Digestive Syste Mmmmm Digestion Mechanical and chemical breakdown

Digestive Syste. Mmmmm

Digestion: Mechanical and chemical breakdown of foods so that nutrients can be absorbed by cells Consists of the alimentary canal, leading from the mouth to the anus, and accessory organs whose secretions aid the process of digestion

Functions of the digestive system • • • Ingestion of food Mechanical breakdown of food particles Chemical breakdown of food particles Absorption of nutrients Elimination of waste

The Alimentary Canal • Muscular tube 9 meters long, passes through ventral cavity

Movement of the Alimentary Canal Peristalsis! Mixing Propelling*

1. Which of the following is an accessory organ? a) b) c) d) e) Mouth Stomach Esophagus Liver My brain

Alimentary Canal Regions: Mouth • Mouth: first part of the alimentary canal • Functions to receive food and begin mechanical and chemical digestion – Mastication (chewing) – Enzymes

Alimentary Canal Regions: Mouth • Tongue – Covered with taste buds within papillae, which also provide friction to move food around – Attached to floor of mouth by frenulum • Tonsils – Lymphatic tissue – fight infections – Palatine, lingual, pharyngeal (adenoids)

Alimentary Canal Regions: Mouth • Teeth – Two sets develop in sockets within alveolar processes of the maxillary and mandibular bones – The 20 primary teeth are shed in the order they appeared and 32 permanent teeth replace them – They begin mechanical digestion

Accessory Organs: Salivary Glands • Salivary Glands – Secrete saliva, a substance which has mucus and enzyme components – Enzyme secreted: amylase (carbohydrate digestion) Parotid Submandibular Sublingual

Alimentary Canal Regions: Pharynx and Esophagus • Pharynx – Cavity posterior to the mouth – Connects to the esophagus • Esophagus – Muscular tube that leads to the stomach – Has esophageal sphincters – Powerful peristalsis!

Swallowing Mechanism • Swallowing Reflex – Food forced into pharynx by the tongue – Sensory receptors sense food, which triggers swallowing reflex (medulla and pons) – Peristalsis transports food through the esophagus to the stomach

Alimentary Canal Regions: Stomach • Stomach: J-shaped muscular organ that receives and mixes food with digestive juices, and propels food to small intestine • Three sections: Fundus, Body, Pylorus

Gastric Secretions • • Gastric glands within the mucosa of the stomach open up as gastric pits Gastric glands secrete 1. 2. 3. 4. • Mucous Pepsin (protein digestion) HCl Also secrete intrinsic factor, necessary for vitamin B 12 absorption in the small intestine Regulated by: 1. 2. The hormone gastrin (increases) Food entering small intestine (decreases) • Cholecystokinin released from small intestine

Gastric Actions • The stomach does very little absorption – Absorbs small amounts of water, salts, alcohol, and lipid -soluble drugs • Mixing and emptying actions – After a meal, mixing actions turn the food into a creamy paste called chyme – The rate at which the stomach empties depends on the fluidity of the chyme and the type of food

Sphincter says what? • Esophageal Sphincter • Pyloric Sphincter • Ulcers

1. The parasympathetic nervous system a) b) c) d) e) 2. A chief cell secretes HCl into the stomach to aid in digestion a) b) 3. True False Carbohydrate digestion begins in the mouth a) b) c) 4. Promotes digestion Inhibits digestion Promotes release of gastrin A and C only B and C only True False eeny miney mo… Which is NOT a part of the tooth? a) b) c) d) e) Dentin Enamel Cementum Peridontal ligament Dental conchae

Accessory Organs: Pancreas • The pancreas has the exocrine function of secreting pancreatic juice which aids digestion

Pancreatic Juice • Contains enzymes that digests proteins, fats, carbohydrates, and nucleic acids • Pancreatic enzymes include: – – • Pancreatic amylase (carbs) Pancreatic lipase (lipids) Trypsin, chymotrypsin, carboxypeptidase (proteins) Nucleases (nucleic acids) Regulated by – Endocrine and nervous systems – Secretin (hormone) – Cholecystokinin (released from wall of sm intestine)

Accessory Organs: Liver • The liver is the second largest organ in your body! • The liver functions in metabolic activities, storage of nutrients, filtration of blood, and chemical digestion – Performs over 500 jobs, and makes over 1000 essential enzymes!!

Liver Functions • Metabolic activities: – Synthesis, breakdown, or conversion of carbohydrates, lipids, and proteins – Detoxification (eg. ammonia urea) • Stores: – Glycogen, vitamins A, D, B 12, iron, and copper • Filters the blood, removing damaged RBCs, foreign substances, toxins • Secretes bile for digestion

Bile Composition • • Bile is a yellow-green liquid that hepatic cells secrete Contains water, bile salts, bile pigments, cholesterol, and electrolytes – Bile pigment bilirubin is from breakdown of heme (hemoglobin) – Only bile salts involved in digestion Stored in gall bladder Release controlled by cholecystekinin (released by cells of sm intestine wall) Bile salts emulsify fats and make them easier to digest and absorb

Alimentary Canal Regions: Small Intestine • • Receives secretions from pancreas and liver Completes digestion of chyme Absorbs the products of digestion Transports the remaining residue to the large intestine MAJOR SITE OF ABSORPTION!! 90% food fuel and water Consists of duodenum, jejunum, and ilium Attached to posterior abdominal wall by double layered peritoneum called mesentary

Structure of Small Intestinal Wall • Lined with villi – Increase surface area, help in mixing actions

Villi and Microvilli

Regulation of Small Intestine Secretions • Mechanical and chemical stimulation from chyme stimulates goblet cells to secrete mucous • Distention (stretching) of intestinal wall stimulates parasympathetic reflexes that stimulate secretions from the small intestine – Cholecystekinin • Movements: – Peristalsis – Segmentation

Alimentary Canal Regions: Large Intestine • The large intestine absorbs water and forms and stores feces • Ascending Colon, Transverse Colon, Descending Colon, Sigmoid Colon, Rectum Doesn’t digest or absorb nutrients Secretes mucous and absorbs water and electrolytes Diarrhea – often due to infections/irritants; leads to malabsorption or increased motility Contains important intestinal flora which synthesize vitamins

1. Which does the small intestine do? a) b) c) d) e) 2. Cholecystekinin a) b) c) d) e) 3. Peristalsis Segmentation Chemical digestion A and C only All of the above Inhibits bile release into small intestine Is released from the small intestine Prevents pancreatic juice release Stimulates increased digestion in the stomach Has way too many syllables The liver is involved in a) b) c) d) e) Metabolism Storage Bile production Detoxification All of the above

Nutrition and Nutrients

Diabetic Food Pyramid: Groups foods based on their protein and carbohydrate content (eg. potatoes and beans in the “grains” box, cheese in the “meats” box)

Healthy Living Food Pyramid

Nutrition and Nutrients • Nutrition: Process by which the body takes up and uses nutrients • Nutrients: Food/chemicals that we need to live and grow – Essential nutrients: nutrients our cells cannot synthesize; must take in from the outside (eg. food) – Macronutrients, vitamins, minerals

Carbohydrates • Sugars and starches used for energy • Ultimately want glucose (simple sugar) for use in cellular respiration Get 38 ATP per glucose in aerobic respiration All carbs are absorbed as monosaccarides. Only macronutrient that is not essential to the diet A lot of controversy regarding carbs in today’s society!

Carbs to Blame? • Changes in the western diet linked to obesity and inflammatory bowel diseases • Evolution hasn’t had time to catch up to the industrial and agricultural revolutions! IBD: Rising prevalence in Western culture, virtually non-existent in cultures maintaining primitive diets Childhood Obesity (tripled since 1980)

Lipids • Includes fats, phospholipids, and steroids • Used for energy and energy storage, cell membranes, hormones Fats serve as compact energy storage Need to eat fats to absorb fat-soluble vitamins (A, D, E, K) Unsaturated – plant origin HDL vs LDL Saturated – animal origin Cholesterol – only in animal fats Saturated vs unsaturated Hydrogenated and trans fats

Proteins • Polymers of amino acids • MANY functions (enzymes, antibodies, hormones, clotting factors, etc) • Amino acids can also be a source of energy if necessary • Absorbed in the duodenum and jejunum Complete vs incomplete proteins Food combining to get all essential AAs

Vitamins • Organic compounds necessary for normal metabolism – Often co-factors or activators for enzymes – Not produced in adequate amounts by cell – Need to ingest • Fat soluble (A, D, E, K) and water soluble (C, B-vitamins) Vitamin A

Minerals • Derived from the soil and used in metabolism • Concentrated in bones and teeth – Calcium and phosphorus most common (75% by weight of minerals in our body) – Other minor minerals: potassium, sulfur, chlorine, magnesium

Poop

1. Trans fats increase LDL production a) b) 2. Essential vitamins are naturally produced by our cells in adequate amounts a) b) 3. True False A, C, E, and B-12 are all fat-soluble vitamins? a) b) 5. True False Vitamins are often co-factors for enzymes a) b) 4. True False Poop JUST happens a) b) True False

Body Mass Index • Calculations BMI = • weight (kg) height 2 (m) According to guidelines from the National Institutes of Health (NIH), a normal BMI range is 18. 5 to 24. 9. A BMI of 25 to 29. 9 is considered overweight, and a BMI of 30 or more is considered obese.