Afferent arteriole

Definition

The afferent arteriole is a small blood vessel that carries oxygenated blood from the renal artery to the glomerulus of the nephron in the kidney. This structure plays a crucial role in regulating blood flow and filtration rates within the nephron, ensuring proper kidney function. Its diameter and resistance are key factors in controlling glomerular filtration pressure and, consequently, urine formation.

5 Must Know Facts For Your Next Test

1. The afferent arteriole adjusts its diameter in response to changes in blood pressure and the body's needs, which helps regulate glomerular filtration rate.
2. Constriction of the afferent arteriole reduces blood flow to the glomerulus, thereby decreasing filtration pressure and urine output.
3. The renal autoregulation mechanism ensures stable glomerular filtration despite fluctuations in systemic blood pressure, partly by adjusting the resistance of the afferent arteriole.
4. Renin, an enzyme released by the juxtaglomerular cells located near the afferent arteriole, plays a key role in blood pressure regulation and fluid balance.
5. Any dysfunction or damage to the afferent arteriole can lead to impaired kidney function, which may result in conditions such as hypertension or chronic kidney disease.

Review Questions

• How does the afferent arteriole contribute to the regulation of glomerular filtration rate?
  • The afferent arteriole contributes to regulating glomerular filtration rate (GFR) by adjusting its diameter in response to blood pressure changes. When blood pressure increases, the afferent arteriole can constrict to reduce blood flow to the glomerulus, thereby preventing excessive filtration. Conversely, if blood pressure drops, it can dilate to increase blood flow and maintain adequate GFR. This dynamic control is essential for proper kidney function and fluid balance.
• Discuss the relationship between the afferent and efferent arterioles in maintaining kidney function.
  • The afferent and efferent arterioles work together to maintain kidney function by controlling blood flow through the nephron. The afferent arteriole supplies blood to the glomerulus for filtration, while the efferent arteriole carries away the filtered blood. Changes in resistance in either arteriole impact glomerular pressure; for instance, constriction of the efferent arteriole can increase pressure within the glomerulus, enhancing filtration rates. This coordinated action ensures effective waste removal and fluid homeostasis.
• Evaluate how alterations in the function of the afferent arteriole can affect overall renal health.
  • Alterations in afferent arteriole function can significantly impact overall renal health by disrupting normal glomerular filtration and fluid balance. For example, if there is constriction due to chronic stress or diseases like hypertension, this can lead to decreased GFR, resulting in inadequate waste removal and potential toxin accumulation. On the other hand, excessive dilation may lead to increased GFR but could also stress kidney structures over time. Both scenarios could contribute to chronic kidney disease or acute kidney injury, highlighting the importance of afferent arteriole regulation for kidney health.

Related terms

glomerulus: A cluster of tiny blood vessels (capillaries) located within the nephron, where blood filtration occurs.

efferent arteriole: The blood vessel that carries filtered blood away from the glomerulus to the peritubular capillaries.

renal corpuscle: The structural unit of the nephron that consists of the glomerulus and Bowman's capsule, where initial filtration of blood takes place.