Histology of the Hepatopancreatico-biliary

1. HISTOLOGY OF GIT &
HEPATOPANCREATICO-
BILIARY SYSTEM

2. Content
 Introduction
 General Structure
 Histology of:
 Oral Cavity
 Esophagus
 Stomach
 Small Intestine
 Large Intestine
 Appendix
 Salivary Gland
 Liver
 Gall Bladder
 Pancreas
 MedicalApplication
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3. Introduction Gastrointestinal Tract
Digestive Tracts
Oral Cavity
Esophagus
Stomach
Small & Large Intestines
Rectum
Anus
Associated Glands
Salivary Glands
Liver
Gall Bladder
Pancreas
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4. General Structure of Digestive Tract
 Common Characteristics:
o Hollow tube composed of a lumen whose diameter
varies.
o Surrounded by a wall made up of 4 principal layers:
• Mucosa
oEpithelial lining; A lamina propria of loose
connective tissues rich in blood, lymph vessels
and smooth muscle cells; Muscularis mucosae.
• Submucosa
oDense connective tissues with many blood and
lymph vessels.
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5. General Structure of Digestive Tract
• Muscularis
oContains smooth muscle cells, divide into 2 layers;
internal (circular); external (longitudinal)
• Serosa
oThin layer of loose connective tissue rich in
blood and lymph vessels and adipose and single
squamous covering epithelium (mesothelium)
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6. 6

7. Oral Cavity
Stratified Squamous Epithelium
Keratinized
Protects Oral Mucosa
from damage during
masticatory function.
In Gingiva and Hard
Palate
Lamina Propria has
several papillae and rest
directly on bony tissue
Non Keratinized
Covers soft palate, lips,
cheeks and floor of mouth
Lamina Propria has
Papillae, similar to those in
dermis of skin and
continuous with
submucosa containing
diffuse small salivary
gland
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8. Oral Cavity
• Tongue
o Papillae
• Filiform
• Fungiform
• Foliate
• Circumvallate
• Pharynx
• Teeth and Associate Structures
o Dentin
o Enamel
o Pulp
o Periodontium 8

9. Tongue
 Mass of striated muscle covered by a mucous membrane.
 Muscle fibers cross on another in 3 planes, they are grouped in
bundles, usually separated by connective tissue.
 Dorsal Surface: Irregular; Thicker epithelium; Covered
anteriorly by a great number of small eminences papillae;
Separated from anterior two thirds by a V-shaped boundary.
 Ventral Surface: Epithelium on this surface is thinner.
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10. Tongue
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11. Papillae of Tongue
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12. Papillae of Tongue
 Filiform Papillae
o Conical Shape
o Numerous and present over entire surface of tongue
o Their epithelium does not contain taste bud and is
Keratinized.
 Fungiform Papillae
o Resemble mushrooms (narrow stalk and smooth surface,
dilated upper part)
o Contain scattered taste buds on upper surfaces
o Irregularly interspersed among filiform papillae.
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13. Papillae of Tongue
 Foliate Papillae
o Poorly developed in humans
o 2 or more parallel ridges and furrows on the
dorsolateral surface of tongue
o Contain many taste buds
 Circumvallate Papillae
o 7 – 12 extremely large circular papillae whose flattened surface
extend above other papillae (Papillae surrounded by deep
circular furrows).
o Distribute in the V region at the junction of the anterior
2/3rd and posterior 1/3rd of tongue.
o The epithelium is smooth on the lateral surface of papillae
o Great number of taste buds present along sides of these papillae.
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14. Papillae of Tongue
 Taste Buds
o Onion shaped structures containing 50 – 100 cells.
o Rests in Basal Lamina
o Apical portion project microvilli that poke through an
opening called taste pore.
o 2types of cells are distinguished in relation to tastebuds
• Supporting or sustentacular cells
• Neuroepithelial or gustatory cells
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15. 15

16. Taste Bud
 SUSTENTACULAR OR SUPPORTING CELLS
o Arranged peripherally, curved course, narrow at each end
and broader in the centre appearing spindle shaped.
o At both ends the cells surround small openings known as external
and internal pores.
 NEUROEPITHELIAL OR GUSTATORY CELLS
o Distributed between the sustentacular cells long narrow,
having slender red shaped form with a nucleus in the
middle.
o On the free surface, these cells gives rise to short hair which
project into the lumen of the pit.
o Substances to be tasted gets dissolved in the saliva, stimulate
the hairs in the neuroepithelial cells and the impulses is
conducted along the nerves (sweet, bitter, sour, salty)
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17. Pharynx
 Lined by Stratified non keratinized squamous epithelium
in region continuous with esophagus.
 Lined by ciliated pseudostratified columnar epithelium
containing goblet cells in region close to nasal cavity.
 Contains tonsils.
 Mucosa of pharynx also has many small mucous salivary
glands in its lamina propria
 Compose of dense connective tissues.
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18. Esophagus
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19. Esophagus
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20. 20

21. Stomach
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22. Stomach
 Mixed exocrine endocrine gland.
 Divides into 4 regions:
 Cardia
 Fundus
 Body
 Pylorus
 Fundus and body are identical in microscopic structure
 Mucosa and submucosa of undistended stomach lie in
longitudinally directed folds known as rugae.
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23. Gastric Mucosa
 Consists surface epithelium invaginating to various extent
into lamina propria forming gastric pits.
 Lamina propria of stomach composed of loose connective
tissue interspersed with smooth muscle and lymphoid cells.
 Muscularis mucosae to separate mucosa from underlying
submucosa
 Epithelium lining the pits and covering the surfaces are
simple columnar epithelium & all cells secrete alkaline
mucus.
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24. Gastro-esophageal Junction
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25. Stomach (Cardia)
 Mucosa contains simple or branched tubular cardiac glands
 Terminal portion of these glands are frequently coiled,
often with large lumens.
 Similar in structure to cardiac glands of the terminal portion
of esophagus.
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26. Stomach (Fundus & Body)
 Simple columnar surface epithelium extends into gastric pits into
which opens into gastric glands.
 Lamina propria consist of fine reticular and collagen fibres fills
the spaces between the packed gastric glands.
 Each gastric gland has 3 distinct region:
 Isthmus
 Neck
 Base
 Isthmus contains differentiating mucous cells and
undifferentiated stem cells and parietal cells.
 Neck consist of stem, mucous neck and parietal cells.
 Base contains parietal and chief (zymogenia) cells.
 Muscularis mucosa composed of inner circular and outer
longitudinal smooth muscle.
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27. Stomach (Fundus & Body)
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28. Stomach (Pylorus)
 Deep gastric pits into which the branched tubular pyloric
glands open.
 The epithelium of the mucous membrane consist of tall columnar
cells which lines the deep pits and short glands.
 Longer pits and shorter coiled secretory portion compare to
glands in cardiac region.
 The acini of pyloric glands and their ducts are in lamina
prorpia.
 G (Gastrin) cells are enteroendocrine cells intercalated
among mucous cells of pyloric glands.
 D cells secrete Somatostatin
 The muscularis externa is made up of thick circular muscle to
form pyloric sphincter which helps to control emptying of the
stomach. 28

29. 29

30. Small Intestine
Duodenum
Jejunum
Ileum
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31. Small Intestine
 4 layers:
 Mucosa
 Submucosa
 Muscularis externa
 Serosa
 Surface area of small intestine increased by
 Length of small intestine
 Valves of Kerkring/ Plica Circularis
 Villi
 Microvilli
 Cypts Of Lieberkuhn
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32. Mucosa of Small Intestine
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33. Valves of Kerkring
 Also known as Plica circulares
 Permanent submucosal circular folds
 Large, seen with naked eye
 Prominent in duodenum & jejunum
 Less marked in ileum
 Significance:
 Increases surface area
 Slow down the passage of contents
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34. Villi
 Central lacteal (lymphatic vessel)
 Core capillaries
 Core of connective tissue
 Epithelial cells – Tall columnar
with striated border
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35. 35

36. Crypt of Lieberkuhn (Intestinal gland)
 Invaginations of lining epithelium into lamina propria
 Wall of crypt is lined by the following cells:
 Columnar cells
 Goblet cells
 Undifferentiated stem cells
 Paneth / Zymogen cells
 Argentaffin cells
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37. Crypt of Lieberkuhn
 Absorptive columnar cells /
Enterocytes
 Microvilli which give it a
striated border appearance
 Goblet cells
 Secretes mucus
 Undifferentiated cells
 Actively multiply, move
upwards give rise to other
cells
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38. 38

39. Crypt of Lieberkuhn
 Paneth cells / Zymogen cells
o Seen in deeper parts of crypts
o Rrich in Zinc, secrete lysozyme that destroys bacteria
 Endocrine cells
o Seen near lower ends of crypts
o Argentaffin cells
o Entero-chromaffin cells
o APUD cells – secrete serotonin
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40. Submucosa of Small Intestine
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41. Brunner’s Gland
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42. Peyer’s Patches
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43. Differences between duodenum,
jejunum & ileum
Duodenum Jejunum Ileum
Epithelium Columnar Striated
border Few goblet
cells
Columnar
Striated border
goblet cells+
Columnar
goblet cells++
Villi Broad
Spatula Shaped
Closely packed
Tongue-shaped
Different heights
Few thin finger-
shaped
Lamina Propria Crypts+ No
Peyer’s
patches
Crypts+
Diffuse
infiltration of
lymphocytes
No Peyer’s
patches
Crypts+
Peyer’s patches
extend into
submucosa
Submucosa Mucus secreting
Brunner’s glands
Only connective
tissues and blood
vessels
Peyer’s patches
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44. Large Intestine
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45. Appendix
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46. Small Vs Large Intestine
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47. Histology ofAccessory Organs of GIT
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48. Salivary Gland
 3 pairs of salivary glands:
 PAROTID GLAND
o Purely serous (few mucous acini maybe present)
 SUBMANDIBULAR GLAND
o Mixed, Predominantly serous
 SUBLINGUAL GLAND
o Mixed, Predominantly mucous
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49. General Features
 Serous cells
 Pyramidal in shape
 Broad base resting on basal lamina
 Narrow apical surface with short irregular microvilli facing
lumen
 Secretory cells are joined together by junctional complex
and usually form spherical mass of cells called acinus
 Mucous Cells
 Usually cuboidal to columnar
 Oval nuclei pressed towards bases of the cells
 Most often organized as tubules, consisting of cylindrical
arrays of secretory cells surrounding a lumen.
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50. General Features
 Duct System
o Intralobular ducts
• Intercalated Ducts
oLined by Cuboidal Epithelial Cells
oAbility to differentiate into secretory or ductal
cells
• Striate Ducts
oRadial striations seen to consist infoldings of
basal plasma membrane with numerous
elongated mitochondria
oDrains into Interlobular Ducts
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51. General Features
 Interlobular Ducts (Excretory Ducts)
 Initially lined with pseudo stratified or stratified cuboidal
epithelium.
 Distal parts lined with stratified columnar epithelium
consisting few mucus secreting cells
 Ultimately empties into oral cavity and lined by
nonkeratinized-stratified squamous epithelium.
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52. Characteristics
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53. Liver
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54. Gall Bladder
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55. Pancreas
Mixed endocrine and exocrine gland
Exocrine: Compound acinar gland, similar in structure
to parotid gland.
Distinction between 2 glands can be made based on absence
of striated ducts and presence of islets of Langerhans.
Initial portions of intercalated ducts penetrate lumens
of acini.
 Centroacinar cells constitude interacinar portion of
intercalated duct.
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57. Application
 Gastroesophageal Reflux Disease associated with
incompetent barriers at gastroesophageal junction caused
by decrease in lower esophageal sphincter tone or hiatus
hernia. Reflux esophagitis develops when mucosal
defenses are not sufficient to protect esophageal mucosa
from acid, pepsin and bile.
 Stress, ingested aspirin, NSAID or ethanol can disrupt
epithelial layer in stomach lead to ulceration. Ulcer is
disruption of mucosal integrity leading to an excavation
due to active inflammation. Apirin and ethanol irritates
mucosa partly by reducing blood flow.
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