Connective Tissue Flashcards
Functions of connective tissue
. Connecting framework of the body (continuous w/ basic tissue)
. Supportive framework of the body (cartilage, bones, ligaments, tendons)
. Protection and defense (immune/inflammatory responses, tissue repair)
. Fat storage
Stroma
Connective framework of body organs and glands
CT composition
ECM and cells
ECM components
Ground substance and fibers
Ground substance
Highly hydrated mixture of glycosaminoglycans, proteoglycans, and multiadhesive glycoproteins
Glycosaminoglycans (GAGs)
. Linear polymers of repeating disaccharide units
. Net. Charge from sulfate and carbonyl groups on sugars attracting water and form hydrated
Hyaluronic acid
. Largest GAG (10,000 kDa)
. Made of glucuronic acid and N-acetylglucosamine
. Axis of proteoglycan aggregate
. Not covalently bound to proteins
GAGS made of disaccharides w/ sulfate residues
. Chondroitin sulfate, heparin sulfate, dermatan sulfate, keratin sulfate
. Covalently bound to proteins
Proteoglycans
. Large molecules composed of a core protein w/ covalently bound GAGs
. Multiple proteoglycans bind via link proteins to hyaluronan core molecule to form giant proteoglycan aggregates
Multiadhesive glycoproteins
. Link ECM elements to cell surface
. Binding sites for various ECM elements
. Interact w/ cell surface receptors
Fibronectin
. Located on reticular lamina
. Main adhesion molecule of ECM
. Binding sites to heparin, collagen I, II, and III, fibrin and integrin (cell surface protein)
What binds to laminin in ground substance?
Collagen type IV (basal lamina component), heparin, and integrin (part of ECM)
Collagen
. Triple helix molecule rich in Gly, hydroxyproline, and hydroxlysine
.
Fibrillar collagen
. Type I, II, III collagen
. Collagen molecule formed by 3 polypeptides forming triple helix
. Aggregate and convalently cross-linked to form collagen fibers
. Type 1 fibers aggregate to make collagen bundles
Collagen fibrils
. Multiple molecules of collagen aggregated
. Aligned in regular arrangement
. See in EM
T/F you can only see collagen bundles in LM
TRUE
Reticular fibers
. Very thin type III collagen
. Form stroma around functional cells of organs
. Stain with silver stains (argophylic)
Nonfibrillar collagen
. Type IV
. Shorter triple-helical segments separated by nontrip;e-helical segments
. In basal lamina, binds to laminin
Scurvy
Hydroxylation of pro/lys in collagen synthesis requires vitamin C
. Deficiency creates this
. Inadequate wound healing and impaired bone formation
Osteogenesis imperfecta
Group of disorders characterized by bone fragility and laxity of ligaments
Ehlers-Danlos syndrome
Hyperelasticity of skin and hyper mobility of joints
. Vascular alterations causing varicose veins and artery rupture
. Collagen III defect
Fibrosis
Excessive collagen accumulation
Elastic fibers
. Networks of elastin molecules cross linked by desmosine and isodesmosine
. Stretch and recoil
. Interspersed w/ collagen bundles in bending organs
When are elastic fibers produced?
Embryonic development and adolescence
Marfan syndrome
. Autosomal dominant disorder characterized by weakening of elastic tissue
. Occular, skeletal, and cardiovascular issues
. Mutation in fibrillin gene causing excessive transforming growth factor beta release
. Elastic fiber issue where fibrillin that binds to elastin cannot bind TGF beta resulting in increased TGF beta levels making people long limbed
Fibroblasts
. Resident cells
. Synthesize ECM
. Spindle-shaped cells w/ elongated nuclei
. Cytoplasm not visible
. well developed rER and golgi EM
Secrete procollagen
Removal of terminal globular peptides and self assembly into polymeric fibrils
Myofibroblasts
. Resemble smooth muscle cells
. Aid in wound contraction
Macrophages
. Maintain self-renewal ability
. Express receptors for ECM components
. Modify ECM
. Hard to see in LM unless visible digested material
. Irregular nucleus, prominent golgi, lysosomes in EM
. Ingest old cells, debris, and ECM
. Immune defense
. Most transient with a few types of resident cells
Kupffer cells
Macrophages in liver
Microglia
Macrophages in CNS
Alveolar macrophages
In lungs
Osteoclasts
Macrophages of bone
How are macrophages derived?
Bone marrow derived monocytes that circulate inn blood then migrate into CT in response to inflammatory signals to differentiate
Macrophages function in immune defense
. Detect microbes and present antigens (proteins) to lymphocytes
. Produce cytokines
Cytokines
Biologically active substance that affect activity of other cells
Mast cells
. Visiting cells from bone marrow (differentiate once in CT)
. In skin and mucous membrane CT
. Absent in CNS
. Cytoplasm has basophilic granules w/ centrally located nucleus
. Holds Inflammation mediators
Inflammation mediators in mast cells
. Granules: heparin, histamine, chemoatractive mediators for cells of immune system
. Luekotriens are released from cell membrane
How mediators in mast cells play a role in allergic reactions
Regulates vascular permeability and bronchial smooth muscle tone
Plasma cell
. Visiting cell
. Product of B lymphocyte differentiation but not classified as lymphocyte
. Synthesize and secrete antibodies
. Basophilic cytoplasm w/ negative golgi, prominent nucleolus, clock face nucleus in LM
. EM good rER and golgi
Leukocytes
. Visiting cells (transient) the migrate into CT from blood
. Include lymphocytes and granulocytes
Adipocytes
. Fat storage
. Isolated or groups w/in loos and dense irregular CT
Unilocular adipocytes
. White
. 1 use droplet of lipid
. Look empty with thin ring of cytoplasm
Multilocular adipocytes
. Brown
. Many small lipid droplets and numerous mitochondria
. Smaller than white
. Heat producing
Mesenchyme
Unspecialized CT in embryo
Derived from mesoderm
Mostly ground substance
Mesenchymal cell
. Embryonic CT that can develop into other CT cell types (pleuripotent)
. Seen in developing tooth bud and umbilical cord
. Stellate-shaped w/ oval pale nucleus and big nucleolus
Mucous (mucoid) CT
. Embryonic CT in umbilical cord
. Formed by gelatin-like ECM
. Fibroblast morphology
. Ground substance (Wharton’s jelly) rich in hyaluronic acid
Loose CT
. Loose network of fibers and cell of different types
. Ground substance more than fibers
. Flexible, delicate
. Under epithelia for support )lamina propria)
. Cell types there are transient and migrate there in response to stimuli
. Site of inflammatory and immune rxns
. Also called areolar
Dense CT
. Abundant collagen fibers and few cells, mostly fibroblasts
. Irregular, regular, and elastic types
Dense irregular CT
. Fibers in different directions
. Woven into interlacing sheets that resist tensile stress from any direction
Dense regular CT
. Tendon
. Fibers in tightly packed, parallel bundles
. Sparse fibroblasts compressed between bundles
. Transmits mechanical forces over distance
Elastic CT
. Dense CT rich in elastic fiber
. Requires orcein to be differentiated from dense CT
. In lungs, skin, artery walls, and elastic ligaments
Reticular CT
. Has reticular fibers produced by reticular cells
. Reticular fibers enveloped by reticular cell cytoplasm,
. Delicate stroma of liver, bone marrow, and lymphoid organs
. Can see with silver stain
White adipose tissue
. Unilocular adipocytes
. Long term energy (15020% men body fat (20-25% woman body fat)
. Insulates, fills space, shock absorber
. Near loose CT
. Produce hormones, growth factors, and cytokines (leptin)
Brown adipose tissue
. Multilocular adipocytes
. Abundant mitochondria and blood capillaries
. Heat production
. Big in newborns (5% body mass)
