Post on 14-Dec-2015
transcript
Animal Nutrition II (Ch. 41)
Guest lecturer: Letitia Reichart (Letty)
Keywords
• Roles of mouth, stomach, sm.&lg. Intestine in digestion
• Pepsin, pepsinogen• Villi, microvilli• Cecum• Cellulose• Cellulase
• Acid chyme• Enzymatic hydrolysis• Peristalsis
Mammalian Digestive System
• Alimentary canal
• Accessory glands– Salivary glands, pancreas, liver, gallbladder
• Food moved by peristalsis
Mouth (oral cavity)
• Mechanical– Teeth– Saliva
• Enzymatic– Salivary amylase –
breakdown of starch and glycogen
Throat (pharynx) & Esophagus
• Throat – junction to esophagus & trachea
– Epiglottis
• Esophagus – uses peristalsis to move food to stomach
Stomach
• Stores food
• Secretes gastric juices
– Acid chyme
Relaxedmuscles
Contractedmuscles
Stomach
Digestive mechanisms in stomach
• Mechanical
• Chemical
• Enzymatic
Esophagus
Stomach
Pyloricsphincter
Cardiacorifice
Liver
Gall-bladder
Pancreas
Mechanical
• Mixing and churning– Smooth muscle– Every 20 seconds
Esophagus
Stomach
Pyloricsphincter
Cardiacorifice
Chemical
• Hydrochloric acid (HCl)
• pH around 2– Also breaks food down
Enzymatic
• Pepsin– Breaks down proteins
Chief cells
Mucus cells
Parietal cells
Interior surface of stomach
Gastric gland
Why doesn’t pepsin digest stomach?
Gastric pit
Activation of pepsin
Pepsin(active enzyme)
Pepsinogen
HCl
Parietal cellChief cell
Stomach
• After mechanical and enzymatic digestion:
-Acid chyme (nutrient-rich broth)
- Pyloric sphincter to the small intestine Stomach
Pyloricsphincter
Cardiacorifice
Smallintestine
Small intestine• Most of:
– Enzymatic digestion occurs here
– Absorption of nutrients into the blood stream occurs here
Figure 41.21 p. 859 in CampbellOral cavity,pharynx,esophagus
Stomach
Lumen ofsmall intes-tine
Smaller polysac-charides, maltose
Polysaccharides Disaccharides
Carbohydrate digestion
Salivary amylase
Polysaccharides
Pancreatic amylases
Maltose and otherdisaccharides
Epitheliumof smallintestine(brushborder)
Disaccharidases
Monosaccharides
Protein digestion Nucleic acid digestion
Proteins
Fat digestion
Fat globulesDNA, RNA
Fat dropletsNucleotides
Bile salts
Pancreatic lipase
Pancreaticnucleases
Nucleotidases
Glycerol, fattyacids, glycerides
Nitrogenous bases,sugars, phosphates
Nucleosides
Nucleosidasesand phosphatases
Dipeptidases, carboxy-peptidase, and aminopeptidase
Amino acids
Amino acids
Small peptides
Pancreatic carboxypeptidase
Pancreatic trypsinand chymotrypsin
Smaller polypeptides
Polypeptides
Small polypeptides
Pepsin
Stomach
Pancreas
Liver
Gall-bladder
Duodenum ofsmall intestine
Intestinaljuice
Bile
Acid chyme
Pancreatic juice
Figure 41.19 p. 858 in Campbell
Pancreas• Secretes proteases into duodenum
Inactive form Active form
Trypsinogen Trypsin
Procarboxypeptidase Carboxypeptidase
Chymotrpsinogen Chymotrypsin
Why doesn’t the small intestine digest itself?
Pancreas
Activeproteases
Fig. 37.13
Lumen of duodenum
Membrane-boundenteropeptidase
Inactivetrypsinogen
Other inactiveproteases Active
proteases
Trypsin
Liver• Produces bile that is stored in gallbladder• Bile contain bile salts• Bile salts aids digestion and absorption of fats
Largecircularfolds
Vein carrying bloodto hepatic portalvessel
Muscle layers
Villi
Intestinal wall
Most nutrient absorption
occurs in small intestine
Structure of small intestine
Lacteal
Lymphvessel
Villi
Epithelialcells
Bloodcapillaries
MicrovilliMicrovilli(brush border)
Epithelial cells
• Aid in nutrient transport across epithelial cells of sm. intestine into bloodstream
Large intestine (colon)• Major function is to reabsorb water
Ascendingportion oflarge intestine
Ileumof small intestine
Rectum
AnusAppendix
Cecum
LargeIntestine
Here are a few review questions
What would happen if you had a defect in pepsin production?
What would happen if you had a defect in pepsin production?
• A. carbohydrate would not be digested well
• B. meat would not be digested at all
• C. perhaps decreased absorption of protein
What would happen if you had a defect in salivary amylase
production?
• A. You would die
• B. You would be unable to digest starch
• C. The pH of the stomach would be affected
• D. None of the above
What would happen if you had a defect in salivary amylase
production?
Which of the following would you least like to donate to science
while you are still alive?• A. Cecum
• B. Pancreas
• C. Reproductive organs
What would happen if you had a defect in small intestine
enteropeptidase?
What would happen if you had a defect in small intestine
enteropeptidase?• A. Pancreatic enzymes would not be
activated
• B. Liver enzymes would increased
• C. Your small intestine would become blocked
• D. None of the above
Variations of vertebrate digestive system
• Herbivorous mammals– Specialized fermentation chambers
Coyote vs. Koala
Smallintestine
Stomach
Cecum
Colon(largeintestine)
Carnivore Herbivore
Small intestine
Why does herbivory require specializations?
• Plant tissue– Harder to break up– Contains cellulose– Nutrients less concentrated than meat
Structure of cellulose
Only bacteria and protozoa can break down cellulose
Via the enzymecellulase
Cecum
• Pouch at junction between lg and sm intestine
• Large cecum in rabbits, some rodents, koala, horses
• Full of symbiotic bacteria
Stomach
Cecum
Colon(largeintestine)
Herbivore
Small intestine
Symbiosis
• “living together”
Cecum function
• Fermentation chamber
• Bacteria breakdown cellulose
• Feces must be reingested
Stomach
Cecum
Colon(largeintestine)
Herbivore
Small intestine