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.