Human Body Chapter 25

The adrenal gland sits atop each kidney. It is responsible for producing hormones such as adrenaline and cortisol, which play a crucial role in regulating various bodily functions, including metabolism, blood pressure, and stress response. The pancreas is located in the abdomen and is responsible for producing insulin and digestive enzymes. The pituitary gland is located at the base of the brain and controls the release of hormones from other glands. The thymus gland is located in the chest and plays a role in the development of the immune system.

Urine is produced in the kidneys and then passes through the renal hilum, which is a narrow opening in the kidney, into the pelvis of the kidney. From there, it travels through the ureter, which is a tube that connects the kidney to the bladder. Once in the bladder, urine is stored until it is ready to be eliminated from the body through the urethra. Therefore, the correct answer is "pelvis of the kidney to ureter to bladder to urethra."

The nephron is the functional and structural unit of the kidneys. It is responsible for filtering waste products and excess water from the blood to form urine. Each kidney contains millions of nephrons, which consist of a glomerulus and a tubule. The glomerulus filters blood, while the tubule reabsorbs essential substances and excretes waste products. Therefore, the nephron plays a crucial role in maintaining the body's fluid balance and removing waste materials.

The correct answer is glomerular hydrostatic pressure (glomerular blood pressure). This pressure is the main force that pushes water and solutes out of the blood across the filtration membrane in the kidneys. It is generated by the pressure exerted by the heart on the blood vessels, specifically in the glomerulus of the kidney. This pressure is essential for the filtration process, allowing waste products and excess fluids to be removed from the blood and excreted as urine.

The renal corpuscle is the functional unit of the kidney responsible for filtering blood and forming urine. It consists of two main components: Bowman's capsule and glomerulus. Bowman's capsule is a cup-like structure that surrounds the glomerulus, which is a network of tiny blood vessels called capillaries. Together, Bowman's capsule and glomerulus work to filter waste products and excess fluids from the blood, allowing them to be excreted as urine. Therefore, the correct answer is Bowman's capsule and glomerulus.

The fatty tissue surrounding the kidneys acts as a cushion and support system for the kidneys, helping to stabilize their position and hold them in their normal position. This is important because it ensures that the kidneys are properly aligned and positioned within the body, allowing them to function optimally.

The juxtaglomerular apparatus is a part of the kidney that plays a crucial role in regulating the rate of filtrate formation and controlling systemic blood pressure. It is involved in the release of renin, an enzyme that helps to regulate blood pressure by constricting blood vessels and increasing the production of aldosterone, a hormone that promotes sodium and water reabsorption. This mechanism helps to maintain the balance of fluid and electrolytes in the body and regulate blood pressure.

Osmosis is the process by which water molecules move across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. In the context of the renal tubules, osmosis is responsible for the reabsorption of water from the filtrate back into the bloodstream. As the filtrate moves through the tubules, solutes such as sodium ions are actively transported out of the tubules, creating a higher solute concentration in the surrounding interstitial fluid. This concentration gradient drives the movement of water out of the tubules and into the interstitial fluid through osmosis, leading to water reabsorption.

The kidneys are stimulated to produce renin by a decrease in blood pressure. Renin is an enzyme that plays a role in regulating blood pressure. When blood pressure drops, the kidneys detect this decrease and respond by releasing renin. Renin then initiates a series of reactions that ultimately lead to the production of angiotensin II, a hormone that helps to increase blood pressure. Therefore, a decrease in blood pressure triggers the release of renin to help restore and maintain normal blood pressure levels.

Alcohol acts as a diuretic because it inhibits the release of ADH. ADH, or antidiuretic hormone, is responsible for regulating the amount of water reabsorbed by the kidneys. When alcohol is consumed, it suppresses the release of ADH, leading to increased urine production and a decrease in water reabsorption. This can result in dehydration and increased frequency of urination.

As individuals age, their kidney function tends to decrease due to kidney atrophy. This means that the kidneys shrink in size and lose some of their filtering capacity. This decline in kidney function can lead to a decrease in the ability to filter waste products from the blood and regulate fluid and electrolyte balance. It is a normal part of the aging process and can contribute to an increased risk of kidney disease and other related health issues in older adults.

The fluid in the glomerular (Bowman's) capsule is similar to plasma in many ways, but it does not contain a significant amount of plasma protein. Plasma proteins, such as albumin and globulin, are large molecules that are usually too big to pass through the filtration barrier of the glomerulus. Therefore, they are not present in significant amounts in the fluid that is filtered into the glomerular capsule. Glucose, electrolytes, and hormones, on the other hand, are all present in the glomerular filtrate and can be reabsorbed by the renal tubules.

The factor favoring filtrate formation at the glomerulus is the glomerular hydrostatic pressure. This pressure is created by the force of blood pushing against the walls of the glomerular capillaries. It is responsible for forcing water and small solutes out of the blood and into the glomerular capsule to form the initial filtrate. Capsular hydrostatic pressure, myogenic mechanism, and colloid osmotic pressure of the blood are not directly involved in the formation of the filtrate at the glomerulus.

The correct answer is that the placenta allows the mother's urinary system to clear the waste from fetal blood. During pregnancy, the placenta acts as a filter, removing waste products from the fetal blood and transferring them to the mother's bloodstream for elimination through her urinary system. This allows the fetal kidneys to remain relatively inactive as the waste is processed by the mother's kidneys.

The renal corpuscle is a part of the kidney responsible for filtering blood and forming urine. It consists of the glomerulus, a network of fenestrated capillaries, and the Bowman's capsule. The efferent arteriole carries blood away from the glomerulus, while the vasa recta is a network of blood vessels that surrounds the nephron. Podocytes are specialized cells in the Bowman's capsule that help with filtration. The only option that is not associated with the renal corpuscle is the vasa recta, as it is not a component of the corpuscle but rather surrounds the nephron.

The male urethra serves both the urinary and reproductive systems but at different times.

The proximal convoluted tubule is responsible for reabsorbing most of the filtered substances back into the bloodstream. However, creatinine is not reabsorbed by the proximal convoluted tubule and is instead excreted in the urine. This is because creatinine is a waste product of muscle metabolism and does not have any significant physiological function in the body. Therefore, it is not necessary for the body to reabsorb creatinine and it is eliminated through the urine.

Urine specific gravity or density refers to the concentration of solutes in urine. A specific gravity range of 1.001-1.035 is considered normal for urine. This range indicates that the urine is neither too dilute nor too concentrated, suggesting a healthy balance of water and solutes in the body.

The urinary bladder is composed of transitional epithelium. This type of epithelium is specialized to stretch and accommodate changes in volume. The transitional epithelium allows the bladder to expand as it fills with urine and then contract as it empties. This type of epithelium is also found in other organs of the urinary system, such as the ureters and the urethra, where it allows for the passage of urine without damage to the underlying tissues.

ADH, or antidiuretic hormone, is responsible for facultative water reabsorption. This hormone is produced by the hypothalamus and released by the pituitary gland in response to low blood volume or high blood osmolality. ADH acts on the collecting ducts in the kidneys, increasing their permeability to water and allowing for the reabsorption of water back into the bloodstream. This helps to conserve water and prevent dehydration.

The mechanism that establishes the medullary osmotic gradient depends most on the permeability properties of the loop of Henle. The loop of Henle plays a crucial role in the reabsorption of water and solutes from the filtrate. It creates a concentration gradient in the medulla of the kidney, with the descending limb allowing water to passively leave the tubule and the ascending limb actively transporting ions out of the tubule. This concentration gradient is essential for the reabsorption of water in the collecting ducts and the production of concentrated urine.

An increase in the production of ADH (antidiuretic hormone) causes an increase in the permeability of the cells of the collecting tubule to water. ADH acts on the collecting tubule to make it more permeable to water, allowing for increased reabsorption of water from the urine back into the bloodstream. This results in a decrease in urine output and helps to conserve water in the body.

The stretching of the bladder wall acts as the trigger for the initiation of micturition (voiding). When the bladder becomes stretched due to the accumulation of urine, sensory receptors in the bladder wall send signals to the brain, indicating the need to empty the bladder. This triggers the micturition reflex, leading to the contraction of the bladder muscles and relaxation of the urinary sphincters to allow urine to be expelled from the body.

The filtration membrane is a structure in the kidney responsible for filtering waste products from the blood. It consists of three layers: the basement membrane, glomerular endothelium, and podocytes. The basement membrane acts as a physical barrier, preventing the passage of large molecules. The glomerular endothelium is a layer of cells that allows for the passage of small molecules. Podocytes are specialized cells that wrap around the glomerular capillaries and help regulate the filtration process. Renal fascia, on the other hand, is a layer of connective tissue that surrounds and supports the kidney, but it is not a part of the filtration membrane.

The correct sequence of the formation and elimination of a drop of urine from the body is as follows: First, the nephron filters the blood and produces urine. Then, the collecting duct carries the urine to the minor calyx. From the minor calyx, the urine moves to the major calyx. Next, it passes through the ureter, which transports it to the bladder. Finally, the urine is eliminated from the body through the urethra. Therefore, the correct answer is 3, 6, 2, 1, 5, 4.

If one says that the clearance value of glucose is zero, it means that normally all the glucose is reabsorbed. This implies that none of the filtered glucose is excreted in the urine, as it is efficiently reabsorbed by the convoluted tubules in the kidneys.

The urinary system is responsible for maintaining homeostasis by controlling the composition, volume, and pressure of blood. It also helps maintain blood osmolarity and regulates blood glucose levels by producing hormones. However, the elimination of solid, undigested wastes and excretion of carbon dioxide, water, salts, and heat is primarily the function of the digestive and respiratory systems, not the urinary system.

Angiotensin II is a hormone that is released in response to low blood pressure or low blood volume. Its main function is to constrict arterioles, which are small blood vessels, causing them to narrow. This narrowing increases resistance to blood flow and ultimately increases blood pressure. Therefore, the correct answer is that angiotensin II constricts arterioles and increases blood pressure.

Diabetes insipidus is a disease caused by inadequate secretion of antidiuretic hormone (ADH) by the pituitary gland. This hormone helps regulate the amount of water reabsorbed by the kidneys, so when there is a deficiency of ADH, excessive amounts of dilute urine are produced, leading to symptoms of polyuria (excessive urination). Diabetic acidosis is a condition associated with high levels of ketones in the blood, diabetes mellitus is a chronic condition characterized by high blood sugar levels, and coma is a state of unconsciousness.

The correct answer is that the ureters are trilayered (mucosa, muscularis, and adventitia). This means that they have three distinct layers: the innermost mucosa, which is responsible for absorption and secretion; the middle muscularis, which consists of smooth muscle and allows the ureters to contract and propel urine; and the outer adventitia, which provides structural support. This trilayered structure is important for the efficient transport of urine from the kidneys to the bladder.

The arcuate artery is the correct answer because it is the artery that lies on the boundary between the cortex and medulla of the kidney. The interlobar artery is located within the renal columns, the cortical radiate artery branches off the interlobar artery and enters the cortex, and the lobar artery branches off the interlobar artery and supplies blood to the renal lobes. Therefore, the arcuate artery is the only artery that fits the description given in the question.

The juxtaglomerular apparatus is responsible for regulating blood pressure and the rate of blood filtration by the kidneys. It consists of specialized cells located near the glomerulus in the kidney. These cells monitor the blood pressure and release hormones, such as renin, in response to changes in blood pressure. Renin helps regulate blood pressure by initiating the production of angiotensin II, a hormone that constricts blood vessels and increases blood volume. This mechanism helps maintain a stable blood pressure and controls the rate of blood filtration in the kidneys.

The glomerulus is a network of capillaries located in the kidney. It is unique because it is drained by an efferent arteriole, which carries blood away from the glomerulus. This is different from other capillaries in the body, which are typically drained by venules. The efferent arteriole helps to maintain a high pressure within the glomerulus, allowing for the filtration of blood and the formation of urine.

The correct answer is that in the ascending limb of the loop of Henle, the thick segment moves ions out into interstitial spaces for reabsorption. This is because the ascending limb of the loop of Henle is impermeable to water, but actively transports ions such as sodium and chloride out of the tubular fluid and into the interstitial spaces. This creates a concentration gradient that allows for the reabsorption of water in the descending limb of the loop of Henle.

The descending limb of the loop of Henle contains fluid that becomes more concentrated as it moves down into the medulla. This is because the descending limb is permeable to water, allowing water to leave the tubule by osmosis. As water leaves, the concentration of solutes in the tubule increases, leading to a more concentrated fluid in the medulla.

The Tm (transport maximum) is the maximum rate at which a substance can be reabsorbed by the renal tubules. If the concentration of a substance in the blood exceeds the Tm, the excess amount will not be reabsorbed and will instead appear in the urine. In this case, the concentration of the amino acid (230 mg/100 ml) exceeds its Tm (120 mg/100 ml), indicating that it will be excreted in the urine.

The correct statement is that kidneys develop from urogenital ridges. During embryonic development, the urogenital ridges give rise to the kidneys. The kidneys develop from the intermediate mesoderm and undergo a complex process of differentiation and morphogenesis to form the functional organs. The metanephric ducts, on the other hand, give rise to the ureters, not the urethras. The mesonephros is a temporary kidney structure that is replaced by the metanephros during development. The pronephros is the first tubule system to develop, but it occurs earlier in gestation, not during the tenth week.

If the capsular hydrostatic pressure were increased above normal, it would create a greater force pushing fluid out of the glomerulus and into the Bowman's capsule. This increased pressure would lead to an increased rate of filtration. However, as the question asks about the overall effect, it is important to consider other factors. The increase in filtration would cause a greater loss of fluid and solutes, leading to a decrease in net filtration. Therefore, the correct answer is that net filtration would decrease.

The juxtaglomerular apparatus is a structure located in the kidney that regulates blood pressure and filtration. It consists of granular cells, mesangial cells, and macula densa. Granular cells secrete the enzyme renin, which helps regulate blood pressure. Mesangial cells provide structural support to the glomerulus and help regulate blood flow. Macula densa cells are specialized cells in the distal tubule that monitor the concentration of sodium and chloride in the filtrate. Podocyte cells, on the other hand, are located in the glomerulus and play a role in filtration by forming a filtration barrier. Therefore, podocyte cells are not a part of the juxtaglomerular apparatus.

Secondary active transport is the correct answer because it involves the movement of molecules across a cell membrane using energy from an electrochemical gradient established by primary active transport. In this case, high levels of glucose and amino acids are reabsorbed from the filtrate against their concentration gradient, which requires energy. Therefore, secondary active transport is the process by which this reabsorption occurs.

The ureters are capable of peristalsis like that of the gastrointestinal tract. Peristalsis is the wave-like muscle contractions that help propel urine from the kidneys to the bladder. This movement is essential for the proper functioning of the urinary system and the elimination of waste from the body. The other statements are incorrect because the ureters are not innervated by parasympathetic nerve endings only, they contain sphincters to prevent backflow, and their epithelium is not stratified squamous like the skin.

The macula densa is the part of the nephron that monitors the salt level. It is located in the distal convoluted tubule, which is the last part of the nephron before it connects to the collecting duct. The macula densa is responsible for sensing the concentration of sodium chloride in the filtrate and signaling the juxtaglomerular cells to release renin, which helps regulate blood pressure and fluid balance. The other choices, such as vasa recta, principal cell, and loop of Henle, are not directly involved in salt level monitoring.

The loop of Henle is responsible for forming a large volume of very dilute urine or a small volume of very concentrated urine. This is achieved through the process of actively absorbing electrolytes and allowing for the automatic absorption of water by osmosis.

The reason why substances are either not reabsorbed or are incompletely reabsorbed from the nephron is not because they are extremely complex molecules. The other options provided are valid reasons for substances not being reabsorbed or being incompletely reabsorbed.

The statement that is correct is that reabsorption of water is hormonally controlled. This means that the amount of water that is reabsorbed by the kidney and returned to the bloodstream is regulated by hormones. Hormones such as antidiuretic hormone (ADH) and aldosterone play a role in controlling the reabsorption of water in the kidney tubules. These hormones signal the kidneys to either retain water or excrete it, depending on the body's hydration needs.

Tubular reabsorption refers to the process in which substances are reabsorbed from the renal tubules back into the bloodstream. This process is usually carried out by active mechanisms, meaning that energy is required. Additionally, the movement of substances during tubular reabsorption occurs against an electrical and/or chemical gradient, meaning that substances are being moved from an area of lower concentration to an area of higher concentration. This helps to ensure that necessary substances are retained in the body while waste products are eliminated.

Electrolyte reabsorption in the renal tubules is primarily controlled by hormones in the distal tubule segments. This means that the reabsorption of electrolytes such as sodium, potassium, and calcium is regulated by hormones like aldosterone and antidiuretic hormone (ADH) in these specific regions of the tubules. The distal tubule is responsible for fine-tuning the reabsorption and excretion of electrolytes, under the influence of hormonal signals. This ensures that electrolyte balance is maintained in the body by adjusting the amount of reabsorption based on the body's needs.

The parietal layer of the glomerular capsule is simple squamous epithelium. This means that it is composed of a single layer of flat cells. This is important because the parietal layer of the glomerular capsule forms the outer wall of the capsule, while the inner wall is formed by the visceral layer, which consists of specialized cells called podocytes. The simple squamous epithelium of the parietal layer allows for the passive diffusion of substances into the capsule, while the podocytes help to regulate the filtration process by forming filtration slits.

The macula densa cells are specialized cells located in the kidney that monitor the solute content of the filtrate. They respond to changes in the concentration of solutes in the filtrate by releasing chemical signals that regulate the function of the nearby juxtaglomerular cells. These juxtaglomerular cells then adjust the production and release of renin, a hormone that plays a crucial role in regulating blood pressure and fluid balance in the body. Therefore, the macula densa cells play a key role in maintaining homeostasis by responding to changes in solute content of the filtrate.

The cells of the renal tubules can raise blood pH by secreting hydrogen ions into the filtrate, by producing new bicarbonate ions, and by reabsorbing filtered bicarbonate ions. However, secreting sodium ions does not directly contribute to raising blood pH. Sodium ions are involved in the reabsorption process but do not directly affect blood pH levels.