Dentin

Dentin cont.
Odontoblast is
elongate
well developed rER
large Golgi
Apical surface in contact with the forming dentin
Apical junctional complexes between odontoblasts separate the dentin from the pulp

Odontoblasts have branched apical processes that penetrates perpendicularly through the dentin
Called odontoblast processes
Processes become longer as the odontoblast is displaced centrally during dentin deposition
Dentin cont.

Dentin cont.
Processes contained in canals called DENTINAL TUBULES
Odontoblast processes are 3-4 um dia near cell body; thinner near enamel or cementum

Fundic Glands: Parietal Cells
Called OXYNTIC CELLS
Secrete HCl
and intrinsic factor
Most numerous in upper and middle region of the gland
Large cells
Appear round to triangular
with apex directed toward lumen of gland
PC

Fundic Glands: Parietal Cell cont.
Nucleus is spherical
Cytoplasm intensely eosinophilic
easily recognized by size and staining
Numerous mitochondria (eosinophilia)
Provide energy for ion trafficking

Small Intestine: Paneth Cell
Found in bases of intestinal glands
May be seen in colon as well
Large apical secretory granules
very eosinophilic
refractile
Granules permit identification of these cells

Small Intestine: Paneth Cell cont.
Granules contain
LYSOZYME
LYSOZYME digests cell walls of certain bacteria
α-DEFENSINS
Paneth cells probably
Regulate normal bacterial flora of small intestine

Small Intestine: Submucosa
Consists of
dense connective tissue
aggregates of adipose cells
Conspicuous feature of duodenum is
submucosal glands (BRUNNER’S GLANDS)

Small Intestine: Submucosa cont.
Cells of Brunner’s glands have characteristics of both mucous and serous secretions
pH of secretions is 8.1-9.3
protects proximal small intestine
neutralizes acid from stomach
creates optimal pH for enzymes

Features of Small Intestine Mucosa: Lamina Propria cont.
Lamina propria also contains
lymphatic nodules
important part of GALT
Nodules are especially large in ileum
called PEYER’S PATCHES
Muscularis mucosae
2 thin layers of smooth muscle
inner circular
outer longitudinal

Composed of :
Cecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
Contain 4 histologic layers of GI tract; exceptions are
Mucosa is smooth (no villi)
Outer muscle layer
has 3 equally spaced bands(teania coli)
Large Intestine

Rectum is dilated distal portion of GIT
Upper part is distinguished
TRANSVERSE RECTAL FOLDS
Mucosa similar to distal colon
Anal canal is most distal part of the GIT
Upper part of anal canal has
longitudinal folds
Called ANAL COLUMNS
Depressions between anal columns called ANAL SINUSES
Large Intestine: Rectum & Anal Canal