Gastro-intestinal system II 2010

Structure Lamina mucosa Epithelium (simple columnar or stratified squamous) Lamina propria (loose collagenous connective tissue) Lamina muscularis mucosae (smooth muscle) Lamina submucosa (loose collagenous connective tissue) Lamina muscularis externa (circular and longitudinal layer) Lamina advetitia or serosa (mesothelium) – loose connective tissue

Pylorus

Pylorus

Duodenum

Small intestine Duodenum Brunner glands -mucous Jejunum Ileum

Small intestine Absorptive function – increase in the total surface: Plicae circulares (circular folds) or valves of Kerkring (submucosa) Intestinal villi (lamina propria) Intestinal glands - Crypts of Lieberkühn (tubular glands) Microvilli (cells) Length – 4 – 6 m

Cells Enterocytes Goblet cells Paneth cells Neuroendocrine Cells M-cell Stem cells Intraepithelial lymphocytes

Enterocytes Resorption – brush border – microvilli (actin, villin, calmodulin)- terminal web Surface coat – glycocalyx Enzymes – disacharidases, aminopeptidases Fatty acid binding protein (FABP) - SER- resynthesis – GA - chylomicrons Na+, K+ ATPase

Brush border Actin microfilaments Terminal web Binding to the membrane in the villus and zonula adherens Intermediate fillament

Goblet cell Production of mucus – RER and CA - glycoproteins – exocytosis Protective gel coat – again mechanical abrasion and bacterial invasion

Enteroendocrine cells Diffuse endocrine – paracrine gland Cholecystokinin Secretin Gastrin Serotonin Somatostatin VIP, substance P, GIP Glucagon-like factor

Paneth cells Granules: Lysozyme TNFα Defensins (Nonspecific immunity)

Villi Outhgrowths of lamina mucosa Smooth muscle cells Fenestrated blood capillaries Lymphatic capillaries

Plexus myentericus

Protection of small intestine Peyer´s patches – gut associated lymphoid tissue – GALT Dome (antigen-presenting cells) and germinal centre Follicle associated epithelium – M-cells – transport of antigens to the antigen presenting cells Plasma cells – secretory IgA dimers – transcytosis – secretory component

Medical application Deficiencies of disaccharidases (genetic, infection, alergy to gluten) – malabsorption syndrome High rate of cell renewal (3-7 days) – affected by chemotherapy or X-ray exposure - diarrhea

Colon No Paneth cells No villi, no plicae circulares Resorption of water and ions: Colonocytes Goblet cells and enteroendocrine cels No Paneth cells

Colon Teniae coli – longitudinal bands of external longitudinal layer of smooth muscle. Appendices epiploicae: serosa forms pendulous processes – adipose tissue

Medical aplications 90 -95% of malignant tumors of the digestive tract are derived from epithelium. Stomach or large intestinum – glandular cells – adenocarcinoma Very frequent

Apendix Structure as colon However Muscularis externa is continuous it does not form tenia colli In lamina propria and submucosa, there is abundant lymphatic tissue (tonsilla abdominalis) Paneth´s cells could be present in crypts of Lieberkűhn

Apendix