Digestive Systems: Platypus vs Human

The Platypus and Digestion

• Platypuses are egg-laying mammals.
• Males have venomous spurs on their legs.
• Platypuses lack a traditional stomach, lacking gastric glands and gastric juice production.
• Their digestive system differs from other mammals, illustrating evolutionary diversity.

Human Digestive System

• The human digestive system performs ingestion, digestion, absorption, and elimination.
• Food is ingested through the mouth.
• Digestion breaks down biomolecules (carbohydrates, lipids, proteins, nucleic acids) into smaller units.
• Absorption transports nutrients into the bloodstream.
• Elimination removes unused materials.

Mouth

• Saliva contains salivary amylase, initiating carbohydrate digestion.
• Teeth mechanically break down food.
• Saliva neutralizes acidity, preventing tooth decay.
• The tongue forms chewed food into a bolus for swallowing.

Esophagus

• The epiglottis prevents food from entering the windpipe.
• Peristalsis, wave-like muscle contractions, moves food to the stomach.

Stomach

• The stomach holds about 2 liters.
• Gastric juice, containing hydrochloric acid (HCL) and pepsin for protein digestion, makes it acidic.
• Stomach churning mixes food and gastric juices, creating chyme.
• Sphincters control food movement between the esophagus, stomach, and intestines.
• A protective mucus layer shields the stomach lining from digestion.

Small Intestine

• The duodenum, jejunum, and ileum form the small intestine - the primary site for all biomolecule digestion.
• Enzymes from the liver, gallbladder, and pancreas aid chemical digestion.
• Peristalsis mechanically digests food.
• Nutrients (glucose, fructose, amino acids, electrolytes, vitamins, lipids) are absorbed.
• Intestinal villi and microvilli increase absorption surface area.
• Villi are vascularized for nutrient transport into capillaries.

Large Intestine (Colon)

• Beneficial bacteria in the large intestine aid digestion and vitamin production.
• Water reabsorption is the large intestine's main function.
• Feces, composed of undigested materials and bacteria, are formed.

Rectum and Anus

• The rectum stores feces until elimination.
• Feces exit through the anus.

Accessory Organs

• The liver, a large internal organ, performs functions beyond digestion.
• In digestion, the liver processes carbohydrates and proteins, producing bile for lipid breakdown.
• The gallbladder stores bile.
• The pancreas produces digestive enzymes and neutralizes acidic chyme.

Hormones and Digestive Disorders

• Hormones control digestive processes.
• Digestive disorders include celiac disease (small intestine), diverticulitis (large intestine), and heartburn (acid reflux).

Conclusion

• The human digestive system efficiently breaks down food, absorbs nutrients, and removes waste.
• Understanding the system is key for maintaining health and managing digestive issues.