Digestive System Flashcards
Describe the lining epithelium.
- Stratified squamous = lips to non-glandular stomach (+ anus)
-oral cavity
-tongue
-esophagus - Simple columnar = glandular stomach & intestine
-mucosa
-rectum
Describe the oral cavity.
-lips, cheeks, palate, pharynx, tongue
-stratified squamous (K or non-K)
-submucosa of CT
-salivary glands & tonsils
EX. Dental pads in ruminants
Describe the tongue.
-mucosa
-stratified squamous (K dorsally)
-papillae = mechanical & gustatory (some taste buds) cats
-skeletal muscle (longitudinal, transverse, vertical)
Taste bud (picture).
Describe dentition.
-type of food consumed
-prehension
-mastication (chewing)
influence shape & structure
Describe the tooth.
HARD:
-enamel = covers external surface above gum line [ameloblasts]
-cementum = covers external surface below gum line [cementoblasts]
-dentin = beneath enamel & cementum [odonoblasts]
SOFT:
-pulp = loose CT & nerves
-periodontal ligament = fibroblasts
Describe enamel & dentin formation during tooth development.
-odontoblasts cover surface of mesenchymal papilla & produce dentin
-ameloblasts = produce enamel
>tall & columnar
Describe brachydont.
-short & stop growing after eruption
-crown (above gingiva)
-neck (below gingiva)
-1 or more roots in a bony socket (alveolus)
-all teeth of carnivores (humans), incisors of ruminants, teeth of pigs except incisors
Describe hypsodont.
-tall & continue to grow after eruption
-no crown/neck
-horses, cheek teeth of ruminant, canine teeth of pigs, rodents (ex. Bunny)
Describe the general organization of tubular digestive organs.
- Mucosa
- Submucosa
- Muscularis
- Serosa/Adventitia
Describe the mucosa of tubular digestive organs.
- Epithelial lining
-simple columnar & glandular - Lamina propria
-loose CT
-blood vessels, lymphatics, lymphocytes, smooth muscle
-supports epithelium - Muscularis mucosae
-smooth muscle
Describe the submucosa of the tubular digestive organs.
-loose CT
-motility of mucosa
-vessels, nerve plexus (submucosal)
-(+/-) lymphatics, glands
Describe the muscularis of the tubular digestive organs.
-smooth or skeletal
-2 layers of smooth = inner circular & outer longitudinal
-controls lumen size, motility of tube
-myenteric nerve plexus, vessels
Describe the serosa/adventitia of the tubular digestive organs.
Serosa:
-mesothelium + loose CT
-(+/-) adipose tissue
-continuous with mesentary omentum & peritoneum
Adventitia:
-loose/dense CT
Describe the enteric NS.
Division of ANS
1. Submucosal plexus = meissners plexus
2. Myenteric plexus = Auerbachs plexus
each region = nerves connecting ganglia
Describe the esophagus.
-stratified squamous (K or non K)
-submucosa = mucous glands
-muscularis = skeletal (dogs, ruminants) or both (cats, horses, pigs)
-adventitia
Describe the stomach.
-digestive tube with sphincters at entry (cardia) & exit (pylorus)
-mucosa
>non glandular = stratified squamous
>glandular = simple columnar
Describe the stomach (species-specific).
- Simple
-carnivores & human
-glandular mucosa - Compound multichambered
-ruminants
-stratified squamous in forestomach (rumen, reticulum, omasum)
-glandular in abomasum (true stomach) - Composite
-pig & horse
-glandular & stratified squamous
Describe the composite stomach of a horse.
Margo plicatus (mp) =
-junction between glandular (g) columnar & non glandular (ng) stratified squamous stomach
Describe the compartments of ruminant forestomaches.
all lined by keratinized stratified squamous
1. Rumen = largest, low papillae, increased SA
2. Reticulum = honeycomb mucosa (smooth muscle)
3. Omasum = leaves ‘butchers bible’
-Rumen & reticulum = mixing, eructation, regurgitation, movement of ingesta, absorption of VFAs (volatile fatty acids)
-Omasum = squeezes ingesta & liquifies & moves to abomasum (true stomach) for more digestion
Rumen (picture).
P = papilla
LP-s = lamina propria
M = muscularis
Reticulum (picture).
Omasum (picture).
La = interpapillar space, arrows pointing to lining mucosa
L-m = lamina propria
M = muscularis
Describe the glandular stomach.
abomasum in ruminants
3 regions in all species:
1. Cardia
2. Fundus/body
3. Pylorus
simple columnar in all regions
-gastric pits = invaginations of epithelium lead to glands
-rugae (folds) = distention
-muscularis = smooth muscle (oblique, circular, longitudinal)
-serosa
What are the glandular regions of the stomach?
all regions covered by mucous
1. Cardiac
-mucous glands
2. Fundic
-gastric glands
>parietal cells = secrete HCl
>chief cells = produce pepsinogen
>endocrine G cells produce GI hormone ‘gastrin’ (enters blood)
3. Pyloric
-mucous glands
-endocrine G cells
Cardiac region (picture).
P = gastric pit
G = glands
Lp = lamina propria
Lm = lamina muscularis (muscularis mucosae)
S = submucosa
Fundic region (picture).
Parietal = pink
Chief = purple
Pyloric region (picture).
G cells not visible without special stain.
P = gastric pit
LP = lamina propria
G = gland
Describe the contents of lg VS sm intestines.
Small: (finger-like projections)
-duodenum
-jejunum
-ileum
Large:
-caecum
-colon
-rectum
Describe the small intestine.
-simple columnar
-enterocytes = absorptive
-goblet cells = make mucus
-circular folds, villi, microvilli = increase SA
-submucosal glands in duodenum (submucosa) = ‘brunner’s glands’
-lymphatic nodules in ileum (submucosa) = ‘Peyers patches’
-MALT = mucosal associated lymphoid tissue
Describe the small intestine mucosa.
Villi:
-papillary projections into lumen
-absorption
Intestinal crypts:
-base of villi
-invaginations of epithelium
-site of cell production/division
Describe the intestinal epithelium.
-enterocytes = absorptive microvilli
-goblet cells = mucus
-stem cells = proliferative (migrate out of crypt as they develop)
-enteroendocrine cell = regeneration (4-5 days)
>target for parvo virus
Crypts of Lieberkuhn (picture).
Longitudinal section of villi (picture).
Lamina propria = loose CT with smooth muscle, lymphatics, blood vessels, lymphoid cells
Describe lacteals.
-lymphatic vessels in intestinal villi
-chyle = found in lacteals
>filtered through intestinal lymph before reentering blood at jug vein
Describe lymphoid tissue.
-lymphocytes & plasma cells in lamina propria
-peyers patch:
>lymphoid nodules in lamina propria & submucosa of sm intestine
>seen in jejunum & ileum
Describe M cells.
-specialized epithelial cells that sample antigens from lumen
Describe brunners glands.
-produce alkaline mucus to protect duodenum from acidic chyme
-not present in non-mammalians
Describe the large intestine.
-absorb water
-secrete mucus
-fermentation
-volatile fatty acid absorption in hind gut fermenters
-no villi
-intestinal crypts (glands)
-simple columnar
-pigs & horses = taeniae coli (long flat bands) -> smooth muscle & elastic fibers from haustra
Describe the rectum & anus.
Rectum:
-simple columnar
-store feces
-secretes mucus
Anus:
-stratified squamous
R = rectal mucosa
N = lymphoid nodule
R-a = rectoanal junction ‘mucocutaneous junction’
A = anal mucosa
What are the 3 glandular regions of the anus?
- Anal glands = empty into lumen of anus
- Anal sac glands = empty into anal sacs (carnivores)
- Circumanal glands = non patent ducts, unknown function, benign tumors dogs
Describe anal sacs.
-paired (lateral & below anus in carnivores)
-keratinized stratified squamous
-between smooth muscle of interanal sphincter & skeletal muscle of external anal sphincter
-glands:
>apocrine tubular sweat glands in dog
>sebaceous & tubular apocrine sweat glands in cat
Describe circumanal/perianal glands.
-present in subcutis around anus in dogs (+ skin near prepuce, tail, flank, groin)
-glands similar to hepatocytes = ‘hepatoid glands’
Esophagus (picture).
Tongue (picture).
Colon (picture).
Stomach (picture).
Describe saliva.
-salivary glands: Contains water,salts, mucin, enzymes(amylase,maltase, lipase), IgA, lysozyme, lactoferrin and suspended cells
(desquamated epithelial cells, leukocytes, bacteria)
-function: digestion, moisture, lubrication, local immunity,evaporative cooling
Describe salivary glands (lobulated).
- Major gland: parotid, sublingual, mandibular
- Minor gland: (intramural) lingual, palatal, labial, buccal, zygomatic (carnivores), molar (cats)
-types of secretion: serous, mucous, mixed
Parotid salivary gland (picture).
Serous
Sublingual salivary gland (picture).
Mucous
Describe the liver.
-largest visceral organ (1-4%)
-caudal to diaphragm
-blood circulation, filter, regeneration
>1/3 blood from hepatic artery
>2/3 blood from portal vein
~25% weight of liver is blood
Describe the components of the liver.
[blood flows to right & bile to left]
-hepatocytes
-vasculature
-biliary tree (bile)
-kupffer cells (macrophage)
-ito/Stellate cells (regen)
-oval/stem cells (regen)
-pit cells
-CT
Describe hepatocytes.
-polygonal, epithelial cells
-detox
-deamination (aa->urea)
-make bile (digestion)
-make blood proteins
-gluconeogenesis
-store energy (glycogen & triglycerides)
arranged in cords/plates
Vasculature (picture).
Vasculature (picture 2).
Hepatic artery (HA)
bile duct (BD)
portal vein (PV)
lymphatic vessels (LV)
limiting plate (LP—dotted line)
Describe the perisinusoidal space.
‘Space of disse’
-site of exchange of blood & hepatocyte
Describe the intrahepatic biliary tree.
-canaliculi = spaces
-canals & ductules lined by cuboidal (cholangiocytes)
-bile ductules = located in portal triads
Describe kupffer cells.
-macrophages
-located in blood sinusoids
-remove aged blood cells, pathogens, toxins
-intracellular iron pigment (hemosiderin)
Describe ito cells (stellate cells).
-vit a metabolism
-collagen production
-lg round lipid vacuoles
-space of disse
Describe oval cells (stem cells).
-pluripotent cells
-found in biliary tree
Describe pit cells.
-granular leukocytes
-found in sinusoids
Describe connective tissue.
-lobe covered by mesothelium (serosa)
-located over a CT layer (capsule)
-lobules = separated by CT septa
Describe the classic hepatic lobule. (Anatomical)
-drains blood from portal vein & hepatic artery to hepatic or central vein
Describe portal lobule.
-drains bile from hepatocytes to bile duct
Describe hepatic acinus. (Functional)
-supplies oxygenated blood to hepatocytes
Describe zone 3. (Centrilobular)
-nearest venule = susceptible to hypoxia
-detoxification enzymes = susceptible to metabolites from toxins
least oxygenated
Describe zone 1 (periportal).
-hepatocytes closest to O2 & nutrient rich arterial & portal inflow
-susceptible to direct acting toxins
Describe the gallbladder.
-accepts bile from cystic duct for storage
-mucosal ‘folds’ when gallbladder is empty
-bile ducts lined with short columnar epithelium
-gallbladder lined with tall columnar epithelium
-epithelial cells can modify bile (absorption of water & inorganic salts)
-smooth muscle
-serosa
Lumen of gallbladder (picture).
Describe the pancreas.
-dual gland = exocrine & endocrine
-exocrine = tubuloacinar secretory units - make digestive enzymes
>trypsinogen, chymotrypsinogen, lipase, amylase
-endocrine = pancreatic islets ‘islets of langerhans’ - produce hormones
>insulin, glucagon, somatostatin, pancreatic polypeptide
Pancreatic islet (picture).
Acinar cell (picture).
Describe the stroma of the pancreas.
-thin CT capsule (serosa) + trabeculae w blood vessels, lymph vessels, & nerves
-Pacinian corpuscle (cat)
Describe the parenchyma of the pancreas.
-endocrine = 5% of parenchyma
-exocrine = 95% of parenchyma
Describe the exocrine pancreas.
-serous acinar glands = zymogen granules
-eosinophilic
