Gastrointestinal Tract physiology Part 3 Flashcards
(30 cards)
What are the regions of the small intestine?
- Duodenum: Receives chyme, bile, pancreatic enzymes
- Jejunum: Major site for nutrient absorption
- Ileum: Absorbs vitamin B12, bile salts
What is the role of Brunner’s glands in the duodenum?
Secrete alkaline mucus to neutralize stomach acid and protect the duodenal lining
What is the surface area amplification of the small intestine?
• Plicae circulares: Folds of the mucosa
• Villi: Finger-like projections
• Microvilli: Brush border enzymes for digestion and absorption
Where are carbohydrates, proteins, and lipids digested and absorbed in the small intestine?
Carbohydrates: Digested by pancreatic amylase, absorbed in the duodenum/jejunum
• Proteins: Digested by pancreatic proteases, absorbed in the jejunum
• Lipids: Emulsified by bile, digested by lipase, absorbed in the jejunum
What are the functions of the large intestine?
• Absorbs water, electrolytes, and vitamins
• Forms feces
• Houses gut microbiota that ferment undigested carbohydrates and synthesize vitamin K
What are the main types of motility in the large intestine?
• Haustral contractions: Local mixing and water absorption
• Mass movements: Propel fecal matter toward the rectum
What are the functions of the rectum and anal canal in defecation?
• Rectum: Stores feces until defecation
• Anal canal: Regulated by the internal anal sphincter (involuntary) and external anal sphincter (voluntary)
What are the acessory organs?
The accessory organs of the gastrointestinal (GI) tract are organs that aid in digestion but are not part of the main alimentary canal. They produce and secrete substances essential for digestion, such as enzymes, bile, and buffers
What are the Main Accessory Organs of the GI Tract?
- Salivary Glands
- Liver
- Gallbladder
- Pancreas
What is the liver’s primary digestive function in the GI system?
Production and secretion of bile to emulsify fats
What are the two blood supplies to the liver and their proportions?
• Portal vein (75%): nutrient-rich, oxygen-poor blood
• Hepatic artery (25%): oxygen-rich blood
What are the components of the portal triad?
• Portal vein
• Hepatic artery
• Bile duct
What are Kupffer cells and their role?
Liver-resident macrophages that phagocytose pathogens and debris in the sinusoids
What is the function of stellate (Ito) cells?
Store vitamin A; produce fibrosis when activated (e.g., in cirrhosis)
Where is bile secreted?
Hepatocytes secrete bile into tiny channels called bile canaliculi.
What is bile composed of?
• Bile salts (from cholesterol)
• Bilirubin
• Cholesterol
• Phospholipids
• Electrolytes
What stimulates bile release from the gallbladder?
Cholecystokinin (CCK) released in response to fats in the duodenum
What is the primary digestive function of bile?
To emulsify fats, breaking them into small droplets for enzyme action
How does bile aid in fat absorption?
By forming micelles that transport lipids and fat-soluble vitamins to the intestinal lining
Which waste products are excreted in bile?
• Bilirubin (from RBC breakdown)
• Cholesterol
• Toxins and drug metabolites
How does bile help neutralize stomach acid in the duodenum?
Via bicarbonate ions that buffer the acidic chyme
What is one antimicrobial role of bile?
Bile salts disrupt bacterial membranes, limiting harmful gut bacteria
What are bile salts?
Bile salts are amphipathic molecules derived from cholesterol in the liver. They are a major active component of bile and are essential for fat digestion and absorption
