GENERAL EMBRYOLOGY 2 • Development of extraembryonic structures – extra-embryonic mesoderm, extraembryonic coelom, yolk sac, fetal membranes: amnion and chorion. • Development of the placenta. • Anomalies of the placenta and umbilical cord. • Multiple pregnancy – arrangement of fetal membranes. • The length of pregnancy, calculation of delivery date. • Fetus position in the uterus – situs, positio, presentatio and habitus. The length and weight of fetus during i.u. development. The rule of Haase. • Mature and full-term fetus, marks of mature fetus. Extraembryonic mesoderm •Derives from cytotrophoblast •cells fill cavity of blastocyst („sparse mesh“) •by fusion of clefts among cells - extraembryonic coelom between 2 layers of mesoderm (visceral and parietal) arises Parietal layer = extraembryonic somatopleura + cytotrophoblast – chorion + amnionic ectoderm – amnion Visceral layer = extraembryonic splanchnopleura is mesoblast of yolk sac (Heuser‘s membrane) extraembryonic coelom = chorionic cavity žv Extraembryonic mesoderm Extraembryonic coelom Development of chorionic villi • chorionic villi – consist of cytotrophoblast, which is covered with syncytiotrophoblast (day 10) • chorionic villi – with extraembryonic mesoderm ingrowing from chorionic cavity (day 12-13) • chorionic villi – with extraembryonic blood vessels in mesoderm /vascularized mesoderm/ (day 17-18) Yolk sac, amnionic sac, fetal membrane - amnion, chorion. chorion and chorionic villi neural tube skin navel extraembryonic splanchnopleura connecting stalk extraembryonic somatopleura extraembryonic coelom chorionic cavity cytotrophoblastic buds •Villi choriales are based over the whole surface of implanted blastocyst, resp. Its chorionic membrane •Different growth of villi toward decidua basalis (partially decidua marginalis) and toward decidua capsularis and decidua marginalis causes division of chorion into parts: • CHORION FRONDOSUM (toward decidua basalis – with villi) and cCHORION LAEVE (smooth, without villi) •Chorion frondosum and decidua basalis fuse together and creates placenta Development of fetal membranes chorionic villi chorionic cavity chorion frondosum chorion laeve primitive gut neural tube connecting stalk amniotic cavity amniová a chor GROWTH OF AMNIOTIC AND CHORIONIC CAVITY •CHORION = cytotrophoblast + syncytiotrophoblast + extrembryonic • mesoderm •AMNION = extraembryonic mesoderm + ectoderm Decidua basalis 4 weeks embryo 8 weeks embryo Chorionic cavity Amniotic cavity Chorion frondosum Chorion frondosum Human placenta -discoidea -olliformis -hemochorialis 15 - 25 cm width up 3 cm weight 500g placenta membrane separations - amnion and chorion membranes donošená placenta FULL TERM PLACENTA maternal surface (with cotyledons) umbilical 1 vein + 2 arteries maternal surface fetal surface umbilical vessels umbilical cord umbilical cord cotyledons figure •COMPARTMENTS OF PLACENTA: •c PARS FETALIS PLACENTAE – chorionic plate + chorionic •villi, intervilous space •c PARS MATERNA PLACENTAE = zona functionalis deciduae •basalis umístění placenty POSITION OF PLACENTA IN UTERUS lateral wall uterine fundus venrtal/dorsal wall Anomalies of placenta Anomalies of chorionic villi (1 : 100 pregnancies)  mola hydatidosa  chorionepitheliom Anomalies in location:  placenta praevia (causes bleeding in week 28)  placenta accreta (attached to myometrium)  placenta increta (grown into myometrium)  placenta percreta (grown through myometrium) Anomálie placenty Anomalies of placenta placenta duplex placenta triplex (several separate pieces) Anomalies of placenta placenta placenta placenta placenta membranacea fenestrata tripartita succenturiata (large, thin) (perforated) (several portions) (1 main + several accessory placentae) •Umbilical cord of full-term fetus: 50 – 60 cm long and 1,5 – 2 cm wide  amniotic ectoderm on the surface  jelly-like connective tissue with umbilical vessels: v. umbilicalis (1) + aa.umbilicales (2) Funiculus umbilicalis Anomalies of umbilical cord -short ( 40 cm) -long ( 60 cm) (danger of strangulation or formation of true knots) -true and false knots - -absence of 1 umbilical artery (hypotrophfic fetus) True knot False knot 1 2 3 Umbilical cord - placenta insertion 1– insertio centralis 2– insertio marginalis 3– insertio velamentosa chorion laeve Multiple pregnanacy twins 1:100 triplets 1:1002 quadruplets 1:1003 amniotic cavities chorionic cavities DIZYGOTIC TWINS •2 spermatozoa fertilize 2 oocytes •each embryo develops separately (has its own amnion, chorion and placenta) •twins can be of different sexes •resemblance of twins is as between siblings of different age TWINS Dizygotic separate amnion, chorion, placenta MONOZYGOTIC TWINS •1 spermatozoon fertilizes 1 oocyte •splitting of embryo occurs during the further development •arrangement of fetal membranes depends on stage on which splitting occurs •twins are always genetically identical and of same sexes 34 % 65 % 1 % dizygotic monozygotic TWINS MONOZYGOTIC separated on stage of 2 blastomeres •each of the first 2 blasto- •meres creates 1 embryo •2 blastocysts are formed •they implantate separatly •fetal membranes as in dizygotic twins: separate amnion and chorion (diamniotic,dichorial) and own placenta TWINS dizygotic monozygotic separate amnion, chorion, placenta MONOZYGOTIC separated on stage of blastocyst •Embryoblast divided into 2 cell clusters befor creation of germ disc •trophoblast does not divide, remains common •fetal membranes: separate amnion (diamniotic), common chorion (monochorial) and common placenta •The most frequent (65 %) TWINS dizygotic monozygotic separate amnion, common chorion, common placenta MONOZYGOTIC separated on stage of bilaminar germ disc • creation of 2 primitive streaks • fetal membranes are common – amnion, chorion placenta (monochorial, monoamniotic) •conjoined „Siamese“ twins develop in case of incomplete separation TWINS dizygotic monozygotic common amnion, chorion, placenta 38 týdnů = 266 dnů Date of th 1st day of the last menstruation + 9 calendar months +7 days Length of pregnancy preembryo embryo fetus Calculation of the expected date of delivery: Fertilization CONCEPTIONAL AGE 38 weeks = 266 days week 0 3 8 38 0 40 1st day of last MENSTRUAL AGE 40 weeks = 280 days menstruation = 10 lunar months Rule of Hasse determine the age of fetus according its length • 3. • 4. • 5. • 6. • 7. • 8. • 9. • 10. 32 42 52 6x5 (l.m. x 5) (the second power of l.m.) CRL** (cm) = 9 cm = 16 cm = 25 cm = 30 cm = 35 cm = 40 cm = 45 cm = 50 cm **CRL = crown-rump length AGE (l.m.)* *l.m. = lunar month Fetal position in utero During fetal development, fetus is placed in amnionic sac, which is filled with amnionic fluid. Space of this sac decreases due to growth of fetus. Therefore, fetus takes up the smallest possible volume, especially in the 3rd trimester. Four characters of fetus arrangement in uterus are followed up and determined before delivery: •Situs •Positio •Habitus •Presentatio Situs relation: long axis of fetus body – long axis of uterus •Longitudinal situs (paralel axes) - 99%, by head (kaudally) or by pelvis •Transversal situs (perpendicular axes) - 1% •Oblique situs - unstable, moves into longitudinal or transversal situs Positio Relation: back [head] of fetus – uterine margin Second ordinary to the right, dorsally First less ordinary to the left, dorsally Second less ordinary to the right, ventrally First ordinary to the left, ventrally 1st 2nd Habitus relation: parts of fetal body to one another • regular = flexion of head, chin on chest, limbs flexed in all joints, uper limbs crossed in front the chest, lower limbs pressed to abdomen, fetus takes up the smallest possible volume •irregular = each other Praesentatio relation: part of fetal body – aditus pelvis •vertex (most frequent) •forehead, face, occiput (1 %) •pelvic end and feet •trunk, shoulder Physiological fetus position in uterus •Longitudinal situs by head •First ordinary position •Regular habitus •Presentatio by head (vertex) Mature and full-term fetus •Full-term fetus – relates to the length of pregnancy (menstrual age) -preterm (to 37th week) -full-term (38 – 40 week) -after term(more then 42 week) - •Mature fetus – relates to level of development: -mature - immature •Level of nutrition •hypotrophic •eutrophic (weight 3,000 – 3,500 g, length 50 - 51 cm) •hypertrophic Marks of full-term fetus Main characters •length (50-51 cm) • weight (3,000-3,500 g) •diameters of the head •♂ testes are descended in scrotum, ♀ labia majora cover labia minora Auxiliary characters •fetus is eutrophic, subcutaneous fat is well developed •skin – rests of lanugo on shoulders and back only •eyelashes, brow, hair (several cm) are developed, nails overlap free end of fingers •skull bone are hard, major and minor fonticulus are palpable and separated from each other •newborn cries and moves GENERAL EMBRYOLOGY 2 Set of embryological pictures II