First Aid Embryology

Front 1

What anatomical region is the Sonic Hedgehog gene produced in, and what does it do?

Back 1

SHH is produced at the base of limbs, and are involved in patterning along anterior-posterior axis

Front 2

Where is the Wnt-7 gene produced and what is its function?

Back 2

Wnt-7 is produced at apical ectodermal ridge (@ distal end of developing limbs), and is necessary for proper organization along dorsal-ventral axis.

Front 3

Where is FGF produced and what is its function?

Back 3

FGF is produced at the apical ectodermal ridge, and it stimulates mitosis of underlying mesoderm thus lengthening limbs.

Front 4

What is the function of the Homeobox gene?

Back 4

It is involved in segmental organization

Front 5

What are the developmental landmarks associated with week 1 of fetal development?

Back 5

hCG secretion begins after implantation of blastocyst. and is detectable by ay 8 post-ovulation

Front 6

What are the developmental landmarks that occur in week 2 of fetal development?

Back 6

Development of the bilaminar disk (epiblast, hypoblast)

Front 7

What are the fetal landmarks associated with week 3 of fetal development?

Back 7

Gastrulation occurs. Primitive streak, notochord, and neural plate begin to form.
Epiblast invaginates to form primitive streak, primitive streak turns into mesoderm and endoderm.

Front 8

What are the fetal landmarks associated with week 4 of fetal development?

Back 8

Heart begins to beat, and 4 limb buds form

Front 9

What processes occur during the embryonic period (3-8 weeks)?

Back 9

Organogenesis, and closing of the neural tube. Teratogens are extremely harmful during this period.

Front 10

What is the difference between the the alar plate and the basal plate?

Back 10

Alar plate is located on the dorsal part of the neural tube and develops into sensory neurons.
Basal plate is ventral and becomes motor neurons.

Front 11

What are the three sublayers of ectoderm?

Back 11

Surface ectoderm, neuroectoderm, and neural crest

Front 12

What develops from the surface ectoderm?

Back 12

Adenohypophysis, lens, lining of oral cavity, inner ear, retina, olfactory epithelium, epidermis, salivary, sweat and mammary glands.

Front 13

What develops from the neuroectoderm?

Back 13

Brain, retina and spinal cord

Front 14

What develops from the neural crest?

Back 14

Peripheral Nervous System and non-neural structures nearby (ANS, odontoblasts dorsal root ganglia, cranial nerves, celiac ganglion, melanocytes, chromaffin cells, schwann cells, etc).

Front 15

What develops from the endoderm?

Back 15

Gut tube epithelium and derivatives (lungs, liver, pancreas, thymus, parathyroid, thyroid follicular cells, etc).

Front 16

What develops from the mesoderm?

Back 16

Muscle, bone, connective tissue, serous linings of the body cavities, spleen, cardiostructures, blood, lymphatics, kidneys, adrenals.

Front 17

What are the main mesodermal defects seen in fetal development?

Back 17

VACTERL
Vertebral, Anal, Cardiac, Tracheo-Esophageal, Renal, and Limb defects

Front 18

Describe the type of effects teratogens can have on a fetus depending on when they are introduced (ie, before 3 wks, btwn 3-8 wks, after 8 wks)

Back 18

Before 3 weeks: all or none effects
3-8 wks: altered organogenesis,
after 8 weeks - growth and function affected

Front 19

What are the teratogenic effects of ACE inhibitors?

Back 19

Renal damage

Front 20

What are the teratogenic effects of alcohol?

Back 20

Leading cause of birth defects and mental retardation; fetal alcohol syndrome

Front 21

What are the teratogenic effects of alkylating agents?

Back 21

Absence of digits, multiple anomalies.

Front 22

What are the teratogenic effects of aminoglycosides?

Back 22

CN VIII toxicity

Front 23

What are the teratogenic effects of cocaine?

Back 23

Abnormal fetal development/fetal addiction and placental abruption

Front 24

What are the teratogenic effects of DES?

Back 24

Vaginal clear cell adenocarcinoma.

Front 25

What are the teratogenic effects of folate antagonists?

Back 25

Neural tube defects

Front 26

What are the teratogenic effects of Iodide?

Back 26

Congenital goiter or hypothyroidism

Front 27

What are the teratogenic effects of Lithium?

Back 27

Ebstein's anomaly (atrialized right ventricle)

Front 28

What are the teratogenic effects of maternal diabetes?

Back 28

Caudal regression syndrome (anal atresia to sirenomelia).

Front 29

What are the teratogenic effects of smoking?

Back 29

preterm labor, placental problems, IUGR, ADHD

Front 30

What are the teratogenic effects of tetracyclines?

Back 30

Discolored teeth

Front 31

What are the teratogenic effects of Thalidomide?

Back 31

Limb defects

Front 32

What are the teratogenic effects of valproate?

Back 32

Inhibition of intestinal folate absorption

Front 33

What are the teratogenic effects of Vitamin A excess?

Back 33

Spontaneous abortions and birth defects

Front 34

What are the teratogenic effects of Warfarin?

Back 34

Bone deformities, fetal hemorrhage, abortion

Front 35

What are the teratogenic effects of X-rays and anticonvulsants?

Back 35

multiple anomalies

Front 36

Fetal alcohol syndrome is the leading cause of congenital malformations in the US. what are some associated malformations and what is the mechanism?

Back 36

Developmental retardation, microcephaly, holoprosencephaly, facial abnormalities, limb dislocation, heart and lung fistulas, are probably caused by inhibition of cell migration

Front 37

If twins split before Day 3 of fetal development, how many chorion and amnion will be present?

Back 37

If twins split before 3 days, there will be 2 chorion, 2 amnion, and possibly 2 placenta

Front 38

If twins split between day 3 and day 8 of fetal development, how many chorion and amnion will be present?

Back 38

There will be 1 chorion, and 2 amnion

Front 39

If twins split after Day 8 of fetal development, how many chorion and amnion will be present?

Back 39

1 chorion, and 1 amnion.
Day 3 chorion is established
Day 8 amnion is established.

Front 40

What are the fetal components of the placenta, and what do they do?

Back 40

Cytotrophoblast is the inner layer of chorionic villi, and it differentiates into other forms of trophoblastic tissue.

Syncytiotrophoblast - outer layer of chorionic villi, secretes hCG.

Front 41

What is the maternal component of placenta and what does it do?

Back 41

Decidua basalis - derived from endometrium and has maternal blood in lacunae.

Front 42

Name the blood vessels in the umbilical cord.

Back 42

There are 2 umbilical arteries which return deoxy fetal blood to placenta.

There is one umbilical vein that supplies oxy blood from placenta to fetus.

Front 43

What are other components of the umbilical cord?

Back 43

Urachal duct - develops from the allantois/yolk sac at week 3, and goes from bladder to yolk sac.
Wharton's jelly and amniotic epithelium bind all the umbilical components together.

Front 44

What are the abnormalities that can affect the urachal duct?

Back 44

Patent urachus - urine out the bellybutton
Vesicourachal diverticulum - outpouching of bladder.

Front 45

What is the vitelline duct, and what are some of its associated abnormalities?

Back 45

Vitelline duct connects the yolk sac to the midgut week, and is obliterated @ 7th wk.
Vitelline fistula - failure of the duct to close @ 7 wks, and meconium is discharged from umbilicus.

Front 46

Truncus arteriosus develops into what structures in a grown adult?

Back 46

Ascending aorta and pulmonary trunk

Front 47

Bulbus cordis develops into what structure in a grown adult?

Back 47

Right ventricle and smooth parts of left and right ventricles.

Front 48

Primitive ventricle develops into what structure in a grown adult?

Back 48

A portion of the left ventricle

Front 49

Primitive atria develop into what structure in a grown adult?

Back 49

Trabeculated left and right atria

Front 50

Left horn of sinus venosus develops into what structure in a grown adult?

Back 50

Coronary sinus

Front 51

Right horn of sinus venosus develops into what structure in a grown adult?

Back 51

Smooth part of right atrium

Front 52

The right common and anterior cardinal veins develop into what structure in a grown adult?

Back 52

superior vena cava

Front 53

Describe the development of the truncus arteriosus, and name some common abnormalities that can happen.

Back 53

Neural crest migration divides the trunk into 2 arteries via fusion and twisting of truncal and bulbar ridges, eventually becoming the ascending aorta and pulmonary trunk.
Common abnormalities include transposition of great vessels and tetralogy of fallot

Front 54

Describe how the truncus arteriosus is divided into the aortic and pulmonary trunks.

Back 54

The aorticopulmonary septum develops in the truncus arteriosus and spirals downwards, joining the muscular ventricular septum and closing the interventricular septum

Front 55

Describe the steps of interatrial septum development.

Back 55

1. Foramen primum narrows as septum primum grows towards endocardial cushions.
2. Perforations in septum primum form foramen secundum.
3. Foramen secundum maintains right to left shunt as septum secundum grows down from the top of the heart.
4. Septum secundum contains a permanent opening (foramen ovale)
5. Foramen secundum enlarges and upper part of septum primum degenerates.
6. Remaining part of foramen primum turns into valve of foramen ovale

Front 56

Where does fetal erythropoesis occur throughout the course of fetal development?

Back 56

1. Yolk sac 3-8 wks
2. Liver 6-30 wks
3. Spleen 9-28 wks
4. Bone marrow from 28 wks on.
(Young Liver Synthesizes Blood)

Front 57

What is the O2 sat of the blood in the umbilical vein?

Back 57

80%-- umbilical arteries have low O2 sat.

Front 58

What/where are the 3 important shunts of fetal circulation?

Back 58

1. Ductus venosus - shunts from umbilical vein to IVC
2. Foramen ovale - shunts blood from IVC across atria to aorta
3. Ductus arteriosus - Deoxy blood is shunted from pulmonary artery to descending aorta

Front 59

What happens to the cardiovasculature when the baby takes its first breath at birth?

Back 59

Breath creates negative pressure in pulmonary vasculature. Right atrial pressure drops and foramen ovale closes.
Rise in O2 causes decrease in PDA-opening prostaglandins. (Indomethacin can also be used to help close PDA).

Front 60

What post-natal structure arises from the umbilical vein?

Back 60

ligamentum teres hepatis (contained in falciform ligament)

Front 61

What post-natal structure arises from the umbilical arteries?

Back 61

medial umbilical ligaments

Front 62

What post-natal structure arises from the ductus arteriosus?

Back 62

ligamentum arteriosum

Front 63

What post-natal structure arises from the ductus venosus?

Back 63

ligamentum venosum

Front 64

What post-natal structure arises from the foramen ovale?

Back 64

fossa ovalis

Front 65

What post-natal structure arises from the allantois?

Back 65

urachus/ median umbilical ligament

Front 66

What post-natal structure arises from the notochord?

Back 66

nucleus pulposus of intervertebral disk.

Front 67

Name the aortic arch derivatives.

Back 67

1. first part of maxillary artery
2. stapedial and hyoid arteries
3. common carotid artery and proximal part of ICA.
4. on left, aortic arch. on right, proximal right subclavian artery
6. proximal part of pulmonary arteries and ductus arteriosus

Front 68

The fetal brain starts as prosencephalon, mesencephalon, and rhombencephalon. Describe how these regions develop into the adult brain.

Back 68

Prosencephalon:
Telencephalon - cerebral hemispheres
Diencephalon - thalami

Mesencephalon - midbrain

Rhombencephalon:
Metencephalon - pons,cerebell
Myelencephalon - Medulla

Front 69

What are the common neural tube defects and what are their presentations?

what substances are elevated and where?

Back 69

Neuropores unfused - fistula btwn amniotic cavity and spinal canal. Elevated AFP and acetylcholinesterase in CSF.
Spina bifida oculta - failure of spinal canal to close. usu @ lower vertebra. Dura is intact.
Meningocele - meninges herniate through spinal canal defect.
Myelomeningocele - meninges and spinal cord herniate through spinal canal defect

Front 70

What are some common forebrain anomalies and their presentations?

Back 70

Anencephaly - anterior end of neural tube is messed up. No brain/calvarium, elevated AFP.

Holoprosencephaly - hemispheres are fused together, cyclopia, Patau's syndrome, FAS and cleft lip

Front 71

What are the posterior fossa malformations and what are their presentations?

Back 71

Arnold-Chiari II - cerebellar tonsil herniation through foramen magnum w/ aqueductal stenosis and hydrocephalus.
Dandy-Walker - large posterior fossa and absent cerebellar vermis w/ enlargement of 4th ventricle. Can lead to hydrocephalus and spina bfida

Front 72

What is syringomyelia and what are its symptoms?

Back 72

Syringomyelia is an enlargement of the central canal of spinal cord. Spinothalamic tract is damaged first. "Cape like" bilateral loss of pain and temperature in upper extremities, whereas touch is preserved

Front 73

Which germ cell layers give rise to branchial clefts, arches and pouches?

Back 73

Branchial clefts - ectoderm
Branchial arches - mesoderm and neural crests
Branchial pouches - endoderm

Front 74

Describe the function and innervation of each branchial arch.

Back 74

Arch 1 - chewing, CN V2 and V3
Arch 2 - facial expression, VII
Arch 3 - stylopharyngeus, IX
Arch 4 - swallowing, X
Arch 6 - speaking, X

Front 75

What do the branchial clefts develop into?

Back 75

1st cleft develops into external auditory meatus
2nd-4th clefts become temporary cervical sinuses (which are eventually obliterated by 2nd arch mesenchyme)

Front 76

What do the branchial pouches develop into?

Back 76

1st pouch - middle ear cavity, eustachian tube, mastoid cells
2nd pouch - epithelial lining of palatine tonsil
3rd pouch - inferior parathyroids and thymus
4th pouch - superior parathyroids

Note: 3rd pouch structures end up BELOW 4th pouch structures

Front 77

What are some diseases that can arise from malfunction of the branchial pouches?

Back 77

DiGeorge Syndrome - aberrant development of 3rd and 4th pouches causes T-cell deficiency and hypocalcemia.

MEN2A mutation of RET neural cells causes tumors:
Adrenal Medulla (pheochromocytoma)
Parathyroid - 3rd/4th pouch
Parafollicular cells - 4th/5th

Front 78

In terms of ear development, what arises from the 1st arch?

Back 78

Malleus/incus bones, and tensor tympani (innervated by V3)

Front 79

In terms of ear development, what arises from the 2nd arch?

Back 79

Stapes bone, Stapedius (VII)

Front 80

In terms of ear development, what arises from the 1st cleft?

Back 80

external auditory meatus

Front 81

In terms of ear development, what arises from the 1st branchial membrane?

Back 81

tympanic membrane

Front 82

In terms of ear development, what arises from the 1st pouch?

Back 82

Eustachian tube, middle ear cavity, mastoid air cells

Front 83

In terms of tongue development, what arises from the 1st branchial arch?

Back 83

anterior 2/3rds of tongue (sensation via V3, taste via CN VII)
Motor innervation of tongue is XII

Front 84

In terms of tongue development, what arises from the 3rd and 4th arches?

Back 84

posterior 1/3rd (sensation and taste via CN IX, and X on the very back end of tongue)

Front 85

What is the thyroglossal duct and what is its relevance to a fully developed adult?

Back 85

Foramen cecum is normal remnant of thyroglossal duct.
A thyroglossal duct cyst is on midline and will move w/ swallowing.

Front 86

What is the difference between cleft lip and cleft palate?

Back 86

Cleft lip - failure of fusion of the maxillary and medial nasal processes (primary palate)

Cleft palate - failure of fusion of the lateral palatine, nasal septum and median palatine process (secondary palate)

Front 87

What are the components that make up the diaphragm?

Back 87

Several Parts Build Diaphragm.
1. Septum transversum --> central tendon
2. Pleuroperitoneal folds
3. Body wall
4. Dorsal mesentary of esophagus (crura)

Innervated by C3, 4, and 5.

Front 88

Describe which structures arise from the foregut, midgut, and hindgut.

Back 88

Foregut - pharynx to duodenum
Midgut - duodenum to trans colon
Hindgut - trans colon to rectum.

Front 89

Describe some of the typical developmental defects caused by failure of:
- rostral fold closure
- lateral fold closure
- caudal fold closure

Back 89

Rostral fold closure - sternal defects
Lateral fold closure - omphalocele, gastroschisis
Caudal fold closure - bladder exstrophy

Front 90

What is the cause of duodenal atresia?

Back 90

failure to recanalize, usually due to trisomy 21

Front 91

What is the cause of jejunal, ileal, colonic atresia?

Back 91

usually due to vascular accidents (apple peel atresia), which cause ischemia to developing parts of the bowel

Front 92

What happens between 6th and 10th weeks with regards to GI development?

Back 92

at 6th week, midgut herniates through umbilical ring and grows rapidly. At 10th week, midgut returns to abdominal cavity and rotates around SMA.

Front 93

What is a tracheoesophageal fistula?

Back 93

An abnormal connection between esophagus and trachea. Usually involves a blind upper esophagus with lower esophagus connected to trachea. Causes cyanosis, choking and vomiting.

Front 94

What are the symptoms of congenital pyloric stenosis and what is its etiology?

what types of pt are most suspectible?

Back 94

Hypertrophy of the pylorus causes obstruction. Results in palpable epigastric mass and nonbilious projectile vomiting. Usually in 1st born males, happens 1/600 births.

Front 95

Describe the embryology of pancreatic development and some common problems that can occur.

Back 95

Pancreas is derived from the foregut. Ventral pancreatic bud becomes pancreatic head and main pancreatic duct. Dorsal pancreatic bud becomes everything else.

Annular pancreas - ventral pancreatic bud circles 2nd part of duodenum and constricts it
Pancreas divisum - ventral and dorsal parts don't fuse @ 8 wks

Front 96

What gives rise to the spleen and what is the spleen's blood supply?

Back 96

The dorsal mesentary (mesoderm) gives rise to the spleen and it is supplied by the celiac artery (artery of the foregut)

Front 97

What are the stages of embryologic kidney development?

Back 97

1. Pronephros - week 4, then degenerates
2. Mesonephros - interim kidney for 1st trimester, later contributes to male genitals
3. Metanephros - permanent. develops from 5-36 wks. Ureteric bud - ureter, pelvises, canalized by 10th wk
Mesenchyme - interacts w bud and induces formation of glomerulus and tubules.

Front 98

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

Back 98

Uteropelvic junction with kidney is the last to canalize and the most common site of obstruction.

Front 99

Describe the pathogenesis and symptoms of Potter's syndrome.

Back 99

Renal agenesis --> oligohydramnios --> limb and face deformities, pulmonary hypoplasia
Caused by malformation of ureteric bud

Front 100

Describe the pathogenesis and symptoms of horseshoe kidney.

Back 100

Inferior poles of both kidneys fuse and get trapped under inferior mesenteric artery. So they are low in abdomen but function normally

Front 101

Describe the process of female genital embryology and the fate of the mesonephric duct.

Back 101

Mesonephric duct degenerates (it must be induced to remain), and paramesonephric duct develops into female genitals.

Front 102

Describe the embryology of male genitals, particularly the impact of sertoli and leydig cells.

Back 102

SRY gene codes for testis determining factor.

Sertolli cells - secrete mullerian inhibiting factor, which inhibits development of paramesonephrics

Leydig cells - increase androgens develops mesonephric ducts

Front 103

Which genital structures does the mesonephric duct develop into?

Back 103

Seminal vesicles, Epididymis, Ejaculatory duct, and Ductus Deferens

Front 104

What genital structures arise from the Paramesonephric duct?

Back 104

Develops into fallopian tube, uterus, and upper 1/3 of vagina.

Front 105

What is a bicornuate uterus and what are its implications?

Back 105

Bicornuate uterus is a "heart shaped" uterus resulting from incomplete fusion of the paramesonephric ducts. It is associated with urinary tract abnormalities and infertility.

Front 106

What does the genital tubercle give rise to when exposed to DHT vs when exposed to estrogen?

Back 106

DHT - glans penis, corpus cavernosum and spongiosum
Estrogen - Glans clitoris and vestibular bulbs

Front 107

What does the urogenital sinus give rise to when exposed to DHT and when exposed to estrogen?

Back 107

DHT - bulbourethral glands and prostate gland
Estrogen - Greater vestibular, urtehral, and paraurethral glands.

Front 108

What does the urogenital folds give rise to when exposed to DHT and when exposed to estrogen?

Back 108

DHT - ventral shaft of penis
Estrogen - Labia minora

Front 109

What does the labioscrotal swelling give rise to when exposed to DHT and when exposed to estrogen?

Back 109

DHT - scrotum
Estrogen - labia majora

Front 110

What are hypospadias and epispadias, and which one occurs more frequently?

Back 110

Hypospadia is when the urethra opens on the inferior side of the penis, because urethral folds fail to close. Risk of UTIs
Epispadias - urethra opens on dorsal penis due to faulty positioning of genital tubercle. Risk of exstrophy of bladder.

Hypospadias is more common.

Front 111

Which cartilage, muscles, nerves, arteries, and abnormalities are derived from branchial arch 1?

Back 111

Cartilage - Mandible, Malleus, Mandibular ligament
Muscles - Muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini, ant 2/3rds of tongue.
Nerves - CN V2 and V3
Arteries - Maxillary
Disease - Treacher Collins Syndrome --> mandibular hypoplasia and facial abnormalities.

Front 112

Which cartilage, muscles, nerves, arteries, and abnormalities are derived from branchial arch 2?

Back 112

Cartilage - stapes, styloid process, lesser horn of hyoid, stylohyoid ligament
Muscles - muscles of facial expression, stapedius, stylohyoid, posterior belly of digastric
Nerves - CN VII
Artery - Stapedial artery, hyoid artery

Front 113

Which cartilage, muscles, nerves, arteries, and abnormalities are derived from branchial arch 3?

Back 113

Cartilage - greater horn of hyoid
Muscle - stylopharyngeus
Nerves - CN IX
Diseases - pharyngocutaneous fistula links tonsils and the lateral neck cleft

Front 114

Which cartilage, muscles, nerves, arteries, and abnormalities are derived from branchial arch 4-6?

Back 114

Cartilage - thyroid, cricoid, arytenoids, corniculate, cuneiform
Muscles from 4 - pharyngeal constrictors, cricothyroid, levator veli palatini
Muscles from 6 - all intrinsic muscles of larynx except cricothyroid
Arches 3 and 4 form the posterior 1/3 of tongue.

Nerves from 4 - CN X, superior laryngeal branch (swallowing)
Nerves from 6 - CN X, recurrent laryngeal branch (speaking)

Front 115

What does the notochord become in adults?

Back 115

nucleus pulposus of the intervertebral disk

Front 116

2nd week
a. how many germ layers
b. how many cavities
c. how many components to the placenta

Back 116

Rule of 2's
a. 2 germ layers - epiblast and hypoblast
b. 2 cavities - amniotic cavity and yolk sac
c. 2 components to the placenta - cytotrophoblast, syncytiotrophoblast

Front 117

Epiblast

part of what structure?

what does it give rise to?

Back 117

bilaminar disk

ectoderm

Front 118

Invagination of epiblast forms what?

this gives rise to what layers?

Back 118

primitive streak

mesoderm and part of the endoderm

Front 119

3rd week

how many germ layers

Back 119

Rule of 3

3rd week = 3 layers
ectoderm, mesoderm, endoderm

Front 120

When do you first see four heart chambers and four limb buds?

Back 120

Fourth week (rule of 4)

Front 121

Types of errors in organ morphogenesis

Malformation

Back 121

Intrinsic disruption occurring in embryonic period (wks 3-8)

Front 122

Types of errors in organ morphogenesis

Deformation

Back 122

Extrinsic disruption, occurs after embryonic period

Front 123

Types of errors in organ morphogenesis

Agenesis

Back 123

Absent organ due to absent primordial tissue

Front 124

Types of errors in organ morphogenesis

Hypoplasia

Back 124

Primordial tissue present, but incomplete organ development

Front 125

Types of errors in organ morphogenesis

Aplasia

Back 125

Primordial tissue present, but absent organ