connective tissue

Connective TissueConnective Tissue

Loose, Dense, SpecializedLoose, Dense, Specialized

Basement MembraneBasement Membrane

Collagen – 68nM banding Collagen – 68nM banding pattern and thick pattern and thick bundles in cross sectionbundles in cross section

Mesenchymal Cells – Mesenchymal Cells – Primitive cells of Primitive cells of connective tissueconnective tissue

Dense, Irregular Connective Dense, Irregular Connective Tissue – More Fibers than Tissue – More Fibers than

cellscells

Irregular Connective Tissue Irregular Connective Tissue – Multiple Cells, fibers – Multiple Cells, fibers presentpresent

White Adipose White Adipose DevelopmentDevelopment

Mesodermal or neural crest derived mesenchymal cells Mesodermal or neural crest derived mesenchymal cells associated with adventitia of small venulesassociated with adventitia of small venules

Fibroblast-like cells determined as lipoblastsFibroblast-like cells determined as lipoblasts Lipoblasts deposit ECM and gather lipid, filling mature Lipoblasts deposit ECM and gather lipid, filling mature

cell and compressing nucleus, cytoplasm and cell and compressing nucleus, cytoplasm and organelles into characteristic adipocyte shapeorganelles into characteristic adipocyte shape

Isolated adipocytes spherical; may appear polyhedral or Isolated adipocytes spherical; may appear polyhedral or ovoid in tissues, surrounded by cytoplasm and a small ovoid in tissues, surrounded by cytoplasm and a small amt of CTamt of CT

Lipid is not membrane bound (unlike multilocular Lipid is not membrane bound (unlike multilocular adipocytes, which have multiple fat-containing adipocytes, which have multiple fat-containing vacuoles)vacuoles)

Mobilization of fat depends on neural or hormonal Mobilization of fat depends on neural or hormonal stimulusstimulus

Triglycerides mobilized to glycerol and fatty acids; FA Triglycerides mobilized to glycerol and fatty acids; FA enter capillary for use as energy sourceenter capillary for use as energy source

Adrenergic Receptors on Fat Cells

Hormone Sensitive Lipase

FA + Glycerol

Metabolism of Fat Metabolism of Fat from Adipocytesfrom Adipocytes

Adapted from Horn, 2006

Insulin

Adipose – H & EAdipose – H & E

Ultrastructure of Ultrastructure of AdiposeAdipose

Brown Adipose – Brown Adipose – Multilocular, Multilocular, ThermogenicThermogenic

Heat Generation Heat Generation Uncoupled From ATP Uncoupled From ATP PdtnPdtn Nervous system stimulationNervous system stimulation Lipid mobilized, fatty acid oxidizedLipid mobilized, fatty acid oxidized UCP-1 moves H+ across inner UCP-1 moves H+ across inner

mitochondrial membrane, mitochondrial membrane, dissipating proton gradient for ATP dissipating proton gradient for ATP pdtnpdtn

Energy freed as heatEnergy freed as heat

CartilageCartilage

Chondrocytes in an avascular Chondrocytes in an avascular extensively specialized matrixextensively specialized matrix

Weight bearing, shock absorbing, Weight bearing, shock absorbing, porousporous

Three kinds – Hyaline, Elastic, Three kinds – Hyaline, Elastic, FibrousFibrous

Differential ECM deposition aids in Differential ECM deposition aids in functionfunction

Hyaline CartilageHyaline Cartilage

Chondrocytes in isogenous Chondrocytes in isogenous groupsgroups

TM vs ITM reflects TM vs ITM reflects differential matrix differential matrix distributiondistribution

Ground Substance= Ground Substance= Collagen II, PG (HA, Collagen II, PG (HA, CSulfate, KerSulfate)CSulfate, KerSulfate)

Proteins (eg., tenascin, FN)Proteins (eg., tenascin, FN) Highly hydrated (assists in Highly hydrated (assists in

weight bearing)weight bearing) Model for Indirect Model for Indirect

(Endochondral) Ossification(Endochondral) Ossification Perichondrium = source of Perichondrium = source of

growth (DR connective growth (DR connective tissue)tissue)

Proliferation of Proliferation of chondrocytes may also be chondrocytes may also be via interstitial growthvia interstitial growth

Elastic CartilageElastic Cartilage

Characterized by Characterized by presence of elastin presence of elastin fibers in hyaline ECMfibers in hyaline ECM

Flexible, non-Flexible, non-calcifyingcalcifying

Surrounded by Surrounded by perichondriumperichondrium

External ear, External ear, eustachian tubes, eustachian tubes, epiglottis of larynxepiglottis of larynx

FibrocartilageFibrocartilage

Dense regular connective Dense regular connective tissue + hyaline matrixtissue + hyaline matrix

No perichondriumNo perichondrium IG and rows of IG and rows of

chondrocyteschondrocytes Fibroblast nucleii presentFibroblast nucleii present Intervertebral disks, Intervertebral disks,

symphysis pubis, articular symphysis pubis, articular disks of mandible and disks of mandible and sternum, meniscus of sternum, meniscus of knee, places where knee, places where tendon attaches to bonetendon attaches to bone

Resistance to shear force Resistance to shear force and compressionand compression

Cartilage growth and Cartilage growth and repairrepair Mesenchymal cellsMesenchymal cells Appositional and Interstitial growthAppositional and Interstitial growth Limited repair due to which three Limited repair due to which three

primary factors? primary factors? Aging – Limited repair, matrix Aging – Limited repair, matrix

calcifies, replaced by bone (how calcifies, replaced by bone (how does this impact function?)does this impact function?)