gastro-intestinal system ii 2010. structure lamina mucosa epithelium (simple columnar or stratified...
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Gastro-intestinal system II2010
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 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
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