Notes in Asynchronous: Limb Embryology

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Published	01/03/2024	On day {{c2::20}}, the embryonic mesoderm splits into 3 different types of mesoderm: the {{c1::paraxial}}, {{c1::lateral}}, and the {{c1::intermediate…
Published	01/03/2024	The {{c1::paraxial}} mesoderm differentiates into somites, which eventually develop into the dermis, muscles, bones, and cartilage of the backThe {{c1…
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Published	01/03/2024	During limb development, {{c1::FGF8}} helps maintain undifferentiated mesenchyme in the distal portion of the limb
Published	01/03/2024	Limb buds have a mesenchymal core from the parietal layer of the {{c1::lateral plate}} mesoderm which is covered by a layer of cuboidal {{c2::ect…
Published	01/03/2024	The ectoderm at the distal portion of the limb thickens during development and forms the {{c1::apical ectodermal ridge (AER)}}
Published	01/03/2024	Cells furthest away from the AER (limb development) differentiate into the {{c1::cartilage}} and {{c1::muscle}}
Published	01/03/2024	Development of the limb proceeds from {{c1::proximal-distally::what direction}} and goes in 3 stages:Stylopod ({{c2::humerus and femur}})Zeugopod ({{c…
Published	01/03/2024	Limb growth proceeds in a proximal to distal fashion and is initiated by secretion of {{c1::FGF-10}} from the lateral plate mesoderm
Published	01/03/2024	The AER is confined to the top of the limb because {{c1::radical fringe}} (dorsal ectoderm) and {{c1::engrailed-1}} (ventral ectoderm) are s…
Published	01/03/2024	AER expresses {{c1::FGFs::what signals?}} which maintain the undifferentiated zone (tell the cells nearby to keep proliferating rapidly)
Published	01/03/2024	The flank mesenchyme cells produce {{c1::retinoic acid}} which is {{c2::antagonistic}} to FGFs and starts to cause differentiation of the cells close …
Published	01/03/2024	The differentiation front is a wave of differentiation that starts {{c1::proximally::proximally vs. distally}} and moves down toward the AER, causing …
Published	01/03/2024	{{c1::Thalidomide}} is a drug that was given to pregnant women to treat nausea and resulted in the children having partially or completely absent limb…
Published	01/03/2024	{{c1::WNT7}} is the gene that helps to establish the dorsoventral axis of the hand during development
Published	01/03/2024	{{c1::Erb-Duchenne}} palsy is caused by the injury to the brachial plexus which can be caused by birth trauma and results in forearm being medially ro…
Published	01/03/2024	{{c1::WNT7a}} gene (expressed in the dorsal ectoderm) works to establish the dorso-ventral axis by inducing expression of {{c2::LMX1}}, a transcriptio…
Published	01/03/2024	The anteroposterior axis of the limb develops under the influence of {{c1::sonic hedgehog::gene}}
Published	01/03/2024	Sonic hedgehog is secreted by the {{c1::zone of polarizing activity::what region?}} of the developing hand
Published	01/03/2024	The ulnar claw is caused by injury to the {{c1::ulnar}} nerve (C8, T1)
Published	01/03/2024	If you're near the zone of polarizing activity and you are under the influence of SHH, you will develop the {{c1::pinky}} finger or {{c1::5t…
Published	01/03/2024	If you have multiple zones of polarizing activity during limb development, you will develop {{c1::multiple digits}}
Published	01/03/2024	The {{c1::TBX5}} gene is critical for specification of the forelimb
Published	01/03/2024	{{c1::HOX}} genes are important in positioning limbs along the craniocaudal axis
Published	01/03/2024	Mutation in {{c1::TBX5}} causes Holt-Oram syndrome
Published	01/03/2024	{{c1::TBX4::gene}} is important in hindlimb development
Published	01/03/2024	Prior to ossificatoin of bone, chondrocytes form {{c1::hyaline cartilage models}}
Published	01/03/2024	In the first step of endochondral bone formation, mesenchyme cells condense and differentiate into {{c1::chondrocytes}} which form hyaline cartil…
Published	01/03/2024	Following hyaline cartilage model formation in bone development, {{c1::osteoblasts}} endter into the center of the bone, forcing the chondrocytes to t…
Published	01/03/2024	The {{c1::primary ossification}} centers are present by the 12th week of development, and this is where mineralization of the bone occurs
Published	01/03/2024	{{c1::Growth plates}} (epiphyseal plates) are not complemtely ossified at birth, and they allow the bone to grow until the plates close which is after…
Published	01/03/2024	Marfan's syndrome is caused by a mutation in the {{c1::FIBRILLIN}} gene
Published	01/03/2024	Osteogenesis imperfecta is caused by a defect in the production of {{c1::collagen}}
Published	01/03/2024	Somites come from the {{c1::paraxial}} mesoderm
Published	01/03/2024	Around the {{c1::third}} week of development, the somites start organizing in segments, accruing in a cranio-caudal fashion before epithelializing and…
Published	01/03/2024	The somites differentiate into 3 different structures during the 4th week of development:{{c1::Dermatome}}: dermis of the skin; {{c1::Myotome}}: …
Published	01/03/2024	The development of somites in a cyclic fashion depends on the expression of {{c1::WNT}} and {{c1::NOTCH}}
Published	01/03/2024	By looking at the # of somites in an embryo, you can estimate the {{c1::age}} of the embryo
Published	01/03/2024	As NOTCH protein levels {{c1::increase}}, the somites start {{c2::forming}}, causing negative feedback and for the NOTCH levels to decrease
Published	01/03/2024	NOTCH production is controlled by expression gradients of {{c1::retinoic acid}}, {{c1::FGF8}}, and {{c1::WNT3a}}
Published	01/03/2024	The notochord secretes {{c1::NOGGIN}} and {{c1::SHH}} which act on the sclerotome which expresses {{c2::PAX1}}, leading to vertebral formation
Published	01/03/2024	WNT proteins from the dorsal neural tube activate {{c1::PAX3}} which influences the development of the dermomyotome
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