The Alimentary Tract A long muscular tube with many sections and areas. Begins with the mouth and ends with the anus.

The Alimentary tract Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine Anus

Accessory Parts Organs that are not in the Alimentary tract but helps in the digestion –T–T–T–Teeth –T–T–T–Tongue –S–S–S–Salivary glands –L–L–L–Liver –G–G–G–Gall bladder –P–P–P–Pancreas

Mouth Functions: – F– F– F– Food enters in the mouth or oral cavity – T– T– T– Tasting – M– M– M– Mechanical breakdown of food – S– S– S– Secretion of salivary glands (salivary amylase)

Mouth Structures in the mouth that aids digestion: Teeth – cut, tear, crush and grind food. Salivary glands – produce and secrete saliva into the oral cavity. – P– P– P– Parotid (beneath the cheeks) – S– S– S– Submaxillary (below the jaw bone) – S– S– S– Sublingual (below the tongue) – saliva moistens the food and contains enzymes (ptyalin or salivary amylase) that begins digestion of starch into smaller polysaccharides.

Mouth Tongue – M– M– M– Mixes and rolls food into tiny mashed up bits (Bolus) – P– P– P– Pushes the bolus toward the pharynx and into the esophagus when swallowing.

Anatomy of the Mouth and Throat

Human Deciduous and Permanent Teeth

Mechanism of Swallowing Swallowing is a coordinated activity of the tongue, soft palate, pharynx and esophagus. Phases –F–F–F–Food is pushed into the pharynx by the tongue. (voluntary) –T–T–T–Tongue blocks the mouth –S–S–S–Soft palate closes off the nose –L–L–L–Larynx (Adams Apple) rises so the Epiglottis (a flap of tissue) can close the opening of the trachea.

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.

Peristalsis

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.

Stomach

Stomach 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.

Movements in Stomach

Small Intestine Long (20 ft), coiled tube beneath the stomach. Has three parts: Duodenum – upper part; about 10 in; connected to the stomach. – where the digestive juices from the pancreas and the liver combine with chyme making it thin and watery. Jejunum – about 8 ft Ileum – about 12 ft

Site of greatest amount of digestion and absorption

Small Intestine Takes about 4 – 8 hrs to complete its journey. Mucosa (inner wall) – secretes several enzymes that acts on the food. Where the pancreatic enzymes are emptied into. 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.

Has folded inner walls covered with fingerlike projections (villi; sing. – villus) Each villus has tinier projections called microvilli that absorbs digested food. Villi and microvilli increases the surface area of the small intestine for greater absorption. Peristalsis moves the undigested food to the large intestine.

Movement in small intestine: Mixing: Segmental contraction that occurs in small intestine Secretion: Lubricate, liquefy, digest Digestion: Mechanical and chemical Absorption: Movement from tract into circulation or lymph Elimination: Waste products removed from body

Large Intestine a.k.a. Colon larger diameter, but shorter (5 ft) Water is absorbed from the undigested food making the waste harder until it becomes solid. Waste stays for 10 – 12 hours.

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.

Accessory Organs Produce or store enzymes that helps in digestion. Liver –L–L–L–Largest gland of the body –S–S–S–Stores vitamins A,D,E,K –S–S–S–Stores sugar and glycogen –P–P–P–Produces bile (watery, greenish substance) –S–S–S–Secretes bile to the gall bladder via the hepatic duct and cystic duct.

Gall bladder – S– S– S– Stores bile in between meals – S– S– S– Secretes bile to the duodenum through the bile duct during mealtime. Bile contains bile salts, pigments, cholesterol and phospholipids. Bile is an emulsifier NOT an enzyme. Emulsifier – dissolves fat into the watery contents of the intestine.

Pancreas – P– P– P– Produces a juice that contains enzymes (amylase and insulin) to break down carbohydrates, fats and protein. – S– S– S– Secretes the juice into the duodenum through the pancreatic duct.

About the author… My name is Azizullah Mohammadi. I am a student at KAZNMU.