Stenosis is the abnormal narrowing of a tubular structure in the body, such as a blood vessel. Stenosis of the afferent arterioles in the kidney would be expected to:

Question

Stenosis is the abnormal narrowing of a tubular structure in the body, such as a blood vessel.  Stenosis of the afferent arterioles in the kidney would be expected to:

Quizplus · Accepted Answer

11ecba2d_0fd0_a806_a3bf_cbee5608d7ee_MD0008_00 The kidneys are composed of functional units called nephrons. In nephrons, the glomerular capillaries (which are collectively known as the glomerulus), Bowman's capsule, the renal tubule, and the collecting duct work together to filter blood and concentrate the waste products as urine. Blood is filtered in the glomerulus by high hydrostatic (blood) pressure, which forces excess fluid and waste products (filtrate) across the porous endothelium and into Bowman's space. Proteins and cells are too large to pass through the pores. The volume of fluid filtered through the kidney per unit time is known as the glomerular filtration rate (GFR). Circulating blood enters the glomerulus through the afferent arteriole and exits through the efferent arteriole. The degree of vascular constriction of these two arterioles controls the rate of blood flow into and out of the glomerulus, thereby affecting the GFR through changes in glomerular hydrostatic pressure. According to the question, stenosis is an abnormal narrowing of a blood vessel, a condition that mimics the physiological effect of vasoconstriction. As a result, stenosis of the afferent arteriole would limit the amount of blood reaching the glomerulus, leading to decreased glomerular hydrostatic pressure and, consequently, a decreased GFR. (Choices B and C) The tendency of the body to oppose flow is known as resistance. Stenosis, or narrowing, of the afferent arteriole would cause an increase in resistance because of the reduced diameter of the afferent arteriole. When resistance within the afferent arteriole is increased, blood flow to the glomerulus is expected to decrease. (Choice D) Urine production is influenced by the GFR, the rate of reabsorption (movement of substances from the filtrate back into the bloodstream), and the rate of secretion (movement of substances from the bloodstream to the filtrate). When GFR decreases, as it does due to stenosis of the afferent arteriole, less filtrate is produced, and urine output decreases. Educational objective: The volume of fluid filtered through the kidney per unit time is known as the glomerular filtration rate (GFR), which can be modulated by controlling blood flow through the glomerulus. Higher hydrostatic (blood) pressure in the glomerulus increases GFR, and lower hydrostatic pressure decreases GFR.

Stenosis Is the Abnormal Narrowing of a Tubular Structure in the Body