D313 Section (Digestive System)

Page 1: Introduction

  • Digestive System: "You are what we eat!"

  • Course: WGU GO Anatomy & Physiology

Page 2: Functions of the Digestive System

  • Ingestion: Taking in food.

  • Mastication: Chewing of food.

  • Digestion: Breakdown of food into smaller substances.

  • Secretion: Release of digestive juices and enzymes.

  • Absorption: Nutrients taken up into the bloodstream.

  • Compaction: Formation of feces.

  • Defecation: Elimination of waste.

  • Course: WGU GO

Page 3: Overview

  • Main Structures:

    • Oral Cavity: Initial food intake.

    • Esophagus: Tube connecting mouth to stomach.

    • Stomach: Digestion of food.

    • Small Intestine: Major site for digestion and absorption.

    • Large Intestine: Water reabsorption and feces formation.

    • Anus: Outlet for waste.

  • Accessory Organs:

    • Salivary Glands: Produce saliva for digestion.

    • Liver: Produces bile for fat digestion.

    • Pancreas: Produces digestive enzymes and bicarbonate.

    • Gall Bladder: Stores bile.

  • Course: WGU GO

Page 4: Alimentary Tract and Accessory Organs

  • Mouth: Entry point for food.

  • Teeth: Aid in mastication.

  • Tongue: Assists in tasting and swallowing.

  • Pharynx: Passageway for food.

  • Esophagus: Conducts food to the stomach.

  • Liver: Produces bile; processes nutrients.

  • Stomach: Continues digestion.

  • Pancreas: Produces enzymes and bicarbonate.

  • Gallbladder: Stores bile.

  • Small Intestine: Further digestion and nutrient absorption.

  • Large Intestine: Reabsorbs water and compacts waste.

  • Anus: Excretes feces.

  • Course: WGU

Page 5: Histology of the Alimentary Canal

  • Layers of the Alimentary Canal:

    • Mucosa: Lining of the gastrointestinal tract.

    • Submucosa: Contains blood vessels and nerve endings.

    • Muscularis: Responsible for peristalsis; assists in movement of food.

      • Components: Circular and longitudinal muscle layers, muscularis mucosae.

    • Serosa: Outer connective tissue layer.

  • Nerves and Plexuses: Communicate control of digestive functions.

    • Myenteric Plexus: Regulates digestive tract motility.

    • Submucosal Plexus: Regulates enzyme secretions.

  • Course: WGU

Page 6: Digestion of Food Starts in the Mouth

  • Functions of Saliva:

    • Lubrication: Makes food easier to swallow.

    • Digestive Enzymes: Initiates carbohydrate digestion (amylase).

    • Buffers: Maintain pH balance for optimal enzyme function.

    • Immune System: Contains antibodies to help combat pathogens.

Page 7 & 8: Site of Digestion Initiation

  • Q&A: Where does chemical and mechanical digestion begin?

    • A. Mouth

    • B. Stomach

    • C. Small Intestine

    • D. None of the above

  • Correct Answer: A. Mouth

  • Course: WGU GO

Page 9: Formation of Bolus

  • Bolus: Formed in the mouth after food is moistened and chewed.

  • Options:

    • A. Chyme

    • B. Bolus (Correct)

    • C. Feces

    • D. Vomit

Page 10 & 11: Acidic Environment in the Stomach

  • Q&A: What cell produces an acidic environment in the stomach?

    • A. Chief cells

    • B. Parietal cells (Correct)

    • C. Mucous cells

    • D. G cells

  • Course: WGU GO

Page 12: Stomach Anatomy

  • Gastric Glands:

    • Structure: Circular muscle layer, fundus, longitudinal muscle layers, and gastric pits.

    • Types of Cells:

      • Mucous Cells: Produce mucus.

      • Parietal Cells: Secrete hydrochloric acid.

      • Chief Cells: Produce pepsinogena gastric lipase.

      • G-cells: Release gastrin, stimulates acid production.

    • Rugae: Folds in stomach lining allow for expansion.

  • Course: Encyclopdia Britannica, Inc., WGU

Page 13: Accessory Organs

  • Liver:

    • Produces bile for fat digestion.

    • Stores nutrients.

  • Pancreas:

    • Produces digestive enzymes and bicarbonate.

    • Aids in digestion of carbohydrates, proteins, and fats.

Page 14: Small Intestine Anatomy and Function

  • Parts of the Small Intestine:

    • Duodenum: Mixing bowl; receives digestive enzymes.

    • Jejunum: Primary site for nutrient absorption.

    • Ileum: Absorbs vitamin B12, bile salts.

  • Main Functions:

    • Conducts chemical digestion (90% occurs here).

    • Nutrient absorption.

  • Memory Tip: DJ Ileum = Duodenum, Jejunum, Ileum.

Page 15 & 16: Intestinal Composition

  • Q&A: The intestines are composed of skeletal muscle. True or False?

    • A. True

    • B. False (Correct)

  • Course: WGU GO

Page 17: Functions of the Large Intestine

  • Main Functions:

    • Reabsorb water: Compacts material into feces.

    • Absorption of Vitamins: Produced by bacteria.

    • Storage of Fecal Matter: Prior to defecation.

    • No Further Digestion: Beyond that performed by enteric bacteria.

  • Structure: Divided into cecum, colon (ascending, transverse, descending, sigmoid), rectum, anus.

Page 18 & 19: Anus Sphincters

  • Q&A: How many sphincters does the anus contain?

    • A. None

    • B. 1

    • C. 2

    • D. None of the above

  • Correct Answer: C. 2

  • Course: WGU GO

Page 20: Carbohydrate Digestion

  • Process:

    • Begins in the mouth with salivary amylase.

    • Continues in the stomach and small intestine with pancreatic amylase.

  • Final Products: Monosaccharides including glucose, fructose, galactose.

  • Transport: Active transport into the bloodstream.

Page 21: Fate of Glucose

  • High Blood Sugar: Stimulates insulin release, promotes glycogen breakdown.

  • Low Blood Sugar: Stimulates glucose release from glycogen, increases glucose uptake in cells.

Page 22: Protein Digestion

  • Process:

    • Begins in the stomach (HCl, pepsin).

    • Continues in the small intestine with enzymes like trypsin.

  • Final Products: Amino acids and small peptides.

Page 23: Fate of Protein

  • Breakdown: Amino acids can be recycled or converted into energy (e.g., glucose).

  • Production of Urea: Liver converts excess amino acids to urea.

  • Transamination: Conversion of one amino acid to another.

Page 24: Protein Anabolism

  • Protein Synthesis: Building of proteins from amino acids.

  • Keto Acid Modification: Can produce glucose or triglycerides during fasting.

Page 25: Fat Digestion

  • Process:

    • Mechanical digestion in the stomach.

    • Enzymatic digestion by pancreatic lipase in the small intestine.

  • Final Products: Monoglycerides and fatty acids absorbed into the bloodstream via chylomicrons.

Page 26 & 27: Composition of Saliva

  • Q&A: Saliva can contain all the following except:

    • A. Mucus

    • B. Amylase

    • C. Antibodies

    • D. Pepsinogen (Correct)

  • Course: WGU GO

Page 28 & 29: Delivery of Pancreatic Juice

  • Q&A: Pancreatic juice is delivered to the small intestine through the:

    • A. Hepatic duct

    • B. Bile duct

    • C. Pancreatic duct (Correct)

    • D. Alveolar duct

  • Course: WGU GO

Page 30 & 31: Function of Amylase

  • Q&A: The enzyme amylase chemically digests:

    • A. Carbohydrate (Correct)

    • B. Lipids

    • C. Fats

    • D. Nucleic acids

  • Course: WGU GO

Page 32 & 33: Secretions of the Stomach

  • Q&A: Which of the following is NOT secreted in the stomach?

    • A. Acid

    • B. Pepsin

    • C. Mucous

    • D. Amylase (Correct)

  • Course: WGU GO

Page 34: Questions

  • Any Questions? contact: healthscience@wgu.edu

Page 35: Conclusion

  • Thank You. www.healthscience.edu WGU GO