Epithelial tissue Dept. Histology & Embryology, Faculty of Medicine MU pvanhara@med.muni.cz Petr Vaňhara, PhD Epithelium Muscle Nerve Connective  Contemporary tissue classification Based on morphology and function: Myofibrils  contraction Mesoderm – skeletal muscle, myocard, mesenchyme – smooth muscles Rarely ectoderm (eg. m. sphincter, 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 General characteristic of epithelial tissue • Typical morphology and cell connections  General characteristics of epithelial tissue • 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  Hallmarks of typical epithelial cell www.webanatomy.net  Basement membrane • Attachment of epithelium to underlying tissues • Selective filter barrier between epithelial and connective tissue • Communication, differentiation PASHE  Basal lamina vs. basement membrane  50-100nm  Glycosaminoglycans – heparansulfate  Laminin, collagen III, IV, VI,  Nidogen/entactin  Perlecan  Proteoglycans  Architecture of basement membrane Lamina basalis Lamina fibroreticularis BM  Modifications of basement membrane architecture • 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 …  Basement membrane in corpusculum renis  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  Embryonic origin of epithelial tissues 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, pancreas) 5. Respiratory passages (ciliated pseudostratified columnar epithelium, ciliated simple columnar epithelium, cuboidal, squamous)  Embryonic origin of epithelial tissues  derived from all three germ layers  Covering (sheet) epithelium  Trabecular epithelium  Reticular epithelium  Classification of epithelial tissues by morphology by function  Covering  Glandular  Resorptive  Sensory  Respiratory  Alveolar  Germinal  ... Morphology of epithelial tissue  Classification of epithelial tissues Vessels Kidney Intestine Respiratory passages Skin Oesophagus Ducts Urinary tract Covering (sheet) epithelia 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  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 Ovarian surface epithelium Thyroid follicles  Simple columnar epithelium ‒ GIT - stomach - small and large intestine - gall bladder Resorption / Secretion ‒ Single layer of columnar cells with large, oval, basally located nucleus  Simple columnar epithelium with kinocilia ‒ Uterine tube ‒ flow of the oocyte towards the uterus © http://www.unifr.ch www.siumed.edu  Simple columnar epithelium with kinocilia (also pseudostratified) ‒ Upper respiratory passages ‒ Removal of mucus produced by epithelial glands Other locations: ‒ Spinal cord ependyma ‒ Epididymis ‒ Vas deferens  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  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  Stratified cuboidal epithelium Large ducts of : ‒ sweat glands ‒ mammary glands ‒ salivary glands ‒ 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  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 ©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 tissues Trabecular epithelium Liver parenchyma • Cords of hepatocytes Trabecular epithelium Islets of Langerhans Cords of endocrine active cells  Endocrine glands Function of epithelial tissue  Glandular epithelium • Secret ↔ excret • Process of secretion: Holocrine  Merocrine  Apocrine  Glandular epithelium  Single cell glands – Goblet – Enteroendocrine  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  Multicellular glands • Shape of secretion part – Alveolar (acinar) – Tubular – Tubuloalveolar (tubuloacinar) • Branching – Simple – Branched – Compound • Secretion – Mucous – Serous – Compound  Multicellular glands – Endocrine vs. endocrine  Mucous glands  Mucous glands  Serous glands  Compound glands - both serous and mucous  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  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  Myoepithelium – Star-like or spindle cells – Connected by nexus and desmosomes – Actin microfilaments, myosin and tropomyosin – Contraction – Sweat and salivary glands – enhancing secretion  Regeneration 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 Metaplasia Squamous metaplasia of cervix uteri Respiratory passages Simple columnar epithelium Stratified squamous epithelium  Plasticity of epithelial tissues Simple columnar epithelium 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  EMT in tumor dissemination J Clin Invest. 2009;119(6):1438–1449. doi:10.1172/JCI38019.  EMT Thank you for attention pvanhara@med.muni.cz http://www.med.muni.cz/histology/education/ http://www.med.muni.cz/histology/petr-vanhara/