U3 and W3 133

What are the accessory glands of the digestive system

• pancreas

• liver

(true/false) food goes through the liver and pancreas

false, not party of the alimentary canal

purpose of both accessory glands

synthesis and release of enzymes, hormones and other secretions

why are pancreatic enzymes important?

• role in digesting 3 main nutrients

• precursors, get activate when released

What does liver produce and what’s its purpose?

produces and secretes bile, which is crucial for lipid digestion 

What other systems do the liver take part in?

metabolic, endocrine and clearance pathways

describe the pancreases

• Enzymatic and Endocrine functions 

• Pancreatic enzymes are produced by the acinar cells (purple) 

• Insulin and glucagon are produced by the pancreatic islets (pink) 

• Pancreatic ducts produce sodium bicarbonate 

  • Releases at the entrance of the duodenum, buffer that reduces the acidity 

• Pancreatitis: release of enzymes

What enzymes to Acinar cells secrete?

• trypsinogen (proteolytic)

• Chymotrypsinogen (Proteolytic)

what the difference between trypsinogen (proteolytic) and Chymotrypsinogen (Proteolytic)

• trypsinogen (proteolytic) = inactive

• Chymotrypsinogen (Proteolytic) = active

role of trypsinogen (proteolytic)

• Activated to trypsin by enterokinase 

• Proteins to peptides (peptidases from enterocytes) 

• Final product amino acids 

Role of Chymotrypsinogen (Proteolytic)

• Activated to chymotrypsin by trypsin 

• Proteins to peptides (peptidases from enterocytes) 

• Final product amino acids

role of Pancreatic amylase (Amylolytic)

•  breaks down “starch”

  • Already active 

  • Starch to Oligosaccharides Maltase and Sucrase (from enterocytes) 

  • Final product monosaccharides (glucose and fructose) 

role of Pancreatic lipase (Lipolytic)

breaks down fats

• Already active 

• Hydrolyzes triglycerides to its final products: fatty acids and glycerol

Role of ducts

• Sodium Bicarbonate 

• Secretin from SI

where does the bile duct come from?

 the liver 

what does a ruminant liver look like?

have a flatter liver with 4 lobes - location between the rumen and the diaphragm

what does a swine liver look like?

have more pronounced and total of 5 lobes

what does a horse liver look like?

do not have a gall bladder and present 4 lobes (maybe 6 depending on the text)

(true/false) horse have a gall bladder

false

what is the general structure of a liver

• The liver sits between to the diaphragm and the other viscera, and it can be identified by its dark red/ maroon/ bright brown color (when healthy)

• It’s structure can be comparable to a “pool filter”, or a “sponge” it is a solid organ, yet porous with blood vessels and bile ducts

functions of the liver

• Digestive function: production of bile (bilirubin), fat emulsification 

• Growth and development: synthesis of IGF (insulin-like growth factor 1) 

• Metabolism of drugs and toxins 

• Synthesis of proteins, cholesterol, glycogen and clotting factors 

• Storage of glycogen, vitamins and minerals 

• Fatty liver: common in “fresh” dairy cows 

• Liver abscesses: common in feedlot beef cattle

Lobe = ____

macro

Lobule = ____

micro

• needs a microscope

what is the microscopic organization of the liver

• Hepatic lobule: based on blood flow 

  • Portal lobule: based on bile flow (opposite to blood flow) 

  • Hepatic acinus: based on blood perfusion (1 = most; 3 = least)

what do hepatocytes make?

bile

list stuff about heptocytes

• Bile – stored in gallbladder (except in the horse), emulsifier. Makes droplets of fat smaller and accessible   Large Lipid Droplets (“salad dressing”) - Bile Acids,  Lipases - Small droplets 

  • Cholesterol 

  • ***Bile Salts 

    • Lipid digestion/absorption 

    • Triglycerides  

  • Phospholipids 

  • Bilirubin

Enterohepatic circulation in the duodenum

• Stimulates release of cholecystokinin 

  • Gallbladder contraction 

  • Stored bile release

Enterohepatic circulation in the ileum

• Enterocytes reabsorb bile salts mixed with food 

• Bile salts enter the blood towards the liver

Enterohepatic circulation in the liver

• Bile sats enter via hepatic portal vein 

• Taken up by hepatocytes, stored and reincorporated into the bile

What gets perfusion more saturated?

water

what does PT stand for?

Portal Tract 

• Hepatic artery + Portal vein + Bile duct

what does CVstand for?

 Central Vein

what do micelles contain?

Micelles containing

what happens to micelles?

Get absorbed by the enterocyte and become chylomicron (fats and proteins repackaged)

• Then is sent to the lacteal

how fast is the circulatory system?

very fast

how fast is the lymphatic system?

very slow 

• Where the chylomicrons are going to travel to the liver 

where are chylomicrons located?

in the lymphatic and enterocyte system 

function and size of large intestine

• Large in diameter, but for ruminants and swine it represents a smaller portion of the GIT compared to small intestine and stomach 

• Water absorption and formation of feces 

• Microbial fermentation of fiber:

  • Vital for the horse, 

  • Important for the swine

  • Little significance for the ruminants (most fermentation already happened in the rumen).  

function and size of cecum

• Blind sac stemming of the junction of the small and large intestines (ileum and great/ ascending colon)

• Size varies greatly according to species, 

  • Proportionally very enlarged in the horse and other hindgut fermenters (rabbits, hippos, elephants) 

  • Relatively small in ruminants and primary carnivores, such as cats and dogs (low fiber ingestion)  

examples of mechanical digestion

• Chewing (mastication) in the mouth

• Tongue mixing food into a bolus

• Stomach churning and muscular contractions

• Segmentation and peristalsis in the intestines

Examples of chemical digestion

• Hydrochloric acid (HCl) in the stomach denaturing proteins

• Bile emulsifying fats into smaller droplets

• Bicarbonate neutralizing acidic chyme in the small intestine

Examples of enzymatic digestion

• Amylase breaking starch into smaller carbohydrates

• Proteases (trypsin, chymotrypsin, pepsin) breaking proteins into peptides/amino acids

• Lipase breaking triglycerides into fatty acids and glycerol

What is the main site of nutrient absorption

Small intestine (especially the jejunum and ileum)

• Villi and microvilli massively increase surface area

• Absorbs carbohydrates, proteins, fats, vitamins, minerals, and most water

why is pancreatitis so serious?

• Exocrine (digestive) function

  • Releases powerful digestive enzymes (proteases, amylase, lipase)

  • If activated inside the pancreas → enzymes start digesting pancreatic tissue itself

• Endocrine (hormonal) function

  • Produces insulin and glucagon to regulate blood glucose

  ⚠ Pancreatitis can therefore cause:

  • Severe tissue damage and inflammation

  • Impaired digestion and nutrient absorption

  • Dangerous blood sugar imbalances

why is stomach mucus important

Mucus protects the stomach lining by:

• Shielding tissue from strong hydrochloric acid

• Preventing damage from digestive enzymes (like pepsin)

• Reducing friction from food movement

Without mucus → ulcers and tissue injury can occur.

characteristics of liver anatomy

• Dark reddish-brown, highly vascular organ

• Organized into microscopic lobules

• Connected to hepatic portal vein, hepatic artery, and bile ducts

roles of the liver

• Produces bile for fat digestion

• Central hub for metabolism (carbs, fats, proteins)

• Stores glycogen, vitamins, and minerals

• Detoxifies drugs and toxins

• Synthesizes important proteins (e.g., clotting factors)

species without gallbladder

horse

how could a drug that inhibits bile production contribute to weight loss?

• Bile is required to emulsify fats

• Without bile → fats are poorly digested and absorbed

• Less fat absorbed = fewer calories taken in

(true/false) you’re feeding the rumen, not the ruminant

true

define forestomach

non-glandular and lined by stratified squamous epithelium.

What are the 3 chambers of the forestomach

• Rumen

• Reticulum

• Omasum

Define abomasum (the “true stomach”)

is glandular and lines with columnar epithelium.

what chamber is the abomasum in?

last chamber

What smooth muscle in the stomach work together to contract and thereby mix feedstuffs in the rumen?

• Grooves - exterior

• Pillars - interior

define the rumen

Fermentation Vat 

• Large, hollow, muscular compartment that extends from the diaphragm to the pelvis and nearly fills the left side of the abdominal cavity

  • Can hold 30-60 gallons in adult cow 

• Walls of rumen lined with papillae

  • Non-secretory but absorptive

    • Shortchainfattyacids

  • Up to 1 cm in length and their shape and health is indicative of the diet

  • Create a niche for microbes

what is in the rumen?

• bacteria

• protozoa

• archaea

• fungi

• phages

define the reticulum

Honeycomb 

• Not completely separated from rumen 

• Acts as pacemaker of rumen muscle contractions to mix contents of rumen 

• Heavier particles settle in reticulum then passed on 

  • Becomes a huge problem if the inflammation transfer to heart and lungs 

  • Reticulperitonitis (hardware disease)

• Honeycomb-like mucous membrane surface traps non-food materials where they stay 

  • Foreign particles (e.g. wire or nails) will usually lodge here . 

• Located caudal to diaphragm

define esophageal groove

• Esophagus opens to space common to both rumen and reticulum 

• A passageway extending from the cardia (esophageal opening) to the abomasum, formed by two heavy muscular folds. 

• Functions to allow milk consumed by the suckling animal to bypass the reticulo- rumen and thus escape bacterial fermentation