Epithelium, Connective, and Muscle Tissue - F2024 Student PDF

Epithelium, connective and muscle tissue Ashwini Bhat Office- GC 40 C Wing [email protected] Office hours: Mon- Fri 10 am- 12 pm Learning objectives ANT.2: Understand the microscopic anatomy and functional correlates of epi...

Epithelium, connective and muscle tissue Ashwini Bhat Office- GC 40 C Wing [email protected] Office hours: Mon- Fri 10 am- 12 pm Learning objectives ANT.2: Understand the microscopic anatomy and functional correlates of epithelia. Given a clinical scenario, description or image, the student should be able to: ANT.2.1. Describe the general microscopic characteristics of epithelia. ANT.2.2. Classify the types of epithelia based on their microscopic features, sites, and functions. MCB.16.1. Determine the type of cell-cell and/or cell-matrix interaction important for the normal function of a tissue. ANT.2.3. Describe the microscopic anatomy of glands, their modes of secretion, and functions. [email protected]  Learning objectives ANT.3: Understand the microscopic anatomy and functions of connective tissues and muscles. Given a clinical scenario, image, or description, students should be able to: ANT.3.1. Differentiate the histologic features of the types of connective tissue. ANT.3.2. Distinguish connective tissue cells and their functions. ANT.3.3. Differentiate the microscopic anatomy of smooth, skeletal and cardiac muscle types. [email protected]  Textbook readings: Pawlina W. & Ross M. H. (2024). Histology: A Text and Atlas with Correlated Cell and Molecular Biology (9th ed.). Philadelphia, PA: Wolters Kluwer / Lippincott Williams and Wilkins. http://auamed.idm.oclc.org/login?url=https://premiumbasicsciences.lwwhealthlibrar y.com/book.aspx?bookid=3290 Agur, A. M. R., Dalley, A. F., & Moore, K. L. (2024). Moore’s Essential Clinical Anatomy (7th ed.). Philadelphia: Wolters Kluwer. http://auamed.idm.oclc.org/login?url=https://premiumbasicsciences.lwwhealthlibr ary.com/book.aspx?bookid=3243 [email protected]  ANT.2.1. Describe the general microscopic characteristics of epithelia. [email protected]  Epithelium Epithelium covers body surfaces, lines body cavities, and constitutes glands. The principal functions of epithelial tissues include: Covering, lining, and protecting surfaces (Ex-epidermis) Absorption (Ex-the intestinal lining) Secretion (Ex- parenchymal cells of glands) Specific cells of certain epithelia may be contractile (myoepithelial cells) or specialized sensory cells, such as those of taste buds or the olfactory epithelium. [email protected]  General features: Basal lamina- a noncellular, protein– polysaccharide-rich layer Junctional complex- Epithelial cells adhere to one another by means of specific cell-to-cell adhesion molecules that form specialized cell junctions Avascular- nourishment through diffusion Regeneration Polarity [email protected] Image source: https://histologyslides.med.umich.edu/Histology/EMsmallCharts/  ANT.2.2. Classify the types of epithelia based on their microscopic features, sites, and functions. [email protected]  Classification of epithelium Number of layers Cell morphology Squamous Simple Stratified Pseudostratified Cuboidal Columnar [email protected] [email protected] Simple squamous epithelium Single layer of thin cells facilitate exchange, acts as barrier and secretory Ex-Vascular endothelium, Lung alveoli Lining of blood Alveoli of lung vessels Simple cuboidal epithelium Composed of a single row of cube- shaped cells with spherical nuclei Absorption and secretion Ex-Small ducts of exocrine glands, Thyroid follicles Pancreatic duct Thyroid follicles [email protected] Simple columnar epithelium Single layer of cells that are taller than they are wide. Absorption, secretion, lubrication & protection Non-ciliated Ex-Small intestine, Gallbladder Common bile duct Small intestine Ciliated Ex- Bronchiole, Uterine tube Bronchiole in lung Uterine tube [email protected] Pseudostratified epithelium Tall columnar and short basal cells, all of which contact the basement membrane. Nuclei at different levels The layered appearance of the nuclei make this epithelium appear stratified, hence the term, pseudostratified Protection, secretion; cilia mediated transport of particles trapped in mucus out of the air passages Ex- Nasal cavity, Larynx, Trachea, Bronchus- Respiratory epithelium Trachea with ciliated epithelium [email protected] [email protected]  Stratified Epithelium Non-keratinized Stratified Squamous Keratinized Protection, secretion; prevents water loss Ex- Esophagus, Oral cavity, Epidermis of skin, Vagina, Keratin Non-keratinized- Vagina Keratinized- Epidermis of Skin [email protected]  Stratified Epithelium Stratified Cuboidal Stratified Columnar Function- Barrier, Conduit Function- Barrier, Conduit Ex- Sweat gland ducts Ex- Large ducts of exocrine glands Duct of salivary gland Duct of esophageal glands Duct of sweat gland [email protected]  Stratified Epithelium Transitional epithelium Functions- Barrier, distensible property Rapidly adapts to distention and contraction by changing from a taller to thinner epithelium. Umbrella cells are highly dynamic cells at the luminal surface. ‘Urothelium’ Ex- Urinary bladder, ureters, urethra, renal calyces [email protected]  ANT.2.1. Describe the general microscopic characteristics of epithelia. MCB.16.1. Determine the type of cell-cell and/or cell-matrix interaction important for the normal function of a tissue. [email protected]  Epithelial cell polarity Epithelial cells generally show polarity, with organelles and membrane proteins distributed unevenly within the cell. Thus, different surfaces differ significantly in both structure and function. The region of the cell usually facing a space/lumen, is the apical pole. The opposite end, contacting the ECM and connective tissue is called the basal pole. Regions of cuboidal or columnar cells that adjoin neighboring cells comprise the cells’ lateral surfaces. [email protected]  Apical domain & its modifications Microvilli-Small, finger-like Cilia -Hair-like extensions of cytoplasmic processes which apical plasma membrane. increase the apical surface area for absorption. Stereocilia - Long microvilli Small intestine with microvilli which facilitate absorption. Ex- male reproductive system (absorption) and Trachea with cilia sensory epithelium of the C- cilia BB- basal bodies inner ear (sensory mechanoreceptors) Epididymis with stereocilia [email protected]  Basal domain Lateral domain Features: Features: Basement membrane Characterized by the presence of unique Cell-to-extracellular matrix junctions- proteins, the cell adhesion molecules (CAMs) anchor the cell to the extracellular matrix; that form junctional complexes between the they are represented by focal adhesions and apposed lateral domains of neighboring cells hemidesmosomes Occluding, Basal cell membrane infoldings- increase Anchoring, the cell surface area and facilitate interactions between adjacent cells and extracellular matrix Communicating junctions proteins. Microvilli(MV) Tight junction(TJ) Adherent junction(AJ) Desmosome(D) Intermediate filaments(IF) [email protected]  ANT.2.3. Describe the microscopic anatomy of glands, their modes of secretion, and functions. [email protected] Glandular Epithelium [email protected]  Glandular Epithelium Types of glands- Endocrine & Exocrine Three basic types of secretions from exocrine glands Merocrine secretion- most common and involves exocytosis of the vesicle content at the apical cell membrane Apocrine secretion- secretory product is enveloped by plasma membrane with cytoplasm & released in the apical portion of the cell- lactating mammary gland cells secrete lipid droplets into the milk. Holocrine secretion- secretory product accumulates & causes disintegration of secretory cells discharging it into the glands as seen in sebaceous glands of hair follicles [email protected]  Glandular Epithelium Exocrine glands are classified as either unicellular or multicellular Goblet cells from small intestine [email protected]  ANT.3.1. Differentiate the histologic features of the types of connective tissue. ANT.3.2. Distinguish connective tissue cells and their functions. [email protected]  Connective tissue Physically connects other tissues and cells to form the organs of the body Binding material that acts like glue Metabolic support to cells Highly vascular, rich in nerve plexus and lymph vessels Components of Connective tissue: Extracellular matrix (ECM) Connective tissue cells [email protected]  Extracellular matrix Ground substance Fibers Glycosaminoglycans (GAG’s) Collagen Proteoglycans Elastic Glycoproteins Reticular Ground substance ensures: ✓ Diffusion of small molecules ✓ Lubrication ✓ Barrier to penetrating microorganisms (bacteria) [email protected] Connective tissue fibers Collagen Elastic Reticular Photomicrograph of a mesentery Photomicrograph of a lymph spread stained with resorcin- node silver preparation- fuchsin- collagen (C) and elastic (E) reticular fibers (black arrow) fibers [email protected]  Collagen fibers Tensile strength Most abundant structural components of connective tissue Made of wavy collagen fibrils, seen as bundles Synthesized by fibroblast Resistant to normal shearing and tearing forces Classified as Type I to XXV Examples –ligaments, tendons, skin, bone. [email protected] Dermis of the skin  Elastic fibers Elasticity Thinner than collagen fibers Arranged in branching pattern Stretch easily with almost perfect recoil Composed of elastin(core) surrounded by network of fibrillin microfibrils Examples- Aorta, dermis of skin, lungs, uterus, and the ligamentum nuchae of neck Elastic fibers in large sized arteries [email protected]  Reticular fibers Collagen type III Rete = net Forms an extensive network (reticulum) to support and keep the different types of cells in position (liver, spleen, bone marrow). Reticular fibers in lymph nodes [email protected]  Connective tissue cells Resident cells Fibroblast Adipocytes Macrophages Mast cells Stem cells Wandering/transient cells Lymphocytes Neutrophils Eosinophils Basophils Monocytes Plasma cells [email protected]  Fibroblasts Adipocytes Principle cells Specialized connective tissue cells that store Responsible for synthesis of extracellular neutral fat and produce a variety of elements hormones Nucleus is elongated/disc shaped, with Individually cells are oval or spherical, when packed together are polygonal thin flattened cytoplasmic process Fat gets stored inside the cells and not extracellular Active fibroblasts with large euchromatic nuclei (a) and Inactive fibroblast with heterochromatic nuclei (b) [email protected]  Mast cells Macrophages Develop in bone marrow and differentiate Phagocytic cells derived from monocytes in connective tissue Contain an abundant number of lysosomes and Basophilic granules that store mediators of play an important role in immune response inflammation (histamine and heparin) reactions Histamine causes allergic reactions ( skin Removal of apoptotic cells, tissue debris rashes, sneezing, watery eyes) & Abundant in sites of inflammation. contributes to dilation of blood vessels which increases permeability and lowers blood pressure Heparin prevents blood clotting Mast cells from CT Macrophages from lymph nodes [email protected]  Adult stem cells Wandering cells Adult stem cells are found in many tissues and organs, residing in specific sites Lymphocytes referred to as niches. These cells give rise to differentiated cells Neutrophils that function in repair and formation of Eosinophils WBC new tissue, as in wound healing. Basophils Monocytes Plasma cells WBC Plasma cells [email protected]  Classification of connective tissue Embryonic CT Specialized CT Connective Tissue Proper Mesenchyme Bone (MSK) Mucoid Cartilage (MSK) Blood & hemopoietic (CVS) Dense connective Loose tissue Lymphatics tissue connective (CVS) Regular tissue Adipose tissue Irregular [email protected]  Loose connective tissue Abundant cells of various types embedded in ground substance with scanty fibers Surrounds glands, blood vessels, beneath epithelia Loose areolar connective tissue Loose CT from mesentery of intestine [email protected]  Dense connective tissue Dense regular connective tissue: Dense irregular connective tissue: Contains few cells, randomly spread collagen Densely packed parallel arrays of fibers and relatively less ground substance collagen fibers (CF) with few fibroblast and ground substance Protects and supports organs, resists excessive stretching and distension Ex: tendons, ligaments, aponeuroses Ex: dermis of skin, organ capsule Dense regular CT in a tendon [email protected] Dense irregular CT in dermis [email protected]  Muscle Tissue ANT.3.3. Differentiate the microscopic anatomy of smooth, skeletal and cardiac muscle types. [email protected]  Muscle Tissue Muscle tissue is composed of cells that optimize the universal property of contractility Responsible for movements of body Change in shape and size of internal organs. [email protected] [email protected]  Skeletal muscle Skeletal muscle is invested by a dense collagenous connective tissue known as: The epimysium, which penetrates the substance of the gross muscle, separating it into fascicles. Each fascicle is surrounded by perimysium, a loose connective tissue. Each individual muscle fiber within a fascicle is enveloped by fine reticular fibers, the endomysium. The neurovascular structures travel in these interrelated connective tissue compartments. [email protected]  Basic structure of a muscle fiber Muscle cells are long cylindrical structures, hence commonly referred to as muscle fibers. The cytoplasm of muscle cells is called sarcoplasm (Gr. sarkos, flesh + plasma, thing formed) The smooth ER is the sarcoplasmic reticulum, and the muscle cell membrane and its external lamina are the sarcolemma (sarkos + Gr. lemma, husk). Longitudinal section Transverse section Syncytium- multinucleated, without any cell boundaries  Cardiac muscle Smooth muscle Cardiac muscle cells (cardiac myocytes) Elongated fusiform cells (called fibers) with finely tapered ends. are short cylindrical, striated cells with a Occurs as bundles or sheets in hollow centrally positioned single nucleus. They organs, such as the stomach, intestine, are attached to each other by blood vessels, and bladder. intercalated discs (arrows) to form a cardiac muscle fiber. [email protected]  Reference books Ross M. H, & Pawlina W. (2021). Histology: A Text and Atlas with Correlated Cell and Molecular Biology (8th ed.). Philadelphia, PA: Wolters Kluwer/Lippincott Williams & Wilkins. Available in LWW Health Library at URL: http://auamed.idm.oclc.org/login?url=http://meded.lwwhealthlibrary.com/book.aspx?bookid=2583 Standring, S. (2021). Gray’s Anatomy (42nd ed.) Philadelphia, PA: Elsevier. Available in ClinicalKey at URL: http://auamed.idm.oclc.org/login?url=https://www.clinicalkey.com/dura/browse/bookChapter/3-s2.0- C20170037291 Agur, A. M. R., Dalley,A. F., & Moore, K. L. (2019). Moore’s Essential Clinical Anatomy (6th ed.). Philadelphia: Wolters Kluwer. Available online in LWW Health Library at URL: http://auamed.idm.oclc.org/login?url=http://meded.lwwhealthlibrary.com/book.aspx?bookid=2610 Sadler T. W. et al. (2019). Langman’s Medical Embryology (14th ed.). Philadelphia, PA: Wolters Kluwer/Lippincott Williams & Wilkins. Available in LWW Health Library at URL: http://auamed.idm.oclc.org/login?url=http://meded.lwwhealthlibrary.com/book.aspx?bookid=2487 Wheater's Functional Histology, Sixth Edition. Junquiera basic histology text and atlas 15th ed [email protected]  Digital resources https://histologyguide.com/slideview/MH-150a- pituitary/13-slide-1.html (Source: T. Clark Brelje and Robert L. Sorenson) https://digitalhistology.org/tissues/epithelium/lining-and- covering/simple/simple-epithelium-11/ https://histology.medicine.umich.edu/ (Source: https://histology.medicine.umich.edu/) [email protected] Brick Exchange Histology of Epithelial Tissue (scholarrx.com) [email protected] BookWidgets Flash cards