Digestive System Overview

Digestive System Overview

• The digestive system obtains energy and materials needed for growth and repair from food.
• Food contains nutrients, such as carbohydrates, proteins, lipids, minerals, vitamins, water, and fiber.
• Food's organic compounds are broken down into simpler forms.
• The digestive tract provides one-way transport through wavelike muscle contractions and sphincter muscles.

Digestive System Functions

• Ingestion: Taking food into the digestive system through the mouth.
• Mastication: Chewing food to break it down and mix it with saliva in the mouth.
• Deglutition: Swallowing food to move it from the mouth to the stomach.
• Digestion: Process of changing food into a usable form for the body.
• Absorption: Passage of food monomers through the digestive tract wall into the blood stream or lymphatic system.
• Defecation: Elimination of indigestible, non-usable wastes.

Organs of the Digestive System

• Mouth: Initial site of digestion with teeth and saliva.
• Pharynx: Passageway for food and air.
• Esophagus: Tube that connects the pharynx to the stomach.
• Stomach: Churns and mixes food with gastric juices.
• Small intestine: Main site of digestion and absorption.
• Large intestine: Absorbs water and remaining nutrients; forms and eliminates feces.
• Accessory organs: Organs that aid in digestion but aren't part of the digestive tract, including salivary glands, liver, gallbladder, and pancreas.

Digestive Enzymes

• Saliva contains salivary amylase to break down starch.
• Stomach contains pepsin to digest proteins.
• Pancreas contains pancreatic amylase, lipase, trypsin to further break down carbohydrates, lipids, and proteins respectively.
• Small intestine contains enzymes like maltase, lactase, sucrase, peptidases to break down carbohydrates, lactose, sucrose, and peptides into smaller molecules.

Regulation of Digestion

• Hormones like gastrin, secretin, and CCK regulate digestive juice secretion.
• Gastrin stimulates stomach acid and enzyme production.
• Secretin and CCK regulate pancreatic and liver secretions.
• Nervous system and hormones regulate digestive processes.

Absorption

• Nutrients are absorbed into the bloodstream or lymph vessels.
• Small intestine has villi and microvilli to increase surface area for absorption.
• Nutrients like glucose, amino acids, glycerol, fatty acids etc are absorbed.

Liver Functions

• Produces bile, which helps digest fats.
• Detoxifies the blood.
• Breaks down hemoglobin.
• Produces plasma proteins.
• Stores glucose as glycogen.
• Deaminates amino acids.

Large Intestine

• Absorbs water and electrolytes.
• Forms and eliminates feces (solid waste).
• Contains bacteria that produce vitamins, particularly vitamin K.