Flashcards in Digestive system Deck (95)
List in sequence the sections of the digestive tract
1. Oral cavity (mouth/jaws/lips/tongue/teeth)
2. GI tract - Oesophagus, Stomach, SI, cecum, LI (colon), rectum, anus
Most important feeding structure of vertebrates?
Part of tooth visible above gum
Define dental pulp
connective tissues, nerves & blood vessels
hard outer substance of tooth.
Inorganic crystals, irreplaceable
Dental formula of dog (upper & lower)?
Dental formula of sheep (upper & lower)?
muscle mass covered in mucous membrane
stratified, squamous epithelium covered in papillae
Different forms of papillae?
Define prehension and structures involved
Act of getting food into mouth - lips, tongue
1st act of digestion
initiates mechanical breakdown
Motility of mouth enables slicing, tearing, grinding & mixing food
What does mastication stimulate?
Secretion of saliva, gastric juices, bile, pancreatic juices
Swallowing - relaxed upper oesophageal sphincter & closed soft palate
Draw micro-anatomy of the SI
What are the 2 levels of control of the GIT?
Extrinsic - ANS
Intrinsic (enteric) - unique to GIT; nervous & endocrine components
T or F - ANS nerves form link with enteric NS
T or F - extrinsic nerves originate within the GIT
false - outside the GIT
ANS influences GIT motility how?
1. modifies ongoing activity thru intrinsic plexus
2. alters levels of GIT hormone secretion
3. Acts directly on SM & glands
Properties & functions of the oesophagus?
To push boluses of food from pharynx to stomach
Contains mucus -> prevents damage
Muscle type in dog & ruminant oesophagus
Muscle type in bird & human oesophagus
Muscle type in horse, cat & pig oesophagus
striated at origin then to SM
Draw stomach & label
Learn and distinguish differences between GIT of ruminant & non-ruminant...
4 compartments vs 1 compartments
much greater number of bacteria to aid in digestion
List the structures in the horse large intestine
Caecum, ascending colon, transverse colon, descending colon, rectum
Name the accessory digestive organs
Name the salivary glands
Endocrine portion of pancreas contains ... & secretes ...?
Islets of Langerhans & insulin/glucagon
Exocrine portion of pancreas contains ... & ... cells which secrete... & ...?
Acinar cells - digestive enzymes
Duct cells - sodium bicarb solution
Functions of the liver...?
Plasma protein synthesis
Secretion/modification of hormones/growth factors
Liver stores what?
glycogen, fat, iron, copper, vitamins
Know how to label structures of liver
... slide 47 & 48
Know components of the avian digestive tract
...slide 51 (lec objective)
Characteristics of motility?
Mixing ingested material with secretions
Peristalsis - circular muscle contracts & longitudinal muscle relaxes and vice versa
Rate of movement varies bwn feed/spp
Characteristics of secretion?
Release of useful substances in GIT lumen
Secretions: enzymes, buffers, bile, lubrication, solvent
Characteristics of digestion?
Breakdown into smaller molecules - mechanical/enzymatic
Aided by secretions
Characteristics of absorption?
nutrient uptake & use
uses specialised cells lining GIT lumen
passive or active
Segmentation (haustration) involves what?
Random, localised contraction of smooth muscle
Occurs in SI & colon
non-propulsive; instead mixes digesta
Most saliva secretion comes from where?
2 types of saliva secretions?
viscous - mucous rich (small glands)
serous - (parotids)
Which salivary glands secrete both (viscous & serous) saliva?
madibular & sublingual
T or F - Starch digestion begins in mouth due to amylose
False - amylase
Amylase digestion is high, low and absent in which animals?
High - pigs
Low - horses
Absent - ruminants
T or F - saliva provides alkaline buffer & fluid bicarbonate in the rumen
True - very important for ruminant digestion
T or F - salive provides evaporative cooling and oral protection
true - oral protection is due to buffer, lysosomes & antibacterial properties
Salivary center in medulla is stimulated by which factors?
Pressure receptors & chemoreceptors (mouth)
Cerebral cortex (sight of food ->'mouthwatering')
Cascade of events to stimulate saliva secretion...?
Visual/chemo-/pressure cues -> + salivary center -> + ANS -> + salivary glands -> + saliva secretion
Mucous cells secretions & role?
Alkaline mucous & protect mucosa
Chief cells secretions & role?
pepsinogen & protein digestion
Parietal cells secretions & role (2 secretions)?
Hydrochloric acid & activates pepsinogen
Intrinsic factor & facilitates absorption of vit B12
Enterochromaffin like cells (ECL) secretions & role?
Histamine & stimulates parietal cells
G cells secretions & role?
Gastrin & stimulates parietal, chief & ECL cells
D cells secretions & role?
Somatostatin & Inhibits parietal, G & ECL cells
Pancreatic enzyme properties...?
Potent enzymatic secretions
Aqueous alkaline secretions
VERY important in non-ruminants
Synthesised as zymogens (inactive enzymes)
3 principle types of pancreatic enzymes?
proteolytic (protein catabolism)
amylase (starch catabolism)
lipase (fat catabolism)
Describe the control of pancreatic sodium bicarb secretion
+acid in duodenum -> + secretin release (mucosa) -> +secretion of bicarb (pancreatic duct cells) -> duodenal lumen -> neutralises acid in duodenum
Describe the control of pancreatic digestive enzyme secretion
Fats & proteins in duodenum -> +CCK (mucosa) -> + secretion digestive enzymes (acinar cells) -> digests fats & proteins
Stored in gall bladder (not stored in horse)
Know SI anatomy diagram on slide 22 (lec 2)
In the small intestine, what impairs digestion & absorption?
Loss of surface area (villous atrophy)
Why is physical breakdown of food important?
Reduces particle size
Enlarges surface area
Reduction of food particles occurs where?
Chemical digestion involves...?
Complex nutrients -> simple ones
Chemical digestion of CHO breaks which bonds?
Chemical digestion of proteins breaks which bonds?
Chemical digestion of fats breaks which bonds?
Chemical digestion of nucleic acids breaks which bonds?
Describe luminal phase of monogastric digestion (non-fibrous CHO)
Dietary polysaccharides such as starch & glycogen broken down in GI lumen by salivary & pancreatic AMYLASE into maltose & sucrose.
Describe membraneous phase of monogastric digestion (non-fibrous CHO)
Maltose, sucrose & lactose -> monosaccharides by brush border enzymes -> glucose & galactose absorbed apical membrane by Na+ cotransport. Fructose by facilitated diffusion
Describe monogastric protein digestion & absorption (3 steps)
1. Dietary & endogenous protein ingested -> hydrolysed by pepsin & pancreatic proteolytic enzymes
2. AAs across apical membrane via Na+/K+ pump
3. Small peptides absorbed by different carrier -> AAs by aminopeptidases or intracellular peptidases
Consider drawing monogastric protein digestion (3 steps)
Consider drawing monogastric CHO digestion
Describe lipid digestion & absorption in monigatrics
1. TGs emulsified in SI by bile (duodenum)
2. Pancreatic lipases hydrolyse TGs -> monoglycerides & FFAs
3. Micelles formed by lipase & bile carry monoglycerides & FFAs -> luminal surface
4. Micelles release monoglycerides & FFAs near epithelial surface -> passive diffusion thru lipid bilayer
Consider drawing monogastric lipid digestion
Properties of large intestine...?
absorb water & electrolytes
microbial CHO & protein digestion
mucosal glands -> buffer & mucous
What does hind gut fermentation in horses produce?
VFAs = energy
Draw diagram of rumen and label compartments
Role(s) of the rumen...?
fermentation - anaerobic, pH, temp, removes indigestible material & products of digestion
Role of reticulum?
'Honeycomb' appearance - movement of material, fluid etc.
Role of omasum?
Spherical shape - laminae grind roughage & squeeze fluid out of ingesta
Role of abomasum?
True 'glandular' stomach - enzymatic digestion
2 main types of motility in the rumen?
Primary contractions - mixing
Secondary contractions - eructation of gas
T or F - regurgitation is not considered a motility pattern
3 main steps to ruminate...?
1. Regurgitate - rumen & reticulum contract -> recently eaten food away from oesophagus replacing it with semi-liquid partially fermented -> reverse peristalsis up oesophagus
2. Remasticate - only some matter ->reinsalivate
What is fermentation? Briefly describe...
Metabolic action of bacteria & other microorganisms
Microbial enzymes hydrolyse large molecules
What are the key features of ruminant & hindgut fermentation?
CHO most important E source
osmolality (ionic strength) optimum range
anaerobic (-ve red-ox potential)
removal of ingestible material
rate of microbial removal = microbial regeneration
VFAs buffered or removed
5 major groups of microbes?
CHO digestion in the rumen...?
Microbial fermentation -> Acetate, Butyrate, Propionate
T or F - SCFA account for between 30 - 50% digestible E intake
False. 50 - 70%
Why is propionate important?
Increased roughage -> ?
Protein digestion in the rumen...?
Proteins -> AAs -> microbial protein prod. & ammonia prod.
Can -> VFA prod.