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
AppendixColon
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
MucosaEpithelium :
Lamina propria:
Intestinal gland: deep
Muscularis mucosae: prominent
Submucosa:
Muscularis externa :
Inner circularOuter 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 junctionEpithelium : non-keratinized stratified
squamousIntestinal glands absent
Lamina propria & Submucosa: No distinction• appears haemorrhoidal plexus (are dilated veins in the anal canal).
Muscularis mucosa: AbsentMuscularis 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 villiIntestinal glands are deeper
glands lack Paneth cells in their basesmore 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