Embryology Flashcards
What is the gene that is expressed at the base of limbs in a zone of polarizing activity?
SHH (sonic hedgehog gene)
MCH1 likes to bind to what type of T cell
CD8 Killer cells
What does the SHH gene do?
The sonic hedgehog gene regulates patterning along the anterior-posterior axis.
MCH 2 (II) binds to what kind of cells?
CD4 helper T cells
What two layers make up the bilaminar embryonic disc?
epiblast and hypoblast
What layer develops into ALLLL
Epiblast
Yolk sac will develop into what?
Allantois
The embryo exists as a bilaminar disk during the _______ week of development.
2nd
Describe the shunts of fetal circulation?
What structures are you bypassing in fetal circulation?
the liver once and the lungs twice….
(meaning you avoid using the liver in one of the shunts, and the lungs in two of the shunts)
the first pharyngeal cleft becomes what?
the external auditory meatus
The 2nd, 3rd, and 4th pharyngeal cleft becomes what?
temporary cervical sinuses
they are obliterated by proliferation of 2nd arch mesenchyme
During fetal development, _____ typically forms the CNS and brain, while _____ typically forms the PNS and non-neural structures nearby.
Neuroectoderm
neural crest cells
Pharyngeal arch 1; what cranial nerve might be affected?
CN 5
Trigeminal - mandibular branch, muscles of mastication
Pharyngeal arch 2; what cranial nerve might be affected?
CN 7
Facial
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Arch 3; what cranial nerve might be affected?
CN 9
Glossopharyngeal
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Arch 4; what cranial nerve might be affected?
CN 9 and 10
VAGUS
Superior laryngeal N
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Arch 4; what cranial nerve might be affected?
CN 10
VAGUS N; Superior laryngeal branch
Muscles: pahryngeal constrictors, cricothyroid, levator veli palatini
- posterior 1/3 tongue
Cartilage: thyroid
The fetal component of the placenta consists of which two cell types?
Cytotrophoblast; syncytiotrophoblast
Pharyngeal Arch 6; what cranial nerve might be affected?
SPEAK; Speech
VAGUS; recurrent and inferior laryngeal branch
MUscles: all intrinsic muscles of larynx except cricothyroid
Cartilage: sing and act, AND THYROID
1st pharyngeal pouch
EAR
Middle ear cavity, eustachain tube, mastoid aid cells
- contributes to endoderm-lined structures of the ear
2nd pharyngeal pouch
tonsils
- epithelial lining of palatine tonsils
3rd pharyngeal pouch
inferior parathroids, thymus
- dorsal wings - inferior parathyroids
- ventral wings - thymus
4th pharyngeal pouch
Superior Parathyroids
Dorsal wings - superior parathyroids
Ventral wings - parafollicular cells (C cells) of thyroid
The umbilical cord contains how many umbilical arteries and umbilical veins?
Two arteries and one vein
Do the umbilical arteries carry oxygenated or deoxygenated blood?
Deoxygenated blood
AFAB
default development (if no androgens present)
- mesonephric duct degenerates and the male remnantis appendix testes
- paramesonephric (mullerian) duct develops – develops into female internal structures
–> these are the fallopian tubes, uterus, proximal vagina
distal vagina is from what…
urogenital sinus
AMAB
needs androgens to develop
- paramesonephric duct DEgenerates (female remnant is gartner duct)
- mesonephric (Wolffian) duct develops – develops into male internal structures (except prostate)
SEED in AMAB stands for…
Seminal Vesicles
Epididymis
Ejaculatory duct
Ductus deferens
SRY gene of __ chromosome….
of the Y chromosome
produces testis determining factor
this leads ot testes development
Sertoli cells secrete
Mulerian inhibitor factor
this suppresses developmnet of paramesonephric duct
Leydig cells secrete _______
androgens
which stimulate development of mesonephric duct
Briefly describe the sexual differentiation flow chart
W hat is the order of branchial apparatus components, from outside to inside?
Clefts, Arches, Pouches (remember: CAP covers outside from inside)
Gubernaculum –
band of fibrous tissue
Male Remnant – anchors
testes within scrotum * Female Remnant – ovarian
ligament + round ligament of
uterus
Processus vaginalis – fibrous tissue evagination of peritoneum
Male Remnant – forms tunica vaginalis
- Pouch of serous membrane
that covers the testes
Female Remnant – obliterated
Describe the steps of chamber septation?
- septum primum grows
- ostium primum narroes
- ostium secundum forms in septum primum
- septum secundum deveops on R side of septum primum
- septum secundum expands and covers most of ostium secundum
- septum primum that remains forms a one-way valve of foramen ovale
- Septum primum closes against septum secundum – this seals foramen ovale
- septum secundum and primum fuse during infancy forming atrial septum
The VENTRICLE septation of chambers
- Muscular interventricular septum forms
Opening is interventricular foramen - Aorticopulmonary septum rotates and fuses with muscular ventricular septum to form membranous interventricular septum
(closing interventricular foramen) - Growth of endocardial cushions separates atria from ventricles and contributes to both atrial septation and membranous portion of interventricular septum
Ascending aorta / Pulmonary trunk… formation
Truncal and bulbar ridges spiral and fuse to form; arise from neural crest cell migrations
Aortic and pulmonary valve formation
Endocardial cushions of outflow tract
Mitral / Tricuspid valves formation
Fused endocardial cushions of AV canal
Truncus arteriosis gives rise to what adult structure
ascending aorta
pulmonary trunk
Name the three shunts
Ductus Venosus
Foramen ovale
Pulmonary trunk
INSTEAD OF THE LIVER and LUNG, LUNG
What does the FUNCTION of the lung come from?
ENDODERM
What 2 layers does the lung come from?
mesoderm
endoderm (most of the function of lung)
Gastrylation of Lungs
Budding of lungs @4th WEEK
Budding of lungs @5th WEEK
Pseudoglandular period
Canicular to Saccular
When is a fetus viable or able to live outside of the womb?
36 weeks
GI development Foregut
Esophagus to duodenum at the level of pancreatic duct and common bile duct insertion (ampulla of vater)
GI development Midgut
- Lower duodenum to proximal 2/3 of transverse colon
- Week 6: physiologic herniation of midgut through umbilical ring
- Week 10: returns to abdominal cavity and rotates 270 degrees counterclockwise around superior mesenteric
artery (SMA)
GI development Hindgut
Distal 1/3 of transverse colon to anal canal above pectinate line
Neural Development
Notochord induces ectoderm to differentiate into neuroectoderm and form neural plate
- notochord becomes nucleus pulposis of intervertebral discs
neural plate – neural tube and neural crest cells
lateral walls of neural tube are divied into plates
1. alar plate (dorsal)
Basal plate (ventral) – motor, induced by SHH sonic hedgehog
Nephrogenesis
- Ureteric bud (metanephric diverticulum)
- Derived from caudal end of mesonephric duct
- Ureter, pelvises, calyces, collecting ducts
- Finalized by week 10
Metanephric mesenchyme (metanephric blastema)
- Interacts with ureteric bud to induce
differentiation and formation of glomerulus through to DCT
Ureteropelvic junction
- Last to canalize
Urologic Development, Kidney
Pronephros – degenerates
Mesonephros – interim kidney during 1st trimester
1. Males / Wolffian duct / ductus deferens and epididymis
Metanephros
- Permanent Nephrogenesis complete by week 36
Fetal Erythropoiesis
Young liver synthessizes blood…
Y Yolk sac
L Liver
S Spleen
B Bone marrow
Fetal Hemoglobin Development
Alpha (always)
Gamma (goes)
Beta (becomes)
HbF fetal hemoglobin has a higher affinity for oxygen (than maternal hemoglobin across the placenta)
Blood Types are an example of ….
Co-dominance
Type O blood
antigens on surface of RBC – NONE
Anti-A, AND Anti-B ANTIBODIES in plasma
“universal donor”
O- can give to anyone, but only recieve from O-
Type AB blood
antigens on surface of RBC – A & B
NO antibodies in plasma
“universal receiver”
AB+ can receive from any; can only give to AB+
Rh + vs -
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Aortic Pulmonary AP Septum
Neural crest cells migrate from the hindbrain region through pharyngeal arches 3, 4 & 6 and invade both the truncal ridges and bulbar ridge
The truncal & bulbar ridges grow and twist around one another in a spiral fashion to eventually fuse into the AP septum
The AP septum divides the truncus arteriosus and bulbus cordis into the aorta and pulmonary trunk
Patient Truncus Arteriosus (PTA)
caused by abnormal neural crest cell migration so there is only partial development of the AP septum
One large vessel leaves the heart and receives
blood from both the R&L ventricles
It’s usually accompanied by a membranous ventricular septal defect (VSD) and cyanosis from a R à L shunting of blood
Pts would NEED surgical treatment
Clinical L-transposition of the great arteries
aorta and pulmonary trunk are transposed and the ventricels are inverted (the anatomical RV lies on the left side and the anatomical LV lies on the right side)
these major deviations offset one another so that blood flow pattern is normal
Teratalogy of Fallot (TF) ***
abnormal neural crest cell migration (skewed development of AP septum)
pulmonary trunk – small diameter
Aorta – large diameter
4 classic malformations:
1. Pulmonary stenosis
2. Right ventricular hypertrophy
3. Overriding aorta
4. Ventricular septal defect
(NEMONIC) = PROVE
infants ahve marked syanosis (or R–> L shunting of blood)
AV Atrioventricular septum
dorsal AV & ADD MORE
AVSD
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Interventricular IV septum
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IV Septal Defects (VSDs)
depends on the size and severity of hole
PDA ***
common in premature infacnts and maternal rubella infection
ductus arteriosus fails to close between the L pulmonary artery and aorta
normally closes within a few hours after birth through smooth muscle contraction to ultimately form the ligamentum arteriosum
can be treated with prostaglandin synthesis inhibitors
