A&p Chapter 21 - The Cardiovascular System: Blood Vessels And Hemodynamics

Baroreceptors and chemoreceptors are sensory receptors that monitor blood pressure and chemical composition in the body. They are located in the aorta and carotid arteries because these arteries are major blood vessels that carry oxygenated blood to the brain and other vital organs. By being located in these areas, the baroreceptors and chemoreceptors can quickly detect any changes in blood pressure or chemical levels and send signals to the brain to regulate these parameters, ensuring proper functioning of the body. Therefore, the statement "Baroreceptors and chemoreceptors are located in the aorta and carotid arteries" is true.

The most important method of capillary exchange is simple diffusion because it allows for the movement of small molecules, such as oxygen and carbon dioxide, across the capillary walls. This process occurs due to the concentration gradient between the blood and the tissues, allowing for the exchange of nutrients, waste products, and gases. Other methods of capillary exchange, such as bulk flow and facilitated diffusion, are also important but not as crucial as simple diffusion.

The contraction of skeletal muscles surrounding the veins creates a pumping action that helps propel blood back to the heart, known as the skeletal muscle pump. This pump is especially important in the lower extremities where gravity can hinder venous return. The respiratory pump refers to the changes in pressure within the thoracic cavity during breathing. When we inhale, the diaphragm contracts and the thoracic cavity expands, causing a decrease in pressure. This decrease in pressure helps to draw blood back to the heart from the veins in the chest and abdomen. Both the skeletal muscle pump and respiratory pump rely on the presence of valves in the veins to prevent backflow of blood.

Systemic vascular resistance refers to the resistance encountered by blood flow in the systemic circulation. It depends on several factors, including blood viscosity, total blood vessel length, and the size of the lumen.

Blood viscosity refers to the thickness or stickiness of the blood, which affects the ease of blood flow. A higher viscosity increases resistance.

Total blood vessel length refers to the combined length of all blood vessels in the systemic circulation. The longer the blood vessels, the greater the resistance.

The size of the lumen, which is the opening or diameter of the blood vessels, also affects resistance. A smaller lumen size increases resistance.

Therefore, factors 1, 2, and 3 (blood viscosity, total blood vessel length, and size of the lumen) all contribute to systemic vascular resistance.

The correct answer is 1,2,3,4, and 5. Baroreceptor and chemoreceptor reflexes, hormones, autoregulation, H+ concentration of blood, and oxygen concentration of the blood all play a role in regulating blood pressure and controlling regional blood flow. Baroreceptor and chemoreceptor reflexes detect changes in blood pressure and chemical composition and initiate appropriate responses to maintain homeostasis. Hormones, such as angiotensin II and aldosterone, regulate blood pressure by constricting blood vessels and increasing fluid retention. Autoregulation allows organs and tissues to adjust their blood flow based on their metabolic needs. H+ concentration of blood and oxygen concentration of the blood also influence blood pressure and regional blood flow.

The carotid sinus reflex helps maintain normal blood pressure in the brain by regulating blood flow in the carotid arteries, which supply blood to the brain. The aortic reflex, on the other hand, governs general systemic blood pressure by regulating blood flow in the aorta, the largest artery in the body. Both reflexes play important roles in maintaining overall blood pressure homeostasis.

The given statement is correct because it correctly identifies the options that are not true. Options 1, 2, and 4 are not true. Muscular arteries are not known as conducting arteries, capillaries do not play a key role in regulating resistance, and the lumen of an artery is not larger than in a comparable vein. Therefore, the correct answer is 1, 2, and 4.

1. Large, lipid-insoluble molecules cross capillary walls by transcytosis: This statement is true. Transcytosis is the process by which large, lipid-insoluble molecules are transported across capillary walls.
3. If the pressures that promote filtration are greater than the pressures that promote reabsorption, fluid will move out of a capillary and into interstitial spaces: This statement is true. Filtration occurs when the hydrostatic pressure in the capillary is greater than the osmotic pressure, causing fluid to move out of the capillary and into the interstitial spaces.
4. A negative net filtration pressure results in reabsorption of fluid from interstitial spaces into a capillary: This statement is true. A negative net filtration pressure means that the osmotic pressure is greater than the hydrostatic pressure, causing fluid to be reabsorbed from the interstitial spaces into the capillary.

Vasodilation refers to the widening of blood vessels, which would actually decrease vascular resistance. Anemia refers to a decrease in red blood cell count, which would also decrease vascular resistance. Therefore, options 1 and 5 are correct as they both would not increase vascular resistance.

Capillary exchange refers to the movement of substances between the blood in the capillaries and the surrounding tissues. The slow rate of flow through the capillaries allows more time for exchange to occur. A small cross-sectional area of capillaries increases the pressure and velocity of blood flow, facilitating exchange. The thinness of capillary walls allows for the diffusion of substances. Extensive branching of capillaries increases the surface area available for exchange. Therefore, options 1, 3, and 5 are correct as they all contribute to enhancing capillary exchange.

Atrial natriuretic peptide, lactic acid, histamine, nitric oxide, and decreased sympathetic impulses all cause vasodilation.