Digestion And Gastro Intestinal System Flashcards
What are the main functions of the gastrointestinal (GI) system?
- Ingestion of food.
- Digestion, mechanical and chemical breakdown of food.
- Absorption of nutrients into the blood stream.
- Elimination of undigested material and waste products.
What are the four layers of the GI tract?
MUCOSA: Inner lining; involved in secretion, absorption, and protection.
SUBMUCOSA: Contains blood vessels, lympatics, and nerves.
MUSCULARIS EXTERNA: Smooth muscle for peristalsis and segmentation.
SEROSA: Outer protective layer.
What is peristalsis and why is it important?
Peristalsis is the rhythmic contraction of smooth muscle in the GI tract, it propels food and liquids through the digestive system.
What role does the stomach play in digestion?
The stomach:
1. Mechanically churns food into chyme.
2. Produces gastric juice containing hydrochloric acid (HCl) and pepsin for protein digestion.
3. Secretes intrinsic factor, essential for vitamin B12 absorption.
What are the three phases of gastric secretion?
CEPHALIC PHASE: Triggered by the sight, smell, or though of food (stimulates gastric secretion).
GASTRIC PHASE: Triggered by food entering the stomach; stimulates gastric release.
INTESTINAL PHASE: Triggered by chime entering the small intestine; inhibits further gastric secretion.
What are the main functions of the small intestine in digestion?
Digestion: Enzymes from the pancreas and bile from the liver breaks down nutrients.
Absorption: Villi and microvilli increase surface area for nutrient Absorption into the bloodstream and lymph.
What enzymes are secreted by the pancreas, and what are their roles?
AMYLASE: Breaks down carbohydrates into simple sugars.
LIPASE: Breaks down lipids into fatty acids and glycerol.
PROTEASES (EG. TRYPSIN): Breaks down proteins into amino acids.
NUCLEASES: Breaks down nucleic acid (DNA/RNA) into nucleotides.
What is bile, and what role does it play in digestion?
Bile is a substance produced by the liver and stored in the gall bladder. It emulsifies fats, breaking them into smaller droplets to aid in lipid digestion by lipase.
What is the function of the large intestine?
The large intestine:
1. Absorbs water and electrolytes from undigested material.
2. Stores and eliminates feces.
3. Houses gut bacteria that synthesise vitamins (eg. Vitamin K, B12).
What is the difference between segmentation and peristalsis?
SEGMENTATION: Non-propulsive contractions that mix chyme and increase contact with digestive enzymes.
PERISTALSIS: Propulsive contractions that move food through the GI tract.
What is the role of the liver in digestion?
- Produces bile for fat digestion.
- Produces nutrients absorbed from the small intestine.
- Detoxifies harmful substances and metabolises drugs.
What are the main sections of the small intestine, and what are their functions?
DUODENUM: Receives chyme, bile, and pancreatic enzymes; primary site of digestion.
JEJUNUM: Primary site of nutrient absorption.
ILEUM: Absorbs vitamin B12 and bile salts.
What is the role of the oesophagus in digestion?
The oesophagus transports food from the pharynx to the stomach via peristalsis, it has no digestive or absorptive function.
What is the significance of the enteric nervous system (ENS)?
The ENS, also called the “gut brain”, regulates GI mobility, secretion, and blood flow independently of the central nervous system. It coordinates peristalsis and responds to change in the digestive environment.
What are the differences between mechanical and chemical digestion?
MECHANICAL DIGESTION: Physical breakdown of food (eg. Chewing, churning in the stomach).
CHEMICAL DIGESTION: Breakdown of food molecules by enzymes and chemicals (eg. Saliva, gastric acid).
