Which of the following is a primary factor that directly influences the rate of glomerular filtration in the kidneys?

• A. Renal medullary osmolarity
• B. Ureteral peristalsis
• C. Plasma glucose concentration
• D. Glomerular hydrostatic pressure

Answer: (D)

Verified step by step guidance

1. Understand the concept of glomerular filtration: Glomerular filtration is the process by which the kidneys filter blood, removing waste and excess substances to form urine. The rate of filtration is influenced by pressures within the glomerulus.
2. Identify the primary factor influencing glomerular filtration: The glomerular hydrostatic pressure is the force exerted by blood within the glomerular capillaries. This pressure drives the movement of fluid and solutes from the blood into the Bowman's capsule.
3. Eliminate irrelevant factors: Renal medullary osmolarity, ureteral peristalsis, and plasma glucose concentration do not directly affect the rate of glomerular filtration. These factors are involved in other kidney functions, such as urine concentration or glucose reabsorption.
4. Relate glomerular hydrostatic pressure to filtration rate: Higher glomerular hydrostatic pressure increases the rate of filtration, while lower pressure decreases it. This pressure is influenced by systemic blood pressure and the resistance in afferent and efferent arterioles.
5. Summarize the importance of glomerular hydrostatic pressure: It is the primary driving force for filtration in the kidneys, ensuring that waste products and excess substances are efficiently removed from the blood.