Exam 6 Flashcards
What organs does the liver receive portal blood from?
S
S
SI
LI
P
The majority of the liver’s blood supply is venous blood from the gastrointestinal tract (spleen, stomach, small and large intestines, and pancreas), which is delivered to the liver via the portal vein
What cells synthesize bile acids in the liver?
How are bile salts recycled/recirculatec back to the liver?
Bile acids are synthesized from cholesterol by the hepatocytes, transported into the bile, stored and concentrated in the gallbladder, and secreted into the intestinal lumen to aid in the digestion and absorption of dietary lipids. Bile acids are then recirculated from the ileum back to the liver via the enterohepatic circulation.
What are the products of Hemogoblin degradation?
How is bilirubin conjugated and with what?
Biliverdin (Green) which is converted to Bilirubin
Bilirubin (Yellow): : bound to albumin in the circulation and then carried to the liver where it is taken up by the hepatocytes.
It is conjugated with GLUCORONIC ACID via enzyme UDP-glucuronyl transferase
Bilirubin in deconjugated to UROBILOGEN by bacterial enzymes. Some is recycled and the rest is excreted in the feces as UROBILIN and STERCOBILIN.
What is Jaundice and why do newborns can develop it?
It is a yellow discoloration of the skin and sclera of the eyes due to the accumulation of either free or gonjugated biliburin.
It can occur when there is an excessive destruction of RBCs that results in an increased production of bilirubin.
It can also occur due to the obstruction of bile ducts or with liver disease. The biliburin can’t be excreted and it is absorbed into the circulation.
The feces are light colored bc of the decreased amount of stercobilin while the urine is dark bc of high concentration of conjugated bilirubin in blood.
Newborns do not sinthesized UDP-glucunoryl transferase fast enough so they can have jundice.
Metabolic functions of the liver
Carbohydrates metabolism, proteins, and lipids.
Gluconeogenesis: the liver stores glucose as glycogen and releases it to the bloodstream when needed.
Protein metabolism: the liver sinthesizes the nonessential AAs and modifies AAs so that they may enter biosynthetic pathways for carbohydrates.
Synthesizes plasma proteins: Albumin and clotting factors. Persons with liver failure develop HYPOALBUMINEMIA
Concerts ammonia: to urea, which is excreted in the urine.
Lipd metabolism the liver participates in FAs oxydation and and synthesizes lipoproteins, cholesterol, and phospholipids. A portion of the cholesterol is converted into bile acids to help lipid digestion and absoprtion.
Detoxification in the Liver
What are examples of substances that are toxic to the body?
For example, bacteria absorbed from the colon are phagocytized by hepatic Kupffer cells and thus never enter the systemic circulation.
In another example, liver enzymes modify both endogenous and exogenous toxins to render them water soluble and thus capable of being excreted in either bile or urine.
These substances are presented to the liver via the portal circulation, and the liver modifies them in so-called “first pass metabolism”
What are Cytochrome P-50 enzymes and what is their function?
What are the conjugating substances?
Phase I reactions, which are catalyzed by cytochrome P-450 enzymes, are followed by phase II reactions that conjugate the substances with glucuronide, sulfate, amino acids, or glutathione.
Intestinal fluid and electrolyte transport
Where do we absorb electrolytes and which ones are they?
In the small intestine and colon we absorb Na+, Cl-, HCO3-, H2O, and K+
What cells secrete electrolytes?
Epethilial cells lining the crypts of the SI. These secretions contribute to the volume already in the intestinal lumen, which must be absorb.
The permeability of the tight junctions between epethilial cells determines whether fluid and electrolytes will move via paracellular or cellular route. The “leaky” junctions permit paracelluar transport.
Where does the major absorption of Na+ occur?
What is the net absorption in the JEJUNUM?
What type of transporters are present in the luminal and basolateral membranes?
What is the source of H+?
JEJUNUM net absoprtion is NaHCO3-
The mechanism consists of Na+ dependent coupled transporters (sodium comes in the cell)
The apical (facing the lumen) membrane also contains monosaccharide cotransporters (N+ glucose, glalactose, N+ ammino acid, and N+/H+ exchanger).
Na+/K+ ATPase to basolateral membrane (blood side)
Source of H+ is intracellular CO2+ H2O, which is converted to HCO3- and H+
H+ is secreted in the lumen on the N+/H+ echanger and the HCO3- is absorbed in the blood.
What type of transport mechanisms are present in the Ileum?
What is absorb in the Ileum?
It contains the same mechanisms as the Jejunum
Additinally it contains the Cl- HCO3- exchange mechanism in the apical membrane
Cl- transporter on the basolateral membrane (instead of the HCO3-)
Both HCO3- and H+ are secreted to the luminal side via Cl-/HCO3- echanger
The result is movement of NaCL into the cell, where it is absorb
The colon and similarities to renal principal cells and absorption
Na+ absorption and K+ secretion
It is induced by aldosterone
Increase number of Na+ channels allows Na+ entry across apical membrane, which leads to increase K+ pump into the cell via Na+/ATPase. Ultimately, leads to secretion of K+ and it is dependent on the flow rate. It can cause HYPOKALEMIA due to high flow rate of intestinal fluid and diarrhea.
Intestinal secretion and diarrhea
Na+/Cl-/K+ cotransporter
The Cl- channels of the apical membrane are typically closed, but they may open due to hormones or neurotransmitters such as, Ach, VIP. Activation of cAMP opens the Cl- channels initiating secretion, Na+ and H2O follow. Normally intestinal Villi cells absorb it but cholera causes severe diahrrhea.
Diarrhea leads to loss of ECF, decreased arterial pressure. The RAAS system is activated by the baroreceptor mechanisms in attempts to restore BP.
Hyperchloremic metabolic acidosis with normal anion gap
Decreased surface area diarrhea
Osmotic diarrhea
Secretory diarrhea
Decreased surface diarrhea: includes infections and inflammation of the small intestine cuasing decreased absorption of fluid by the gastointestinal tract
Osmotic: is cuased by the prescence of nonabsorbable solutes in the lumen such as lactose instead od glucose and fructose from lactase deficiency.
Secretory: example, cholera. The cholera toxin moves across the basolateral cell membrane where it catalyzes ADP ribosylation of the Alpha s subunit. GTP can’t be converted back to GDP, so it permanently binds to the Alpha s subunit permanently activating cAMP and causing the Cl- Channels on the apical membrane to remain open. Na+, Cl-, H2O are unrestrictely secreted into the lumen.
Tx: Oral rehydration solution
Avian GI Physiology
What are the parts of the avian GI?
How long does an adult chicken’s GI tract can be?
In general, the intestines of birds are relatively shorter than those of mammals.
- Beak and oropharynx
- Pre-crop esophagus
- Crop
- Post-crop esophagus
- Preventricular (gandular stomach)
- Gizzard (muscular stomach)
- Duodenal loop
- Small Intestine (jejunum and Ileum)
- Ceca
- Large intestine (very short)
- Cloaca
- Vent
Adult Avian GI 200 cm
What are the choanal clefts and what does each communicate with?
2Where is the crop relative to the esophagus?
3Which one of the two avian stomach chambers is the glandular stomach and which one is the muscular stomach?
4Are there lacteals in the lamina propria of the avian small intestine?
5What structure marks the end of the small intestine ileum?
6What are the two parts of the large intestine?
7What appears to be the function of the well‐developed villi near the ileocecal junction?
8What are the three compartments of the cloaca? Which one is most cranial and which one is most caudal?
9Are gallbladders present in domestic birds?
1.
What is the name of the combined cavity of mouth and pharynx extending from beak to esophagus?
How does it function?
Oropharaynx
The roof of the cavity is the PALATE, has long median cleft (choana) that connects with NASAL CAVITY.
Shorter cleft (infundibular cleft) is opening of the auditory tubes.
The floor of the oropharynx is formed by the mandible, tongue, and laryngeal mound. The glottis is a median slit, and there is no epiglottis guarding it.
Chickens may have as many as 300 taste buds.
Salivary glands are present and are well developed but the secretion contains little amylase. Saliva provides lubrication for the boli.
Esophagus and Crop
It consist of cervical and thoracic regions
Near the thoracic inlet of the cervical esophagus there is a dilatation that forms a pouch known as the crop (ingluvies), which has a food storage function. In the thoracic region the postcrop esophagus terminates in the proventriculus. Mucous glands are abundant in the esophagus to provide lubrication for food being swallowed.
The Stomach
What are the two chambers of the stomach?
What is the second chamber also known as?
What is the Koilin?
Why is there a red-deep color?
What is the cuticle?
How does grit help digestion?
The proventriculus is the first of two chambers that comprise the avian stomach. It is the glandular or gastric stomach.
The second chamber is the ventriculus, also known as the gizzard the muscular stomach or grinding stomach
The deep red color is due to a high concentration of myoglobin. The mucosal surface of the ventriculus is lined with a thick cuticle, called koilin, a car-bohydrate–protein complex. Koilin is formed when the mucosal secretion solidifies on the surface following exposure to the low pH in the ventriculus. The cuticle protects the ventriculus from acid and proteolytic enzymes secreted by the proventriculus.
Grit is not essential for digestion, but it helps the food moves faster instead of staying in the gizzard longer.
Small intestine
What are the parts of the SI?
It continuos caudally from the ventriculus by the duodenum.
There is a duodenum loop as found in mammals.
Meckel’s diverticulum is the Yolk sac vestige about midway in the small intestine and it is used to indicate the division between the JEJUNUM ans ILEUM.
A well‐defined network of blood capillaries, connective tissue, smooth muscle, and nerve fibers are present in the lamina propria, but no there are lacteals (blind beginnings of lymph capillaries). The ileum ends with a circular ring of muscle tissue projecting into the rectal lumen that appears to serve as a valve at the ileocecocolic junction (see Figure 46.1). Entrances to the ceca are located immediately caudal to this ring.
Avian ceca and large intestine
Where does bacterial breakdown occur?
Where does the absorption og water occur?
Is there villi in the LI?
NO paired ceca present in hawks or sonbirds
The large intestine comprises the ceca and the rectum (colon).
In most birds, a right and left ceca arise at the junction of the small and large intestines and pursue retrograde courses beside the ileum to which they are attached by ileocecal folds.
In chickens, a cecum can be divided into three regions depending on development of their villi and the presence or absence of longitudinal and/or transverse folds. Near the ileocecal junction, villi are well developed and inter-digitate to form a filter that excludes coarse intestinal contents and allows fluids to enter. While early opinions considered their function to be mainly for absorption, a greater understanding and importance of the ceca is presently recognized. In this regard, cecectomy results in reduced metabolism of food, lower digestibility of crude fiber, and greater loss of amino acids. Also, bacterial breakdown of cellulose occurs in the ceca.
Rectum and cloaca
What is the vent, and bursa of fabricus?
The rectum (colon) is relatively short and links the ileum with the coprodeal compartment of the cloaca
The coprodeum is the most cranial of the three cloacal compart-ments followed in order by the urodeum and proctodeum
The urodeum and protodeum open externally through the anus
ANUS is the VENT
The BURSA OF FABRICUS is involved in immune function and it is protected dorsally from protodeum
Gastroduodenal motility
What type of contractions are present and with what frequency?
What is the sequnce in contraction?
Rhytmic contractions and they occur ~3/minute
Contraction of thin entricular muscles
2-3 peristaltic waves through duodenum
Contraction of thick ventricular muscles
Peristaltic wave through ventriculus
About 4x/hr digesta from duodenum and upper jejunum refluxes into ventriculus. This activity permits the remixing of intestinal content with gastric secretions
Extrinsic innervation does not appear to be involved in the initiation of contractions or to be significant in the regulation of the sequence.
This activity permits the remixing of intestinal content with gastric secretions
Ileal, colonic, and cecal motility
What are Antiperistalsis movements and what is their purpose?
Antiperistalsis are segmenting contractions that occur almost continuously in the colon.
Functions of the antiperistaltic contractions are (i) to move urine from the cloaca into the colon and ceca for water reabsorption and (ii) filling of the ceca.
Antiperistaltic contractions arise from the cloaca and occur at a rate of 10–14 per minute in chickens and turkeys.
Antiperistalsis ceases immediately before defecation, and the entire colon contracts to evacuate the feces.
There are major and minor contractions that occur in the ceca. The major contractions are associated with peristaltic con-tractions in the colon, whereby a series of major contractions is associated with cecal evacuation, and a single major contraction is associated with defecation. The minor contractions perform a mixing function.
Poultry Feces
What is the difference between cecal and intestinal droppings?
Cecal droppings have a chocolate brown color, homoge-neous texture, and are distinguished from intestinal droppings, which that have a greenish, granular‐textured appearance. One or two cecal droppings occur per day, while 25–50 intestinal droppings are formed.
The Liver
Where do the ducts drain into?
How many lobes does it have?
The liver is Bi-lobed. It has right and left lobes.
The duct from the right lobe is the only one connected to the gallbladder. Bile ducts drain into the distal duodenum near the location of the pancreatic ducts.
The pancreas is located within the duodenal loop. There are three pancreatic ducts that drain in the distal duedenum.
Gallbladders are present in chickens, turkeys, ducks, and geese and bile is transported to the duodenum by two ducts (one from each liver lobe).
What is food prehension?
Food is grasped by the beak and brought into the mouth by repeated upward and downward movements of the head. Following prehension, swallowing is accomplished in three phases, oral, pharyngeal, and esophageal
Digestive issues for poultry
Based on digestive anatomy
Highly digestible starch and protein are most efficient for commercial poultry
High fiber diets will not be digested well
However, free-ranging chickens will consume some fiber
Impacted crop (crop binding, pendulous crop)
Sour crop
Ruminant Digestive Physiology
The forestomachs of the ruminant are?
The gastric stomach of the rumen is?
What is the function of the rumen and reticulum and to a lesser extent the omasum?
What is the Reticulum?
The forestomachs are, the reticulum, rumen, omesum.
The gastric stmach is the abomasum
The rumen is the largest compartment (left side of the cow abdomen)
It is part of a fermentation chamber where papillae increases surface area for absorption.
Butyrate and volatile fatty acids (VFA) are produced in the rumen.
The reticulum in the fermantation vat. It has a unique honeycomb-sheped projections from its wall.
What is the overall capacity of the ruminant GIT?
60-80 gallons
The rumen 42.5 gallons
Reticulum 2 gal
Omasum 4 gal
Abomasum 4 gal
Small intestine 15 gal
Large Intestine 10 gal
Pseudoruminants have no omasum
Where is the esthetoscope place to listen to rumen contractions?
How often do they normally occur?
Paralumbar fossa
1-2 minutes
