Digestive System

Do It Now 1. What are the two functions of an animal digestive system? (2 points) 2. Write the following in correct order and briefly list its function: Anus, rectum, mouth, stomach, esophogus, small intestine, large intestine (16 points) 3. Where are villi and microvilli found? (1 point) 4. What is the function of villi and micro villi? (1 point) Extra credit: What is chyme?

Collect 24 hours data Decant liquid down the drain. Throw away bag. Put stuff back where you got it!!!

Function Take in food Take in food Process food - Digestion Process food - Digestion Absorb nutrients Absorb nutrients

Homeostasis of Blood Glucose What are the two main nutrients carried by blood for cellular respiration? What are the two main nutrients carried by blood for cellular respiration? Why must blood glucose levels be maintained at a certain level? Why must blood glucose levels be maintained at a certain level?

Nutrition Animals must supply carbon skeletons necessary to build all needed molecules. Animals must supply carbon skeletons necessary to build all needed molecules. Animals must supply themselves with essential nutrients that can not be made with their enzymes. Animals must supply themselves with essential nutrients that can not be made with their enzymes. Minerals and vitamins Minerals and vitamins

Ingestion – Where is the animal in the Food Web Herbivores – eat only plants, mouthparts adapted to their food source, coevolution with bacteria and protists to digest cellulose, longer small intestine Herbivores – eat only plants, mouthparts adapted to their food source, coevolution with bacteria and protists to digest cellulose, longer small intestine Carnivores – eat only animals, mouthparts, shorter small intestine Carnivores – eat only animals, mouthparts, shorter small intestine Omnivores – somewhere in between! Omnivores – somewhere in between!

Feeding Mechanisms Suspension feeding – food particles removed from water Suspension feeding – food particles removed from water Substrate feeding – live on the food source e.g. leaf miners, dung beetles Substrate feeding – live on the food source e.g. leaf miners, dung beetles Deposit feeding – earthworms take in soil and remove organic material Deposit feeding – earthworms take in soil and remove organic material Fluid feeding – mosquito, leaches Fluid feeding – mosquito, leaches Bulk feeding – large meals, not much chewing Bulk feeding – large meals, not much chewing

Food Processing Ingestion – Digestion – Absorption Ingestion – Digestion – Absorption Ingestion – teeth – dentition, tongue Ingestion – teeth – dentition, tongue Digestion physical or chemical – hydrolytic enzymes Digestion physical or chemical – hydrolytic enzymes Absorption – once food is broken down, the materials must be absorbed and transported throughout the body. Absorption – once food is broken down, the materials must be absorbed and transported throughout the body.

Intracellular Digestion Paramecium example Paramecium example paramecium paramecium paramecium

Gastrovascular Cavity Hydra and planarian Hydra and planarian

Alimentary Canal Mouth  Esophagus  Stomach  Small Intestine  Large Intestine  Rectum  Anus Mouth  Esophagus  Stomach  Small Intestine  Large Intestine  Rectum  Anus Mouth digestion of starch via amylase Mouth digestion of starch via amylase Stomach – pepsin begins digestion of protein into smaller polypeptides Stomach – pepsin begins digestion of protein into smaller polypeptides Small intestine – breakdown and absorb nutrients Small intestine – breakdown and absorb nutrients Large intestine – reabsorption of water and minerals Large intestine – reabsorption of water and minerals

Gastrointestinal System Function-physical and chemical breakdown of food Includes alimentary canal and accessory organs Accessory organs: Salivary glands, tongue, teeth, liver, gallbladder, and pancreas

Alimentary canal Mouth- physical and chemical breakdown. Mastication-the act of chewing Saliva contains enzyme amylase to break down carbohydrates

Pharynx- contains opening to trachea as well. Epiglottis covers opening of trachea. Esophagus-muscular tube dorsal to trachea Relies on a rhythmic wave-like motion called peristalsis

Esophagus- transverse view

Sphincter-a circular muscle that constricts a passage or closes a natural orifice (opening) Cardiac sphincter Pyloric sphincter Food sits in stomach for 1-4 hours. Gastric juices contain hydrochloric acid- activates pepsin, kills bacteria.

Small intestine: not so small! 20ft x 1’’ Duodenum- 1 st 10 inches. Bile and pancreatic juice enter here Jejunum- next 8 ft. Ileum- final 12 ft. When food leaves small intestine, digestion is complete

Small intestine has lots of enzymes: peptidases maltase, sucrase, lactase, amylase. Lipase Bile Digested food is absorbed into the bloodstream.

Large intestine- 5 ft x 2’’. Separated from small intestine by ileocecal valve Final absorption of water, storage of indigestible material, absorption of vitamins B and K by bacteria. Colon connects to rectum- anal canal opens to the anus (final opening). Fecal material is expelled.

But Wait! What about the accessory organs: Liver, gall bladder and pancreas Liver- largest gland in your body Secretes bile- emulsifies fat, makes them water soluble. Stores glucose in the form of glycogen Makes clotting proteins Detoxifies blood

Gall bladder- stores and concentrates bile Pancreas- produces insulin, pancreatic juices amylase and lipase. Insulin regulates the uptake of glucose by the cells

Questions 1. What parts of the model accurately portrayed the action of the digestive system? 2. How could we improve this model of digestion? 3. What organs are play a part in digestion, but are not present in the alimentary canal?

Stomach example Physical churning Physical churning Acid released by cells in response to the hormone Gastrin that is released when a person eats. Acid released by cells in response to the hormone Gastrin that is released when a person eats. Pepsinogin is also released by separate cells – the acid in the stomach changes the shape of pepsinogin to its active form pepsin. Pepsin stimulates more acid – positive feedback. Pepsinogin is also released by separate cells – the acid in the stomach changes the shape of pepsinogin to its active form pepsin. Pepsin stimulates more acid – positive feedback. Acid and Pepsinogin do not mix until they reach the lumen of the stomach or else it would digest the stomach. Stomach lumen is coated with mucus to protect it. Acid and Pepsinogin do not mix until they reach the lumen of the stomach or else it would digest the stomach. Stomach lumen is coated with mucus to protect it.

Stomach continued The food + water + acid and enzymes = acid chyme which passes to the the duodenum of the small intestine. The food + water + acid and enzymes = acid chyme which passes to the the duodenum of the small intestine. Ulcers – most caused by a bacteria called Helliobacter pylori treated with antibiotics Ulcers – most caused by a bacteria called Helliobacter pylori treated with antibiotics

Small Intestine Duodenum – beginning of small intestine the chyme is acidic, digestive enzymes are secreted by the pancreas, liver, and gall bladder (bile), but are active in a neutral pH. Cells add Sodium bicarbonate to neutralize the acid chyme. Duodenum – beginning of small intestine the chyme is acidic, digestive enzymes are secreted by the pancreas, liver, and gall bladder (bile), but are active in a neutral pH. Cells add Sodium bicarbonate to neutralize the acid chyme. Jejunum – villi and micro villi absorb nutrients Jejunum – villi and micro villi absorb nutrients

The End of the Line 7 liters of liquid are passed through the stomach and small intestine each day. 7 liters of liquid are passed through the stomach and small intestine each day. Much is reabsorbed by microvilli into lacreal cells in the small intestine. Much is reabsorbed by microvilli into lacreal cells in the small intestine. More water and minerals are reabsorbed by the large intestine. More water and minerals are reabsorbed by the large intestine. Food digestion takes hours. Longer = less water, Shorter = more water Food digestion takes hours. Longer = less water, Shorter = more water

And then More cellulose in the diet = faster movement. More cellulose in the diet = faster movement. E. coli lives in the large intestine on undigested food. The bacteria produce vitamins and some strains help to fight off infections by out-competing the bad guys. E. coli lives in the large intestine on undigested food. The bacteria produce vitamins and some strains help to fight off infections by out-competing the bad guys.

Interesting Adaptations Herbivores have a longer cecum – usually with symbiotic prokaryotes and protists that digest cellulose. Herbivores have a longer cecum – usually with symbiotic prokaryotes and protists that digest cellulose. Rabbits have their symbionts living in their large intestine instead. They eat the digested food (poo) from the first time around and the typical pellets you see are food that has been through twice. Rabbits have their symbionts living in their large intestine instead. They eat the digested food (poo) from the first time around and the typical pellets you see are food that has been through twice.

Ruminents Deer, cows, horses Deer, cows, horses They have a four chambered alimentary canal. They end up “chewing the cud” cud is made up of food after it has been metabolized by the protists and bacteria. They have a four chambered alimentary canal. They end up “chewing the cud” cud is made up of food after it has been metabolized by the protists and bacteria. It passes through the digestive system again. It passes through the digestive system again. Ruminents actually get most of their nutrition from the digestion of the microorganisms living inside of them! Ruminents actually get most of their nutrition from the digestion of the microorganisms living inside of them!