Human Digestion: Alimentary Canal and Organs

• Focus on notes, classwork and labs from Human Digestion

Alimentary Canal Organs and Digestion

• The alimentary canal includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus
• These organs contribute to the digestion process through mechanical and chemical means

Mouth

• Mechanical digestion occurs through chewing (mastication)
• Chemical digestion begins with saliva, which contains salivary amylase
• Salivary amylase starts the breakdown of starch

Esophagus

• Transports food from the mouth to the stomach
• This is achieved through peristalsis, which is involuntary muscle contractions

Stomach

• Mechanical digestion occurs via churning
• Chemical digestion occurs with gastric juices and pepsin
• Breaks down food into a mixture called chyme

Small Intestine

• Chemical digestion and nutrient absorption take place
• Enzymes from the pancreas and bile from the liver further break down food
• Villi absorb nutrients

Large Intestine

• Absorbs water and minerals
• Processes waste materials

Rectum and Anus

• Responsible for the storage and elimination of waste

Types of Digestion in Each Organ

• Digestion can either be mechanical or chemical, depending on the organ

Mouth

• Both mechanical and chemical digestion take place
• Salivary amylase is responsible for the chemical breakdown of starch

Esophagus

• Mechanical digestion through peristalsis occurs

Stomach

• Mechanical digestion via churning
• Chemical digestion with gastric juices

Small Intestine

• Chemical digestion and nutrient absorption occurs

Large Intestine

• Absorption of water
• Electrolyte absorption
• No digestion occurs here

Cardioesophageal Sphincter

• Located between the esophagus and stomach
• Prevents acid reflux from the stomach into the esophagus

Heartburn

• Caused by stomach acid flowing back into the esophagus
• Treatment includes antacids, avoiding large meals, and not lying down immediately after eating

Accessory Organs and Digestion

• Accessory organs aid in the digestion process
• These include the salivary glands, pancreas, gallbladder, and liver

Salivary Glands

• Produce saliva containing salivary amylase
• Salivary amylase starts the digestion of starch

Pancreas

• Produces digestive enzymes, like pancreatic amylase, lipase, and proteases
• Also produces bicarbonate to neutralize stomach acid

Gallbladder

• Stores bile from the liver
• Releases bile to help digest fats

Liver

• Produces bile to emulsify fats
• Stores glycogen

Definitions

• Important terminology for understanding digestion

Mastication

• The process of chewing

Chyme

• The semi-liquid mixture of food and digestive juices in the stomach

Bolus

• A chewed piece of food that is swallowed

Enzymes and Bile

• Enzymes and bile, their functions, and where they act

Salivary Amylase

• Works in the mouth
• Breaks down starch

Pepsin

• Works in the stomach
• Breaks down proteins

Pancreatic Proteases (Trypsin, Chymotrypsin)

• Work in the small intestine
• Breaks down proteins

Pancreatic Amylase

• Works in the small intestine
• Breaks down starch

Pancreatic Lipase

• Works in the small intestine
• Breaks down fats

Bile

• Produced by the liver, stored in the gallbladder
• Emulsifies fats in the small intestine

Villi and Microvilli

• Villi and microvilli details

Location

• Found in the small intestine

Function

• Villi increase the surface area for nutrient absorption
• Microvilli further increase surface area

Cells in Digestion

• Names and functions of cells involved in digestion

Chief Cells

• Secrete pepsinogen
• Pepsinogen is activated to pepsin to digest proteins

Mucous Cells

• Secrete mucus
• Mucus protects the stomach lining from acidic juices

Parietal Cells

• Secrete hydrochloric acid (HCl)
• HCl activates pepsin

Gastric Cells

• Produce digestive enzymes and acids
• Aid in food breakdown

Peristalsis

• Involuntary muscle contractions
• Move food through the digestive tract, starting from the esophagus

Organic Compounds

• Functions and examples of carbohydrates, fats, and proteins

Carbohydrates

• Provide energy
• Examples include sugars, starches, and fiber

Fats

• Provide long-term energy storage
• Help absorb vitamins
• Examples include oils and butter

Proteins

• Proteins build and repair tissues
• Examples include meat, beans, and eggs

Labs

• Relevant labs include modeling the digestive system
• Labs also include identifying nutrients in foods and lactose intolerance