Test 2: Lecture 19, 20, 21: Digestive Flashcards
3 layers of the GI tract
mucosa
submucosa
muscularis externa
3 layers of mucosa
epithelium
lamina propria
muscularis mucosae
carnivore stomachs have an extra layer in the mucosa called the
lamina subglandularis
there is no ___ in the mouth/pharynx/part of the esophagus in a rumen
muscularis mucosae
the lamina propria is ___ with lymphocytes and circulatory channels
loose connective tissue
The muscularis mucosae is made of ___ usually only ___ layers thick
smooth muscle
a few cell
what type of epithelium does the stomach, small intestine and large intestine have?
simple columnar epithelium (used for passive and active absorption)
what part of the digestive tract have stratified squamous epithelium?
lips to cardiac stomach
anal canal
(protection)
what part of the digestive tract have simple cuboidal epithelium
kidney
ducts of GI have what type of epithelium?
pseudo stratified and stratified columnar
submucosa is made of ___ tissue and contains __
dense irregular connective tissue
blood vessels
where is the submucosal plexus found?
submucosa
which layer of the GI tract is missing in the mouth?
submucosa
muscularis externa are two layers of smooth muscle with a ___ in between
nerve plexus (myenteric plexus)
layers of muscularis externa
a. Inner circular layer (smooth muscle): reduces gut diameter
b. Myenteric Plexus (enteric nervous system)
c. Outer longitudinal layer (smooth muscle): reduces gut length
Adventitia
outermost layer of GI tract
loose CT
Inside the abdominal cavity (intraperitoneal), the adventitia is draped by serous membranes (mesothelium) and is renamed “serosa”
Inside the abdominal cavity (intraperitoneal), the adventitia is draped by serous membranes (mesothelium) and is renamed ___
serosa
how is gut innervated?
autonomic innervation
parasympathetic
sympathetic
enteric
parasympathetic innervation of the GI promotes
rest and digest
passage of food through GI
Parasympathetic innervation to the upper g.i.: ___: innervation to mouth, pharynx, esophagus, stomach, duodenum, pancreas, liver, etc.
Vagus Nerve (cranial nerve X)
Parasympathetic innervation to the lower g.i.: ___: particularly important for defecation.
Pelvic Nerve
autonomic sympathetic innervation of the GI promotes ___
fight or flight
inhibits digestion: closes sphincters, inhibits enteric motor neurons
Sympathetic innervation to the g.i. arises from ___ - preganglionic fibers arise from the celiac, cranial, caudal mesenteric ganglia.
T5 - L2 (splanchnic nerves)
what is the function of the ENS
enteric nervous system
controls g.i. movements, secretions, regional blood flow, fluid flow, etc.
activity of ENS can be regulated by autonomic nervous system ( parasympathetic= rest and digest)
what are the two plexi of the ENS
enteric nervous system
I. Outer plexus: Myenteric (Auerbach’s)
II. Inner plexus: Submucosal (Meissner’s)
outer plexus of the ENS
Myenteric (Auerbach’s)
a. Lies between the inner circular and outer longitudinal layers of the muscularis externa.
b. Controls the overall muscle tone of the gut as well as its rhythmic contractions (peristalsis).
c. Peristalsis: stimulated by distension of the gut. Inner circular layer of muscularis externa forms a contractile ring - squeezing around the gut. Outer longitudinal layer then contracts – pushing bolus caudally. At the same time, the distal gut relaxes, allowing food to enter.
d. Anti-peristalsis: regurgitation & vomiting.
myenteric plexus of ENS
what is 4
myenteric plexus of the ENS
Myenteric (Auerbach’s) controls ___ of the GI tract which ___
Peristalsis:
movement of food through the GI tract
Submucosal plexus of the ENS lies within the ___
submucosal layer
The inner plexus of the ENS oversees the ___
localized secretions and absorptions of the epithelium in the lumen, regulation of blood flow, etc.
___ is responsible for localized contractions of the ___and the villi of the gut.
inner plexus, submucosal plexus, meissner’s
muscularis mucosae
name for plexus of ENS within the 2nd layer of the GI
Inner plexus: Submucosal (Meissner’s)
the mouth is where food is chewed into a___, partially digested, and lubricated by ___.
bolus
salivary glands
The oral cavity is lined by ___ epithelium which can have a range of keratinization based on diet.
stratified squamous epithelium
what is an easy way to determine oral vs aboral surface
aboral will have hair follicles and more keratinization (usually)
The tongue contains what type of glands
mucous and serous salivary glands
The core of the tongue is ___
Core of intrinsic skeletal muscle, arranged in three layers, all positioned at right angles to each other (x, y, and z planes).
Where are lingual papillae found
dorsal region of the tongue
what is the function of lingual papillae?
aid in retaining food and water, protection, and grooming.
___ have a dermal core covered by stratified squamous epithelium (keratinized).
lingual papillae
3 types of lingual papillae that lack taste buds
filiform
conical
lenticular
Lingual Papillae lacking taste buds are used for ___
food/water acquisition, grooming, protection
Filiform lingual papillae are the ___ abundant type of papillae and are found on the ___ of the tongue
most
rostal ⅔ of the dorsal tongue
Filiform lingual papillae resemble small cones, apex points ___ and is highly ___ in cats
caudally
keratinized
Conical lingual papillae are found on the ___ of the tongue and are a subtype of ___
caudal ⅓
filiform
___ type of lingual papillae are less abundant due to their large size
conical
___ type of lingual papillae are only found in the oral cavity of a ruminant
lenticular
filliform papillae
filliform papillae of a cat
3 types of lingual papillae with taste buds
fungiform (mushroom)
circumvallate (dome)
foliate (rectangular blocks)
Fungiform lingual papillae are found where on the tongue?
lateral surface
mushroom shape (contain taste buds)
Curcumvallate lingual papillae are the ___ and form a __ shape that points __ on caudal ⅓ tongue
largest
“V” shape (apex pointing caudally) on caudal 1/3 tongue
___ papillae are surrounded by a large circular trench
circumvallate (dome) (has taste buds)
___ lingual papillae are common in rabbits and monkeys
foliate (rectangular blocks) (have taste buds)
filiform/ conical papillae
fungiform papillae
(mushroom shape) (have taste buds)
Fungiform (mushroom): occupy lateral surfaces of tongue (have taste buds)
Circumvallate (dome): largest. Form a “V” shape (apex pointing caudally) on caudal 1/3 tongue. Each papillae surrounded by a large circular trench.
have tastebuds
foliate papillae rabbit (have tastebuds)
Taste Buds are ___ found on the sides of the lingual papillae and in other regions of mouth aside from the tongue.
specialized pores
taste buds consist of 50 - 150 cells, apical ends open into a ___
taste pore.
Each mature cell projects microvilli into the taste pore - these microvilli are in contact with the oral cavity and house ___ for chemical tastes
receptors
5 tastes
sweet, sour, salt, bitter, and umami (monosodium glutamate)
taste buds have 3 cell types
Taste Receptor Cells (“Gustatory”)
Immature / Supporting Cells
Basal Cells
In the cranial 2/3 of the tongue, the ___ (Cranial Nerve #7) is responsible for taste; while the sensations of touch, temperature, and pain are carried by the ___(Cranial Nerve #5).
facial nerve
trigeminal nerve
In the caudal 2/3 of the tongue, the ___ (Cranial Nerve #9), is responsible for both taste (primarily sweet and bitter) and overall sensation.
glossopharyngeal nerve
Tastebud
Salivary gland are compound ___ glands
exocrine
acinus (berry shape)
serous glands (___) that produces ___
Serous glands (parotid / exocrine pancreas)
thin watery serous fluid containing numerous enzymatic & antimicrobial properties.
Secretory cells in serous glands store their secretions in ___
secretory granules
also called zymogen
(inactive precursors to digestive enzymes).
mucous glands produce ___
Produce mucin, a thick viscous fluid composed of glycoprotein.
Salivary mucin is similar to intestinal mucin, additionally has antibacterial properties in forming a protective film over the teeth.
The precursor of mucin is ___ and is stored in the ___ cells of the mucous glands
mucinogen
secretory
what are some functions of the salivary gland
lubrication of mouth and food
antimicrobial (serous glands mostly)
digestive component
buffering agent
tooth protection
what are some antimicrobials produced by the serous gland
Lysozyme (antibacterial agent)
Lactoferrin (antifungal, antiviral, and an antioxidant: binds up free iron)
Salivary IgA (neutralizes bacteria & yeast)
Histitin (inhibits fungal growth of Candida albicans)
How does salivary gland contribute to digestion
Amylase (ptyalin): begins digestion of starches.
Lingual lipase: begins hydrolysis of fats.
How does salivary gland act as a buffering agent?
neutralizing acids & keeping pH neutral in oral cavity.
How does salivary gland act as a tooth protection
mucins and salivary proteins form a protective film on teeth: pellicles. Protects teeth from corrosive acids and bacteria
The serous demilune (half moon) morphology is not real-it’s an artifact caused by ___, driving mucinous cells to swell, pushing ___ cells to the outside.
formalin
serous
___ cells are epithelial in origin, but have ___ properties usually associated w/ mesenchymal cells (eg, smooth muscle actin).
myoepthithelial cells
contractile
___ aid in expulsion of acinar contents
myoepithelial cells
esophagus has two sphincters
Upper esophageal sphincter (proximal) : lies at the entranceway to the pharynx (cricopharyngeus muscle).
Lower esophageal sphincter (distal): relaxes to allow food to pass into stomach; constricts to prevent gastric reflux.
what muscle lies at the entranceway to the pharynx
cricopharyngeus muscle
upper esophageal sphincter (proximal)
__ is a disorder when esophageal sphincter does not fully close
GERD
GERD (Gastro- Esophageal Reflux Disease)
___ are disorders when the esophageal sphincter does not open fully
Achalasia & megaesophagus
the mucosa layer of the esophagus is ___ epithelium
stratified squamous
Mucosa & submucosa organized into longitudinal folds in a ___esophagus. These folds disappear as ___passes through.
non-distended
food
the esophagus has two types of glands: ___ and ___. They produce ___ and help lubricate epithelial surfaces
mucosal glands (in lamina propria) and submucosal glands
mucus
muscularis externa in the esophagus is ___ between species
differnt
typically the composition of the muscularis externa of the esophagus is
Upper 1/3: both layers are striated
Middle 1/3: mix of striated and smooth
Lower 1/3: all smooth
how are ruminants and dog esophagus different?
the muscularis externa is striated throughout instead of the
typically it is:
Upper 1/3: both layers are striated
Middle 1/3: mix of striated and smooth
Lower 1/3: all smooth
what nerve innervates the esophageal musculature
vagus nerve (cranial nerve #10)
a ___ surrounds the esophagus only below the diaphragm
serosa
avian tongue
- cartilage core
crop of avian upper GI
- diverticula of the esophagus
- subcutaneous
- lies in the thoracic inlet
- avian equivalent of “cheeks” (for food storage)
- Epithelial cells produce a “crop milk” in pigeons for feeding young
Epithelial cells of the ___ produce a “crop milk” in pigeons for feeding young
crop
avian esophagus
avian crop (no glands)
salivary glands are compound ___ glands that have mucous cells that secrete ___ and serous cells that secrete __
tubuloacinar
mucin
thin fluid rich in amylase
esophagus
glandular regions of the stomach
cardiac
fundic
pyloric
monogastric stomach
columnar epithelium
glandular stomach (has glands)
The fore stomach of the rumen is ___ epithelium.
the last chamber of the ruminant stomach is ___ epithelium and has ___
non glandular, stratified squamous
columnar epithelium
glands
horses and ruminants have large ___ regions of the stomach
nonglandular
Ruminant stomach serves to breakdown cellulose through actions of microbiota, primarily bacteria, but also ___, yeast, and fungi.
protozoa
what are the four chambers of a rumen stomach
the rumen, the reticulum, the omasum and the abomasum.
the ___,___ and ___ have non glandular squamous epithelium, compared to the ___ which has glandular columnar epithelium
the rumen, the reticulum, the omasum
abomasum
order of food through cow stomach
the rumen, the reticulum, the omasum and the abomasum.
the function of the first 3 chambers of the cow stomach are __
The function of the last chamber of the cow stomach is ___
physical mechanical breakdown of food
chemical/ glandular breakdown of food
This is where saliva and ingesta mix to form cud, which is regurgitated, chewed, swallowed, etc. Here microbes break down cellulose.
Rumen and Reticulum
___ is where microbes break down cellulose in ruminant
rumen and reticulum