Histology - Digestive System

Front 1

Basic Layers of Tubular Organs (GIT)

Back 1

Basic Layers of Tubular Organs (GIT):

*Inside to Outside

1.) Mucosa
*Most glands in this layer
a.) Epithelium (simple columnar)
b.) Lamina Propria (CT)
-lymph, vessels, etc
c.) Muscularis Mucosa
-thin & weak
-local movement (NOT peristalsis), facilitates mixing/absorption

2.) Submucosa
-loose CT (denser than in mucosa layer)
-Meissner's Plexus (aka Submucosal Plexus)

3.) Muscularis Externis
*Peristalsis
-Circular Muscle (inner)
-Auerbach's Plexus (aka Myenteric Plexus)
-Longitudinal Muscle (outer)

4.) Serosa (free-hanging parts)
-Adventitia for: upper esophagus, sigmoid colon

Front 2

Tongue Papillae

Back 2

Taste Papillae:

1.) Filliform Papillae
-keratinized epithelium
-everywhere
-doesn't actually have tastebuds

2.) Circumvillate Papillae
-non-keratinized epithelium
-7-12 in adult humans
-lined up at back of the tongue anterior to sulcus
-have Von Ebner glands at base

3.) Fungiform Papillae
-keratinized squamous epithelim
-(not as strong as filliform)
-scattered
4.) Foliate Papillae
-rare in adult humans
-lateral sides of the tongue

*All have tastebuds, except filliform

Front 3

Zones of the Stomach

Back 3

Zones of the Stomach:

1.) Cardia - immediately around the opening
2.) Fundus - upper, rounded part
3.) Corpus - majority of the stomach
4.) Pylorus - funnel shaped portion, exit

*Histologically 3 zones, b/c Cardia & Fundus look the same

Front 4

Rugae

Back 4

Rugae:

Folds in the stomach
(mucosal & submucosal layers)

Front 5

Chief Cells

Back 5

Chief Cells (Exocrine):

-Pepsinogen
-Gastric Lipase

-base of Gastric Glands
-bluer in appearance

Front 6

Entereocrhomaffin Cells

Back 6

Enterochromaffin Cells (Endocrine)

-Histamine
(stimulates gastric acid secretion)

-Neck of Gastric Glands

Front 7

Enteroendocrine Cells (G cells)

Back 7

Enteroendocrine Cells (G cells) [Endocrine]:

-Gastrin
(stimulates Gastric Acid Secretion)

-Neck of Gastric Glands

Front 8

Parietal Cells

Back 8

Parietal Cells:

-HCl (Gastric Acid)
-Intrinsic Factor

*Neck & Fundus of Gastric Glands
*High in Mitochondria for secreting H+

Front 9

Mucous Neck Cell

Back 9

Mucous Neck Cell (Exocrine):

-Mucous
-Bicarbonate

Front 10

D Cells

Back 10

D Cells (Endocrine):

-Somatostatin
(inhibits gastric acid secretion)

Front 11

Stomach Layers

Back 11

Stomach Layers:

-Same as basic layers for tubular organs, except...

*Muscularis Externa has extra layer: Oblique Muscle (internal to circular layer)

Front 12

Intestinal Surface Area

Back 12

Intestinal Surface Area:

1.) Plicae Circularis - 3x increase, 3x total

2.) Villi - 10x increase, 30x total

3.) Microvilli - 20x increase, 600x total

Front 13

Crypts of Lieberkühn

Back 13

Crypts of Lieberkühn (Intestinal Glands):

-Small Intestine, between intestinal villi
-simple tubular (short)
-Mechanism: ?
-Secrete: mucous, water, electrolytes
*NOT digestive enzymes

Paneth Cells (base): antimicrobial
Goblet Cells

Front 14

Paneth Cells

Back 14

Paneth Cells:

-base of intestinal glands
-secrete lysozome, antimicrobial
-acidophilic
-secretory granules

Front 15

Small Intestine: Regional Characteristics

Back 15

Small Intestine: Regional Characteristics

1.) Duodenum
-Brunner's Glands (submucosa)

2.) Jejunum
-most developed plicae circulares

3.) Ileum
-Peyer's patch
*aggregate lymphoid tissue
(*note: some is found everywhere, here aggregated)
*M (microfold) cells - randomly sample antigens from the lumen & transport to dendritic cells

Front 16

Large Intestine: Unique Features

Back 16

Large Intestine: Unique Features

1.) Taenia Coli - longitudinal muscle gathered into 3 "bunches"

2.) No folds - BUT, intestinal glands can be confused for folds
-Trick: imagine a line across tops
-straight = itestinal glands (indented from a flat surface)
-crooked = folds (SI) (protrusions)

Front 17

Anal Canal

Back 17

Anal Canal:

-Colorectal Zone
-simple columnar epithelium

-Anal Transitional Zone
-change toward stratified squamous epithelium

-Squamous Zone
-keratinized stratified squamous epithelium

Front 18

Appendix

Back 18

Appendix:

Differences from Colon Histology:
1.) Fewer Glands/Crypts
2.) No Taenia Coli
3.) Mucosa & Submucosa full of lymph nodules