Download Mucosa

Kharkov National
Medical University
LECTURE for dentistry students
Department of
Histology, cytology and
embryology
DIGESTIVE SYSTEM


The digestive tract is a long tube and associated glands.
Main functions are: ingestion, fragmentation,
digestion, absorption of nutrients and elimination of
waste products.
Embryogenesis
Gut – from endoderm,
stomatodaeum, proctodaeum – from ectoderm
Connective tissue, muscles are from mesoderm
amnion
yolk sac
General plan of structure

FOUR membranes:

Mucosa:



Epithelium
Lamina propria
Muscularis mucosae
Submucosa
Muscularis externa
Serosa or adventitia
3a
1a
2a
1b
1c
2
2b
4
3b
Mucosa: 1.epithelium
Mucosa:
2. lamina propria – c.t. –
nutrition,
support,
3. muscularis mucosae



Submucosa - c.t.
- big bl.vessels, glands,
nerve plexuses, lymphatic nodules,
 provides motility of mucosa
Muscularis externa – circular, longitudinal
layers
Serosa or adventitia
Esophagus
6-7 longitudinal folds.
Epithelium is stratified squamous nonkeratinized
The muscularis externa is composed of skeletal and smooth
muscle.
Esophagus
1) Mucosa2) Submucosa,
3) Muscularis
externa
4) Adventitia
Esophagus
ss
mg
lp
mm
sm
me
 Mucosal cardiac glands (mg) are found in the lamina propria
(lp) (mm) in the upper and lower thirds of the esophagus. If
they are not fully effective, the excessive reflux results in
pyrosis (heartburn) – tending to rise of the gastric contents
upward toward the neck.
Esophagus
mm
mg
s
me
A mucous esophagel glands proper (mg)
lie in the submucosa (s).
Esophagus,
m
 middle 1/3rd med. mag.
.
L
sub
sm
me
sk
The muscularis externa (me).
smooth (sm) & skeletal muscle (sk).
Accumulations of lymphocytes (L), called lymphatic nodules are common in the
mucosa (m) along the GI tract.
Esophagus
submucosal gl.
med
lymphatic nodule
M'
high
lumen
muscul.
externa.

str.sq.epi
musc. muc.
submuc.
A'
high
nerve supply
The gut nervous system is extensive. In the submucosa
(Meissner’s plexus) (M') and in the muscularis externa
(Auerbach’s plexus) (A').
E
sc
1
S
2
low
sc
3
E
med
S
high
Esophagus/Stomach junction. - low, med. & high mag.
Epithelium is changed from stratified squamous to
simple columnar (sc).

Stomach

The process of digestion essentially begins in the stomach;
little absorption and excretion.

The mucosal lining is a simple columnar secretory epithelium
(mucous).

Folds (rugae), gastric pits, mammilated areas.

Glands vary in different regions of the stomach.
gp
sc
Gastric pits (gp) are invaginations of a simple columnar
epithelium
The mucus layer protects the stomach.

Lamina propria contains glands:

fundic glands secrete enzymes and acid of
the stomach.

While cardiac
and pyloric
predominantly secrete mucus.

The fundic glands are simple tubular.

They contain 4 cell types:
glands
1. Chief cells

form the body of the glands.

produce pepsinogen and lipase.
2. Parietal cells
secrete hydrochloric acid ( HCL ) and
intrinsic factor is necessary for absorption
of vitamin B12
3. Enteroendocrine cells (APUD)

20 different types
4 principal hormones

4. mucous neck cells - stem

Fundic
stomach
mucosa
gastric
pit
Isthmus

In fundic stomach,
gastric pits occupy
1/4 the mucosa;
fundic glands
comprise the
remaining 3/4ths.
fundic
gland
Neck
Base
sc

Cardiac Stomach,
gastric
pit
Gastric pits occupy ½ of
mucosa.
cardiac
glands
Gastric glands are simple tubular
and slightly branched
Cells are mucus-secreting and
occational endocrine
mm
Stomach, pyloric
gastric
pit
gastric
gland
mn
low
In the pylorus, gastric pits occupy 3/4ths,
pyloric glands – short and branched.
The major cell of the gland is the pale mucous
(mn); parietal cells are absent - pyloric
stomach nears the intestine.
smooth muscle
outer
inner
m
middle
artery
fundic
glands
submucosa
muscularis
externa
musc.
mucosa
s
vein
Fundic Stomach, nerve supply, - med & high mag
Elements of the submucosal (s) and myenteric (m) nerve
plexuses are present.

Small intestine



Functions:
digestion – liver, pancreas, enterocytes
absorption - enterocytes
Intestinal lining:
plicae circularis: mucosa + submucosa
intestinal villi:
epithelium, lamina propria, mm
crypts:
invaginations of epithelium in the
lamina propria
Duodenum
Ileum
lacteal
Villus
serosa
a
Epithelium
(villus)
bb
gc
L

1. Enterocytes = Columnar absorptive cells (a) have microvilli = brush
border (bb) for absorption of digested food.
2. Mucus-secreting goblet cells (gc) produce a protective mucus. Lymphocytes
and plasma cells (L) are numerous in the lamina propria of the villus.
Epithelium
(crypt)
p
g
a
At the bottom of intestinal glands (crypts) are
3. the granule-containing Paneth cells (p). Lysozyme.
Goblet (g) and absorptive (a) cells.
3. Paneth cells, 4. enteroendocrine cells (CCK,
secretin, GIP),
5. undifferentiated cells
4
5
3
Villus,
lacteal
ivs
v
ivs
lp
sm
l
c
gc
GALT
low
The lamina propria (lp) contains blood-filled capillaries ©,
and lacteal (l),
smooth muscle cells (sm),(krok – villus shortens
GALT
Duodenum
v
low
m
v
sm
v
me sm
s

bg
mm
ig
lp
m
med
Lamina propria, mm
Submucosa filled with Brunner’s mucous glands (bg), around which - 2 layers
of smooth muscle
the muscularis externa (me) surrounded by
the serosa (s).
Jejunum
v
a
ig
g
ig
P
med
 low & med. mag.
The jejunum is like the duodenum
but has no submucosal glands and Peyer’s patches.
Contains bigger amount of goblet cells
low
Ileum
v
cr.
muscul.
mucosa
v
sm
sm
low

lnmed
ln
low & med. mag.
The major distinguishing feature is the aggregated lymphatic
nodules (ln) called Peyer’s patches in the mucosa or
submucosa
Large intestine




Reabsorbtion of water & electrolytes
Elimination of wastes
Inner lining - permanent internal folds of its mucosa &
submucosa called plicae circulares and crypts.
muscularis externa. The inner circular layer is
uniform but the outer longitudinal layer has 3 thicker
bands, the taenia coli.
Taenia coli
Colon
cr
pc
med
muscularis
mucosa
submucosa
low
musc. ext.
Plicae circulares (pc) . Unlike the small intestine there are no
villi.
There are straight intestinal glands – crypts (cr) composed mainly
of 1. goblet cells – the most numerous .
2. Columnar absorptive cells
3. Enteroendocrine cells
4. Undifferentiated cells

Large intestine
COMPARE !

Appendix
Liver & Gall Bladder
Liver has specific location – on
the way of absorbed
material, that is why has
very original vasculature and
functions
Functions:









Bile synthesis and secretion (emulsification)
Excretion of bilirubin
Protein synthesis
Gluconeogenesis
Storage
Detoxification
Protective
Hemopoietic organ
Endocrine
Liver has lobulated structure
Liver lobule
① at its center - central
vein
② hepatic plates（cords of
cells - hepatocytes）locate
radially
③ hepatic sinusoids locate
between plates
is hexagonal in shape

Hepatic plate(cord)is
one or two cells thick

Between cells the bile
canaliculi locate
Bile canaliculus
hepatocyte
sinusoid
Kupffer cell
The bile canaliculus wall is made
up of hepatocytes
Blood circulation of the liver



Hepatic artery
interlobular artery
Portal vein
interlobular vein
hepatic sinusoid
s
central vein
d

cv

v

cv
sublobular vein
hepatic vein
a

The way of bile draining
At the lobule coners the portal triads are
found:
Pancreas.

Mixed gland
Functions:
–Exocrine




Trypsinogen, pepsinogen, peptidase
Amylase
Lipase
Deoxyribonuclease, ribonuclease
–Endocrine
Pancreas –
compound acinar
serous gland







Exocrine – 98-99%
Endocrine – 1-2%
Capsule
Septa
Lobules
Interlobular duct
Serous secretory units
low
lobule
lobule
id
med

Exocrine part
Structural features of the acinus:
① Purely serous.
② the presence of centroacinar
cells in the center of the acinus
Intercalated duct
Serous cells
Centroacinar cells
Pancreas. Endocrine

Islets of Langerhans, low & med. mag.
low, H&E
Scattered among exocrine
secretory units spherical
collections of light-staining
cords of endocrine cells
.
med,
trichrome
Pancreas. Endocrine





islets of
Langerhans:
1. B cell
2. A cell
3. D cell
4. minor
cells:
PP, D1, EC,
Islets of Langerhans






B - insulin
blood glucose
70%
A – glucagon
blood glucose
15-20%
D – somatostatin
insulin
5-10%
glucagon
PP – PP,
D1 – VIP,
EC – secretin, motilin