includes the alimentary canal, plus teeth, tongue, salivary glands, liver, pancreas, and gallbladder
Oral cavity
mastication and break down of food before entering the alimentary canal
vestibule - between the lips/cheeks and teeth
oral cavity proper
behind the teeth
top: hard and soft palate
bottom: tongue
lateral: teeth
posterior: oropharynx
Tongue
made up of 8 different muscles
for vocalization, moving food into direct path of teeth for chewing, swallowing, and taste
lingual papilla
filiform
finger like
most numerous papillae
cover the surface of tongue
most keratinization
mostly stratum corneum
pointed toward throat
think like cat grooming
extensions of epidermis
no role in taste
fungiform
role in taste
looks like mushrooms
2nd most numerous
concentrated on the tip of the tongue
lateral edge of the papilla has the concentration of the taste buds
taste buds are specialized chemoreceptors
circumvallate
role in taste
circular shape
largest papillae
found on the back of the tongue organized in an upside down V
foliate
role in taste
looks like broccoli in humans
can be more square or cylindrical in other species
found near the edges of tongue
Taste buds
cells
neuroepithelial cells
supporting/sustentacular cells
basal cells
The only ones we can specifically identify
pore
has microvilli
the microvilli care covered in chemoreceptors
tastants bind here
send action potential down to the basal cells to synapse with VII, IX, and X for taste sensations
Teeth
development
deciduous teeth
baby or milk teeth
20 teeth in this set
central incisor
lateral incisor
canine
2 molars
these repeat in each quadrant
permanent teeth
32 teeth in this set
central incisor
1 root
lateral incisor
1 root
canine
1 root
premolar
2 roots
3 molars
3-4 roots
functions
incisor comes from Latin word to cut
for tearing food
molar is from molaris dens
for grinding food
Enamel
made from ameloblasts
formed from the inside out
ameloblasts fall off when the tooth erupts
milk teeth has less enamel
more prone to cavities
most slides are ground due to high Hydroxyapatite
96-98% HA
acellular
enamel is laid down in prisms or rods
Gingiva
stratified squamous epithelium and CT that the tooth is in
epidermis and dermis layers
Dental alveolus
the socket of bone
Apical foramen
the hole at the bottom of the tooth and socket
gives way for nerve, artery, and vein to go into tooth
Root and crown
the crown is what we can see of the tooth
the root is what is below the gums
Root canal
the space that holds the n,a,v
cementum
runs with the edge of the pulp cavity
cells are cementocytes
bone like material
trapped in lacunae
anchors tooth to the bone
periodontal ligament
collagen fibers that connect bone to the cementum
Dentin
material under the enamel
70% hydroxyapatite (soft bone)
runs all the way down the root
cells are odontoblasts
found at the border between pulp cavity and the root canal
projections so to the edge of the pulp cavity
produce the dentin
on SM can see little openings to the odontoblasts between the dentin
sensitivity is a sign of exposed dentin and these holes
Salivary Glands
Major ones
Parotid
submandibular
sublingual
Minor ones
lingual
buccal
labial
molar
palatine
Parts
secretory acinus
the glandular part where the products are made
duct
moved the products to their final location
moved by contractions and movements of face
parts
intercalated duct
low cuboidal
big lumen
closest to the acinus
striated duct
simple cuboidal
basal infoldings give the striated appearance
Excretory duct
simple or stratified cuboidal
want to make sure these stay open
Products
serous
protein based
zymogen granules
very distinct
packaged proteins
mucous
mucin
mucinogen granules
clear appearance gives clear appearance to secretory acinus
mixed
mucin and protein
acinus appearance is serous demilunes
dark serous part in a half-circle and lighter part for mucous
this is an artifact of the slide preparation but not how it looks in real life
in real life there is a combination of the cells and the serous parts get pushed to the edge
Parotid
totally serous
completely surrounded by adipose tissue
Stensen’s Ducts
drains at about the 2nd molar
Submandibular
mixed
Wharton’s ducts
opens at the base of the mouth under the tongue
Sublingual
mostly mucous
Functions of Saliva
moisten oral cavity
easier speech/vocalization
moisten dry food
makes swallowing easier
provides a medium for dissolved food items
dissolve food to get tastants to neuroepithelial
buffer oral cavity
high bicarbonate ions
digestion of carbohydrates
by alpha-amylase
control bacterial growth
by lysozyme
source of calcium and phosphates ions
for teeth
immune functions
IgA
acquired pellicle
film of proteins that coat teeth
barrier between tooth and a pathogen
production of saliva
1.2 L/day
controlled by ANS
GI Tract
hallow muscular tube with 4 layers
mucosa
innermost layer
epithelium
with a little loose connective tissue called lamina propria
with a little muscle called muscularis mucosa
submucosa
2nd layer
DICT
may or may not have glands
muscularis externa
sublayers
inner circular
thickened regions called sphincters
pharyngoesophageal - pharynx and esophagus
cardiac - esophagus and stomach
pyloric - stomach and intestines
ileocecal - small and large intestines
internal anal - intestines and anus
these allow for 1 way flow
outer longitudinal
coordinated contractions of these layers moves food down the tube
these waves of contractions are called peristalsis
mix contents
propel contents
Adventitia/Serosa
outermost layer
connective tissue
name changes based on location
adventitia when the wall of the tube is attached to some other structure
only connective tissue
serosa when not attached to something else
a serous membrane of simple squamous epithelium
lubricates the tube to help with peristalsis
contractions
controlled by ANS
Myenteric Plexuses
between layers 2 and 3 is Meissner’s Plexus
between inner circular and outer longitudinal is Auerbach’s Plexus
Esophagus
~25 cm long
from the Greek meaning gullet
mucosa of stratified squamous epithelium
non keratinized
only stratified squamous epithelium until anus
diffuse lymphatics
submucosa
has glands as identifying factor
esophageal glands proper
dense in upper 1/2 of esophagus
serous glands
mostly for lubrication
slightly acidic (antimicrobial activity)
Muscularis Externa
upper 1/3 is skeletal muscle
middle 1/3 is both smooth and skeletal muscle
bottom 1/3 is smooth muscle
Esophageal cardiac glands
found at junction of esophagus and stomach
mucous glands that protect esophagus from stomach contents
Stomach
swollen part of GI tube
from Greek for gatekeeper
highly secretory organ
~2 L/day
water and electrolytes
pepsinogen (inactive form of pepsin)
converted in low pH
0.16 N HCl
pH 1-2
intrinsic factor
absorption of vitamin B12
highly folded
gastric folds (rugae)
allow for expansion
Gastric pits
holes in rugae
openings into gastric glands
cells are densely packed so hard to see pits
parts
closest to surface is the pit
middle region is the neck
bottom part is the base
Cells of mucosa
mucous neck cells
secretions protect mucosa from acidic environments
chief cells
concentrated in base
zymogen granules
pepsinogen
lipase (to lesser extent)
parietal (oxyntic) cells
found in neck or base
intracellular canaliculi
microvilli
mitochondria, rough ER, and golgi
produce HCl
in response to hormone gastrin
enteroendocrine cells
found in base
aka amine precursor uptake and decarboxylation
produce gastrin by G-cells
lamina propria and submucosa
unremarkable
LP is between glands so obscured by glands
muscularis externa
3 layers of smooth muscle
inner oblique
middle circular
outer longitudinal
contraction mixes food with digestion enzymes
between middle and outer is Auerbach’s Plexuses
Small Intestines
~6 m long
3 parts
duodenum
shortest
~25 cm
jejunum
2.5 m
ileum
3.5 m
features
villi on surface
glands below surface
aka crypts of Lieberkühn
simple columnar epithelium
microvilli
capillary network and lymphatic capillary in villi
for overall purpose of absorption
mucosa
enterocytes
transport and absorption
goblet cells
increase lubrication
protect mucosa
Paneth Cells
found in base of intestinal glands
produce lysozymes
regulate intestinal flora
Enteroendocrine cells
all appear the same
all have roles in regulating pancreas and gallbladder
I-cells
cholecystokinin
S-cells
secretin
K-cells
gastric inhibitory protein
M-cells
microfold
only in ileum
overlying Peyer’s Patches
transport of macromolecules from lumen to patches
act like antigen presenting cells
intermediate cells
absorptive and goblet like
potent - can switch
think stem cells of SI
found about middle of gland and send cells up
microvilli
non-motile
enterocytes
cores of actin
Submucosa
Brunner’s Glands
only in duodenum
ducts open directly to lumen
basic secretion protect intestinal mucosa from acidic chyme
if these are not seen, look at lamina propria
Muscularis externa
Auerbach’s Plexuses
Large Intestine
aka Colon
absorption of mainly water
also some electrolytes
enterocytes - simple columnar epithelium
goblet cells
outnumber enterocytes 4:1
key ID factor for LI
Colonic crypts
aka Crypts of Lieberkühn
very similar to stomach
lined with goblet cells and enterocytes
Recto-anal junction
where the colon meets anal canal
see the change from simple columnar epithelium with lots of goblet cells to lightly keratinized stratified squamous epithelium
Accessory Organ
Extensions to GI Tube
development
starts as a straight tube
some rotations with maturation
buds or out pockets form with turns
starts with liver, gallbladder, and ventral pancreas all budding together on right and dorsal pancreas budding on left
another rotation moves ventral pancreas to left with dorsal pancreas
these will be fused together in adults
all open to duodenum
all work like glands with ducts to duodenum
Liver
largest internal organ
largest gland
found in upper right quadrant
under surface of diaphragm
exocrine
producing bile
waste products and aids in digestion
move through bile ducts that converge to hepatic duct to leave liver
leaves liver and goes to gallbladder by cystic duct
where it is concentrated and stored
leaves gallbladder, when needed, by cystic duct to common bile duct
Endocrine
albumin
alpha and beta globulins
prothrombin
fibronectin
glucose
Cells
hepatocytes
main cells
multifunction
protein synthesis and secretions
ex. bile formation
metabolism of lipid soluble drugs and steroids
lipoprotein synthesis
carbohydrate metabolism
urea productions
and more
binucleate
20-30 um
tetraploid
said to be simple cuboidal epithelium
much larger than normal SCE
~800 to 1000 mitochondria per cell
glycogen deposits/lipid deposits
Golgi complexes and peroxisomes
highest peroxisomes of any cell
SER for inactivation of toxins
synthesis of cholesterol and lipids
squiggly membranes for increasing surface area
when meets with another cell form bile canaliculus for tight junctions
add together to canals of Herring
which add to bile ducts
which add to hepatic ducts
which add to common hepatic duct
bile
H20
cholesterol and lecithin
phospholipids
bile salts
digestive enzymes for lipids
glycolic acid and taurocholic acid
greenish color due to bile pigments
bilirubin
breakdown of porphyrin rings
if in blood, causes jaundice
electrolytes
1L/day
production controlled by enteroendocrine cells
and by secretin, CCK, and gastrin
organization
arranged in plates among connective tissue stroma
stroma is the blood vessels, lymphatics, and bile ducts
sinusoidal spaces are between plates of cells
classical hepatic lobule
a representation of a hepatic lobule
shows the central vein (branch of hepatic vein), sinusoids, portal triad (branch of hepatic artery, branch of hepatic portal vein, and branch of bile duct)
shows 3D structure as hexagonal
blood moves to the center of the lobule from the triad
bile moves to the edges of the lobule toward the triad
Portal lobule
a representation of hepatic lobule emphasizing exocrine role of liver
a more top down view showing the connections of a lobule to others
uses a triangle connecting the 3 central veins with the shared triad in the middle
Liver Acinus
a representation of hepatic lobule focusing on the delivery of blood from artery and portal vein
forms 3 zones from 1 triad to next
Zone 1
closest to the triads
first to receive the nutrients but also the toxins
makes bile first
Zone 2
the middle zone
mix of the other 2
Zone 3
furthest from the triads
first to show pathologic damage
due to ischemia
Kupffer cells
MNP
phagocytic
stain for ferritin
endothelium
space between epi and hepatocytes call space of Disse
Ito cells
found in space of Disse
vitamin A storage
believed to be fibroblast derived
Gallbladder
concentrates bile 10X
tall simple columnar epithelium
only remarkable feature
highly absorptive
Rokitansky-Aschoff Sinuses
artifact from slide prep
show highly folded
gallstones
crystalline forms of cholesterol and lipids
most common reason to have gallbladder removed
don’t really need because only concentrating bile
adjust diet to limit lipid intake
Pancreas
sits below greater curvature of stomach
accessory duct (+/-) is remenant of the 2 buds during development
exocrine and endocrine
unique because separate cell types for these functions
where liver has same cells for both
exocrine - purely serous
look just like parotid
except for serous acinus
centroacinar cell
artifact of prep process
section through nucleus of intercalated duct cell
zymogen granules
trypsinogen
proteolytic enzyme
procarboxypeptidase
proteolytic enzyme
amylase
lipases
DNAse/RNAse
helps with digestion
endocrine - Islets of Langerhans
no prominent zymogen granules
cell types
alpha (A)
15-20% of islet
glucagon
beta (B)
70% of islet
insulin
delta (D)
5-10% of islet
somatostatin
decreases activity of parietal cells (HCl production)
differentiate by Mallory-azan stain
