Embryology Review

medmaestro's version from 2015-11-03 04:27




Question Answer
Genital system Ovaries develop in absence of Y chromosome
Germ cells in ovary develop fromYolk sac
Oogonia derived fromYolk sac
Primordial germ cells derived fromEctoderm
OogenesisSecondary oocyte arrest in metaphase of 2nd meiotic division, 1st polar body extruded during 1st meiotic division of primary oocytes
At birth, oocytes are in which stage of DevelopmentResting phase between prophase and metaphase of 1st meiotic division
Formation of primary ovary in female fetus takes place By10 weeks
Formation of primary follicles in human fetus is completed by18 weeks
Maximum number of oocytes in ovary during20 weeks of gestation
Vitelline membraneCell membrane of secondary oocyte
Polar body is located betweenZona pellucida and vitelline membrane
Polar bodies are formed duringOogenesis
In a female child at birth oocyte is in a stage ofProphase 1st meiotic
Primary oocyteMaximum in number in 5 month fetus, Is in prophase arrest
Arrest of primary oocyte byPeptide produced by follicular cells
Mature graafian follicle is less than18 mm
1st polar body releasedAccompanied by ovulation
Woman with cycles of 28 days with ovulation occurring around 14th day. When is the 1st polar body extruded24 hours prior to ovulation
Second polar body extrudedafter Fertilization
Female gamete remains inDiplotene stage


Question Answer
Gene coding for androgen receptors are located inLong arm of X chromosome
All spermatozoa carryXY chromosome
Chromosome number of primary spermatocyte44 XY
Meiosis occurs in males inSeminiferous tubulus
Does NOT undergo divisionSpermatid
Spermatogonium to mature spermatozoa (time taken for complete differentiation into mature sperm)74 days
Number of spermatids in second meiotic division4 spermatids
Number of spermatids from single spermatogonia512
Meiosis in spermatogenesis occurs inPrimary spermatocyte to secondary spermatocyte
Division of chromosomes in spermatogenesis inPrimary spermatocyte to secondary spermatocyte
In spermatogenesis,at which stage & which cell undergoes sex chromosome segregationMeiosis I, primary spermatocyte
Primary spermatocyte enters prolonged prophase of22 days
Spermatogenesis occurs at Temperaturelower than core body temperature
Core body temperature1 degree higher than rectal temperature, 1 degree higher than surface temperature,most accurate, best site of measurement is lower esophagus
Time taken for spermatogenesis61 days
Spermatogenesis is maintained byTestosterone, FSH, LH
Sperm after formation stored inEpididymis
Length of mature human spermatozoa50 – 60 micron
Sperms acquire motility inEpididymis
Sperm movement1-3 mm/min
Daily sperm production120 million/day
Mitochondria of sperm is seen inBody
Capacitance of sperms occurs inUterus
Sperm capacitation takes about6-8 hours
Correct order of pathway for spermStraight tubules-rete testis-efferent tubules
Sertoli cells play a key role inSpermiogenesis
Sertoli cells secreteInhibin
Supporting cells of testisSertoli
Mullerian regression in males is caused bySertoli cells
Primary action of inhibinInhibits secretion of FSH
Males and females show differences in age of onset of puberty. Difference in age of puberty amongst males may be explained byIncreased inhibin levels
Testosterone production is mainly contributed byLeydig cells
Cells NOT present in Seminiferous tubulesLeydig cells
Androgen is secreted byLeydig cells
Blood testis barrier is formed byThe blood-testes barrier is formed by tight intracellular junctions between adjacent Sertoli cells in the seminiferous tubule. The tight junctions of Sertoli cells form the blood-testis barrier, a structure that partitions the interstitial blood compartment of the testis from the adluminal compartment of the seminiferous tubules. The walls of seminiferous tubules are lined by primitive germ layer cells and Sertoli cells. The barrier is formed by tight junctions, adherens junctions and gap junctions between the Sertoli cells, which are sustentacular cells (supporting cells) of the seminiferous tubules, and divides the seminiferous tubule in a basal compartment (outer side of the tubule, in contact with blood and lymph) and an adluminal compartment (inner side of the tubule, isolated from blood and lymph).It is better termed as SERTOLI CELL BARRIER(SCB).


Question Answer
Microscopic examination of PAS stained histological section of a Graafian follicle demonstrates a bright reddish pink avascular ring around ovumZona pellucida
Zona pellucidaSurrounds morula, Barrier by fusion/fertilin, Surrounds ovum
Synthesis of zona pellucidaat Primary follicle stage
Zygote with zona pellucida reaches uterine cavity by4 days
Fertilized ovum reaches uterine cavity by4-5 days
After how many days of ovulation implantation occurs7-9 days
Fertilized ovum is embedded in endometriumat 8 day after fertilization
Zygote reaches uterine cavity as16 celled stage
Morula16 cell stage, Zona pellucida present
Morula formed after3 days
Implantation occurs at the stage ofBlastocyst
Zona hatching occurs5th day after fertilization
Zygote implanted in the 6 days after fertilization in the form ofBlastocyst
Second maturation division of human ovum occurs at the time ofFertilization
Commonest site of fertilizationAmpulla
Lionisation occur on16th day
By which day, placental circulation is established17th day
Maximum teratogenecity3-8 weeks after conception
Embryo is termed till8 weeks
Ovaries and testes distinguished by8 weeks
Fetal stage starts at9 weeks
Fetal movements established by11 weeks
Test tube baby produced bySperm and ovum fertilized in test tube and implanted
Amnion is present onFetal surface
Umbilical cordTwo arteries and one left vein, Umbilical vein carries
oxygenated blood, Right umbilical vein disappears


Question Answer
Gastrulation Establishes all three germ layers
Gastrulation occurs at3rd week
Events in 3rd week of development Gastrulation, primitive streak formation,notochord
Teratogenesis associated with gastrulationSirenomelia
Derivatives of Surface ectodermLens, Corneal epithelium, Conjunctival epithelium,Epithelium of lacrimal gland
Ectodermal originEnamel of teeth, Epithelial lining of Nasolacrimal duct,Anterior Pituitary
Structures arising from both Surface Ectoderm and NeuroectodermEye, Pituitary gland
Ectoderm Lens, Brain, Spinal cord
NOT derived from ectodermRetinal vascular endothelium
Not an ectodermal derivativeArrector Pilli
NOT derived from surface ectodermSclera, Anterior layer of iris
Neuroectodermal derivativesCiliary epithelium, Sphincter and dilator papillae
Develops from both ectoderm and mesodermAdrenal gland
MesodermalCiliary muscle, Iris, Ovarian tissue, Iris stroma, Ciliary
body, Choroid
Question Answer
Derivative of mesodermUreter, uterus and epididymis
NOT of mesodermal originDilators of iris
NOT derived from mesodermSphincter papillae
NOT a derivative of mesodermGall bladder
Paraxial mesoderm develops intoSomites
Paraxial mesoderm develops intoSclerotome
Ectoderm and endoderm approach each other in head and neck region during 4th weekPharyngeal membrane
Bilaminar germ disc formed byColumnar epiblast cells and cuboidal hypoblast cells
Buccopharyngeal membrane derived fromEctoderm, Endoderm
ChorionBoth layer of trophoblast with somatopleuric layer of extraembryonic mesoderm
Gland developed from EndodermPancreas
Endoderm formsLiver Parenchyma
Structure NOT arising from EndodermKidney
Fetal developmentGrowth in length is very fast in 3-5th month, Thumbs are formed in preaxial border, Upper limb develops before legs
NOT true about fetal development Fetus gains maximum weight in first trimester
Misexpression of which of the following homeobox genes alters position of forelimb during developmentHOXB8

Muscle development

Question Answer
Cardiac muscle develop fromsplanchnic mesoderm
Smooth muscle of dorsal aorta develops fromlateral plate mesoderm
Pupillary muscles areectodermal
Voluntary muscles of head are derived fromPARAXIALmesoderm
Tendons develop from sclerotome


Question Answer
Primitive streak 16th day
Closure of cranial neuropore25th day
Position of anterior neuropore in adultsStria
Closure of caudal neuropore27th day
Initiation and maintenance of primitive streakNodal gene
Formation of primitive streak occursBefore gastrulation
Primitive streakCephalic end of embryo is established before the formation of primitive streak,Henson node is the anterior tip of primitive streak
Notochord Prenotochordal cells intercalates with hypoblast, Cranial end forms first, Neurotenteric canal communicates amniotic and umbilical vesicle cavities,Extends from oropharyngeal membrane to primitive node
Notochord develops in 3rd week
Notochord formsNucleus pulposus of intervertebral disc
Neural plate inducersNotochord appearance, PGF upregulation, Prechordal
Question Answer
NOT a neural plate inducerHigh BMP
BMP 4 is inhibited byNoggin, Follistatin, Chordin
Closure of neural tube begins atCervical end
Features of neural developmentIn 3rd week neural groove is formed and neurulation completes in 4th week, Neural folds are first sign of brain development, Neuropores communicate with amniotic cavity, Cranial neural crest cells leave befor and truncal cells after neural tube closure
Angiogenesis in fetus is stimulated byVEGF, basic FGF, IL-8
Neural crest cells are deficient inSuperoxide dismutase, catalase
NOT true about neural crestNeural crest undergoes hypoblast to epiblast
Question Answer
Structures derived from neural crestPia, Dental papillae, Adrenal medulla, Schwann cells,Odontoblast, Melanoblast, Auerbach plexus and Meissner ganglion, Sympathetic ganglia, Dorsal root ganglia, Autonomic ganglia, Melanocyte, Dentine
NOT derived from neural crestMotor neuron
NOT a derivative of neural crestCauda equine
NOT a Neural Crest derivativeSpinal Cord



Question Answer
Aortic arch derivatives Pulmonary artery derived from 6th arch, Maxillary arterydevelops from 1st arch, All 6 arches are NOT present simultaneously
Aortic arch is developed FromLeft primitive arterial segment
3rd and 4th aortic arches are connected byDuctus caroticus
Branches of dorsal aortaVentral splanchnic, lateral splanchnic, somatic intersegmental
NOT true about aortic arch derivatives5th arch is absent in 5% of embryo
Maxillary artery is a derivative of First Aortic arch
Structure derived from right fourth aortic archRight subclavian artery
Double aortic arch is due toPersistent fourth arch
Most common vascular ring encircling trachea and esophagusDouble aortic arch
Most common incomplete vascular ringAberrant right subclavian artery
Axial artery of upper limb7th intersegmental artery
Axis artery of lower limb5th lumbar intersegmental artery
Congenital anomalies associated with defective aortic archesDouble aortic arch, aberrant right subclavian artery, coarctation of aorta
NOT an anomaly associated with defective aortic archesTransposition of great vessels



Question Answer
Derived from pharyngeal archesTensor tympani, Palatine tensor, Orbicularis oculi, Mylohyoid
Muscle NOT arising from Branchial archSuperior Oblique
NOT derived from pharyngeal archLevator palpebrae superioris, Palatine tonsils
Branchial arch in embryo begin to develop early in3rd week
Maxillary prominence develops inFirst pharyngeal arch
First pharyngeal archMaxillary and mandibular prominences are formed,Maxilla and zygoma bone are formed by intermembranous ossification, Tensor palati from first arch
Tensor tympani derived fromFirst arch
Derived from second archStylohyoid ligament, Stapes, Small cornu of hyoid
Second pharyngeal archStyloid
Nerve of second archFacial nerve
NOT derived from second archMalleus/incus
Nerve of III Pharyngeal archGlossopharyngeal nerve
Derived from <third pharyngeal> archStylopharyngeus
Derived from cartilage of third archGreater cornu of hyoid
Nerve supply of Sixth ArchVagus Nerve
Thymus develop from Ventral part of third pharyngeal pouch
Ectodermal cleft Cervical sinus is found between 2-6 arches, Ventral part of cleft is obliterated, Dorsal part of 1st cleft forms the lining of external ear
Primary and secondary plates are divided byIncisive foramen