Digestive-System 2

Animal Digestive System Overview

  • Prepared by: Mr. Daryl B. Sercena

Introduction to Digestion

  • Digestive System breaks down food to provide energy to every cell in the body.

  • Quote: "The way to a man's heart is through his stomach."

Digestion Process

  • Definition: Complexity of turning food into NUTRIENTS for energy, growth, and cell repair.

Key Processes in Digestion

1. Ingestion

  • Ingestion involves taking in food at the beginning of the gastrointestinal tract.

  • Triggers release of saliva into the oral cavity.

  • Salivary glands are activated by the smell and taste of food, increasing saliva production.

  • Enzyme: Amylase in saliva digests starch and glycogen.

2. Digestion

  • Involves breaking down food into smaller molecules.

  • Mechanical Digestion:

    • Mastication (chewing), churning in the stomach, and segmentation in the small intestine.

  • Chemical Digestion:

    • Enzymes such as gastrin trigger stomach acids (HCl) and enzymes (pepsinogen) for food breakdown.

    • Bile and pancreatic juice aid digestion in the small intestine.

3. Secretion

  • Digestive organs synthesize and release enzymes for chemical digestion.

4. Absorption

  • Transport of digested food into the bloodstream via intestinal capillaries and lacteals:

    • Capillaries: Absorb glucose, amino acids, vitamins, minerals.

    • Lacteals: Absorb fatty acids, glycerol.

    • Most water and vitamins absorbed in the large intestine.

5. Excretion

  • The process of eliminating undigested food.

  • Feces contains indigestible materials, including fibers and bacteria.

  • Mass movements of the large intestine push feces to the rectum, signaling excretion.

Mechanical and Chemical Digestion

  • Mouth Region:

    • Mechanical digestion through teeth (incisors, canines, premolars, molars) and involvement of the tongue.

    • Chemical digestion begins with saliva.

  • Pharynx and Epiglottis:

    • Pharynx connects mouth to esophagus, with the epiglottis preventing food from entering the respiratory tract.

  • Esophagus:

    • Muscular tube transporting food to the stomach; sphincters prevent backflow.

  • Stomach:

    • Stores and breaks down food; acidic environment facilitates digestion.

  • Small Intestine:

    • Site of major digestion and absorption; divided into duodenum, jejunum, and ileum.

  • Large Intestine:

    • Final organ for absorption of water and vitamins, converting chyme into feces.

Accessory Organs of Digestion

  • Salivary Glands: Secrete saliva for cleaning, lubrication, and starting chemical digestion.

  • Liver: Produces bile for fat digestion.

  • Gallbladder: Stores bile until needed in the duodenum.

  • Pancreas: Secretes pancreatic juice to break down proteins, fats, and carbohydrates.

Specialized Digestive Systems

Ruminant Digestive System

  1. Ingests cellulose-rich food.

  2. Mechanical digestion in the rumen.

  3. Regurgitation in the reticulum.

  4. Further digestion in the omasum.

  5. Final digestion in the abomasum.

Avian Digestive System

  • Birds do not chew food; it moves to the crop for temporary storage.

  • Proventriculus facilitates chemical digestion while the gizzard aids in mechanical digestion.

  • Common exit for food wastes and urine is the cloaca.

Conclusion

  • Understanding the digestive system is important for grasping how nutrients are processed and utilized in the body.