else? Choices: - methane - carbon monoxide - phosphorous - water vapor A:
Answer: water vapor
*Question*
Answer the following question given this paragraph: If you look up close, you would be able to see grains of sand. From this distance, you can see different layers from where the sand was laid down. This rock is sandstone. The sand grains are cemented together to make sandstone. Sandstone is a common type of sedimentary rock. Q: What type of rock is a sandstone? Choices: - igneous rocks - landform rocks - limestone rocks - sedimentary rocks A:
**Answer**
sedimentary rocks
*Question*
Answer the following question given this paragraph: 40.4 | Blood Flow and Blood Pressure Regulation By the end of this section, you will be able to: Describe the system of blood flow through the body Describe how blood pressure is regulated Blood pressure (BP) is the pressure exerted by blood on the walls of a blood vessel that helps to push blood through the body. Systolic blood pressure measures the amount of pressure that blood exerts on vessels while the heart is beating. The optimal systolic blood pressure is 120 mmHg. Diastolic blood pressure measures the pressure in the vessels between heartbeats. The optimal diastolic blood pressure is 80 mmHg. Many factors can affect blood pressure, such as hormones, stress, exercise, eating, sitting, and standing. Blood flow through the body is regulated by the size of blood vessels, by the action of smooth muscle, by one-way valves, and by the fluid pressure of the blood itself. Q: What blood pressure reading measures the pressure in the vessels between heartbeats? Choices: - metabolic - plasma - systolic - diastolic A:
**Answer**
diastolic