Unit 6 Feeding and DIgestion Flashcards
What are the Major Nutrient Molecules
water, proteins/amino acids, lipids, carbohydrates
Vitamins
- participate in catalysis
- solubility affect mode of uptake and potential toxicit
- some obtained from symbiotic bacteria (vitamin C, K, B12)
- Coprophagy - improves vitamin uptake
Essential Amino Acids
- eight of them
- must come from diet
- during starvation, protien comes from muscles
Lipids
- essential for membrane production
- animals cant produce omega-3 or omega 6
- must come from diet
steps of eating and digestion
- nutrient sensing
- mechanical digestion
- chemical processing
- egestion
The breakdown of energy
gross energy —-> indigestible energy (feces)
- digestible energy —–> unetabolizable energy (urine)
- -Metabolizable energy—> heat
- —net energy
Acquiring food
sensing- prey with Gustatory receptors, energy emitted as heat or light
- lateral line
- electromagnetic receptors
small partibles- filter feeding
large particles - chewing, capture and swallow
fluids and soft tissues- nectal, blood, milk and milk like secretions
Filter feeding
- Planktivorous fishes - filter water over fills and sieve out the flanction
- some frogs use mucous covered fileter plates on gills to entrap particles
Fluid feeding
- sucking (baby)
- cutting and licking (lamprey + vampire bat)
Solid feeding
- teeth, beaks, great variety
- carnivores, herbivores, omnivores
Solid feeding- teeth types
- usually undifferentiated in non-mammalian vertebrates (homodonts) - sharks, fish, amphibians, reptiles
- venemous snakes have specialized fangs to inject venom and elastic ligaments which allow their jaws to stretch
- mammalian teeth are very specialized (incisors, canines, and molars) (heterodonts)
3 basic types of Alimentary sytems
Batch reactors (hydra) Continuous-flow, stirred tank reactors (ruminants forestomach) Plug-flow reactors (human small instestine)- composition varies along the tube
Essential parts of the Alimentary system
- Headgut- mouth, buccal cavity, pharynx
- –receiving food - Foregut - esophagus, stomach
- —food conduction, storage and digestion - Midgut - small intestine
- ——chemical digestion, absorption - Hindgut - colon, rectum
- —water/ion absorption, defecation
Headgut
- salivary glands (mucins-lubrication, digestive enzymes)
- mastication: teeth, beak etc.
- tongue (unique to vertebrates)
taste buds
figure 7-16
Foregut
Esophagus - gizzard (some birds, some fish), crop (some birds)
- stomach - cellular level view
- –monogastric (carnivores, omnivores)
- –digastric (ruminants)
Gastric Pit
mucous neck cells ----mucus cheif cells --------Pepsin parietal cells -----HCl G-cell-------Gastrin -low pH is optimal for gastric enzymes
Men can pass gass, men pass Hot gas
Platypus and gastric brooding frog
-do not have low pH
Monogastric stomach
- pylorospasm and pyloric stenosis -infants
- gastroesophageal Reflux - Hcl irritates wall
- —avoid foods that stimulate stomach acid or relax sphincter
Ruminant Stomachs
esophagus—rumen—reticulum—–omasum—Abomasum—small intestine
Other examples of Foregut Fermenters
Kangaroo, sloth, colombus monkey
MIdgut
- most nutrient absorption occurs here
- duodenum (secretions), jejunum (secretions and absorption, ileum (absorption)
Anatomy of intestinal epithelium
- longitudinal smooth muscle
- circular smooth muscle
- epithelial layer: submucosa, mucosa
- villi
- microvilli
- tight junctions and desmosomes
- hormones and antimicrobial stem cells
HIndgut
- storage of undigested food, absorption of water, ions
- major site for bacterial digestion in herbivorous reptiles, birds, most herbivorous mammals
two types of hindgut fermenters
- colon fermenters: horses, zebras, tapirs, sirenians, elephants, rhinos, marsupial wombats
- cecal fermenters: rabbits, many rodents, hydraxes, howler monkeys, koalas, opossums
- terminates in rectum or cloaca
What is the largest exocrine and endocrine gland in the body
the gut
Two important layers in the gut secretion
-myenteric plexus, submucous plexus
Endocrine and Exocrine glands
- exocrine glands- secretes fluids through a duct onto an epithelial surface
- endocrine glands secrete substances (hormones) direction into the blood
What are three exocrine secretions
- Water and electrolytes
- Bile and Bile salts
- Digestive Enzymes
Overview of Exocrine secretions
- review slide on powerpoint
Water and Electrolyte secretions
- ~95% of GI secretions are water and mucus
- thin slippery mucus- lubricates, protects the lining of the gut
- primary secretions enter in the acinar lumen (end of an exocrine gland)
- –modifications in the duct produce the final secretory juice composed of water, ions mucus and enzymes
Acinar cells
- primary secretions from capaillaries around acinar cells
- secondary modification in ducts
The liver produces
- bile (water, cholesterol, lecithin, inorganic salts)
- bile salts (organic salts derived from Cholesterol)
- bile pigments (from hemoglobin breakdown)
Bile travel pathway
-through the hepatic duct to the gallbladder where it is stored
Function of Bile
- neutralization of acidic gastric juices
- facilitation of digestion of fats by breaking them down into small droplets (emulsification)
- dispersion of lipid-soluble vitamins for transport int he blood
- removal of waste substances from the liver, (hemoglobin pigments, cholesterol, steroids, hydrophobic drugs.
Hyperbilirubinemia
- increased bilirubin in blood (frome heme catabolism)
- Jaundice
- normaly excreted in urine (yellow) and feces (brown)
- causes yellow color of bruises
- Treatment? broken down by blue light
Digestive enzymes
- hydrolysis of polymeric food molecules
- proenzymes (zymogens): inactive form of enzymes which are cleaved to produce active forms
Proteases
- endopeptidases, exopeptidases (highly specific enzymes)
- pepsin (stomach))
- tripsin and chymotrypsin (released from pancrease to SI
Carbohydrases
- amylases- salivary glands, duodenum
- polysaccharidases
- glycosidases
- cellulase- duodum
Lipases
- degrade lipids into fatty acids plus mono and di-glycerides
- fat digesion: 3 steps
- -emulsification
- -formation of micelles
- -digestion by lipases
other types of digestive enzymes
-nucleases, nucleotidases, nucleosidases, esterases
what is the primary stimulus for secretion of digestive enzymes
- presence of food molecules
- triggers chemoreceptors along the GI tract
- cephalic influences also stimulate sectretions
Secretion differences in the mouth, stomach and intestines (control and speed)
- mouth = neuronal = fast
- stomach = neuronal and hormonal = medium
- Intestine = hormonal = slow
What are the salivary secretions?
-water, electrolytes, mucin, amylase, anitmicrobial agents (lysozyme, thiocyanate)
what controls salivary secretions
- cholinergic parasympathetic control
- suppression of secretion cause by sympathetic innervation
what are the three gastric secretions
- HCL
- Pepsin
- Gastric Mucus
Hcl secretion in the gastic intestinal tract
- produced by teh parietal cells of the gastric pits
- stimulated by parasympatheitc activity in the vagus nerve, gastrin, secretagogues in food
- alkaline tide may occur in blood pH after a large meal due to loss of H+ to gastric secretions
Pepsin secretion in the gastric intestinal tract
- endopeptidase with several gastric variants
- produces as pepsinogen by chief (zygomatic) cells
- under parasympathetic control of gastric branch of vafus nerve and hormone gastrin
Gastric mucus secretion
- protects gastric epithelium from digestion and from high acidity
- trapped electrolytes help to neutralize gastric acid
- from the goblet cells (mucous neck cells)
What are the three gastric secretion phases
- Cephalic Phase
- Gastric phase
- Intestinal phase
- Cephalic phase of gastric secretion
-secretion in response to sight, smell or taste of food or to conditioned reflex
- Gastric phase of gastric secrtion
- secretion of Hcl and pepsin in response to food in the stomach
- mediated by gastrine (endocrine) and histamine (paracine) which bind receptors on parietal cells
- gastrin is secreted by pyloric mucosa in response to protein-contaning chyme and stomach distention; it also stimulates stomach motility
- Intestinal phase of gastric secretions
- controled by enteric gastrin (inresponse to partially digested proteins in duodunum), vasoactive intestinal protien (VIP) and gastric inhibitory peptide (GIP) in response to fats, sugars in duodenum
Intenstinal and pancreatic Secretion
- small intestin: succus entericu
- -bunner’s glands- secrete alkaline mucus
- -crypts of lieberkuhn- secrete enzyme-rich alkaloid fluid
What controls the pancrease and its secretion
-peptide hormones from the upper intestine
-endocrine secriton: insulen
exocrine secretions: many numerous secrtion
What enzymes does the large intestine secrete
-none
Absorption pathway
-gut lumen–epithelial cell: apical surface -cytosol –basal surface– blood or lymphde
5 types of nutrient uptakes in the intestine
- simple diffusion
- facilitated diffusion
- active transport
- chylomicrons into central lacteal
- endocytosis
feeding enzymes (review slides_
- GLUT 2, SCLT ect
lipid transport in the body
-di/triglyceride surrondd by lipase –> micelle
micelle migrate to brush border and release their contents— triglycerides reassemble in smooth endoplasmic reticulum - exocytosis or chlomicron into the central lacteal
Nutrient Transport in the Blood
- through central lacteal (80% of chylomicrons)
- into capillaries which then drain to hepatic portal vein and travel to liver where glucose is converted to glycogen for storage
What occurs during fasting
- use up glycogen storage (hours)
- Catabolism of triglycerides and structural proteins (weeks)
- Gluconeogenesis, ketogenesis (weeks)
Day 2- blood-glucose stabilized, fatty acids 4X, ketones 100-300X
day 40 - ketones supply 2/3 of brain’s energy needs
Hibernation
- metabolic rates lowered (only replace protein structures)
- bears recycle urea nitrogen back into animo acids
Aerophagia
(burping)
Caused by excess air in the stomach or gases created by digestion
-relazation of the lower esophageal sphincter
—vents gastric air
Colon Canger
- develos in the cells lining the colon and/or rectum
- people who have a diet righ in fat and read meat are at a greater risk
- easy to treat but symptoms don’t manifest until later
Crohn’s Disease
- inflammatory bowel disease, characterized by abdominal pain, diarrhea and weight loss
- immune related disease in which the body’s immune system attacks the GI tract, possibly directed as microbial antigens
- large part of the risk is genetics as well as smoking an stress
Diarrhea
- osmotic diarrhea = excessive solutes in the lumen of the intestine prevents absorption of water
- secretory diarrhea - water secreted in the small intestine is not reabsorbed
- inflammatory and infectious = micobial or viral pathogens destroy intestine epithelial cells
- results do include bloody diarrhea and lower water reabsorption
Diverticulitis
- outpockets along the wall of the colon
- they become inflamed due to infection from waste blockage and bacteria build up
- symptoms= cramps and abdominal pain, chills or fever and alternating diarrhea and constipation
Gallstones
- hard crystalline masses that form int he gall bladder or bile ducts
- form when there is an imbalance in the substances that make bile
- symptoms= pain in upper abdomen and back, nauseau, vomiting bloating and indigestion
Gas
-bloating (small bowel bacteria overgrowth)
by large amount of bacterial growth within the small intestine which use up nutrients that would otherwise be absorbed causing malnourishment.
conditions causing this= crohns disease
diabetes and scleroderma
treatment = antibiotics, drugs that speed intestinal movement
Heart burn (acid indigestion)
-the burning senstion (irritation) of teh esophagus caused by stomach acid
caused by = the lower esophageal sphinctor does not tight as it shood from:
- —too much food in the stomach
- —too much pressure on the stomach (obesity, pregnancy, constipation)
as a result, food and digestive juices from the stomach flow backward up into the esophagus
Jaundice
-bilirubin–> bile pigment in fat layer under the skin
-normally involved in the breakdown of red blood cells
abnormal= disruption of the meabolism in livier or excretion–> bilirubin build-up
from:
1. liver damage
2. gallbladder blockage
3. Rapid destruction of RBC’s
Pyloral Spasms
- pyloric stenosis is a narrowing of the opening in the stomach leading to the small intestine - the muscle surronding the opening is enlarged
- when the stomach empties into the small intestine the muscle spasm, causing projectile vomitting
Vomiting
- controled by the bilateral vomitting centers with are located in the medulla
- recives signals from 4 major sources
1. CTZ
2. visceral afferents from the GI tract
3. Visceral afferents from outside the GI tract
4. Afferents from extramedullary centers in the brain
