HESI A2 Exam: Genitourinary System
• What prevents fluid loss to maintain blood volume by increasing reabsorption of water from renal tubules?
• What is the glomerulus?
• What is the filtration unit of the kidneys?
• What does vasopressin do?
• What is the function of renin, angiotensin, and aldosterone?
Intro
The genitourinary system is composed of the kidneys, ureters, urinary bladder, and urethra.
The kidneys filter blood to remove waste products and maintain fluid balance. They also produce urine.
The kidneys produce urine and the bladder stores it.
Urine is produced in the collecting ducts of the kidneys, flows into the renal pelvis and then moves into the ureters. The ureters transfer the urine to the urinary bladder, where it is stored, until it is released by the body through the urethra.
Kidneys
The functional unit of the kidney, the nephron, is where blood filtration and reabsorption occur. While there is a range, a healthy kidney would be expected to have around 1 million nephrons.
The kidneys receive blood from the renal arteries, which carry blood directly from the heart via the abdominal aorta. These arteries branch and feed into the glomerulus.
The glomerulus is a network of capillaries that contains pores and makes it highly permeable to certain ions like sodium and potassium.
Bowman's capsule, found at the end of the nephron, surrounds the glomerulus and together they make up the renal corpuscle, which is the filtration unit of the kidney.
The renal corpuscle is composed of the glomerulus and Bowman's capsule. The glomerulus allows the passage of water and solutes into the Bowman's capsule during the process of filtration.
The renal tubule allows salts, water, and amino acids to be reabsorbed.
The kidney concentrates urea in the renal tubules by reabsorbing water from the renal tubules.
The blood enters the renal corpuscle through the afferent arteriole, is filtered through the glomerulus, and exits through the efferent arteriole.
The presence of certain solutes in the urine can indicate certain issues. Glucose in the urine is a sign of diabetes. Dark urine is a sign of dehydration. Blood in the urine could indicate damage to the urinary tract.
Homeostasis
Renin increases secretion of vasopressin and aldosterone and results in increased blood pressure. Renin activates angiotensin and increases secretion of ADH and aldosterone.
Angiotensin, which is activated by renin, also increases blood pressure.
Vasopressin prevents fluid loss to maintain blood volume by increasing reabsorption of water from renal tubules. Vasopressin results in increased blood volume. Vasopressin (also called ADH) acts to increase water reabsorption.
Renin, angiotensin, and aldosterone function to increase blood pressure by inducing either vasoconstriction or the reabsorption of sodium at the distal convoluted tubule.
ADH is released from the pituitary gland in response to decreased blood volume or increased blood concentration. The role of ADH is to regulate fluid balance in the body. ADH is responsible for urine concentration. Only ADH is responsible for urine concentration because it is the only one directly acting on the collecting duct.
Aldosterone increases the reabsorption of sodium from the renal tubules, causing more water to be reabsorbed via osmosis. The trigger for aldosterone is both decreased blood pressure and increased potassium levels.
Renin, angiotensin, and aldosterone function to increase blood pressure by inducing either vasoconstriction or the reabsorption of sodium at the distal convoluted tubule.
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