Digestive System Quiz

Digestive System Overview

• The digestive system obtains energy and materials for growth and repair from food.
• Nutrients in food include carbohydrates, proteins, lipids, minerals, vitamins, water, and fiber.
• Organic compounds (carbohydrates, fats, and proteins) must be broken down into simpler monomers for cells to use them.
• Digestion breaks down complex food molecules into simpler units.

Digestive Tract

• The digestive tract is a tube called the gastrointestinal tract (GIT), allowing one-way transport of food.
• Specialised sections are specialised for different functions (e.g., ingestion, chewing).
• Seven functions include ingestion, mastication, deglutition, digestion, absorption, peristalsis, and defecation.
• Food is processed in a sequence of steps to become usable for the body.

Mechanical and Chemical Digestion

• Physical digestion tears and grinds food into smaller pieces, increasing surface area for enzyme action.
• Chemical digestion changes large food molecules into smaller monomers using enzymes.
• Mechanical and chemical digestion both begin in the mouth (using teeth and saliva).
• Enzymes such as salivary amylase start breaking down starches in the mouth.

Salivary Glands

• Three pairs of salivary glands moisten and lubricate the food, also helping to aid in swallowing.
• Saliva contains mucus to lubricate food and salivary amylase.
• Salivary amylase hydrolyses starch to maltose.

Swallowing and Esophagus

• Swallowing (deglutition) moves food from the mouth to the stomach.
• The epiglottis prevents food from entering the trachea (windpipe).
• Peristalsis in the esophagus moves food toward the stomach.
• The cardiac sphincter relaxes to allow food into the stomach.

Stomach

• The stomach stores food, mixes it with gastric juices, and continues chemical digestion of protein using hydrochloric acid (HCl) and pepsin.
• Hydrochloric acid provides a suitable pH for pepsin.
• Pepsin begins protein break down.
• Food becomes chyme.

Small Intestine

• The small intestine is the major site of nutrient absorption.
• Sections are the duodenum, jejunum, and ileum.
• The small intestine receives pancreatic juices and bile which aid in digestion.
• Chemical digestion continues in the small intestine with specific enzymes (e.g., pancreatic amylase, trypsin, lipase).
• Monosaccharides, amino acids, nucleotides, vitamins, and minerals are absorbed.

Absorption in the Small Intestine

• Cells lining the villi (projections lining the small intestine) greatly increase the absorption area.
• Absorption methods include facilitated diffusion and active transport of nutrients into the capillaries (or lymph vessels).

Pancreas

• The pancreas is a dual-function gland.
• It secretes pancreatic juices containing enzymes (e.g., pancreatic amylase, lipases, trypsin) into the duodenum.
• These enzymes complete the breakdown of carbohydrates, fats, and proteins.
• The pancreas also releases hormones (insulin and glucagon) that regulate blood glucose levels.

Liver

• The liver produces bile to emulsify fats into smaller droplets.
• Bile contains bile salts needed for lipid digestion.
• The liver processes and stores nutrients, detoxifies the blood, produces blood proteins, and stores glycogen (from excess glucose).

Large Intestine

• The large intestine absorbs water, minerals, and some vitamins from undigested food.
• Bacteria in the large intestine help in the fermentation of undigested material and synthesis of certain vitamins.
• Feces (undigested materials) are formed and eliminated through the anus.

Control of Digestion

• The nervous system and hormones control digestive secretions and processes.
• Hormones (gastrin, secretin, CCK) regulate the secretion of enzymes and bile from accessory organs.
• Signals from the brain trigger the secretion of digestive enzymes and the movement of food in different sections of the digestive tract.