REPRODUCTIVE- Embryology Flashcards
Where is Sonic Hedgehog gene produced?
At base of limbs in zone of polarizing acitvity
In what is Sonic Hedgehog gene involved?
In patterning along anterior-posterior axis
In CNS development
What can Sonic Hedgehog gene mutation lead to?
Holoprosencephaly
Where is Wnt-7 gene produced?
At apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)
What is the function of Wnt-7 gene?
Necessary for proper organization along dorsal ventral axis
Where is FGF gene produced?
At apical ectodermal ridge
What is the function of FGF gene?
Stimulates mitosis of underlying mesoderm, providing for lenghthening of limbs
What is the function of Homebox (Hox) genes?
Involved in segmental organization of embryo in a craniocaudal direction
What does Homebox (Hox) gene mutations lead to?
Appendages in wrong locations
During this day of early fetal development the fertilization by sperm is made, forming zygote, initiating embryogenesis
Day 0
When does hCG secretion begins?
Within week 1
What else happens during week 1 of fetal development when hCG begins?
Implnatation of blastocyst
What happens in fetal development during week 2?
Bilaminar disc (epiblast, hypoblast)
What happens in fetal development during week 3?
Trilaminar disc
Gastrulation
When do primitive streak, notochordm mesoderm and its organization, and neural plate begin to form?
Week 3 of fetal development
When does the embryonic period starts?
Weeks 3-8
What forms neural tube?
By neuroectoderm
When does the neural tube close?
By week 4
What happens during embryigenic period?
Closure of neural tube
Organogenesis
In which fetal development period is extremely susceptible to teratogens?
During week 3-8
Embryogenic period
When does the heart begin to to beat?
By week 4
When do upper and lower limb bud begin to form?
By 4th week
When is the fetal cardiac activity visible by transvaginal ultrasound?
By week 6
At this week Genitalia have mal/female characteristics
Week 10
Process that forms the trilaminar embryonic disc
Gastrulation
What is establish during Gastrulation?
Ectoderm, mesoderm, and endoderm germ layers
How is the evolution of Gastrulation?
Starts with the epiblast invagination to form the primitive streak
How is ectoderm classified?
Surface ectoderm
Neuroectoderm
Neural crest
From which structure does Adenohypophysis come forme?
From Rathke pounch
Derivates of surface ectoderm
Adenohypophysis, lens of eye, ephithelial linings of oral cavitym sensory organs of ear, and olfactory epithelium, epidermis, anal canal below the pectinate line, parotid, sweat and mammary glands
Characteristics of Craneopharyngioma
Benign Rathke pounch tumor with cholesterol crystals, calcifications
What derivates from Neuroectoderm?
Brain (neurohypophysis, CNS neuronsm oligodendrocytes, astrocytes, ependymal cells, pineal gland), retina and optic nerve, spinal cord
What you should think of Neuroectoderm?
CNS
What derivates from Neural crest?
PNS (dorsal root ganglia, cranial nerves, celiacganglion, Schwann cells, ANS), melanocytes, chromaffin cells of adrenal medulla, parafollicular (C) cells of thyroid, pia and arachnoid, bones of the skull, odontoblasts, aporicopulmonary septum
What you should thibk of Neural crest derivates?
Think PNS and non neural structures nearby
Derivates of Mesoderm
Muscle, bone, connective tissue, serous linings of body cavities (peritoneum), spleen (derived from foregut mesentery), cardiovascular structures, lymphatics, blood, wall of gut tube, vaginam kidneys, adrenal cortex, dermis, testes, ovaries
What does Notochord induces?
Induces ectoderm to form neuroectoderm (neural plate). Its only postnatal derivative is the nucleus pulposus of the invertebral disc
Mesodermal defects
Vertebral defects Anal atresia Cardiac defects Tracheo Esophageal fistula Renal defects Limb defects (bone and muscle)
Endoderm derivates
Gut tube epithelium (including anal canal above the pectinate line), most of urethra (derived from urogenital sinus), luminal epithelial derivates (eg. lungs, liver, gallbladder, pancreasm eustachain tube, thymus, parathyroid , thyroid follicular cells)
Absent organ due to absent primordial tissue
Agenesis
Absent organ despite presence of primordial tissue
Aplasia
Incomplete organ development; primordial tissue present
Hypoplasia
What is a deformation?
Extrinsic disruption
When do deformation occur?
After the embryonic period
Secondary breakdown of a previously normal tissue or structure
Disruption
What is an example of Disruption?
Amniotic band syndrome
What is a malformation?
Intrinsic disruption
When do malformations occur?
During the embryonic period (week 3-8)
What is Sequence?
Abnormalities result from a single primary embryological event
Example of sequence
Oligohydramnios → Potter sequence
When is more susceptible for Teratogens?
In 3rd- 8th weeks (embryonic period- organogenesis) of pregnancy
Before week 3 of pregnacy do teratogen effects happen?
All-or-non effects
What could be affected by teratogens after week 8 of pregnancy?
Growth and function affected
Teratogen effect of ACE inhibitors
Renal damage
What is the teratogen effect of Alkylating agents?
Absence of digits, multiple anomalies
Which drugs can cause CN VIII toxicity?
Aminoglycosides
Teratogen effect Carbamazepine
Neural tube defects, craniofacial defects, fingernail hypoplasia, developmental delay, IUGR
Which drug can cause Vaginal clear cell adenocarcinoma, congenital Mullerian anomalies?
Diethylstilbestrol (DES)
Which drugs can cause Neural tube defects?
Folate antagonists
What is the teratogen effect of Lithium?
Ebstein anomaly (atrialized right ventricle)
Which drug may cause Aplasia cutis congneita?
Methimazole
Teratogen effects of Phenytoin
Fetal hydantoin syndrome
What is the Fetal hydantoin syndrome?
Microcephaly, dismorphic craniofacial features, hypoplastic nails and distal phalanges, cardiac defects, IUGR, intellectual disability
Which drugs have the effect of Discolored teeth?
Tetracyclines
What is the teratogen effect of Thalidomide?
Limb defects (phocomelia, micromelia- flipper limbs
What is the teratogen effect of Valproate?
Inhibition of maternal folate absorption → neural tube defects
Teratogen effects of Warfarin
Bone deformities, fetal hemorrhage, abortion, ophthalmologic abnormalities
Can heparin be used during pregnancy?
Yes, because it does not cross placenta
Teratogen effect of Alcohol
Common cause of birth defects and intellectual disability; fetal alcohol syndrome
Which are the teratogen effects of Cocaine?
Abnormal fetal growth and fetal addiction; placental abruption
Important effects of Smoker (nicotine, CO) pregnant women
A leading cause of low birth weight in developed countries; associated with preterm labor, placental problems, IUGR, ADHD
This teratogen agent can cause Congenital goiter or hypothyroidism (creatinism)
Iodine (lack or excess)
Teratogen effects of Maternal diabetes
Caudal regression syndrome (anal atresia to sirenomelia) congenital heart defects, neural tube defects
What are the risks of Vitamin A (excess) in pregnant women?
Extremely high risk for spontaneous abortionsand birth defects (cleft palate, cardiac, abnormalities)
What are the teratogen risk of X ray exposure?
Microcephaly, intellectual disability
Which is one of the leading causes of congenital malformations in the USA?
Fetal alcohol syndrome
What is the risk for newborns of mothers who consumed significant amounts of alcohol during pregnancy?
Have increase incidence of congenital abnormalities, including intellectual disability, pre and postnatal developmental retardation, microcephaly , holoprosencephaly, facial abnormalities (smooth philtrum, thin upper lip, small palpebral fissures, hypertelorism), limb dislocation and heart defects
How do dizygotic twins arise?
From 2 eggs that are separately fertilized by 2 different sperm (always 2 zygotes)
Characteristics of dizygotic twins during the pregnancy
Have 2 separate amniotic sacs and 2 separate placentas (chorions)
From where do monozygotic arise?
From 1 fertilized egg (1 egg+ 1 sperm) that splits into 2 zygotes in early pregnancy
In what depends the degree of separation between monozygotic twins?
On when the fertilized egg splits into 2 zygotes
In monozygotic twins what does the timing of separation determines?
The number of chorions and the number of amnions
Percentage of monocygotic twins
20 %
Percentage of Dizygotic twins
80%
What is the most common result of Dizygotic twins?
Dichorionic diamniotic
Which is the most common result of cleavage in monocygotic twins?
75% Monochorionic, diamniotic
During the Monochorionic diamniotic in monocygotic twins… When and in which phase does this happen?
4-8 days in Morula to Blastocyst phase
Possible result of cleavage in monocygotic twins during 0- 4 days
Dichorionic diamniotic
Percentage of Dichorionic diamniotic in monocygotic twins
25%
In monocygotic twins what could be the result of cleavage during 8-12 days?
Monochorionic monoamniotic
What is the risk if monocygotic twins cleavege after day 13?
Monochorionic monoamniotic conjoined twins
What happens during day 0-4 of pregnancy?
2 cell stage to Morula
What happens during day 4-8 of pregnancy?
Morula to Blastocyst