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

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