Epithelial tissue Petr Vaňhara Epithelium Muscle Nerve Connective Based on morphology and function: Myofibrils → contraction Mesoderm – skeletal muscle, myocard, mesenchyme – smooth muscles Rarely ectoderm (eg. m. sphincter a m. dilatator pupillae) Neurons and neuroglia Reception and transmission of electric signals Ectoderm, rarely mesoderm (microglia) Dominant extracellular matrix Connective tissue, cartilage, bone… Mesenchyme Continual, avascular layers of cells with different function, oriented to open space, with specific junctions and minimum of ECM and intercellular space. Derivates of all three germ layers CONTEMPORARY TISSUE CLASSIFICATION General characteristics EPITHELIAL TISSUE • Cell arrangement • Specific morphology • Surface modifications • Adhesion • Tissue barriers trachea EPITHELIUM EPITHELIAL VARIABILITY IN HUMANS • Typical morphology and cell connections • Avascular (without blood supply) – nutrition by diffusion from a highly vascular and innervated area of loose connective tissue (lamina propria) just below the basement membrane • Highly cellular – cohesive sheet or groups of cells with no or little extracellular matrix GENERAL CHARACTERISTICS OF EPITHELIAL TISSUE https://doi.org/10.1038/aps.2011.20 APICAL DOMAIN BASOLATERAL DOMAIN EPITHELIUM MESENCHYME vs. CELL POLARITY https://doi.org/10.1038/aps.2011.20 CELL POLARITY www.webanatomy.net HALLMARKS OF A TYPICAL EPITHELIAL CELL • Attachment of epithelium to underlying tissues • Selective filter barrier between epithelial and connective tissue • Communication, differentiation PASHE BASEMENT MEMBRANE ▪ 50-100nm ▪ Glycosaminoglycans – heparansulfate ▪ Laminin, collagen III, IV, VI, ▪ Nidogen/entactin ▪ Perlecan ▪ Proteoglycans BASAL LAMINA vs. BASEMENT MEMBRANE Dunsmore SE, Chambers RC, Laurent GJ. 2003. Matrix Proteins. Figure 2.1.2. In: Respiratory Medicine, 3rd ed. London. Saunders, p. 83; Dunsmore SE, Laurent GJ. 2007. Lung Connective Tissue. Figure 40.1. In: Chronic Obstructive Pulmonary Disease: A Practical Guide to Management, 1st ed. Oxford. Wiley-Blackwell, p. 467. ▪ Basement membrane Kolagen IV Laminin Perlecan, Nidogen/Entactin BASEMENT MEMBRANE Lamina basalis Lamina fibroreticularis Fibroblast BM ARCHITECTURE OF BASEMENT MEMBRANE Epithelium • Two basic layers of basement membrane – lamina basalis – lamina fibroreticularis • Tissue specific modifications ‒ Descemet membrane (cornea) ‒ Glomerular BM (Bowman’s capsule) ‒ Part of Bruch’s membran of retina … MODIFICATIONS OF BASEMENT MEMBRANE • Contact of two epithelia (or with endothelium) – fusion of laminae basales • lamina densa • lamina rara (lucida) ext. et int. BASEMENT MEMBRANE IN CORPUSCULUM RENIS • Clinical correlations – membranous glomerulonefritis - circulationg Abs bind to BM of capillary wall - complement (C5b-C9) attacks glomerular endothelial cells - filtation barrier compromised - proteinuria, edema, hematouria, renal failure BASEMENT MEMBRANE IN CORPUSCULUM RENIS EMBRYONIC ORIGIN OF EPITHELIAL TISSUE Germ layer Epithelial derivatives Ectoderm 1. Epidermis (stratified squamous keratinized epithelium) 2. Sweat glands and ducts (simple and stratified cuboidal epithelium) 3. Oral cavity, vagina, anal canal (stratified squamous non-keratinized epithelium) Mesoderm 1. Endothelium of blood vessels (simple squamous epithelium) 2. Mesothelium of body cavities (simple squamous epithelium) 3. Urinary and reproductive passages (transitional, pseudostratified and stratified columnar epithelium, simple cuboidal and columnar epithelium) Endoderm 1. Esophagus (stratified squamous non-keratinized epithelium) 2. GIT (simple columnar epithelium) 3. Gall bladder (simple columnar epithelium) 4. Solid glands (liver, pankreas) 5. Respiratory passages (ciliated pseudostratified columnar epithelium, ciliated simple columnar epithelium, cuboidal, squamous epithelium) 6. Part of urinary system (cloaca-derived) ▪ derived from all three germ layers EMBRYONIC ORIGIN OF EPITHELIAL TISSUE ▪ Covering (sheet) epithelium ▪ Trabecular epithelium ▪ Reticular epithelium 1) morphology 2) function ▪ Covering ▪ Glandular ▪ Resorption ▪ Sensory ▪ Respiratory ▪ Alveolar ▪ Germinal ▪ ... CLASSIFICATION OF EPITHELIAL TISSUE According to Classification by morphology CLASSIFICATION OF EPITHELIAL TISSUE Vessels Kidney Intestine Respiratory passages Skin Oesophagus Ducts Urinary tract 1) Covering (sheet) epithelia CLASSIFICATION OF EPITHELIAL TISSUE Endothelium heart, blood, and lymphatic vessels. Mesothelium serous membranes - body cavities ▪ Simple squamous epithelium ‒ Capillaries ‒ Lung alveolus ‒ Glomerulus in renal corpuscle Selective permeabilty ‒ Single layer of flat cells with central flat nuclei CLASSIFICATION OF EPITHELIAL TISSUE CLASSIFICATION OF EPITHELIAL TISSUE ▪ Simple cuboidal epithelium ‒ Single layer of cuboidal cells with large, spherical central nuclei Examples: ‒ Ovarian surface epithelium ‒ Renal tubules ‒ Thyroid ‒ Secretion acini ‒ Secretion or resorption CLASSIFICATION OF EPITHELIAL TISSUE Ovarian surface epithelium Thyroid follicles CLASSIFICATION OF EPITHELIAL TISSUE ▪ Simple columnar epithelium ‒ Typicall epithelium of GIT - stomach - small and large intestine - gall bladder Resorption / Secretion ‒ Single layer of columnar cells with large, oval, basally located nucleus CLASSIFICATION OF EPITHELIAL TISSUE ▪ Simple columnar epithelium with kinocilia Uterine tube ‒ flow of the oocyte towards the uterus CLASSIFICATION OF EPITHELIAL TISSUE ▪ Pseudostratified columnar epithelium with kinocilia and goblet cells Upper respiratory passages ‒ Removal of mucus produced by epithelial glands CLASSIFICATION OF EPITHELIAL TISSUE CLASSIFICATION OF EPITHELIAL TISSUE Male reproductive passages ‒ Epididymis ‒ Ductus deferens ▪ Pseudostratified columnar epithelium with stereocilia ▪ Non-keratinized stratified squamous epithelium ▪ Constant abrasion ▪ Mechanical resilience ▪ Protection from drying ▪ Rapid renewal Examples: ▪ Cornea ▪ Oral cavity and lips ▪ Esophagus ▪ Anal canal ▪ Vagina ▪ Multiple layers of cubic cells with centrally localized nuclei, flattening towards surface ▪ Cells in the superficial layer viable ▪ First layer in contact with BM, last layer – squamous CLASSIFICATION OF EPITHELIAL TISSUE ▪ Keratinized stratified squamous epithelium ▪ Cell in the superficial layer dead ▪ Skin (epidermis) ▪ Nail ▪ Keratins ▪ Fibrous proteins, ~ 40 types ▪ Intermediate filaments ▪ Very stable, multimeric ▪ Disorders of keratin expression – variety of clinical symptoms ▪ e.g. Epidermolysis bullosa simplex (mutations in the genes encoding keratin 5 or keratin 14) CLASSIFICATION OF EPITHELIAL TISSUE ▪ Stratified cuboidal epithelium Large ducts of: ‒ sweat glands ‒ mammary glands ‒ salivary glands CLASSIFICATION OF EPITHELIAL TISSUE ▪ fluctuation of volume ▪ organization of epithelial layers ▪ membrane reserve ▪ protection against hyperosmotic urine Urinary system ▪ urinary bladder, ureters, renal calyx and pelvis ▪ Transitional epithelium (urothelium) Empty (relaxed): rather cuboidal cells with a domed apex Full: flat,stretched ▪ Basal cells ▪ Intermediate layer ▪ Surface cells CLASSIFICATION OF EPITHELIAL TISSUE ▪ Transitional epithelium (urothelium) ▪ glycosaminoglycan layer (GAG) on the surface ▪ osmotic barrier ▪ antimicrobial properties Barrier architecture: ▪ GAG-layer ▪ surface cells (tight junctions), uroplakins proteins in the apical cell membrane ▪ subepithelial capillary network CLASSIFICATION OF EPITHELIAL TISSUE ©http://www.cytochemistry.net/microanatomy/epithelia/salivary7.jpg ▪ Stratified columnar epithelia ‒ several layers of columnar cells ‒ secretion / protection ‒ occular conjunctiva ‒ pharynx, anus – transitions ‒ male urethra, vas deferens ‒ large ducts of salivary glands CLASSIFICATION OF EPITHELIAL TISSUE 2) Trabecular epithelium Liver parenchyma CLASSIFICATION OF EPITHELIAL TISSUE Trabecules of hepatocytes develop from sheet epithelial layer of primitive gut lining CLASSIFICATION OF EPITHELIAL TISSUE ▪ Liver Islets of Langerhans Cords of endocrine active cells ▪ Endocrine glands CLASSIFICATION OF EPITHELIAL TISSUE Adrenal cortex Cortex of adrenal gland – epithelial cells in cords secreting corticoid ▪ Endocrine glands CLASSIFICATION OF EPITHELIAL TISSUE Adenohypophysis – anterior pituitary ▪ Endocrine glands CLASSIFICATION OF EPITHELIAL TISSUE Thymus - cytoretikulum ▪ Compartments and microenvironment for T-cell development and selection ▪ Blood-thymus barrier RETIKULÁRNÍ EPIELCLASSIFICATION OF EPITHELIAL TISSUE Epithelial reticular (epithelioreticular) cells: Structural and functional support for developing T-lymphocytes CLASSIFICATION OF EPITHELIAL TISSUE Sheet Trabecular Reticular SUMMARY Classification by function CLASSIFICATION OF EPITHELIAL TISSUE Ways of secretion • Secretion ↔ excretion • Process of secretion: Holocrine  Merocrine  Apocrine CLASSIFICATION OF EPITHELIAL TISSUE ▪ Single cell glands – Goblet – Enteroendocrine GLANDULAR EPITHELIUM ▪ Goblet cells - Mainly respiratory and intestinal tract - Produce mucus = viscous fluid composed of electrolytes and highly glycosylated glycoproteins (mucins) - Protection against mechanic shear or chemical damage - Trapping and elimination of particular matter - Secretion by secretory granules constitutive or stimulated - After secretion mucus expands extremely – more than 500-fold in 20ms - Dramatic changes in hydration and ionic charge - Chronic bronchitis or cystic fibrosis – hyperplasia or metaplasia of goblet cells GLANDULAR EPITHELIUM GOBLET CELL Exocrine Endocrine ▪ Multicellular glands GLANDULAR EPITHELIUM ▪ Development of multicellular glands – Endocrine vs. exocrine GLANDULAR EPITHELIUM ▪ Exocrine multicellular glands • Shape of secretion part – Alveolar (acinar) – Tubular – Tubuloalveolar (tubuloacinar) • Branching – Simple – Branched – Compound • Secretion – Mucous – Serous – Compound GLANDULAR EPITHELIUM ▪ Mucous glands GLANDULAR EPITHELIUM ▪ Mucous glands GLANDULAR EPITHELIUM ▪ Serous glands GLANDULAR EPITHELIUM • Mixed glands GLANDULAR EPITHELIUM ▪ mixed serous and mucous secretion GLANDULAR EPITHELIUM Myoepithelium ▪ star-like or spindle cells ▪ connected by nexus and desmosomes ▪ actin microfilaments, myosin and tropomyosin ▪ contraction ▪ sweat and salivary glands – enhancing secretion CLASSIFICATION OF EPITHELIAL TISSUE DOI: 10.4103/0973-029X.190952 Transcellular transport through epithelial cells is driven by concentration and/or charge gradients Glucose transport HCl secretion in stomach http://www.ncbi.nlm.nih.gov/books/NBK21502/ GLANDULAR EPITHELIUM Respiratory epithelium Epithelium of respiratory passages ▪ Moistening and protection against injury and pathogens ▪ Remove particles by mucociliary clearance ▪ Pseudostratified columnar epithelium with cilia ▪ Basal cells → epithelium renewal Alveolar epithelium ▪ Gas exchange ▪ Surfactant ▪ Respiratory bronchioles, alveolar passages and alveoli ▪ Type I and II pneumocytes CLASSIFICATION OF EPITHELIAL TISSUE Sensory epithelium – Supportive and sensory cells Primary sensory cells ‒ directly convert stimuli to membrane potential ‒ receptor region, body, axonal process ‒ olfactory epithelium (regio olfactoria nasi), rods and cones Secondary sensory cells ‒ receptor region and the cell body ‒ signal is transmitted by adjacent neurons terminating on secondary sensory cell ‒ taste buds, vestibulocochlear apparatus CLASSIFICATION OF EPITHELIAL TISSUE Renewal of epithelium ▪ different regenerative potential (epidermis  sensory epithelium of inner ear) ▪ multi- and oligopotent stem cells ▪ microenvironment – stem cell niche Example: Regeneration of intestine epithelium REGENERATION OF EPITHELIAL TISSUE Example: Regeneration of intestine epithelium REGENERATION OF EPITHELIAL TISSUE Abnormal renewal: metaplasia • squamous metaplasia of cervix uteri • respiratory passages Simple columnar epithelium Stratified squamous epithelium Simple columnar epithelium PLASTICITY OF EPITHELIAL TISSUES • risk of development of precancerous lesions PLASTICITY OF EPITHELIAL TISSUES Abnormal renewal: metaplasia Wikipedia.org; http://radiology.uchc.edu Normal prostate Hyperplasia of prostate glandular epithelium Prostate adenocarcinoma PLASTICITY OF EPITHELIAL TISSUES Abnormal renewal: hyperplasia PLASTICITY OF EPITHELIAL TISSUES Abnormal renewal: dysplasia and neoplasia • uncoupling from regulatory mechanisms • change in morphology and acqusition of new biological properties • tumor development Hanahan & Weinberg, Cell 2011. The six hallmarks of cancer. https://doi.org/10.1016/j.cell.2011.02.013 • uncoupling from regualtory mechanisms • tumor development PLASTICITY OF EPITHELIAL TISSUES Abnormal renewal: neoplasia Epithelial to mesenchymal transition (EMT) J Clin Invest. 2009;119(6):1420–1428. doi:10.1172/JCI39104. PLASTICITY OF EPITHELIAL TISSUES EMT in embryonic development PLASTICITY OF EPITHELIAL TISSUES EMT in tumor dissemination PLASTICITY OF EPITHELIAL TISSUES PLASTICITY OF EPITHELIAL TISSUES J Clin Invest. 2009;119(6):1438–1449. doi:10.1172/JCI38019. EMT overview PLASTICITY OF EPITHELIAL TISSUES http://www.histology.med.muni.cz/ FURTHER STUDY Thank you for attention pvanhara@med.muni.cz http://www.histology.med.muni.cz Questions? Comments?