Connective Tissues IAS21 2024 PDF

Connective Tissues Part I: General Properties and Composition Dr Jada C.D. Lee Lecturer Learning Outcomes At the end of this video, you will be able to: ⎼ Outline the general functions and components of connective tissues ⎼ Take note of the composition of the extracellular matrix (ECM) which...

Connective Tissues Part I: General Properties and Composition Dr Jada C.D. Lee Lecturer Learning Outcomes At the end of this video, you will be able to: ⎼ Outline the general functions and components of connective tissues ⎼ Take note of the composition of the extracellular matrix (ECM) which is made up of ground substances and fibres General Functions of Connective Tissues - Exchange of materials - through blood vessels - Support and binding of other tissues together - e.g. Epithelia, blood vessels and nerves - Protection - to against infection, inflammation and immune response - Wound healing - involves collagen I and III - Regulating the behaviour of the cells - e.g. migration, proliferation and differentiation Connective tissue Characteristics of Connective Tissues ⎼ Origin of connective tissues: Mesenchyme (from mesoderm) in embryo Ground Extracellular substances matrix Connective Fibres tissue Resident cells Cellular components Transient cells Extracellular matrix Ground Substances ⎼ An amorphous gelatinous material The ground substance helps determine ⎼ It fills the spaces between fibres and cells the functionality of tissue ⎼ Consists of: 1) Hyaluronic acid - Polysaccharide - Viscous, slippery, good lubricant 2) Proteoglycan = Core protein + Glycosaminoglycan (GAG) - Traps water 3) Glycoprotein - Adhesion proteins - Links the components of the ground substance and to the surface of the cells e.g. fibronectin, laminin, osteopontin Extracellular matrix Fibrous Components There are 3 major types of fibres: ⎼ Collagen fibres (Type I collagen, most abundant) ⎼ Reticular fibres (Type III collagen) ⎼ Elastic fibres Wolfgang. Color atlas of cytology, histology, and microscopic anatomy. Extracellular matrix Fibrous Components: Collagen fibres ⎼ Most abundant type of connective tissue fibres ⎼ General function to provide flexibility with high tensile strength ⎼ Appears as wavy fibres with variable width ⎼ At least 29 of them have been classified Black arrow: the fibres oriented longitudinally Purple arrows: fibers in cross-section Lowrie. Histology: An essential textbook. Kierszenbaum, et al. Histology and cell biology: An introduction to pathology. Extracellular matrix Fibrous Components: Collagen fibres Common types of collagen: Collagen type Location in Body Formed by I Bones, tendons, dermis of the skin Fibroblasts Osteoblasts II Hyaline and elastic cartilage Chondroblasts III Form reticular fibers, present in skin, muscle and Fibroblasts blood vessel It is the first collagen type synthesized during wound healing and then is replaced by type I collagen IV Basement membrane-forming collagens Epithelial cells Find in basal lamina VII Epithelia, anchor epidermis to basal lamina Keratinocytes Fibroblasts  Extracellular matrix Fibrous Components: Collagen fibres ⎼ Involvement of collagen I and III in wound healing Normal skin Skin injury Proliferation phase Tissue remodelling without injury Neutrophils, as first Macrophages promote the Collagen type III is replaced by responders, remove reconstruction of the tissue the stronger type I collagen foreign material and structure by recruiting This is supported by bacteria from the wound fibroblasts and inducing macrophages, fibrocytes, and Followed by monocytes them to produce a myofibroblasts differentiating into provisional extracellular macrophages matrix (ECM), such as collagen III Suda et al. (2016) Extracellular matrix Fibrous Components: Reticular fibres ⎼ Very fine fibrils that make up the type III collagens ⎼ Not visible under H&E staining ⎼ Provides a supporting mesh framework for soft organs e.g. spleen, red bone marrow, liver, lymph node Reticular fibres in lymph node Special stains Silver: stains reticular fibres black/brown PAS: stains reticular fibres pink Pawlina, et al. Histology: A text and Atlas: With Correlated Cell and Molecular Biology. Silver stains (argyrophilic) for reticular fibres  Extracellular matrix Fibrous Components: Elastic fibres ⎼ Contains elastin that allows them to stretch and recoil (via cross-link molecules) ⎼ Branching fibres with a wavy appearance (when relaxed) ⎼ The fresh elastic fibres appear yellow ⎼ Distribution: e.g. aortic wall, larynx, ligamentum flavum in the vertebral column  Extracellular matrix Fibrous Components: Elastic fibres Mesentery Elastic artery BV: Blood vessels E: Elastic fibres C: Collagen fibres Pawlina, et al. Histology: A text and Atlas: With Correlated Cell and Molecular Biology. Extracellular matrix Fibrous Components: Elastic fibres Marfan Syndrome ⎼ An autosomal dominant disorder ⎼ Inherited defect in the gene encoding the protein fibrillin-1 ⎼ Predominant in aorta, skin, ligaments ciliary zonular fibres of the lens Patient with Marfan syndrome from McKusick VA: Heritable Disorders of Connective Tissue, 4th ed. St. Louis, Mosby, 1972. Connective Tissues Part II: Cellular Components in Connective Tissues Dr Jada C.D. Lee Lecturer Learning Outcomes At the end of this video, you will be able to: ⎼ Outline the major cell types present in connective tissue and their functions Components of Connective Tissues Ground substances Extracellular matrix Connective Fibres tissue Resident cells Cellular components Transient cells Cells of Connective Tissues Resident Connective Tissue Cells Transient Connective Tissue Cells 1. Fibroblast 1. Macrophage 2. Adipocytes 2. Lymphocytes 3. Mesenchymal stem cells 3. Mast cells 4. Plasma cells 5. Granular leukocytes e.g. neutrophils, eosinophils, basophils  Cells of Connective Tissues Resident Cells: Fibroblasts Fibroblasts ⎼ Most common cell types in connective tissue ⎼ Fibrocytes: a less active form ⎼ Functions: - Synthesizes the collagen, elastic and reticular fibres, and the ground substance of ECM - Response to tissue damage and synthesize new matrix Activated fibroblasts G: Golgi Apparatus; Pawlina, et al. Histology: A text and Atlas: rER: Rough endoplasmic With Correlated Cell and Molecular Biology. reticulum  Cells of Connective Tissues Resident Cells: Adipocytes ⎼ Cells contain a single lipid droplet which nuclei squeezed to the periphery ⎼ There are 2 types: - Unilocular adipose tissue (white) Unilocular adipose tissue - Multilocular adipose tissue (brown) ⎼ Functions: Synthesis and storage of fat, for endocrine and thermal regulation Multilocular adipose tissue Gray, H. et al. Gray's anatomy: The anatomical basis of Clinical Practice. Cells of Connective Tissues Resident Cells: Adipocytes Site of White Adipose Tissue in Adult Humans Unilocular adipose tissue Site of Brown Adipose Tissue in Adult Humans Raafat AbdRaboh et al. (2020) Multilocular adipose tissue  Cells of Connective Tissues Transient Cells: Macrophage ⎼ Phagocytic cells derived from monocytes in blood Mitochondria ⎼ Either fixed or transient ⎼ Functions: Phagocytes pathogen, dead Nucleus cells and red blood cells; defence and immune response Lysosome Pawlina, et al. Histology: A text and Atlas: With Correlated Cell and Molecular Biology.  Cells of Connective Tissues Transient Cells: Macrophage ⎼ Macrophages as antigen-presenting cells Major histocompatibility complex (MHC) Pawlina, et al. Histology: A text and Atlas: With Correlated Cell and Molecular Biology. Cells of Connective Tissues Transient: Mast Cells ⎼ Contain numerous secretory granules, very dense and obscure the nucleus ⎼ Cellular granules contain vasoactive and immunoreactive substances e.g. histamine & heparin ⎼ Functions: Mediate inflammation and allergic reactions Pawlina, et al. Histology: A text and Atlas: With Correlated Cell and Molecular Biology.  Cells of Connective Tissues Transient Cells: Plasma Cells ⎼ Developed from the B-lymphocyte after activation ⎼ Oval in shape ⎼ Cells with prominent Golgi apparatus and rER ⎼ Nucleus usually in an eccentric location with a clock-face nucleus ⎼ Active in antibody productions Pawlina, et al. Histology: A text and Atlas: With Correlated Cell and Molecular Biology. Connective Tissues Part III: Classification of Connective Tissues Dr Jada C.D. Lee Lecturer Learning Outcomes At the end of this video, you will be able to: ⎼ Outline different types of connective tissues ⎼ Differentiate the two major subtypes of connective tissue proper Types of Connective Tissues Connective tissue Embryonic connective Mature connective tissues tissues Specialized connective tissues Loose Dense Adipose Cartilage Bone Liquid connective connective connective tissue tissue Hyaline tissue Fibrocartilage Elastic Blood tissue Lymph Types of Connective Tissues - Based on composition, most connective tissue types can be divided into: df 1) Loose (areolar) connective tissue - more cells than fibres - e.g. lamina propria, mesentery, Wharton’s jelly dff 2) Dense connective tissue - more fibres than cells - Regular Vs Irregular  Types of Connective Tissues Loose (areolar) Connective Tissue ⎼ Fine network of collagen/elastic/reticular fibres with ground substance-filled space dff ⎼ Location: widely distributed under epithelia of body (lamina propria); dermis of the skin Lowrie. Histology: An essential textbook.  Types of Connective Tissues Loose (areolar) Connective Tissue Example: Fibroblasts Elastic fibre The mesentery of the intestine Collagen fibre Functions: - To support and binding, materials Intercellular space exchange, immune and filled with fluid and defense functions ground substance Lowrie. Histology: An essential textbook.  Types of Connective Tissues Dense Irregular Connective Tissue ⎼ Large amount of collagen Dermis of the skin fibres providing high tensile/ elasticity f ⎼ Fibres arranged in Blood random directions capillary ⎼ Locations: Fibrocyte e.g. the superficial connective tissue sheaths of muscle Fibroblast and nerves; the adventitia of large blood Collagen vessels; capsules of bundles various glands and organs Lowrie. Histology: An essential textbook. Types of Connective Tissues Dense Regular Connective Tissue ⎼ Dense parallel orientation of collagen fibres Dense regular connective tissue from a tendon ff ⎼ Aims to withstand tensile force in one direction ff ⎼ Poorly vascularized ff ⎼ Functions: - to attach muscles to bones; bones to bones e.g. tendons, ligaments Lowrie. Histology: An essential textbook. Types of Connective Tissues Mammary gland, human, H&E LCT: Loose Connective Tissue DICT: Dense irregular connective tissue GE: Glandular epithelium Pawlina, et al. Histology: A text and Atlas: With Correlated Cell and Molecular Biology.