Monogastric digestion Flashcards
Function of teeth
Mechanically reduce particle size
Increases surface area
How many muscles in the tongue?
3
Function of the tongue
Manoeuvres food in the mouth
Moves feed to teeth for grinding and to the back of the mouth for swallowing
Can distinguish between feed and toxins by papillae or taste buds
Name the 4 salivary glands
Zygomatic
Parotid
Sublingual
Mandibular
Zygomatic salivary gland - Type of secretion and main constituents
Type of secretion = mainly mucous
Main constituents = Mucin
Parotid salivary gland - Type of secretion and main constituents
Type of secretion = Serous
Main constituents = water, enzymes
Sublingual salivary gland - Type of secretion and main constituents
Type of secretion = mucous or mixed
Main constituents = Mucin, water, enzymes
Mandibular salivary gland - Type of secretion and main constituents
Type of secretion = Mucous or mixed
Main constituents = Mucin, enzymes, water
Function of Salivary glands
Moisten feed (salt and water)
Lubrication (aids swallowing)
Starch and/or lipid digestion - Amylase and/or lipase
Venom/bacteria – kill prey
Function of Oesophagus
Transport of food from mouth to stomach
Uses peristaltic (wave contractions)
Oesophagus of a horse/pig
Striated muscles for first 2/3
Smooth muscle for last 1/3
In horse, oesophagus joins stomach at an oblique angle – cannot belch
Oesophagus of a dog
Striated muscles throughout
Function of Stomach
Reservoir for controlled release of digesta to small intestine
Mixing food
Mechanical breakdown of feed
Hydrolytic digestion by acid and enzymes - Mainly protein
Kill bacteria
Secrete intrinsic factor: needed for vitamin B12 absorption
Hormone production
Stomach regions
Oesophagus - Non glandular
Cardia - Secretes mucous
Fundus - Parietal cells - enzymes & chief cells - HCL & intrinsic factor
Antrum - gastric
Pylorus - mucus
List secretions of the stomach
HCl
Mucus
Pepsinogen
Lipase
Stomach secretion - HCl
Decreases pH (~2-3)
Denatures protein
Kills bacteria
Activates pepsinogen
Stomach secretion - Mucus
Protects lining from acid and enzymes
No “autodigestion”
Lubricant
Stomach secretion - Pepsinogen
Activated form is pepsin
Hydrolyses protein
Stomach secretion - Lipase
Some species
Lipid breakdown
Chyme
Semifluid mass ready for passage into SI
Function of gastric motility
Motility aids mixing, mechanical and hydrolytic reduction of feed to chyme
Gastric secretions and motility are controlled by
Cephalic phase - head
Gastric phase - stomach
Intestinal phase - Intestine
Cephalic phase
Vagal reflex:
Parasympathetic innervation
Increases gastric motility, enzyme secretion
Small increase in HCl secretion
Gastric phase
Local reflex, depends on presence of feed in stomach
Mainly mediated by gastrin
Increases HCl secretion
Intestinal phase
Stimulated by duodenal distension, pH, osmolarity, nutrients (fat)
Decreases HCl secretion and gastric motility
List the gastrointestinal hormones
Gastrin
Secretin
Cholecystokinin (CKK)
Gastric inhibitory protein
Gastrin
Origin: stomach
Stimulus: food in stomach
Function: stimulates HCl & pepsinogen secretion, increases stomach motility
Secretin
Origin: duodenum
Stimulus: acid
Function: stimulates pancreatic secretions. Slows stomach motility and acid production
Cholecystokinin (CKK)
Origin: duodenum
Stimulus: fat & protein in duodenum
Function: Stimulates bile and pancreatic secretions
Also regulates appetite and feed intake
Gastric inhibitory protein
Origin: duodenum
Stimulus: fats and bile
Function: Inhibit stomach motility and secretion of acid and enzymes
Segments of small intestine (proximal to distal)
Duodenum
Jejunum
ileum
Duodenum
Releases bile and pancreatic secretion
Active site of digestion
Jejunum
Active site of nutrient absorption
Ileum
Active site of nutrient absorption - Water, vitamins and minerals
Some bacterial presence - Fermentation
Paneth cell
Secretory granules with anti-microbial properties
Speed of digestion in the small intestine
Very rapid
Within 30 minutes of entering SI
What nutrients can be absorbed by diffusion in the small intestine?
Water and small lipid molecules
Secretions within the small intestin
Intestinal mucous
Brush border enzymes
Intestinal mucous
From Brunner’s glands in duodenum wall
Acts as lubricant and buffer to protect duodenal wall
Brush boarder enzymes
CHO: lactase, maltase, sucrose
Proteins: Dipeptidase, aminopeptidase
Function of liver
Production of bile
Protein, CHO, fat metabolism
Storage of Glycogen & Vitamins
Break down of toxic substances
Function of Pancreas
Produces enzymes responsible for:
- 50% of carbohydrate digestion
- 50% of protein digestion
- 90% of lipid digestion
Produces sodium bicarbonate for neutralisation of chyme in duodenum
Produces insulin
Pancreatic juice
Produced & stored in pancreas
Clear, watery juice
Enters duodenum via pancreatic duct
Aids in fat, starch, and protein digestion
Contains: HCO3- Trypsinogen – Pro-enzyme Chymotrypsinogen - Pro-enzyme Procarboxypeptidase – Pro-enzyme Amylase Lipase Colipase (lipase co-enzyme)
Large intestine - Segments
Cecum
Colon
Rectum
Large intestine - Function
Fermentative digestion
- No enzyme secretion
- Relies on microbes or secretions washed out of the SI
Absorption of water, electrolytes, minerals
Digesta storage
Movement of fecal mater to rectum for defecation
Vitamin synthesis
Monogastric cecum
Located at junction of small and large intestine
Function similar to rumen in ruminants
- Microbial activity and digestion of feeds
- Contains a microbial population similar rumen
- Cellulolytic & hemicelluloytic bacteria
Microbial cell proteins not available to host
- Fecal loss – coprophagy
Monogastric Rectum
Muscular area of large intestine used for storage of faeces and ultimately for defecation
Faeces includes sloughed cells, undigested food and microbial matter
Salivary glands in birds
Are poorly developed
Avian oesophagus
Enlarged area called crop
Ingesta holding and moistening
Location for breakdown for carbohydrate by amylase
Fermentation
Avian Proventriculus
Release of HCl and pepsin (gastric juices)
Ingesta passes through very quickly (14 seconds)
Avian Gizzard
Muscular area with a hardened lining reduces particle size
Muscular contractions every 20-30 secs
Includes action of grift – deliberately ingested
Avian ceca
Contain two ceca instead of one
Avian large intestine
Very short (5-10 cm) and empties into cloaca where fecal material will be voided via the vent
- Water resorption
- Fibre fermentation by bacteria
- Water soluble vitamin synthesis by bacteria
Main features digestive tract of horse
Large intestine (45%)
Where microbes are stored
Main features of digestive tract of dog
Large stomach
- Don’t need many microbes because don’t eat much plant material (meat is easy to digest)
Scavengers – can store food
Main features of digestive tract of cat
Large stomach
Tiny caecum
- (obligate carnivore – no plant material)
Main features of digestive tract of fish
Have pyloric ceca after stomach
- Where the digestive enzymes are
- Finger-like projections to increase surface area
Have a combined small/large intestine
