HISTOLOGY OF GASTROINTESTINAL TRACT- 2

GIT-2DR.DEEPAK N.KHEDEKAR

DEPARTMENT OF ANATOMYLTMMC

DEC- 2016

05/02/2023 DR.DEEPAK N.KHEDEKAR/LTMMC/2016


• Cardiac region (cardia)- part near the esophageal orifice, contains the cardiac glands

• Pyloric region (pylorus)- part proximal to the pyloric sphincter, which contains the pyloric glands

• Fundic region (fundus)- largest part , which is situated between the cardia and pylorus and contains the fundic or gastric glands

STOMACH-Divided histologically into three regions


GASTRIC MUCOSARugae- • Longitudinal

submucosal foldsGastric pits, or

foveolae- • Numerous in the

mucosal surface. • Gastric glands open into

the bottom of the gastric pits.


GASTRIC MUCOSA

• Lining of the stomach-simple columnar E. • Columnar cells are -Surface mucous cellsSurface mucous cells :• Possesses a large, apical cup of mucinogen granules• Occupies most of the volume of the cell.• Appears empty in routine (H&E) sections because

the mucinogen is lost in fixation and dehydration. • When the mucinogen is preserved, the granules stain

intensely with toluidine blue and with the PAS


ESOPHAGOGASTRIC JUNCTION,• Stratified squamous epithelium of the esophagus ends abruptly, and the simple columnar epithelium of the stomach mucosa begins.

• Surface of the stomach show numerous and deep depressions

• Glands in the vicinity of the esophagus , the cardiac glands

• Extend from the bottom of these pits.

Fundic (gastric):• Glands arise at the base of the

gastric pits and are evident in the remaining part of the mucosa.

• Thick muscularis externa. .


RUGAE• BV- Blood vessels • M- Mamillated areas • ME- Muscularis

externa • Muc- Mucosa• SM- Smooth muscle

cells • SubM- Submucosa • Arrows three

differently stained regions of fundic mucosa;


FUNDIC MUCOSA

• Alcian Blue/PAS.• One of the gastric pits

& Associated fundic gland

• Nucleus and Golgi apparatus are located below the mucous cup.

• Basal part of the cell contains small amounts of rER that impart a light basophilia to the cytoplasm.


FUNDIC GLANDS• A- Adipocytes,BV- blood vessels• CC- Chief cells,GC- ganglion cells• ME- Muscularis externa• MM- Muscularis mucosae• MNC- Mucous neck cells• MP- Meissner’s plexus• N- Neck of fundic glands• PC- Parietal cells• SMC- Surface mucous cells• SubM- Submucosa• Arrows- Argentaffin cells• Arrowheads- nuclei of satellite

cells


FUNDIC GLANDS (GASTRIC GLANDS )

• Present throughout the entire gastric mucosa• Simple, branched, tubular glands • Extend from the bottom of the gastric pits to the

muscularis mucosae.• Has a narrow, long neck segment and a shorter and

wider base or fundic segment.



ISTHMUS OF THE FUNDIC GLAND - SITE OF STEM CELLS

• Short segment -Located between the gastric pit and the gland

• Cells destined to become mucous surface cells migrate upward in the gastric pits to surface.

• Other cells migrate downward, maintaining the population of the fundic gland epithelium.


FUNDIC GLANDS

Composed of four functionally differentcell types…

• Mucous neck cells• Chief cells• Parietal cells, also called oxyntic cells• Entero-endocrine cells• Undifferentiated adult stem cells


1.MUCOUS NECK CELLS

• Located in the neck region of the fundic gland. • Much shorter than the surface mucous cell and • Contains less mucinogen in the apical cytoplasm.• Do not exhibit a prominent mucous cup. • Nucleus tends to be spherical compared with the

more prominent, elongated nucleus of the surface mucous cell.

• Parietal cells are interspersed between these cells


2.CHIEF CELLS

• Located in the deeper part of the fundic glands.• Typical protein-secreting. • Basal cytoplasm- basophilic due the abundant

rER , • Apical cytoplasm- eosinophilic due to presence

of the secretory vesicles, zymogen granules • Zymogen granules contain enzyme precursors. • Basophilia, in particular, allows easy

identification of these cells in H&E sections


3.PARIETAL CELLS (0XYNTIC CELLS)

• Found in the neck glands, among the mucous neck cells, and in the deeper part.

• More in no. in the upper & middle part. • Large cells, binucleate, and appear triangular in

sections, with the apex directed toward the lumen of the gland and the resting on the basal lamina.

• Nucleus-spherical• Cytoplasm- stains with eosin and other acidic dyes.


CHIEF CELL VS PARIETAL CELL


Parietal cells-TEM STUDY• Show intracellular canalicular system • Communicates with the lumen of the gland. • Numerous microvilli project from the surface of the canaliculi,

and an elaborate tubulovesicular membrane system is present in the cytoplasm adjacent to the canaliculi.

• In an active cell, the number of microvilli in the canaliculi increases, and the tubulovesicular system is reduced significantly or disappears.

• Membranes of the tubulo-vesicular system serve as a reservoir of plasma membrane containing active proton pumps.


TEM


4.ENTERO-ENDOCRINE CELLS

• Found in fundic gland, more prevalent in the Base

• 2 types can be distinguishedClosed” cells- • Small cells ,rest on the basal

lamina , do not always reach the lumen;

0pen” cells-• Have a thin cytoplasmic extension

bearing microvilli that are exposed to the gland lumen


CARDIAC GLANDS OF THE GASTRIC MUCOSA

• Composed of mucus-secreting cells, with occasional interspersed entero-endocrine cells.

• Glands are tubular, tortuous, and branched.• Location- narrow region of the stomach (cardia) that

surrounds the esophageal orifice.• Secretion, in combination with that of the esophageal

cardiac glands, contributes to the gastric juice and helps protect the esophageal epithelium against gastric reflux.

• Appearance –Similar to esophageal cardiac glands.


CARDIAC GLANDS

• Tubular, tortuous, and occasionally branched.

• Composed mainly of mucus-secreting cells

• Similar in appearance to the cells of the esophageal glands.

• Mucous secretion reaches the lumen of the gastric pit via a short duct segment containing columnar cells.


FUNDO-CARDIAC JUNCTION, STOMACH,

H&E.• CG- cardiac glands • FG- fundic glands • L- lumen • LN- lymphatic nodule• MM- muscularis

mucosae• P- gastric pits • PC- parietal cells


FUNDO-CARDIAC JUNCTION, STOMACH, HUMAN, H&E.

CG- cardiac glands FG- fundic glands L- lumen ,LN- lymphatic nodule MM- muscularis mucosae ,P- gastric pits PC- parietal cells ,SM- smooth muscle cells


PYLORIC GLANDS

• Branched, coiled, tubular gland. • Location-Pyloric antrum • Lumen- wide • Appearance- cells similar to the surface mucous cells

(viscous secretion)• Enteroendocrine cells interspersed within the gland

epithelium along with occasional parietal cells. • Empty secretion into deep gastric pits• Gastric pits - Half the thickness of the mucosa.• Help protect pyloric mucosa.


PYLORIC GLANDS

•Relatively straight but are slightly coiled near the muscularis mucosae. •Lumen is relatively wide, •Secretory cells similar in appearance to the surface mucous cells. •Restricted to the mucosa and empty into the gastric pits.


LAMINA PROPRIA OF THE STOMACH• Relatively scant and restricted to the spaces

surrounding the gastric pits and glands. • Stroma - composed of reticular fibers with fibroblasts

and smooth muscle cells.• Other components- lymphocytes, plasma cells,

macrophages, and some eosinophils. • lymphatic nodules are also present, intruding into MM.

GASTRIC SUBMUCOSA• Composed of a dense connective tissue.• Contain adipose tissue,blood,nerve fibers and ganglion

cells that compose the submucosal (Meissner’s) plexus.


STOMACH -SUBMUCOSAA- adipocytesBV- blood vesselsCC- chief cellsGC- ganglion cellsME, muscularis externaMM- muscularis mucosaeMNC- mucous neck cellsMP- Meissner’s plexusN- neck of fundic glandsPC- parietal cellsSMC- surface mucous cellsSubM- submucosaarrows, argentaffin cellsarrowheads, nuclei of satellite cells


GASTRIC MUSCULARIS EXTERNA

• Outer longitudinal layer, a middle circular layer, and an inner oblique layer, Randomly oriented.

• longitudinal layer is absent from much of the anterior and posterior stomach surfaces

• Circular layer is poorly developed in the peri-esophageal region

• Myenteric (Auerbach’s) PLX- Ganglion cells and bundles of unmyelinated nerve fibers are present betwn the muscle layers.

SEROSA


SMALL INTESTINE

• Longest component of the GIT , measuring over 6 m, and is divided into three anatomic portions:

Duodenum (25 cm long) -first, shortest, and widest part of the small intestine. It begins at the pylorus of the stomach and ends at the duodenojejunal jn

Jejunum (2.5 m long)- begins at the duodenojejunal junction and constitutes the upper two fifths of the small intestine

Ileum (3.5 m long) is a continuation of the jejunum and constitutes the lower three fifths. It ends at the ileocecal junction.


SEGMENT OF JEJUNUM

• Circular folds ( plicae circulares) appear as a series of transversely oriented ridges

• Extend partially around the lumen.

• Some of the circular folds appear to end (or begin) at various sites along the luminal surface (arrows).

• Entire mucosa has a velvety appearance because of the presence of villi.


A.MUCOSA

Absorptive surface area is amplified by. PLICAE CIRCULARES, VILLIMICROVILLI


1.Plicae circulares (circular folds), valves of Kerckring

• Permanent transverse folds, contain a core of submucosa.

• Each circular fold is circularly arranged and extends about one half to two thirds of the way around the circumference of the lumen.

• Begin to appear about 5 to 6 cm beyond the pylorus. • Most numerous in the distal part of the duodenum

and the beginning of the jejunum and become reduced in size and frequency in the middle of the ileum.


2.VILLI

• Unique, fingerlike and leaflike projections, Extend from the mucosal surface for 0.5 to 1.5 mm into the lumen

• Cover the surface , giving it a velvety appearance. • Consist of a core of loose CT covered by a Simple

columnar E.• Core of the villus - an extension of the lamina propria ,

which contains fibroblasts, smooth muscle cells, lymphocytes, plasma cells, eosinophils , macrophages, and a network of fenestrated blood capillaries and also lymphatic capillary, the lacteal.


2.VILLI


3.MICROVILLI-ABSORPTIVE CELL-ENTEROCYTE

• Provide the major amplification of the luminal surface.

• Each cell possesses several thousand closely packed microvilli .

• Visible in the light microscope and give the apical region of the cell a striated appearance, the so-called striated border.


A.1.LINING EPITHELIUM

• Simple Columnar EpitheliumINTESTINAL GLANDS

(CRYPTS OF LIEBERKÜHN)• Simple tubular structures • Extend from the MM through the thickness of

the lamina propria• Open onto the luminal surface of the intestine

at the base of the villi• Lined by simple columnar epithelium that is

continuous with the lining epithelium of the villi.


A.2.LAMINA PROPRIA

• Surrounds the intestinal glands• Contains numerous cells of the immune system

(lymphocytes, plasma cells, mast cells, macrophages, and eosinophils), particularly in the villi.

• Contains numerous nodules of lymphatic tissue that represent a major component of the GALT.

• Nodules are large and numerous in the ileum, where they are located on the side of the intestine opposite the mesenteric attachment .

• Nodular aggregations are known as aggregated nodules or Peyer’s patches.


A.3.MUSCULARIS MUCOSAE

• Consists of two thin layers of smooth muscle cells, an inner circular and an outer longitudinal layer.

• Strands of smooth muscle cells extend from the muscularis mucosae into the lamina Propria of the villi.


CELLS IN INTESTINAL MUCOSALEPITHELIUM.

They include the following:Enterocytes- whose primary function is absorptionGoblet cells- unicellular mucin-secreting glandsPaneth cells- whose primary function is to maintain

mucosal innate immunity by secreting antimicrobial Substances

Enteroendocrine cells- which produce various paracrine and endocrine hormones

M cells (microfold cells)- modified enterocytes that cover enlarged lymphatic nodules in the lamina propria


ENTEROCYTES

• Tall columnar cells with a basal Nucleus • Microvilli -increase the apical surface area as

much as 600 times;• form a striated border on the luminal surface• Lateral cell surface exhibits elaborate, flattened

cytoplasmic processes (plicae) that interdigitate with those of adjacent cells .

• Folds increase the lateral surface area of the cell, thus increasing the amount of plasma membrane containing transport enzymes


ENTEROCYTE


GOBLET CELLS

• Unicellular glands, produce mucus ,are interspersed among the other cells of the intestinal epithelium.

• Increase in number from the duodenum to the terminal part of the ileum.

• As water-soluble mucinogen is lost during preparation of routine H&E sections, the part of the cell that contains mucinogen granules appears empty.

• Examination with the TEM- reveals a large accumulation of mucinogen granules in the apical cytoplasm that distends the apex of the cell and distorts the shape of neighboring cells


GOBLET CELL• Basal portion of the cell contains the nucleus, rER, and mitochondria.

• Just apical to the nucleus are extensive profiles of Golgi apparatus. As the mucous product accumulates in the Golgi cisternae, they become enlarged.

• Mucous cup -Large mucinogen granules fill most of the apical portion of the cell.


PANETH CELLS

• Found in the bases of the intestinal glands• Occasionally found in the normal colon in small

numbers; No. increases in pathologic conditions. • Have a basophilic basal cytoplasm, a supranuclear

Golgi apparatus, and large, Intensely acidophilic, refractile apical secretory vesicles.

• Vesicles allow their easy identificationPaneth cells play a role in regulation of normal

bacterial flora of the small intestine.


BASE OF INTESTINAL (JEJUNAL) GLANDS IN AN

H&E

Paneth cells- located in the base of the

intestinal glands , readily intensive eosin staining of

vesicles. LP- contains of plasma cells,

lymphocytes, and other CT cells.

Inset. High magnification – Basophilia in the basal portion

of the cell and Eosinophilic, refractile

secretory vesicles in the apical portion of the cell.


M CELLS

• Cells that overlie Peyer’s patches and other large lymphatic nodules;

• Differ significantly from the surrounding intestinal epithelial cells .

• Have microfolds rather than microvilli on their apical surface, and they take up Microorganisms and macromolecules from the lumen in endocytotic vesicles.

M cells convey microorganisms and other macromolecules from the intestinal lumen to Peyer’s

patches.


ENTERO-ENDOCRINE CELLS

• Resemble those that reside in the stomach . • “Closed cells”- concentrated in the lower portion of

the intestinal gland,whereas the • “Open cells” -found at all levels of each villus.• Activation of taste receptors -found on the apical

cell membrane of “open cells” activates G protein–signaling cascade, resulting in releasing of peptides that regulate a variety of gastrointestinal functions.


INTERMEDIATE CELLS• Constitute most of the cells found within the

intestinal stem cell niche• Located in the lower half of the intestinal gland. • Constitute the amplifying compartment of the cells• Capable of cell division and usually undergo one or

two divisions before they become committed to differentiation into either absorptive or goblet cells.

• Have short, irregular microvilli with long core filaments extending deep into the apical cytoplasm and numerous macular (desmosomal) junctions with adjacent cells.


Intermediate cells(Stem cells)

Goblet cells (Increase in

secretory granules)

Absorptive cells(Loss of secretory

granules)


GALT

• LP of the GI tract is heavily populated with elements of the immune system;

• Approximately one-fourth of the mucosa consists of a loosely organized layer of lymphatic nodules, lymphocytes, macrophages, plasma cells, and eosinophils in the lamina propria.

• Lymphocytes are also located between epithelial cells.

GALT serves as an immunologic barrier throughout the length of the gastrointestinal tract.


SUBMUCOSA• Consists of a dense CT and localized sites that

contain aggregates of adipose cells.• Distinguishing characteristic of the duodenum is the

presence of submucosal glands i.e Brunner’s glands (Branched, tubular,have secretory cells with characteristics of both zymogen secreting and mucus-secreting cells.

Muscularis externa• Consists of an inner circular and an outer

longitudinal smooth muscle cells with Myenteric plexus (Auerbach’s plexus)


1.DUODENUM-BRUNNERS GLAND

• Dashed line -boundary between the villi and the typical intestinal glands (crypts of Lieberkühn). extending to the MM.

• Submucosa-contains Brunner’s glands.

• These are branched tubular glands whose secretory component consists of columnar cells.

• Duct of the Brunner’s gland -opens into the lumen of the intestinal gland (arrow). 120.


1.Duodenum


1.Duodenum


2.Jejunum.

PC- plicae circulares, Muc- mucosa, V- villi ,ME- muscularis externa, SubM- submucosa


2.Jejunum.• EC- endothelial cell• GC- goblet cell• GI- intestinal glands• L- lacteal• LP- lamina propria• Ly- lymphocytes• M- smooth muscle• MM- muscularis m.• S- serosa• SB- striated border• Arrow- basal processes

of enterocytes• asterisks, basal-lateral

intercellular spaces• dashed line-boundary

between villi and intestinal glands


• LN, lymphatic nodules ME, muscularis externa• Mucosae SM, submucosa V, villi

ILEUM


ILEUM Gl- intestinal glands, MM- Muscularis Mucosae MM??- presumptive location of muscularis ,Asterisks- leaf like villus


LARGE INTESTINE


COLON

BV- blood vessels , ME- muscularis externa ME(c), circular layer of muscularis externa ME(l)- longitudinal layer of muscularis externa Muc, mucosa S, serosa SubM, submucosa TC, tenia


Mucosa• Smooth surface, Neither plicae circulares nor villi are

present.• Contains numerous straight tubular intestinal glands• Glands extend through the full thickness of the mucosa • Glands consist of simple columnar epithelium, as does the

intestinal surface from which they invaginate. • O/E of luminal surface at the microscopic level reveals the

openings of the glands, which are arranged in an orderly pattern

• Morphology of absorptive cells is essentially identical to that of the Enterocytes of the small intestine


The mucosal epithelium of the large intestine contains the same cell types as the small intestine except Paneth cells, which are

normally absent in humans• Columnar absorptive cells predominate (4:1)

over goblet cells



COLON

• A- Adipose tissue, GI- intestinal glands , LP-lamina propria , Arrows- opening of intestinal glands


LAMINA PROPRIA

• 1.Collagen table- thick layer of collagen and proteoglycans lies between the basal lamina of the epithelium and that of the fenestrated absorptive venous capillaries.

• 5 m thick in the normal human colon.• participates in regulation of water and

electrolyte• transport from the intercellular compartment of

the epithelium to the vascular compartment


LAMINA PROPRIA

Pericryptal fibroblast sheath- • constitutes a well developed fibroblast population

of regularly replicating cells. • Divide immediately beneath the base of the

intestinal gland, adjacent to the stem cells. • fibroblasts then differentiate and migrate upward

in parallel and synchrony with the epithelial cells. GALT LYMPHATIC VESSELS


COLON

• AC- absorptive cells ,GC- goblet cells ,M-mitotic figures, MM- muscularis m., Arrowheads- smooth muscle cells showing rounded nuclei coli ,Asterisks- lumen of intestinal glands ,


MUSCULARIS EXTERNA• Outer layer, condensed into prominent

longitudinal bands of muscle, called teniae coli,• Inner, circular layer of muscle at irregular

intervals along the length and circumference of the colon.

SUBMUCOSA AND SEROSA


VERMIFORM APPENDIX


vermiform appendix• Displays the same four layers as those of the large

intestine • Its diameter is smaller.• Typically, lymphatic nodules are seen within the entire

mucosa and usually extend into the submucosa. • Distinct germinal centers within the lymphatic nodules. • Muscularis externa is composed of a relatively thick

circular layer and a much thinner outer longitudinal layer. • Covered by a serosa that is continuous with the

mesentery of the appendix


Cl- gland, L- lumen , LN- lymphatic nodule, ME- muscularis externa, Muc- mucosa S- serosa, Subm- submucosa


BV- blood vessel ,Cap- cap of lymphatic nodule GC- germinal center


VERMIFORM APPENDIXARROWS- MUSCULARIS MUCOSAE AT BASE OF GLANDS


THE END

Health & Medicine

HISTOLOGY OF GASTROINTESTINAL TRACT- 2