Histology, Lecture 1, Introduction to Histology (Lecture Notes)
Histology of Stomach for 2nd Year Mbbs (by Dr SUNDUS)
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Transcript of 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
Simple branched tubular glands
Three regions
Isthmus
Neck
Body
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2. Principal Gastric Glands
Four types of cells
Mucous neck cells
Parietal cells
Zymogen cells
Enteroendocrine cells
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2. Principal Gastric Glands
Mucous neck cells
Location = Neck
Columnar or pyramidal
Oval basal nucleus
Mucinogen granules inapical region
Produces mucin that is lessalkaline
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2. Principal Gastric Glands
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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2. Principal Gastric Glands
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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2. Principal Gastric Glands
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)
Simple branched tubular glands
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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