TENDONS
Tendons are anatomic structures interposed between muscles and bones transmitting the force created in the muscle to bone, and, in this way, making joint movement possible.
They are one of the strongest connective tissue in human body withstanding numerous mechanical forces.
They are viscoelastic structures exhibiting both elastic and viscous behaviour.
Paratenon covered tendons e.g., patellar, achilles tendons have rich vascular supply and thus heal better often injured due to trauma and most often fail
at the musculotendinous junction tendon-bone junction
Sheathed tendons e.g., hand flexor tendons less vascularized and have avascular areas that
receive nutrition by diffusion often injured due to laceration and at risk
for adhesions
Tendon composition Water Collagen ( type I and type III ) -> 90% 1-5% proteoglycan (decorin & aggrecan) 0.2% inorganic components copper,manganese
and calcium
Tendons are basically group of collagen bundles Separated by endotenon and covered by epitenon.
Tendon cells or Tenocytes Tenocytes are fibroblast-like differentiated
cells that form the mature tendon. Tenocytes synthesize the extracellular matrix, inducing assembly of early collagen fibers, which are the basic units of the tendon
TENOCYTES PROPERTIES
Are spindle shaped cells arranged in direction of muscle loading in arrays
Secrete collagen type I predominantly (95 %) but also secretes type III collagen in small
amounts
Help in healing of tendons
BIOMECHANICAL EFFECTS
Exercise strengthens tendons Immobilisation has detrimental effects. Tensile strength decreases with age. Heat decreases tensility/strength . Strength varies with
hydration,pH,tempreature. Tendons can bear 5-10% more tension as
compared to bone.
STAGES OF TENDON HEALING
Hemostasis Platelets initiate coagulation cascadeFibrin clot and fibronectin interaction leading to chemotaxis to stabilize torn tendon edges
5-15 min
Inflammation Fibroblasts produce type III collagenmacrophages help initiate healing and remodeling
1-7 days
Organogenesis Tissue modeling via large amounts of disorganized collagen and angiogenesis
7-21 days
Remodeling Tissue remodeling replacing type III collagen to type I collagen
Upto 18 mths
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