Large Intestine

Large Intestine

Large Intestine

The large intestine is the final section of the gastrointestinal tract.
The large intestine is about 1.5 m in length and 6-7 cm in diameter in the living body.
Functions:
Absorption water
Formation of faecal mass
Production of mucus

Large Intestine

The large intestine formed of the following organs:

Cecum

Appendix
Colon
Rectum
Anal canal

Large Intestine

• The wall of Large Intestine consists of 4 layers:
• Mucosa
• Submucosa
• Muscularis Externa
• Serosa

Large Intestine

Mucosa
• The thick mucosa has deep intestinal glands , but there are no villi.

Consists of:

• 1- Epithelium : simple columnar epithelium and GOBLET CELLS
• 2-Lamina propria: Ioose connective tissue(INTESTINAL GLANDS)
• 3-muscularis mucosae: smooth muscle (inner circular and outer longitudinal layers).
• .

Large Intestine

• Submucosa:
• the dense connective tissue
• Muscularis Externa:
• consists of 2 substantial layers of smooth muscle.
• Inner circular layer :
• Outer longitudinal layer:
• Serosa :
• Loose connective tissue covered by a mesothelium.


INTESTINAL GLANDS

The intestinal glands: are simple tubular glands.

Types the cells in the intestinal glands:
columnar absorptive cells (absorb water)
goblet cells (unicellular mucous glands) their secretion serving to lubricate the lumen to facilitate waste elimination.
Stem cells
enteroendocrine cells
*****No Paneth cells.

Colon

Mucosa
Epithelium :
Lamina propria:
Intestinal gland: deep
Muscularis mucosae: prominent

Submucosa:

Muscularis externa :

Inner circular
Outer longitudinal : taeniae coli: (three bands of muscle)


Serosa

taeniae coli

APPENDIX :
Few short intestinal glands
Mucosa
Epithelium:Goblet cells- few
Lamina Propria:
Appearance Solitary Lymphatic nodules

Muscularis mucosae: disrupted

Submucosa:

.Muscularis externa:

Serosa

Anal canal (upper part)

Recto anal junction

Epithelium : non-keratinized stratified

squamous

Intestinal glands absent

Lamina propria & Submucosa: No distinction

• appears haemorrhoidal plexus (are dilated veins in the anal canal).

Muscularis mucosa: Absent

Muscularis externa :

• Inner circular (Thicken ): internal anal sphincter (smooth muscle) Outer longitudinal (Thicken ): external anal sphincter (skeletal muscle)

ANAL CANAL (lower part)

Mucosa :
Epithelium: keratinized Stratified squamous
Anal glands:
Sweat glands
Sebaceous glands
•

Large Intestine features

lacks villi

Intestinal glands are deeper

glands lack Paneth cells in their bases

more goblet cells in the epithelium

lamina propria contains solitary lymphatic nodules,(appendix)

m. externae has a unique arrangement: inner circular muscle layer present, outer longitudinal layer is arranged into 3 longitudinal muscle strips = taeniae coli