W08 - MSK Intro; Joints Synovial Fluid Cartilage, Embryology, Ortho Hx and Examination Flashcards
Describe the functions of the skeletal system
A
Distinguish between different types of joints and link anatomical design to joint functions
FIBROUS
CARTILAGINOUS
SYNOVIAL
- greatest movement
- both hyaline and fibrocart.
Explain the structure and function of cartilage
Cartilage provides stability to the joint
ARTICULAR CARTILAGE (hyaline) - superficial layer: flat chondrocyte = collagen and glycoprotein (lubricin) - SHEER FORCES
- Transitional & deep layers: round chondrocytes = proteoglycans (aggrecan)
large water composition and changing collagen fibre orientation (parallel superficial to perpendicular bone)
* varying thickness =depending on Wt. bearing function
patella > interphalangeal joint
Indicate the mechanism of nutrition of cartilage
avasc. aneural and alymphatic thus the synovial fluid is produced by synvoial membrane (uptake and secretion and transport)
SYNOVIUM contain SYNOVIOCYTES. (Rich capillary network and NO EPITHELIAL LINING = direct exchange)
Describe the source and main constituents of synovial fluid
TYPE A SYNOVIOCYTE
- debris removal
- fluid prod
TYPE B SYNOVIOCYTE
- MAIN PRODUCER of fluid
=>
• viscous fluid
• hyaluronic acid & lubricin
• fluid component
Indicate the function of synovial fluid
synovial fluid lubricates in 3 ways:
- boundary lubrication: forms thin film boundary on articular surfaces via GLYCOPROT
- hydrodynamic: surfaces kept apart by liquid pressure, viscosity changes with load
- weeping lubrication: cartilaginous fluid squeezed into synovial cavity to increase fluid volume upon exertion of great force
+bursae FILLED WITH SYN.FLUID found around joint = reduce friction
* site of inflamm = BURSITIS affects mobility of joints
FIBROUS JOINTS examples
periodontal ligament
cranial sutures
interosseus membranes
CARTILAGINOUS JOINTS examples
Primary c. joint: only hyaline cartilage
- synchondrosis
e. g. epiphyseal plates
Secondary c. joint: hyaline & fibrocartilage
- symphysis
e. g. IV disc
SYNOVIAL JOINTS
Hinge (elbow)
Saddle (carpometacarpal)
Plane (acromioclavicular)
Pivot (atlantoaxial)
Condylar (metacarpophlangeal)
Ball & Socket (hip joint)
Initiation of Limb Budding
at end of 4 weeks, activation of mesenchymal cells in somatic lateral mesoderm
mesenchyme elongation, with ectoderm apex forming APICAL ECTODERMAL RIDGE
- homebox genes
- regional expression of HOX genes in limbs
e. g HOXd 9-13 gene expression in upper limb
Significance of APICAL ECTODERMAL RIDGE
Most distal of limb bud where adjacent to it contains rapid proliferation of cells (undiff.)
Mesenchymal cells proximal will differentiate into vasc., cartilage, and bone
When do hands and feet develop
end of 6th week = hand plates = digital rays
end of 7th week = digital rays = foot plates
4th-8thw = hand and feet dev
Birth defects
AMELIA - total absence
MEROMELIA - partial absence
PHOCOMELIA - some long bone absence
SYNDACTYLY - common defect of hand/foot (webbing), more common in foot, webbing
*THALIDOMIDE
Developmental Dysplasia of the Hip
Common after breech deliveries
or general joint laxity (multifactorial, associated w/ congenital dislocation of the hip)
Congenital Clubfoot
TALIPES EQUINOVARUS, common
sole of foot turned medially = foot inverted
- multifactorial
- abn positioning of fetus lower limb in utero
