Step 1 Embryology

Front 1

Fetal Landmark: Day 0

Back 1

Fertilization by sperm forming zygote, initiating embryogenesis

Front 2

Fetal Landmark: Day 3

Back 2

Morula

Front 3

Fetal Landmark: Day 5

Back 3

Blastocysts

Front 4

Fetal Landmark: Day 6

Back 4

Implantation

Front 5

Fetal Landmark: within week 2

Back 5

Bilaminar disk (epiblast and hypoblast)

Front 6

Fetal landmark: within week 3

Back 6

Gastrulation - establishes 3 germ layers
Primitive streak
Notochord and neural plate begin to form

Front 7

Fetal landmark: week 3-8

Back 7

Neural tube formed
Organogenesis
Extremely susceptible to teratogens

Front 8

Fetal Landmark: Week 4

Back 8

heart begins to beat
upper and lower limb buds begin to form

Front 9

Fetal Landmark: Week 8

Back 9

Fetal movement; fetus looks like a baby

Front 10

Fetal landmark: week 10

Back 10

Genitalia have male/female characteristics

Front 11

Alar plate (dorsal)

Back 11

Sensory

Front 12

Basal plate (ventral)

Back 12

Motor

Front 13

Rule of 2's for 2nd week

Back 13

2 germ layers (bilaminar disk)
2 cavities: amniotic cavity and yolk sac
2 components to the placenta: cytotrophoblast and syncytiotrophoblast

Front 14

Rule of 3's for 3rd week

Back 14

3 germ layers (gatrula): ectoderm, mesoderm, and endoderm

Front 15

Rule of 4's for 4th week

Back 15

4 heart chambers
4 limb buds grow

Front 16

Surface ectoderm

Back 16

Adenohypophysis; lens of eye; epithelial linings of skin, ear, eye, and nose; epidermis

Front 17

Surface ectoderm

Back 17

Adenohypophysis; lens of eye; epithelial linings of skin, ear, eye, and nose; epidermis

Front 18

Neuroectoderm

Back 18

Neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland

Front 19

Neural crest

Back 19

ANS, dorsal root ganglia, melanocytes, chromaffin cells of adrenal medulla, enterochromaffin cell, pia and arachnoid, celiac ganglion, Schwann cells, odontoblasts, parafollicular (C) cells of thyroid, laryngeal cartilage, bones of the skull

Front 20

Endoderm

Back 20

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

Front 21

Mesoderm

Back 21

Dura mater, connective tissue, muscle, bone, cardiovascular structures, lymphatics, blood, urogenital structures, serous linings of body cavities (peritoneal) spleen, adrenal cortex, and kidneys

Hint 21

Mesodermal defects = VACTERL = Caudal Dysplasia
V: Vertebral defect
A: Anal atresia
C: cardiac defect
T: tracheo-espophageal fistula
R: renal defects
L: limb defects (bone and muscle)

Front 22

Teratogen: ACE inhibitors

Back 22

Renal Damage

Front 23

Teratogen: Cocaine

Back 23

Abnormal fetal development and fetal addiction
(Placental abruption)

Front 24

Teratogen: Diethylstilbestrol (DES)

Back 24

Vaginal clear cell adenocarcinoma

Front 25

Teratogen: Iodide

Back 25

Congenital goiter of hypothyroidism

Front 26

Teratogen: Vitamin A

Back 26

extremely high risk for birth defects
(retinoic acid derivative)

Front 27

Teratogen: Thalidomide

Back 27

Limb defects (flipper limbs)

Front 28

Teratogen: Tobacco

Back 28

Preterm labor, placental problems, ADHD
(Hypoxia- decrease uterine blood flow)

Front 29

Teratogen: Warfarin, x-rays, and anticonvulsants

Back 29

Multiple anomalies

Front 30

Fetal alcohol syndrome

Back 30

Leading cause of congenital malformations in US. Newborns have an increased incidence of pre and postnatal development retardation, microcephaly, facial abnormalities, limb dislocation, and heart and lung fistulas.
* Mechanism may be decrease or inhibition of cellular migration

Front 31

Monozygotic twins

Back 31

1 zygote splits evenly to develop 2 amniotic sacs within a single common chorion and placenta

Front 32

Dizygotic or monozygotic

Back 32

Monozygotes taht split early develop 2 placentas, chorions, and amniotic sacs.

Dizygotic develop individual placentas, chorions, and amniotic sacs

Front 33

Placental development

Back 33

primary site of nutrient and gas exchange between mother and fetus
*Fetal: Cytotrophoblast composes the inner layer of chorionic villi. Syncytiotrophoblast is the outer layer and secretes hCG
Maternal: Decidua basalis derived from endometrium

Front 34

Umbilical cord

Back 34

Contains 2 umbilical arteries, which return deoxygenated blood from fetal internal iliac arteries, and 1 umbilical vein, with supplies oxygenated blood from the placenta to the fetus

Hint 34

A single umbilical artery is associated with congenital and chromosomal abnormalities

Front 35

urachus

Back 35

removes nitrogenous wastes from fetal bladder (like urethra)

Hint 35

urachus connects fetal bladder with allantois. Umbilical arteries and veins are derived from the allantois

Front 36

What does the Truncus arteriosus (TA) become?

Back 36

Ascending aorta and pulmonary trunk

Front 37

What does the Bulbus cordis become?

Back 37

Smooth pars of the left and right ventricle.

Front 38

What does the Primitive ventricle become?

Back 38

Trabeculated parts of the left and right ventricle

Front 39

What does the primitive atria become?

Back 39

Trabeculated left and right atrium

Front 40

What does the left horn of sinus venous become?

Back 40

Coronary sinus

Front 41

What does the right horn of the Sinus venous become?

Back 41

Smooth pars of right atrium

Front 42

What does the right common cardinal vein and right anterior cardinal vein become?

Back 42

SVC

Front 43

Development of the Interventricular septum

Back 43

1. Muscular ventricular septum froms. Opening is called the interventricular foramen.
2. The aorticopulmonary septum divides the truncus arteriosis into the aortic and pulmonary trunks.
3. The aorticopulmonary septum meets and fuses with the muscular ventricular septum to form the membranous interventricular septum, closing the interventricular foramen

Front 44

Interatrial septum development

Back 44

1. Foramen primum narrows as the septum primum grows toward the endocardial cushion
2. Perforations in the septum primum form the foramen secundum as the foramen primum disappears
3.forman secundum maintains the right to left shunt as the septum secundum begins to grow
4.The septum secundum contains the opening (foramen ovale)
5. The foramen secundum enlarges and the upper part of the septum primum degenerates
6. the remaining septum primum is now called the valve of the formen ovale

Front 45

Fetal erythropoiesis occurs in:

Back 45

1. yolk sac: (3-8 weeks)
2. liver (6-30 wks)
3. Spleen (9 - 28 wks)
4. Bone marrow (28 wks - +)

Hint 45

Young Liver Synthesizes Blood
fetal hemoglobin: alpha and gamma
adult: alpha and beta

Front 46

In fetal circulation, do the umbilical veins or umbilical arteries have high O2 content?

Back 46

Blood in umbilical vein is 80% saturated with O2. Umbilical arteries have low O2 saturation

Front 47

The Three important shunts in fetal circulation?

Back 47

1. Ductus venosus- blood entering the fetus through the umbilical vein is conducted via the DV into the IVC
2. Foramen ovale- most oxygenated blood reaching the heart via the IVC is diverted through the FO and pumped out the aorta to the head and body
3. Ductus arteriosus- deoxygenated blood from the SVC is expelled into the pulmonary artery and DA to the lower body of the fetus

Hint 47

at birth, the first breath dec. resistance in pulmonary vasculature causing increase left atrial pressure vs. right atrial pressure-foramen ovale closes = fossa ovalis
- increase O2 leads to decrease in prostaglandins, causing closure of ductus arteriosus

Front 48

what does the umbilical vein become?

Back 48

ligamentum teres hepatis
(contained to the falciform ligament)

Front 49

What does the umbilical arteries become?

Back 49

the medial umbilical ligament

Front 50

What does the ductus arteriosus become?

Back 50

ligamentum arteriosum

Front 51

What does the ductus venosus become?

Back 51

ligamentum venosum

Front 52

What dose the foramen ovale become?

Back 52

fossa ovalis

Front 53

What does the allantois become?

Back 53

The urachus- median umbilical ligament

Front 54

what does the notochord become?

Back 54

nucleus pulposus of intervertebral disk

Front 55

1st Aortic Arch derivative?

Back 55

part of the MAXillary artery

Hint 55

First arch is MAXimal

Front 56

The derivative of the 2nd aortic arch?

Back 56

Stapedial artery and hyoid artery

Hint 56

Second = Stapedial

Front 57

The derivative of the third aortic arch?

Back 57

common Carotid artery and proximal part of internal carotid artery

Hint 57

C is the third letter in the alphabet

Front 58

The derivative of the 4th aortic arch?

Back 58

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

Hint 58

4th arch - 4 limbs - systemic

Front 59

The derivative of the 6th aortic arch?

Back 59

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

Hint 59

6th arch = pulmonary and the pulmonary to systemic shunt (DA)

Front 60

What composes the brachial (pharyngeal) apparatus?

Back 60

brachail clefts, arches, and pouches
Clefts = ectoderm
arches - mesoderm
pouches = endoderm

Hint 60

CAP - Cleft/Arch/ Pouch
Ecto/Meso/Endo
*Clefts also called grooves

Front 61

Brachial arch 1 derivatives?

Back 61

Meckel's cartilage
Manible
Malleus and incus
sphenoMandibular ligament
Muscles of Mastication
Mylohyoid and anterior belly of digastric, tensor tympani, tensor veli palantini, anterior 2/3 of the tongue.
NERVES: CN V2 and V3

Front 62

What are the muscles of mastication?

Back 62

termporalis, Masseter, later and medial pterygoids

Front 63

Derivatives of brachial arch 2

Back 63

Reichert's cartilage, Stapes, Styloid process, lesser horn of hyoid, Stylohyoid ligament
Muscles of facial expression, Stapedius, Stylohyoid, posterior belly of digastric
NERVE: CN VII

Front 64

Brachial arch 3 derivatives

Back 64

Cartilage: greater horn of hyoid
Muscle: stylopharyngeus
Nerve: CN IX

Hint 64

Think of pharynx:
stylopharyngeus innervated by glossopharyngeal nerve

Front 65

Brachial arch 4- 6 derivatives

Back 65

Cartilages: thyroid, cricoid, arytenoids, corniculate, cuneiform
Muscles (4th): most of pharyngeal constrictors, cricothyroid, levator veli palantini
6th: all intrinsic muscles of the larynx expcept cricothyroid
NERVE: 4- CN X - superior laryngeal branch
6- CNX - recurrent laryngeal branch

Front 66

Brachial arch innervations

Back 66

1: CNV2 and CNV3
2: CNVII
3: CNIX
4: CNX
6: CNX

Hint 66

These cranial nerves are the only ones with both a sensory and motor component (except V2)

Front 67

Brachial cleft derivatives

Back 67

1st cleft = external auditory meatus
2-4th clefts = temporary cervical sinuses, which are obliterated by the proliferations of 2nd arch mesenchyme

Front 68

1st Brachial pouch

Back 68

develops into middle ear cavity; eustachian tube, and mastoid air cells

Hint 68

1st pouch contributes to endoderm-lined structures of the ear

Front 69

2nd brachial pouch

Back 69

develops into epithelial lining of palatine tonsil

Front 70

3rd brachial pouch

Back 70

(dorsal wing) develops into inferior parathyroids

Hint 70

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

Front 71

3rd brachial pouch (ventral wings)

Back 71

develop into thymus

Front 72

4th brachial pouch

Back 72

(dorsal wing) develops into superior parathyroids

Front 73

Aberrant development of 3rd and 4th pouches leads to what problems

Back 73

1. DiGeorge syndrome
2.leads to T-cell deficiency (thymic aplasia)
3. hypocalcemia (failure of parathyroid development)

Front 74

Ear Development

Back 74

Bones: Malleus, Incus, Stapes
Muscles: Tensor Tympani (V3)
Stapedius (VII)
Origin: 1st and 2nd arch, 1st cleft, and 1st brachial membrane

Front 75

Tongue development
anterior 2/3 of tongue

Back 75

1st brachial arch forms anterior 2/3 of tongue
Sensation: CNV3
Taste: CNVII

Front 76

Tongue Development
posterior 1/3 of tongue

Back 76

3rd and 4th arches form the posterior 1/3
Sensation and taste: CNIX
Extreme posterior: CN X

Front 77

Motor innervation of tongue

Back 77

CN XII

Front 78

Innervation for taste

Back 78

CN VII, IX, X

Front 79

Innervation for pain in the tongue

Back 79

CN V3, IX, X

Front 80

Thyroid Development

Back 80

Thyroid diverticulum arises from the floor of primitive pharynx, descends into neck, thyroglossal duct connects the two. The foramen cecum is the normal remnant of the thyroglossal duct.

Hint 80

Most common ectopic thyroid tissue site is the tongue

Front 81

Cleft Lip

Back 81

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

Front 82

Cleft Palate

Back 82

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

Front 83

What is the diaphragm derived from?

Back 83

1. Septum transversum
2. Pleuroperitoneal folds
3. Body Wall
4. Dorsal mesentery of esophagus

Hint 83

Several Parts Build Diaphragm
Diaphragm descends during development so its innervation comes from above (C3,4,5 Keep the Diaphragm alive)

Front 84

Where is the pancreas derived from?

Back 84

Pancreas is derived from the foregut. Ventral pancreatic bud becomes the pancreatic head, unicinate process (lower half of head), and main pancreatic duct. Dorsal pancreatic bud becomes the body, tail, isthmus, and accessory pancreatic duct.

Front 85

Annular pancreas

Back 85

ventral pancreatic bud abnormally encircles 2nd part of the duodenum- forming a rind of pancreatic tissue that may cause duodenal narrowing

Front 86

What is the spleen derived from?

Back 86

Spleen arises from the dorsal mesentery but is supplied by artery of foregut.

Front 87

Where are the distinctions between foregut/midgut/hindgut?

Back 87

Foregut- pharynx to duodenum
Midgut- duodenum to transverse colon
Hindgut- distal transverse colon to rectum

Front 88

Gastroschisis

Back 88

failure of lateral body folds to fuse
extrusion of abdominal contents through abdominal folds

Front 89

Omphalocele

Back 89

persistence of herniation of abdominal contents into umbilical cord

Front 90

The 4 stages of kidney development?

Back 90

1. Pronephros- week 4; then degenerates
2. Mesonephros - function as interim kidney for 1st trimester- later contributes to male genital system
3. Metanephos- permanent
4. Urogenital sinus- develops into bladder, urethra, and allantois

Front 91

Female genital development?

Back 91

Default development. Mesonephric duct disappears and paramesonephric duct develops

Front 92

Male genital development?

Back 92

SRY gene on Y chromosome codes for testis-determining factor. Mullerian inhibiting substance secreted by the testes suppresses development of paramesonephric ducts. Increase androgens - development of mesonephric ducts

Front 93

Mesonephric (Wolffian) Duct

Back 93

Develops into Male internal structures (except prostate) - Seminal vesicles, Epididymis, Ejaculatory duct, and Ductus deferens

Hint 93

SEED

Front 94

Paramesonephric (Mullerian) Duct

Back 94

Develops into fallopian tube, uterus, and part of the vagina.

Front 95

What does the genital tubercle become in males? females?

Back 95

Dihydrotestosterone- Glans penis
Estrogen- Glans clitoris

Front 96

What does the urogenital sinus become in males? females?

Back 96

Dihydrotestosterone- Corpus spongiosum, Bulbourethral glands, and prostate gland
Estrogen-Vestibular bulbs, Greater vestibular glands (Bartholin), Urethral and paraurethral glands (Skene)

Front 97

What does the urogenital folds becomes in males? females?

Back 97

Dihydrotestosterone- ventral shaft of penis (penile urethra)
Estrogen- Labia minora

Front 98

What does the Labioscrotal swellings become in males? females?

Back 98

Dihydrotestosterone- Scrotum
Estrogen- Labia Majora

Front 99

What are the 3 factors need to develop male gonads?

Back 99

1) Sry gene (TDF on the Y chromosome)
2) Testosterone - secreted by the Leydig cells
3) Mullerian- inhibiting factor - secreted by the Sertoli cells

Front 100

Where do the primordial germ cells arise from?

Back 100

The wall of the yolk sac

Front 101

What is the most common form of ectopic pregnancy?

Back 101

Ectopic tubal pregnancy
- the blastocyst implants within the ampulla of the uterine tube because of delayed transport
*Risk factors: endometriosis, PID, tubular pelvic surgery, or exposure to diethylstilbestrol

Front 102

Clinical signs of Ectopic tubal pregnancy?

Back 102

1)abnormal or brisk uterine bleeding
2) sudden onset of abdominal pain (can be confused with appendicitis)
3) last menses 60 days ago
4) + hCG
5) interperitoneal blood

Front 103

Most come site for ectopic abdominal pregnancy?

Back 103

rectouterine pouch (pouch of Douglas).

Front 104

Human Chorionic Gonadotropin

Back 104

hCG is a glycoprotein - produced by the syncytiotrophoblast
*stimulates the production of progesterone by the corpus lutem to maintain uterine lining

Front 105

What day can hCG be detected in the blood? the urine?

Back 105

Blood- Day 8
Urine- Day 10

Front 106

What can either low or high levels of hCG indicate?

Back 106

low levels- spontaneous abortion or ectopic pregnancy

high levels- multiple pregnancies, hydatidiform mole, or gestational trophoblastic neoplasia

Front 107

What is a hydatidiform mole?

Back 107

a blighted blastocyst (the embryo dies) followed by a hyperplastic proliferation of the trophoblast within the uterine wall

*clinical signs: preclampsia during the 1st trimester, high levels of hCG, and enlarged uterus with bleeding

* 5% of moles develop into gestational trophoblastic neoplasia

Front 108

What is gestational trophoblastic neoplasia?

Back 108

a maltignant tumor of the trophoblast that may occur after a normal pregnancy, abortion, or hydatidiform mole. High levels of hCG are clinical significant