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Physiology

Renal

Question 42 of 180

What is the role of the macula densa cells of the juxtaglomerular apparatus:

Answer:

The macula densa is an area of specialised cells located between the end of the thick ascending loop of Henle and the start of the distal convoluted tubule which respond to changes in the composition of the tubular fluid (particularly changes in the concentration of Na+ ions).

Juxtaglomerular Apparatus

Physiology / Renal / Functional Anatomy

Last Updated: 29th July 2024

The juxtaglomerular apparatus (JGA) is located where the renal tubule passes back up into the cortex and lies adjacent to the renal corpuscle and arterioles of its own nephron.

Cell Types

The juxtaglomerular apparatus consists of three main cell types:

  • Juxtaglomerular (granular) cells
  • Macula densa tubular cells
  • Extraglomerular mesangial cells

Juxtaglomerular cells are specialised smooth muscle cells found mainly in the walls of the afferent arterioles which synthesise renin.

The macula densa is an area of specialised columnar tubular epithelial cells located at the junction of the thick ascending limb of the loop of Henle and the early distal tubule which senses and responds to changes in tubular ion concentration (particularly changes in the concentration of Na+ ions).

Contractile extraglomerular mesangial cells are found outside the glomerulus in association with the JGA. Their role is uncertain.

By M•Komorniczak -talk- (polish Wikipedist) Illustration by : Micha? Komorniczak This file has been released into the Creative Commons 3.0. Attribution-ShareAlike (CC BY-SA 3.0) If you use on your website or in your publication my images (either original or modified), you are requested to give me details: Micha? Komorniczak (Poland) or Michal Komorniczak (Poland). For more information, write to my e-mail address: m.komorniczak.pl@gmail.com [CC BY-SA 3.0 , via Wikimedia Commons

Juxtaglomerular Apparatus. (Image by MKomorniczak -talk- (polish Wikipedist) [CC BY-SA 3.0 , via Wikimedia Commons)

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  • Biochemistry
  • Blood Gases
  • Haematology
Biochemistry Normal Value
Sodium 135 – 145 mmol/l
Potassium 3.0 – 4.5 mmol/l
Urea 2.5 – 7.5 mmol/l
Glucose 3.5 – 5.0 mmol/l
Creatinine 35 – 135 μmol/l
Alanine Aminotransferase (ALT) 5 – 35 U/l
Gamma-glutamyl Transferase (GGT) < 65 U/l
Alkaline Phosphatase (ALP) 30 – 135 U/l
Aspartate Aminotransferase (AST) < 40 U/l
Total Protein 60 – 80 g/l
Albumin 35 – 50 g/l
Globulin 2.4 – 3.5 g/dl
Amylase < 70 U/l
Total Bilirubin 3 – 17 μmol/l
Calcium 2.1 – 2.5 mmol/l
Chloride 95 – 105 mmol/l
Phosphate 0.8 – 1.4 mmol/l
Haematology Normal Value
Haemoglobin 11.5 – 16.6 g/dl
White Blood Cells 4.0 – 11.0 x 109/l
Platelets 150 – 450 x 109/l
MCV 80 – 96 fl
MCHC 32 – 36 g/dl
Neutrophils 2.0 – 7.5 x 109/l
Lymphocytes 1.5 – 4.0 x 109/l
Monocytes 0.3 – 1.0 x 109/l
Eosinophils 0.1 – 0.5 x 109/l
Basophils < 0.2 x 109/l
Reticulocytes < 2%
Haematocrit 0.35 – 0.49
Red Cell Distribution Width 11 – 15%
Blood Gases Normal Value
pH 7.35 – 7.45
pO2 11 – 14 kPa
pCO2 4.5 – 6.0 kPa
Base Excess -2 – +2 mmol/l
Bicarbonate 24 – 30 mmol/l
Lactate < 2 mmol/l

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