Reproductive - Embryology Flashcards
1
Q
Important genes of embryogenesis
- Sonic hedgehog gene
- Produced…
- Function(s)
- Wnt-7 gene
- Produced…
- Function(s)
- Mutation(s) –>
- FGF gene
- Produced…
- Function(s)
- Homeobox (Hox) genes
- Function(s)
- Mutation(s) –>
A
- Sonic hedgehog gene
- Produced at base of limbs in zone of polarizing activity.
- Function(s)
- Involved in patterning along anterior-posterior axis.
- Involved in CNS development
- Mutation can cause holoprosencephaly.
- Wnt-7 gene
- Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb).
- Necessary for proper organization along dorsal-ventral axis.
- FGF gene
- Produced at apical ectodermal ridge.
- Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs.
- Homeobox (Hox) genes
- Involved in segmental organization of embryo in a craniocaudal direction.
- Hox mutations –> appendages in wrong locations.
2
Q
Early fetal development (552)
- Day 0
- Within week 1
- Within week 2
- Within week 3
- Weeks 3–8 (embryonic period)
- Week 4
- Week 6
- Week 10
A
- Day 0
- Fertilization by sperm, forming zygote, initiating embryogenesis.
- Within week 1
- hCG secretion begins around the time of implantation of blastocyst.
- Within week 2
- Bilaminar disc (epiblast, hypoblast).
- 2 weeks = 2 layers.
- Bilaminar disc (epiblast, hypoblast).
- Within week 3
- Trilaminar disc.
- 3 weeks = 3 layers.
- Gastrulation.
- Primitive streak, notochord, mesoderm and its organization, and neural plate begin to form.
- Trilaminar disc.
- Weeks 3–8 (embryonic period)
- Neural tube formed by neuroectoderm and closes by week 4.
- Organogenesis.
- Extremely susceptible to teratogens.
- Week 4
- Heart begins to beat.
- Upper and lower limb buds begin to form.
- 4 weeks = 4 limbs.
- Week 6
- Fetal cardiac activity visible by transvaginal ultrasound.
- Week 10
- Genitalia have male/female characteristics.
3
Q
Gastrulation
A
- Process that forms the trilaminar embryonic disc.
- Establishes the ectoderm, mesoderm, and endoderm germ layers.
- Starts with the epiblast invaginating to form the primitive streak.
4
Q
Embryologic derivatives:
Surface ectoderm
- Derivatives
- Craniopharyngioma
A
- Derivatives
- All Epidermis PALE
- Adenohypophysis (from Rathke pouch)
- Epidermis
- Parotid, sweat, and mammary glands
- Anal canal below the pectinate line
- Lens of eye
- Epithelial linings of oral cavity, sensory organs of ear, and olfactory epithelium
-
Craniopharyngioma
- Benign Rathke pouch tumor with cholesterol crystals, calcifications.
5
Q
Embryologic derivatives:
Neuroectoderm
A
- Brain (neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland)
- Retina and optic nerve
- Spinal cord
- Neuroectoderm—think CNS.
6
Q
Embryologic derivatives:
Neural crest ectoderm
A
- BAM, COPPP
- Bones of the skull
- Aorticopulmonary septum
- Melanocytes
- Chromaffin cells of adrenal medulla
- Odontoblasts
- PNS (dorsal root ganglia, cranial nerves, celiac ganglion, Schwann cells, ANS)
- Parafollicular (C) cells of thyroid
- Pia and arachnoid
- Neural crest—think PNS and non-neural structures nearby.
7
Q
Embryologic derivatives:
Mesoderm
- Derivatives
- Notochord
- Mesodermal defects
A
- Derivatives
- Muscle
- Bone
- Connective tissue
- Serous linings of body cavities (e.g., peritoneum)
- Spleen (derived from foregut mesentery)
- Cardiovascular structures
- Lymphatics
- Blood
- Wall of gut tube
- Vagina
- Kidneys
- Adrenal cortex
- Dermis
- Testes
- Ovaries
- Notochord
- Induces ectoderm to form neuroectoderm (neural plate).
- Its only postnatal derivative is the nucleus pulposus of the intervertebral disc.
- Mesodermal defects (VACTERL)
- Vertebral defects
- Anal atresia
- Cardiac defects
- Tracheo-Esophageal fistula
- Renal defects
- Limb defects (bone and muscle)
8
Q
Embryologic derivatives:
Endoderm
A
- Gut tube epithelium (including anal canal above the pectinate line)
- Most of urethra (derived from urogenital sinus)
- Luminal epithelial derivatives (e.g., lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, thyroid follicular cells)
9
Q
Types of errors in organ morphogenesis
- Agenesis
- Aplasia
- Hypoplasia
- Deformation
- Disruption
- Malformation
- Sequence
A
- Agenesis
- Absent organ due to absent primordial tissue.
- Aplasia
- Absent organ despite presence of primordial tissue.
- Hypoplasia
- Incomplete organ development
- Primordial tissue present.
- Deformation
- Extrinsic disruption
- Occurs after the embryonic period.
- Disruption
- 2° breakdown of a previously normal tissue or structure
- e.g., amniotic band syndrome
- Malformation
- Intrinsic disruption
- Occurs during the embryonic period (weeks 3–8).
- Sequence
- Abnormalities result from a single 1° embryological event
- e.g., oligohydramnios –> Potter sequence
10
Q
Teratogens
- When most susceptible
- Before
- After
A
- Most susceptible in 3rd–8th weeks (embryonic period—organogenesis) of pregnancy.
- Before week 3: all-or-none effects.
- After week 8: growth and function affected.
11
Q
Effects of these teratogens (medications) on fetus
- ACE inhibitors
- Alkylating agents
- Aminoglycosides
- Carbamazepine
- Diethylstilbestrol (DES)
- Folate antagonists
- Lithium
A
- ACE inhibitors
- Renal damage
- Alkylating agents
- Absence of digits, multiple anomalies
-
Aminoglycosides
- CN VIII toxicity
- A mean guy hit the baby in the ear.
- Carbamazepine
- Neural tube defects, craniofacial defects, fingernail hypoplasia, developmental delay, IUGR
- Diethylstilbestrol (DES)
- Vaginal clear cell adenocarcinoma, congenital Müllerian anomalies
- Folate antagonists
- Neural tube defects
- Lithium
- Ebstein anomaly (atrialized right ventricle)
12
Q
Effects of these teratogens (medications) on fetus
- Methimazole
- Phenytoin
- Tetracyclines
- Thalidomide
- Valproate
- Warfarin
A
- Methimazole
- Aplasia cutis congenita
- Phenytoin
- Fetal hydantoin syndrome: microcephaly, dysmorphic craniofacial features, hypoplastic nails and distal phalanges, cardiac defects, IUGR, intellectual disability
-
Tetracyclines
- Discolored teeth
- “Teethracyclines”
- Thalidomide
- Limb defects (phocomelia, micromelia—“flipper” limbs)
- Limb defects with “tha-_limb_-domide.”
- Valproate
- Inhibition of maternal folate absorption –> neural tube defects
- Valproate** inhibits folate absorption**
-
Warfarin
- Bone deformities, fetal hemorrhage, abortion, ophthalmologic abnormalities
- Do not wage warfare on the baby; keep it heppy with heparin (does not cross placenta).
13
Q
Effects of these teratogens (substance abuse) on fetus
- Alcohol
- Cocaine
- Smoking (nicotine, CO)
A
- Alcohol
- Common cause of birth defects and intellectual disability
- Fetal alcohol syndrome
- Cocaine
- Abnormal fetal growth and fetal addiction
- Placental abruption
- Smoking (nicotine, CO)
- A leading cause of low birth weight in developed countries
- Associated with preterm labor, placental problems, IUGR, ADHD
14
Q
Effects of these teratogens on fetus
- Iodine (lack or excess)
- Maternal diabetes
- Vitamin A (excess)
- X-rays
- Other
A
- Iodine (lack or excess)
- Congenital goiter or hypothyroidism (cretinism)
- Maternal diabetes
- Caudal regression syndrome (anal atresia to sirenomelia), congenital heart defects, neural tube defects
- Vitamin A (excess)
- Extremely high risk for spontaneous abortions and birth defects (cleft palate, cardiac abnormalities)
- X-rays
- Microcephaly, intellectual disability
- Other
- Fetal infections and certain antibiotics can also cause congenital malformations
15
Q
Fetal alcohol syndrome
- One of the leading causes of…
- Newborns of mothers who consumed significant amounts of alcohol during pregnancy have an increased incidence of…
A
- One of the leading causes of congenital malformations in the United States.
- Newborns of mothers who consumed significant amounts of alcohol during pregnancy have an increased 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
- Heart defects
16
Q
Twinning (555)
- Dizygotic twins
- Arise from…
- Will have…
- Monozygotic twins
- Arise from…
- The degree of separation between monozygotic twins depends on…
- The timing of this separation determines…
A
- Dizygotic twins
- Arise from 2 eggs that are separately fertilized by 2 different sperm (always 2 zygotes)
- Will have 2 separate amniotic sacs and 2 separate placentas (chorions)
- Monozygotic twins
- Arise from 1 fertilized egg (1 egg + 1 sperm) that splits into 2 zygotes in early pregnancy.
- The degree of separation between monozygotic twins depends on when the fertilized egg splits into 2 zygotes.
- The timing of this separation determines the number of chorions and the number of amnions.
18
Q
Placental development
- 1º site of…
- For each
- Fetal or maternal component
- Definition
- Cytotrophoblast
- Syncytiotrophoblast
- Decidua basalis
A
- 1º site of nutrient and gas exchange between mother and fetus.
- Cytotrophoblast
- Fetal component
- Definition
- Inner layer of chorionic villi.
- Cytotrophoblast makes Cells.
- Syncytiotrophoblast
- Fetal component
- Definition
- Outer layer of chorionic villi
- Secretes hCG (structurally similar to LH; stimulates corpus luteum to secrete progesterone during first trimester).
- Decidua basalis
- Maternal component
- Definition
- Derived from the endometrium.
- Maternal blood in lacunae.
19
Q
Umbilical cord
- Umbilical arteries
- Umbilical veins
- Umbilical artery and vein derivation
A
- Umbilical arteries (2)
- Return deoxygenated blood from fetal internal iliac arteries to placenta [A].
- Single umbilical artery is associated with congenital and chromosomal anomalies.
- Umbilical vein (1)
- Supplies oxygenated blood from placenta to fetus
- Drains into IVC via liver or via ductus venosus.
- Umbilical arteries and veins are derived from allantois.
22
Q
Aortic arch derivatives
- Develop into…
- 1st
- 2nd
- 3rd
- 4th
- 6th
A
- Develop into the arterial system.
-
1st
- Part of maxillary artery (branch of external carotid).
- 1st arch is maximal.
-
2nd
- Stapedial artery and hyoid artery.
- Second = Stapedial.
-
3rd
- Common Carotid artery and proximal part of internal Carotid artery.
- C is 3rd letter of alphabet.
-
4th
- On left, aortic arch; on right, proximal part of right subclavian artery.
- 4th arch (4 limbs) = systemic.
- 6th
- Proximal part of pulmonary arteries and (on left only) ductus arteriosus.
- 6th arch = pulmonary and the pulmonary-to-systemic shunt (ductus arteriosus).
23
Q
Branchial apparatus
- Also called…
- Composed of…
A
- Also called pharyngeal apparatus.
- Composed of…
- Branchial clefts
- Derived from ectoderm.
- Also called branchial grooves.
- Branchial arches
- Derived from mesoderm (muscles, arteries) and neural crest (bones, cartilage).
- Branchial pouches
- Derived from endoderm.
- Branchial clefts
-
CAP covers outside to inside:
- Clefts = ectoderm
- Arches = mesoderm
- Pouches = endoderm
33
Q
Cleft lip and cleft palate
- Cleft lip
- Cleft palate
- Comparison
A
-
Cleft lip
- Failure of fusion of the maxillary and medial nasal processes (formation of 1° palate).
-
Cleft palate
- Failure of fusion of the two lateral palatine processes or failure of fusion of lateral palatine processes with the nasal septum and/or median palatine process (formation of 2° palate).
- Comparison
- Cleft lip and cleft palate have two distinct etiologies, but often occur together.
34
Q
Genital embryology
- Female
- Development
- Mesonephric duct
- Paramesonephric duct
- Male
- SRY gene
- Sertoli cells
- Leydig cells
A
- Female
- Default development.
- Mesonephric duct degenerates
- Paramesonephric duct develops.
- Male
- SRY gene on Y chromosome—produces testisdetermining factor (testes development).
- Sertoli cells secrete Müllerian inhibitory factor (MIF) that suppresses development of paramesonephric ducts.
- Leydig cells secrete androgens that stimulate the development of mesonephric ducts.
35
Q
Genital embryology
- Paramesonephric (Müllerian) duct
- Mesonephric (Wolffian) duct
- Bicornuate uterus
A
- Paramesonephric (Müllerian) duct
- Develops into female internal structures
- Fallopian tubes, uterus, and upper portion of vagina (lower portion from urogenital sinus).
- Müllerian duct abnormalities result in anatomical defects that may present as 1° amenorrhea in females with fully developed 2° sexual characteristics (indicator of functional ovaries).
- Develops into female internal structures
- Mesonephric (Wolffian) duct
- Develops into male internal structures (except prostate)
- Seminal vesicles, Epididymis, Ejaculatory duct, and Ductus deferens (SEED).
- Bicornuate uterus
- Results from incomplete fusion of the paramesonephric ducts (vs. complete failure of fusion, resulting in double uterus and vagina).
- Can lead to anatomic defects –> recurrent miscarriages.
36
Q
SRY gene
- No Sertoli cells or lack of Müllerian inhibitory factor
- 5α-reductase deficiency
A
- No Sertoli cells or lack of Müllerian inhibitory factor
- Develop both male and female internal genitalia and male external genitalia
- 5α-reductase deficiency
- Inability to convert testosterone into DHT
- Male internal genitalia, ambiguous external genitalia until puberty (when increase testosterone levels cause masculinization)
37
Q
Male/female genital homologs (562)
- For each
- Dihydrotestosterone (male) –>
- Estrogen (female) –>
- Genital tubercle
- Urogenital sinus
- Urogenital folds
- Labioscrotal swelling
A
- Genital tubercle
- Dihydrotestosterone –> glans penis, corpus cavernosum, spongiosum
- Estrogen –> glans clitoris, vestibular bulbs
- Urogenital sinus
- Dihydrotestosterone –> bulbourethral glands (of Cowper), prostate gland
- Estrogen –> greater vestibular glands (of Bartholin), urethral and paraurethral glands (of Skene)
- Urogenital folds
- Dihydrotestosterone –> ventral shaft of penis (penile urethra)
- Estrogen –> labia minora
- Labioscrotal swelling
- Dihydrotestosterone –> scrotum
- Estrogen –> labia majora
38
Q
Hypospadias
A
- Congenital penile abnormality
- Abnormal opening of penile urethra on inferior (ventral) side of penis due to failure of urethral folds to close.
- Hypospadias is more common than epispadias.
- Fix hypospadias to prevent UTIs.
- Hypo is below.
39
Q
Epispadias
A
- Congenital penile abnormality
- Abnormal opening of penile urethra on superior (dorsal) side of penis due to faulty positioning of genital tubercle.
- Exstrophy of the bladder is associated with Epispadias.
- When you have Epispadias, you hit your Eye when you pEE.
