Digestive System: Organs and Processes

• Digestive System
  • Organs for digestion
  • Processes of the digestive system
  • Gastro-intestinal disorders
• Objectives of the lesson on the digestive system
  • Describe the different organs for digestion and their functions
  • Explain the processes of the digestive system and its interaction with the circulatory and excretory systems
  • Explain the prevention, detection, and treatment of diseases of the digestive system
  • Identify healthy practices that affect the digestive system

Digestion

• The process of breaking down food
• Mechanical digestion breaks down food physically using teeth and tongue
• Chemical digestion breaks down food into chemical components (nutrients) by enzymes, such as saliva

Organs of the Digestive System

• Mouth (oral cavity)
• Pharynx
• Esophagus
• Stomach
• Small intestines
• Large Intestines
• Rectum
• Anus

Oral Cavity

• Palate: The roof of the mouth
• Tongue: Mixes and pushes food
• Salivary glands: 3 pairs; produces salivary amylase (saliva)
• Teeth: Used for mastication(cutting, tearing, and grinding food)
  • Incisors (8) - cutting
  • Canines (4) - tearing
  • Premolars (8) - grinding
  • Molars (12) - grinding

Pharynx

• Epiglottis prevents food from entering the trachea

Esophagus

• Bolus is a ball of food
• Peristalsis is the movement of the esophagus

Stomach

• Temporary food storage and site of chemical digestion
• Rugae are the folds of the stomach
• Esophageal sphincter: junction of the esophagus and stomach
• Pyloric sphincter: junction of the stomach and small intestine
• The stomach has glands that produce substances
  • Mucous cells produce mucus, which protects the stomach
  • Parietal cells produce HCI that softens food and kills bacteria
  • Gastric chief cells produce pepsin that digests proteins
  • Gastric amylase digests starch
  • Gastric Lipase digests fats (triglyceride -> 1 free fatty acid)
  • Gastric juice combines HCI, mucus, and enzymes
  • Chyme is partially digested liquid food

Small Intestine

• Longest (7m) and 2.5cm in diameter
• Has three parts: Duodenum, Jejunum, and Ileum
• Intestinal glands produce intestinal amylase, lipase, peptidase, maltase, sucrase, and lactase
  • Duodenum and Jejunum
    • Villi: small projections of the small intestine
    • Microvilli: tiny projections of villi
    • Contains capillaries where the absorption of nutrients occurs -Ileum
    • Absorbs calcium, zinc, and vitamins

Pancreas & Liver

• Liver:
  • Largest internal organ
  • Produces bile; stored in the gall bladder
  • Digests fats into tiny droplets through emulsification
• Pancreas:
  • Secretes pancreatic juice
  • Reduces the chyme acidity
  • Produces trypsin (digests proteins)
  • Produces Pacreatic amylase (Carbs ->Maltose)
    • Produces Pancreatic lipase: digests fats (triglyceride -> 2 free fatty acid)

Large Intestines

• About 1.5 m in length and 6.5 cm in diameter
• Includes cecum, colon, rectum, and anal canal
• Produces vitamin K and some B vitamins using bacteria
• Absorbs water
• Indigestible material then becomes solid and is called feces

Rectum

• The end of the large intestine
• Temporary storage of waste material

Anus

• The end of the rectum
• Where feces comes out of the body
• Consists of a muscular ring called the anal sphincter, that opens during a bowel movement to allow feces to pass through

Gastrointestinal Disorders

• Constipation: occurs when a hard-to-pass or frequent bowel movement happens to a person
• Hemorrhoids: swollen, enlarged veins that form inside and outside of the anus and rectum
• Diverticulosis: infected pouches inside the intestine (diverticula)
• Diarrhea: loose, watery, and possibly more-frequent passage of stool
• Appendicitis: happens when the appendix gets clogged, infected, or inflamed
• Colon cancer: growth of polyps that turned into a tumor in the colon's inner lining