1. Cell systems Epithelial tissue
2009

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)

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

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

5. Function: Covering and lining Absorption Secretion Sensation
Contractility (myoepithelial cells)

6. Compartments of cell Apical: Microvilli, stereocilia,cilia
Lateral: Intercellular junction
Basal: Basal lamina and basement membrane

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.

8. Apical differentiation
Stereocilia – long and branching processes (immobile)
Kinocilia – mobile - till 10 μm – axial microtubules - 9 duplets + 2 central , basal body and rootlets

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

10. Intercellular junction
Zonula occludens
Zonula adherens
Macula adherens, desmosome
Gap junctions

11. Intercellular junction
Tight junction – zonula occludens – controls and prevents free passage of substances across epithelium
Determine cell polarity
Occludins and claudins – barrier

12. Adhesive – anchoring junction
Zonula adherens
Cadherins + actin
Desmosome (macula adherens)
Cadherins + intermediate
filaments (cytokeratins)

13. Communicating junction
Gap junction – connexons – channel-like structures (connexins - proteins) exchange of small molecules till 1500 Da.

14. Attachment to the background
Integrins –attachment to the extracellular matrix and basal lamina (Ca independent)-signaling
Focal adhesion (actin)
Hemidesmosome (intermediate filaments)

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

16. Basal lamina

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

18. Cellular types Transporting cells Signaling cells
Secretory and exporting cells
Myoepithelial cells
Stem cells

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 ).

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

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

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)

23. Steroid producing cells
Lipids
Tubular or vesicular types of mitochondria
SER

24. Types of secretion Merocrine – secretory granuls
Apocrine – granules and parts of apical cytoplasma
Holocrine – destruction of cell – whole is changed in secretion

25. Myoepithelial cell
Cytokeratins
Actin and myosin

26. Stem cell
Regeneration
Self-renewal

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