Anatomy of the Intes.ne: Epithelium, Lympha.cs, Vessels and Nerves

Transcription

1 Master Course Gastroenterology 2015 Anatomy of the Intes.ne: Epithelium, Lympha.cs, Vessels and Nerves Dr. Stephanie Ganal Department Klinische Forschung University of Bern

2 Dual funchon of the inteshne 1. DigesHon and uptake of nutrients 2. ProtecHon from invading pathogens 2

3 General structure 3

4 IntesHne overview 4

5 The small inteshne ca. 3 6 m long from pylorus to ileocecal valve 3 segments (proximaldistal) Duodenum (first 25 cm) Jejunum (2/3) Ileum (1/3) Main funchon: absorphon of nutrients, immune protechon 5

6 The large inteshne ca. 1.5 m long Cecum Ascending colon Transverse colon Descending colon Rectum Main funchon: resorphon of water and salts, stool formahon 6

7 Small inteshne cross sechon Plicae circulares + villi: Increase of absorphve surface in small inteshne ( m 2 ) 7

8 Small inteshne layers 8

9 Small inteshne mucosa IntesHnal mucosa: Epithelium + lamina propria, separated from submucosa by muscularis mucosae 9

10 Small inteshne Villus structure enables efficient uptake of nutrients 10

11 IntesHnal epithelium 11

12 Cell types in the inteshnal epithelium UndifferenHated stem cells in the crypts 4 major cell types in the epithelium: Enterocytes Goblet cells Paneth cells Enteroendocrine cells Cell turnover: ca. 5 days (shedding of epthelial cells at the Hp of the villus) 12

13 Cell types in the inteshnal epithelium 13

14 Cell types in the inteshnal epithelium: Enterocytes AbsorbHve cells Tight junchons Luminal surface (microvilli) brush border enzymes =ectoenzymes) (disaccharidase, pephdase) lipid absorphon proteins (apolipoproteins, fafy acid binding proteins) Receptors, transporters/carriers 14

15 Cell types in the inteshnal epithelium: Goblet cells Present throughout GI tract Increase in number along the inteshne (mainly in terminal ileum and colon) Produce mucus (mucins): cytoprotechve protechon from infechous agents lubricant 15

16 Cell types in the inteshnal epithelium: Paneth cells Present in the small inteshne Located at the base of the crypts Secrete anhmicrobial agents: Defensins (cyrphdins) Lysozyme Phospholipae A2 16

17 Cell types in the inteshnal epithelium: Enteroendocrine cells Present in small inteshne and colon Produce hormones and local mediators Types of enteroendocrine cells: Dcells (somatostahn) Lcells (glucagonlike pephdes) Enterochromaffin cells (serotonin) CCKproducing cells SubstanceP (PP) secrehng cells MoHlin secrehng cells 17

18 Lamina propria 18

19 Cell types and structures in the lamina propria Lamina propria = connechve Hssue underlying the epithelium Immunologically achve cells: Plasma cells (IgA synthesis) Lymphocytes (T cells, innate lymphoid cells) Macrophages, dendrihc cells, neutrophils Mast cells Other structures: Fibroblasts capillaries lymph vessels (lacteals, for anhgen transport, lipid uptake) 19

20 The inteshnal lymphahc system 20

21 Lymphoid follicles and immune cells in the inteshne 1. Immune cells clustered in secondary lymphoid organs: Peyer s patches (Ileum) Cryptopatches/isolated lymphoid follicles 2. Immune cells scafered in lamina propria 21

22 IntesHnal vessels 22

23 Mesenteric arteries Truncus coeliacus: (stomach, liver and upper duodenum) Superior mesenteric artery: (lower duodenum to transverse colon) A. pancreahcoduodenalis inferior Aa. inteshnales A. ileocolica A. colica dextra A. colica media Inferior mesenteric artery: (transverse colon to rectum) A. colica sinistra A. rectalis superior 23

24 Mesenteric veins Portal vein: V. lienalis V. mesenterica superior V. mesenterica inferior 24

25 IntesHnal InnervaHon 25

26 Autonomic nervous system 26

27 Enteric nervous system (ENS) Hundreds of neurons embedded in inteshne:! sensory neurons! motor neurons Autonomic funchon (Pacemaker in stomach, small inteshne, large inteshne)! second brain? 27

28 Small intes.ne anatomy Duodenum, jejunum, ileum Summary Epithelium, submucosa, muscularis, serosa Small intes.nal epithelium and lamina propria Enterocytes, Goblet cells, Paneth cells, Enteroendocrine cells Large number of immune cells Small intes.nal vascular supply Mesenteric arteries, veins and lymphahcs Enteric nervous system Autonomous from but communicahng with central nervous system Literature recommendahon (German): Darm mit Charme von Guilia Enders 28