Physiology
Gastrointestinal
Regarding gastric motility and emptying, which of the following statements is CORRECT:
Answer:
Gastric emptying is decreased by the presence of fats in the duodenum (by stimulating release of cholecystokinin). Mixing of the food with gastric secretions takes place in the distal body and antrum of the stomach where the muscularis externa layer is thicker. The stomach has an additional inner oblique smooth muscle layer (in addition to the inner circular layer and outer longitudinal layer). Gastric emptying is increased by a low gastric pH and decreased by a low duodenal pH.Gastric Emptying
Physiology / Gastrointestinal / Stomach
Last Updated: 21st April 2019
Gastric Motility
Mixing of the food with gastric secretions takes place in the distal body and antrum of the stomach where the muscularis externa layer is thicker. The stomach has an additional inner oblique smooth muscle layer (in addition to the inner circular layer and outer longitudinal layer), allowing peristaltic contractions and thorough mixing. Gastric contractions are increased by vagal stimulation and decreased by sympathetic stimulation.
Gastric Emptying
The presence of chyme in the pyloric antrum distends it and causes antral contractions and opening of the pyloric sphincter. The rate of gastric emptying is regulated, which leads to a precise supply of chyme to the intestine at an appropriate rate for digestion. Gastric emptying varies with different food types; carbohydrates are emptied more quickly, proteins more slowly and fatty foods even more so, liquids empty more rapidly than solid foods.
Gastric emptying is increased by:
- Distension of the pyloric antrum
- A fall in the pH of chyme in the stomach
- Parasympathetic stimulation
Gastric emptying is decreased by:
- Enterogastric inhibitory reflexes stimulated by
- Distension of the duodenum
- The presence of fats in the duodenum (by stimulating release of cholecystokinin)
- A fall in the pH of chyme in the duodenum
- An increase in the osmolality of chyme in the duodenum
- Irritation of the mucosal lining of the duodenum
- Hormones
- Cholecystokinin
- Secretin
Gastric emptying can also be delayed pathologically by mechanical obstruction e.g. tumours or stenosis or by non-mechanical causes e.g. myotonic dystrophy or autonomic neuropathy.
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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 |
