Presentation on theme: "Quaestio: How do humans obtain and process nutrients?"— Presentation transcript:
1 Quaestio: How do humans obtain and process nutrients? Nunc Agenda:What is the difference between mechanical and chemical digestion?
2 Review Types of Digestion : 1. Mechanical Digestion: Physical breakdown of food.2. Chemical Digestion: Chemical breakdown of food through hydrolysis.
3 HUMAN DIGESTIVE SYSTEM Human digestive tract = GI (gastrointestinal)Consists of a continuous one way food tube (mouth to anus)
4 The Path food takes: 1. Mouth: (oral cavity) ingests food 2. Teeth: function in mechanical breakdown of food,increases surface area of food for enzyme action3.Tongue: acts as a plunger to push food back into the throat (pharynx) taste buds are located on the surface of the tongue
5 Saliva Salivary glands are located in the mouth Produce and secrete salivary amylase which starts the chemical digestion of starchProvides lubrication for the chewed foodContains enzymes to kill harmful microbesChewed food is called a bolus
7 The Path food takes: 4. Pharynx = throat food is pushed by tongue to back of throat, initiates swallowing – food is now in the form of a bolusEpiglottis: flap of tissue that covers the entrance to the tracheaprevents choking
14 The Path food takes: 6. Stomach: J-shaped, sac-like , muscular organ - mechanically churns food into a liquid- begins chemical digestion of protein- lining secretes gastric juice (enzymes and HCL) and mucus- food now liquid called chyme
15 The Stomach’s Environment Gastric Juice: The digestive secretion of glands in the stomach, containing hydrochloric acid and pepsin.Hydrochloric acid (HCl) makes gastric juice highly acidic (pH between 1.5 and 2.5).HCl kills most microorganisms that reach the stomach from swallowed food.Pepsin is the enzyme that breaks down protein.Pepsin is secreted in the form of inactive pepsinogen, which is converted to active pepsin when it comes into contact with HCl.
16 The Stomach secretes gastric juice, a combo of enzymes (I. e The Stomach secretes gastric juice, a combo of enzymes (I.e. pepsin) and hydrochloric acid (HCl)
19 Absorption of nutrients 7. Small Intestine: site of chemical digestion and nutrient absorption- long twisted tube with small diameter ~21 ft-main function is absorption of the digested molecules into the bloodVilli: fingerlike projections where nutrient absorption takes placeincrease surface area
20 The Parts of the Small Intestine. The duodenum:25 centimeters long.Ducts from the liver, pancreas, and gallbladder open into the duodenum.The jejunum:2.5 meters long.The ileum4 meters long.
26 The small intestine seen here in cross section shows the numerous villi that greatly increase the surface area for the digestion and absorption of nutrients. SEM X30Dr. Richard Kessel & Dr. Gene Shih/Visuals Unlimited, Inc.
29 The Small Intestine’s Environment Unlike the stomach (acidic), the small intestine is alkaline (basic).Different secretions account for this.Secretions include:Pancreatic Juice (from Pancreas)Bile (from Gallbladder, Originating in Liver)Intestinal Juice (from Intestine).
30 Accessory organs 1. Pancreas – produces Pancreatic juice: when chyme enters the duodenum (first section of s.i.),it mixes with enzymes and digestive fluids1. Pancreas – produces Pancreatic juice:enzymes that break down carbs, protiens, lipids, and nucleic acidssodium bicarbonate that neutralizes HCL acid from stomach
31 Accessory organs 2. Liver: digestion of fats - produces bile(NOT an enzyme,)emulsifies lipids- breaks them into smaller droplets to increase the surface area for enzymes (lipases) to act on fats3.Gallbladder: small storage sac for bile, carries bile to small intestine
34 The Path food takes: 8. Large Intestine: - No digestion Functions:1. reabsorption of water and salts2. absorption of vitamins produced by bacteria that live in the LI- vitamin K and B3. storage and elimination of fecal matter- egestion – removal of undigested wastesectionsCecumColonrectum
36 Some Digestive Homeostasis Disorders 1.Constipation - too much water absorbed in l.i.2. Diarrhea– not enough water absorbed, can lead to dehydration3. Ulcer – sores that develop when the mucus layer in the stomach breaks down4. Gall stones– small hard particles made of cholesterol which form & collect in gall bladder- may block the bile duct and cause pain5. acid reflux -backflow of stomach contents upward into esophagus6. appendicitis- inflammation of appendix