Macula densa

Definition

The macula densa is a group of specialized cells located in the distal convoluted tubule of the nephron. These cells detect sodium concentration in the filtrate and regulate glomerular filtration rate (GFR) through signaling mechanisms.

5 Must Know Facts For Your Next Test

1. 1. Macula densa cells sense changes in sodium chloride concentration in the tubular fluid.
2. 2. They play a crucial role in the tubuloglomerular feedback mechanism to maintain GFR.
3. 3. When low sodium levels are detected, macula densa cells signal juxtaglomerular cells to release renin.
4. 4. Renin release leads to the activation of the renin-angiotensin-aldosterone system (RAAS), which increases blood pressure and sodium reabsorption.
5. 5. High sodium levels cause macula densa cells to send signals that lead to afferent arteriole constriction, reducing GFR.

Review Questions

• 1. What primary function do macula densa cells serve within the nephron?
• 2. How do macula densa cells respond to low sodium chloride concentrations?
• 3. Explain how macula densa cells influence the renin-angiotensin-aldosterone system (RAAS).

Related terms

Juxtaglomerular Apparatus: A complex structure formed by the distal convoluted tubule and glomerular afferent arteriole, playing a key role in blood pressure regulation

Renin: An enzyme secreted by juxtaglomerular cells that initiates the RAAS pathway to increase blood pressure

Glomerular Filtration Rate (GFR): A measure of how much blood is filtered by the glomeruli each minute, essential for assessing kidney function