Question

Describe how the motility and secretions of the stomach contribute to the digestive process in a healthy human, making sure that you describe difference between the functional regions of the stomach.

Answer 1

There are four main regions in the stomach:

• cardia
• fundus
• body
• pylorus.

The cardia (or cardiac region) is the area where esophagus connects to the stomach and food enters into the stomach.

Fundus is located above and to the left of the cardia.

Body is the major part which lies below the fundus.

Pylorus is a funnel-shaped region which connects the stomach to the duodenum.

Digestion within the stomach includes both mechanical digestion and chemical digestion

Mechanical digestion

Motility of stomach contributes to digestion in normal healthy human body.

Mechanical digestion involves a process in which physical breaking of the food into small pieces occurs.

When the food reaches stomach, muscles of the stomach wall exhibits prristaltic contractions which results in churning the bolus into chyme.
Peristaltic contraction of smooth muscle from the fundus to the pylorus is termed as propulsion.

By this process, large food particles breaks into small fragments which in turn facilitates the process of enzymatic digestion.

Chemical digestion

There are lots of secretions within the stomach which helps with digestion process.

Enzymes are these secretions which are produced by many gastric glands situated in various parts of the stomach. And there are other compounds also which helps in digestion.

Enzymes secreted into the stomach are collectively called gastric enzymes.

To produce these enzymes and other compounds, there are mainly 4 types of cells in the stomach, which are,

• Parietal cells: produce HCl and intrinsic factor
• Chief cells: Produce pepsinogen& gastric lipase. They are mainly located in body of stomach.
• Mucous neck cells: Produce mucin and bicarbonate ions
• G cells: produce gastrin hormone. They are mostly located in the pyloric antrum.

Function of each of these compounds are:

• Pepsin: main gastric enzyme. It breaks down proteins into peptides and amino acids.
• Gastric lipase: it provides lipolytic activity in an optimum pH of 3-6.
• Hydrochloric acid: It is the stomach acid which destroys bacteria, denatures proteins and activates pepsinogen into pepsin.
• Intrinsic factor: It facilitates vitamin B12 absorption.
• Mucin: Helps to destroy bacteria and viruses
• Gastrin: It stimulates parietal cells to produce HCl and IF.