Physiology
Gastrointestinal
Regarding the exocrine pancreas, which of the following statements is CORRECT:
Answer:
The exocrine pancreas secretes a major digestive fluid called pancreatic juice, which is secreted into the duodenum via the pancreatic duct. The pancreas secretes about 1 L of fluid per day. The bulk of the fluid is a sodium and bicarbonate rich hypertonic alkaline fluid secreted by pancreatic ductal cells, which together with secretions from the gallbladder and the intestinal juices, neutralises acid entering the duodenum from the stomach. The acinar cells secrete a small volume of fluid rich in digestive enzymes. The main proteolytic enzymes are trypsin, chymotrypsin, elastase and carboxypeptidase. Most of the proteolytic enzymes are secreted in an inactive proenzyme form to protect the pancreas from autodigestion, and are activated in the duodenum.Function of Exocrine Pancreas
Physiology / Gastrointestinal / Pancreas
Last Updated: 24th August 2023
The exocrine pancreas secretes a major digestive fluid called pancreatic juice, which is secreted into the duodenum via the pancreatic duct. When food is present in the duodenum the sphincter of Oddi relaxes, allowing both bile and pancreatic secretions to enter the duodenum.
Functional Anatomy of the Pancreas. (Image by OpenStax College [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons)
Pancreatic Juice
The pancreas secretes about 1 L of fluid per day. The bulk of the fluid is a sodium and bicarbonate rich hypertonic alkaline fluid secreted by pancreatic ductal cells, which together with secretions from the gallbladder and the intestinal juices, neutralises acid entering the duodenum from the stomach.
Digestive Enzymes
The acinar cells secrete a small volume of fluid rich in digestive enzymes.
These enzymes include:
- Pancreatic amylase
- Pancreatic lipase
- Ribonuclease and deoxyribonuclease
- Proteolytic enzymes including trypsin, chymotrypsin, elastase and carboxypeptidase
Most of the proteolytic enzymes are secreted in an inactive proenzyme form to protect the pancreas from autodigestion, and are activated in the duodenum.
Regulation of Secretions
Pancreatic exocrine secretion is controlled by:
- Parasympathetic stimulation which enhances secretion of both the enzyme and aqueous components
- Sympathetic stimulation which inhibits pancreatic secretion
- Secretin which stimulates secretion of the alkaline-rich fluid from ductal cells
- Cholecystokinin which stimulates secretion of the enzyme-rich fluid from acinar cells
- Somatostatin which inhibits secretion from both acinar and ductal cells
- Gastrin which stimulates pancreatic acinar cells to secrete digestive enzymes
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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 |
