Histology of upper GIT

EDITH NAGAWA
Contents
Oral cavity
Tongue
Esophagus
Stomach

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 Introduction
Gastrointestinal tract is
a long , hollow tube or
tract
Extends from oral cavity
to anus

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General structure of GIT
Consists of four layers:
Mucous layer
Submucous layer
Muscular layer
Serous layer

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 Mucous layer
Mucosa comprises:
Epithelial lining
Lamina propria
 Consists of loose connective tissue
rich in blood and lymph vessels
Muscularis mucosae
 Consists of inner circular layer and an
outer longitudinal layer of smooth
muscle cells
 It separates the mucosa from the
submucosa

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Function of mucosa
Secretion
Absorption
Barrier
Immunologic protection

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Submucous layer
Composed of dense irregular connective
tissue and contains:
 blood and lymph vessels
 submucosal or Meissner’s nerve plexus
 glands and lymphoid tissue

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Muscular layer
It contains smooth muscle cells that are spirally
oriented and divided into two sublayers:
 Internal sublayer is circular
 External sublayer is longitudinal
 Myenteric or Auerbach’s nerve plexus lies between
two muscle sublayers

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Serous layer
Consists of thin layer of loose connective tissue

Rich in blood and lymph vessels, and adipose tissue

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Oral cavity
Oral cavity is lined with stratified squamous epithelium,
keratinized or nonkeratinized, depending on the region
The keratin layer protects the oral mucosa from damage
during masticatory function
The keratin layer is present in the gingiva and hard palate
Nonkeratinized stratified squamous epithelium covers the
soft palate, lips, checks and the floor of the mouth

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Tongue
The tongue is a mass of striated muscle covered by a
mucous membrane
The dorsal surface of tongue is rough due to presence of
papillae
The ventral surface of tongue is smooth
The posterior one-third of dorsal surface is separated
from the anterior two-thirds by a V-shaped boundary

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Papillae
Papillae are elevations of epithelium and lamina
propria. There are four types of papillae:
Filiform papillae - slender, conical shape, most
numerous, cover the entire dorsal surface
Fungiform papillae - less numerous, have broad round
surface resemble mushrooms
Foliate papillae – poorly developed in humans
Circumvallate papillae – large circular papillae with
flattened surfaces, distributed in the V region in the
posterior portion of the tongue

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Tongue: circumvalate papillae

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Muscles of tongue (Anterior part of
tongue)
The tongue consists of criss-crossing bundles of
skeletal muscle
The muscles are longitudinal, transverse or oblique
The connective tissue around the muscle bundle
contain blood vessel
Anterior lingual gland – lies in the lower half of the
tongue and opens on the ventral surface of the
tongue

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Anterior region of the tongue

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Posterior tongue behind circumvallate papilla
Dorsal surface of posterior region exhibits large mucosal ridges
Nonkeratinized stratified squamous epithelium covers the
mucosal ridges
Lamina propria of the mucosa is wider but similar to that in the
anterior two-thirds
Lamina propria contains diffuse lymphatic tissue,
accumulation of adipose tissue, nerve fibers and blood
vessels
Skeletal muscle lies beneath the lamina propria
The posterior lingual gland opens onto the dorsal surface

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Posterior tongue behind circumvallate papillae

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Esophagus
Esophagus is a muscular tube extends from the
pharynx to the stomach
Histologically it consists of four layers:
 mucosa
 submucosa
 muscularis externa
 adventitia / serosa

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Upper esophagus

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Mucosa
Mucosa consists of three parts:
 epithelium – nonkeratinized stratified squamous epithelium
 lamina propria – lies below the epithelium, consists of thin
layer of fine connective tissue, contains small blood vessels, diffuse
lymphatic tissue and a small lymphatic nodule

 muscularis mucosae – consists of a layer of longitudinal

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Submucosa
Submucosa:
a wide layer of moderately dense irregular connective
trissue,
Contains adipose tissue, esophageal glands and blood
vessels

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Muscularis externa
Muscularis externa located inferior to the
submucosa
Composed of two well-defined muscle layers:
inner circular and outer longitudinal
Muscularis externa in:
 Upper third of esophagus consists of skeletal muscles
 Middle third consists of both skeletal and smooth muscle
 Lower third, only smooth muscle is present

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Adventitia / serosa
Adventitia / Serosa :
 In the thoracic cavity, the outer most layer of the
esophagus is called adventitia
 In the abdominal cavity, the outer most layer of the
esophagus is called serosa
 It consists of connective tissue layer and contains
adipose tissue, blood vessels and nerves

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Esophageal-stomach junction

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Stomach
Stomach is a dilated segment of the digestive tract, that
digest food and secrets hormone
There are three histological regions:
 Cardia
 Fundus and body
 Pylorus
The fundus and body are identical in microscopic
structure
The mucosa and submucosa of the undistended stomach
lie in longitudinally directed folds known as rugae
When the stomach is filled with food, folds flatten out

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Histological structure
Stomach has four histologic layers:
 Mucosa
 Submucosa
 Muscularis externa
 Serosa

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Stomach mucosa of the fundus and body

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Mucosa
Mucosa consists of:
 Surface epithelium – simple columnar, that invaginates to
various extents into the lamina propria, forming gastric pits
 Lamina propria – composed of loose connective tissue,
contains gastric glands, lymphatic tissue or small lymph
nodule
 Gastric glands contain two distinct cell types – acidophilic
parietal cells and basophilic chief cells
 Muscularis mucosae

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Submucosa
Submucosa lies below the muscularis mucosae

It is composed of dense irregular connective tissue

It contains small blood vessels, and isolated or clusters

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Muscularis externa
Muscularis externa consists of three layers of smooth
muscle
 Inner oblique muscle layer
 Middle circular muscle layer
 Outer longitudinal muscle layer
Myenteric (Auerbach’s) nerve plexus of
parasympathetic ganglia and nerve fibers is located
between the circular and longitudinal smooth muscle
layers

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Serosa
Serosa consists of thin connective tissue that
overlies the muscularis externa

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Fundic mucosa

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Basal region of fundic mucosa

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Mucosa of pyloric region

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Difference between cardia, fundus & body, and pylorus

Cardia Fundus & body Pylorus

Contain cardiac gland Contain gastric gland Contain pyloric gland

Gastric pit less deeper Gastric pit less deeper Gastric pit more deeper
than pyloric gland than pyloric gland than gastric or cardiac
gland

Parietal cells absent or Parietal cells more Parietal cells few

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References
Basic Histology – Luis Carlos Junqueira, 11 th edition

diFiore’s Atlas of Histology – 10th edition

Histology A Text and Atlas – Michael H. Ross, 4 th

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