Twins_lecture 9.pptx

Umbilical cord & TWINS Anatomy Unit  Objectives  Describe the development and structure of the umbilical cord   Describe the anomalies of the umbilical cord  Describe the definition, incidence, and causes of twins  Describe the types and...

Umbilical cord & TWINS Anatomy Unit  Objectives  Describe the development and structure of the umbilical cord   Describe the anomalies of the umbilical cord  Describe the definition, incidence, and causes of twins  Describe the types and differences between twins  Case scenario Which of the following best describes the placental components of dizygotic twins? (A) One placenta, two amniotic sacs, one chorion (B) One placenta, two amniotic sacs, two chorions (C) Two placentas, two amniotic sacs, one chorion (D) Two placentas, two amniotic sacs, two chorions (E) One placenta, two amniotic sacs, two chorions Umbilical cord  Cord like structure  Connects fetus to the placenta  Length: 50-60 cm.  Diameter: one cm.  Shape: Twisted because vein shorter than artery. False knots along its length. Amniotic membrane covers both surfaces.  Attachment to placenta: near the center of the fetal surface of placenta. Umbilical cord structure  Amniotic sheath.  Extra embryonic mesoderm of connecting stalk become loose and gelatinous (Wharton's jelly).  Umbilical vessels: 1. Two umbilical arteries: carrynon-oxygenated blood. 2. Left umbilical vein: carry oxygenated blood.  Remnant of vitello intestinal duct: disappear at 3rd month.  Definitive yolk sac: disappears at 5th month.  Allantois.  Intestinal loop of midgut (6-12 weeks). Umbilical Cord: after birth  Allantois obliterated to form median umbilical ligament.  2 umbilical arteries become occluded to form medial umbilical ligament.  Left umbilical vein become occluded to form ligamentum teres of liver. Umbilical vein Umbilical Arteries Umbilical Cord: Anomalies  Number: Two (double), three (triple).  Length : A. Very short cord:?? B. Very long umbilical cord: ??  Knots of umbilical cord: A. False knots: no significance. B. True knots: due to long umbilical cord and may be tighten and cause fetal death. Umbilical Cord: Anomalies  Attachment of umbilical cord Marginal attachment: attached away from the center Velamentous attachment: attached to amnion  Anomaly in structure of umbilical cord: Cause: one artery is absent due to agenesis or degeneration. Character: 15-20% of cardiovascular abnormalities. Umbilical Cord: Anomalies  Persistence physiological umbilical hernia (exophthalmos) The intestine is not reduced after 10 weeks TWINS Definition: delivery of more than one fetus. Incidence:  Twins: once every 85 pregnancy.  Triplets: once every 90 pregnancy.  Quadriplets: once every 90 pregnancies. Causes:  Hereditary.  Medical causes: due to administration of exogenous gonadotrophin to stimulate ovulation in women with ovulatory failure and also In vitro fertilization. Types:  1. Identical twins.  2. Non-identical twins. Dizygotic (inidentical, binovular or fraternal) twins  Cause: fertilization of two oocytes by 2 sperms  Incidence: 70% of twins.  Character: Same or different sex. Vary in physical appearance. 2 amnion, 2 chorions, 2 placentae chorion and placenta may be fused. Monozygotic Twins Cause: the fertilization of one oocyte (develops from one zygote) Incidence: 30% of twins Character: the same sex genetically identical similar in physical character and the difference occurs only by the environment. Monozygotic Twins: subtypes Separation in 2 cell stage Very similar as sex, blood groups, 2 placenta & 2 chorion & 2 amnion fingerprints, color of eye and hair Separation in inner cell mass Division of the inner cell mass 1 placenta & 1 chorion & 2 amnions Separation in bi-laminar disc Equally: 2 equal embryos 1 placenta & 1 chorion & amnion Un-equal: 1 large & 1 small Monozygotic Twins: Conjoined monozygotic twins (monsters or Siamse):  Cause: embryonic disc not divide completely.  Character: United in 1. Thoracic region (thoracopagus): the most common 2. Head region (craniopagus) 3. Dorsal (Pygopagus) or ventral body wall.  Case scenario Which of the following best describes the placental components of dizygotic twins? (A) One placenta, two amniotic sacs, one chorion (B) One placenta, two amniotic sacs, two chorions (C) Two placentas, two amniotic sacs, one chorion (D) Two placentas, two amniotic sacs, two chorions (E) One placenta, two amniotic sacs, two chorions https://next.amboss.com/us/article/Do01VS?q=umbilical+cord&m=eiXxqB#Z6d37cbe 3d3d65de034416abf50412d9c