HISTOLOGY OF DIGESTIVE SYSTEMOESOPHAGUS, STOMACH-

FUNDUS & PYLORUS

Dr. Makarchuk Iryna

INTRODUCTION BASIC PATTERN:I) Mucosa

- Epithelium

- Lamina propria

- Muscularis Mucosae

II) SubmucosaIII) Muscularis ExternaIV) Serous layer /

Adventitial layer

MUCOSA EPITHELIUM:

It is columnar (Absorption/secretion) all over except in the Oesophagus and the lower part of Anal canal where it is stratified squamous (Protection).

- Numerous folds- Crypts – At numerous

places epithelium dips into the Lamina propria and form crypts (Simple tubular glands).

Villi:In Small intestine, Mucosa bears numerous finger-like processes that project in the lumen.

Glands:1. Unicellular secretory cells are scattered among the cells of the lining epithelium.2. In some parts of GIT, Compound tubulo-alveolar glands are present in the submucosa.

LAMINA PROPRIA:- Made up of Collagen and reticular fibres.- contain blood capillaries, lymph vessels and nerves- In SI, the core of villus is attached to the lamina propria.- Prominent aggregation of lymphatic tissue is seen in Lamina propria (MALT)

MUSCULARIS MUCOSAE- Thin layer of smooth

muscle that seperates lamina propria with the submucosa.

- Inner layer: Circular- Outer layer: Longitudinal- Contraction of Muscularis

Mucosa is important for the local mixing of intestinal contents

- It changes the shape of mucosa, that helps in absorption and secretion

SUBMUCOSA This layer consists of

loose areolar tissue that connects mucosa to the muscularis externa.

Its looseness permits some mobility of mucosa over the muscularis externa.

Contain numerous blood vessels, lymphatics and nerve fibres and Meissner’s plexus.

MUSCULARIS EXTERNA It consists of smooth muscles

all over GIT except upper part of oesophagus which contain skeletal muscles.

Arranged in two layers - Inner layer: Circular - Outer layer: Longitudinal Between the two layers

“Auerbach’s plexus (Myenteric plexus)” is present.

- Inner circular layer acts as sphincter. Eg: Pyloric sphincter, Internal anal sphincter, Ileo - caecal valve

SEROSA /ADVENTITIAL LAYER It is merely visceral

peritoneum composed of connective tissue and simple squamous epithelium.

The oesophagus lies outside the abdominal cavity has a superficial layer called Adventitia which consists of areolar connective tissue

OESOPHAGUS It is a straight muscular tube extending from pharynx to the stomach in abdomen.

MUCOSA:Epithelium: Non-Keratinised sratified squamous epitheliumLamina Propria: Thin layer of loose CT.Muscularis Mucosae: - It is thicker than other parts of GIT- It is single layer of longitudinally running smooth muscle fibres.

SUBMUCOSA:- It is a wide layer of irregular,

moderately dense connective tissue composed of bundles of collagen and elastic fibres.

- Due to elastic fibres mucosa is thrown into folds, hence lumen of oesophagus appears star shaped

- Contains blood vessels and branched tubulo- alveolar mucous glands

MUSCULARIS EXTERNA

Arranged in two layers: - Inner layer: Circular - Outer layer: Longitudinal* Between the two layers –

Myenteric plexus of nerve fibre and ganglion cells are present. It controls peristaltic movement.

TYPES OF MUSCLES:Upper 1/3rd – Skeletal muscleMiddle 1/3rd – Both skeletal and

smooth muscleLower 1/3rd – purely smooth

muscle

SEROSA / ADVEVTITIA

It consists of loose areolar connective tissue, which merges with the connective tissue of surrounding structures.

CARDIO-OESOPHAGEAL JUNCTION

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

CARDIAC REGION OF THE STOMACHMucosa: Epithelial lining at the

cardio-oesophageal junction changes from stratified sq. to simple columnar epithelium

Presence of Mucous surface cells and cardiac glands

Submucosa:Consists of Meissner’s plexus and blood vessels

Muscularis externa:Inner – ObliqueMiddle – circularOuter – longitudinalMyenteric plexus between

muscle layersSerosa – Simple squamous

epithelium resting on a thin layer of connective tissue

STOMACH - FUNDUS Mucosa:- Lining Epithelium – Simple

columnar epithelium that invaginates to various extents into the lamina propria, forming gastric pits.

- These cells are involved in mucus secretion. The mucus protects the epithelial lining from damage due to the presence of acid in the stomach.

STOMACH – FUNDUS

Lamina propria:- Small tubular fundic/gastric

glands are present.- Types of cells:i) Mucous neck cells – Located

just below gastric pit. - Columnar in shape- Contain mucinogen granules in apical cytoplasm, while nuclei are basally situated basally.- Produces soluble mucus

Parietal or oxyntic cells:- They are large, ovoid or

polyhedral cells with a large central nucleus.

- More numerous in the upper half of the gland than in the lower half

- Secretes HCL and intrinsic factor. Intrinsic factor combines with vitamin B12 to form a complex necessary for erythrocytes formation.

Chief or zymogenic cells:- Located in the lower 1/3rd of gastric glands.- Contain rough endoplasmic reticulum near the base, secretory granules near their apex and a small golgi apparatus.- Secrete pepsinogen which is converted into pepsin in an acid environment.

Enteroendocrine and APUD cells:- Located in the basal portion of gastric glands- Secretes serotonin, histamine and gastrin. These are endocrine cells which release their products into the blood vessels.

MUSCULARIS MUCOSAE:- It consists of two thin layer of smooth muscles.i.e., Outer longitudinal and

inner circular

SUBMUCOSA:- Consists of blood vessels, lymphatic vessels and Meissner’s plexus.

MUSCULARIS EXTERNA:Inner: ObliqueMiddle: circularOuter: Longitudinal

SEROSA:Outermost layers of the stomach which consists of loose connective tissue covered by mesothelium

STOMACH - PYLORUS

MUCOSA:- Epithelium: Simple

columnar as in fundic part- Pyloric glands occupy the

lamina propria- Gastric pits are deeper- Glands are short,tortuous

and branched- Produce mucus and gastrin- Muscularis mucosa and

Submucosa are similar to fundic part

MUSCULARIS EXTERNA:Inner: ObliqueMiddle: circularOuter: Longitudinal

Similar to Fundic part, but the circular fibres are much thickened to form pyloric sphincter

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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 than pyloric gland

Gastric pit less deeper than pyloric gland

Gastric pit more deeper than gastric or cardiac gland

Parietal cells absent or very few

Parietal cells more Parietal cells few

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CLINICAL ASPECTS GASTRO- ESOPHAGEAL

REFLUX DISORDER:A condition which is characterised by the compromised state of the lower oesophageal sphincter, which leads to reflux of food and acid into oesophagus.

OESOPHAGOSCOPY:This may be indicated in patients with persistent oesophageal symptoms such as atypical chest pain, dysphagia, odynophagia (painful swallowing) or symptoms of reflux.

OESOPHAGEAL RUPTURE The majority of oesophageal ruptures are iatrogenic.

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