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Cell systems Epithelial tissue 2009 Slide 2 Cell systems Systems of cells with typical features and specific function Epitheliocytes intercellular junctions (epithelia and neural tissue) Mechanocytes adhesion to the molecules of the intercellular space (connective tissue and muscles) Amebocytes movable (blood cells) Slide 3 Epithelial tissue It is composed from cells closely arranged with very little extracellular tissue Typical feature of epithelial cells is polarity, cells are lying on the lamina basalis. Important is the cell adhesion Nutrition difusion from connectives (without vessels) Inervation nerve ending are frequent Regeneration good especially in covering epithelia stem cells proliferation and movement along basement membrane Slide 4 Types of epithelial tissue Layers - flat sheets covering, lining the body surface, glands Cords (endocrine glands, liver) Reticulum network (thymus) Development from all three embryonic germ layers ectoderm, endoderm and mesoderm Slide 5 Function: Covering and lining Absorption Secretion Sensation Contractility (myoepithelial cells) Slide 6 Compartments of cell Apical: Microvilli, stereocilia,cilia Lateral: Intercellular junction Basal: Basal lamina and basement membrane Slide 7 Apical differentiation: Microvilli - finger-like projection containing actin microfilaments brush border glycocalyx Terminal web (actin and intermediate filaments) attachment to the zonula adherens by alfa actinin and vinculin. Slide 8 Apical differentiation Stereocilia long and branching processes (immobile) Kinocilia mobile - till 10 m axial microtubules - 9 duplets + 2 central, basal body and rootlets Slide 9 Kinocilia Kinocilia - peripheral- 9 duplets of microtubules and one pair of central microtubules Molecular motor - dynein = axial complex Basal body = centriol - 9 triplets of microtubules Rootlets intermediate filaments Slide 10 Intercellular junction Zonula occludens Zonula adherens Macula adherens, desmosome Gap junctions Slide 11 Intercellular junction Tight junction zonula occludens controls and prevents free passage of substances across epithelium Determine cell polarity Occludins and claudins barrier Slide 12 Adhesive anchoring junction Zonula adherens Cadherins + actin Desmosome (macula adherens) Cadherins + intermediate filaments (cytokeratins) Slide 13 Communicating junction Gap junction connexons channel-like structures (connexins - proteins) exchange of small molecules till 1500 Da. Slide 14 Attachment to the background Integrins attachment to the extracellular matrix and basal lamina (Ca independent)-signaling Focal adhesion (actin) Hemidesmosome (intermediate filaments) Slide 15 Basal lamina Structure lamina densa and lamina rara (lucida) collagen type IV, laminin, fibronectin, entactin and proteoglycans (heparan sulphate proteoglycan) Produced by epithelial cells (and others - adipocytes, muscle cells, Schwann cells) barrier and attachment to extracellular matrix. Regulate proliferation and differentiation Loss of contact induces apoptosis Slide 16 Basal lamina Slide 17 Basement membrane Visible in light microscopy. Structure basal lamina a lamina reticularis (connective tissue) achoring collagen fibrils and reticular fibres attachment to connective tissue Sometimes for the fusion of two basal laminae kidney and lung alveoli Slide 18 Cellular types Transporting cells Signaling cells Secretory and exporting cells Myoepithelial cells Stem cells Slide 19 Transport through membrane Endocytosis plasmatic membrane forms invaginations surrounding particle vesicle (endosom):Pinocytosis (vesicle contains fluid), fagocytosis (vesicle contains dense particle). Exocytosis content of vesicle is secreated from cell. Proteins are syntetized on RER and GA. These vesicle migrate to the plasma membrane, where they either fused immediately with the membrane and discharge their content to the exterior (constitutive secretion) or they are stored near the membrane until a signal such as a neurotransmitter or hormone causes them to fuse with the membrane and release the enclosed content (regulated secretion ). Slide 20 Transporting cells Pinocytotic invagination and vesicules transport of macromolecules in the cell or through cells Transport through vascular endothelium - calveolae Clathrin forms layer on the inner surface of plasmalemma and enables vesicule formation Slide 21 Transporting cells Active transport Na,K ATPase sodium pump - invagination of basal cell membrane, mitochondria source of energy Basolateral labyrinth Tight junction compartments of cellular surface Slide 22 Signaling cells Cells are specialized to production of signal molecules - hormones (different chemical structure - proteins, glycoproteins, lipids) They affect target cells, which are far from cells producing signal molecule (hormone) (endocrine signaling) or which are in their neighbourhood (paracrine signaling) Cells form cords (parathyroid gland, islets of Langerhans) Cells form follicle or vesicles filled by noncellular material (thyroid gland) Slide 23 Steroid producing cells Lipids Tubular or vesicular types of mitochondria SER Slide 24 Types of secretion Merocrine secretory granuls Apocrine granules and parts of apical cytoplasma Holocrine destruction of cell whole is changed in secretion Slide 25 Myoepithelial cell Cytokeratins Actin and myosin Slide 26 Stem cell Regeneration Self-renewal Slide 27 Epithelial cell - derived tumors Metaplasia transformation of cells into the other type Benign X malignant (carcinoma) Origin from stem cells (progenitor cells) loss of typical features polarity and basal lamina. It enables invasivity and metastasis formation. Loss of cadherins is jointed with tumor invasivity loss of contact inhibition. Cells loosing typical features are more malignant - they grow faster Typical cytokeratins are used for diagnosis