STOMACH

WHAT IS THE STOMACH?

• J-shaped, pouch like organ that hangs inferior to diaphragm
• Capacity of about 1+ liter
• Receives food from the esophagus, mixes the food with gastric juice,
• Initiates protein digestion, moves food into SI

PARTS OF THE STOMACH

• Stomach divided into 4
• 1. Cardiac region is a small area near the esophageal opening
• 2. Fundic region, temporary storage area
• 3. Body region, main part of stomach
• 4. Pyloric region narrows and becomes pyloric canal

CONT.

• Pyloric sphincter, powerful circular muscle
• Controls gastric emptying

GASTRIC SECRETIONS

• Mucous membrane- thick inner lining of stomach
• Studded with many gastric pits
• Gastric pits- end of tubular gastric glands

CONT.

• Gastric glands have three secretory glands
• 1. Mucous cells(goblet cells) located in neck of glands
• 2. Chief cells secrete digestive enzymes
• 3. Parietal cells release hydrochloric acid
• Products of cells make gastric juice

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CONT.

• Pepsin- enzyme in gastric juice, begins digestion
• of dietary protein into polypeptide strands
• Pepsinogen- combined with hydrochloric acid
• makes pepsin

CONT.

• Mucous cells secrete copious thin mucous
• Gastric glands secrete viscous and alkaline secretion
• Coats the inside of stomach
• prevents stomach eating itself

CONT.

• Intrinsic factor- component of gastric juice
• Secreted by parietal cells
• Helps small intestine absorb B12

REGULATION OF GASTRIC SECRETIONS

• Parasympathetic nerve impulses stimulate Ach
• Ach=acetylcholine
• Ach stimulates gastric glands to secrete their juice
• Parasympathetic nerves also stimulate some stomach cells
• to release gastrin which increases secretory activity in gastric glands

GASTRIC ABSORPTION

• Gastric enzymes break down proteins
• Stomach wall ->absorbs small volumes
• Water, certain salts, alcohol,
• and some lipid-soluble drugs

Mixing and Emptying actions

• mixing movements of stomach wall aid producing semifluid 
• paste of food particles and gastric juice called chyme 
• peristaltic waves push chyme toward pyloric region 
• muscle relaxes as chyme accumulates near pyloric sphincter
• stomach contractions push chyme little at a time into SI

CONT.

• Liquids pass through quickly
• Solids remain until mixed with gastric juice
• Fatty foods-> 3-6 hours in stomach
• Foods high in proteins move quickly
• Carbs are faster than fats or proteins

cont.

• chyme enters duodenum (first portion of SI)
• accessory organs, pancreas, liver,
• and gallbladder add their secretions