REGULATION OF GASTRIC EMPTYING

REGULATION OF GASTRIC EMPTYING

Gastric emptying is regulated by nervous and hormonal factors.

Nervous Factor

Nervous factor which regulates the emptying of stomach is the enterogastric reflex.

Enterogastric Reflex

Enterogastric reflex is the reflex that inhibits gastric emptying. It is elicited by the presence of chyme in

the duodenum, which prevents further emptying of stomach.

Mechanism of enterogastric reflex

1. Presence of chyme in duodenum causes generation of nerve impulses which are transmitted to stomach by the intrinsic nerve fibers of GI tract. After reaching the stomach, these impulses inhibit emptying.

2. Impulses from duodenum pass via extrinsic sympathetic fibers to stomach and inhibit emptying.

3. Some impulses from duodenum travel through afferent vagal fibers to the brainstem. Normally,

brainstem neurons send excitatory impulses to stomach through efferent vagal fibers and stimulate

gastric emptying. However, the impulses from duodenum inhibit these brainstem neurons and thereby inhibit gastric emptying.

Factors which initiate enterogastric reflex

1. Duodenal distension

2. Irritation of the duodenal mucosa

3. Acidity of the chyme

4. Osmolality of the chyme

5. Breakdown products of proteins and fats.

Hormonal Factors

When an acid chyme enters the duodenum, the duodenal mucosa releases some hormones which

enter the stomach through blood and inhibit the motility of stomach.

Hormones inhibiting gastric motility and emptying

1. Vasoactive intestinal peptide (VIP)

2. Gastric inhibitory peptide (GIP)

3. Secretin

4. Cholecystokinin

5. Somatostatin

6. Peptide YY.

ABNORMAL GASTRIC EMPTYING

1. Gastric Dumping Syndrome

Gastric dumping syndrome or rapid gastric emptying is the condition characterized by series of upper abdominal symptoms. It is due to the rapid or quick dumping of undigested food from stomach into the jejunum. It occurs in patients following partial gastrectomy (removal of stomach) or gastroenterostomy (gastric bypass surgery). The rapid gastric emptying may begin immediately after taking meals (early dumping) or about few hours after taking meals (late dumping).

Causes

i. Gastric surgery.

ii. Zollinger-Ellison syndrome (rare disorder due to severe peptic ulcer and gastrin-secreting tumor

in pancreas).

Symptoms of early dumping

i. Nausea and vomiting

ii. Bloating (increase in abdominal volume with feeling of abdominal fullness and tightness)

iii. Diarrhea

iv. Sweating and weakness

v. Fatigue and dizziness

vi. Fainting and palpitations (sensation of heart beat).

Symptoms of late dumping

i. Hypoglycemia

ii. Sweating and weakness

iii. Dizziness.

2. Gastroparesis

Gastroparesis is a chronic disorder characterized by delayed gastric emptying. It usually occurs as a

secondary disorder, precipitated by a primary cause.

Causes

i. Diabetes mellitus

ii. Postsurgical complications

iii. Motility disorder

iv. Gastric infection

v. Metabolic and endocrine disorder

vi. Decrease in myenteric ganglia (rare).

Symptoms

i. Early satiety (feeling full with small quantity of food)

ii. Nausea

iii. Vomiting

iv. Bloating

v. Upper abdominal discomfort.

 

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