Digestive System Quiz (BMS Learning Outcomes)

Digestive System Processes

• Ingestion: Taking food and liquids into the gastrointestinal (GI) tract.
• Propulsion: Moving and mixing food along the GI tract.
• Digestion: Mechanical breakdown (e.g., chewing) and chemical breakdown (enzymes) of food into smaller molecules.
• Absorption: Movement of digested nutrients through the GI tract walls into the bloodstream.
• Elimination: Removal of undigested waste products from the body.

Mouth

• Mechanical Digestion: Chewing (mastication) breaks down food into smaller pieces and forms a bolus.
• Chemical Digestion: Salivary amylase (ptyalin) starts breaking down starches into maltose.
• Taste buds: Help identify and assess food.

Salivary Glands

• Secrete saliva to moisten and lubricate food for swallowing.
• Contains mucin (lubricant) and amylase (enzyme).

Swallowing

• Voluntary phase: Tongue pushes food into the pharynx.
• Reflex phase: Soft palate closes the nasal cavity, larynx rises, epiglottis covers the trachea to prevent food from entering the lungs.
• Peristalsis moves food through the oesophagus.

Oesophagus

• Lined with a mucus membrane, secreting mucus for lubrication.
• Smooth muscle contractions (peristalsis) move food towards the stomach.

Peristalsis

• Rhythmic contractions of smooth muscles in the GI tract.
• Circular muscles contract behind the food bolus to prevent backflow, while longitudinal muscles contract to push the bolus forward.

Stomach

• Temporary holding area for food (3-4 hours).
• Churns food into chyme (a semiliquid mixture).
• Rugae increase surface area for churning.
• Pyloric sphincter regulates the release of chyme into the small intestine.

Small Intestine

• Site of nutrient absorption.
• Villi and microvilli increase surface area for absorption.
• Duodenum: First part, where chemical digestion continues with enzymes from the pancreas and duodenum itself.
• Jejunum/Ileum: Middle and final parts of the small intestine, continue absorbing nutrients.

Pancreas

• Exocrine function: Produces digestive enzymes (e.g., amylase, lipase, protease) that enter the duodenum.
• Endocrine function: Produces hormones like insulin and glucagon.

Liver

• Produces bile, stored in the gallbladder.
• Bile aids in fat digestion by emulsifying fats.
• Nutrient processing and detoxification

Gallbladder

• Stores and concentrates bile.
• Releases bile into the duodenum in response to fat entering the small intestine.

Large Intestine (Colon)

• Absorbs water from waste material.
• Ascending, transverse, descending, and sigmoid colon are sections.
• Forms feces.

Rectum

• Stores feces until elimination.

Anus

• Opening for excreting feces.

Digestive Tissue Layers

• Adventitia/Serosa: Outer covering of connective tissue.
• Muscularis: Smooth muscle layer for peristalsis (Inner circular and outer longitudinal layers).
• Submucosa: Layer with blood vessels, lymphatic vessels, nerves, and glands.
• Mucosa: Innermost layer, lining epithelial cells coated with mucus.

Gastric Juice Functions

• Digestion: Breaks down food particles into chyme.
• Microorganism inactivation: The acidity of gastric juice kills microorganisms.
• Nutrient absorption: Aids in absorbing vitamin B12 and iron.
• Stomach protection: Mucus in gastric juice protects the stomach lining from the acid.

Chemical Digestion Summary

• Carbohydrates:*

• Mouth: Salivary amylase begins the breakdown of starches.

• Small intestine: Pancreatic amylase and various enzymes (sucrase, maltase, lactase) break down disaccharides into monosaccharides.

• Proteins:*

• Stomach: Pepsin begins protein breakdown.

• Small intestine: Trypsin, chymotrypsin, and other enzymes further break down proteins into amino acids.

• Lipids (Fats):*

• Small intestine: Bile emulsifies fats, pancreatic lipase breaks them down into fatty acids and glycerol.

Explore the key processes of the digestive system, including ingestion, propulsion, digestion, absorption, and elimination. This quiz will help you understand the roles of different components, such as the mouth and salivary glands, in the digestion process. Test your knowledge on how food is processed in the gastrointestinal tract.