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