2Placenta Organ which provides nutrients & removes waste Complete by end of 3rd monthChorionic Villi (vascular projections from Chorion) are embedded in endometrium & allow nutrient / waste exchange, via active transport & diffusion. (16m2 SA)Attached to foetus via umbilical cordUmbilical veins, umbilical arteries (foetus)Uterine veins, uterine arteries (mother)
3Early Embryonic Period Immediately after fertilisation zygote divides (cleavage)Journey between uterine tube uterus (approx. 3-4 days)Cells divide but no new cytoplasm36 hrs. 1st cleavage is complete48 hrs. 2nd cleavage complete72 hrs. 4th cleavage completeCleavage continues forming a ‘blastocyst’ (approx. 5 days after fertilisation)Thin layer of cells surrounding a fluid filled cavity with one specific area of greater cell density (inner cell mass)
4Early Embryonic Period cont. Acquires nutrients from uterine fluidApprox. 7-8 days after fertilisation blastocyst (0.25mm diameter) sinks into endometrium (due to an enzyme) and becomes firmly attached (implantation)Inner cell mass faces towards endometrium, blastocyst is completely covered.Nutrients from endometriumIncreased oestrogen / progesterone from Corpus Luteum maintain endometrium & inhibit pituitary hormones
5Early Embryonic Period cont. Chorion secretes HCG, maintains Corpus LuteumSecretion starts at 2nd week preg 3rd month.Then placenta secretes oestrogen / progesterone & doesn’t need Corpus Luteum.
6Early Embryonic Period cont. first two months of pregnancy: embryoPrimary Germ layers:after implantation, inner cell mass breaks up into 3 layers (Primary Germ Layers)1. Ectoderm: (closer to body stalk)epidermis (top layer) of the skin, hair, nails, glands of skin, lens in the eye, receptor cells, epithelium in mouth, nose and anal canal, teeth enamel, nervous system, A. lobe of Pituitary gland, Adrenal medulla.
7Early Embryonic Period cont. Primary Germ layers:2. Mesoderm: (middle)Skeletal, smooth & cardiac muscles, connective tissues, lymphoid tissues, epithelium (top layers) of body / joint cavities, kidney, ureter, gonads, reproductive tracts, adrenal cortex & dermis of skin3. Endoderm (furthest from body stalk)Epithelium of A.C., bladder, urethra, gallbladder, pharynx, larynx, trachea, lungs, tonsils, thyroid, thymus glands, vagina.
8EARLY Embryonic Period cont. Embryonic MembranesLie outside the embryo: protect and nourishAmnion:Encases embryo, filled with amniotic fluidBy 8th day surrounds embryoProtection (shock absorber)Constant body tempFreedom of growth / movementYolk Sac:First site of red blood cell formationplacenta.
9EARLY Embryonic Period cont. Embryonic MembranesAllantois: joins with yolk sac to become umbilical cordChorion: outer cells of blastocyst with layer of mesodermal cellsAs amnion enlarges it fuses with Chorion. Chorion eventually becomes foetal placenta.
10Embryonic Period 4 weeks: 4mm Development of muscle segments on either side of the ‘spine’ tubeTail evident, brain & liver begins to form, heart forms and begins to beat.5 weeksArm / leg buds appear8 weeks3cm, 1gEnlarged head with eye slits & jaw, nose & ear lobesHands with fingers, feet with toesExternal sexual organs evident
11FOETAL Period 12 weeks 6cm Body straightens, upright posture Finger toe nails appear & hair appearsBone marrow with red blood cells formed16 weeks18 cm, 100gFingerprintsMovement of foetus120 – 160 / min (mum: 60 – 80 / min)Skeleton complete20 week25 cm, 300gBody covered with fine hairGripping reflexes
12FOETAL Period 24 weeks 27 -35 cm, 565 – 680 g Respiratory movements Digestive glands functioningEyebrows / eye lashes28 weeks38 cm, 1kg+Brain much larger with convolutionsIn males testes descend into scrotumAll systems functioning minus respiratory32 weeks41 – 45cm, 2.2 kgFat beneath skin36 – 40 weeks50 cm, 3.3 kgBoys approx 100g heavierEyes openWell formed noseFine body hair is shed
13Pregnant Mother Signs of Pregnancy Failure to menstruate Fuller, firmer, more tender breastsLarger, darker nipplesMorning sickness (nausea / vomiting)Increased urination frequency (pressure form uterus)Enlargement of abdomen.Changes to Mother during pregnancyno great change to a woman during embryonic periodduring lat foetal period, foetus has high demandsmother functions slow down nutrients stay in blood longerConstipationmothers blood vol increases (40%) & faster circulation (increased heart rate and vol)Increased urine production
14Treatment of infertility May be fixed by microsurgery, surrogacy, AID or ARTArtificial Insemination by Donor (AID)70% - 80% effectiveMale is sterile therefore semen is donated by an unknown man (generally physically similar).All donors are screened for STI’s and genetic diseases, mental problems and general health.Semen is injected into woman’s upper vagina around expected time of ovulation for 3-4 consecutive days. (generally for 3 months)SurrogacyWoman agrees to bear a child for a couple. (fertilised either naturally or artificially with male semen and surrogate egg OR using ART)
15Treatment of infertility Assisted Reproductive Technologies (ART)In vitro Fertilisation (IVF)takes ovum from mother, fertilise outside body, then transplant embryo to uterusGamete Intrafallopian transfer (GIFT)variation of IVFEggs and sperm immediately mixed together, then mixture immediately injected in to fallopian (uterine) tube.Most require women to take fertility drugs which increase number of eggs released by ovaries.Often more embryos are created than are needed so the excess are frozen. (may be used if initial is unsuccessful, donated to another couple, discarded or used for research)
16Treatment of infertility Assisted Reproductive Technologies (ART) cont.Intracytoplasmic Sperm Injection (ICSI)20-30% effectiveSingle sperm injected into a single egg and embryo transplanted into females uterus.May increase likeliness of birth defects.Donor Egg or EmbryoDonated egg is mixed with parents sperm and resulting embryo implanted into females Uterus.Could also be donated embryo.