Gastro Lab Manual
Transcript of Gastro Lab Manual
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Gastrointestinal Lab Manual
Histology
dr. Jan Tambayong, PHK
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Gastrointestinal Lab Manual
Introduction
Students will work individually. Sit anywhere.
This lab manual contains instructions for each one of the GI
labs. Each student will be supplied with GI microscopic slides at
the beginning of each lab session.
Wear a white lab coat every time you enter the lab room.
Please return your microslides at the end of every lab. This lab manual is for your personal use only.
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Gastrointestinal Lab Manual
Important Information on the Lab Exam
The Lab Exam will be a bell ringer exam.
There will be an integrated lab exam, called OSPE(Objective Structured Practical Exam) for each block,
consisting of disciplines involved in the same block (egAnatomy, Histology, Pathology, etc), usually consisting of 14or 15 stations.
Each station will have one first-order question and onesecond-order question.
Second-order questions will include: Specific features
Function
Your reasoning
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LABORATORY 1
Introduction to the Gastrointestinal System
The purpose of this session is to provide you with
an overview of the structure of the upper GI tract,
ie. Lips, esophagus and stomach.
Identify the similarities and differences between
gastric mucosa, small intestinal mucosa and
colonic mucosa.
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The Lips
When examining this microslide, you notice a
structure with rounded end, lined by stratified
squamous epithelium. One side is covered by skin,
with integument of skin like hair follicles,sebaceous glands; this part is the outer part of the
lips.
Adjacent to this is a curved part: red portion of
your lips. Beyond that is the inner part of the lips,
entirely composed of mucous epithelia.
Teeth development
With small magnification, find the part containing
tooth buds, showing the development of teeth.
Try to locate : Enamel/email : dark magenta colored
Dentin : pink colored
Predentin : slightly pink
Ameloblast : closer to enamel
Odontoblast : closer to dentin
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Sexy Lips
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Cleft Lips
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Deciduous teeth
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The Tongue
Notice the unique pattern of the muscles, like the
pattern of tikar. The orientation of the muscle
fibers are in three directions: horizontal, transverse
and vertical, in accordance with its function.
Circumvallate Papillae
Observe the surface of the tongue. Youll find a
large rounded structure, most of which are
embedded beneath the tongue surface. This
structure, the circumvallate papillae, is surrounded
by a deep groove, lined by stratified epithelia which
contains small rounded structures, the taste buds, at
its periphery wall. Beneath the groove are serous
glands, the Ebners gland, which drain their contents
into the groove.
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Foliate Papillae
Observe the surface of the tongue. Youll see a series
of parallel ridges and furrows, the foliate papillae.
They are located at the dorsolateral surface of the
tongue.
Fungiform Papillae
Observe the surface of the tongue. Youll find a
mushroom-like structure, the fungiform papillae,
bulging above the tongue surface. Next to this
structure are situated rows of filiform papillae, which
have an elongated, conical structure. Its upper
surface contains scattered taste buds.
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Lingual Tonsil
At the base of the tongue youll see clusters of
solitary lymphnodules. It is covered by stratified
squamous epithelium.
Palatine Tonsil
Located at the lateral walls of the oropharynx,
youll find a pair of lymphoid organs, the palatine
tonsils. They are lined with a squamous stratified
epithelium, that often becomes so densely
infiltrated by lymphocyres that it may be difficultto recognize the real feature of this epithelium.
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The Esophagus
This photomicrograph is from the lower third of the
esophagus. It is lined with stratified squamous
epithelium. The muscularis mucosae is very thick.
The muscular layer, the muscularis externa,
consists of smooth muscle cells. The muscularisexterna of the mid portion of the esophagus
consists of a mixture of striated and smooth
muscle cells. In the upper part of the esophagus, it
is striated muscle.
Esophageal-cardiac junction
Observe the epithelial lining. At the esophageal-
cardiac junction, the epithelium from the
esophagus, stratified squamous epithelium, is
directly transformed into epithelium of the
stomach, simple columnar epithelium.
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Layers of GI tract
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Stomach
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Fundus
Gaster
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The stomach, a dilated segment of the digestive
tract, is divided into 4 regions: cardia, fundus,
corpus, and pylorus. The fundus and corpus are
identical in microscopic structure.
This photomicrograph is of the fundus gaster. The
simple columnar surface epithelium is invaginatedto form gastric pits (foveola gastrica). These pits
extent to 1/5 of the mucosa thickness into the
lamina propria.
Cells of the surface epithelium secrete an alkaline
mucus, forming a thick gel layer, that protects
them from the strong acid.
At the base of the gastric pits open several
branched tubular gastric (fundic) glands. The neck
of the gland consists of stem, mucous neck and
parietal (oxyntic) cells. The base of the gland
contains parietal, zymogenic (chief) and
enteroendocrine cells.
Note the large acidophilic cells; these are the
parietal cells of the fundus gaster, which secrete
HCl and an intrinsic factor for the absorption ofvit. B12
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Pilorus gaster
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LABORATORY 2
Identify the histological characteristic
appearance of the gastrointestinal tract from
the stomach to the recto-anal junction, ie.
duodenum, jejunum, ileum, colon, appendix,and recto-anal junction.
Identify histological features of small and large
intestines.
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Pylorus gaster.
The surface epithelium form deep gastric pits,
reaching of the mucosa thickness.
The glands are short and coiled, consisting of mucus
secreting cells.
Gastrin (G) cells which release gastrin, are intercalated
among the mucous cells. Gastrin stimulates the
secretion of acid (HCl) by the parietal cells
Enteroendocrine (D ) cells secrete somatostatin, which
inhibits the release of other hormones, including
gastrin.
The Small Intestine
The lining of the small intestine shows a series of
permanent folds, plicae circulares (Kerckring),
consisting of mucosa and submucosa, having a
semilunar, circular or spiral form. Besides that there
are outgrowth of the mucosa, forming intestinal villi,
consisting of epithelium and lamina propria.
This photomicrograph shows many cross-sections of
intestinal villi; plica is not seen here. These cross-
sections consist of absorptive, tall columnar cells ,
interspersed with mucus-secreting goblet cells , and
lamina propria.
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The duodenum
In the duodenum, the intestinal villi are leaf-
shaped. Plica Kerckring, if any, is very short.
In the submucosa are clusters of coiled, tubular
glands, Brunners gland. They may extent intothe lamina propria. Their cells are of mucous
type; their product is alkaline and acts to
protect the duodenal mucous membrane
against the effects of acid gastric juice.
Jejunum
In this segment of the digestive tract, the plicae
circulares Kerckring are the most developed,
containing many intestinal villi.
At the basal portion of the intestinal glands (also
called crypts of Lieberkhn), are exocrine cellswith large eosinophilic granules in their apical
cytoplasm; these are the Paneth cells. The
granules contain lysozyme, with antibacterial
activity.
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Ileum
This segment of the digestive tract containsintestinal villi, sometimes part of a plicaKerckring.
In the lamina propria and submucosa areaggregates of lymphoid nodules known as Peyers
patches (plaque Peyer). Each patch contains 10 to 200 nodules and is
visible to the naked eye as oval areas on the anti-mesenteric side of the intestine; they are devoidof villi. There are about 30 patches in the human.
Instead of absorptive cells, its coveringepithelium consists of M cells.
Colon
The colon, or large intestine, consists of a mucousmembrane with no folds or villi.
The intestinal glands are long and characterizedby a great abundance of goblet and absorptivecells, and a small number of enteroendocrine
cells. The muscularis layer have fibers of theouter longitudinal layer congregated into 3 thicklongitudinal bands called teniae coli.
In the anal region the mucous membrane forms aseries of longitudinal folds, the rectal columns ofMorgagni.
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Appendix
The appendix, an evagination of the cecum, ischaracterized by a relatively small, narrow, andirregular lumen, that is caused by the presence ofabundant lymphoid follicles in its wall.
It contains fewer and shorter intestinal glandsand has no villi or teniae coli.
The recto-anal junction
About 2 cm above the anal opening, theintestinal mucosa lining from simple columnar(rectum) is gradually replaced by stratifiedsquamous epithelium (anal eepithelium).
In this region the lamina propria contains aplexus of large veins that, excessively dilated andvaricose, produce hemorrhoid.
The muscular layer is not complete, because onlythe circular layer persists, its end forming theinternal sphincter ani muscle.
Surrounding the internal sphincter ani muscle isthe external sphincter ani muscle, consisting ofclusters of striated muscle fibers.
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LABORATORY 3
Identify the essential histological features of
the salivary glands and the liver, with special
reference to the organization of parenchyma
and stroma.
Identify the organization of the bile canaliculi,
space of Disse, liver sinusoid and Kupffer cells.
Identify the histology and vascular relations of
a classic hepatic lobule.
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Parotid Gland
It is a branched acinar gland; its excretoryportion is composed exclusively of serous cells.
As in other large salivary glands, the connectivetissue contains many plasma cells andlymphocutes. The plasma cells secrete IgA which
forms a complex with a secretory componentsynthesized by the serous acinar, intercalatedduct, and striated duct (intralobular duct) cells.This complex constitutes an immunologicdefence mechanism against pathogens in theoral cavity.
Submandibular (submaxillary) Gland
It is a branched tubuloacinar gland; its secretoryportion contains both mucous and serous cells.The serous cells are the main component of thisgland (90%).
The presence of extensive lateral and basal
membrane infoldings toward the vascular bedincreases the ion-transporting surface area 60times. Because of this, the cell boundaries areindistinct.
The cells that form the demilunes secrete theenzyme lysozyme, which main activity is tohydrolyze the walls of certain bacteria.
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Sublingual Gland
Like the submandibular gland, this gland is a
branched tubuloacinar gland formed of serous and
mucous cells. Mucous cells predominate in this
gland; serous cells are present exclusively on
demilunes of mucous tubules.
As in the submandibular gland, cells that form the
demilunes in this gland secrete lysozyme.
The duct system of the salivary glands are
intercalated ducts (lined by squamous to low
cuboidal cells), striated (intralobular) ducts (lined
by cuboidal cells with a lot of cytoplasm), and
larger interlobular ducts (lined by striated or
columnar cells around a large lumen).
In this photomicrograph is shown interlobularducts, with its large lumen, surrounded by
connective tissue.
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Liver
The liver is the organ in which nutrients absorbed
in the digestive tract are processed and stored for
use.
Most of its blood (70-80%) comes from the portal
vein; the smaller percentage is supplied by thehepatic artery.
In light microscopic sections, structural units
called liver lobules can be seen. In certain animals,
eg pigs, the lobules are separated from each
other by a layer of connective tissue. This is not
the case in humans.
In the lobule, the hepatocytes are radially
disposed in plates, directed from its periphery to
its center. The space between those plates
contains capillaries, the liver sinusoids.
In addition to the endothelial cells, the sinusoids
contain macrophages known as Kupffer cells, on
the luminal surface of the endothelial cells. Their
main functions are to metabolize aged
erythrocytes, digest hemoglobin, secrete proteinsrelated to immunologic processes and destroy
bacteria that enter blood through the large
intestine.
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LABORATORY 4
Identify the microscopic structure of the
pancreatic gland, the exocrine and the
endocrine portion of the gland.
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Pancreas
It is a mixed exocrine-endocrine gland that
produces digestive enzymes and hormones.
The enzymes are stored and released by cells of
the exocrine portion, arranged in acini. The
hormones are synthesized in clusters of endocrineepithelial cells, known as islets of Langerhans.
The exocrine portion of the pancreas is similar in
structure to the parotid gland (serous cells).
The distinction between the two glands can be
made based on the absence of striated ducts and
the presence of islets of Langerhans in pancreas.
Another characteristic detail is that in the
pancreas the initial portion of intercalated ducts
penetrate the lumen of the acini.
Nuclei, surrounded by a pale cytoplasm, belong to
the so called centroacinar cells, that constitute the
intra-acinar portion of the intercalated duct.
Intercalated ducts are tributaries of largerinterlobular ducts lined by columnar epithelium.
There are no striated ducts in the pancreatic duct
system.
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