Gastric juice-The course is designed for the basic understanding of anatomical structures and physiological functions of human body, musculoskeletal system, digestive system, respiratory system; cardiovascular system; urinary system, endocrine system, reproductive system, nervous system, hematologic system, sensory organs, integumentary system, and immune system.The aim of the course is to acquire knowledge and skills regarding anatomy and physiology.
Gastric juice
Composition of gastric juice
A. Water : 99.5%
B. Solids : 0.5%
a) Organic constituent:
- Pepsinogen.
- Gastric lipase & amylase.
- Mucin.
- Intrinsic factor of Castle.
b) Electrolytes (inorganic constituent):
1. Hydrochloric acid (HCI).
2. Cation: Na+, K+, H+ etc.
3. Anion: CI, SO4″ etc.
(Ref: Ganong, 23 edition, P-433)
Digestive juices
| Name of D. Juices | Daily secretion | P^H |
| 1. Saliva | 1000 ml | 6.0 – 7.0 |
| 2. Gastric juice | 1500 ml | 1.0 – 3.5 |
| 3. Pancreatic juice | 1000 ml | 8.0 – 8.3 |
| 4. Bile | 1000 ml | 7.8 |
| 5. Small intestinal juice | 1800 ml | 7.5 – 8.0 |
| 6. Brunners gland secretion | 200 ml | 8.0 – 8.9 |
| 7. Large intestinal juice | 200 ml | 7.5 – 8.0 |
(Ref: Guyton & Hall, 12th, edition, P-775).
Digestive activities occur in three overlapping phases:
A. The cephalic phase,
B. The gastric phase, and
C. The intestinal phase,
A. Cephalic Phase
1. Sight, smell, and taste of food cause stimulation of vagus nuclei in brain
2. Vagus stimulates acid secretion
- a. Indirect stimulation of parietal cells (major effect)
- b. Stimulation of gastrin secretion (lesser effect)
B. Gastric Phase
1. Distension of stomach stimulates vagus nerve; vagus stimulates acid secretion 2.
2. Amino acids and peptides in stomach lumen stimulate acid secretion
- a. Direct stimulation of parietal cells (lesser effect)
- b. Stimulation of gastrin secretion; gastrin stimulates acid secretion (major effect)
3. Gastrin secretion inhibited when pH of gastric juice falls below 2.5
C. Intestinal Phase
1. Neural inhibition of gastric emptying and acid secretion
- a. Arrival of chyme in duodenum causes distension, increase in osmotic pressure
- b. These stimuli activate a neural reflex that inhibits gastric activity
2. In response to fat in chyme, duodenum secretes a hormone that inhibits gastric acid secretion
(Ref:-Stuart Ira Fox, Pierce College, Human Physiology-12th edition, P-638)
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