Digestive System Oral Cavity to Anal Canal

Zulham

Zukesti EffendiDepartment of Histology

Faculty of Medicine USU

• Oral Cavity

– Lip

– Palate

– Tongue

• Alimentary Canal

– Esophagus

– Stomach (Cardia, Fundus and Corpus, Pylorus)

– Small intestine (Duodenum, Jejunum, Ileum)

– Large Intestine (Appendix, Colon, Rectum, Anal Canal)

• Glands

– Salivary Gland

– Liver

– Gall bladder

– Pancreas

Lip

• 3 regions:

– External aspects

• is covered with thin skin

– Vermillion Zone

• The pink region of the lip

• is covered with thin skin, devoid sweat gland and hair follicles

– Mucous aspect

• is covered by stratified squamous non keratinized ep.

• Sub mucosa is composed of dense and loose connective

tissue. They have dense vascularization

• Muscle: skeletal muscle

Lip

Teeth

• Crown, cervix, root

• Mineralized: Enamel,

Dentin, Cementum

• Periodonsium: Gingiva,

Alveolus, Periodontal

ligament

• Pulp chamber: Connective

tissue, vascular, lymph,

nerve

Palate

• Composed of hard palate, soft palatae, and

uvula

• Hard palate is composed of str squamous

keratinized/parakeratinized ep, irregular

collagenous CT, and bony shelfcollagenous CT, and bony shelf

• Soft palate is composed of str squamous

nonkeratinized ep, dense irregular CT, minor

salivary glands, and bony shelf

• Uvula is composed of str squamous

nonkeratinized ep, areolar CT, muscle

Tongue

• Dorsal surface– Lingual papillae

• Filiform papillae– Str squamous keratinized ep

• Fungiform papillae • Foliate papillae (degenerate at 3 y old)• Foliate papillae (degenerate at 3 y old)• Circumvalate papillae

– Von Ebner glands produces lipase

• Intrinsic and extrinsic skeletal muscle

Papila filiformis

Papila foliate

Papila filiformis

Papila fungiformis

Papila

circumvallate

Taste Buds• Sensory organs, perception of

taste. (In fungiform and circumvalate papillae)

• Taste pore

• Oval structure, composed of 60 – 80 spindle-shaped cells, pale. Microvili protrudes from taste porepore

– Basal cells (type IV cells)

– Dark cells (type I cells)

– Light cells (type II cells)

– Intermediate cells (type III cells)

• Nerve fibers form synaptic junctions w/ type I, II, III cells

General Structure of Alimentary Canal

• Mucosa

– Epithelium

– Lamina proria (loose CT): glands, lymph vessel and nodules, richly vascularized

– Muscularis mucosae

• Submucosa

– Dense, irregular fibroelastic CT: glands (+) in oesophagus n duodenum

– Meissner’s submucosal plexus

• Muscularis Externa• Muscularis Externa

– Smooth muscle

– Auerbach’s myenteric plexus

• Serosa/adventitia

– Thin CT

• Serosa, if it is invested by peritoneum

• Adventitia, if it is retroperitoneal

Mucosa Submucosa

Muscularis externa

Serosa/Adventitisa

Innervation of the Digestive Tract

• Enteric Nervous System

– Meissner’s submucosal plexus

• Controlling secretory, mucosal movement, blood flow regulation

– Auerbach’s myenteric plexus

• Peristaltic Motility functions

• Parasympathetic and Sympathetic Nerve

– Parasympathetic

• Stimulates peristalsis; inhibits sphincter muscle; triggers secretion

– Sympathetic

• Inhibit peristalsis; activate sphincter muscles

Auerbach myenteric plexus

Esophagus• Mucosa

– Epithelium: Str squamous nonkeratinized ep,

– Lamina propria: esophageal cardiac glands

– Musc. Mucosa: single layer of longitudinally oriented smooth muscle

• Submucosa

– Esophageal glands

• Mucous cells• Mucous cells

• Serous cells: pepsinogen + lysozyme

• Muscularis externa

– 2 layers: inner circular; outer longitudinal

– 1/3 upper skeletal; 1/3 mid skeletal and smooth; 1/3 lower smooth

• Adventitia/Serosa

• F: conveys the bolus from oropharynx to stomach

Epithelium

Lamina Propria

Muscularis mucosae

Mucosa

Esophageal glands

Submucosa

Muscularis ExternaInner circular layer

Outer longitudinal layer

Gastroesophageal Junction

Stomach

• Mucosa

• Submucosa• Submucosa

• Muscularis Externa

• Serosa

Mucosa of Gaster• Epithelium: simple columnar ep

– Mucus layer/visible mucus; bicarbonate ion

– Gastric pit/Foveola gastrica

• Surface lining cells

• Regenerative/stem cells

• Lamina propria

– Loose, vascular >>>

– Houses gastric/fundic/oxyntic glands– Houses gastric/fundic/oxyntic glands

• Surface lining cells

• Mucous neck cells

• Regenerative (Stem) cells

• Parietal (Oxyntic) cells

• Chief (Zymogenic) Cells

• DNES Cells/APUD/Enteroendocrine/Argentaffin Cells

• Muscularis mucosae

– 3 layers: inner circular; outer longitudinal; outermost circular (occasionally)

Matched pair of light and electronmicrographs of serial sections through thestomach.A, Adventitia;C, Chief Cell;G, lumen of gastric pit;L, lumen of stomach;ME, Muscularis Externa;MM, Muscularis Mucosae;P, parietal cell;S, surface mucous cell;SUB, Submucosa;SUB, Submucosa;arrow, opening of gastric pit;*, lumen of Gastric Gland.1,100 X

Submucosa of gaster

– Dense, irregular CT

– Richly vascularized n lymphoid tissue

– Submucosal plexus

Muscularis externa of gaster

– Innermost oblique layer, middle circular layer, outer – Innermost oblique layer, middle circular layer, outer longitudinal muscle layer

– Myenteric plexus

Serosa of gaster

– Thin, lose CT covered by simple squamous ep

Distribution of Cell Type in Fundic Glands

REGION CELL TYPES

ISTHMUS Surface-lining cells and few DNES cellsISTHMUS Surface-lining cells and few DNES cells

NECK Mucous neck cells, Stem cells, parietal cells, and few DNES cells

BASE Chief cells, occasional parietal cells, and few DNES cells

Differences in Mucosa Cardiac and Pylorus

• Cardiac

– Gastric pit depth shallower

– Highly coiled glands

– Cell population: mostly surface-lining cell, some mucous neck cells, a few mucous neck cells, a few DNES and Parietal cell, but no chief cells

• Pylorus

– Gastric pit deeper

– Highly convoluted and tend to branch

– Same as cardiac; but mostly mucous neck cells

Surface Lining Cells

• Produced thick mucus layer• Apical cell

– Glycocalyx-covered, short,

stubby microvili

– Secretory granules

• Lateral cell– Zonula occludens n adherens

• Basally nucleus

Mucous Neck Cells

• Columnar, resemble surface-lining cells• Produce soluble mucus and lysozyme to

lubricate gastric contentslubricate gastric contents• Predominat in pyloric

Regenerative (Stem) Cells

• In the base of pits but more numeous in the neck

• Columnar• Columnar

• Have little heterochromatin and display large nucleolus

Parietal (Oxyntic) Cells

• Large, round to pyramid-shaped

• Mainly in upper half of fundic glands

• Produce HCl and gastric intrinsic factor

• Eosinophilic cytoplasm

• Invaginations apical plasmalemma to form intracellular canaliculi

• Tubulovesicular system

Chief (Zymogen) Cells• Columnar with basophilic

cytoplasm, basally located nuclei, apical secretory granules (pepsinogen)

• Rich RER, Golgi apparatus, but a few apparatus, but a few lysosomes

• Microvilli

• Secretion of pepsinogen is induced by both neural and hormonal, triggered by secretin binding to the receptor (in basal cell)

• Figure A. Electronmicrograph of gastricglands within the mousestomach.C, capillary,Ch, Chief Cell;E, enterochromaffin cell;LP, Lamina Propria;MM, MuscularisMucosae;P, parietal cell;RER, rough ER;S, Secretory Granules;S, Secretory Granules;*, lumen of GastricGland. 3,500 X

• Figure B. Chief Cell.5,600 X

• Figure C. Parietal cell.Ca,secretory canaliculus;M, mitochondrion;P, parietal cell.7,800 X 148

DNES/Argentaffin/APUD/Enteroendocrine Cells

• Releases secretory granules to lamina propria– Paracrine

– Endocrine

– Neurocrine

• 13 different secretory granules types

• 2 types• 2 types– Closed type

– Open type• Microvili → monitor luminal

contents

Small Intestine

Modifications of the Luminal Surface

• Plicae circulares (valves of Kerckring)

– Transverse folds of submucosa and mucosa that form – Transverse folds of submucosa and mucosa that form semicircular to helical elevations

• Vili

– Epithelially covered, finger-like or oak leaf-like protrusions of lamina propria

• Microvili

– Modifications of apical of intestinal epithelium cell membrane

• Intestinal Mucosa

– Epithelium: surface absorptive cells, Goblet Cells, DNES cells, M (microfold) cells

– Lamina propria

• Forms the core of villi

• Tubular glands (Crypts of Lieberkuhn): + Regenerative cells , Paneth cells

– Muscularis mucosae

• Inner circular layer; outer longitudinal layer

• Inner layer enter the villus and extend through its core

• Submucosa

– Dense, irregular fibroelastic CT; rich in lymph and vascular

• Muscularis Externa

– Inner circular, outer longitudinal smooth muscle

• Serosa

Specific Features of Small Intestine

• Duodenum

– Brunner’s (duodenal) glands in submucosa

• Jejunum

– Plicae circulares

• Ileum

– Peyer’s patch

Duodenum

JejunumJejunum

Ileum

Matched pair of light and electronmicrographs of serial sectionstaken through the duodenum.

BG, Brunner's Glands;

E, epithelium;

IG, Intestinal Glands;

L, Lacteal;

Lu, lumen of duodenum;

LP, Lamina Propria;

SUB, Submucosa;

V, Villus;

*, brush border.

Figure A, 550 X; Figure B, 675 X

Electron micrograph of longitudinal section through a Villus of the duodenum.

C, columnar absorptive cell; G, Goblet Cell; L, lymph capillary (Lacteal); LP, Lamina Propria; Lu, lumen of duodenum; N, nerve bundle; P, Plasma cell; blood capillary; arrow, brush border; dotted line, boundary between epithelium and Lamina Propria. 1,100 X

Electron micrograph of upper part of the Submucosa of the duodenum.

A, Arteriole; BG, Brunner's Glands; Co, Collagen fibrils; IG, Intestinal Glands (crypts of Lieberkuhn) at the base of the epithelium; L, lymph capillary; LP, Lamina Propria; N, nerve; *, blood capillary; dotted line, boundary between Lamina Propria and Submucosa. 1,300 X

Longitudinal section

through the tip of a Villus

in the jejunum.

BB, brush border; C, columnar

absorptive cell; G, Goblet Cell; L,

lumen of intestine; LP, Lamina

Propria; V, Villus; *, Smooth

Muscle Fiber; dotted line,

interface between epithelium

and Lamina Propria. 1,300 X

EM of the lower aspect of

the wall of the same

jejunum.

A, Arteriole; C, capillary; IG,

intestinal gland; La, lymph

vessel (Lacteal); LP, Lamina

Propria; ME, Muscularis Externa;

SUB, Submucosa; *, Smooth

Muscle fibers. 800 X

Matched pair of LM and EM of

serial longitudinal sections taken

through the lower half of the wall

of the jejunum.

A, Adventitia;

AP, Auerbach's plexus;

Ar, Arteriole;

C, capillary;

IC, inner circular layer of

muscularis externa;

IG, Intestinal Glands;

La, Lacteal;

LP, Lamina Propria; LP, Lamina Propria;

ME, Muscularis Externa;

OL, outer longitudinal layer of

muscularis externa,

SUB, Submucosa;

*, Smooth Muscle in wall of

Lacteal.

770 X

• EM of the simple Columnar Epitheliumlining a Villus of the ileum. C, columnar absorptive cell; BB, brush border; G, Goblet Cell; LP, Lamina Propria; L, lumen of ileum. 3,800 X

• EM of the same ileum showing the area beneath the intestinal surface. A, the intestinal surface. A, Arteriole; G, goblet cells; IC, inner circular layer of Muscularis Externa; IG, Intestinal Glands; L, lumen of intestinal gland; LP, Lamina Propria; M, dividing cell; ME, Muscularis Externa; OL, outer longitudinal layer; P, Paneth Cells; SUB, Submucosa. 1,300 X

Surface Absorptive Cells

• The most numerous

• Tall cell with basally located nucleus, brush

border (microvili), and cell junction

• For terminal digestion and absorptions of water • For terminal digestion and absorptions of water

and nutrients

Goblet Cells

• Unicellular glands

• Produced mucinogen

M (Microfold) Cells

• Squamous like cell above the lymphoid

nodule

• Important for defense mechanism

Paneth Cells

• Large, eosinophilic, apical secretory granules → lysozymegranules → lysozyme

• Pyramid-shape cell in bottom of crypts Lieberkuhn

Large Intestine

• Appendix

• Caecum and Colon• Caecum and Colon

• Rectum and Anal Canal

Appendix• Mucosa

– Epithelium: simple columnar

• Surface absorptive cells, goblet cells, M cells

– Lamina propria

• Loose CT

• Lymphoid nodules• Lymphoid nodules

• Shallow crypts of Lieberkuhn– Surface absorptive, goblet , regenerative, DNES, and Paneth Cells

• Submucosa, Muscularis externa, Serosa

• Stellate lumen that is filled by debris

Caecum and Colon

• Mucosa

– Epithelium: simple columnar

– Lamina propria

• Richly endowed crypths of Lieberkuhn

• No Paneth cells; surface absorptive cells >>>>> Goblet cells >>>, DNES >

• Submucosa

• Muscularis externa

– 2 layers: inner circular; outer longitudinal

– Outer longitudinal layer is not continous but is gathered into 3 fascicles: taenia coli

• Serosa

– Appendices epiploicae: fat-filled pouches

Taenia Coli

Matched pair of LM and EM of serial cross sections through colon. A, Arteriole; AP, Auerbach's plexus; C, columnar absorptive cell; G, Goblet Cell; IG, intestinal gland; L, lumen of colon; Lu, lumen of intestinal gland; LP, Lamina Propria; ME, Muscularis Externa; S, Muscularis Externa; S, artifactual space between Submucosa and Muscularis Externa; SUB, Submucosa; V, vein; *, Plasma cell; arrow, opening of intestinal gland; arrowheads, Smooth Muscle fibers of Muscularis Mucosae. 550 X

EM of the outer region of the wall of the colon.A, Arteriole; G, Goblet Cell; IG, intestinal gland; Lu, lumen of intestinal gland; LP, Lamina Propria; ME, Muscularis Externa; MM, Muscularis Mucosae; S, artifactual space S, artifactual space between Submucosa and Muscularis Externa; SM, Smooth Muscle in Arteriole wall; SUB, Submucosa. 1,900 X

Rectum

• Rectum resembles colon but the crypts of

Lieberkuhn are deeper and number fewer

per unit areaper unit area

Anal Canal• Mucosa

– Epithelium:

• simple cuboidal from rectum to pectinate line

• Str squamous nonkeratinized: from pectinate line to external anal orifice

• Str squamous keratinized: epidermis at anus

– Lamina propria houses anal glands (at rectoanal junction) and circumanal glands (distal end of anal canal)circumanal glands (distal end of anal canal)

• Submucosa

– Fibroelastic tissue houses 2 venous plexus: internal and external hemorrhoidal plexus

• Muscularis externa

– Inner circular layer becomes thickened at pectinate line to form internal anal sphincter muscle

– External anal sphicter muscle comes from pelvis

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