medical anatomy notes

1. MESODERM
GoogleClassroomcode:tkendnz

4. MESODERMALGERM
LAYER
•Paraxialmesoderm
•Intermediatemesoderm
•Lateral platemesoderm
•Somatic orparietalmesodermlayer
•Splanchnic orvisceralmesodermlayer

6. ParaxialMesoderm
•Paraxialmesodermbeginstobe
organizedintosegments.
•knownassomitomeres
• firstappearinthecephalic
regionoftheembryo,
•theirformationproceeds
cephalocaudally.

7. Somitomeres
•Eachsomitomereconsistsof
mesodermalcellsarrangedin
concentricwhorlsaroundthe
centeroftheunit.
•Intheheadregion,somitomeres form
inassociationwith segmentationof
theneuralplate intoneuromeresand
contribute tomesenchymeinthehead

12. Somites
•Fromtheoccipitalregioncaudally,somitomeresfurtherorganizeinto
somites.
•Thefirstpairofsomitesarisesinoccipitalregionat20thday
•Newsomitesappearincraniocaudalsequenceatarateof approximatelythree
pairsperdayuntil,attheendofthefifthweek, 42to44pairsarepresent
•Thereare4-occipital,8-cervical,12-thoracic,5-lumbar,5-sacral,and 8-10-
coccygealpairs.
•Thefirstoccipitalandthelastfivetosevencoccygealsomiteslater disappear,
whiletheremainingsomitesformtheaxial skeleton

13. Somite
Differentiation
•Whensomitesfirstformfrom presomitic
mesoderm,theyexistas aballof
mesoderm(fibroblastlike) cells.
•Thesecellsthenundergoaprocess of
epithelizationandarrange themselvesina
donutshapearound asmalllumen
•cellsintheventralandmedialwalls ofthe
somitelosetheirepithelial characteristics,
become mesenchymal(fibroblastlike)
again, andshifttheirpositiontosurround
theneuraltubeandnotochordand form
thesclerotomethatwill differentiateinto
thevertebraeandribs

14. SomiteDifferentiation
•Cellsatthedorsomedialand
ventrolateraledgesoftheupper
regionofthesomiteform myotome-
•myotome-musculaturefor the body
wallandmostofthelimb muscles
•Cellsbetweenthesetwogroups form
thedermatome
•Dermatome forms dermis and
subcutaneousareaof skin.

15. •Eachmyotomeanddermatomeretainsitsinnervationfromits segmentof
origin,nomatterwherethecellsmigrate.
• Hence,eachsomiteformsitsownsclerotome(thetendoncartilage andbone
component),itsownmyotome(providingthesegmental musclecomponent),and
itsowndermatome,whichformsthedermis oftheback.
•Eachmyotomeanddermatomealsohasitsownsegmentalnerve
component

16. IntermediateMesoderm
•Intermediatemesoderm,whichtemporarilyconnectsparaxial mesoderm
withthelateralplatedifferentiatesintourogenitalstructures.
•In upper thoracic and cervical regions this forms the nephrotomes, and in
caudallyregionsthisformsthenephrogeniccord

17. LateralPlateMesoderm
•Lateralplatemesodermsplitsinto
•parietal(somatic)and
•visceral(splanchnic)layers,
•intraembryoniccavity-inbetween
•Theparietallayeroflateralplatemesodermformsdermis,bonesand connective
tissueofbodywall.
•Mesodermcellsoftheparietallayersurroundingtheintraembryonic cavityform
serousmembranes,whichwill linetheperitoneal,pleural,andpericardialserous
membranesandsecreteserousfluid
•Hearttube

19. Mesodermderivatives
• Muscle(smooth,cardiac,skeletal)
• Boneandcartilage
• Heart,bloodvesselsandbloodcellsofthecirculatorysystem,microglia, andKupffer
cells
• Endotheliumofbloodandlymphvessels
• Connectivetissue,Dermisandsubcutaneouslayerof skin
• Duramater
• Spleen
• Kidney
• Adrenalcortex
• Testes,epididymis,ductusdeferens,seminalvesicle,ejaculatory duct
• Ovary,uterus,uterinetubes,superior1/3ofvagina
• Serousmembraneliningthebodycavities

20. •Mesenchyme-Aprimordialembryonicconnectivetissue,consisting ofaloose,
fluidextracellularmatrixandfewfibresandstellatecells. Canoriginatefromthe
mesodermorfromneuralcrest.foundasa componentofWharton'sjelly.
•Mesoderm- Themiddleofthe3germlayers.It givesrisetoall connective
tissues(exceptintheheadandneckregions),allbody musculature,blood,
cardiovascularandlymphaticsystems,mostof theurogenitalsystemandthe
liningofpericardial,pleuraland peritonealcavities.

21. Assignments
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•StudyMaterialsarepostedthere
•MCQassignmentandSAQassignmenttherepleasesubmitthoseto get
attendance
•Anyquestions/feedbackuhaveucanpost there

22. Thankyou