Animal nutrition

Chapter 41

Function

1. Digestion2. Absorption of nutrients/water– Energy– Growth

3. Elimination

Mechanicaldigestion

Chemicaldigestion(enzymatichydrolysis)

Nutrientmoleculesenterbody cells

Undigestedmaterial

INGESTION

DIGESTION

ABSORPTION

ELIMINATION

1

2

3

4

Heterotrophs

Intracellular digestion

Extracellular digestion

Extracellular digestion

Fig. 41-9

Esophagus

Mouth

Pharynx

Crop Gizzard

Typhlosole

Intestine

Lumen of intestine

Anus

(b) Grasshopper

Foregut

(c) Bird

(a) Earthworm

Midgut Hindgut

Esophagus RectumAnus

Mouth

Crop

Gastric cecae

Esophagus

Mouth

Crop

Anus

StomachGizzard

Intestine

Digestive system

General structure

Gastrointestinal tract (tube)Mucosa: inner layer (epithelial)Submucosa: connectiveMuscularis: 2 layers of muscleSerosa: outer layer (connective)Plexues: nerves located in the submucosa

Digestive organs

MouthPharynxEsophagusStomachSmall intestine (duodenum, jejunum, ileum)Large intestine (cecum, ascending colon, transverse colon, descending colon, sigmoid, rectum, anus)

Digestive organs

Accessory organsLiverGallbladderPancreas

Digestion

MouthTeethGizzard (in birds to help grind food)Salivary glandsSecrete saliva Amylase (enzyme to breakdown starch)

Mouth

Salivary glands

Digestion

Chew or mastication Tongue pushes food PharynxEpiglottis closesEsophagus

Pharynx

Esophagus

EsophagusMuscular tubeConnects pharynx to stomachPeristalsis:Rhythmic movement of muscle contractions Moves food alongEsophageal sphincter:End of esophagus keeps food in stomach

Stomach

Mucosa lining (epithelial)Parietal cellsSecrete H + Cl ionsChief cellsSecrete pepsinogenPepsinogen is converted to pepsinDigests proteins

Stomach

Gastric juices:HCl, pepsinogen & mucus pH=2Chyme: Mixture of partially digested food

Stomach

Stomach

Small intestine

ChymeLeaves stomach via pyloric sphincterDuodenum Digestive enzymes from pancreasBile from liver & gallbladderMost digestion occurs in the duodenum & jejunum

Intestines

Small intestine

Small intestines

Villi along intestine epitheliumMicrovilli“brush border”Aids in absorptionSecretes enzymesBreak disaccharides (sucrose, lactose)

Small intestine

Accessory organs

Accessory organs

PancreasSecretes fluids via pancreatic ductExocrine systemTrypsin & chymotrypsin (proteases)Amylase (starch)Lipase (fats)Bicarbonate (neutralizes HCl)Endocrine (insulin and glucagon)

Accessory organs

LiverSecretes bileContains bile pigments & bile saltsBile pigments are waste from break down of RBCEliminated

Accessory organs

Bile salts Emulsify the fatsBile made in liverStored in gall bladderReleased when eat fatty mealGallstones can block release

Small intestines

Monosaccharides, aa are transported to the blood capillariesHepatic portal veinLiverHeart Transported to body

Small intestines

Fatty acids & monoglycerides Villi TriglyceridesChylomicrons: (triglyceride & protein coat) Lymph system

Fig. 41-15bMicrovilli (brushborder) at apical(lumenal) surface

Key

Nutrientabsorption

Bloodcapillaries

Epithelialcells

Villi

Lymphvessel

Basal surface

Lacteal

Epithelial cells

Lumen

Fig. 41-16Lumenof smallintestine

Lacteal

Chylomicron

Phospholipids,cholesterol,and proteins

Triglycerides

Monoglycerides

Triglycerides

Fatty acids

Epithelialcell

Essential nutrients

Oral cavity,pharynx,esophagus

Stomach

Lumen ofsmall intes-tine

Epitheliumof smallintestine(brushborder)

Carbohydrate digestion

Polysaccharides

Smaller polysaccharides,maltose

Polysaccharides

Maltose and otherdisaccharides

Disaccharides

Protein digestion Nucleic acid digestion Fat digestion

Proteins

Small polypeptides

Pepsin

Pancreatic amylases

Salivary amylase

Disaccharidases

Monosaccharides

Small peptides

Amino acids

Amino acids

Polypeptides

Smallerpolypeptides

Pancreatic trypsin andchymotrypsin

Pancreatic carboxypeptidase

Dipeptidases, carboxypeptidase,and aminopeptidase

DNA, RNA

Pancreatic nucleases

Fat globules

NucleotidesFat droplets

Nucleosides

Nitrogenous bases,sugars, phosphates

Nucleotidases

Nucleosidasesandphosphatases

Glycerol, fattyacids, monoglycerides

Bile salts

Pancreatic lipase

(starch, glycogen) (sucrose, lactose)

Large intestines

Absorbs waterAbsorbs vitamin KConcentrates wastesE. coli FecesCloacaCombines feces & urine wastes in some animals

Large intestine

Large intestine

Veins to heart

Lymphatic system

Hepatic portal vein

Liver

Mouth

Esophagus

StomachLipids

Absorbed food(except lipids)

Absorbedwater

Secretionsfromsalivaryglands

Secretionsfromgastricglands

Small intestine

Secretions from liver

Secretions from pancreasLargeintestine

Anus

Rectum

Food

BMRBasal metabolic rateObesityHeart disease, diabetes, strokeAnorexia, Bulimia

Essential nutrients

Essential aa Minerals VitaminsA, B-complex, C, D, E, KScurvy, rickets, pernicious anemia, bleeding

Abnormalities

UlcersH. pyloriBacteria Treated with antibioticsReflux:Gastric juices go backwards to esophagus

Hiatal hernia

Pyloric Stenosis

Colon Cancer

Jaundice