Question

6. Describe the three types of secretory cells in the stomach: chief, parietal, and mucous cells. Review the role of pepsinogen, hydrochloric acid, intrinsic factor, and prostaglandins in digestion.

7. Describe the effect of stress on the GI diseases GERD and PUD.

8. Describe the signs and symptoms of GI disorders seen in older patients and young adult patients.
9. Describe the difference between GERD and PUD
10. Describe the body’s natural mechanisms for protecting the stomach walls from injury. Include a description of the three types of secretory cells that line portions of the stomach and the role of prostaglandins.

Answer 1

Three types of secretory cells:

Chief cells : The gastric chief cell (also known as a zymogenic cell or peptic cell) is a cell in the stomach that releases pepsinogen and chymosin. Pepsinogen is activated into the digestive enzyme pepsin when it comes in contact with acid produced by gastric parietal cells.

Parietal - The parietal cells are located in the middle part of the glands of the fundus-body region of the stomach. They secrete gastric acid, i.e. hydrochloric acid and secrete the intrinsic factor, which is a vitamin B12-binding protein.

Mucous - Foveolar cells or surface mucous cells are mucus-producing cells which cover the inside of the stomach, protecting it from the corrosive nature of gastric acid. These cells line the gastric mucosa (mucous neck cells are found in the necks of the gastric pits).

Role of this substances in digestion.

Pepsinogen : Pepsin is a stomach enzyme that serves to digest proteins found in ingested food. Gastric chief cells secrete pepsin as an inactive zymogen called pepsinogen. Parietal cells within the stomach lining secrete hydrochloric acid that lowers the pH of the stomach.

Hydrochloric acid : Hydrochloric acid activates pepsinogen into the enzyme pepsin, which then aids digestion by breaking the amino acid bonds, a process called proteolysis. In addition, many microorganisms are inhibited or destroyed in an acidic environment, preventing infection or sickness.

Intrinsic factor - The intrinsic factor (IF) is a glycoprotein produced by the parietal cells (oxyntic cells) located at the gastric body and fundus. Intrinsic factor plays a crucial role in the transportation and absorption of the vital micronutrient vitamin B12 (cobalamin, Cbl) by the terminal ileum.

Prostaglandins - Prostaglandins are found in high concentration in the gastric mucosa and gastric juice. Exogenous prostaglandins inhibit acid secretion, stimulate mucus and bicarbonate secretion, alter mucosal blood flow, and provide dramatic protection against a wide variety of agents which cause acute mucosal damage.

Effect of stress on Gi diseases:

Stress especially affects people with chronic bowel disorders, such as Inflammatory Bowel Disease or Irritable Bowel Syndrome. This may be due to the gut nerves being more sensitive, changes in gut microbiota, changes in how quickly food moves through the gut, and/or changes in gut immune responses.

Signs and symptoms of Gi diseases:

The first sign of problems in the digestive tract often includes one or more of the following symptoms:

Bleeding.

Bloating.

Constipation.

Diarrhea.

Heartburn.

Incontinence.

Nausea and vomiting.

Pain in the belly.

Difference between GERD and PUD

GERD : A digestive disease in which stomach acid or bile irritates the food pipe lining.

This is a chronic disease that occurs when stomach acid or bile flows into the food pipe and irritates the lining. Acid reflux and heartburn more than twice a week may indicate GERD.

PUD : A sore that develops on the lining of the oesophagus, stomach or small intestine.

Ulcers occur when stomach acid damages the lining of the digestive tract. Common causes include the bacteria H. Pylori and anti-inflammatory pain relievers including aspirin.

Natural protecting mechanisms :

In the stomach several mucosal defence mechanisms protect the stomach against hydrochloric acid and noxious agents. The pre-epithelial protection is made up by the mucus-bicarbonate barrier. Mucus and bicarbonate, secreted by mucus cells, create a pH gradient maintaining the epithelial cell surface at near neutral pH.