What is a granular growth or tumor?

Granular cell tumor is a tumor that can develop on any skin or mucosal surface, but occurs on the tongue 40% of the time. It is also known as Abrikossoff’s tumor, Granular cell myoblastoma, Granular cell nerve sheath tumor, and Granular cell schwannoma.) Granular cell tumors (GCTs) affect females more often than males.

What do the macula densa cells respond to?

It is thought that the macula densa cells are sensory cells that respond to the sodium concentration in the fluid within the distal tubule and, perhaps, to the rate of fluid flow past them.

Is granular cell tumor common?

Granular cell tumours (GrCTs) are uncommon soft tissue tumours that are usually benign (approximately 0.5%–2.0% have been reported as malignant). They are very rarely found at the extremities.

What does a granular cell tumor look like?

A granular cell tumour is most often a solitary, small (usually 1–3c m), and painless. Occasionally mild itch or tenderness is described. They usually appear as a slowly growing skin coloured nodule with a smooth or slightly rough surface.

Why is the macula densa called the macular densa?

The cells of the macula densa are taller and have more prominent nuclei than surrounding cells of the distal straight tubule (cortical thick ascending limb). The close proximity and prominence of the nuclei cause this segment of the distal tubule wall to appear darker in microscopic preparations, hence the name macula densa .

How do macula densa cells inhibit renin release?

Macula-densa cells may signal granular cells to inhibit renin release by secreting adenosine and/or ATP across the basolateral membrane in response to increased sodium delivery [96, 101, 102]. The precise mechanism of this effect is not clear. Adenosine stimulates granular-cell A 1 and A 2 receptors.

Why is there less sodium in the macula densa of the eye?

This results in a smaller capillary hydrostatic pressure, which causes an increased absorption of sodium ions into the vasa recta at the proximal tubule. Hence, a decrease in blood pressure results in less sodium chloride present at the distal tubule, where the macula densa is located.

How does a decrease in afferent arteriole diameter affect macula densa cells?

Macula densa cells sense changes in sodium chloride level, and will trigger an autoregulatory response to increase or decrease reabsorption of ions and water to the blood (as needed) in order to alter blood volume and return blood pressure to normal. A decrease in afferent arteriole diameter causes a decrease in the GFR…