Esophagus & Gastrointestinal Tract Pictures

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4 Major Layers of GI Tract
-->Mucosa, Submucosa, Muscularis Externa/Propria, Adventitia/Serosa

Example of Protective (Above)(Ex. Stratisfied Squamous Ep.; Esophagus) & Secretatory (Below)(Stomach)

Example of Absorptive (Above)(Ex. Simple Columnar Epithelium; SI) and Aborptive/Protective (Below)(Ex. Simple Columnar Epithelium; Reabsorptive of water; LI)

Simple Columnar Epthelium
-->Goblet Cells
-->Microvilli covering surface of the intestinal villi

Lamina Propria
-->Microvilli on Apical Surface of simple columnar epithelium
-->Plasma Cells in lamina propria

Deep Layers Layers of GI Tract
-->Messiner's Ganglion ("Submucosal Ganglion")(PG)

Muscularirs Mucosa (2 Layers: Circular & Longitudinal)

Meissner's Ganglion/Submucosa Plexus
-->Eccentric Nucleus

Myentric/Auerbach's Ganglion betwn. the 2 Layers of Muscularis Externa
-->The plexus (ganglion & nerve)

Aurbach's Plexus in Muscularis Externa
1) Serosa (Corvered by 1 layer of squamous epithelium)

Esophagus (Oropharynx to Stomach)
-->Star Shape Lumen
-->Observe Difference betwn Circular & Longitudinal Muscle

Middle 1/3 of Esophagus (smooth & skeletal muscle)

Esophageal Mucosa

Esophageal Mucosa & Submucosa
-->**Contain Esophageal Gland Proper in Submucosa**

Mucosa of Esophague (Srat. Squamous non-ker. epithelium)
-->Lamina Propria underneath epithelium

Mucous gland in the Submucosa of Esophagus ("Esophageal Gland Proper")
-->Mucus cell nuclei are condensed & flattened against basement membrane

Gastro-esophageal Junction
-->See transition from stratisfied squamous epithelium (esophagus on far right) to simple columnar epithelium of the stomach (left)

Gastro-esophageal Junction

Upper 1/3 of Esophagus
-->Esophageal Gland Proper of Submucosa
-->Muscularis externa contains skeletal muscle

Skeletal Muscle of Muscularis Mucosae in upper 1/3 of esophagus

Lower 1/3 of Esophagus
-->Smooth muscle in outer muscularis externa

Gastro-Esophageal Juntion =

Glands in GE Junction
**CARDIAC GLANDS in lamina propria**(Secrete products in gastric pits)
***ESOPHAGEAL GLAND PROPER in submucosa of esophagus

Cardia of Stomach
-->Shallow gastric pit & short gastric gland
-->See the **CARDIAC GLANDS** in the lamina propria (Branching and coiled)

Cardiac Gland leading in from a gastric pit (upper right)
-->Cardiac gland produces mucus by **Surface mucus cell**
--Mucus prevents HCl from destroying the epithelium that surrounds the stomach

Mucosal Surface Of The Stomach
-->Arrows on the left represents the openings of glands from cardia, corpus (body), or pylorus

Body of the stomach
-->Same histologically as the fundus
-->Short & shallow gastric pit (GP)
-->Contains long, tubular gland that occupies entire length of lamina propria
-->***STOMACH contains 3 layers in muscularis externa (inner oblique, inner circular, & outer longitudinal)

3 Layers of Muscularis Externa of the stomach

Junction betwn. cardia & fundus (Cardiac vs. Fundic Gland)

Fundus or Corpus of Stomach
-->Surface Mucus cells (upper right) & parietal cells (large, eosinophillic cytoplasm; centrally placed nucleus, & fried-egg appearence ~oligodendrocytes)
-->Chief cells seen on bottom near bottom with granules of pepsin (basophilic due to high ribosome content)

Fundus & Corpus of Stomach

Gastric Cells of Gastric Gland of fundus/body
-->Surrounds a gastic pit (secretes mucus on the surface)

Surface mucous cells & Neck mucous cells

Parietal & Chief Cells

Schematic of Parietal Cell

Parietal Cell on EM
-->High amounts of mitochondria
-->Intracellular Caniculi ("Inside the cell")
-->Tubulovesicular System

Schematic of Chief Cell

Chief Cell on EM
-->Zymogen Granules
-->Rough ER
-->Supranuclear Golgi Apparatus

Base of Gastric Gland
**Contains Neuroendocrine Cells**
-->Also see parietal cell & gastric cell (Pc; peptic cell)

Pyloric Stomach
-->Contains DEEP gastric pits that run ~1/3 the length of the lamina propria
-->The second half becomes coiled (Gastric Gland) & contains "G" Cells that STIMULATE chief cells to produce HCl

Overview of Pylorus of the stomach

Pyloric Glands in the lamina propria

Pyloric Glands in the lamina propria

Gastroduodenal Junction
-->Contains Pyloric sphincter (PS), glandular mucosa of the stomach (S), Mucosa of Duodenum (D), Brunners Gland (B), and 2 layers of muscularis externa (CM & LM; ***no oblique layer)
-->***Brunner's Gland in the mucus secreting glands in SUBMUCOSA OF THE DUODENUM

Small Intestine
-->Distinct characteristics
1)Villi on outside surface cover the transverse folds (plicae circulares)
-->Microvilli on top of villi
2)**Brunner's Glands in Submucosea ALWAYS indicate that you are in DUODENUM

-->Contains Brunner's Glands in submucosa

Intestinal Villi & Crypts of SI
-->Lined by simple columnar epithelium
-->Other important cell types (some not visible in picture):
1)Goblet cells
2)Paneth cells (***Prominent, eosinophilic apical granuels; fxn. is defensive)
3)Neuroendocrine cells
4)Stem Cells (***At base of the crypts)

Intestinal Villi of SI
Note: Both mucus & glcocalyx both protect the epithelium against AUTODIGESTION

Brunners glands in subucosa of SI

***Crypts of Lieberkuhn of the duodenum

Intestinal Villi ("Fingerlike projections")
-->Also contain lymph capillaries in the CORE OF VILLUS

Central Lacteal in the Intestinal Villi
-->Lacteal represent a blind-ended lymphatic capillary that may contain smooth muscle that is NOT APART OF MUSCULARIS MUCOSAE
1)Major fxn is to bring lipid-absorbed substances from the lumen into the lacteal

Intestinal Villi
-->Can be variable in shape
-->Lacteal on the far right contains a CENTRAL LACTEAL

Intestinal Villus of rat
-->Illustrates presense of absorped lipids
-->Black stain represents high amount of lipid in enterocyte cytoplams & chylomicrons (lipoprotein droplets)
1)Chylomicrons will use the central lacteal to enter systemic circulation

Topagraphy of Duodenum

Topagraphy of Jejunum

Topagraphy of Illeum
-->High aggregation of lymphoid is seen as PEYER'S PATCHES

Villous of Jejunum
-->Contains High number of GOBLET CELLS

Lymphocytes Aggregation In Jejunum

-->Contains valves of Kerckring & Peyer's Patches

Enterocyes (*See Wheaters for bigger image)
(1)Features of enterocytes (upper pic.)
-->Large # of microvilli that represent the BRUSH BORDER microscopically
-->Mitochondria (M) in high amounts
-->Intercellular Clefts (IC) & basement membrane (BM) represent layers chylomicrons must pass to enter core of the villus
->Lymphocytes found in the intercellular clefts in betwn. enterocytes
(2)Features of enterocytes (lower pic.)
-->Prominent GYCOCALYX on enterocyte microvilli
-->Terminal web sen at bottom of microfilament cytoskeletion of microvilli (Def:A dense meshwork of spectrin and myosin molecules located at the base of a microvillus to which the bundle of actin microfilaments that make up the core of the microvillus is anchored)

Basal Aspect of 2 Enterocytes
-->Contains intracellular cleft betwn 2 enterocyte cell
-->Endothelium of central lacteal

Goblet Cell

Crypts of Lieberkuhn of SI
-->Contains **PANETH CELLS**
1)Intensly eosinophilic apical cytoplasmic granules
2)Granules contain **DEFENSINS**(antimicrobial peptides) and **LYSOZYME & PHOSPHOLIPASE A (protective enzymes) that serve as the first line of defense against any pathogens that survive passage through the stomach (i.e. "Natural form of antibiotic")

Capillary Network of the Intestinal Villi
**Most of absorbed food products enter the capillaries & pass via the portal vein to the liver EXCEPT TRIGLYCERIDES**

Prominent Peyers Patches of lymph nodules in the lamina propria of Ileum

Aurbach's Plexux in SI
-->In betwn inner circular & outer longitudinal SM

Ileocacecal Junction
-->See transition of lining of IC Valve from small intestines (villiform patters; S) to glandular form in the LI *L)
-->Ileocecal valve consists of a thickened extension of muscularis propria (M) that provides robust support for the mucosa
-->Lymphoid tissue (lymphoid tissue (Ly) in form of large Peyer's Patches are found in the mucosa

Coeliac Disease (Coeliac Sprue or Gluten Enteropathy)
-->Caused by an immunologic response to gluten (component of wheat, oats, barley, rye)
-->Individuals with condition present with symptoms of malaborption (weight loss, steatorrhoea, anemia, vitamin deficiences) b/c fewer NUTRIENTS are able to be absorbed
->***Biopses of small bowel for diagnosis will displayL
1)Loss of normal intestinal villi
2)Incr. of lymphocytes & plasma cells in lamina propria

Large Intestine
-->Contains absorptive cells & mucus-secreating goblet cells arranged in CRYPTS (closely packed straight tubular glands) that extend into the MUSCULARIS MUCOSEA
***Contains NO VILLI
-->Mucosa forms longitudinal folds (COLUMNS OF MORGANI) above anal valves
-->Muscularis Mucosae rhythmically contract to prevent clogging of the glands & enhance the expulsion of mucus

Muscular wall of large intestine
-->**Can see tenia coli in the longitudinal layer of muscularis externa (**Not seen in the rectum)

Mucosa of Colon
-->Arrows point to opening of crypts of Leiberkuhn (straight, unbranched tubular glands
-->Lamina propria seen IN BETWEEN the glands
-->Opening of the crypts of Luberkuhn makes the feces MORE COMPACT via lubrication (feces is easier to move)

Absorptive & Goblet Cells of the Colon

Crypts of Colon containing many goblet cells

Pictures of colon
-->Alcian blue method stains goblet cell cell mucus greenish blue vs poorly stained absorptive
1)Goblet cells encompass BASE OF GLAND
2)Absorptive cell found mostly in the luminal surface

Colrectal Adenocarcinoma
-->Affect older patients 50-60 yrs. old
-->Is a *malignant tumours arising in the glandular epithelium

-->Structure similar to that of large intestine
-->Contain large masses of lymphoid tissue in mucosa & submucosa (*Esp. in the young)
-->High # of lymphocytes in lamina propria
1)Lymphoid tissue forms follicles that contain germinal centers (***Invested by a simple epithelium of M Cells; M Cells facilitate the sampling of antigen in the lumen)
-->Less packed mucosal glands than in large intestine

Recto-anal Junction
-->in anus you see sebaceous and LARGE apocrine glands

-->Contains large apocrine glands and **complete muscularis externa**(anal sphincter

Topagaphy of anal canal

Micofold (M) Cells
-->Epithelial cells that overlie Peyer's patches & other large lymphatic nodules

M Cells are APC's b/c they contain both MHC Class I & MHC Class II (**ERORR ON SLIDE**)

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