Week 11 - Implantation and extra embryonic tissues

• 3 layers of uterus?


  from innermost to outermost: Endometrium, Myometrium, Perimetrium
• Which layer of endometrial layers shed in menstruation?

  Endometrial functionalis layer
• Underlying the functionalis layer?


  Endometrial basalis layer stimulates regeneration
• What is not part of endometrium but help with contraction and shedding

  Myometrium
• When does blastocyst implant into endometrium?

  Receptive (secretory phase)
• Endometrium cell types and functions?


  On the top: luminal epithelium: outermost layer forms contact with blastocyst

  glandular epithelium on the side: secretes factors to promote receptivity

  stromal cells: undergo terminal differentiation called decidualisation to transition from mesenchymal cells to more rounded, becomes highly secretory to prepare for pregnancy
• phases of menstrual cycle 


  Between ovarian and endometrial cycle

  Ovarian cycle:

  follicular phase: estrogen release from granulosa cells and leads to ovulation literal phase: CL produces progesterone

  Uterine cycle:

  Menses (shed endometrial functionalis layer)

  proliferation: regeneration and repair signals due to chemokines generated by basalis layer

  secretion (when blastocyst implants if have): secretion ability changes due to progesterone release by CL
• Key changes in endometrium across the menstrual cycle?

  Nnnn
• endometrium is only receptive of the blastocyst for….


  4-5 days receptive window or mid secretory phase: adhesive
• Pre receptive epithelium hallmarks??


  Non adhesive

  Thick glycocalyx layer

  polarised luminal epithelial cells which have tight junctions so blastocyst cannot implant
• endometrial receptivity steps?


  highly secretory to attract blastocyst to site of attachment, facilitate pregnancy

  relax tight junctions between luminal epithelial cells

  if fertilisation occurs, Trophectoderm oppose and attach to luminal epithelium
• Blastocyst how to implant 


  hatches from zone pellucida, trophectoderm adheres to endometrium
• Stages of blastocyst implantation 


  Blastocyst batches from zona pellucida

  blastocyst apposition to uterine wall: the luminal epithelium

  attachment of trophectoderm to uterine wall liminal epithelium

  Blastocyst invasion to uterine wall trophoblast differentiate from trophectoderm then invade between epithelial cells to form placenta.
• cell lineage of amnion, allantois and yolk sac

  Amnion is from inner cell mass

  Allantois Is from extra embryonic mesoderm

  yolk sac is from extraembryonic endoderm
• Function of allantois 


  Respiration, blood vessels differentiated from it
• amnion function 


  Protective buffer against injury
• Function of yolk sac in humans ?


  primordial germ cells arise from extraembryonic mesoderm, become visible in lining of yolk sac then migrate to gonads

  extra embryonic hematopoiesis
• Types of trophoblasts and functions?


  Syncytiotrophoblast: line placental villus single multi nucleated cell layer maximise surface area for maternal fetal exchange: Hormone production and nutrient exchange. Cytotrophoblast: fuse to form syncytiotrophoblast, Cell division and differentiate into extravillous trophoblast

  extravillous trophoblast: interstitial (anchor placenta to uterine wall) and endovascular (remodel maternal spiral arteries to increase blood supply to placenta and foetus by replacing lining of arteries to reduce pulsatility) both highly invasive
• Process of placental development in first trimester and pregnancy initiation?


  Stromal cells undergo decidualisation
• Any drug that cross the placenta must cross

  Syncytiotrophoblast
• What is semi allograft 


  Fetus considered immunologically distinct from mother
• Why mom does not reject fetus ?

  Placental and decidual cells produce factors to modulate maternal immune cells
• Immune cells in the decidua?

  70% Natural Killer Cells And 20% macrophages and 3-10% T cells.
• Maternal tolerance


  HLA G or MHC binds to decidual NK cells inhibiting its activity
• ectopic pregnancy risk factors and treatment options?


  Risk include smoking, IVF, pelvic inflammatory disease, endometriosis, chlamydia

  treatment include chemotherapy and removing fallopian tube
• Pre eclampsia risk factors and treatments?


  Shallow artery remodelling, activate anti angiogenic factors, hypertension, proteinuria protein in urine. No treatment
• Placenta produced human chorionic gonadotropin hormone in the first trimester

  Tested in pregnancy test