The digestive system breaks down food into nutrients that can be absorbed and used by the body. It consists of the gastrointestinal tract - the mouth, esophagus, stomach, small intestine, large intestine and rectum. Food is ingested, mechanically and chemically broken down, and absorbed in the small intestine. The liver, gallbladder and pancreas secrete digestive juices to aid breakdown. Undigested waste is eliminated as feces through the large intestine and rectum.

1. PRESENTED BY:-
ANAMIKA JAISWAL

2. Digestive system
 Digestion is defined as the process by which food is broken down into simple chemical
substances that can be absorbed and used as nutrients by the body.
 A normal young adult consumes 1 kg of solid diet and 1–2 Liter of fluid per day.
 The gastrointestinal tract (digestive tract, digestional tract, GI tract, GIT, gut, or
alimentary canal) is an organ system within humans and other animals which takes in food,
digests it and absorb energy and nutrients, and expels the remaining waste as feces.
 Functions of digestive system includes
 Ingestion or consumptions of food substances.
 Breaking them into small particles.
 Transport of small particles to different areas of the digestive tract.
 Secretion of necessary enzymes and other substances for digestion.
 Digestion of the food particles.
 Absorption of the digestive products.
 Removal of unwanted substances from the body.

4. Phases of Digestion
1. Ingestion- Intake of food
2. Propulsion
Peristalsis- Alternate waves of muscular contraction and relaxation in the primary
digestive organs. The end result is to squeeze food from one part of the system to the next.
3. Mechanical Digestion -Physical preparation of food for digestion.
Segmentation – Mixing of food in the intestines with digestive juices.
4. Chemical Digestion - Carbohydrates, Fat, and Proteins are broken down by enzymes.
5. Absorption- Transfer of the digested portion of food into the blood from the digestive canal.
6. Defecation- Removal/Elimination of the waste products from the body.

5. Mouth(Digestion)
 Teeth – cut, tear, crush and grind food.
 Salivary glands – produce and secrete saliva into the oral cavity.it has 3 parts.
– Parotid (beneath the cheeks)
– Submaxillary (below the jaw bone)
– Sublingual (below the tongue)
 Saliva moistens the food and contains enzymes (ptyalin or salivary amylase) that begins digestion of
starch into smaller polysaccharides.
 Tongue- Taste Buds
 – Mixes and rolls food into tiny mashed up bits (Bolus)
– Pushes the bolus toward the pharynx and into the esophagus when swallowing.
Functions:
 Ingestion
 Tasting
 Mechanical breakdown of food
 Secretion of salivary glands (salivary amylase).

6. Esophagus
 A straight muscular tube that is about 10 inches (25 cm) long which
connects the mouth with the stomach
 Food takes about 4 to 8 seconds as it passes through to the stomach.
 Its walls contain smooth muscles that contracts in wavy motion
(Peristalsis).
 Peristalsis propels food and liquid slowly Down the esophagus into the
stomach.
 Cardiac Sphincter (ring-like valve) relaxes to allow food into the stomach.

7. Stomach
 J-shaped muscular sac has inner folds (rugae) that increases the surface area of the
stomach.
 Churns and grinds together the bolus into smaller pieces.
 Food is mixed with gastric juices (hydrochloric acid and enzymes) secreted by the
stomach walls.
 HCL helps break down food and kills.
 Bacteria that came along with the food.
 Pepsin – major enzyme; converts proteins into peptides in the presence of HCL.
 Mucus – lubricates food and protects the gastric lining from strong digestive juices.
 Converts the bolus into a liquid (chyme) after 4 hrs of mechanical and chemical
digestion Chyme passes through the pyloric sphincter into the small intestine.

8. Small Intestine(end of digestion and
absorption)
 3 parts:
1. Duodenum - 10 inches long
2. Jejunum- 8 feet long
3. Ileum- 11 feet long
 Takes about 4 – 8 hrs to complete its journey.
 The small intestine produces 7 enzymes. There are a total of 17 enzymes that
are dumped into the duodenum for digestion.
 The small intestine is the area where most digestion occurs.
 It is also the place where 74% of the absorption of nutrients occur.
 Digested nutrients are absorbed through intestinal walls.
 Absorbed materials cross the mucosa into the blood then other parts of the
body for storage or further chemical change.

9. The Large Intestine
 5 feet long
 The CECUM extends as a 2.5 inch blind sac caudally from the sphincter.
 Absorption process take place here.
 Bacteria live in the colon. These are important for the synthesis of Vit. B12 and
K. Other bacteria are responsible for destroying the “bad” bacteria.
 E. coli is an example Large Intestine.
 Waste is pushed into the expanded portion (rectum) of the large intestine.
 Solid waste stays in the rectum until it is excreted through the anus as feces.
 Appendix hangs on the right side of the large intestine.

10. Defecation
 Solid Waste – from the Digestive System in the form of feces
 Accessory Organs-Not part of the path of food, but play a critical role.
 Include: Liver, gall bladder, and pancreas