Step 1 High Yield Embryology

Front 1

sonic hedgehog gene

Back 1

produced at base of limbs in zone of polarizing activity

involved in patterning along anterior-posterior axis

Front 2

Wnt-7 gene

Back 2

produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)

necessary for proper organization along dorsal-ventral axis

Front 3

FGF gene

Back 3

produced at apical ectodermal ridge

stimulates mitosis of underlying mesoderm, providing for lengthening of limbs

Front 4

homeobox (Hox) genes

Back 4

involved in segmental organization of embryo in a craniocaudal direction

Hox mutations lead to appendages in wrong locations

Front 5

fetal landmarks at day 0

Back 5

fertilization by sperm forming a zygote, initiating embryogenesis

Front 6

fetal landmarks within week 1

Back 6

hCG secretion begins after implantation of blastocyst

Front 7

fetal landmarks within week 2

Back 7

bilaminar disk (epiblast, hypoblast)

Front 8

fetal landmarks within week 3

Back 8

trilaminar dic

gastrulation

primitive streak, notochord, mesoderm, and its organization

neural plate begins to form

Front 9

fetal landmarks between weeks 3 and 8 (embryonic period)

Back 9

neural tube formed by neuroectoderm and closes by week 4

organogenesis

fetus is extremely susceptible to teratogens

Front 10

fetal landmarks during week 4

Back 10

heart begins to beat

upper and lower limb buds begin to form

Front 11

fetal landmarks during week 8 (fetal period)

Back 11

fetal movement

fetus looks like a baby

Front 12

fetal landmarks during week 10

Back 12

genitalia have male/female characteristics

Front 13

alar plate

Back 13

dorsal

sensory

same orientation as spinal cord

Front 14

basal plate

Back 14

ventral

motor

same orientation as spinal cord

Front 15

when does a fertilized egg become a zygote?

Back 15

day 2

Front 16

when does a fertilized egg become a morula?

Back 16

day 3

Front 17

when does a fertilized egg become a blastocyst?

Back 17

day 5

Front 18

when does a fertilized egg become implanted?

Back 18

day 6

Front 19

what induces ectoderm to differentiate into neuroectoderm and form the neural plate?

Back 19

the notochord induces overlying ectoderm to differentiate into neuroectoderm to form the neural plate

Front 20

what does the neural plate give rise to?

Back 20

neural tube
neural crest cells

Front 21

what does the notochord become in adults?

Back 21

it becomes the nucleus pulposus of the intervertebral disk in adults

Front 22

what is the rule of 2's for the second week of early development?

Back 22

2 germ layers (bilaminar disk):
- epiblast
- hypoblast

2 cavities:
- amniotic cavity
- yolk sac

2 components to placenta:
- cytotrophoblast
- syncytiotrophoblast

Front 23

what happens to the epiblast?

Back 23

the epiblast is the precursor to ectoderm

it invaginates to form the primitive streak, which gives rise to both intraembryonic mesoderm and part of the endoderm

Front 24

what is the rule of 3's for the third week of early development?

Back 24

3 germ layers (gastrula):
- ectoderm
- mesoderm
- endoderm

Front 25

what is the rule of 4's for the fourth week of early development?

Back 25

4 heart chambers
4 limb buds grow

Front 26

what are the embryologic derivatives of the surface ectoderm?

Back 26

1. adenohypophysis (from Rathke's pouch)
2. ocular lens
3. epithelial linings of oral cavity, sensory organs of ear, and olfactory epithelium
4. epidermis
5. anal canal below pectinate line
6. salivary, sweat, mammary glands

Front 27

what is a craniopharyngioma?

Back 27

benign Rathke's pouch tumor with cholesterol crystals and/or calcifications

Front 28

from what embryologic germ layer is the adenohypophysis derived?

Back 28

surface ectoderm

(derived from Rathke's pouch)

Front 29

from what embryologic germ layer is the lens of the eye derived?

Back 29

surface ectoderm

Front 30

from what embryologic germ layer is the epithelial lining of the oral cavity derived?

Back 30

surface ectoderm

Front 31

from what embryologic germ layer is the epithelial lining of the sensory organs of the ear derived?

Back 31

surface ectoderm

Front 32

from what embryologic germ layer is the olfactory epithelium derived?

Back 32

surface ectoderm

Front 33

from what embryologic germ layer is the epidermis derived?

Back 33

surface ectoderm

Front 34

from what embryologic germ layer is the anal canal derived (below the pectinate line)?

Back 34

surface ectoderm

Front 35

from what embryologic germ layer are the salivary glands derived?

Back 35

surface ectoderm

Front 36

from what embryologic germ layer are the sweat glands derived?

Back 36

surface ectoderm

Front 37

from what embryologic germ layer are the mammary glands derived?

Back 37

surface ectoderm

Front 38

what are the embryologic derivatives of neuroectoderm?

Back 38

brain
- neurohypophysis
- CNS neurons
- oligodendrocytes
- astrocytes
- ependymal cells
- pineal gland
retina
spinal cord

neuroectoderm - think CNS and brain

Front 39

what are the embryologic derivatives of neural crest?

Back 39

autonomic nervous system
dorsal root ganglia
cranial nerves
celiac ganglion
melanocytes
chromaffin
cells of adrenal medulla
parafollicular (C) cells of thyroid
Schwann cells
pia mater and arachnoid
bones of the skull
odontoblasts
aorticopulmonary septum

neural crest - think PNS and non-neural structures nearby

Front 40

from what embryologic germ layer is the autonomic nervous system derived?

Back 40

neural crest

Front 41

from what embryologic germ layer are the dorsal root ganglia derived?

Back 41

neural crest

Front 42

from what embryologic germ layer are the cranial nerves derived?

Back 42

neural crest

Front 43

from what embryologic germ layer is the celiac ganglion derived?

Back 43

neural crest

Front 44

from what embryologic germ layer are melanocytes derived?

Back 44

neural crest

Front 45

from what embryologic germ layer are chromaffin cells of the adrenal medulla derived?

Back 45

neural crest

Front 46

from what embryologic germ layer are parafollicular (C) cells of the thyroid derived?

Back 46

neural crest

Front 47

from what embryologic germ layer are Schwann cells derived?

Back 47

neural crest

Front 48

from what embryologic germ layer are the pia mater and arachnoid mater derived?

Back 48

neural crest

Front 49

from what embryologic germ layer are the bones of the skull derived?

Back 49

neural crest

Front 50

from what embryologic germ layer are odontoblasts derived?

Back 50

neural crest

remember: odonto = teeth
- think CREST toothpaste

Front 51

from what embryologic germ layer is the aorticopulmonary septum derived?

Back 51

neural crest

Front 52

what are the embryologic derivatives of endoderm?

Back 52

gut tube epithelium:
- anal canal above the pectinate line

derivatives:
- lungs
- liver
- pancreas
- thymus
- parathyroid
- thyroid follicular cells

Front 53

what is the acronym for mesodermal defects?

Back 53

VACTERL
V-ertebral defects
A-nal atresia
C-ardiac defects
T-racheoEsophageal fistula
R-enal defects
L-imb defects (bone and muscle)

Front 54

what are the embryologic derivatives of mesoderm?

Back 54

muscle
bone
connective tissue
serous linings of body cavities
spleen (derived from foregut mesentery)
cardiovascular structures
lymphatics
blood
bladder
urethra
vagina
eustachian tube
kidneys
adrenal cortex
skin dermis
testes
ovaries

Front 55

from what embryologic germ layer is the gut tube epithelium derived?

Back 55

endoderm

**includes anal canal above the pectinate line**

Front 56

from what embryologic germ layer are the lungs derived?

Back 56

endoderm

Front 57

from what embryologic germ layer is the liver derived?

Back 57

endoderm

Front 58

from what embryologic germ layer is the pancreas derived?

Back 58

endoderm

Front 59

from what embryologic germ layer is the thymus derived?

Back 59

endoderm

Front 60

from what embryologic germ layer are the parathyroid glands derived?

Back 60

endoderm

Front 61

from what embryologic germ layer are the thyroid follicular cells derived?

Back 61

endoderm

Front 62

from what embryologic germ layer is muscle derived?

Back 62

mesoderm

Front 63

from what embryologic germ layer is bone derived?

Back 63

mesoderm

Front 64

from what embryologic germ layer is connective tissue derived?

Back 64

mesoderm

Front 65

from what embryologic germ layer is the serous lining of body cavities (e.g. peritoneum) derived?

Back 65

mesoderm

Front 66

from what embryologic germ layer is the spleen derived?

Back 66

mesoderm

**derived from foregut mesentery**

Front 67

from what embryologic germ layer are the cardiovascular structures derived?

Back 67

mesoderm

Front 68

from what embryologic germ layer are the lymphatics derived?

Back 68

mesoderm

Front 69

from what embryologic germ layer is blood derived?

Back 69

mesoderm

Front 70

from what embryologic germ layer is the urethra derived?

Back 70

mesoderm

Front 71

from what embryologic germ layer is the vagina derived?

Back 71

mesoderm

Front 72

from what embryologic germ layer are the eustachian tubes derived?

Back 72

mesoderm

Front 73

from what embryologic germ layer are the kidneys derived?

Back 73

mesoderm

Front 74

from what embryologic germ layer are the adrenal cortices derived?

Back 74

mesoderm

Front 75

from what embryologic germ layer is the skin dermis derived?

Back 75

mesoderm

Front 76

from what embryologic germ layer are the testes derived?

Back 76

mesoderm

Front 77

from what embryologic germ layer are the ovaries derived?

Back 77

mesoderm

Front 78

what is the postnatal derivative of the notochord?

Back 78

nucleus pulposus of the intervertebral disk

Front 79

malformation

Back 79

intrinsic disruption in organ morphogenesis

occurs during the embryonic period (weeks 3-8)

Front 80

deformation

Back 80

extrinsic disruption in organ morphogenesis

occurs after the embryonic period

Front 81

agenesis

Back 81

absent organ due to absent primordial tissue

Front 82

hypoplasia

Back 82

incomplete organ development

primordial tissue is present

Front 83

aplasia

Back 83

absent organ despite presence of primordial tissue

Front 84

teratogens

Back 84

fetus is most susceptible in the 3rd to 8th weeks of pregnancy (embryonic period, during organogenesis)

before week 3 there is an all-or-none effect

after week 8 only growth and function are affected

Front 85

teratogenic effects of ACE inhibitors

Back 85

renal damage

Front 86

teratogenic effects of alkylating agents

Back 86

absence of digits

multiple anomalies

Front 87

teratogenic effects of aminoglycosides

Back 87

CN VIII toxicity

remember: A MEAN GUY hit the baby in the ear

Front 88

teratogenic effects of carbamazepine

Back 88

neural tube defects
craniofacial defects
fingernail hypoplasia
developmental delay
IUGR

Front 89

teratogenic effects of diethylstilbestrol (DES)

Back 89

vaginal clear cell adenocarcinoma in the fetus

Front 90

teratogenic effects of folate antagonists

Back 90

neural tube defects

Front 91

teratogenic effects of lithium

Back 91

Ebstein's anomaly (atrialized right ventricle)

Front 92

teratogenic effects of phenytoin

Back 92

fetal hydantoin syndrome
microcephaly
dysmorphic craniofacial features
hypoplastic nails
hypoplastic distal phalanges
cardiac defects
IUGR
mental retardation

Front 93

teratogenic effects of tetracyclines

Back 93

discolored teeth

Front 94

teratogenic effects of thalidomide

Back 94

limb defects ("flipper" limbs)

LIMB defects with tha-LIMB-domide

Front 95

teratogenic effects of valproic acid

Back 95

inhibition of maternal folate absorption leading to neural tube defects

Front 96

teratogenic effects of warfarin

Back 96

bone deformities
fetal hemorrhage
abortion
ophthalmologic abnormalities

do not wage WARFARE on the baby; keep it HEPPY with HEParin (does not cross the placenta)

Front 97

teratogenic effects of alcohol abuse

Back 97

leading cause of birth defects and mental retardation

fetal alcohol syndrome

Front 98

teratogenic effects of cocaine

Back 98

abnormal fetal development and fetal addiction

placental abruption

Front 99

teratogenic effects of smoking (nicotine, CO)

Back 99

preterm labor
placental problems
IUGR
ADHD

Front 100

teratogenic effects of iodide (lack or excess)

Back 100

congenital goiter or hypothyroidism

Front 101

teratogenic effects of maternal diabetes

Back 101

caudal regression syndrome (anal atresia to sirenomelia)

congenital heart defects

neural tube defects

Front 102

teratogenic effects of excess vitamin A

Back 102

extremely high risk for spontaneous abortions and birth defects
- cleft palate
- cardiac abnormalities

Front 103

teratogenic effects of X-rays

Back 103

microcephaly
mental retardation

Front 104

fetal alcohol syndrome

Back 104

leadicng cause of congenital malformations in US

newborns of mothers who consumed significant amounts of alcohol during pregnancy have an inc. incidence of congenital abnormalities (pre- and postnatal developmental retardation, microcephaly, holoprosencephaly, facial abnormalities, limb dislocation, heart/lung fistulas)

mechanism may include inhibition of cell migration

Front 105

what is the leading cause of congenital malformations in the United States?

Back 105

fetal alcohol syndrome

Front 106

dizygotic twins

Back 106

arise from 2 separate eggs that are separately fertilized by two different sperm

**ALWAYS two zygotes**

twins are dichorionic and diamniotic

Front 107

monozygotic twins

Back 107

arise from 1 fertilized egg (1 egg + 1 sperm) that splits into two zygotes in early pregnancy

degree of separation depends on when the fertilized egg splits into two zygotes

timing of this separation determines the number of chorions and number of amnions

Front 108

what is the result of eggs splitting between 0 and 4 days after fertilization?

Back 108

cleavage between the two cell stage and the morula

occurs in 25% of twins

placenta can be fused or can be separate; twins are dichorionic and diamniotic

Front 109

what is the result of eggs splitting between 4 and 8 days after fertilization?

Back 109

cleavage between the morula stage and blastocyst stage

occurs in 75% of twins

twins are monochorionic and diamniotic

Front 110

what is the result of eggs splitting between 8 and 12 days after fertilization?

Back 110

cleavage between the blastocyst stage and the stage with a formed embryonic disc

occurs in <1% of twins

twins are monochorionic and monoamniotic

Front 111

what happens if a fetus is cleaved more than 13 days after fertilization?

Back 111

twins are monochorionic, monoamniotic, and conjoined

Front 112

what is the primary site of nutrient and gas exchange between a mother and fetus?

Back 112

placental development

Front 113

fetal component of the placenta

Back 113

cytotrophoblast - inner layer of chorionic villi (Cyto makes Cells)

syncytiotrophoblast - outer layer of chorionic villi
- secretes hCG

Front 114

what is hCG?

Back 114

human chorionic gonadotropin

hormone that is structurally similar to LH

stimulates corpus luteum to secrete progesterone during the first trimester

Front 115

maternal component of the placenta

Back 115

decidua basalis - derived from the endometrium

maternal blood is in lacunae

Front 116

what vascular structures are found in the umbilical cord?

Back 116

2x umbilical arteries
- return deoxygenated blood from fetal internal iliac arteries to placenta

1x umbilical vein
- supplies oxygenated blood from placenta to fetus
- drains into IVC

Front 117

where does the umbilical vein drain?

Back 117

inferior vena cava (IVC)

Front 118

with what is a single umbilical artery associated?

Back 118

congenital and chromosomal anomalies

Front 119

from where are the umbilical arteries and veins derived?

Back 119

allantois

Front 120

urachal duct development

Back 120

3rd week - yolk sac forms allantois, which extends into urogenital sinus

allantois becomes urachus, a duct between the bladder and the yolk sac

Front 121

urachal duct abnormalities

Back 121

failure of urachus to obliterate:
1. patent urachus - urine discharge from umbilicus
2. vesicourachal diverticulum - outpouching of bladder

Front 122

vitelline duct development

Back 122

the vitelline duct connects the yolk sac to the midgut lumen

in the 7th week, the vitelline (omphalomesenteric) duct is obliterated

Front 123

vitelline duct abnormalities

Back 123

1. vitelline fistula - failure of duct to close, leading to meconium discharge from umbilicus

2. meckel's diverticulum - partial closure, with patent portion attached to ileum; pt may have ectopic gastric mucosa leading to melena and periumbilical pain

Front 124

meckel's diverticulum

Back 124

partial closure of the vitelline duct, with the patent portion attached to the ileum

pt may have ectopic gastric mucosa leading to melena and periumbilical pain

Front 125

to what structures does the truncus arteriosus (TA) give rise?

Back 125

ascending aorta
pulmonary trunk

Front 126

to what structures does the bulbus cordis give rise?

Back 126

right ventricle

smooth parts (outflow tracts) of left and right ventricles

Front 127

to what structures does the primitive ventricle give rise?

Back 127

trabeculated left and right ventricles

Front 128

to what structures does the primitive ventricle give rise?

Back 128

trabeculated left and right atria

Front 129

to what structures does the left horn of the sinus venosus (SV) give rise?

Back 129

coronary sinus

Front 130

to what structures does the right horn of the sinus venosus (SV) give rise?

Back 130

smooth part of right atrium

Front 131

to what structures do the right common cardinal vein and right anterior cardinal vein give rise?

Back 131

superior vena cava (SVC)

Front 132

formation of truncus arteriosus

Back 132

neural crest migration leads to truncal and bulbar ridges that spiral and fuse to form the aorticopulmonary septum

this then develops into the ascending aorta and pulmonary trunk

Front 133

pathology of truncus arteriosus

Back 133

1. transposition of great vessels (failure to spiral)
2. tetralogy of Fallot (skewed aorticopulmonary septum development)
3. persistent truncus arteriosus (partial aorticopulmonary septum development)

Front 134

steps of interventricular septum development

Back 134

1. muscular septum forms (opening is called interventricular foramen)
2. aorticopulmonary septum meets and fuses with muscular ventricular septum to form membranous IV septum, closing the IV foramen
3. growth of endocardial cushions separates atria from ventricles and contributes to both atrial separation and membranous portion of the IV septum

Front 135

pathology of interventricular septum development

Back 135

improper neural crest migration into the truncus arteriosus can result in transposition of the great arteries or a persistent truncus arteriosus

membranous septal defect causes initial left-to-right shunting, which then becomes right-to-left shunting (Eisenmenger's syndrome)

Front 136

Eisenmenger's syndrome

Back 136

membranous septal defect in the IV septum causes initial left-to-right shunting, which then becomes right-to-left shunting

Front 137

stages in the development of the interatrial septum

Back 137

1. foramen primum narrows as septum primum grows toward endocardial cushions
2. perforations in septum primum form foramen secundum (foramen primum disappears)
3. foramen secundum maintains right-to-left shunt as septum secundum begins to grow
4. septum secundum contains a permanent opening (foramen ovale)
5. foramen secundum enlarges and upper part of septum primum degenerates
6. remaining portion of septum primum forms valve of foramen ovale
7. septum secundum and septum primum fuse to form the atrial septum
8. foramen ovale usually closes soon after birth because of inc. left atrial pressure

Front 138

pathology of interatrial septum

Back 138

patent foramen ovale, which is caused by excessive resorption of septum primum and/or secundum

Front 139

where does fetal erythropoiesis occur?

Back 139

Yolk sac (3-8 wks)
Liver (6-30 wks)
Spleen (9-28 wks)
Bone marrow (>28 wks)

remember: Young Liver Synthesizes Blood

Front 140

what are the globin groups in fetal hemoglobin?

Back 140

2 alpha subunits
2 gamma subunits

Front 141

what are the globin groups in adult hemoglobin?

Back 141

2 alpha subunits
2 beta subunits

Front 142

what is the O2 saturation of blood in the umbilical vein?

Back 142

about 80%

Front 143

what is the O2 saturation of blood in the umbilical artery?

Back 143

very, very low

Front 144

what are the three important shunts in fetal circulation?

Back 144

1. ductus venosus (umbilical vein to IVC; bypass hepatic circulation)

2. foramen ovale (right atrium to left atrium; bypass pulmonary circulation)

3. ductus arteriosus (pulmonary artery to aorta; bypass pulmonary circulation)

Front 145

ductus venosus

Back 145

blood entering the fetus through the umbilical vein is conducted via the ductus venosus into the IVC to bypass the hepatic circulation

Front 146

foramen ovale

Back 146

most oxygenated blood reaching the heart via the IVC is diverted through the foramen ovale and pumped out the aorta to the head and body

Front 147

ductus arteriosus

Back 147

deoxygenated blood from the SVC is expelled into the pulmonary artery and ductus arteriosus to the lower body of the fetus

Front 148

what happens to the three fetal shunts at birth?

Back 148

infant takes a breath leading to dec. resistance in pulmonary vasculature

decreased resistance in the pulmonary vasculature then leads to increased left atrial pressure vs. right atrial pressure

foramen ovale closes (now called fossa ovalis)

inc. O2 leads to dec. prostaglandins, causing closure of ductus arteriosus

Front 149

what drug can be used to force closure of a patent ductus arteriosus?

Back 149

indomethacin

Front 150

what drug can be used to maintain a patent ductus arteriosus?

Back 150

prostaglandins (PGE2 specifically)

Front 151

what is the postnatal derivative of the umbilical vein?

Back 151

ligamentum teres hepatis

(it is contained in the falciform ligament)

Front 152

what is the postnatal derivative of the umbiLical arteries?

Back 152

mediaL umbilical ligaments

Front 153

what is the postnatal derivative of the ductus arteriosus?

Back 153

ligamentum arteriosum

Front 154

what is the postnatal derivative of the ductus venosus?

Back 154

ligamentum venosum

Front 155

what is the urachus?

Back 155

the part of the allantoic duct between the bladder and the umbilicus

Front 156

what is the postnatal derivative of the foramen ovale?

Back 156

fossa ovalis

Front 157

what is the postnatal derivative of the allantois?

Back 157

allaNtois is the urachus-mediaN umbilical ligament

Front 158

what is a remnant of the allantois?

Back 158

urachal cyst or sinus

Front 159

what is the postnatal derivative of the notochord?

Back 159

nucleus pulposus of the intervertebral disc

Front 160

what are the three primary vesicles of the developing brain?

Back 160

1. forebrain (prosencephalon)
2. midbrain (mesencephalon)
3. hindbrain (rhombencephalon)

Front 161

what are the five secondary vesicles of the developing brain (from what primary vesicle do they each derive)?

Back 161

1. telencephalon (prosencephalon/forebrain)
2. diencephalon (prosencephalon/forebrain)
3. mesencephalon (mesencephalon)
4. metencephalon (rhombencephalon/hindbrain)
5. myelencephalon (rhombencephalon/hindbrain)

Front 162

what are the adult derivatives of the telencephalon?

Back 162

walls develop into the cerebral hemispheres

cavity develops into the lateral ventricles

Front 163

what are the adult derivatives of the diencephalon?

Back 163

walls develop into the thalamus

cavity develops into the third ventricle

Front 164

what are the adult derivatives of the mesencephalon?

Back 164

walls develop into the midbrain

cavity develops into the aqueduct of silvius

Front 165

what are the adult derivatives of the metencephalon?

Back 165

walls develop into the pons and the cerebellum

cavity develops into the upper part of the fourth ventricle

Front 166

what are the adult derivatives of myelencephalon?

Back 166

walls develop into the medulla

cavity develops into the lower part of the fourth ventricle

Front 167

from what vesicles do the cerebral hemispheres derive?

Back 167

primary vesicle: forebrain/prosencephalon

secondary vesicle: telencephalon (walls)

Front 168

from what vesicles do the lateral ventricles derive?

Back 168

primary vesicle: forebrain/prosencephalon

secondary vesicle: telencephalon (cavity)

Front 169

from what vesicles does the thalamus derive?

Back 169

primary vesicle: forebrain/prosencephalon

secondary vesicle: diencephalon (walls)

Front 170

from what vesicles does the third ventricle derive?

Back 170

primary vesicle: forebrain/prosencephalon

secondary vesicle: diencephalon (cavity)

Front 171

from what vesicles is the midbrain derived?

Back 171

primary: midbrain/mesencephalon

secondary: mesencephalon (walls)

Front 172

from what vesicles is the aqueduct of silvius derived?

Back 172

primary: midbrain/mesencephalon

secondary: mesencephalon (cavity)

Front 173

from what vesicles is the pons derived?

Back 173

primary: hindbrain/rhombencephalon

secondary: metencephalon (walls)

Front 174

from what vesicles is the cerebellum derived?

Back 174

primary: hindbrain/rhombencephalon

secondary: metencephalon (walls)

Front 175

from what vesicles is the upper part of the fourth ventricle derived?

Back 175

primary: hindbrain/rhombencephalon

secondary: metencephalon (cavity)

Front 176

from what vesicles is the medulla derived?

Back 176

primary: hindbrain/rhombencephalon

secondary: myelencephalon (walls)

Front 177

from what vesicles is the lower part of the fourth ventricle derived?

Back 177

primary: hindbrain/rhombencephalon

secondary: myelencephalon (cavity)

Front 178

neural tube defects

Back 178

neuropores fail to fuse in the fourth week causing persistent connection between the amniotic cavity and the spinal canal

associated with low folic acid intake during pregnancy

elevated alpha-fetoprotein (AFP) in amniotic fluid as well as in maternal serum

elevated AFP and acetylcholinesterase in the amniotic fluid b/c it leaks out of the CSF

Front 179

spina bifida occulta

Back 179

failure of bony spinal canal to close, though there is no structural herniation

usually seen at lower vertebral levels; usually a tuft of hair sits over the defect

dura is intact

Front 180

meningocele

Back 180

meninges herniate through spinal canal defect

Front 181

meningomyelocele

Back 181

meninges and spinal cord herniate through a spinal cord defect

Front 182

anencephaly

Back 182

malformation of the anterior end of the neural tube

pt has no brain/calvarium, has elevated alpha-fetoprotein, and polyhydramnios

no swallowing center in the brain

Front 183

holoprosencephaly

Back 183

decreased separation of hemispheres across the midline

results in cyclopia

associated with Patau's syndrome (trisomy 13), severe fetal alcohol syndrome, and cleft lip/palate

Front 184

what are the forebrain anomalies?

Back 184

anencephaly
holoprosencephaly

Front 185

what are the posterior fossa malformations?

Back 185

Chiari II
Dandy-Walker

Front 186

Chiari II

Back 186

cerebellar tonsillar herniation through the foramen magnum with aqueductal stenosis and hydrocephaly

often presents with syringomyelia and thoraco-lumbar myelomeningocele

Front 187

what is syringomyelia?

Back 187

disorder in which a cyst or cavity, called a syrinx, forms within the spinal cord

it can expand and elongate over time, destroying the spinal cord, possibly resulting in pain, paralysis, weakness, and stiffness in the back, shoulders, and extremities

may also cause a loss of the ability to feel extremes of hot or cold, especially in the hands.

generally leads to a cape-like loss of pain and temperature sensation along the back and arms

Front 188

Dandy-Walker syndrome

Back 188

large posterior fossa

absent cerebellar vermis with cystic enlargement of the fourth ventricle

can lead to hydrocephalus and spina bifida

Front 189

syringomyelia

Back 189

enlargement of the central canal of the spinal cord

crossing fibers of the spinothalamic tract are typically damaged first

presents as a "cape-like" bilateral loss of pain and temp sensation in upper extremities with preservation of touch sensation

syrinx = tube, as in syringe

associated with Chiari II malformation

most common at C8-T1

Front 190

what is derived from the first aortic arch?

Back 190

part of the MAXillary artery (branch of the external carotid artery)

1st arch is MAXimal

Front 191

what is derived from the second aortic arch?

Back 191

Stapedial artery and hyoid artery

Second = Stapedial

Front 192

what is derived from the third aortic arch?

Back 192

common Carotid artery
proximal part of internal carotid artery

remember: C is the third letter of the alphabet

Front 193

what is derived from the fourth aortic arch?

Back 193

- on left, the aortic arch
- on right, the proximal part of the right subclavian artery

4th arch (4 limbs) = systemic

Front 194

what is derived from the sixth aortic arch?

Back 194

proximal part of the pulmonary arteries and (on left only) ductus arteriosus

6th arch = pulmonary and pulmonary-to-systemic shunt (ductus arteriosus)

Front 195

where does the right recurrent laryngeal nerve loop around?

Back 195

4th aortic arch

proximal part of right subclavian artery

Front 196

where does the left recurrent laryngeal nerve loop around?

Back 196

6th aortic arch

ductus arteriosus and subsequently the aorta

Front 197

what are the components of the branchial apparatus?

Back 197

branchial clefts
branchial arches
branchial pouches

CAP covers outside from inside
Clefts = ectoderm
Arches = mesoderm
Pouches = endoderm

Front 198

branchial clefts

Back 198

part of the branchial apparatus

derived from ectoderm

also called branchial grooves

Front 199

branchial arches

Back 199

part of the branchial apparatus

derived from mesoderm (muscle, arteries) and neural crests (bones, cartilage)

Front 200

branchial pouches

Back 200

part of the branchial apparatus

derived from endoderm

Front 201

branchial cleft derivatives

Back 201

1st cleft develops into external auditory meatus

2nd through 4th clefts form temporary cervical sinuses, which are obliterated by proliferation of 2nd arch mesenchyme

persistent cervical sinus leads to branchial cleft cyst within the lateral neck

Front 202

cartilage derivatives of the first branchial arch

Back 202

Meckel's cartilage:
- Mandible
- Malleus
- incus
- sphenoMandibular ligament

Front 203

muscle derivatives of the first branchial arch

Back 203

Muscles of Mastication
- temporalis
- Masseter
- lateral and Medial pterygoids

Mylohyoid
anterior belly of digastric
tensor tympani
tensor veli palatini

Front 204

nerves derived from first branchial arch

Back 204

CN V2 and V3

remember: chew

Front 205

Treacher Collins syndrome

Back 205

first arch neural crest fails to migrate leading to mandibular hypoplasia and facial abnormalities

Front 206

cartilage derivatives of the second branchial arch

Back 206

Reichert's cartilage:
- Stapes
- Styloid process
- lesser horn of hyoid
- Stylohyoid ligament

Front 207

muscle derivatives of the second branchial arch

Back 207

muscles of facial expression
Stapedius
Stylohyoid
posterior belly of digastric

Front 208

nerve derivatives of the second branchial arch

Back 208

CN VII (facial expression)

smile

Front 209

cartilage derivatives of the third branchial arch

Back 209

greater horn of the hyoid

Front 210

muscle derivatives of the third branchial arch

Back 210

stylopharyngeus

remember: stylo-PHARYNGEUS is innervated by the glossoPHARYNGEAL nerve

Front 211

nerve derivatives of the third branchial arch

Back 211

CN IX (stylopharyngeus)

SWALLOW STYLishly

Front 212

congenital pharyngocutaneous fistula

Back 212

persistence of the third branchial cleft and pouch creating a fistula between the tonsillar area and the cleft in lateral neck

Front 213

cartilage derivatives of the 4-6th branchial arches

Back 213

thyroid cartilage
cricoid cartilage
arytenoids
corniculate cartilage
cuneiform cartilage

Front 214

muscle derivatives of the 4th branchial arch

Back 214

- most pharyngeal constrictors
- cricothyroid muscle
- levator veli palatini

Front 215

muscle derivatives of the 6th branchial arch

Back 215

all intrinsic muscles of the larynx except the cricothyroid

Front 216

nerve derivatives the 4th branchial arch

Back 216

CN X (superior laryngeal branch)

SIMPLY SWALLOW

Front 217

nerve derivatives of the 6th branchial arch

Back 217

CN X (recurrent laryngeal branch)

SPEAK

Front 218

what branchial arches form the posterior third of the tongue?

Back 218

arches 3 and 4

Front 219

what are the developmental contributions of the 5th branchial arch?

Back 219

arch 5 makes no major developmental contributions

Front 220

what are the only cranial nerves with both motor and sensory components?

Back 220

CN V3
CN VII
CN IX
CN X

Front 221

what is the acronym for the branchial arches?

Back 221

when at the golden ARCHES, children tend to first CHEW (1), then SMILE (2), then SWALLOW STYLishly (3) or SIMPLY SWALLOW (4), and then SPEAK (6)

Front 222

what are the derivatives of the 1st branchial pouch?

Back 222

middle ear cavity
eustachian tube
mastoid air cells

contributes to endoderm-lined structures of the ear

Front 223

what are the derivatives of the 2nd branchial pouch?

Back 223

epithelial lining of the palatine tonsil

Front 224

what are the derivatives of the 3rd branchial pouch?

Back 224

dorsal wings develop into inferior parathyroids

ventral wings develop into thymus

3rd pouch contributes to 3 structures (thymus, left and right inferior parathyroids)

3rd pouch structures end up below 4th pouch structures

Front 225

what are the derivatives of the 4th branchial pouch?

Back 225

dorsal wings develop into superior parathyroids

Front 226

what is the acronym for the derivatives of the branchial pouches?

Back 226

ear, tonsils, bottom-to-top:
1. contributes to endoderm-lined structures of the ear
2. contributes to epithelial lining of palatine tonsil
3. dorsal (bottom for inferior parathyroids)
3. ventral (to = thymus)
4. dorsal (top for superior parathyroids)

Front 227

what results from aberrant development of the third and fourth branchial pouches?

Back 227

DiGeorge syndrome
- cell deficiency (thymic aplasia)
- hypocalcemia (failure of parathyroid development)

Front 228

Multiple Endocrine Neoplasia (MEN) 2A

Back 228

associated with germline mutation of RET (affects neural crest cells)
- adrenal medullary tumor (pheochromocytoma)
- parathyroid (tumor): 3rd/4th pharyngeal pouch
- parafollicular cells (medullary thyroid cancer): derived from neural crest cells; associated with 4th/5th pharyngeal pouches

Front 229

tongue development

Back 229

1st branchial arch forms anterior 2/3
- sensation via CN V3
- taste via CN VII

3rd and 4th branchial arches form posterior 1/3
- sensation and taste mainly via CN IX
- in extreme posterior, it is via CN X

Front 230

what nerve is responsible for motor innervation of the tongue?

Back 230

CN XII

Front 231

from where are the muscles of the tongue derived?

Back 231

occipital myotomes

Front 232

nerves responsible for taste, pain, and motor innervation of the tongue

Back 232

taste:
- CN VII in front 2/3
- CN IX in posterior 1/3
- CN X in extreme posterior

pain:
- CN V3 in front 2/3
- CN IX in posterior 1/3
- CN X in extreme posterior

motor:
- CN XII

Front 233

thyroid development

Back 233

thyroid diverticulum arises from floor of primitive pharynx and descends into the neck

connected to tongue by thyroglossal duct, which normally disappears but may persist as pyramidal lobe of thyroid

foramen cecum is normal remnant of thyroglossal duct

Front 234

what is the most common site for ectopic thyroid tissue?

Back 234

tongue

Front 235

thyroglossal duct cyst

Back 235

midline neck cyst that moves with swallowing

vs. persistent cervical sinus leading to branchial cleft cyst in lateral neck

Front 236

cleft lip

Back 236

failure of fusion of the maxillary and medial nasal processes (formation of primary palate)

**often occurs with cleft palate**

Front 237

cleft palate

Back 237

failure of fusion of the lateral palatine processes, the nasal septum, and/or the median palatine process (formation of secondary palate)

**often occurs with cleft lip**

Front 238

what are the segments of the GI tract?

Back 238

1. foregut (pharynx to duodenum)
2. midgut (duodenum to transverse colon)
3. hindgut (distal transverse colon to rectum)

Front 239

what are the causes of developmental defects of the anterior abdominal wall?

Back 239

failure of:
- rostral fold closure: sternal defects
- lateral fold closure: omphalocele, gastroschisis
- caudal fold closure: bladder exstrophy

Front 240

duodenal atresia

Back 240

failure to recanalize

associated with trisomy 21

Front 241

jejunal, ileal, colonic atresia

Back 241

due to vascular accident

"apple peel atresia"

Front 242

midgut development

Back 242

6th week - midgut herniates through umbilical ring physiologically

10th week - midgut returns to abdominal cavity and rotates around superior mesenteric artery

Front 243

pathology of midgut development

Back 243

malrotation of midgut
omphalocele
intestinal atresia or stenosis
volvulus

Front 244

gastroschisis

Back 244

extrusion of abdominal contents through abdominal folds

not covered by peritoneum

Front 245

omphalocele

Back 245

persistence of herniation of abdominal contents into umbilical cord

covered by peritoneum

Front 246

tracheoesophageal fistula

Back 246

abnormal connection between esophagus and trachea

most common subtype is blind upper esophagus with lower esophagus connected to trachea (type C)

presentation:
- cyanosis
- choking/vomiting with feeding
- air bubble in stomach on CXR
- polyhydramnios
- failure to pass NG tube into stomach
- pneumonitis

Front 247

congenital pyloric stenosis

Back 247

hypertrophy of the pylorus that causes obstruction

presentation:
- palpable "olive" mass in epigastric region
- nonbilious projectile vomiting at about two weeks of age

treatment:
- surgical incision
epidemiology:
- 1/600 live births
- often in 1st born males

Front 248

pancreatic embryology

Back 248

derived from foregut

dorsal and ventral pancreatic buds contribute to the pancreatic head and main pancreatic duct

uncinate process is formed by the ventral bud alone

dorsal pancreatic bud becomes body, tail, isthmus, accessory pancreatic duct

ventral and dorsal buds fuse at 8 weeks

Front 249

annular pancreas

Back 249

ventral pancreatic bud abnormally encircles 2nd part of the duodenum

forms a ring of pancreatic tissue that may cause duodenal narrowing

Front 250

pancreas divisum

Back 250

ventral and dorsal pancreatic buds fail to fuse at 8 weeks

Front 251

embryology of the spleen

Back 251

arises from dorsal mesentery (thus mesodermal origin)

supplied by artery of foregut (celiac artery)

Front 252

kidney embryology

Back 252

development of the kidney proceeds through a series of successive phases, each marked by the development of a more advanced kidney: the pronephros, mesonephros, and metanephros

- pronephros is the most immature form of kidney
- metanephros is most developed
- metanephros persists as the definitive adult kidney

Front 253

what stage of the kidney persists as the definitive adult kidney?

Back 253

metanephros

Front 254

pronephros

Back 254

first stage of kidney development

most immature form of kidney

develops in the cervical region of the embryo

develops in week 4 and then degenerates

Front 255

mesonephros

Back 255

functions as interim kidney for first trimester

later contributes to male genital system

Front 256

metanephros

Back 256

permanent

beginnings first appear during the 5th week of gestation; nephrogenesis continues through 32-36 weeks of gestation

most mature kidney stage

Front 257

ureteric bud

Back 257

derived from caudal end of mesonephros

gives rise to ureter, pelvises, and calyces/collecting ducts (through branching)

fully canalized by the 10th week

Front 258

metanephric mesenchyme

Back 258

ureteric bud interacts with this tissue

interaction induces differentiation and formation of glomerulus and renal tubules to distal convoluted tubule

aberrant interaction btwn this and ureteric buds may result in several congenital malformations

Front 259

what is the most common site of obstruction (hydronephrosis) in a fetus?

Back 259

ureteropelvic junction with the kidney (it is the last to canalize)

Front 260

Potter's syndrome

Back 260

bilateral renal agenesis leading to oligohydramnios leading to limb deformities, facial deformities, and pulmonary hypoplasia

caused by malformation of ureteric bud

babies who can't "Pee" in utero develop Potter's syndrome

Front 261

horseshoe kidney

Back 261

inferior poles of both kidneys fuse

as they ascend from the pelvis during fetal development, horseshoe kidneys get trapped under inferior mesenteric artery and remain low in the abdomen

kidney functions normally

associated with Turner syndrome (XO)

Front 262

female genital embryology

Back 262

default development

mesonephric duct degenerates and paramesonephric duct develops

Front 263

male genital embryology

Back 263

SRY gene on Y chromosome produces testis-determining factor (testes development)

Mullerian inhibitory factor from Sertoli cells suppresses development of paramesonephric ducts

increased androgens from Leydig cells stimulates development of mesonephric ducts

mesonephric duct must be induced to remain; default program for embryo development is for paramesonephric duct to develop into female

Front 264

what is the gubernaculum?

Back 264

slender band, extending from that part of the skin of the groin which afterward forms the scrotum through the inguinal canal to the body and epididymis of the testis

Front 265

mesonephric (Wolffian) duct

Back 265

develops into male internal structures (except prostate)
- S-eminal vesicles
- E-pididymis
- E-jaculatory duct
- D-uctus deferens

remember: SEED

Front 266

paramesonephric (Mullerian) duct

Back 266

develops into female internal structures
- fallopian tubes
- uterus
- upper 1/3 of vagina

Mullerian duct abnormalities result in anatomical defects that may present as primary amenorrhea in females with fully developed secondary sexual characteristics (indicator of functional ovaries)

Front 267

bicornuate uterus

Back 267

results from incomplete fusion of the paramesonephric ducts

associated with urinary tract abnormalities and infertility

Front 268

5alpha-reductase deficiency

Back 268

male internal genitalia

ambiguous external genitalia until puberty

Front 269

SRY gene

Back 269

SRY gene on Y chromosome causes production of testis-determining factor, which leads to testes development

sertoli cells of the testes produce anti-mullerian hormone which causes degeneration of paramesonephric (mullerian) duct (female internal genitalia)

Leydig cells produce testosterone which causes male internal genitalia to develop from Wolffian ducts; testosterone is converted to DHT by 5alpha reductase, which then causes the genital tubercle and urogenital sinus to develop into male external genitalia and a prostate

Front 270

what is the result of a lack of sertoli cells or a lack of anti-Mullerian hormone?

Back 270

develop both male and female internal genitalia

develop male external genitalia

Front 271

what are the adult derivatives of the genital tubercle?

Back 271

in men: glans penis, corpus cavernosum, corpus spongiosum (via DHT)

in women: glans clitoris, vestibular bulbs (via estrogen)

Front 272

what are the adult derivatives of the urogenital sinus?

Back 272

in men: bulbourethral glands (of Cowper), prostate gland
- via DHT

in women: greater vestibular glands (of Bartholin), urethral and paraurethral glands (of Skene)
- via estrogen

Front 273

what are the adult derivatives of the urogenital folds?

Back 273

in men: ventral shaft of penis (penile urethra)
- via DHT

in women: labia minora

Front 274

what are the adult derivatives of the labioscrotal swelling?

Back 274

in men: scrotum (via DHT)

in women: labia majora (via estrogen)

Front 275

hypospadias

Back 275

abnormal opening of penile urethra on inferior (ventral) side of the penis due to failure of the urethral folds to close (remember: HYPO is below)

hypospadias are more common than epispadias

fix hypospadias to prevent UTIs

Front 276

epispadias

Back 276

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

remember: when you have Epispadias, you hit your Eye when you pEE

Front 277

what is exstrophy of the bladder?

Back 277

congenital anomaly in which part of the urinary bladder is present outside the body

Front 278

what is the female remnant of the gubernaculum?

Back 278

ovarian ligament and round ligament of the uterus

Front 279

what is the male remnant of the gubernaculum?

Back 279

band of fibrous tissue that anchors testes within the scrotum

Front 280

what is the female remnant of the processus vaginalis?

Back 280

N/A

the processus vaginalis is obliterated

Front 281

what is the male remnant of the processus vaginalis?

Back 281

tunica vaginalis

Front 282

what is the processus vaginalis?

Back 282

evagination of peritoneum