Embryo Flashcards
Lens, cornea
Inner ear sensory organs
Olfactory epithelium
all DERIVED FROM WHAT?
surface ectoderm
Neural ganglia, adrenal medulla
Schwann cells, pia + arachnoid mater
all derived from WHAT?
Neural crest cells (part of ectoderm)
Brain + SC
Posterior pituitary, pineal gland
Retina
all derived from WHAT?
Neural tube (part of ectoderm)
Muscles (all 3 types)
CT, bone + cartilage
Spleen + HSCs
all derived from WHAT?
mesoderm
GI tract, liver, pancreas
Lungs
Bladder and urethra
All derived from WHAT?
endoderm
Middle ear + auditory tube
Thymus, parathyroids, thyroid follicular cells
Parafollicular C cells
all derived from what?
endoderm
specifically endoderm of pharyngeal pouches
Serosal linings
CV and lymphatic system
Adrenal cortex
all derived from what?
mesoderm
Kidneys, ureters and internal genitalia
all derived from what?
mesoderm
Anterior pituitary
Nasal + oral epithelium, salivary glands
Epidermis, sweat + mammary glands
All derived from what?
surface ectoderm
Aorticopulmonary septum + endocardial cushions
derived from what?
Neural crest cells (part of ectoderm)
Branchial arches (their bones + cartilage)
Skull bones
derived from what?
Neural crest cells (part of ectoderm)
Melanocytes
derived from what?
Neural crest cells (part of ectoderm)
musculoskeletal + nerve derivatives of pharyngeal arch 1
Meckel’s cartilage - CN V3 (mandibular)
muscles of mastication maxilla + mandible malleus + incus sphenoMandibular ligament Mylohyoid
(ant. belly digastric, tensor tympani + veli palatini, ant 2/3 of tongue)
(related to Pierre-Robin sequence - micrognathia, glossoptosis, cleft palate + airway obstruction)
(remember incus and the Ms … Meckel’s, mastication muscles, maxilla, mandible + malleus … plus incus)
musculoskeletal + nerve derivatives of pharyngeal arch 2
Reichert’s cartilage - CN VII facial n.
Facial expression mm. (“Smile”)
Stapes + Stapedius m.
PlatySma
PoSt. belly digaStric
Styloid proc. > Stylohyoid lig. and muscle > leSSer horn hyoid
Remember R, S (Reicherts, stapes, styloid stylohyoid > hyoid) and RiSorius (facial expression)
(assoc. with Treacher Collins syndrome)
musculoskeletal + nerve derivatives of pharyngeal arch 3
- StyloPHARYNGEUS muscle + glossoPHARYNGEAL nerve (CN IX)
- Greater horn hyoid (greater number 3 = greater horn)
(“stylishly swallow”)
msk and nerve derivatives of pharyngeal arch 4 + 6
- thyroid cartilage (4)
- cricoid cartilage (6)
- arytenoids, corniculate + cuneiform cartilages
- muscles of pharynx and larynx
- post 1/3 tongue
4th - SUPERIOR LARYNGEAL BRANCH of Vagus (“simply swallow”)
5th - RECURRENT/INF. LARYNGEAL BRANCHES of Vagus
(remember that the ant 2/3 tongue is from the 1st arch and the post 1/3 is from the last arches)
Treacher Collins syndrome
dev. abnormality of what?
affecting what?
abnormal 1ST / 2ND PHARYNGEAL ARCH DEV. due to NEURAL CREST issue
craniofacial issues (maxilla, mandible, zygomatic hypoplasia) > AIRWAY + FEEDING ISSUES
ossicle issues > CONDUCTIVE HEARING LOSS
Germ layer embryonic kidney is from?
this germ layer forms what which then gives what?
Intermediated MESODERM forms the UROGENITAL RIDGE which then forms the NEPHROGENIC CORD
Primitive structure that arises from cephalic part of nephrogenic cord?
what does it become?
PRONEPHROS
completely regresses
after the pronephros, what forms from the midportion of the nephrogenic cord?
what persists from it?
MESONEPHROS
Wolffian ducts - gives vas deferens + epididymis
regresses in females (> vestigial Gartner’s ducts)
after the mesonephros, how does the actual kidney begin to form?
METANEPHROS formation starts with URETERIC BUD (aka metanephric diverticulum; sprouts off caudal mesonephric duct)
how does the ureteric bud induce continuation of renal development?
ureteric bud penetrates sacral intermediate mesoderm to induce formation of the METANEPHRIC MESODERM (aka metanephric blastema)
the metanephric mesoderm + ureteric bud then exchange inductive signals to promote each other’s growth
what structures come from the ureteric bud?
from the metanephric mesoderm?
bud - collecting tubules + ducts, calyces, pelvis + ureters
metanephric mesoderm - glomeruli, Bowman’s space, PCT, loop, DCT
gene that controls differentiation of the gonads into testes or ovaries
what does it code for?
SRY gene on Y chromosome
codes for “testes determining factor” which allows XY embryos to develop testes
(absence of SRY > ovaries develop)
What do the two special cell types within testes stimulate in male reproductive development?
Sertoli cells - suppress female internal organ development via ANTI-MULLERIAN HORMONE; (also make androgen-binding protein that concentrates testosterone in the seminiferous tubules)
Leydig cells - secrete testosterone which STIMULATES WOLFFIAN DUCT formation + its derivatives (epididymis, vas deferens, ejaculatory ducts, seminal vesicles)
Heart embryo: these give rise to what?
Truncus arteriosus…
Bulbus cordis…
Endocardial cushion…
TA - asc. aorta + pulmonary trunk
BC - smooth parts of ventricles (outflow tracts)
EC - atrial septum; membranous IV septum; valves (all 4) … from endothelial cells that undergo EMT
Heart embryo: these give rise to what?
Primitive atrium
Primitive ventricle
Primitive pulmonary vein
A - trabeculated part of both atria
V - trabeculated part of both ventricles
PV - SMOOTH part of left atrium
Heart embryo:
L and R horns of SINUS VENOSUS give what?
Left horn - coronary sinus
Right horn - “sinus venarum” smooth part of RA
Heart embryo:
what gives the SVC?
R common cardinal v.
R anterior cardinal v.
What forms the VALVE of FORAMEN OVALE?
inferior remnant of SEPTUM PRIMUM
after septum secundum forms to the right of the remnant; higher RA pressure in utero pushes blood through, higher LA pressure postpartum presses it shut > FO closes + fossa ovale remains
What cells give rise to the AORTICOPULMONARY SEPTUM?
ectodermal NEURAL CREST cells
failure > persistent truncus arteriosus + VSD
What is the most common external opening site for a BRANCHIAL CYST?
what causes it?
anterior to SCM
painless, slowly enlarging mass on side of neck; freely mobile and soft
incomplete fusion SECOND + THIRD BRANCHIAL ARCHES to obliterate the 2nd branchial cleft
Dandy-Walker malformation
2 main features (visible on CT)
- VERMIS ABSENCE - no cerebellar vermis
2. 4TH VENTRICLE DILATION - cystic dilation causes enlargement of posterior fossa
Dandy-Walker malformation
associated features (3)
- CORPUS CALLOSUM agenesis
- MALFORMATIONS - face, heart, limbs
- SPINA BIFIDA
Dandy-Walker malformation
presentation (3) + complications (1)
infant with a) dev delay and b) large skull
c) unsteadiness + malcoordination (cerebellar)
complication - high ICP w/ lethargy/vomit (atresia of 4th ventricle foramina with NON-COM HYDROCEPHALUS)
Arnold-Chiari malformation ( aka Chiari II )
structural abnormality + consequence
herniation of low lying VERMIS and TONSILS thru f. magnum (Chiari II = 2 structures)
aqueductal stenosis > HYDROCEPHALUS
Arnold-Chiari malformation ( aka Chiari II )
associated abnormality far from brain
LUMBOSACRAL myelomeningocele - presents as paralysis/sensory loss below lesion
Chiari I malformation
structural issue? when presents?
assoc?
ECTOPIA of the cerebellar TONSILS (Chiari I = 1 structure)
presents in ADULTHOOD (asymp. in kids) with HA and ATAXIA
assoc. with SYRINGOMYELIA
Urogenital folds
give what in females?
in males?
labia minora
ventral penis + penile raphe
Failure of fusion of urogenital folds
causes what?
HYPOSPADIAS in males
normal in females - forms labia minora
Genital tubercle
becomes what in males? females?
glans penis + clitoris
Malpositioning of the genital tubercle causes what?
epispadias
presents as a small bifid penis with urethra on top
Failure of fusion of labioscrotal folds causes what in males
bifid scrotum
don’t fuse in females > labia majora
What are the derivatives of the FIRST and SECOND aortic arches?
1st - part of maxillary artery
2nd - stapedial + hyoid arteries
(1st is “MAXimal” and Second is Stapedial)
What are the derivatives of the 3rd aortic arch?
CCA and proximal ICA
C is the 3rd letter of the alphabet
What are the derivatives of the 4th aortic arch?
on left - AORTIC ARCH
on right - proximal R SUBCLAVIAN
(4th arch supplies the 4 limbs)
What are the derivatives of the 6th aortic arch?
Proximal pulmonary arteries
Ductus arteriosus
What is the Pierre Robin Sequence?
4 issues, due to what
1st pharyngeal arch derivative issues
- Micrognathia
- Glossoptosis
- Airway obstruction
- Cleft palate
inheritance of cleft lip / palate issues?
multifactorial
When and where are the two “meiotic arrests” in oogenesis?
- All PRIMARY oocytes in the ovary are arrested in PROphase (“diplotene”) of Meiosis I by MONTH 5 of FETAL LIFE
(at puberty, a primary oocyte becomes unarrested and undergoes meiosis I to form a secondary oocyte + polar body)
- SECONDARY OOCYTE is arrested at METAphase of Meiosis II and then ovulated
(it only continues meiosis II to form mature oocyte + polar body if fertilized)
(remember PRIMARY = PROphase of meio I …. SECONDARY = METAphase of meio II)
Over the first ~6 days after fertilization, the zygote (46, 2N) undergoes MITOSIS within the Fallopian tube…
what are the names of the THREE STRUCTURES that form as mitosis continues before implantation?
- BLASTULA - about days 1-4
- MORULA - once blastula reaches 32-cell size (day 4)
- BLASTOCYST - formed of embryoblast + trophoblast with cavity
Implantation
what degenerates first to allow it?
where does it implant? (part of uterus and layer of wall)
what part implants first?
ZONA PELLUCIDA degenerates, then
EMBRYONIC POLE implants into the POSTERIOR UTERINE WALL in the FUNCTIONAL LAYER of the endometrium
What embryonic process is occuring in WEEK TWO after fertilization?
(2 cell types, 2 cavities, 1 important future structure)
formation of the BILAMINAR DISC
- Epiblast - just below amniotic cavity
- Hypoblast - just above yolk sac
- fusion of epi-/hypoblast cells at one end forms the PRECHORDAL PLATE (future mouth)
(all projecting out into chorionic cavity)
Hematopoiesis
Where does it FIRST occur in the embryo (during what time period)?
Then what 3 places does it occur next (during what time period)?
- YOLK SAC - in mesoderm around yolk sac up to 6 weeks
2. LIVER, SPLEEN + THYMUS of fetus from 6 weeks to 3rd trimester
low hCG vs. high hCG
low - can mean MISCARRIAGE or ECTOPIA
high - can mean TWINS, MOLE, or gestational trophoblastic disease
What is GASTRULATION?
the process that produces the 3 primary germ layers: endoderm, ectoderm and mesoderm
begins with formation of PRIMITIVE STREAK in
What occurs in the embryo during the THIRD WEEK?
1 fundamental embryonic dev. process
2 organ systems begin development
- GASTRULATION - formation of germ layers
- NERVOUS and CV systems begin development
a. ectoderm forms neuroectoderm + NC cells
b. mesoderm forms PARAXIAL somites (35 pair),
plus int./lat. mesoderm
What tumor arises from remnants of the primitive streak?
where is it and what’s its morpho like?
SACROCOCCYGEAL teratoma
various types of tissue: bone, nerve, hair etc.
What kind of tumor arises from the notochord remnants?
found in what 2 places?
CHORDOMA
either INTRACRANIAL or SACRAL
What is the state of the embryonic nervous system at the ABOUT 20 DAYS of development?
NEURAL PLATE is present, but the neural tube is not yet complete
What structure within the embryonic mesoderm induces formation of the neural plate?
And what does it later become?
NOTOCHORD induces neural plate formation (day 18) and later becomes NUCLEUS PULPOSUS of IV discs
When is NEURAL TUBE formation complete?
day 21
and NC cells have pinched off the neural folds as they close, coming to rest in mesoderm on either side of neural tube
What are the two “plates” of the neural tube and how do they correspond to later CNS structures?
ALAR plate - dorsal, corresponds to dorsal horns (sensory)
BASAL plate - ventral, corresponds to anterior/ventral horns (motor)
What is HOLOPROSENCEPHALY?
mutations involved, structurally what happens, moderate vs. severe forms
FAILED SEPARATION of L/R hemispheres of brain, usually during WEEK 5 or 6, prob due to SHH signaling issue
moderate = cleft lip/palate severe = cyclopia
Holoprosencephaly
assoc. with what? (2)
MRI shows what? (2)
assoc. with 1) PATAU, trisomy 13 and 2) fetal alcohol syndrome
MRI shows 1) “MONOVENTRICLE” and 2) basal ganglia fusion
1st pharyngeal pouch, membrane + groove derivatives
remember pouch = internal, groove = external
pouch = middle ear + auditory tube epithelium
membrane = tympanic membrane
groove = ext. auditory canal epithelium
2nd pharyngeal pouch derivative
palatine tonsil crypt epithelium
groove and membrane obliterate + contribute to cervical sinus
3rd pharyngeal pouch derivatives
INFERIOR parathyroid glands and THYMUS
groove and membrane obliterate + contribute to cervical sinus
4th pharyngeal pouch derivatives
SUPERIOR parathyroid glands and “ultimobranchial body” which gives the PARAFOLLICULAR C CELLS of thyroid medulla
(groove and membrane obliterate + contribute to cervical sinus)
