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The human syndromes on digestive system.

1. Human Digestive System 1 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

2. Human Digestive System The human digestive system is a group of organs that work together to break down food into smaller, absorbable molecules. It allows the body to obtain energy, nutrients, and water from the food we eat. 2 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

3. use of nutrients by body cells removal of undigested waste 3 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

4. 1.Mouth (Buccal or Oral Cavity) Physical Form of Food: Food (solid form) → Bolus (soft mass) Functions: Ingestion: Food enters through the mouth. Mechanical digestion: Teeth grind food into smaller pieces (mastication). Chemical digestion: Saliva mixes with food. Formation of bolus: Tongue rolls the chewed food into a soft ball (bolus) for swallowing. 4 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

5. Saliva (from salivary glands): Water and mucus – moisten and soften food. Enzyme: Salivary amylase (ptyalin) → Converts starch → maltose (a simple sugar). Lysozyme – destroys bacteria. Food becomes a soft, partially digested bolus ready to move to the stomach. 5 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

6. 2. Pharynx and Oesophagus Pharynx: Common passage for food and air. Epiglottis closes the trachea during swallowing to prevent choking. Oesophagus : A muscular tube (~25 cm long) Moves bolus to stomach by peristalsis (wave-like contractions). No digestion occurs here. Physical Form: Bolus continues to stomach through peristaltic movement. 6 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

7. 3. Stomach Physical Form of Food: Bolus → Chyme (semi-liquid mixture) Structure and Secretions: Regions: Cardiac, Fundic, Pyloric. Gastric glands secrete gastric juice containing: Hydrochloric acid (HCl): Kills microbes, activates enzymes. Pepsin: Converts proteins → peptides . Rennin (in infants): Coagulates milk protein (casein). Mucus: Protects stomach lining. Functions: Churns food mechanically. Starts protein digestion chemically. Converts bolus into chyme , a semi-fluid acidic paste. 7 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

8. 4. Small Intestine Divided into Duodenum, Jejunum, and Ileum — main site of digestion and absorption . (a) Duodenum Receives bile from liver/gallbladder and pancreatic juice from pancreas. Bile (no enzyme): Bile salts emulsify fats (break large fat globules into tiny droplets). Neutralizes acid from stomach. Pancreatic Juice (from pancreas): Enzyme Function Amylase Starch → Maltose Trypsin Peptides → Amino acids Lipase Fats → Fatty acids + Glycerol 8 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

9. (b) Jejunum & Ileum Intestinal glands secrete intestinal juice (succus entericus) . Enzymes complete digestion Enzyme Function Maltase Maltose → Glucose Lactase Lactose → Glucose + Galactose Sucrase Sucrose → Glucose + Fructose Peptidase Peptides → Amino acids Lipase Fats → Fatty acids + Glycerol Nucleotidase , Nucleosidase Nucleic acids → Sugars, phosphates, bases Physical Form of Food: Chyme → Chyle (milky fluid containing digested nutrients 9 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

10. 5. Absorption of Nutrients Takes place mainly in the ileum (inner surface lined with villi and microvilli ). Villi increase surface area for absorption Nutrient Absorbed Form Enters Carbohydrates Glucose, Fructose Blood capillaries Proteins Amino acids Blood capillaries Fats Fatty acids + Glycerol Lymphatic vessels (lacteals) Water, Minerals, Vitamins — Blood vessels Physical Form: Chyle (nutrient-rich milky fluid) absorbed into blood and lymph 10 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

11. 6. Assimilation Absorbed nutrients are carried by blood to all body cells. Used for: Energy production Growth and repair of tissues Synthesis of enzymes, hormones, and other biomolecules 11 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

12. 7. Large Intestine Parts: Caecum → Colon → Rectum Functions: Absorbs remaining water and salts . Houses beneficial bacteria that produce vitamin K and B12 . Forms feces from undigested material. Physical Form of Food: Chyle → Undigested residue → Feces 12 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

13. 8. Rectum and Anus Rectum: Stores feces temporarily. Anus: Expels feces out of the body. The process is called Egestion (Defecation) . Final Physical Form: Feces (solid waste material) 13 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources

14. Food Conversion Forms and Digestion Step Organ Enzyme / Juice Food Form Digestion / Conversion End Product 1 Mouth Salivary amylase Food → Bolus Starch → Maltose Bolus formed 2 Stomach Pepsin, HCl Bolus → Chyme Proteins → Peptides Chyme 3 Duodenum Bile, Pancreatic enzymes Chyme → Chyle Fats, Proteins, Carbs → Simple forms Chyle 4 Ileum Intestinal enzymes Chyle Final digestion Simple nutrients 5 Large Intestine — Chyle → Feces Water absorbed, waste solidified Feces 14 Lecture By: Marya Rubab Course: Fundamentals of Natural Resources