Connective Tissue Flashcards
Derived from what embryonic tissue?
mesenchyme (middle germ layer)
ground substance
amorphous gel like substance. Part of extracellular matrix.
Components of ground substance (3)
Glycosaminoglycans (GAG), proteoglycans, adhesive glycoproteins
Glycosaminoglycans (GAG)
long inflexible unbranched polysaccharides
proteoglycans
proteins and GAG. attracts water to make tissue bulky and resist compression/pressure. Slow movement of cells.
Adhesive glycoproteins
large macromolecules with cell surface proteins (integrins). Fastens tissue components together.
Collagen
most prevalent protein in body. Forms various structures for different functions (cables, sheets, etc)
Collagen type 1
Location: dermis of skin, bone, capsules of organs, fibrocartilage, dentin, cementum, tendons. (places where there is siginificant force and tension.
Function: resists tension and pull
Collagen type II
Location: hyaline and elastic cartilage
Function: resistance to pressure
Collagen type III
AKA reticular collagen
Location: reticular fibers of spleen, liver, cardiovascular system, lungs, skin. (In organs having structural framework)
Function: structural support
Collagen type IV
Location: basal lamina (structure associated with epithelial cells)
Function: support and filtration
Collagen type V
Location: fetal tissues, placenta, dermis, bone, most interstitial tissues
Function: associated with type 1
Collagen type VII
Location: skin
Function: anchors epidermal basal lamina to underlying dermis
Collagen groups based on structures formed:
Fibrillar collagens: types I, II, III. Have subunits that aggregate to form large fibrils (can see on electron or light microscope)
Sheet forming collagens: type IV. To do with basement membrane. Subunits produced by epithelial cells. Major structural proteins of external laminae and basal lamina in epithelia
Linking/anchoring collagens (type VII): short collagens that link fibrillar collagens to one another and to components of ECM
Elastic fibers
seen mostly in organs subject to bending/stretching
thinner than type 1 collagen. Form sparse network interspersed with collagen bundles
protein cross link holds elastin aggregates together
Reticular fibers
mostly type III collagen
narrow, branching, don’t bundle
Stroma
scaffolding/framework. Supporting tissue of epithelial organ, tumor, gonads
Select fixed/resident cells
stay in connective tissue their whole lives
Connective tissue cellular components (6)
Fibroblasts, active fibroblasts, inactive fibroblasts, myofibroblasts, adiposytes, pericytes
Fibroblasts
originate locally from mesenchymal cells. Most abundant cell type. Active or quiescent state (fibrocytes)
active fibroblasts
found in close association with collagen bundles. elongated fusiform cells. Large, granular, ovoid nucleus; well defined nucleolus.
inactive fibrobalst
smaller than active. May differentiate into adipose cells, chrondrocytes, osteoblasts (under extreme stress/trauma)
myofibroblasts
modified fibroblasts that demonstrate characteristics of both fibroblasts and smooth muscle cells. Not easily distinguishable by LM. Abundant where wound healing takes place. Also in periodontal ligament. Bundles of actin filaments and dense bodies similar to those of smooth muscle cells.
Adipocytes
fully differentiated cells, function in synthesis, storage, and release of fat. Found throughout body in loose CT, concentrated along blood vessels. Masses form adipose tissue (15-20% of body weight)
Adipocytes of white fat
large spherical cells, polyhedral when in adipose tissue. Store fat in single droplet. Unicellular. Energy reserve
Adipocytes of brown fat
brown fat cells smaller and more polygonal than white fat. Stores fat in several small droplets. Lots of mitochondria so stains darker than white fat. Multicellular. Thermogenic, lose after infancy
pericytes
surround endothelial cells of capillaries and small venules. Have characteristics of smooth muscle cells and endothelial cells. Long processes coming off that associate with small capillaries
Transient cells
Come and go from CT. Plasma cells, leukocytes, macrophages, immune cells
Functions of CT (4)
- structural support
- medium for nutrient exchange
- aiding in defense and protection of body (via immune cells and ‘cushioning’)
- site for fat storage
Mesenchyme
derived mainly from mesoderm. Loosly packed stem cells in gel like extracellular matrix.
Loose CT
abundant ground substance, below lining of internal body cavity. Surrounds parenchyma of glands. Very pliable and flexible
Lamina propria
loost CT in GI tract that allows nutrients to diffuse to epithelium
Dense irregular CT
abundant collagen fibers, resistant to stress, tightly packed and not well organized.
location: dermis of skin, lymph node capsule
Dense regular CT (2 types)
Collagenous: abundant collagen fibers organized in parallel cylinders along lines of force/stress. Resistent to tensile stress.
Location: tendons, ligaments.
Elastic: abundant elastic fibers in parallel to form thin sheets. Resistant to tensile stress.
Location: large blood vessles
