GI Tract Flashcards
What are the 4 tunics of the GI tract?
- Mucosa
- Submucosa
- Muscularis
- Serosa or adventitia
What are the three parts of the mucosa?
a. Epithelium
b. Lamina propria
c. Muscularis propria
difference between Meissner’s and Myenteric nerve plexus?
Meissner’s nerve plexus: contains sympathetic & parasympathetic fibers
Myenteric nerve plexus: parasympathetic terminal ganglia & autonomic fibers between muscle layers
What muscle type is found in the GI tract?
Tunica mucosa
What are the two layers of the tunica muscularis (in the typical gut section)?
- The inner circular muscle layer forms sphincters
- The Outer longitudinal muscle layer may form longitudinal bands (tenia)
whats the difference between an adventitia and serosa?
Adventitia: an ill-defined layer of connective tissue blending with surrounding connective tissue
Serosa: thin connective tissue layer covered by mesothelium
- Aka the visceral peritoneum
what are the type of epithelium found in the mouth, esophagus, tongue, stomach (different species), small intestine, large intestine, and rectum.
Mouth: stratified squamous epithelium
Esophagus: thick stratified squamous epithelium
Tongue: stratified squamous epithelium
Stomach: simple columnar epithelium
Small intestine: simple columnar epithelium
Large intestine: simple columnar epithelium
Rectum: stratified squamous non-keratinized epithelium
Philtrum
median cleft of the upper lip in carnivores and small ruminants
Palatine rugae
the anterior part of the palatal mucosa that forms ridges
Dental pad
present in ruminants, located on the rostral end of the hard palate, and replaces the upper incisors
Incisive papilla
small median swelling behind the incisor teeth. And incisive ducts to the vomeronasal glands
Sublingual caruncles
mucosal elevations on the floor of the oral cavity under the tongue and just caudal to the incisors
Lingual frenulum
the Central fold of mucous membrane connecting the floor of the oral cavity and the ventral surface of the tongue
What cranial nerve innervates the lips?
Cranial nerve V = trigeminal nerve
What cranial nerve innervates the muscles of mastication? Which branch?
The mandibular nerve is the branch of the trigeminal nerve
list the muscles of mastication
- Innervated by the mandibular nerve
- Temporalis
- Masseter
- Pterygoideus medialis
- Pterygoideus lateralis
filiform papillae (cats & cattle)
a. mechanical- functions to direct food caudally
b. found on the dorsal surface of the rostral 2/3 of the
tongue
c. apical processes are keratinized and point caudally
d. large & rough -> found for grooming
conical papillae (NOT found in horses)
a. mechanical
b. located on the root of the tongue and the inner surface
of the cheek
c. Large, with keratinized epithelium and a large
connective tissue core
lenticular papillae (ruminants)
a. mechanical
b. large & grossly visible (lentil shaped)
c. keratinized
d. found on the dorsal prominence of the tongue
fungiform papillae (humans & herbivores)
a. possibly mechanical & gustatory
b. scattered rostral dorsal surface of the tongue
c. maybe be keratinized in herbivores
circumvallate papillae (pigs, horses, carnivores, ruminants)
a. gustatory
b. “V” shaped at the rostral border of the root on the
tongue
c. Each papillae is surrounded by a depression -> moat
d. Pigs/horses (1 pair)
e. Carnivores (2-3 pairs)
f. Ruminants (many pairs)
foliate papillae (pigs, horses, carnivores, rabbits)
a. gustatory
b. leaf-like and separated by furrows
c. found in a row in the lateral margin of the tongue
difference between the parotid salivary gland secretions and the mandibular salivary gland secretions?
parotid salivary gland secretions:
produces serous secretions. Molded around the ventral part of the ear cartilage. The duct opens in the vestibule of the mouth
- dog -> ducts run over the masseter muscle - larger animals -> duct runs along the angle of the jaw
mandibular salivary gland secretions:
produces mixed mucous and serous secretions. Close to the angle of the jaw. And duct runs ventrally along the floor of the mouth and opens into the sublingual caruncle.
Is the esophagus dorsal or ventral to the trachea?
dorsal
which parts of the GI tract have submucosal glands
esohpagus & duodenum
Which species of animals have striated muscle only in the proximal portion of the esophagus?
dog
Where does the greater omentum attach to the stomach? The lesser omentum?
The greater omentum attaches to the stomach of the transverse colon. And the lesser omentum attaches the stomach and duodenum to the liver.
Cardia
opening or part of the stomach around the opening. And closest to the heart
fundus
blind; expanded portion of the stomach
body
largest part of the stomach
pylorus
the distal opening of the stomach. Surrounded by a strong band of circular muscle (pyloric sphincter)
What is the margo plicatus and which two species of animals have it?
Separates the glandular and non-glandular parts of the stomach
horses &p pigs
Cardiac glands
- found near the esophagus and are small
- Contains predominantly mucus cells.
- Pits & glands may be short.
- wide lumen
Fundic glands
- the largest region (except in pigs), with the greatest variety of cell types in glands.
- In horses and pigs, the stomach also contains a non-glandular area of the esophageal region which is lined by stratified squamous epithelium
body glands
gastric folds (rugae) is seen when the stomach is empty
Pyloric glands
- near the pylorus region
- deepest pits and the shortest coiled glands.
- Thickest tunica muscularis
What are the two main types of cells in fundic glands? What do they secrete? Which one is pink and which one is purple?
Parietal cells: secrete hydrochloric acid
- eosinophilic, round
- pink
Chief cells: Secrete proteases (trypsin & chymotrypsin)
- Basophilic, angular
- purple
What are the three layers of smooth muscle in the stomach?
- Inner oblique
- Middle circular (sphincters)
- Outer longitudinal layer
What branch of the aorta supplies the stomach?
celiac artery
What are the three main branches of the celiac artery?
- Left gastric artery
- Splenic artery
- Hepatic artery
What are the 3 divisions of the small intestine? Which is most proximal? Which is the longest section? Which section has mesentery on two sides? Which section has the longest villi? Which section has Peyer’s patches?
- Duodenum
- Most proximal
- Short & right - Jejunum
- 90% of the small intestines
- Longest section
- Longest villi - Ileum
- Empties into large intestines
- Short terminal section of the small intestines
- Peyer’s patches
- The mesentery is attached to the jejunum & ileum
what are the different cell types found in the small intestinal mucosa?
- Undifferentiated crypt cells (stem cells)
- Intestinal absorptive cells = enterocytes
- Goblet cells:
- Enteroendocrine cells
- Paneth cells
- M (microfold) cells
Undifferentiated crypt cells (stem cells)
- Located basal portion of the crypt
- Divide to give rise to other types of epithelial cells of the
intestine - replaced every few days
Intestinal absorptive cells = enterocytes
- Columnar with microvilli
- Numerous on the surface of villi in the small intestine, also
on the luminal surface of the large intestine
Goblet cells
- secrete protective mucin
- Increase in numbers distally in the intestine
Enteroendocrine cells
- Scattered throughout the epithelium
- Important in the hormonal regulation of the GU functions
Paneth cells
- Produce bactericidal substances
- Found in only the base of the gland
- Horses, ruminants, and man
- Control the microflora of the crypt
M (microfold) cells
- special epithelial cells located over lymphatic nodules
- Have blunt microvilli or ridges
- Intraepithelial lymphocytes
How is lymph pumped out of lacteals into larger lymphatic vessels?
Rhythmic contraction of the smooth muscle
What section of the small intestine has submucosal glands? What is another name for them?
- Duodenum and found in the esophagus
- “Brunner’s glands”
What are Peyer’s Patches? Are they on the mesenteric or antimesenteric side?
Peyer’s patches:
a group of well-organized lymphoid follicles that contain germinal centers.
- on the anti-mesenteric side.
Know the 3 divisions of the large intestine.
- Cecum
- Colon
- Rectum
what are the 3 divisions of the colon?
Majority length of the large intestine
- Ascending colon (right colic flexure)
- Transverse colon
- Descending colon (left colic flexure)
which species has a spiral colon
pigs
- Modified ascending colon
- Outer centripetal turns
- Toward center - Inner centripetal turns
- Away from the center - Central flexure
what is the difference between the structure of the mucosa in the small intestine and the large intestine?
Small intestine of the mucosa:
- Intestinal villi are finger-like projections of the epithelium
and lamina propria
- Circular folds
- Include villi
Large intestine of the mucosa:
- No villi
- Surface epithelium is smooth
- Longitudinal folds in some areas
- deep mucosal glands that open onto the luminal surface
- thicker
which branch of the abdominal aorta supplies the: stomach (dog), small intestine, descending colon and rectum?
Inferior mesenteric artery
Which branch of the celiac artery supplies the duodenum?
Hepatic branch of the celiac artery
What structures are supplied by the caudal mesenteric artery?
Descending colon & rectum
Of the celiac, cranial mesenteric, and caudal mesenteric arteries, know which is the most cranial and which is the most caudal.
Cranial mesenteric artery: most cranial
Caudal mesenteric artery: most caudal
What major vein drains the stomach and intestines?
Superior mesenteric vein
which side of the body the following are on (left or right): Duodenum (dog), Descending colon (dog), Cecum (dog), Cecum (pig)
Duodenum (dog): right
Descending colon (dog): left
Cecum (dog): right
Cecum (pig): left
What layer of the large intestine (be as specific as possible) forms the tenia?
Muscularis:
- Outer longitudinal layer forms bands (tenia) in the cecum
and colon of the horse and pig
- Many elastic fibers
Anal sac glands
- Found in carnivores and some rodents
- Pea to marble-sized
- Perisaccular glands secrete into the neck of the anal sac or directly into its duct
Anal glands
simple glands that secrete directly into the anal canal
list of circumanal glands (perianal glands)
- Sebaceous or non-sebaceous glands
- Suderiferous
- Hepatoid
