Epithelial tissue Dept. Histology & Embryology, Faculty of Medicine MU pvanhara@med.muni.cz Petr Vaňhara, PhD 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 ‒ Very early event and very novel innovation in Metazoa evolution ‒ From simple colonies of cells to highly specialized tissue structures ‒ Boundaries and interfaces ‒ Dividing of the body into separated compartments → separating individual milieu ‒ Lining of cavities or interfaces of open space ‒ Attachment and adhesion ‒ Basal membrane What can sea sponges and hydras teach us? General characteristics – lessons from primitive metazoans Evolution of epithelia Complexity of cell-cell junctions 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 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 Kolagenní vazivo BM ARCHITECTURE OF BASEMENT MEMBRANE • Two basic layers – lamina basalis • lamina densa, • lamina rara ext. et int. – lamina fibroreticularis • Tissue specific modifications ‒ Descemet membrane (cornea) ‒ Glomerular BM (Bowman’s capsule) ‒ Part of Bruch’s membran of retina … MODIFICATION OF BASEMENT MEMBRANE 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. Výstelka žlučníku (simple columnar epithelium) 4. Solid glands (liver, pancreas) 5. Respiratory passages (ciliated pseudostratified columnar epithelium, ciliated simple columnar epithelium, cuboidal, squamous)  derived from all three germ layers EMBRYONIC ORIGIN OF EPITHELIAL TISSUE  Covering (sheet) epithelium  Trabecular epithelium  Reticular epithelium 1) morphology 2) function  Covering  Glandular  Resorptive  Sensory  Respiratory  Alveolar  Germinal  ... CLASSIFICATION OF EPITHELIAL TISSUE According to 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 cubic 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 ‒ 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 ‒ Upper respiratory passages ‒ Removal of mucus produced by epithelial glands ‒ Epididymis ‒ Vas deferens CLASSIFICATION OF EPITHELIAL TISSUE  Pseudostratified columnar epithelium with stereocilia  Stratified squamous epithelium Keratinized vs. non-keratinized  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 central nuclei, flattening towards the surface  First layer in contact with BM, last layer – flat CLASSIFICATION OF EPITHELIAL TISSUE  Stratified squamous epithelium Keratinized Skin (epidermis) Nail Keratins Fibrous proteins, ~ 40 types Very stable, multimeric Disorders of keratin expression – variety of clinical symptoms e.g. Epidermolysis bullosa simplex 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 bladder, kidneys, ureters  Transitional epithelium (urothelium) Empty: rather cuboidal with a domed apex Relaxed: 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), uroplakin proteins in the apical cell membrane ‒ capillary plexus in the submucosa CLASSIFICATION OF EPITHELIAL TISSUE ©http://www.cytochemistry.net/microanatomy/epithelia/salivary7.jpg  Stratified columnar epithelia ‒ several layers of columnar cells ‒ secretion / protection ‒ ocular conjunctiva ‒ pharynx, anus – transitions ‒ uterus, male urethra, vas deferens ‒ intralobular ducts of salivary glands CLASSIFICATION OF EPITHELIAL TISSUE 2) Trabecular epithelium Liver parenchyma CLASSIFICATION OF EPITHELIAL TISSUE • Cords of hepatocytes Trabecular epithelium CLASSIFICATION OF EPITHELIAL TISSUE 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 Reticular epithelium Thymus CLASSIFICATION OF EPITHELIAL TISSUE Function CLASSIFICATION OF EPITHELIAL TISSUE  Glandular epithelium • Secret ↔ excret • 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  Multicellular glands • Shape of secretion part – Alveolar (acinar) – Tubular – Tubuloalveolar (tubuloacinar) • Branching – Simple – Branched – Compound • Secretion – Mucous – Serous – Compound GLANDULAR EPITHELIUM  Multicellular glands – Endocrine vs. endocrine GLANDULAR EPITHELIUM  Mucous glands GLANDULAR EPITHELIUM  Mucous glands GLANDULAR EPITHELIUM  Serous glands GLANDULAR EPITHELIUM  Compound glands - both serous and mucous GLANDULAR EPITHELIUM GLANDULAR EPITHELIUM  Transport and resorption Glucose transport HCl secretion in stomach http://www.ncbi.nlm.nih.gov/books/NBK21502/ GLANDULAR EPITHELIUM  Respiratory epithelium Respiratory passages – Moisten, protect against injury and pathogen – Remove particles by „mucociliary escalator“ – Pseudostratified columanr epithelim with cilia – Basal cells- epithelium renewal Alveolar epitheithelium – Gas exchange – Respiratory bronchiols, 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 Receptory region, body, axonal process Nasal epithelium (regio olfactoria nasi), rods and cones Secondary sensory cells Receptory region and body Signal is trasmitted by adjacent neurons terminating on secondary sensory cell Taste buds, vestibulocochlear appratus CLASSIFICATION OF EPITHELIAL TISSUE  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 Different regenerative potential (epidermis  sensory epithelium of inner ear) Multi- a 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 Metaplasia Squamous metaplasia of cervix uteri Respiratory passages Simple columnar epithelium Stratified squamous epithelium Simple columnar epithelium PLASTICITY OF EPITHELIAL TISSUES Metaplasia Development of precancerous lesions PLASTICITY OF EPITHELIAL TISSUES Wikipedia.org; http://radiology.uchc.edu Hyperplasia Normal prostate Hyperplasia of prostate glandular epithelium Prostate adenocarcinoma PLASTICITY OF EPITHELIAL TISSUES 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 PLASTICITY OF EPITHELIAL TISSUES http://www.med.muni.cz/histology FURTHER STUDY Thank you for attention pvanhara@med.muni.cz http://www.med.muni.cz/histology/education/ http://www.med.muni.cz/histology/petr-vanhara/