DIGESTIVE SYSTEMDIGESTIVE SYSTEM

3 major components:3 major components:

1.1. Oral cavity.Oral cavity.

2.2. Alimentary canal.Alimentary canal.

3.3. Associated Glands:Associated Glands:• Salivary glands.Salivary glands.

• Liver.Liver.

• Pancreas.Pancreas.

Wall of the Alimentary CanalWall of the Alimentary Canal

Four concentric layers:Four concentric layers:

1.1.MucosaMucosa::– Epithelial Lining:Epithelial Lining:

• Simple columnar Simple columnar epithelium (in stomach & epithelium (in stomach & intestine).intestine).

– Lamina propria:Lamina propria:• Connective tissue.Connective tissue.• It contains mucosal glands.It contains mucosal glands.

– Muscularis mucosae:Muscularis mucosae:• 2 layers of smooth muscle 2 layers of smooth muscle

cells.cells.

Serosa

Wall of the Alimentary CanalWall of the Alimentary Canal

2.2. Submucosa:Submucosa:Connective tissue containing Connective tissue containing blood vessels & nerves. May blood vessels & nerves. May contain glands (as in contain glands (as in duodenum).duodenum).

3.3. Muscularis Externa:Muscularis Externa:2 smooth muscle layers:2 smooth muscle layers:

• Inner circular layer.Inner circular layer.• Outer longitudinal layer.Outer longitudinal layer.

4.4. Serosa:Serosa:Connective tissue covered by Connective tissue covered by mesothelium (simple squamous mesothelium (simple squamous epithelium).epithelium).

Serosa

STOMACHSTOMACH

It has 4 regions: It has 4 regions: cardiacardia, , fundusfundus, , bodybody and and pyloruspylorus..

fundus

body

pylorus

cardia

Fundus of StomachFundus of Stomach

Mucosa:Mucosa:

Shows Shows gastric pitsgastric pits in which in which open the open the fundic glandsfundic glands..

–Epithelial lining:Epithelial lining: simple simple columnar epithelium columnar epithelium ((mucus-mucus-secreting).secreting).NO goblet cellsNO goblet cells..

–Lamina propria: Lamina propria: Connective Connective tissue containing numerous tissue containing numerous fundic glandsfundic glands..

–Muscularis mucosae: Muscularis mucosae: 2 2 layers of smooth muscle.layers of smooth muscle.

Fundus of StomachFundus of Stomach Submucosa:Submucosa:

– Connective tissue containing Connective tissue containing blood vessels & nerves.blood vessels & nerves.

– NO glandsNO glands..

Muscularis Externa:Muscularis Externa:– 3 smooth muscle layers:3 smooth muscle layers:

• Inner oblique.Inner oblique.• Middle circular.Middle circular.• Outer longitudinal.Outer longitudinal.

Serosa:Serosa:– Connective tissue covered by Connective tissue covered by

mesothelium.mesothelium.

Fundic GlandsFundic Glands

Simple branched Simple branched tubular glands.tubular glands.

Have short narrow Have short narrow ducts (pits).ducts (pits).

Numerous; Numerous; occupying most of occupying most of the lamina propria.the lamina propria.

Perpendicular to Perpendicular to the surface. the surface.

Fundic GlandsFundic Glands

Composed of 5 cell types:Composed of 5 cell types:

1.1. Parietal cells: Parietal cells: secrete secrete HClHCl and and gastric intrinsic factor gastric intrinsic factor that that helps absorption of vitamin Bhelps absorption of vitamin B1212..

2.2. Peptic (chief) cells:Peptic (chief) cells:secrete secrete pepsinpepsin..

3.3. Mucous neck cells:Mucous neck cells:secrete secrete mucusmucus..

4.4. Enteroendocrine cells:Enteroendocrine cells:secrete secrete hormoneshormones..

5.5. Stem cells: Stem cells: regenerativeregenerative cells. cells.

SMALL INTESTINESMALL INTESTINE It has 3 regions: It has 3 regions:

duodenum, jejunum and duodenum, jejunum and ileum.ileum.

To increase surface area To increase surface area the mucosa has:the mucosa has:– Villi.Villi.– Crypts (intestinal glands).Crypts (intestinal glands).

DuodenumDuodenum

1.1. Mucosa:Mucosa:Shows Shows villivilli and and cryptscrypts..–Epithelium:Epithelium: simple simple columnar epithelium columnar epithelium with goblet cellswith goblet cells..–Lamina propria: Lamina propria: Connective tissue Connective tissue containing containing intestinal intestinal glands (crypts)glands (crypts)..–Muscularis mucosae: Muscularis mucosae: 2 2 layers of smooth muscle layers of smooth muscle cells.cells.

DuodenumDuodenum2.2. Submucosa:Submucosa:

– Connective tissue Connective tissue containing blood vessels containing blood vessels and nerves.and nerves.

– Contains Contains Brunner’s Brunner’s glandsglands (secrete mucus). (secrete mucus).

3.3. Muscularis Externa:Muscularis Externa:– 2 smooth muscle layers:2 smooth muscle layers:

• Inner circular layer.Inner circular layer.• Outer longitudinal layer.Outer longitudinal layer.

4.4. Serosa:Serosa:– Connective tissue Connective tissue

covered by mesothelium.covered by mesothelium.

Intestinal Glands (Crypts)Intestinal Glands (Crypts) Simple tubular glands Simple tubular glands

that open between villi.that open between villi. Composed of 5 cell types:Composed of 5 cell types:

1.1. Columnar cells: Columnar cells: absorptiveabsorptive..

2.2. Goblet cells: Goblet cells: secrete secrete mucusmucus..

3.3. Paneth cells: Paneth cells: secrete secrete lysozymelysozyme (antibacterial). (antibacterial).

4.4. Enteroendocrine cells: Enteroendocrine cells: secrete secrete hormoneshormones..

5.5. Stem cells: Stem cells: regenerativeregenerative cells.cells.

LARGE INTESTINELARGE INTESTINE

It is composed of:It is composed of:– Appendix,Appendix,– Cecum,Cecum,– Colon (ascending, transverse, Colon (ascending, transverse,

descending & sigmoid),descending & sigmoid),– Rectum, andRectum, and– Anal canal.Anal canal.

ColonColon1.1. Mucosa:Mucosa:

Shows Shows onlyonly cryptscrypts ((NO villiNO villi))–Epithelium:Epithelium: simple columnar simple columnar epitheliumepithelium with with numerous numerous goblet cellsgoblet cells..–Lamina propria: Lamina propria: Connective Connective tissue containing numerous tissue containing numerous cryptscrypts.. Cells of the crypts are Cells of the crypts are the same as in small intestine the same as in small intestine but but NO Paneth cellsNO Paneth cells..Lymphatic nodulesLymphatic nodules:: frequent.frequent.–Muscularis mucosae:Muscularis mucosae:2 layers of smooth muscle.2 layers of smooth muscle.

ColonColon

2.2. Submucosa:Submucosa:– NO glandsNO glands..

3.3. Muscularis Externa:Muscularis Externa:– Inner circular & outer Inner circular & outer

longitudinal smooth muscle longitudinal smooth muscle layers.layers.

– The longitudinal layer is not The longitudinal layer is not continuous but in the form of 3 continuous but in the form of 3 ribbons (ribbons (teniae coliteniae coli).).

4.4. Serosa:Serosa:– C.T. covered by mesothelium.C.T. covered by mesothelium.– Has fat-filled pouches called Has fat-filled pouches called

appendices epiploicaeappendices epiploicae..

PRACTICAL SLIDESPRACTICAL SLIDES

Fundus of StomachFundus of Stomach

DuodenumDuodenum

ColonColon

ColonColonDuodenumDuodenumFundusFundus

of Stomachof Stomach