Digestive System

Primary organ of digestion that chemically processes biomolecules

Stomach

Fundamentals:

Characteristics/Specs:

• Located in the URQ
• Capacity for 2 L
• Gastric and pyloric glands
• Respond to signals from the brain activated by the sight, taste and smell of food

Function/Purpose:

• Processes biomolecules into chyme
  • Combined mechanical and chemical digestive activities INC significantly Surface area of the food particles
    • WHY? Optimize absorption
• 1)Proteins are denatured and degredation
  • WHY?Denaturation renders protein a better substrate
  • Stimulates Cholecystokinin (CCK)
• pH 1-2
• 2)Lipids are initially emulsified

Types of Secretions:

• Mucus

Salient Enzymes and Function Tests:

Enzymes:

• Pepsinogen - Pepsin
  • Pepsin will digest proteins by cleaving peptide bonds near the aromatic rings resulting in short polypeptide fragments
  • pepsin which is most active at pH of 2

Stomach Function Tests and Assessment:

Anatomy:

Gross Anatomy:

• Cardia/Cardiac/Gastroesophageal Sphincter
• Fundus
• Body
• Pylorus
• Pyloric Sphincter

Micro Anatomy:

Molecular

• ATP dependent proton pump similar to Na K ATPase

Cellular

• Mucus/Surface cells - secrete mucus
• Endocrine cells/Pyloric glands - secretes Gastrin
  • Gastrin - stimulates secretion of HCl and Pepsinogen
    • Activates Parietal cells and Chief Cells
• Gastric pits
• Parietal cells - secretes HCl (pH 1)
  • Activates acid initially activates Pepsinogen-Pepsin:ZYM for autocatalysis
  • Prevents most known bact
• Chief cells - secretes Pepsinogen

Concept:

• Surface Area - MATH
• Enzymes - Zymogens/Proenzymes

Terminology:

• Gastric Pit: region where parietal cells and chief cells are located
• Chyme: acidic semifluid mixture

Additional Information:

• [http://en.wikipedia.org/wiki/Stomach#Anatomy of the Stomach Wikiedia