Zápatí prezentace1 GENERAL EMBRYOLOGY 2 • Folding of the embryo – 4th week of development • Development of extraembryonic structures – extraembryonic 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, praesentatio, 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. Zápatí prezentace2 4th week – folding of the embryo (flexion) Differentiation of intraembryonic mesoderm 3rd week 4th week neural tubesomitesparaxial intermediate lateral notochord aorta body of embryo primitive gut aorta sclerotome (base of vertebral arch) sclerotome (base of corpus vertebrae) dermatome, myotome Mesoderm: • paraxial mesoderm – thickened region of mesoderm along neural tube • intermediate mesoderm (nephrotome) – in between paraxial and lateral mesoderm • lateral mesoderm – keeps sheet-like structure intermediate lateral paraxial aorta dorsalis amniotic cavity intercellular spaces in lateral plate mesoderm intermediate mesoderm (nephrotome) neural tube intraembryonic coelom somite Mesoderm 4 Differentiation of intraembryonic mesoderm – paraaxial (somites) Somite → Dermatome, Myotome, Sclerotome Sefton EM, 2019 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6449175/ Zápatí prezentace5 Differentiation of intraembryonic mesoderm – intermediate and lateral Intermediate mesoderm → urinary system (kidney, ureter), genital system (gonads, ducts, accessory glands) Sefton EM, 2019 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6449175/ Lateral mesoderm (parietal and visceral layer) → dermis, hypodermis of ventral body parts, connective tissue and muscle of viscera, serous membranes, blood and lymphatic vessels, spleen Amniotic cavity Neural plate Septum transversum Connecting stalk Allantois Nephrotom Intraembryonic coelom Pericardial cavity Yolk sac Paraxial mesoderm Embryonic somatopleura Embryonic splanchnopleurasection plane section plane Umbilical vein incorporation of yolk sac into primitive gut Anterior and posterior neuroporus Oropharyngeal membrane Neural tube Ectoderm Cloacal membrane Neural tube Somite Dorsal aortae Communication between extra and intraembryonic coelom Primitive umbilical cord Primary brain vesicles Foregut Midgut Hindgut Cranial (head) fold Caudal (tail) fold Yolk sac Midgut Lateral folds Ductus omphalomesentericus Yolk sac EMBRYO FOLDING Moore et al., Before we are born, 2013, 8th ed. Intraembryonic coelom – horseshoe shape Heart primordium parietal layer = extraembryonic somatopleura + trophoblast → chorion + amniotic ectoderm → amnion visceral layer = extraembryonic splanchnopleura + extraembryonic endoderm → yolk sac extraembryonic coelom = chorionic cavity Extraembryonic mesoderm chorionic villi • primary – cytotrophoblastic buds (day 10) covered with syncytiotrophoblast • secondary - with extraembryonic mesoderm (days 12-13) • tertiary – vascularized extraembryonic mesoderm (days 17-18) yolk sac Yolk sac, amniotic sac, fetal membranes - amnion, chorion chorion and secondary chorionic villi neural tube extraembryonic splanchnopleura connecting stalk extraembryonic somatopleura extraembryonic coelom (chorionic cavity) primary chorionic villi umbilical cord Development of fetal membranes chorionic villi chorion frondosum primitive gut neural tube connecting stalk amniotic cavity chorionic cavity chorion laeve Different growth of chorionic villi toward decidua basalis (partially decidua marginalis) and toward decidua capsularis causes division of chorion into parts: CHORION FRONDOSUM (toward decidua basalis – with villi) and CHORION LAEVE (smooth, without villi) GROWTH OF AMNIOTIC AND CHORIONIC CAVITY CHORION = extraembryonic mesoderm + cytotrophoblast + syncytiotrophoblast AMNION = extraembryonic mesoderm + amniotic ectoderm decidua basalis 4 weeks embryo 8 weeks embryo Chorionic cavityAmniotic cavity chorion frondosum chorion frondosum decidua • basalis • capsularis • marginalis • parietalis COMPARTMENTS OF PLACENTA:  PARS FETALIS PLACENTAE – chorionic plate + chorionic villi, intervillous space  PARS MATERNA PLACENTAE = zona functionalis deciduae basalis • discoidalis • olliformis • hemochorialis Human placenta maternal surface fetal surface  15-25 cm width 2-3 cm weight 500 g 15-20 cotyledons Full-term placenta POSITION OF PLACENTA IN UTERUS lateral wall uterine fundus ventral/dorsal wall normal anomaly Anomalies of chorionic villi (1 : 100 pregnancies) • mola hydatidosa • chorionepitheliom Anomalies in location: • placenta praevia (causes bleeding in week 28) • absolute indication to CS • placenta accreta (attached to myometrium) • placenta increta (grown into myometrium) • placenta percreta (grown through myometrium) Anomalies of placenta Anomalies of shape of placenta Funiculus umbilicalis (HE, HES, AZAN) magn:2,5 magn:2.5 from APERIO vein artery artery • 50 – 60 cm long • 1,5 – 2 cm wide • amniotic ectoderm on the surface • jelly-like connective tissue with umbilical vessels ductus allantoideus - short ( 40 cm) - long ( 60 cm) (danger of strangulation or formation of true knots) - true and false knots - absence of 1 umbilical artery (hypotrophic fetus) True knot False knot Anomalies of umbilical cord 1 2 3 Umbilical cord – placenta insertion 1 – insertio centralis 2 – insertio marginalis 3 – insertio velamentosa chorion laeve Multiple pregnancy 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 as between siblings of different age 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 the same sexes 34% 65% 1% dizygotic monozygotic TWINS MONOZYGOTIC separated on stage of 2 blastomeres • each of 2 blastomeres creates 1 embryo • 2 blastocysts are formed • they implantate separately • fetal membranes are 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 divides into 2 cell clusters before creation of germ disc • trophoblast does not separate, 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 the 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 Haase 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.) = 9 cm = 16 cm = 25 cm = 30 cm = 35 cm = 40 cm = 45 cm = 50 cm *CRL = crown-rump length AGE (lunar month) CRL* (cm) 1st month - 6-7 mm 2nd month – 2.5 cm Fetal position in utero During fetal development, fetus is placed in amniotic sac, which is filled with amniotic fluid. The space of this sac decreases due to the 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 • Praesentatio • Habitus Situs relation: long axis of fetus body – long axis of uterus • longitudinal situs (parallel axes) - 99% by head (caudally) 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 1st2nd Praesentatio relation: part of fetal body – aditus pelvis • vertex (most frequent) • forehead, face, occiput (1 %) • pelvic end and feet • trunk, shoulder Habitus relation: parts of fetal body to one another • regular= flexion of head, chin on chest, limbs flexed in all joints, upper limbs crossed in front of the chest, lower limbs pressed to abdomen, fetus takes up the smallest possible volume • irregular = each other Physiological fetus position in uterus • longitudinal situs by head • first ordinary position • praesentatio by head (vertex) • regular habitus Marks of full-term fetus Main characters • length (50-51 cm) • weight (3,000-3,500 g) • diameters of the head in norm • ♂ 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 bones are hard, major and minor fontanelles are palpable and separated from each other • newborn cries and moves Mature and full-term fetus • Full-term fetus – relates to the length of pregnancy (menstrual age): - preterm (to 37th week) - full-term (38 – 40 weeks) - after term (more than 42 weeks) • 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 Zápatí prezentace35 GENERAL EMBRYOLOGY 2 ̶ Set of embryological schemes II ̶ Atlas of Cytology and Embryology – pages 76 – 81 ̶ Discussion ̶ 3 embryological schemes