Connective Tissue Flashcards
Connective Tissue
Function: connecting (binding) cells and tissues
-connects epithelium, muscle, and nervous tissue
-structural support for tissues and organs
-aids in defense, protection, repairs
Connective Tissue Origin
Originates from mesenchyme that comes from embryonic mesoderm
General Composition
cells: resident cells and transient cells
extracellular matrix: hydrated gel-like ground substance with fibers embedded in it
fibers: provide tensile strength and elasticity
Resident CT Cells
fibroblasts/fibrocytes
macrophages
mast cells
adipose cells (fat)
pericytes
Fibroblast
-most abundant CT cell
-active cell, oval nucleus
-synthesize extracellular matrix: collagen, reticular, and elastic fibers
Fibrocytes
-small dense nucleus, less active cells (quiescent)
Macrophages (histiocytes)
-origin: blood monocytes
-shape varies when cells are active, round with dense/round-oval nucleus
-phagocytic for many different materials
Mast cells
-located around capillaries
-common in loose CT
-oval cell, membrane bound granules
-derived from progenitor cells from bone marrow
-granules contain inflammatory mediators
Adipose cells (fat)
-derived from mesenchyme
-synthesize/store triglycerides
-produce hormones (adipokines)
type 1: Unilocular (white)
type 2: multiocular (brown)
Unilocular adipose cells
-large cells
-store lipids as single droplets in cytoplasm
Multilocular adipose cells
-smaller cells
-lipids stored in multiple droplets in each cell
-nucleus is spherical and not against the plasma membrane
-contains more mitochindria
Pericytes (perivascular cells)
-partially surround endothelial cells of capillaries/small venules
-surrounded by own basal lamina
-characteristics of endothelial cells and smooth muscle cells
-multipotent: differentiate into other cells (endothelium, fibroblasts, vascular smooth muscle)
Transient CT cells
plasma cells
leukocytes
-lymphocytes
-eosinophils
-neutrophils
-basophils
plasma cells
-abundant in respiratory and digestive systems
-immune-activated B-lymphocytes
-manufacture antibodies
-small cells: basophilic due to abundant RER
-nucleus eccentrically placed, appears “clock face” due to heterochromatin
-function: synthesis/secretion of antibodies (immunoglobulins)
Leukocytes - white blood cells, enter CT during inflammation
-Lymphocytes: T cells, B cells, natural killer cells
-Eosinophils: attack parasites, moderate allergic reactions, phagocytose antibody-antigen complexes
- Neutrophils: phagocytic especially bacteria
-Basophils: release components that control inflammatory process
Extracellular matrix
-hydrated gel-like ground substance with fibers embedded in it
-Fibers: provide tensile strength and elasticity
-ground substance: resists forces of compression
Collagen fibers
-composed of collagen
-tough, nonelastic protein
- secreted by fibroblasts in CT Proper
-stain pink to reddish with H&E stain
Collagen Fibers (Types)
Reticular fibers
-type III collagen
-visualized with silver stains
-fine network of fibers closely associated with individual cells of certain organs (lymph node, spleen, liver, kidney, bone marrow)
Elastic Fibers
-slender, long, branching in loose CT
-found in bundles (ligaments) and sheets (walls large blood vessels)
-produced by fibroblasts of CT proper and smooth muscle cells of blood vessels
-composed of elastin proteins
-EX: nuchal ligament, cartilage, CT proper, vessels, lungs
Embryonic Connective Tissue (mesenchymal CT)
-present in developing embryo
-mesenchymal cells have pale cytoplasm and oval nucleus
-ground substance is amorphous with scattered reticular fibers
-may present in dental pulp adult teeth
Embryonic Connective Tissue (Mucous CT)
-loose, amorphous CT
-gel-type matrix primarily composed hyaluronic acid
-fibers: type I, type III collagen
-fibroblast present
-location: umbilical cord and embryonic subdermal CT
Connective Tissue Proper Loose (areolar)
-loose arrangement fibers and cells
-abundant gel-like ground substance
-contains: collagen, reticular and elastic fibers (also nerves and blood vessels)
-Location: deep epidermal layer skin, deep mesothelium body cavities, associated with blood vessels
Connective Tissue Proper (Dense irregular)
-more fibers, fewer cells, less ground substance
-collagen fibers bundles arranged randomly
-collagen fibers are coarse (large) and form meshwork
-fibroblasts located between collagen fibers
-location: dermis skin, nerve sheaths, capsules spleen, testes, ovary, kidney, lymph nodes
Connective Tissue Proper (dense regular collagenous)
-densely packed coarse collagen fibers arranged parallel
-little ground substance and few cells (mostly fibroblasts) are interspersed between collagen fibers
-EX: tendons and aponeuroses
Connective Tissue Proper (dense regular elastic)
-coarse (large) branching elastic fibers
-densely packed bundles elastic fibers
-fibroblasts present between fibers
-few collagen fibers present
-location: large blood vessels, ligamentum flavum vertebral column, nuchal ligament, vocal ligament
Connective Tissue Proper (reticular)
-consists reticular fibers composed type III collagen that synthesized by fibroblasts
-fibers form delicate meshwork with fibroblasts and other cells interspersed
-forms supportive network for parenchyma various organs: spleen, lymph nodes, liver, kidney, bone marrow
Unilocular Adipose CT (white fat)
-location: potentially within any loose CT, within most organs
-predominantly in certain locations: subcutaneous tissue, coelomic cavities, axillary/inguinal regions
Multilocular Adipose CT (brown fat)
-Locations: interscapular region, axilla, mediastinum, mesenteries, perirenal region
