Upload
others
View
9
Download
0
Embed Size (px)
Citation preview
HISTOLOGY & CELL BIOLOGY
Mr. BABATUNDE, D.E
GASTRO INTESTINAL TRACT II
Fundic Glands-Mucous Neck Cells
Located in neck region Shorter than surface
mucous cell do not exhibit
prominent mucous cap Nucleus tends to be
spherical rather than elongate
Secretes a soluble mucous compared to viscous
surface mucous,high in HCO3 and K+.
PGE2 play an important role in mucosa protection.
Mucus neck cells
Fundic Glands-Parietal
Called OXYNTIC CELLS Secrete HCl
and intrinsic factor Located in neck
among mucous neck cells Most numerous in upper and
middle sections Give glandular epithelium
beaded appearance. Large cells
often binucleate,
Parietal cell
Fundic Glands-Parietal Cell cont
EM shows extensive INTRACELLULAR CANALICULAR SYSTEM communicates with lumen of
fundic gland Numerous surface microvilli
project from canaliculi HCl produced in the lumen of the
intracellular caniculi Pernicious anemia: absence (achlorhydria) or loss
of parietal cells (ulcers) - inadequate intrinsic factor production - vitamin B12 not absorbed.
Gram negative anaeroboic bacterial overgrowth which bind to VitB12- intrinsic
Fundic Glands-Chief Cells
Typical protein-secreting cells Loacted in the deepest part of
fundic glands Cuboidal or low columnar Cells easily identified by intense
basophilia Basal RER and apical granules
responsible for basophilia and acidophilia
Secrete: pepsinogen a weak lipase
Fundic Glands-Enteroendocrines
Located at any level of gland small cells sit on basal lamina Cells hard to identify
but clear cytoplasm stands out in contrast to chief cells
EM shows small, membrane-limited granules. Produce gastrin, secretin,cholecystokinin Secrete products into lamina propria. Peptic ulcers: majority caused by Helicobacterium pylori destruction of mucus layer erosion of mucosa,
submucosa, muscularis, etc.
M- muscular wallSl- Necrotic sloughV- Vascular granulation tissueF- Fibrous granulation tissueSc- Fibrous scar
Chronic peptic ulcer.
Ulcer – extends throughout the thickness of mucosa Causes- an imbalance between Damaging factors and protectiveFactorsUnchecked- can erode through the wall3 main complication of chronic peptic ulcera) Perforationb) Haemorrhagec) Obstruction.
Pyloric Glands Located between fundus and
pylorus in pyloric antrum
Branched tubular glands coiled
Cells Similar to surface mucous
cells
neuroendocrine cells interspersed
Glands empty into deep gastric pits that occupy ½ the thickness
of the mucosa
Small Intestine
Longest component 6 meters
Three segments: DUODENUM- 25 cm long JEJENUM- 2.5 m long ILEUM- 3.5 m long
Functions Passage of unabsorbed material Hormone production Principal site of digestion & absorption
Enzymes are from pancreas bile from liver
Small Intestine-lining
Amplification of absorptive surface area by tissue & cell
specializations: PLICAE CIRCULARES
valves of Kerckring permanent transverse
folds that contain a core of submucosa
Each fold circularly arranged
extends around half to 2/3 of circumference of lumen
PLICAE CIRCULARES
Small Intestine -Villi
Epithelium --simple columnar
Finger-like; leaf-like projections
Core of villus consists of extension of lamina
propria network of fenestrated
capillaries beneath epithelium
Small Intestine –Villi cont. Lamina propria
contains blind ended lymphatic capillary
CENTRAL LACTEAL
Smooth muscle accompanies lacteal
MICROVILLI of enterocytes
are major amplification of luminal surface. Each cell has several thousand In LM give apical region of cell a striated appearance (or BRUSH)
Small Intestine
Intestinal glands CRYPTS of
LIEBERKUHN
Extends from Villous base to muscularis mucosae
Lined by single layer of epithelial cells-Columnar
Constantly renewed Cells slough into lumen
PC – Plicae circularisIG- Intestinal GlandMM- Muscularis MucosaeSM- Submucosa
Small Intestine-epithelium
simple columnar, consisting of:
1) undifferentiated stem cells stem cells in base of crypt;
capable of cell division differentiate into 4 cell types enterocytes, goblet cells &
enteroendocrine cells proceed to villus; Paneth cells remain in crypt
2) protein- (enzyme-) secreting Paneth cells
Small Intestine-Enterocytes
Enterocytes: Tall columnar cell
basal nucleus
Have striated border on luminal surface MICROVILLI
Secretes its own apical surface coat of glycoprotein enzyme- help in the chemical break down of food.
Enterocytes
Small Intestine-Goblet Cells
Unicellular gland Accumulation of mucin
granules apically
Basal cytoplasm full of RER Mucous is water-soluble Mucus secreted covers
glycocalyx Increase in number
from proximal to distal small intestine
Most numerous in terminal ileum
Helps in lubrication
Small Intestine-Paneth Cell Found in bases of mucosal
glands May be seen in colon as well
Basophilic basal cytoplasm Supranuclear Golgi Large apical secretory
granules very eosinophilic refractile Granules permit
identification of these cells
Small Intestine-Paneth Cell cont
Granules contain LYSOZYME
LYSOZYME digests cell walls of certain bacteria
Paneth cells probably Regulate of normal
bacterial flora of small intestine
Small Intestine-Enteroendocrines
Like those in stomach Secrete into lamina propria
Situated in lower part of crypts migrate and found at all
levels
Same hormones as in stomach increase liver & gall
bladder activity and decrease gastric
secretion
Small Intestine
Lamina propria surrounds glands
Lamina propria also contains lymphatic nodules
important part of GALT
Nodules are especially large in ileum called PEYER’S
PATCHES
Progressive changes: Duodenum -ileum
Duodenum-Distinguished by plicae
circularis (less than the jejunum)
-Long prominent villi(leaf like)
-fewer goblet cells-presence of
SUBMUCOSAL DOUDENAL GLANDS(OF BRUNNER)
JejunumLong prominent
villiMore number of
goblet cellsNo submucosal
glandsMore elaborate
Plicae circularis.
IleumShort villiGoblet cells increasePresence of large aggregates
of lymph nodules:Peyer’s patches(GALT)
Peyers patches – appear dome shaped when viewed from luminal surface
Epithelium covering peyers patches – M cells
Small Intestine-M cells
M Cells (Microfold cells) Epithelial cells that overlie
Peyer’s Patches and other lymphatic
nodules
Take up macromolecules from lumen by endocytosis vesicles transported
basally for exocytosis near
lymphocytes
CELIAC DISEASE(malabsorption syndrome)
Autoimmune diseaseHypersensitive to glutenWeight loss, anemia and steatorrheaInfiltration of inflammatory lymphocytes and plasma cellsLoss of villiHyperplasia(elongation) of cryptsFlat small bowel mucosaIncrease in intraepithelial lymphocytes
Large Intestine-Mucosa Contains numerous CRYPTS
OF LIEBERKUHN
Simple columnar epithelium Absorptive cells look like
those of small intestine primary function of
ABSORPTIVE CELLS
absorb water and electrolytes
Large Intestine-Mucosa cont
Goblet Cells Secrete much mucous
- Facilitates elimination of waste material
Undifferentiated cells No Paneth cells(exc
appendix)
Large Intestine-Muscularis (externa)
Outer layer
partly formed into dense bands called TENIAE COLI
- teniae pucker wall between into haustrae.
Appendix APPENDIX is a thin
finger-like extension of the CECUM. Appendix is different
in that it has a complete layer of longitudinal muscle in the muscularis
Conspicuously, large numbers of lymphatic nodules located in wall of
appendix also trash in lumen
Most common surgical emergencyEarliest change- a) Ulceration of mucosa-Ub) Overlying fibropurulent
inflammatory exudates-EXc) Pus within lumen- Pd) Vague central abdominal pain
Acute Appendicitis
Gangrenous appendicitisa) Continuing inflammation-
necrosis(Ne) of muscle layer(M)
b) Predisposes to perforation – peritonitis
c) Pus(P) may discharge into peritoneal cavity
d) No appropriate treatment – septicemia, shock &death
Large Intestine-Rectum & Anal canal
No teniae Rectum is dilated
Upper part notable by presence of folds TRANSVERSE
RECTAL FOLDS Anal canal
Upper part has longitudinal folds
Called ANAL COLUMNS Depressions
between anal columns called ANAL SINUSES
Mucosa like rest of colon
Distal anal canal linedwith stratified squamous epithelium
Continuous with that of skin
Anal Canal
Divided into three zones Colorectal zone- Found in upper third of anal canal and contains
simple columnar epithelium
Anal Transitional zone- Occupies middle two third. Represents transition between the simple columnar epithelium of rectal mucosa and stratified squamous epithelium of perianal skin
Squamous Zone-Found in lower third. lined
with stratified squamous epithelium
Continuous with that of skin
Acknowledgements
• Color Atlas of Histology, Leslie P. Gartner & James L. Hiatt - 3rd ed. 2000, Lippincott, Williams & Wilkins• Basic Histology, Luiz Junqueira & Jose
Carneiro – 10th ed. 2003, Lange Medical Books McGraw-Hill• Freeze-Etch Histology, Lelio Orci & Allain
Perrelet – 1975, Springer-Verlag Berlin Heidelberg• Fine Structure of Cells and Tissues, Keith R.
Porter & Mary A. Bonneville – 4th ed. 1973,Lea & Febiger