Test 1: Small and Large Intestine Flashcards
Why are ruminants unable to digest plant material directly?
they lack the enzyme to break down cellulose in plant cell walls.
In how many chambers does ruminant digestion occur? Name them.
4 chambers:
- rumen
- reticulum
- omasum
- abomasum
What are the non glandular parts of the ruminant stomach?
- rumen
- reticulum
- omasum
What is the name of the terminal glandular stomach of the ruminant?
abomasum
What is the first part of the ruminant stomach? What is its function? What is its appearance?
RETICULUM:
- HONEYCOMB appearance
- moves food into the rumen and omasum
- causes regurgitation of injesta
- collection compartment for foreign objects
What is the largest part of the ruminant stomach? What is its function? What is its appearance? What is produced?
RUMEN:
- leaf like PAPILLAE
- storage compartment
- facilitates microbial (bacterial and protozoal) fermentation of injesta
- Volatile fatty acids are biproducts which are absorbed and serve as a direct energy source
What is produced in the rumen?
volatile fatty acids
- directly accessible energy source
What type of material is digested in the rumen? How? What is the purpose of this digestion?
carbohydrates
- microbial fermentation
- purpose: produce ATP for bacterial protein synthesis and growth
- Volatile fatty acids are absorbed through the rumen into the portal vein and are carried to the liver
What are the different types of microorganisms in the rumen?
- bacteria
- protozoa
- fungi
What is needed for the digestion of cellulose?
microorganisms such as bacteria, fungi and protozoa.
What do rapid changes in feed affect in the ruminant stomach?
the microflora of the forestomachs
What do rumenal bacteria digest?
- main: cellulose
- starch
- sugars
- other plant material
What is the living condition of rumenal bacteria?
completely anaerobic (obligate anaerobes)
What vitamins do rumenal bacteria synthesize?
B vitamins
B for Bacteria
Where do large amounts of bacteria end up in?
abomasum
How are rumenal bacteria classified? Based on what factor?
Rumenal bacteria are classified based on what nutrients they metabolize.
- cellulolytic
- hemicellulolytic
- amylolytic
- proteolytic
- sugar utilizers
- ammonia producers
- vitamin synthesizers
- methane producers
How do ruminants produce methane? What else comes with the methane?
CO2 + H2 + CH4
Explain the structure of rumen protozoa.
- large
- single celled
- microscopic cillia (help push food towards their mouth)
- obligatory anaerobes
- eat large amounts of starch at a time
- store starch in their bodies
- 50% of rumen
- 40x the size of rumenal bacteria
What do rumen protozoa store? What does this help in?
- store starch
- slows down the production of acids (rumen pH doesn’t get too low)
What do rumen potozoa feed on? What does that help in?
- starch (not as much acid is produced)
- bacteria (prevents bacterial overgrowth)
What do rumenn protozoa produce?
fermentation end products:
- acetate
- butyrate
- hydrogen
Where do rumen methane bacteria live? Why?
on the surface of rumenal protozoa, for immediate access to hydrogen
Explain the location of rumenal protozoa. Why?
- slower moving fiber mat of the rumen
- so that they aren’t washed out before they multiply
- multiplication is very slow (15-24h) in comparison to bacteria (13min)
What may reduce the number of protozoa in the rumen?
- low roughage diets
- reduce retention of fibers
Explain features of rumen fungi. Conditions? Function? Nutrition?
Conditions:
- multiple types of fungi (both anaerobic and aerobic)
- attach to food particles
- reproduce slowly
Function:
- split fibrous material (making it more accessible for bacteria)
- fermentation
Nutrition:
- recieved from bacteria
Explain the function of the omasum. What is its structure?
- contains numerous LAMINAE (tissue leaves)
- grinds ingesta
- reduce particle size
- absorb water
- absorb VFA
- prevent abomasum buffering
Explain the function of the abomasum. What is its structure? What is its function?
- true gastric stomach
Structure:
- 3 regions: cardiac, fundic, pyloric
- pH: 2.6
Function:
- digestive secretions
- proteolytic enzymes
- HCl
- denatures proteins
- kills bacteria and pathogens
- dissolves minerals
- gastric digestion
Explain the layering of content in the rumen of cows
gas
fiber mat (intense fermentation)
intermediate zone (intense fermentation)
liquid zone (moderate fermentation)
What types of contractions occur in the reticulorumen?
1) MIXING contractions (primary contractions)
2) contractiosn related to RUMINATION (transport of forestomach content to the oral cavity for chewing)
3) contractions related to ERUCTATION OF GAS (secondary contractions)
What is rumination? Purpose? Differences depending of diet?
transport of forestomach content to the oral cavity for additional chewing:
- reduces size of feed particles
- expose new surfaces to fermentation
- rich fiber diet=longer fermentation
How much gas do ruminants produce in a 24h period?
2000-4000L
What organs secrete digestive juices into the small intestine?
accessory glands:
- pancreas
- liver
- gallbladder
How does the small intestine and its nearby organs protect themselves from digestive enzymes?
produce inactive forms of enzymes which are only activated in the duodenum.
What are the two main functions of the pancreas?
- exocrine function
- endocrine function
What is the exocrine function of the pancreas?
- secretes pancreatic juice into the small intestine
- produce sodium bicarbonate (neutralizes gastric contents in the duodenum)
- zymogen granules (in acinar cells) produce digestive enzymes
What is the endocrine function of the pancreas?
- secretes insulin and glucagon (regulate blood sugar and carbohydrate metabolism)
What are the major pancreatic enzymes? What do they digest? Into what?
- amylase (polysaccharides–>disaccharides)
- lipase (triglycerides–>fatty acids)
- nuclease (nucleic acids–>nucleotides)
- proteinases (peptides–>amino acids) (all secreted in their inactive form)
Explain the activation of enzymes in the duodenum.
trypsinogen + enterokinase –> trypsin (active)
trypsin + chymotrypsynogen –> chymotripsin (active)
trypsin + proaminopeptidase –> aminopeptidase (active)
trypsin + procarboxypeptidase –> carboxypeptidase (active)
What are the two major hormones regulating pancreatic proteases in the small intestine? What is their function?
CCK- induces secretion of pancreatic enzymes
Secretin- induces secretion of HCO3-
What are the function sof the liver?
- lipid metabolism
- production of bile (fat emulsification)
- carbohydrate metabolism (glycogenesis, glycogenolysis)
- storage of glycogen, iron, and vitamins A, D, B12
- pcontains phagocytes (destroy damaged erythrocytes and foreign substances)
- blood reservoir
- coagulation blood factors
- cholesterol production
- converts and inactivated toxic substances
What is bile? What is it composed of?
- yellowish-green alkaline solution
- contains bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytes
- chief bile pigment: billirubin (waste product of heme)
What is the function of bile?
- emulsify fats
- facilitate fat and cholesterol absorption
- help solubilize cholesterol
Explain the position of the gall bladder.
- inferior,
- visceral surface of the liver
What is the function of the gall bladder?
stores and concentrates bile secreted by the liver
Explain the species differences related to the gall bladder.
dogs, cats, humans:
- fat digestion is intermitent
- unnecesary continuous bile presence
- gall bladder facilitates the transfer of large quantities of bile salts to the small intestine during digestion + continuous transport of waste products from the hepatocytes to the bile
horses, ruminanats:
- continuous digestion- flow of bile does not fluctuate
- horses lack a gallbladder
- ruminants have a gall blader with a short retention time and poorly concentrating mechanism
Explain the regulation of bile release.
- chyme enters duodenum
- CCK and secretin released (bloodstream)
- production of bile stimulated in liver
- weak contractions of gall bladder (caused by vagal stimulation)
- CCK’s cause gallbladder contraction + hepatopancreatic relaxation
- bile enters duodenum
Explain the adaptations of the small intestine depending on species differences.
carnivores: shorter
herbivores: longer
Explain the adaptations of the large intestine depending on species differences.
hind hut fermantation depending on structure and size
Where is the small intestine located? What are its parts? What is its function?
Location:
- from pyloric sphincter
- to ileocecal valve
Division:
- duodenum
- jejunum
- ileum
Functions:
- digestion (intestinal glands)
What are the different intestinal enzymes? What do they digest? Into what?
- maltase: maltose–>glucose
- sucrase: sucrose–>glucose + fructose
- lactase: lactose–>glucose+galactose
- peptidase: peptides–>amino acids
- lipase: triglycerides–>fatty acids+glycerol
- nuclease: nucleotides–>nitrogenous bases
- enterokinase: trypsinogen–>trypsin
How are intestinal secretions stimulated?
- gastrc juice
- chyma
- distension of the small intestine
Explain the structure of villi. What does it absorb?
blood capillaries:
- absorb water (osmosis)
- glucose (active transport)
- amino acids (active transport)
- vitamins & minerals (active transport)
- short chain fatty-acids (passive diffusion)
lymphatic capillaries:
- long chain fatty-acids (passive diffusion)
Explain the differences in absorption depending on the location in the small intestine.
duodenum:
- amino acids,
- vitamins,
- lipids
- glucose and other sugars
jejunum:
- carbohydrates
- proteins
ileum:
- vitamin B12
- bile salts
- remaining nutrients
What are the types of contractions in the small intestine? What are their functions?
types:
- segmentation (mixes intestinal content)
- peristalsis (moves intestinal content)
function:
- mix content
- ensures lumenal content comes in contact with epithelial cells
- transports chyme along the digestive tract
Explain the process of segmentation. What is segmentation? What it its function?
- most common type of contraction in the small intestine
- ring-like contractions occuring simultaneously at regular intervals
Function:
- divides intestinal content into many small segemnts
- mixing of injesta with digestive juices
- bring new content into contact with absorptive surfaces
Explain the process of peristalsis. What is peristalsis? When is it initiated? How? What it its function?
- waves of contractions (moving from one part of the GI tract to the next)
- initiated when a segment of the intestine recieves chyma
expansion stimulates:
- contraction of circular muscle (proximal to stimulated part)
- receptive relaxation (distal to stimulated part)
function:
- displacement of chyme
How is the small intestine regulated?
1) Neural Regulation:
- parasympathetic nerve activity: increases contraction strength
- sympathetic nerve activity: weakens contraction strength
- peristalsis
- segmentation
2) Reflex Regulation:
- feed composition
- emotions
3) Humoral Regulation:
- gastrin, motilin, CCK, seratonin, histamin, bradicinin, VIP, NT
What is peristalsis and segmentation regulated by?
the enteric nervous system
What sphincter is present at the transition between the small intestine and the colon? What else do some species have to prevent the retrograde flow of the colonic content?
ileocecal sphincter
(one way gate)
some species: mucosa in the sphincter forms a flap
Explain the large intestine. Where is it located? What are its species differences? What does it consist of?
- tube between the terminal ileum and anus
species differences:
- horse, ruminant, pig: ileocecal valve
- dogs: ileocolic valve
Structure:
- cecum
- colon
- rectum
dog- collie
What are the functions of the large intestine?
- absorption of water and ions
- microbial digestion
- absorption of carbohydrates and proteins
- digestion (microbial enzymes)
- produce HCO3 and mucin
HCO3- neutralization of organic acids (formed by fermentation)
Explain the digestion occuring in the large intestine depending on diet differences.
Carnivores:
- large intestine is of small significance
- digestion completed in the small intestine
Herbivores and Omnivores:
- microbial degredation processes are very important
- rabbit: fermentation in the cecum (COPROPHAGY)
- horses: fermentation in colon
rabbit- ceCUM ; horse-COLon
What types of contractions occur in the large intestine?
- segmentation (haustrastion contractions)
- peristalsis
- antiperistalsis (retard movement of injesta- absorption of water and electrolytes)
- mass movements (intensive and prolongued peristaltic movements- strips area clear of contents)
Explain the rectum. Where is it located? What glands does it have? What stimulates its contractions?
- terminal portion of the colon
- mucous-secreting glands
- sensory receptors detect stretching/distension and trigger defacation
carnivore and omnivore rectum- empty most of the time
Explain the anus. What controls the passage of feces? Voluntary? Involuntary? What stimulates contractions?
- internal and external sphincters control the passage of feces
- dogs&cats- voluntary control (early life)
- ruminants, horses, birds- involuntary
- parasympathetic signals stimulate contractions (colon and rectum)
- smooth muscle cells in the internal sphincter relax
- defecation occurs
What are the parts of the bird digestive system?
1) beak, mouth, pharynx
2) esophagus, crop
3) proventriculus, gizzard
4) small intestine
5) cecum
6) colon & cloaca
7) pancrease
8) liver
Where does the fiber microbial degredation occur in birds?
ceca
What do birds have which have fiber-rich diets?
large ceca
What birds have specifically good fiber digestibility?
ostriches, geese, and ducks
Explain the crop. What is it? Where is it located? What is its function?
- pouch-like enlargement of the esophagus
- food is temporarily stored (later passed onto stomach in small, regulated portions)
- neutral pH
- allows the degradation of starch (with salivary amylase and bacterial fermentation)
What is the proventriculus?
the ‘true stomach’
- glandular stomach
- place where digestion occurs
In birds, what marks the end of the jejunum and the start of the ileum?
Merkel’s diverticulum
Explain the ceca in birds. What is it? What is its function?
ceca=plural of cecum
- blind pouches at the junction of the small and large intestines
function:
- reabsorption of water
- fermentation
- production of B-vitamins
- minimal absorption and nutrient release
What occurs in the large intestines of the birds?
large intestine is short!
- empties into cloaca
- fecal material is voided by the vent
- water reabsorption
- fiber fermentation (bacteria)
- H2O soluble vitamin synthesis (bacteria)
What happens in the rectum and cloaca?
absorption of water and ions
What do bird feces contain? What is it transported in?
- white crystals of uric acid
- transported with the urine
- colloidal suspension
