Connective Tissue Refresher 2024 PDF

Connective Tissue Refresher Adapted from lecture by Dr. Amy Plotkin, MD, PhD Assistant Professor of Pathology Outline Connective tissue basics Extracellular matrix and its components Cells of connective tissue Types of connective tissue What is connective tissue?...

Connective Tissue Refresher Adapted from lecture by Dr. Amy Plotkin, MD, PhD Assistant Professor of Pathology Outline Connective tissue basics Extracellular matrix and its components Cells of connective tissue Types of connective tissue What is connective tissue? Provides a matrix that SUPPORTS Originates from and CONNECTS embryonic tissues and cells mesenchyme. together to FORM organs.  Tensile strength to resist pulling, stretching and tearing (provided by collagen) Connective Elasticity to allow return to tissue original shape after mechanical distortion (provided by elastic fibers) functions Volume (bulk/substance): provided by ground substance Types of connective tissue Loose connective Dense connective tissue tissue Biologic packing Physical support and wrapping Cartilage/bone are material specialized forms of dense connective tissue Components of connective tissue Connective tissue Extracellul ar matrix Cells Ground Protein Fibers Fibroblasts Adipocytes substance Glycosaminoglyc Collagen Elastin Proteoglycans Macrophages Mast cells ans (GAGs) Multiadhesive White blood cells glycoproteins  ECM Protein fibers Collagen Elastic fibers (strength) (stretchy)  Most abundant protein in the human body Main fiber type in most connective tissue ECM Function: tensile strength component: Collagen Fibers Secreted as a monomer by fibroblasts (and other cell types), polymerizes into fibrils in ECM 28 different types! ECM component: Elastic Fibers Allows tissues to be STRETCHED or DISTENDED and return to original shape. Skin, lungs, large arteries, bladder and others Elastic fibers are composed of elastin (secreted by fibroblasts) and fibrillin (a glycoprotein). Broken down by elastase, which is normally inhibited by α-1 antitrypsin Ex: lung tissue  breathing  Extracellular matrix Ground substance Glycosaminogly Proteoglycans cans (GAGs) Multiadhesive glycoproteins Ground substance Highly hydrated, transparent, semi-solid gel Fills the space between cells and fibers Allows diffusion of small molecules, acts as both a lubricant and a barrier to the penetration of invaders Mixture of three major kinds of macromolecules: Glycosoaminoglycans (GAGs), proteoglycans, multiadhesive glycoproteins Glycosaminoglycans (GAGs) Most predominant— hyaluronan (viscous, plays a role in Long polymers of Component of ground molecular diffusion repeating disaccharide substance through connective units tissue and in lubricating various organs/joints) Ground substance Proteoglycans—core protein with bound GAGs Various functions, associates with collagen fibers and other ECM components Multiadhesive glycoproteins Cell adhesion, have multiple binding sites for cell surface integrins and other matrix molecules  Connective tissue Extracellula Cells r matrix Ground Protein Fibers Fibroblasts Adipocytes substance Glycosaminoglyc Collagen Elastin Proteoglycans Macrophages Mast cells ans (GAGs) Multiadhesive White blood cells glycoproteins Cells of connective tissue are derived from mesenchyme Connectiv e tissue Cells Macrophag White Fibroblasts Adipocytes Mast cells es blood cells Fibroblasts Key cell in Secretes, maintains Can be active or Histology: long and Involved with connective tissue and recycles the quiescent thin, elongated with repair/scar matrix (secretes fine cytoplasmic formation collagen) processes and oval nuclei  Main cell in fat tissue Function: support, Adipocytes storage/metabolism Two main types: white and brown White adipose tissue Distributed throughout body nucleus pushed to side by lipid Roles Triglyceride storage/metabolism Structural fill and shock absorption Acts as a thermal blood insulator under skin vessels Brown adipose tissue Only small amounts in human adults Rich in mitochondria (makes it look pink on H&E stain) Generation of heat, plays a part in body temperature regulation The distinction between loose vs dense is based on Connective the amount of collagen present. Forms the supportive tissue stroma of organs proper Loose Dense Loose connective tissue Loose connective tissue Much ground substance Many cells and little collagen epithelium Supports microvasculature, nerves, and immune defense cells Example: lamina propria in digestive tract Dense connective tissue Dense irregular Little ground substance; few cells (mostly fibroblasts); much collagen in randomly arranged fibers Protects and supports organs; resists tearing Examples: dermis of skin, organ capsules, submucosa layer of digestive tract Dense regular Almost completely filled with parallel bundles of collagen; few fibroblasts, aligned with collagen. Provide strong connections within musculoskeletal system; strong resistance to force Examples: ligaments, tendons, aponeuroses, corneal stroma Summary of key points Function of connective tissue = support and connect other tissues; maintain water required for metabolite diffusion ECM > cells. ECM = large protein fibers and ground substance rich in various GAGs and water. Fibroblasts = major cell-type of CT proper, synthesizes and secretes most components of the ECM. Adipocytes = fat cells, store triglycerides; form adipose tissue. Summary of key points Collagen fibers are most important and abundant fiber of connective tissue (function = strength). Elastic fibers’ function = stretchiness Connective tissue proper is classified as loose or dense according to the amount of collagen and ground substance present. Loose connective tissue = more ground substance, less collagen, occupies areas adjacent to other types of epithelia. Dense irregular connective tissue = randomly distributed bundles of collagen (and some elastin), provides resistance to tearing Dense regular connective tissue = parallel collagen, great strength (but little stretch), prominent in tendons and ligaments