Pregnancy & Placentation Lecture PDF

MD1020 Reproduction – Week 7 Assoc. Prof. Damien Paris ([email protected])  Placentation:  maturation & function  Maternal adaptations to pregnancy:  anatomical, metabolic & physiological  Sexual differentiation of the reproductive tract:  determination of sex  development of the re...

MD1020 Reproduction – Week 7 Assoc. Prof. Damien Paris ([email protected])  Placentation:  maturation & function  Maternal adaptations to pregnancy:  anatomical, metabolic & physiological  Sexual differentiation of the reproductive tract:  determination of sex  development of the reproductive tract  Explain the basic development, structure & function of the placenta - Sounds simple but lots in it, don't sleep on it.  Describe the impact of pregnancy & placental hormones on the maternal anatomy, metabolism & physiology of major body systems - Physiological changes to the body systems.  Apply principles of sexual differentiation to the development of the reproductive tract Development of the reproductive tract, what cells produce more hormones and downstream effect.  Pre-implantation (up to blastocyst-stage):  nutrients derived from uterine secretion (histiotrophic nutrition) transfer of nutrients from mother to the foetus. First 7 days that the blastocyst is derived is sollely from the uterine secretion. Diffusion across a few cells. INnercell mass is the most dense. - chorion -> chorion + chorion vilia + maternal decidua epithelium= placenta  Post-implantation (up to 3.2kg foetus):  nutrients derived from maternal blood (haemotrophic nutrition) more efficient, hameochorion placenta allows this to happen, occurs from week 2. Extraembryonic mesoderm forms. and turns into the foetal capillaries.  achieved via haemochorial placenta in humans  development starts from beginning of Week 2  fully functional by end of Week 12 after fertilization (nutritive, respiratory, excretory, immunological & endocrine functions established)  Transports nutrients from maternal circulation to foetus  Exchanges gases between foetus & mother CO2.  Excretes foetal waste into maternal compartment  Immunomodulatory role in maternal acceptance of foetus  Delivery of maternal antibodies to foetus (passive immunity)  Produces hormones that regulate maternal & foetal organs So the feotus has a automatic immune system at birth before it develops, occurs from placenta Gasttrulation completed. Maternal bloodfilled Lacuna Marieb & Hoehn 2010 Decidua basalis Maternal blood Chorionic villus Chorion Chorionic villus Umbilical cord & blood vessels Cytotrophoblast Extraembryonic mesoderm Red cells are the mesoderm Day 16 Periphery- hypoblast Mesoderm -> most becomes extraembryonic-> like a weed, gets out and covers everything. Week 4½  extra-embryonic mesoderm lines cytotrophoblast & with syncytiotrophoblast collectively form chorion & chorionic villi  chorion & villi of the embryo combine with maternal decidua basalis (stratum functionalis of endometrium) to form the true placenta chorion- foetal component cells differntiate into a decidual type of cell. Decidiat parcalus. - region in decidua capsulares.  Primary stem villi (11-13 days after fert): cytotrophoblast expands into syncytiotrophoblast projections how the chorionic vili forms- period when day 11-13 Starts to envaginate into the trophoblast areas. Cytroptropblasts dig into the syncytiotrophoblasts  Secondary stem villi (16 days): extraembryonic mesoderm proliferates into projection Proliferation of the extrembyronic mesoderm, have the syncytiotrophoblast layers bury in  Tertiary stem villi (21 days): mesoderm differentiates into connective tissue & blood vessels FOrms te blood cells. Have CT tissue forming, all encpasulated by the cytotrophblast and synciotophoblast which are directly in contact with the maternal blood. Can take oxygen and other things back into foetus. Placenta Chorionic villi Maternal arteries Decidua basalis Maternal veins Myometrium Umbilical cord Decidual pacalis Uterus Decidua capsularis epith make up capillary layers Chorionic villus containing fetal capillaries Maternal blood-filled lacuna What seperates the maternal and foetal blood Syncytrophoblast, cytotrophoblasts, vilus ct and foetal capillary endothelium-> Blood vessels (same thing) Week 13 Fetal arteriole Fetal venule Marieb & Hoehn 2010 Stratum basalis of endometrium Maternal portion of placenta (decidua basalis) Fetal portion of placenta (chorion) Umbilical arteries Umbilical vein Umbilical cord  villi become highly vascularised & project into maternal blood supply  maternal & foetal blood separated by syncytiotrophoblast, cytotrophoblast, villus connective tissue, & foetal capillary endothelium  chorion in decidua capsularis compressed → discoidal haemochorial placenta  placenta is fully functional by the end of week 12 after fertilization Direct contact stromal tissue is gone, have jsut direct contact with paternal blood and can exchange gases across the 3-4 layers to reach foetal circulation. passive diffusion Senger 2005 Most invasive: O2, CO2, nutrients & waste, etc. must diffuse across 3-4 tissue layers that separate foetal & maternal blood keeps endometrium going and nice thick robubst keeps the myometrium non contractile breaast tissue development progesterone Increase size of uterus helps breast tissue development helps stimulate relaxation of pelvis ligament and pubic symph oestrogen hCG Maintains pregnancy keeps progesterone going from the CL Stimulates corisol production via foetal H-P-adrenal axis CRH relaxin hCS/hPL Ttowards later stages it prepares birth canal by relaxing those ligament in the pelvis area hCT Decreasee glucose metabolism and uses fatty acid metabolism in mother, develops breast increase maternal metabolism Marieb & Hoehn 2010  hCG: maintains CL, suppresses maternal immune system  oestrogen: enlarges uterus, develops breasts & later relaxes pelvic      ligaments & pubic symphysis relaxin: later relaxes pelvic ligaments & pubic symphysis progesterone: maintains functional endometrium, quietens uterus, develops breasts, ↑respiratory tidal volume hCS/hPL: ↓glucose & ↑fatty acid metabolism in mother, develops breasts hCT: ↑maternal metabolism CRH: stimulates cortisol production via foetal H-P-adrenal axis  changes in anatomy, metabolism & physiology  influenced by placental hormones  ↑ vascularisation of reproductive organs  breast development & finally milk synthesis (progesterone, oestrogen, human chorionic somatomammotrophin/ human placental lactogen - hCS/hPL, prolactin)  dramatic uterine enlargement (oestrogen) estrogen and relaxin help the birth canal  fist-size to filling abdominal cavity  pressure on internal organs  alters centre of gravity → lordosis & backache  later, pelvis & ligaments relax & widen (relaxin, oestrogen)  waddling gate  considerable weight gain ~13 kg -> developing foetus =~3.3 kgs, however the weight gain occurs is assoicated with fluid retention, hunger Marieb & Hoehn 2010 (a) Before conception (b) 4 months (c) 7 months (d) 9 months foetus requires proteins, calcium, iron & energy for development  ↑ appetite (cortisol) needs calcium , iron , energy, helps cells differniate rapidly, number of adapation for the mother.  elevated fat storage & blood glucose levels Rise in cortisol during pregnancy = increase fat sotrage and blood glucose levels  ↑ fatty acid consumption & ↓ glucose metabolism in mother (hCS/hPL) increase in glucose in blood circulation but risks  free-up glucose in blood for foetal metabolism → 10% risk gestational diabetes  ↑ rate of maternal metabolism hCS (human chorionic thyrotrophin - hCT)  elevated calcium for foetal bone development helps breakdown nutrients -> more calcium available during development Wikipedia 2012 Marieb & Hoehn 2010  gastrointestinal system: progesterone and estrogen cause nausea and constipation  initial nausea (elevated progesterone, oestrogen)  reflux & constipation  urinary/renal system:  ↑ frequency & volume of urine  Na+ & water retention (renin, angiotensin II, aldosterone)  respiratory system: -> progesterone increases this process and increases Na+ and water retention  ↑ tidal volume: greater need of O2 (progesterone)  cardiovascular system:  ↑ blood volume 25-40%, & periodic ↑ cardiac output 20-40% (thyroxine, triiodothyronine) increase in red blood cells, t3 and t4-> from elevated progesterone Name the two chromosomes that determine sex in humans. Which one contains the gene responsible? Does anyone know the name of the gene? Intronless sex determining gene  sex of offspring depends on sex chromosomes (X & Y):  females have XX  males have XY  a single gene on Y chromosome, sex determining region on the Y (SRY), controls ‘maleness’ genetic sex (XY or XX) determines gonadal sex (testis or ovary) determines phenotypic sex (internal & external genitalia) influenced by hormones. stem cell Meiotic events Spermatogonium XY Type A daughter cell XY Mitosis Before birth XY Growth Meiosis I X Meiosis II X X Y Y Late spermatids X X Infancy and childhood (ovary inactive) Each month from puberty to menopause Secondary spermatocytes Early spermatids Y Y sex determined by sperm Spindle X X Y Y Primary oocyte XX Primary oocyte XX Primary oocyte 1 X-bearing 2 X-bearing 2 Y-bearing XX Meiosis I First polar body Spermatozoa XX Growth Primary spermatocyte Y Oogonium Mitosis Type B daughter cell XY XX Meiosis II of Polar body X X X Secondary oocyte Ovulation Sperm Meiosis II X X X X Polar bodies Second Ovum (all polar bodies one large functional gameteonly polar body degenerate) contain x bearing chromosome  during week 5 of embryo development gonadal tissue (gonadal ridge) develops → future ovaries or testes embyro -> sexual indifferent-> hasn't formed male or female structures yet  primordial germ cells migrate into gonadal ridge → future oogonia or spermatogonia ` germ cells-> are a stem cell derivative, the chromosome starts to act. Whether you form a testis or an ovary. ` SRY produces a testis TDF -> promotes testis and sertoli cells support  testis or ovary development regulated by the presence (XY) or absence (XX) of the SRY gene:  SRY produces testis determining factor (TDF) → testis & Sertoli cells  Sertoli cell produces müllerian inhibitory factor/anti-müllerian produces testerone in males hormone (MIF/AMH) → Leydig cells  Leydig cells produce testosterone → male genitalia sexually indifferent male TDF MIF (AMH) testosterone development of the testis itself. Produces the sertoli cells Melanin inhibitory factor Production of the leydig cells Attacks the Mesonephros and degernates them,**** fact check Mesonephric or wolfiian duct turns into the epipdidymis and the ductus or vas deferns Ongoing influence of testorone promotes testicular descent - starts from about six testosteronemonths of pregnancy and also promotes the developmetn of the penis and testicular decent into the scromtum and have at birtht eh male external genital male formation of reproductive organs female No SRY-> no testes determining factor. no TDF no MIF (AMH) Female waiting for the signa in the absence of testerone we get ovaries form ovarian tissue and no sertolli whihc leads to malorian inhibitor factor so te paramseone phric ducts forml No leydig cells no testerone No testicular descent Wolfian ducts degenerate no testosterone no testosterone genetic sex gonadal sex Influenced by three different factors Whether you inherit the Y chromsome If you do you get SRY testis released Anti mullarian hormone Helps sertolli cells and leydig cells-> testerone phenotypic sex Senger 2005 genetic sex (XY or XX) determines gonadal sex (testis or ovary) determines phenotypic sex (internal & external genitalia)