GENERAL EMBRYOLOGY 2GENERAL EMBRYOLOGY 2 • Folding of the embryo – 4th week of development• Folding of the embryo – 4th week of development • Development of extraembryonic structures – extraembryonic mesoderm, extraembryonic coelom, yolk sac, fetal membranes: amnion and chorion.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• 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 prezentace1 • Mature and full-term fetus, marks of mature fetus. 4th week – folding of the embryo (flexion) neural tubesomitesparaxial intermediate notochord sclerotome (base of vertebral arch) lateral arch) sclerotome (base of corpus vertebrae) dermatome, myotome aorta dermatome, myotome 3rd week primitive gut 4th weekaorta body of embryo Zápatí prezentace2 Differentiation of intraembryonic mesoderm intermediate lateral paraxialMesoderm lateral aorta dorsalis amniotic cavity intercellular spaces in lateral plate mesoderm intermediate mesoderm (nephrotome) neural tube somite Mesoderm: • paraxial mesoderm – thickened region of mesoderm along neural tube intraembryonic coelom • paraxial mesoderm – thickened region of mesoderm along neural tube • intermediate mesoderm (nephrotome) – in between paraxial and lateral mesoderm • lateral mesoderm – keeps sheet-like structure Differentiation of intraembryonic mesoderm – paraaxial (somites)– paraaxial (somites) Somite → Dermatome, Myotome, SclerotomeMyotome, Sclerotome 4 Sefton EM, 2019 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6449175/ Differentiation of intraembryonic mesoderm – intermediate and lateral– intermediate and lateral Intermediate mesoderm → urinary system (kidney, ureter), genital system (gonads, ducts, accessory glands) Lateral mesoderm (parietal and visceral layer) → dermis, hypodermis of ventral body parts, connective tissue and muscle of viscera, serous membranes, blood and lymphaticaccessory glands) serous membranes, blood and lymphatic vessels, spleen Zápatí prezentace5 Sefton EM, 2019 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6449175/ Amniotic cavity Neural plate Connecting stalk Nephrotom Intraembryonic Paraxial mesoderm Embryonic somatopleuraEMBRYO FOLDING Septum transversum Allantois Intraembryonic coelom Pericardial cavity Yolk sac Embryonic splanchnopleurasection plane Intraembryonic coelom – horseshoe shape Anterior and posterior neuroporus Oropharyngeal membrane Neural tube Ectoderm Cloacal membrane Neural tube Somite section plane Umbilical vein incorporation of yolk sac into primitive gut Dorsal aortae Communication between extra and intraembryonic coelom Heart primordium Primary brain vesicles Foregut Midgut Midgut Heart primordium Primitive Hindgut Cranial (head) fold Caudal (tail) fold Lateral folds Ductus omphalomesentericusPrimitive umbilical cord Yolk sac omphalomesentericus Yolk sac Moore et al., Before we are born, 2013, 8th ed. extraembryonic coelom = chorionic cavity Extraembryonic mesoderm yolk sac parietal layer = extraembryonic somatopleura + trophoblast → chorion = chorionic cavity yolk sac + trophoblast → chorion + amniotic ectoderm → amnion visceral layer = extraembryonic splanchnopleuraextraembryonic splanchnopleura + extraembryonic endoderm → yolk sac chorionic villichorionic villi • primary – cytotrophoblastic buds (day 10) covered with syncytiotrophoblastsyncytiotrophoblast • secondary - with extraembryonic mesoderm (days 12-13) • tertiary – vascularized extraembryonic• tertiary – vascularized extraembryonic mesoderm (days 17-18) Yolk sac, amniotic sac, fetal membranes - amnion, chorion chorion and secondary chorionic villi neural extraembryonic coelom (chorionic cavity) primary chorionic villi secondary chorionic villi neural tube primary chorionic villi connecting stalk umbilical cord extraembryonic splanchnopleura extraembryonic somatopleura cord Development of fetal membranes Different growth of chorionic chorionic villi primitive gut neural tube Different growth of chorionic villi toward decidua basalis (partially decidua marginalis) and toward decidua capsularis causes division of chorion into parts: neural tube connecting stalk causes division of chorion into parts: CHORION FRONDOSUM (toward decidua basalis – with villi) and CHORION LAEVE (smooth, without villi)LAEVE (smooth, without villi) amniotic cavity chorion frondosum cavity chorionic cavity chorion frondosumchorion laeve CHORION = extraembryonic mesoderm + cytotrophoblast + syncytiotrophoblast AMNION = extraembryonic mesoderm + amniotic ectoderm GROWTH OF AMNIOTIC AND CHORIONIC CAVITY AMNION = extraembryonic mesoderm + amniotic ectoderm GROWTH OF AMNIOTIC AND CHORIONIC CAVITY ChorionicChorionic cavityAmniotic cavity decidua • basalis • capsularis chorion frondosum • capsularis • marginalis • parietalis decidua basalis 4 weeks embryo 8 weeks embryo chorion frondosum chorion frondosum 4 weeks embryo 8 weeks embryo COMPARTMENTS OF PLACENTA: PARS FETALIS PLACENTAE – chorionic plate + chorionicPARS FETALIS PLACENTAE – chorionic plate + chorionic villi, intervillous space PARS MATERNA PLACENTAE = zona functionalis deciduae basalisbasalis • discoidalis Human placenta Full-term placenta • discoidalis • olliformis • hemochorialis maternal surface fetal surface ∅ 15-25 cm width 2-3 cm 15-20 cotyledonswidth 2-3 cm weight 500 g cotyledons POSITION OF PLACENTA IN UTERUS normal lateral wall normal wall uterineuterine fundus ventral/dorsal wall anomaly Anomalies of placenta Anomalies of chorionic villi (1 : 100 pregnancies) • mola hydatidosa• mola hydatidosa • chorionepitheliom Anomalies in location: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 increta (grown into myometrium) • placenta percreta (grown through myometrium) Anomalies of shape of placentaAnomalies of shape of placenta Funiculus umbilicalis (HE, HES, AZAN) • 50 – 60 cm long • 1,5 – 2 cm wide • amniotic ectoderm on the surface • jelly-like connective tissue• jelly-like connective tissue with umbilical vessels ductus allantoideus magn:2,5 from APERIO vein artery artery magn:2.5 artery Anomalies of umbilical cord - short (< 40 cm) True knot False knot- short (< 40 cm) - long (> 60 cm) (danger of strangulation or formation of true knots) True knot False knot formation of true knots) - true and false knots - absence of 1 umbilical artery (hypotrophic fetus) 1 21 2 3 Umbilical cord – placenta insertion 1 – insertio centralis chorion laeve 1 – insertio centralis 2 – insertio marginalis 3 – insertio velamentosa Multiple pregnancy twins 1:100 triplets 1:1002triplets 1:100 quadruplets 1:1003 amniotic cavities chorionic cavities DIZYGOTIC TWINS Dizygotic DIZYGOTIC TWINS • 2 spermatozoa fertilize 2 oocytes Dizygotic 2 oocytes • each embryo develops separatelyseparately (has its own amnion, chorion, and placenta) • twins can be of• twins can be of different sexes • resemblance of twins as• resemblance of twins as between siblings of different age separate amnion, chorion, placenta MONOZYGOTIC TWINS dizygotic monozygotic TWINS • 1 spermatozoon fertilizes 1 oocyte • splitting of embryo occurs 34% 65% 1% dizygotic monozygotic • splitting of embryo occurs during the further developmentdevelopment • arrangement of fetal membranes depends on stage on which splitting membranes depends on stage on which splitting occurs • twins are always• twins are always genetically identical and of the same sexesand of the same sexes MONOZYGOTIC separated on stage of 2 blastomeres TWINS dizygotic monozygotic on stage of 2 blastomeres • each of 2 blastomeres creates dizygotic monozygotic • each of 2 blastomeres creates 1 embryo • 2 blastocysts are formed • they implantate separately • fetal membranes are as in dizygotic twins: separate • fetal membranes are as in dizygotic twins: separate amnion and chorion (diamniotic,dichorial), and own placenta (diamniotic,dichorial), and own placenta separate amnion, chorion, placenta MONOZYGOTIC separated on stage of blastocyst TWINS dizygotic monozygotic on stage of blastocyst • embryoblast divides into 2 cell clusters before creation of germ dizygotic monozygotic clusters before creation of germ disc • trophoblast does not separate,• trophoblast does not separate, remains common • fetal membranes: separate• fetal membranes: separate amnion (diamniotic), common chorion (monochorial) and common placentacommon placenta • the most frequent (65 %) separate amnion, common chorion, common placenta MONOZYGOTIC separated on stage of bilaminar germ TWINS dizygotic monozygotic on stage of bilaminar germ disc • creation of 2 primitive dizygotic monozygotic • creation of 2 primitive streaks • fetal membranes are• fetal membranes are common – amnion, chorion, placenta (monochorial,placenta (monochorial, monoamniotic) • conjoined „Siamese“ twins• conjoined „Siamese“ twins develop in case of incomplete separation common amnion, chorion, placenta Length of pregnancy 38 týdnů = 266 dnůFertilization CONCEPTIONAL AGE 38 weeks = 266 days week 0 3 8 38 0 400 40 1st day of last MENSTRUAL AGE 40 weeks = 280 days menstruation = 10 lunar months preembryo embryo fetus Date of the 1st day of the last menstruation + 9 calendar months + 7 days preembryo embryo fetus Calculation of the expected date of delivery: Date of the 1st day of the last menstruation + 9 calendar months + 7 days Rule of Haase determine the age of fetus according its lengthdetermine the age of fetus according its length AGE (lunar month) CRL* (cm) • 3. • 4. 32 42 (the second power of l.m.) = 9 cm = 16 cm • 5. • 6. • 7. 52 6x5 (l.m. x 5) = 16 cm = 25 cm = 30 cm = 35 cm• 7. • 8. • 9. = 35 cm = 40 cm = 45 cm• 9. • 10. = 45 cm = 50 cm 1st month - 6-7 mm 2nd month – 2.5 cm *CRL = crown-rump length Fetal position in uteroFetal 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 ofwith 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 andFour characters of fetus arrangement in uterus are followed up and determined before delivery: • Situs• Situs • Positio • Praesentatio• Praesentatio • Habitus Situs relation: long axis of fetus body – long axis of uterus • longitudinal situs (parallel axes) - 99%• longitudinal situs (parallel axes) - 99% by head (caudally) or by pelvis • transversal situs• transversal situs (perpendicular axes) - 1% • oblique situs - unstable,• oblique situs - unstable, moves into longitudinal or transversal situs Positio relation: back (head) of fetus – uterine marginrelation: back (head) of fetus – uterine margin Second First lessSecond ordinary to the right, First less ordinary to the left,to the right, dorsally to the left, dorsally 1st2nd Second less First ordinary 1st2nd Second less ordinary to the right, ventrally First ordinary to the left, ventrally ventrally Praesentatio relation: part of fetal body – aditusrelation: part of fetal body – aditus pelvis • vertex (most• vertex (most frequent) • forehead, face, occiputocciput (1 %) • pelvic end and feet • trunk, shoulder Habitus relation: parts of fetal body to one anotherrelation: parts of fetal body to one another • regular= flexion of head, chin on• regular= flexion of head, chin on chest, limbs flexed in all joints, upper limbs crossed in front of the chest, lower limbs pressed tochest, lower limbs pressed to abdomen, fetus takes up the smallest possible volume • irregular = each other• irregular = each other Physiological fetus position in uterusPhysiological fetus position in uterus • longitudinal situs by• longitudinal situs by head • first ordinary• first ordinary position • praesentatio by head (vertex)head (vertex) • regular habitus Marks of full-term fetus Main characters • length (50-51 cm) • weight (3,000-3,500 g)• weight (3,000-3,500 g) • diameters of the head in norm • ♂ testes are descended in scrotum ♀ labia majora cover labia minora♀ labia majora cover labia minora Auxiliary charactersAuxiliary 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,• 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 otherare 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)- preterm (to 37th week) - full-term (38 – 40 weeks) - after term (more than 42 weeks)- after term (more than 42 weeks) • Mature fetus – relates to level of development: - mature - immature • Level of nutrition • hypotrophic• hypotrophic • eutrophic (weight 3,000 – 3,500 g, length 50 - 51 cm) • hypertrophic GENERAL EMBRYOLOGY 2GENERAL EMBRYOLOGY 2 ̶ Set of embryological schemes II ̶ ̶ Set of embryological schemes II ̶ Atlas of Cytology and Embryology – pages 76 – 81 ̶ ̶ ̶ ̶ Discussion ̶ 3 embryological schemes ̶ ̶ 3 embryological schemes Zápatí prezentace35