Lecture 5 Flashcards
What is a species adaption in the oesophagus?
Species adaptations
Ability to control
peristaltic
contractions
◆ Reverse peristalsis
◆ Amount and location of
skeletal muscle
◆ Regurgitation vs. vomiting
In horses eosophagus can they belch out gas or vomit?
no they cant
Whats dogs eosaphagus muscles like?
Striated muscles throughout allow GREAT control of digesta
movement both directions
Whats different about ruminants oesophagus?
Different from monogastric esophagus
– Striated muscle along the entire length
* Provides greater strength
* Allows some voluntary control
– Funnel shaped
* Contains three sphincters active in rumination
and eructation
Whats the stomach regions?
-Oesophageal (Non-Glandular)
-Cardiac (secreted muscle)
-Fundic (Parential cells and cheif cells)
-Pyloric (Mucas)
What are the different muscles in the stomach?
-Longitudinal muscle
-Circular muscle
-Diagonal muscle
-Pyloric sphincter
Whats functions of gastric digestion
Reservoir for controlled release of digesta to small
intestine
* Horse has small capacity – requires increased number of
smaller sized meals
– Mixing food & mechanical breakdown of feed
– Hydrolytic digestion by acid and enzymes
* Mainly protein
– Kill most bacteria
– Hormone production
What does gastric fluid consist of?
-Mucas
-Hydrochloric acid
-Pepsinogen
What does mucas do in stomach?
coats and protects the lining of the
stomach.
What does hydrochloric acid do in the stomach?
kills most harmful
substances that have been ingested and it also
converts pepsinogen into pepsin
What is pepsin?
it is a protein digesting enzyme that breaks
large protein chains into smaller chains
Name the 4 secretions in the stomach?
-HCL (-Decrease’s pH -Denatures protein - Kills most bacteria -activated pepsinogen)
-Mucus (-Protects lining from acid and enzymes -No “autodigestion” -Lubricant)
-Pepsinogen (-activated form in pepsin -Hydrolyses)
-Rennin (abomasum, clots milk)
-Lipase (-some species)
What are gastric pits formed by?
-Formed by numerous folds in the
epithelium
- Glands empty into the gastric pit
- Many types of glands may empty
into one gastric pit
What does the acidity of the stomach allow pepsin to do?
To function and make the HCL effective at killing pathogens
What do mucus cells secrete ?
Secrete mucus to protect
epithelial cells from enzymes
& acid
What do parental cells secrete?
HCL
What do chief cells secrete?
Secrete pepsinogen which
gets converted to “pepsin”
when mixed with HCl; for
protein digestion
What do entero- endocrine cells secrete?
Secrete gastrin to regulate
stomach emptying
What 3 things controls gastric secretions and gastric mobility?
- Cephalic phase
- Gastric phase (chemical phase)
- Intestinal phase
1- What is the Cephalic phase? (2)
Vagal reflex:
It is induced by thinking , smelling , tasting or chewing food
Implies involvement of CNS (via release of acetylcholine , histamine and gastrin )
Increased saliva production, gastric mobility, enzyme and HCL secretion
2- What is the Gastric phase (aka Chemical Phase) and an example: (3)
This is a local reflex, it depends on presence of food in stomach eg: dietary protein stimulates G cells to release gastrin
-Its reinforced by gastrin (peptide hormone secreted by stomach)
-Increases HCL secretion
3- What is the intestinal phase (2)
-Stimulated by duodenal , distension, decreased pH, osmolarity, nutrients (fat and carbs)
-Decreases HCL secretion and gastric motility (cholecystokinin (CCK) is released by the small intestine
What are the two gastric mobility and emptying actions?
1- Mobility aids mixing , mechanical and hydrochloric reduction of feed to chyme
2- Emptying is stimulated by distension of antral wall and presence of liquid chyme
Why is the stomachs pH 2-3?
The acidity allows pepsin to
function and makes the HCL
effective at killing pathogens
What does HCL convert in the stomach ?
Converts pepsinogen to pepsin
What does pepsin in the stomach activate?
activates more pepsinogen starting a chain reaction. pepsin begins the chemical digestion of proteins
Whats acid reflux caused by?
Its caused by acid that’s found in the stomach that helps break down food , it rises up into the gullet .
Unlike the stomach the gullet doesn’t have a protective lining and so it becomes sore and inflamed
What type of secretion does the cardia gland secrete?
Mucous
What type of secretion does the pylorous or Antrum gland secrete?
Mucous
What type of secretion does the fundus chief and parental cells secrete?
Enzyme acid
What’s the main constituents of the mucous in the cardia gland?
Mucin
What’s the main constituents of the mucous in the pylorous or Antrum gland?
Mucin
What’s the main constituents of the enzyme acid in fundus cheif and pariental cells gland?
Pepsinogen acid to pepsin HCL
What are the 3 phases for the control of gastric secretions and gastric motility
1- Cephalic phase
2-Gastric phase (chemical phase)
3- Intestinal phase
Name the 4 gastrointestinal hormones:
1- Gastrin
2- Secretin
3- Cholecystokinin (CKK)
4- Gastric Inhibitory Protein (GIP)
Where is the origin of gastrin hormone?
Stomach/abomasum (G-cells of antrum)
What stimulates gastrin?
Food in stomach
Whats the function of gastrin?
-It stimulates HCL and pepsinogen secretion,
-increases stomach mobility
Where does the hormone secretin originate?
It originates in the duodenum
What stimulates secretin?
HCL from the stomach
What is the function of Secretin?
It stimulates pancreatic secretions, slows stomach mobility and acid production
Where is the origin of cholecystokinin (CKK)
The origin is the duodenum
What stimulates cholecystokinin (CKK)?
Fat and protein in the duodenum
Whats the function of cholecystokinin (CKK)?
It stimulates bile and pancreatic secretions, it also regulates appetite and feed intake
Where is the origin of the gastric inhibitory protein (GIP)?
The origin of gastric inhibitory protein (GIP) is in the duodenum
What does the gastric inhibitory protein (GIP) stimulated by?
its stimulated by fats and bile
What’s the function of the gastric inhibitory protein(GIP)?
it inhibits stomach mobility and secretion of acid and enzymes
What sort of communication is there between the SI and the stomach?
Coordinated and “cross talk” ,
they “govern” the amount of digestia delivered to the small intestine
Want to maximise the digestion and absorption in the SI
We DONT want excessive chyme “pushing” nutrients into the LI prior to them being fully digested and absorbed.
Name the 3 sections of the small intestine
Duodenum
Jejunum
Ileum
What happens in the small intestines ?
The majority of nutrients are absorbed into the bloodstream
-Same anatomy for monogastric and ruminants
What is the duodenum
Short, first segment that leaves stomach
-Recieves bile and pancreatic secretions
-Active site of digestion
Whats the jejunum?
Longest, makes up majority of the small intestines
-Active site of nutrient absorption
Whats the Ileum?
Short, enters the colon (LI)
Separated from colon by ileocecal sphincter
–Active site of nutrient absorption (minerals, water, vitamins)
-Some bacterial presence (fermentation)
Whats the Ileocecal sphincter?
Separates the Ileum from the colon
It regulates movement of materials from the small intestine into the colon or the caecum
Whats the pH of the small intestine?
it increases towards 7 as food moves from the duodenum to the ileum
Whats the PH of duodenum?
2.7-4
-Enzymes
-pH change
-flow rate regulation
Whats the PH of the Ileum?
7-8
-Absorption
-Limited fermentation
Whats the PH of the jejunum?
4-7
-Enzymes
-Absorption
What is present in the si wall? and whats it similar to?
Present: Mucosa, submucosa , muscularis, serosa
What does the musoc do in the small intestine wall?
it increases the surface area due to many folds and villi
What does each villi contain?
contains thousands of microvilli
What do microvilli do?
They have both digestive enzymes and
carrier molecules for nutrients, vitamins, and
minerals embedded in cell membranes
What do crypts do?
Puts mucous around each villis,
New cells are produced and pushed from the bottom of crypt to replace cells of villis
What are also present in the small intestinal wall
goblet cells present . Mucus helps with the from of ingesta
if you inhance the surface area what increases?
Nutrient absorption
What the surface area of the plicae circurlais
3x
What the surface area of the villi
10x
What the surface area of the microvilli brush border
200x
What size is the gut surface area ?
The same as 2 tennis courts
What is the time frame from cell migration from the crypts to the tips of the villus?
2-3 days
What do the aborpative epithelial cells contain?
Contain brush border on the lumen/apical side
What does the brush border contain?(2)
-Enzymes
-Nutrient transport molecules
What do goblet cells do?
They secrete mucus (3 litres a day)
What are the 2 specialised cells in the lining villi?
-Endocrine cell
-Paneth cell
What does the endocrine cell secrete ?
Hormones into bloodstream or local cells
What do paneth cells secrete?
Secretes granules with anti-microbial properties
What secretions are secreted within the Small Intestine?
-Intestinal mucus
-Brush border enzymes
-Pancreatic juices
What secretions enters the small intestine from the ducts?
-Bile
Where’s bile produced?
In the liver
Where is bile stored ?
Gallbladder
What animals have no gallbladder?
Horses
-there is direct bile secretion into duodenum
-Horses cannot store bile so that why they always have to have a continuous intake of food.
What gland secretes intestinal mucus?
Secreted by glands in the wall of the small and large intestine (goblet cells)
What does intestinal mucus act as?
acts as a lubricant and buffer to protect intestinal wall
What does intestinal mucus prevent?(2)
-self digestion
-microbes/pathogens from adhering to epithelium
What is the importance of the pancreas for digestion? (3)
Produces enzymes responsible for
-50% carb and protein digestion
-90% lipid digestion
-It also produces sodium bicarbonate for neutralisation of chyme in the duodenum
Whats the ph of the pancreas?
ph- 7.2-7.8
What enzymes are present in the pancreas?
-Amylase
-Lipase
-Proteases
-Nucleases
What is trypsinogen converted into?
Trypsin
What is chymotrypsinogen converted into?
Chymotrypsin
What is procarboxypeptidase converted to?
carboxypeptidase
Where bile secreted from in most species?
secreted from the bile ducts
Is bile an enzyme?
NOOOOO
What colour is bile? what ph is it?
-Green
-Alkine ph (nuetralize acidic chyme)
What is bile secreted by?
By the liver via the bile duct to duodenum (stored in the gallbladder except in horses)
Whats the composition of bile? (3)
-Bile salts
-Bile pigments
-Cholesterol
Whats bile function?
emulsifies fats
Whta % of bile is reabsorbed and returned to the liver?
95%
What is the principles site of absorption for amino acids, vitamins , minerals and lipids?
Small Intestine
Where does most absorption occur in the small intestine?
in the jejunum but some absorption occurs in all segments
Is digestion in the small intestine fast or slow?
rapid, within 30 mins after entering the small intestine
List the nutrient absorption procedures? (4)
-Diffusion
-Facilitated diffusion
-Active transport
-Pinocytosis or endocytosis
What does nutrient absorption depend on ?
-Solubility of the nutrient (fat vs water)
-Concentration or electrical gradient
-Size of the molecule to be absorbed
What is the large intestine composed of?
– Cecum
– Colon (ascending, transverse and descending: human)
– Rectum
Whats the function of the large intestine?
Fermentative digestion
* No enzyme secretion
* Relies on microbes or secretions washed out of the SI
What type of absorption occurs in the large intestine?
-Absorption of remaining water, VFA’S and minerals
What type of storage happens in the large intestine?
digestia storage
Is there protein absorption and microbial digestion in the large intestine?
NOOOOO
Can the large intestine be developed?
Degree of development is species dependent
Whats the primary function of the large intestine?
-Stores faeces until they can be eliminated
-Recover fluid and electrolytes
-Hindgut fermentation
Whats the function of the monogastric large intestine?
– Absorption of liquid
– Mass movements move fecal matter to anus
– Usually only a few times a day
* Associated with defecation
Where the monogastric cecum located?
Located at junction of small and large intestine
Whats the function of the monogastrics cecum?
similar to rumen in ruminants
– Microbial activity and digestion of feeds
* Contains a microbial population similar to the rumen
– Cellulolytic & hemicelluloytic bacteria
What happens in the ruminants large intestine?
Fermentative digestion
– Bacteria similar to rumen, but no protozoa
– Digestion in colon may account for as much as:
- 27% of cellulose digestion
- 40% of hemicellulose digestion
- 10% of starch digestion
What is the ruminants large intestine very important in what conditions?
conditions that increase the amount of
fermentative carbohydrate entering the large intestine
* Increased rate of passage of forages
* High grain diets
What % does the ruminants large intestine account for when it comes to VFA absorption?
-17% of total VFA absorption
What are VFA’s used for in ruminants large intestine?
primarily used as energy source
for large intestinal mucosa cells
What is the rectum ?
- Muscular area of large intestine used
for storage of feces and ultimately for
defecation
– Feces includes sloughed cells, undigested
food and microbial matter
What does Passive or Simple Diffusion mean?
- Water and small lipid
molecules pass freely
through membrane - Move down
concentration gradient
to equalize
concentrations
List the types of absorptive processes?
-Passive diffusion
-Facilitated diffusion
-Active transport
What is facilitated diffusion ?
1) Carrier loads particle
on outside of cell
2) Carrier releases
particle on inside of
cell
3) Reverse
What does facilitated diffusion allow?
Allows equalization of
concentrations across
membrane
What is active transport?
1) Carrier loads particle
on outside of cell
2) Carrier releases
particle on inside of
cell
3) Carrier returns to
outside to pick up
another particle
- Unidirectional
movement - Transports nutrients
against concentration
gradient
Is pepsinogen active in the stomach?
they are inactive, hydrochloride acid turns it into pepsin thats an active form that breaks down protein
What do cheif cells produce
pepsinogen
what to parental cells produce?
HCL
What phases increase gastric secretions and mobility?
-Cephalic phase
-gastric phase
What phase decreases gastric secretions and mobility ?
-Intestinal phase
what’s a hormone secreted by the stomach
gastrin ,
it also increases hcl secretion
What does the intestinal phase decrease?
HCL secretion and gastric mobility
Whats a hormone reselse by the small intestine (Duodenum) that negatively regulate stomach secretion
-CCK
-GIP
-Secretin
What stimulates CCK and GIP in the small intestine?
by the presence of lipids and carbohydrates
What stimulates secretion in the small intestine ?
Decreased pH
Whats the pancreas important for?
The release of secretions
Name the biggest part of the small intestine?
jejunum
What are crypt important for producing?
they are important to produce Epithelial Cell in the small intestine
IS there mucus in the small intestine and large intestine?
Yes, there is its protecting your gut
What cells secrete mucous in the intestinal tract?
Goblet cells
Whats intestinal music important for?
-Prevent self digestion
-Prevent harm in intestine from microbes
Whats pancreatic enzymes important for ?
carb, protein, lipid digestion
produces sodium bicarbonate for
neutralization of chyme in duodenum
What’s the primary function of bile?
Help emulsifies fats
Where the primary site of absorption ?
Small intestine
Where is the primary area of the SI where absorption occurs?
Duodenum
Name the primary part of the large intestine?
Large intestine - Colon
Does the large intestine secrete enzymes?
-No
Fermentation occurs
Is there absorptions of protein in the large intestine?
No
What cells can be in your faeces?
Sloughed cells as they are replaced every 3 days
How do molecules pass through simple diffusion ?
molecules pass from an area from high conc to low conc
Passive diffusion , does it need energy?
dosnt require energy
What type of transport requires energy?
Active transport,
Across the concentration gradient, Glucose passed y active transport
