Histology of Stomach for 2nd Year Mbbs (by Dr SUNDUS)

8/2/2019 Histology of Stomach for 2nd Year Mbbs (by Dr SUNDUS)

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Dr Sundus Tariq


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Stomach

A mixed exocrine-endocrine organ Digests food and secretes hormones. It is a dilated segment of the digestive tract

whose main functions are to continue the digestion of carbohydrates initiated in

the mouth, add an acidic fluid to the ingested food, transform it by muscular activity into a viscous mass

(chyme),

promote the initial digestion of proteins with theenzyme pepsin. Produces a gastric lipase that digests triglycerides. Secretes intrinsic factor ( absorption of vitamin

B12)


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Stomach

Gross inspection reveals four regions: cardia,

fundus

body

pylorus (Figure 1515).

The fundus and body are identical inmicroscopic structure so that only threehistologically distinct regions arerecognized.

The wall in all regions of the stomach ismade up of all four major layers.

The mucosa and submucosa of the emptystomach have longitudinally directed foldsknown as rugae, which flatten when thestomach is filled with food.


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Mucosa

Rugae (longitudinal folds) Mamillated areas Gastric pits (depressions)

Several glands lying in lamina propria open

in pits Epithelium

Simple tall columnar Mucus secreting (mucinogen granules) Lubricating layer (protect against abrasion) Barrier (protect mucosa from digestion by

acid and hydrolytic enzymes) Short microvilli


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Mucosa

Lamina Propria Loose connective tissue

Glands

Numerous

Different in various regionsof stomach

Muscularis mucosae

Smooth muscle Inner circular

Outer longitudinal


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Submucosa

Loosely arranged, coarseconnective tissue

Blood vessels

Submucosal plexus

No glands


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Muscularis Externa

Three layers of smooth muscles

Inner oblique

Middle circular

Myenteric plexus

Outer longitudinal


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Serosa

Thin layer of connective tissue coveredby mesothelium


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Glands of Stomach


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1. Cardiac Glands

Cardiac orifice Pits are shallow

Simple branched tubular glands

deeper portions are coiled

Mucus

Lysozyme


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2. Principal Gastric Glands

Gastric, Oxyntic, Fundic glands

Fundus and Body of Stomach

Pits are short


Three regions

Isthmus

Neck

Body


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Four types of cells

Mucous neck cells

Parietal cells

Zymogen cells

Enteroendocrine cells


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Mucous neck cells

Location = Neck

Columnar or pyramidal

Oval basal nucleus

Mucinogen granules inapical region

Produces mucin that is lessalkaline


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Parietal cells

Location = upper half of gastricglands, with fewer in the base. Large rounded or pyramidal cells one central spherical nucleus cytoplasm that is intensely

eosinophilic due to the high densityof mitochondria

A striking feature of the activesecreting cell seen in the electronmicroscope is a deep, circular

invagination of the apical plasmamembrane, forming anintracellular canaliculus

Hydrochloric acid (HCl) Intrinsic factor, a glycoprotein

required for uptake of vitamin B12 inthe small intestine.


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Atrophicgastritis

Perniciousanemia


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Zymogen cells Chief cells

Location = Base or body

Pyramidal Spherical basal nucleus

Acidophilic scretorygranules in apical region

Pepsinogen (Inactiveenzyme)

Basal basophilia

ER


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Enteroendocrine cells Location = Base in periphery Pyramidal Stain with silver nitrate

Potassium dichromate Hormone producing cells

Gastro-entero-pancreaticendocrine (GEP system)

Four types 1. G-cells = Gastrin 2. EC-cells = Serotinin 3. D-cells = Somatostatin 4. A-cells = Enteroglucagon


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3. Pyloric Glands

Pyloric region (antrum, canal)


Pits are deep

Glands are short and tortous

Mucus secreting cells

Enteroendocrine cells

G cells

Gastrin


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Medical Application

Stress and other psychosomatic factors; ingested substances such asaspirin, nonsteroidal anti-inflammatory drugs or ethanol; thehyperosmolality of meals; and some microorganisms (eg, Helicobacterpylori) can disrupt this epithelial layer and lead to ulceration. The initialulceration may heal, or it may be further aggravated by the localaggressive agents, leading to additional gastric and duodenal ulcers.

Processes that enable the gastric mucosa to rapidly repair superficialdamage incurred by several factors play a very important role in thedefense mechanism, as does an adequate blood flow that supportsgastric physiologic activity. Any imbalance between aggression andprotection may lead to pathologic alterations. As an example, aspirinand ethanol irritate the mucosa partly by reducing mucosal blood flow.Several anti-inflammatory drugs inhibit the production of prostaglandinsof the E type, which are very important substances for the alkalinizationof the mucus layer and, consequently, important for protection.


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Documents

Histology of Stomach for 2nd Year Mbbs (by Dr SUNDUS)