Chapter 34- ANIMAL NUTRITION AND DIGESTIVE SYSTEM - PowerPoint Presentation

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Chapter 34-ANIMAL NUTRITION AND DIGESTIVE SYSTEM

General Biology IIBSC 2011

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modification of work by Julie Rybarczyk)Slide2

Types of Digestive SystemsHeterotrophs are divided into three groups based on their food sourcesHerbivores are animals that eat plants exclusivelyCarnivores are animals that eat other animalsOmnivores are animals that eat both plants and other animals234.1Slide3

Figure 34.2Herbivores, like this (a) mule deer and (b) monarch caterpillar, eat primarily plant material. (credit a: modification of work by Bill Ebbesen; credit b: modification of work by Doug Bowman)Slide4

Figure 34.3Carnivores like the (a) lion eat primarily meat. The (b) ladybug is also a carnivore that consumes small insects called aphids. (credit a: modification of work by Kevin Pluck; credit b: modification of work by Jon Sullivan)Slide5

Figure 34.4Omnivores like the (a) bear and (b) crayfish eat both plant and animal based food. (credit a: modification of work by Dave Menke; credit b: modification of work by Jon Sullivan)Slide6

Figure 34.5A gastrovascular cavity has a single opening through which food is ingested and waste is excreted, as shown in this hydra and in this jellyfish medusa.An alimentary canal (more advanced) has two openings: a mouth for ingesting food, and an anus for eliminating waste, as shown in this nematode.Invertebrate Digestive SystemsSlide7

Monogastric: Single chambered Stomach(a) Humans and herbivores, such as the (b) rabbit, have a monogastric digestive system. However, in the rabbit the small intestine and cecum are enlarged to allow more time to digest plant material. The enlarged organ provides more surface area for absorption of nutrients. Rabbits digest their food twice: the first time food passes through the digestive system, it collects in the cecum, and then it passes as soft feces called cecotrophes. The rabbit re-ingests these cecotrophes to further digest them.Figure 34.6Slide8

Vertebrate Digestive SystemsConsists of a tubular gastrointestinal tract and accessory organsMouth and pharynx – entryEsophagus – delivers food to stomachStomach – preliminary digestionSmall intestine – digestion and absorptionLarge intestine – absorption of water and mineralsCloaca or rectum – expel waste8

Monogastric stomachSlide9

Vertebrate Digestive SystemsAccessory organsLiverProduces bileGallbladderStores and concentrates bilePancreasProduces pancreatic juiceDigestive enzymes and bicarbonate buffer9Slide10

Vertebrate Digestive Systems-AvianThe avian esophagus has a pouch, called a crop, which stores food. Food passes from the crop to the first of two stomachs, called the proventriculus, which contains digestive juices that break down food. From the proventriculus, the food enters the second stomach, called the gizzard, which grinds food. Some birds swallow stones or grit, which are stored in the gizzard, to aid the grinding process. Birds do not have separate openings to excrete urine and feces. Instead, uric acid from

the kidneys is secreted into the large intestine and combined with waste from the digestive process. This waste is excreted through an opening called the cloaca.Figure

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Vertebrate Digestive System -RuminantsRuminant animals, such as goats and cows, have four stomachs. The first two stomachs, the rumen and the reticulum, contain prokaryotes and protists that are able to digest cellulose fiber. The ruminant regurgitates cud from the reticulum, chews it, and swallows it into a third stomach, the omasum, which removes water. The cud then passes onto the fourth stomach, the abomasum, where it is digested by enzymes produced by the ruminant.Figure 34.8Slide12

Parts of the Digestive System-Oral CavityDigestion of food begins in the (a) oral cavity. Food is masticated by teeth and moistened by saliva secreted from the (b) salivary glands. Enzymes in the saliva begin to digest starches and fats. With the help of the tongue, the resulting bolus is moved into the esophagus by swallowing. (credit: modification of work by the National Cancer Institute)Figure 34.9Slide13

Parts of the Digestive System-Mouth and TeethInside the mouth, the tongue mixes food with salivaMoistens and lubricates the foodContains salivary amylase, which initiates the breakdown of starchSalivation is controlled by the nervous systemTasting, smelling, and even thinking or talking about food stimulate increased salivation13Slide14

Parts of the Digestive System-Mouth and TeethSwallowingStarts as voluntary actionContinued under involuntary control When food is ready to be swallowed, the tongue moves it to the back of the mouthSoft palate seals off nasal cavityElevation of the larynx (voice box) pushes the glottis against the epiglottisKeeps food out of respiratory tract14Slide15

Parts of the Digestive System-EsophagusMuscular tube connecting the mouth to the stomachActively transfers food (called a bolus)from the mouth to the stomach through peristaltic movements.15Figure 34.10Slide16

Parts of the Digestive System-StomachThe human stomach has an extremely acidic environment where most of the protein gets digested. (credit: modification of work by Mariana Ruiz Villareal)Figure 34.11Slide17

Parts of the Digestive System-StomachSaclike portion of tractConvoluted surface allows expansion Contains 3rd layer of smooth muscles for mixing food with gastric juice3 kinds of secretory cellsMucus-secreting cellsParietal cellsSecrete HCl and intrinsic factor (for vitamin B12 absorption)Chief cellsSecrete pepsinogen (inactive form of pepsin) for protein digestion

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Parts of the Digestive System-The Small IntestineAbout 4.5 m long – small diameterConsists of duodenum, jejunum, and ileumReceives Chyme from stomachDigestive enzymes and bicarbonate from pancreasBile from liver and gallbladder18Slide19

Parts of the Digestive System-The Small IntestineVilli are folds on the small intestine lining that increase the surface area to facilitate the absorption of nutrients.Figure 34.12Slide20

Parts of the Digestive System-The Small Intestine-Accessory OrgansPancreas Pancreatic fluid is secreted into the duodenum through the pancreatic duct Enzymes to break down proteins, carbs and fatsBicarbonate neutralizes acidic chyme from stomachExocrine and endocrine glandLiver Body’s largest internal organSecretes bileemulsifies fats GallbladderStores and concentrates bile

Arrival of fatty food in the duodenum triggers the gallbladder to contract, causing bile to be transported through the common bile duct and injected into the duodenum20Slide21

Parts of the Digestive System-The Large IntestineThe large intestine reabsorbs water from undigested food and stores waste material until it is eliminated.Figure 34.13Slide22

Parts of the Digestive System-The Large Intestine (Colon)Much shorter than small intestine, but has larger diameterSmall intestine empties directly into the large intestine at a junction where two vestigial structures, cecum and appendix, remainNo digestion occursFunction to reabsorb water and remaining electrolytesPrepare waste for expulsion22Slide23

Parts of the Digestive System-The Large Intestine (Colon)/Rectum/AnusMany bacteria live and reproduce within the large intestine. Provide humans with Vitamin KFeces compacted and passed to rectumFeces exit anusSmooth muscle sphincter (involuntary)Striated muscle sphincter (voluntary)23Slide24

Figure 34.19Mechanical and chemical digestion of food takes place in many steps, beginning in the mouth and ending in the rectum.Overview of Digestive ProcessSlide25

Figure 34.14For humans, a balanced diet includes fruits, vegetables, grains, and protein. (credit: USDA)Nutrition and Energy ProductionSlide26

Organic PrecursorsCarbohydrates –primary source of organic carbonBroken down into glucose to provide energy for metabolic pathwaysExcess converted to glycogenProteins- provides source of organic nitrogenNeeded for nucleotides, nucleic acids, glycoproteins, etcLipidsNeeded for fat-soluble hormones and vitaminsNeeded for cellular membranesSlide27

Figure 34.16Digestion of carbohydrates is performed by several enzymes. Starch and glycogen are broken down into glucose by amylase and maltase. Sucrose (table sugar) and lactose (milk sugar) are broken down by sucrase and lactase, respectively.Slide28

Figure 34.17Protein digestion is a multistep process that begins in the stomach and continues through the intestines.Slide29

Figure 34.18Lipids are digested and absorbed in the small intestine.Slide30

Figure 34.15A healthy diet should include a variety of foods to ensure that needs for essential nutrients are met. (credit: Keith Weller, USDA ARS)Slide31

Essential NutrientsAnimal cannot manufacture these for itself but are necessary for health and so must be obtained in the dietVitaminsHumans, apes, monkeys, and guinea pigs have lost the ability to synthesize ascorbic acid (vitamin C)Amino acids – humans require 9Long-chain unsaturated fatty acidsVertebrates can synthesize cholesterol, a key component of steroid hormones, but some carnivorous insects cannotMinerals31Slide32

Digestive System ProcessesIngestionDigestion and AbsorptionCarbohydratesProteinsLipidsSlide33

Figure 34.19Mechanical and chemical digestion of food takes place in many steps, beginning in the mouth and ending in the rectum.Slide34

Figure 34.20Seeing a plate of food triggers the secretion of saliva in the mouth and the production of HCL in the stomach. (credit: Kelly Bailey)Neural Responses to FoodSlide35

Neural Responses to Food3 phases of gastric controlCephalicSensory input stimulates gastric and salivary secretionGastricPresence of food stimulates gastric secretions and contractionIntestinalPresence of food stimulates accessory organs (e.g. gallbladder, pancreas, liver) and the intestinal cells to secrete digestive e enzymes