Morphology and histology of the and

János Hanics M.D. Anatomy of the and Duodenojejunal flexure Ileocoecal junction

Bauchin - valve Jejunum and ileum are intraperitoneal organs The is the largest of the human body. Derives from lateral plates of mesoderm. It has two layers: 1. parietal peritoneum 2. visceral peritoneum They have a continuous mesothelial layer

Abdominal and pelvic organs and structures – according to their peritoneal relations - can be divided into 2 main groups:

Intraperitoneal - covered by peritoneum and generally they have a duplication

Extraperitoneal (not surrounded by the peritoneum) within this: - Praeperitoneal - Retroperitoneal (secunder and primary) - Infraperitoneal structures. Duplication = meso- !!!! 1 4

3 2

5 1. 2. 3. Duodenum 4. Pancreas 5. Jejunum, ileum Mesentery (root of mesentery) mesenterial

antimesenterial Development

Ventral mesentery Dorsal mesentery Unpaired visceral branches of the abdominal Branches of the sup. mes. a. System of the portal vein

Cysterna chyli and thoracic duct Innervation: parasympathetic (vagus) and sympathetic Tunica mucosa Histology of the small interstine - (E)Epithelium (simple cuboideal) - (LPM) mucosae - (LMM)Lamina

Tela Tunica muscularis - Circular layer (inner) - Myenteric plexus (Auerbachi) - Longitudinal layer (outer) Tela Tunica serosa (mesothelium) - (Kerckring’s) - Intersinal villi - Microvilli (3000/cell) Longitudinal section – circular folds (plicae circulares=Kerckring’s folds) Interstinal villi

Lieberkühn -crypts Intersinal villus

In LPM

MALT (GALT) Enterocyte Lieberkühn-crypts (interstinal glands) Cells in the wall of Lieberkühn-crypts (interstinal glands)

Lysozyme production Regeneration Duodenum Jejunum Ileum Tunica mucosa Tela submucosa!!! Brunner’s glands (FLA) Peyer’s patches (antimesenterial margin!!!)

Tunica muscularis Tela subserosa Tunica serosa Jejunum

Duodenum Ileum (FLA) Folliculi lymphatici aggregati – Peyer’s patches

FLA Tunica muscularis (myenteric plexus of Auerbach Thank You for Your attention!