Physiology
Renal
Regarding the nephrons, which of the following statements is INCORRECT:
Answer:
All nephrons have their renal corpuscles in the renal cortex. Cortical nephrons have their renal corpuscles in the outer part of the cortex and relatively short loops of Henle. Juxtamedullary nephrons have their corpuscles in the inner third of the cortex, close to the corticomedullary junction, with long loops of Henle extending into the renal medulla.Overview of Nephron
Physiology / Renal / Functional Anatomy
Last Updated: 26th July 2024
Each kidney has about 800,000 nephrons, the functional unit of the kidney. There are two types of nephrons, cortical nephrons (85% of nephrons) and juxtamedullary nephrons (15% of nephrons).
Functional Anatomy
Each nephron consists of a renal corpuscle (Bowman's capsule and glomerulus) and a tubule (proximal tubule, loop of Henle, distal tubule and collecting duct):
- Cortical nephrons have their renal corpuscles in the outer part of the cortex and relatively short loops of Henle.
- Juxtamedullary nephrons have their corpuscles in the inner third of the cortex, close to the corticomedullary junction, with long loops of Henle extending into the renal medulla.
The glomerulus is formed by the invagination of a ball of capillaries into the Bowman's capsule, the blind end of the nephron.
The convoluted proximal tubule continues from the renal corpuscle and straightens before becoming the loop of Henle.
The distal tubule is the continuation of the loop of Henle, ending in the collecting ducts.
The collecting ducts empty into papillary ducts at the apices of the renal pyramids.
Functions
Main functions:
- Glomerulus: Filtration
- Proximal tubule: Reabsorption
- Loop of Henle: Urine concentration
- Distal tubule and collecting duct: Water homeostasis and acid-base balance
Overview of the Nephron. (Image by Holly Fischer [CC BY 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 |
