Esophagus stomach презентация

Alimentary Canal
Same basic construction end to end
Four distinct layers:
Mucosa
Epithelium
lamina propria,
MUSCULARIS MUCOSAE
Submucosa
dense irregular connective tissue
Muscularis
two layers of smooth muscle
Serosa /adventitia
serosa is a mesothelium and underlying connective tissue
adventitia is found where the wall of the gut is attached to a structure
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Mucosa
Mucosa has three functions:
Barrier
separates the lumen (which is in contact with the environment) from the body interior
Secretory
Absorptive

Mucosa: Epithelium
Epithelium secretes:
Digestive enzymes
into lumen
onto apical plasma membrane
Hormones
Mucous
Antibodies
which it receives from connective tissue (diffuse lymphatic tissue)
Epithelium absorbs products of digestion
transport to vascular system
absorption occurs in small and large intestine

Mucosa: Lamina Propria
Areolar (loose) connective tissue under epithelium
Contains:
- glands
- vessels to receive absorbed substances
- fenestrated type
- numerous lymphatic capillaries; receive lipids and some proteins
- components of the immune system
Diffuse lymphatic tissue
Lymphatic nodules
Gut-associate lymphatic tissue (GALT)
and Peyer’s patches

Mucosa: Lamina propria cont.

Mucosa: Muscularis Mucosae
Layer of smooth muscles that forms boundary between mucosa and submucosa
Consists of 2 layers:
Inner circular
Outer longitudinal
Can produce movement of mucosa independent of movement of entire gut wall

Submucosa
Consists of
moderately dense irregular connective tissue
larger blood vessels
send branches to mucosa, to muscularis externa and serosa
lymphatics

Submucosa cont.
Submucosa also contains nerve plexuses
AKA Submucosal (Meissner’s) plexus
Nerve networks contain cell bodies (ganglion cells) of
postganglionic neurons
Represent the third (enteric) division of autonomic nervous system
Innervate the smooth muscle of the alimentary canal

Neurons of the enteric division show the same pathologic changes that can occur in neurons of the brain
e.g., Lewy bodies associated with Parkinson’s disease
Amyloid plaques and neurofibrillary tangles associated with Alzheimer’s disease
These finding may lead to development of routine rectal biopsies for early diagnosis of these conditions as it is not possible to biopsy the brain
Submucosa cont.

Glands occur in submucosa of esophagus and initial part of duodenum
Presence of these glands aids in identification of particular regions of gut
Submucosa cont.

Muscularis Externa
Also called the MUSCULARIS
Usually consists of two concentric thick layers of smooth muscle
Inner layer forms tight spiral seen as a CIRCULAR LAYER
outer loose spiral described as a LONGITUDINAL layer

Muscularis cont.
Located between the 2 muscle layers is a thin connective tissue layer
contains the MYENTERIC PLEXUS (AUERBACH’S PLEXUS)
Part of the enteric division of the autonomic NS
Also contains blood vessels and lymphatic vessels

Serosa & Adventitia
Serosa is a membrane containing simple squamous epithelium
the MESOTHELIUM
and a small amount of underlying connective tissue
equivalent to visceral peritoneum of gross anatomy
Continuous with the MESENTERY which holds the digestive tract in place
Contains large blood and lymphatic vessels
travel to and from mesentery to gut

Serosa & Adventitia cont.
Large amounts of fat can accumulate in serosa
Where gut has no serosa (esophagus, duodenum, ascending colon, and descending colon)
it is attached by loose connective tissue
ADVENTITIA
Adventitia blends with connective tissue of surrounding structures

Esophagus
Mucosa:
Epithelium non-keratinized stratified squamous
Lamina propria has diffuse lymphatic tissue
and lymphatic nodules
Muscularis mucosae
composed of longitudinally organized smooth muscle
M
SM
muscularis externa
A
EG
EG
D
MM
EP

Muscularis externa
IC
OL

Esophagus cont.
Submucosa along with muscularis mucosae
forms longitudinal folds
create very irregular luminal profile when seen in XS
Muscularis externa
upper 1/3 is
striated muscle
Middle third
striated and smooth muscle interwoven
Lower third
Smooth muscle
Continuous with the rest of the gut

Esophagus has adventitia until it enters abdominal cavity
where it is covered by SEROSA
Esophagus cont.

Esophagus: Glands
Two types:
ESOPHAGEAL GLANDS PROPER
ESOPHAGEAL CARDIAC GLANDS
ESOPHAGEAL GLANDS PROPER
Occur in submucosa
Scattered through out the length of esophagus; most in upper one half
Small compound tubuloalveolar glands
Produce acidic mucous

Esophagus: Glands cont.
ESOPHAGEAL CARDIAC GLANDS
occur in lamina propria of mucosa
Similar to cardiac glands of stomach
Present in terminal parts of esophagus
Esoph. Cardiac glands produce neutral mucous
protect against regurgitated material

Stomach
Expanded part of alimentary canal
Same organization as remaining gut
Mucosa
submucosa
muscularis
serosa
Inner surface has longitudinal folds called RUGAE
Poorly developed in upper stomach
more elaborate in lower part
Disappear when stomach is distended
Accommodate expansion

Stomach cont.
Numerous openings seen in mucosal surface
GASTRIC PITS or FOVEOLAE
Easily seen in SEM
Gastric glands empty into bottom of gastric pits

Histologically divided into 3 regions:
Cardia
pylorus
Fundus
Stomach cont.

CARDIA (cardiac region)
part near esophagus
contains cardiac glands
PYLORUS (pyloric region)
part proximal to pyloric sphincter
contains pyloric glands
FUNDUS (fundic region)
called the body
largest part
between cardia and pylorus
Contains fundic glands
Called gastric glands
Stomach cont.

Stomach: Gastric Secretion
2 liters of fluid/day
Gastric secretions include:
Pepsinogen
inactive precursor of proteolytic enzyme PEPSIN
HCl- (0.16N HCl)
acid pH promotes hydrolysis of food
converts pepsinogen to pepsin
Intrinsic factor
glycoprotein used for absorption of vitamin B
Hormone gastrin and others
produced by ENTEROENDOCRINE cells in gastric epithelium

Stomach: Absorption
Stomach lining absorbs
some water
salts
lipid-soluble drugs
certain drugs
Asprin enters by damaging surface epithelium
Alcohol

Stomach: Gastric Mucosa
Simple columnar epithelium
Called SURFACE MUCOUS CELLS
Cells have a large apical deposit (cap) of mucin granules
Mucous forms a thick gel-like coat on surface

Fundic Glands
Fundic glands; also called gastric glands
Produce digestive juice of stomach
Present throughout gastric mucosa
except where cardiac and pyloric glands occur
Simple branched tubular glands
Extend from bottom of GASTRIC PITS to muscularis mucosae

Fundic Glands cont.
Several glands open into one gastric pit
Each gland has
long NECK SEGMENT
BASE or FUNDIC SEGMENT
Gland may divide into 2 or 3 branches

Composed of 4 functional cell types:
MUCOUS NECK CELLS
CHIEF CELLS
PARIETAL CELLS (Oxyntic cells)
ENTEROENDOCRINE CELLS
And
UNDIFFERENTIATED CELLS
located in upper neck region
give rise to mature cells listed above
Fundic Glands cont.

PC
CC
L

Fundic Glands: Mucous Neck Cells
Located in neck region
Shorter than surface mucous cell
Nucleus tends to be spherical rather than elongate
as in surface cells
Secretes soluble mucous
compared to viscous surface mucous

Fundic Glands: Chief Cells
Typical protein-secreting cells
Occupy the basal portion of the gland
Cells easily identified by intense basophilia
Basal rER and apical granules
Secrete:
pepsin as inactive pepsinogen
a weak lipase

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

EM shows extensive INTRACELLULAR CANALICULAR SYSTEM
communicates with lumen of fundic gland
Numerous surface microvilli project from canaliculi
Secretion of HCl across membranes of canaliculi and microvillous extensions
Fundic Glands: Parietal Cell cont.

TUBULOVESICULAR MEMBRANE SYSTEM
located in cytoplasm adjacent to canalicular system
represent reserve membrane for insertion into surface
for increased secretory surface area
In humans INTRINSIC FACTOR secreted by parietal cells
absorption of vitamin B
Failure of IF secrection causes PERNICIOUS anemia
Fundic Glands: Parietal Cell cont.

Fundic Glands: Enteroendocrines
Open and closed types
Open are chemoreceptors
Located at any level of gland
sit on basal lamina
EM shows small, membrane-limited granules
Cells hard to identify
Also called:
Chromaffin cells
argentaffin cells
argyrophil cells
enterochromaffin cells

Cardiac Glands
Limited to narrow region of stomach
near esophageal orifice
Secretion, along with that of esophageal cardiac glands
contributes to gastric juice
Tubular glands
Tortuous
Composed of mainly mucous secreting cells
Some enteroendocrine cells interspersed

Pyloric Glands
Located between fundus and pylorus
Branched tubular glands
Coiled
Cells
Similar to surface mucous cells
Enteroendocrine cells interspersed
Glands empty into deep gastric pits
that occupy ½ the thickness of the mucosa