Embryology Flashcards
Malformation
structure never formed properly and was abnormal to begin with due to underlying genetic, epigenetic, or environmental factor
Sequence
malformation triggers series of other defects; aka field defect
Potter Sequence
kidney agenesis -> absent urine production -> oligohydramnios -> constriction of fetal movement, clubfoot, pulmonary hypoplasia, Potter facies
Pierre-Robin Sequence
micrognathia (may be due to oligohydramnios) -> posteriorly displaced tongue -> u-shaped cleft palate and breathing obstruction
Deformation
genetic components and potential for normal development present but constrictions in space/external constraints lead to abnormalities
Disruption
potential for normalcy present but something interferes and destroys formation, usually abnormality in uterine environment
Dysplasia
intrinsic cellular architecture of tissue not normally maintained throughout growth and development
Syndrome
generally recognized and well-characterized constellation of major and minor anomalies that occur together in predictable fashion with known cause
Association
group of anomalies that occur more frequently together than would be predicted by chance alone but that lack a predictable pattern/unified underlying etiology
Major Anomalies
anomalies/malformations that create significant medical problems or require specific surgical/medical management
Minor Anomalies
features that vary from those most commonly seen in normal population that don’t cause increased morbidity
When do most internal organs form?
4-6w
When do digits and facial features form?
8-12w
When does neurological development occur?
throughout gestation
Gametogenesis
- process of forming haploid germ cells that will combine to make diploid zygotes
- oogenesis starts during embryonic development
- spermatogenesis starts during puberty
Fertilization
- 0w FA
- sperm drawn towards chemoattractant produced by ovum
- zona pellucidum becomes impermeable when a sperm penetrates
- sperm nucleus decondenses and forms pronucleus
- fertilization triggers ovum to complete meiosis II and form pronucleus
- pronuclei fuse
Cleavage
- 0.5w FA
- zygote rapidly divides and forms blastocyst with inner cell mass and trophoblast
Implantation
- 10d FA
- as soon as it occurs, trophoblast differentiates into cytotrophoblast and syncytiotrophoblast
Placenta and Amniotic Fluid
- 2w FA
- formal circulation system established and develops into placenta
- amnionic cavity forms in blastocyst and chorionic cavity encases developing cell mass
- as embryo grows, amnion rapidly expands and joins chorion (fully fused 14w) and contains amniotic fluid
Gastrulation
- 3w FA
- embryo transitions from bilaminar to trilaminar
- notochord forms and neural tube development starting
- somites develop
Folding
- 4w FA
- transverse: flat embryo rolls up and forms tubular structure
- longitudinal: head and tail curve inward
Heart Formation
- 3.5w - 9w FA
- first organ to fully develop
- critical period for major anomalies 3.5-6.5w
L-transposition of Great Arteries
- heart tube loops to left instead of right
- asymptomatic but may have conduction defects
Atrial Septal Defects
- LR shunt
- heart failure, FTT< pulmonary vasoconstriction, pulmonary vascular disease
Ventricular Septal Defects
- LR shunt
- pulmonary HTN, pulmonary vascular disease, CHF
Endocardial Cushion Defect/AV Canal
- LR shunt
- seen in DS
Double Outlet Right Ventricle
- right ventricle empties into pulmonary artery and aorta, LV empties into RV
- cyanotic
- increased pulmonary blood flow, PVD, CHF
Tetralogy of Fallot
- obstruction to pulmonary outflow, VSD, RVH, overriding aorta
- cyanotic
- seen in 22q11.2
Persistent Truncus Arteriosus Communus
- absence of truncal and part of conal septum leads to common trunk instead of aorta and VSD
- cyanotic
- CHF, PVD
Aorticopulmonary Septal Defect
- LR shunt
- defect in ascending aorta without VSD due to neural crest cell defect
- like PDA
Patent Ductus Arteriosus
- LR shunt
- cyanotic
- could lead to PVD
Pulmonary Stenosis/Atresia
- RL shunt across foramen ovale
- cyanotic
- pulmonary flow into pulmonary artery diminished, RVH
D-Transposition of Great Arteries
- cyanotic
- RV outputs into aorta and LV outputs into pulmonary arteries
- can be catastrophic at birth and requires surgical intervention
Tricuspid Atresia
- cyanotic
- no opening in tricuspid valve leads to blockage between RA and RV and no flow across pulmonary artery
- hypoplastic RV, atresia/stenosis of pulmonary valve
- surgery required
Total Anomalous Venous Connection
- cyanotic
- complete mixing of saturated and desaturated blood in left atrium due to anomalous attachment of pulmonary veins into something below diaphragm
Vascular Ring
- compression of esophagus and trachea leads to severe respiratory distress
Esophageal Constriction
- posterior identation of esophagus due to presence of artery
- difficulty swallowing food
Coarctation of Aorta
- narrowing of aorta near ductus that decreases flow in ascending aorta
- may be preductal, postductal, or juxtaductal
- high blood pressure in arms, low blood pressure in legs, rib notching
- seen in Turner syndrome
Hypoplastic Left Heart
- cyanotic
- no flow through left side of heart due to mitral atresia, no flow through ascending aorta
- baby goes into shock when ductus closes
- surgical repair or heart transplant needed
Respiratory System Formation
- development takes place between 4-28w FA and continues until 8y
- lungs derived from developing foregut and respiratory pathway separated from digestive pathway
Tracheoesophageal Fistula
- abnormal communication between respiratory and digestive pathways
- when infant eats, can aspirate food into lungs
- when regurgitate/reflux, stomach contents can go into lungs
- G-tube placement
- associated with chromosomal anomalies, CHD, imperforate anus (VACTERL)
Apnea of Prematurity
periodic breathing in premature infants that leads to pauses in oxygen flow
Meconium Aspiration
meconium excreted into amniotic fluid when fetus in distress and aspirated into lungs leading to irritation and pneumonia
Respiratory Distress Syndrome
- issue with prematurity
- surface of alveoli become proteinaceous, leading to difficulty breathing
- treatment with ECMO
- may be prevented by administering glucocorticoids to stimulate lung maturation
Bronchopulmonary Dysplasia
improper development of lungs leads to overexpansion and respiratory distress
Stuctural Lung Anomalies
- lung hypoplasia
- unilateral absence of lung
- bilateral absence of lungs (not viable)
- severe hypoplasia (not viable)
- sequestration of lung
Transient Tachypnea of Newborn
babies born via C-section have retained fluid in lungs and may breathe faster
Persistent Pulmonary Hypertension of Newborn
- pulmonary HTN perpetuated in utero and after birth
- high pulmonary vascular pressure causes RL shunt
- ECMO needed
GI System Formation
- development takes place between 3-32w FA
- involves development of foregut, midgut, and hindgut
Foregut
- esophagus, stomach, first part of duodenum
- celiac artery and branch aorta
Midgut
- small intestine, cecum, part of ascending colon
- superior mesenteric artery
Hindgut
- transverse colon, descending colon, sigmoid colon, rectum
- inferior mesenteric artery
Esophageal Atresia
unable to pass what is swallowed, leading to polyhydramnios and prematurity
Hiatal Hernia
- hole for esophagus in diaphragm larger than it should be, allowing stomach to enter chest cavity
- GER
- thickened feedings, prop baby up
Diaphragmatic Hernia
- variable amounts of intestine pass through holes in diaphragm and end up in chest cavity
- hypoplastic lungs, small volume in abdomen
- can be fix via intrauterine repair
Eventration of Diaphragm
- muscular aspects of diaphragm underdeveloped so diaphragm remains high in chest
- lung development affected, respiratory distress
Diaphragmatic Palsy
phrenic nerve injury causes paralysis of diaphragm causing similar features as eventration
Pyloric Stenosis
- pyloric sphincter hypertrophy leads to forceful vomiting
- failure to gain weight, dehydration, vigorous waves in stomach, big stomach bubble
- more common in males
Biliary Atresia
- intrahepatic (in liver): jaundice, dark urine, lack of color in stool, need liver transplant
- extrahepatic (outside liver): palliative surgery
Annular Pancreas
pancreatic tissue completely surrounds duodenum leading to stenosis/atresia
Duodenal Stenosis/Atresia
- bilious vomiting, polyhydramnios, prematurity, “double bubble”
- associated with DS
Omphalocele
- gut fails to come back into body cavity but intestines not exposed to amniotic fluid
- associated with BWS
Gastroschisis
- hole in abdominal wall lateral to umbilicus allows intestines to protrude directly into amniotic fluid
- associated with young maternal age
Malrotation
abnormal fixation of intestinal structures to abdominal wall leading to twisting of intestines (volvulus) or fibrous obstructions (Ladd’s bands)
Intestinal Stenosis/Atresia
- proximal: polyhydramnios, multiple bubbles
- ileum: microcolon
- jejunum: cut off where polyhydramnios occurs
Diverticulum
outpouching that is mostly asymptomatic unless becomes infected or telescopes inward (intussusception)
Duplication
parts of gut duplicated
Meconium Ileus
- viscous secretion from CF patients that is stuck because peristalsis cannot move it
- infection, paralysis of ileum, “soap bubbles”, abdominal distension, no bowel sounds
Hirschsprung Disease
- neural crest cell disorder that prevents innervation for peristalsis
- megacolon, chronic obstruction
Rectal Atresia
- rectum forms fistula with adjacent stucture (vagina, urethra)
- delayed vomiting, no stool
Imperforate Anus
- membrane did not undergo apoptosis
- associated with chromosomal anomalies, vertebral, and other GI anomalies (VACTERL)
GU System Formation
- development occurs between 4-32w FA
- involves differentiation of pronephros, mesonephros, and metanephros along urogenital ridge into different structures and further differentiation of genitalia
- nephrogenesis not complete until 32w
- critical period 7.5w-9w
Pronephros
kidney formation
Mesonephros
- paramesonephric ducts: Mullerian ducts
- mesonephric ducts: Wolffian ducts
Metanephros
definitive kidney
Agenesis of Kidney
- kidney does not form at all
- Potter sequence, lung hypoplasia, respiratory insufficiency
Renal Obstruction
can cause oligohydramnios and pulmonary hypoplasia
Posterior Urethral Valves
bladder unable to empty leading to dilatation of ureters and renal pelvis, compression of kidney parenchyma, kidney damage, oligohydramnios
Horseshoe Kidney
- kidney fuses in pelvis which prevents its normal ascent
- associated with Turner
Cystic Kidneys
genetic and non-genetic causes and linked to disease in other organs (liver)
Exstrophy of Bladder
- abdominal wall doesn’t close completely over bladder and is exposed to amniotic fluid
- associated with other urinary tract anomalies, kidney problems
Rectovesicular Fistula
division of hindgut goes awry and rectal contents empty into bladder
Failure of Paramesonephric Ducts to Fuse in Midline
- duplication of cervix, duplication of horns, unequal horns, septate uterus
- impacts fertility
Hypospadias
- often due to deficiency of androgens
- penoscrotal/perineal: opening between unfused scrotum, ambiguous genitalia
- penial: opening on underside of shaft
- glanular: opening on underside of glans
- associated with SLOS, infertility
Inguinal Hernia
inguinal canal fails to close after testicular descent and intestine enters canal causing pain and intestinal obstruction
Ambiguous Genitalia
- several different etiologies
- important to consider AIS, CAH
Formation of Head, Face, and Neck
- facial development including lips, eyes, ears starting during 4w FA with more recognizable features 8-12w FA
- pharyngeal apparatus begins to develop and contributes to development of ear, thymus, thyroid, and parathyroid structures
Pharyngeal Arches
- arch 1: maxilla, mandible, mastication muscles, trigeminal nerve
- arch 2: muscles of facial expression, facial nerve
- arch 3: swallowing muscles, glossopharyngeal nerve
- arch 4: neck, swallowing muscles, aorta, glossopharyngeal nerve
- arch 5: neck
- arch 6: neck, pulmonary artery, ductus arteriosus
Pharyngeal Clefts
external ear canal
Pharyngeal Pouches
- internal ear canal
- tonsils
- parathyroid gland
- thymus
- thyroid
First Arch Syndrome
- marcostomia, cleft in cheek tissue, low-set ears, micrognathia
- complete lack of first arch leads to agnathia
- common in T18
Cleft Lip/Palate
- syndromic or nonsyndromic
- associated with recurrent ear infections, difficulty feeding
Microstomia
small mouth
Microophthalmia
small eyes
Ankyloglossus
tongue not freely mobile
Formation of Nervous System
- CNS starts developing 3w FA and continues to develop throughout gestation with critical period continuing throughout gestation
Neural Tube Defects
- spina bifida occulta
- meningocele: CSF and meninges bulge out but spinal cord unaffected
- myelomeningocele: CSF and spinal cord bulge out leading to damage
- anencephaly: no brain
- encephalocele: fluid +/- brain
- rachischisis: neural tube does not close
Charcot-Marie-Tooth
- abnormal myelination affects Schwann cells in PNS
- distal muscle weakness, muscle atrophy
Krabbe Disease
- leukodystrophy affecting oligodendrocytes
- brain and spinal cord damage, blindness, seizures, childhood death
Lissencephaly
- brain remains smooth
- significant neurological impact but involuntary functioning remains intact
Miller-Dieker Syndrome
- sporadic chr 17 deletion
- lissencephaly, dysmorphic features, renal issues
Holoprosencephaly
- spectrum of disorder depending on how much of telencephalon divides
- midline defects
- T13, SHH
Microcephaly
- abnormal brain development not caused by premature closing of sutures
- viral infection, maternal disease, genetic conditions
- ID, DD, seizures
Hydrocephalus
- too much fluid in brain due to excess production, poor recycling/drainage, blockage
- due to aqueductal stenosis, Dandy-Walker, Arnold-Chiari, IVH, achondroplasia
Neural Crest Cell Defects
- 22q11.2
- Waardenburg
- Hirschsprung disease
- chromaffin cells contributing to pheochromocytoma tumors (VHL, MEN1)
Familial Dysautonomia
- all autonomic innervation not functioning properly
- hypotonia, feeding difficulties, reduced sensitivity to temperature and pain
Craniosynostosis
- one or more suture fuses before it should leading to differences in skull shape
- cognitive function can be normal
Formation of Musculoskeletal System and Skin
- during 3-5w FA, somites develop form mesoderm and constitute dermatome (skin), myotome (muscle), and sclerotome (bone)
- critical period for limb anomalies 4-6w FA
Pectus Excavatum
chest caves inward
Pectus Carinatum
chest projects outward
Absent Fontanelles
crankiness, vomiting, high blood pressure, brain compression
Prune Belly Syndrome
no abdominal muscles, so abdomen enlarged
Limb Defects
- amelia: no limb
- phocomelia: only distal element present
- rhizomelia: shortening of proximal bones
- mesomelia: shortening of distal bones
- acromelia: shortening of digits
- micromelia: shortening of limb
- sirenomelia: caudal dysgenesis
- hip dysplasia: hip socket not adequately development
Digit Defects
- extrodactyly: clefting and syndactyly
- syndactyly: fusion of digits
- polydactyly: extra digits
Apert Syndrome
craniosynostosis and mitten hand deformity
Achondroplasia
rhizomelia, lumbar lordosis
Marfan Syndrome
hyperextensibility, joint laxity, tall stature, arachnodactyly, ectopia lentis, aortic dissection, pectus deformities
OI
- defect in collagen
- tendency to fracture, chest deformities
- severe forms incompatible with life
Ehlers-Danlos Syndrome
elastic skin, scarring, vascular issues
Holt-Oram Syndrome
- “hand-heart” condition
- defects of radial ray (absent thumbs/radius), CHD
Amniotic Bands
- oligohydramnios or tear in amniotic membrane can develop fibrous bands that put pressure on developing structure
- if compressing blood supply, distal elements will no longer grow
Albinism
no pigment granules
Ectodermal Dysplasia
- certain receptors or aspects of skin development not present, resulting in individual with delicate skin and sparse hair
- hypohidrotic form includes absent/sparse sweat glands leading to trouble regulating temperature
- abnormal tooth development
Hemangioma
raised collection of tiny blood vessels that usually fade in infancy
Peutz-Jegher Syndrome
freckles on vermilon border and inside mouth
NF
neurofibromas on skin
Tuberous Sclerosis
shagreen patches, hypopigmentation (ash leaf spots)
Gynecomastia
further breast development in men with Klinefelter syndrome
Diastrophic Dwarfism
Hitchhiker’s thumb, club foot, proportionate short stature
