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The Digestive System The Basics of Nutrition Heterotrophs (can NOT synthesize organic nutrients) Digestion involves: • ingestion: • digestion: • egestion: The Basics of Nutrition Nutrient: any substance that provides energy for growth and repair: Food molecules must be digested into subunits ( Monomers ) that can diffuse through cell membranes Structure of Digestive System • Continuous tube extending from mouth to anus- Also called ALIMENTARY TRACT • Accessory organs attached along the way LineRider • LineRider Organs of Digestive System Alimentary Tract 1. Mouth – “oral cavity” 2. Pharynx – “throat” 3. Esophagus 4. Stomach 5. Small intestine 6. Large intestine – “colon” Organs of Digestive System Accessory Organs 1. Liver 2. Gall Bladder 3. Pancreas 4. Appendix 5. Salivary Glands The Mouth • Ingestion occurs here • Contains teeth, tongue, and salivary glands • Both chemical and mechanical digestion occur here. • Only Starch get digested in the Mouth The Mouth – Chemical: Salivary amylase is an enzyme in saliva that breaks down Starch. – Mechanical: Teeth grind food increasing surface area for more efficient enzyme action • saliva also lubricates the food by adding water and mucus The Food we swallow is called a bolus Pharynx • • • Back of the throat Where openings to trachea and esophagus meet Epiglottis: flap of connective tissue that closes over the trachea when swallowing Esophagus • • tube that connects the oral cavity with stomach Peristalsis: muscular contractions that squeeze food towards the stomach A Phone Call at 12am The opening from the esophagus into the stomach is a ring of muscle called the cardiac sphincter Stomach • muscular organ that mechanically and chemically digests food. • Only Protein get digested in the stomach Stomach • Lined with cells that secrete: 1. Mucus to protect stomach lining 2. Protease ( Pepsin ) to chemically digest Protein 3. Hydrochloric acid (HCl) HCl has several functions - lowers the pH in the stomach (pepsin works best at pH 2) - helps to kill microorganisms ingested in the food Stomach Strange things in kids stomachs Chyme The food coming out of the stomach is a soupy mixture called chyme Most of the chemical digestion of food occurs in the the duodenum the first 25 cm of the SI Villi VILLI - finger-like projections lining the small intestines for increased surface area FYI: (size of tennis court) • Absorption and diffusion of nutrients into the bloodstream occurs here A CLOSER LOOK at Villi Digested end products are taken into the villi by active and passive transport Each villus contains : Lacteal - pick up fatty acids and glycerol Veins, arteries and capillaries - pick up nucleotides, amino acids, and monosaccharides Accessory Organs Pancreas • Pancreas: 1. Produces enzymes and release them into the Small Intestines: Enzymes breaks down carbohydrates, lipids, and proteins • Pancreas: 2. Produces sodium bicarbonate – neutralizes stomach acid 3. Produces hormones that regulate blood sugar levels (Endocrine Hormones) Pancreatic juice contains: proteases - digest proteins lipases - digest lipids amylases - digest carbohydrates Gall Bladder • Small, non-vital organ – storage of bile • Bile – emulsifies fat • Tucked on underside of liver Gallbladder The gallbladder releases bile into the Small Intestines Bile is NOT an enzyme - its function is to break down fat globules by a emulsification Emulsification: mechanical digestion of fats molecules dissolved into smaller droplets The Liver • Largest internal organ Liver • Functions: Produces Bile: Which breaks down fats Produces Urea (from breakdown of proteins) Filters out harmful substances Removes Biliubin ( from dead red blood cells ) Produces and removes Cholesterol Bile is produced in the liver then stored in the gallbladder Appendix • Pouch located where small and large intestines meet • A vestigial organ: – Non-vital – Thought to house important bacteria needed for balance in body – Could possibly play a role in immunity • All indigestible waste at this point – no nutritional value • Known as the colon • Regulates water concentration of fecal matter before EGESTION through the RECTUM and ANUS • Function is to reabsorb most of the water that was not picked up by the SI • Too much or too little water can be problematic… A large colony of bacteria known as E. Coli lives in the LI They Help produce vitamin K - needed for blood clotting 1. Erosion of the stomach lining by digestive enzymes or acid due to lack of protective mucus. Ulcers • a hole in the stomach lining • cause: bacterium – Helicobacter pylori • Large intestine is difficult to empty due to too much water being reabsorbed in the colon – waste hardens. • Cardiac sphincter stretches and stomach acid splashes walls of esophagus. • Burning and pressure in chest • Caused by overeating, acidic foods, or caffeinated beverages • Not enough water is absorbed out of waste before egestion • Usually caused by bacteria • Results in watery feces • Could cause SEVERE DEHYDRATION • Inflammation of the appendix • Could be very dangerous if it ruptures • Accumulation of hardened cholesterol in the gall bladder • Hepatitis (Inflammation/ Infection of the liver) • Type A , B, & C • Cirrhosis • Distorted or scarred liver as a result of chronic inflammation or drinking and drug use Question #1 The principal function of the large intestine is to: 1.Produce salivary amylase 2.Produce bile 3.Store bile 4.Reabsorb water from feces Question #2 Choking on food is most likely caused by an interference with the proper functioning of the 1. Diaphragm 2. Oral cavity 3. Esophagus 4. Epiglottis Question # 3 What is the role of teeth in digestion? 1. They break down food mechanically, increasing the surface area of the food for enzyme action. 2. They break food down mechanically, stimulating enzyme synthesis in the food. 3. They break down food chemically, aiding in the movement of food down the esophagus. 4. They break down food chemically, mixing saliva with the food for easier digestion. Question # 4 In the human body, hydrochloric acid is responsible for the low pH of the contents of the 1. Lungs 2. Kidneys 3. Pancreas 4. Stomach Question # 5 In humans villi that absorb small, soluble nutrients into the bloodstream are found in the 1. Large Intestine 2. Small Intestine 3. Esophagus 4. Stomach Question # 6 Bile is a secretion produced by the liver, which aids in the emulsification of 1. Lipids 2. Proteins 3. Sugars 4. Starches Question #7 Feces is usually about 40% water and 60% solid matter. Reducing the water content to 20% would most likely result in 1. Diarrhea 2. Ulcers 3. Gallstones 4. Constipation