Day 5.1 Embryo Flashcards Preview

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Flashcards in Day 5.1 Embryo Deck (191):
1

Sonic Hedgehog gene

Produced at BASE of limbs (limb buds) in ZPA- zone of polarizing activity
Involved in patterning along anterior-posterior axis
Mediated ECTOdermal fn.
Dysfn is related to holoprose encephalopathy (division along cerebral hemispheres)

2

Wnt-7 gene

Produced at APICAL ridge of ECTOderm- thickened ectoderm at DISTAL end of each developing limb.
Necessary for proper organization along dorsal-ventral axis

3

FGF gene

Produced at APICAL ridge of ECTOderm.
Stimulates mitosis of underlying MESOderm, providing for lengthening of limbs
Dysfn related to achondroplasia--> dwarfism

4

Homeobox (HOX) gene

Involved in segmental organization in a cranio-caudal direction.
Blueprint for skeletal morphology
Code for transcription regulators
Mutation in HOXD-13 = synpolydactyly- extra fused digit b/t 3rd and 4th fingers
Retinoic acid (VitA) is a teratogen that alters HOX gene expression and leads to mutation.

5

Day 0
Day 2
Day 3
Day 5
Day 6

Day 0 Fertilization by sperm
Day 2 zygote
Day 3 morula
Day 5 blastocyst
Day 6 implantation into endometrium

6

When does B-hCG secretion begin?

Within one week, after implantation of the blastocyst.
hCG is made by the placenta

7

2 weeks (fetus)

2's for 2nd week:
2 germlayers- Bilaminar disk (epiblast + hypoblast)
2 cavities- amniotic cavity and yolk sac
2 parts of placenta- cytotrophoblast and synctiotrohoblast

8

3 weeks (fetus)

Gastrulation - going from 2 layers to 3 layers
Primitive streak, notochord, and neural plate begin to form.

3 wks = 3 germ layers
ectoderm
mesoderm
endoderm

9

How is the primitive streak formed in week 3?

The epiblast (of the bilaminar disk from week 2) invaginates to form the primitive streak.

10

What the the cells from the primitive streak give rise to?

Cells from the primitive streak give rise to both the mesoderm and part of the ectoderm.

11

What does the notochord of week 3 do?

The notocord causes the neuroectoderm to form the neural plate.

12

When does the neural tube close?

By week 4
The neural tube is formed by the neuroectoderm, which forms the neural plate, which folds up in a U shape and forms the neural tube (and also the neural crest cells)
Note: any problems with the SC devt (eg spina bifida) will happen by the 4th week, since this is when the neural tube closes. Folic acid is important!

13

What is the embryonic period of the fetus?

Weeks 3-8
Neural tube closes (week 4)
Organogenesis
Extremely susceptible to tertatogens during this time- kidney, bladder, brain, heart are all forming.

14

Week 4

4's for week 4:
4 heart chambers (heart begins to beat)
4 limb buds begin to form
also the neural tube closes by week 4.

15

What is the fetal period of the fetus?

Starts in week 8, after the embryonic period is over. There is fetal mvmt, fetus looks more like a baby.

16

Week 10

Fetal genitalia have male/female characteristics

17

Alar plate and Basal plate

Alar plate = dorsal. Sensory.
Basal plate = ventral. Motor
Same as SC

18

What are the 3 (big categories of) things that the ectoderm gives rise to?

Surface ectoderm
Neuroectoderm
Neural crest cells

19

What does surface ectoderm form?

Adenohypophysis (Ant pit)- from Rathke's pouch
Lens of eye
Epithelial linings of oral cavity
Sensory organs of ear, retina, olfactory epithelium
Epidermis
Salivary, sweat, mammary glands

20

Craniopharyngioma

Benign Rathke's pouch tumor w cholesterol crystals and calcifications

21

What does the Rathke's pouch give rise to?

Ant. Pit (adenohypophysis)

22

What does the Neuroectoderm form?

Brain, Retina, SC
(think CNS and brain)
Brain structures:
neurohypophysis (post pit), CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland

23

What does the Neural crest form?

(think PNS and non-neural structures nearby)
ANS
Dorsal root ganglia
Cranial nerves
Celiac ganglion
Melanocytes
Chromaffin cells of adrenal medulla
Enterochromaffin cells
Parafollicular C cells of thyroid
Schwann cells
Pia and Arachnoid
Bones of skull
Odontoblasts
Laryngeal cartilage
Aorticopulm septum (spiral septum of heart)

24

Albanism can mean there was a problem of which component of ectoderm?

Neural crest cells- they are responsible for making melanocytes.

25

What is formed from endoderm?

Gut tube epithelium and derivatives:
lung, liver, pancreas, thymus, parathyroid, thyroid follicular cells

26

Mesoderm

Muscle
Bone
CT
Serous linings of body cavities- peritoneum
Spleen (from foregut mesentery)
CV structures
Lymphatics
Blood
Urogenital structures
Kidneys
Adrenal cortex

27

Embryologic derivative of the thyroid

Endoderm- thyroid develops from the tongue.

28

Embryologic derivative of the spleen

Mesoderm- spleen is derived from the foregut mesentery

29

Embryologic derivative of the adrenals

Adrenal medulla- neural crest (ectoderm)
Adrenal cortex- mesoderm

30

Embryologic derivative of the nucleus pulposis (of IVD)

Notochord (mesoderm)

31

Organ error: malformation

Intrinsic disruption
Occurs during embryonic period (3-8wks)

32

Organ error: deformation

Extrinsic disruption
Occurs after the embryonic period (after 8 wks)

33

Organ error: Agenesis

absent organ d/t absent primordial tsu

34

Organ error: Aplasia

absent organ even though primordial tsu was present

35

Organ error: Hypoplasia

Incomplete organ development
(obvs primordial tsu was present)

36

Mesodermal defects

VACTERL:
Vertebral defects
Anal atresia
Cardiac defects
Tracheo-Esophageal defects
Renal defects
Limb defects (bone and muscle)

37

When are fetuses most susceptible to teratogens

During the embryonic period (3-8 wks) when organogenesis is occuring.
Before week 3- all or none miscarriage (but no organs yet to be malformed)
After week 8- growth/devt problems (organs finished forming)

38

ACE inhibitors effect on fetus

Renal dmg
(ACE inhibitors are for HTN, renal dz)

39

Alcohol effect on fetus

FAS
Leading cause of birth defects and MR

40

Alkylating agents (chemo) effect on fetus

absence of digits
multiple anomalies

41

Aminglycosides effect on fetus

CN VIII toxicity- hearing problems

42

Diethylstilbestrol/DES effect on fetus
(synthestic estrogen)

Mullerian tract abnormalities- tube, uterine, cervical, vaginal abn in girls
Vaginal clear cell adenocarcinoma (rare)
this drug is not really used now

43

Folate antagonists (MTX-chemo)

Neural tube defects

44

Folic acid needed for prego

Need at least 1 mo of folic acid reserves before becoming pregnant.

45

Iodide (lack or excess) effect on fetus

Congential goiter
Hypothyroidism

46

Lithium effect on fetus

Ebstein's anomaly of the heart (atrialized R ventricle)

47

Maternal diabetes effect on fetus

Cardiac malformation- txposition of the great vessels
Big baby- shoulder dystocia--> clavical fracture or Erb-Duchenne palsy
Hypoglycemia in infant
Increased C-sections
Caudal regression syndrome (anal atresia to sirenomelia)

48

Smoking (nicotine, CO) effect on fetus

Nicotine is a vasoconstrictor, so sml babies
Preterm labor
Placental abruption
IUGR
ADHD

49

Tetracycline effect on fetus

Discolored teeth

50

Thalidomide (sedative) effect on fetus

Limb defects- phocomelia: flipper limbs

51

Valproate and carbamazpine (anti seizure meds) effect on fetus

Inhibition of intestinal folate absorption, so neural tube defects

52

Excess Vitamin A (Retinoic Acid) effect on fetus

Affects HOX gene
extremely high risk for spontaneous abortions and birth defects (cleft palate, cardiac abnormalities)
Make sure all women taking Vit A are on birth control

53

Warfarin/Coumadin

Bone deformities
Also fetal hemorrhage, abortion
Use heparin or lovanox instead

54

Fetal Alcohol Syndrome

Leading cause of congenital malformation in USA.
Pre and post-natal devt retardation
Microcephaly
Holoprosencephaly
Facial abn (Flat nose, smooth philtrum, low set ears, epicanthal folds)
Limb dislocation
Heart and lung fistulas
Mech may incl inhibition of cell migration.

55

Amniocentesis

15-17 weeks for genetic eval
eval lung maturity (lecithin:spingomyelin ratio >2.5)
eval defects in mom >35
eval abn maternal serum, quad screen (nuchal screen)
eval fetal blood type/hemolysis in RH-sensitized prego
1-2% maternal hemorrhage, 1/200 fetal loss (0.5%)

56

Chronic villous sampling

10-12 wks- so can know earlier than amnio)
1% fetal loss
1% can't dx NTD
get limb defects if done <9wks

57

Monochorionic monoamniotic twins

Share placenta and sac
Split in 8-12day range.
Know it's mono/mono if there is cord entanglement or if one yolk sac but 2 fetal poles (v early)

58

Monochorionic diamniotic twins

One placenta, but 2 sacs
split after day 3 (but before day 8)

59

Diachorionic diamniotic twins

Two placentas, Two sacs
Either monozygotic (identical twins) that split before day 3
Or dizygotic (fraternal, non-identical twins)- 2 eggs, 2 sperm

60

Twin-twin transfusion syndrome

Vascular channels are intertwined, results in one lg and one sml fetus
Lg one does worse due to sludging and polycythemia (increased RBCs)

61

When does the chorion form?

Day 3
So if split is before this, monozygotic (identical) twins will each have their own placenta (dichorionic, diamniotic)

62

When does the amnion form?

Day 8
If split occurs after this, monozygotic twins will be monochorionic monoamniotic.
Risk for conjoined goes up.

63

Fetal component of the placenta

Cytotrophoblast- inner layer of chorionic villi
Cyto makes Cells

Synctiotrophoblast- outer later of chorionic villi
Synctio Secretes hCG

64

Structure and fn of hCG

Structurally similar to LH, FSH, TSH

Stim's corpus lutem to secrete progesterone during 1st trimester

65

Maternal component of the placenta

Decidua basalis- derived from endometrium.
Maternal blood is in lacunae
In absence of decidua basalis, have placenta acreta (goes into uterine wall)

66

Umbilical cord contents

2 umbilical arteries (1 artery is assocd w congenital and chromosomal abn- esp renal abn)
1 umbilical vein
Urachus
Wharton's jelly

67

Where are umbilical arteries and veins derived from?

allantois

68

What blood is in umbilical arteries?

Deoxygenated blood.
the 2 arteries return deoxygenated blood from the fetal internal iliac arteries to the placenta

69

What blood is in umbilical vein?

Oxygenated blood
the 1 umbilical vein supplies oxygenated blood from the placenta to the fetus. goes into fetus through fetus's IVC

70

What is the urachus? How is it formed?

Uracus is a duct bt the fetal bladder and the yolk sac.
The yolk sac forms the allantois, which extends into the fetus's urogenital sinus.
The allantois becomes the urachus- duct bt bladder and yolk sac.

71

What happens if the urachus doesn't obliterate?

1. Patent urachus- urine discharge from umbilicus
2. Vesicourachal diverticulus- outpouching of the bladder

72

What is the vitelline duct? When is it obliterated?

aka omphalomesenteric duct
connects yolk sac to midgut lumen
Obliterated in week 7.

73

Vitelline fistula

Failure of vitelline duct to close --> meconium discharge from umbilicus
Ex: Meckel's diverticulus- partial closure, w patent portion attached to ileum. Can have ectopic gastric mucosa, causing melena (tarry, black) and RUQ pain.

74

Trunctus arteriosis gives rise to...

Ascending aorta and pulmonary trunk

75

Bulbus cordis gives rise to...

RV and smooth parts (outflow tract) of LV and RV

76

Primitive ventricle gives rise to...

Part of the LV

77

Primitive atria gives rise to...

Trabeculated LA and RA

78

Left horn of the sinus venosus gives rise to...

Coronary sinus

79

Right horn of the sinus venosus gives rise to...

Smooth part of RA

80

R common cardinal vein and R anterior cardinal vein give rise to...

SVC

81

What is the truncus arteriosus (TA)?

Neural crest cells migrate and give rise to the aorticopulmonary (spiral) septum of the heart.
Crest cells divide the trunk into 2 arteries via fusion and twisting of the truncal and bulbar ridges.
This gives rise to the ascending aorta and the pulmonary trunk.

82

Pathology of Truncus Arteriosus

Transposition of great vessels (failure to spiral)
Tetrology of Fallot (skewed AP septum devt)
Persistent TA (partial AP septum devt)

83

How is the interventricular septum formed?

1. Muscular septum forms, with interventricular foramen abv it
2. AP septum meets and fuses with the muscular ventricular septum, closing the interventricular foramen
3. Growth of endocardial cushings separates the atria from the ventricles, and contributes to both atrial separation and the membranous portion of the intervertebral septum

84

Pathology of the interventricular septum

Membranous septal defect (the part that joins the AP and the interventricular) causes initial Left --> Right shunting, which then becomes Right --> Left shunting. This is called the Eisenmenger Complex.

85

How is the interatrial septum formed?

p124

86

Pathology of interatrial septum formation?

Patent foramen ovale (R --> L shunt)
Cuased by excessive resorption of the septum prium and/or septum secundum

87

Where does fetal erythropoesis (making RBCs) occur?

Young Liver Synthesizes Blood:
Yolk sac (3-8wk, embryonic period)
Liver (6-30wk)
Spleen (9-28wk)
Bone marrow (28wk onward)- in flat bones (sternum, pelvis, ribs, cranial bones, vertebrae; in <25yo also in long bones of leg)

88

Fetal Hb vs Maternal Hb structure

Hb is made of 4 chains.
Fetal = alpha2 gamma2
Maternal/adult = alpha2 beta2

gamma (fetal) chains have a lower affinity for 2,3-DPG, so they have a higher affinity for O2

beta chains (adult) have a higher affinity for 2,3-DPG, so they will give up their O2 to fetal Hb

89

Path of fetal circ

placenta --> umb veins --> ductus venosus in liver --> IVC (so bypasses liver circulation)

IVC --> (+ a little deoxygenated blood from SVC) --> RA --> 2options: most goes through patent FO to LA, LA --> aorta --> brain, body

a little goes RA --> RV --> Pulm artery --> Ductus arteriosis (branch to descending aorta) --> body. (the blood from the SVC does this)

(the little blood that didn't go through the PDA goes to the lungs (but no gas exchg))

from lower body, goes into internal iliac arteries --> umbilical arteries --> placenta

90

Why does the FO close at birth?

Infant takes a breath, diaphragm goes down, decreased resistance in pulm vasculature causes increased left atrial prs, so FO closes (now called fossa ovalis)

91

Why does ductus arteriosis close shortly after birth?

Increased O2 leads to decreased prostaglandins.
Prostaglandins are what keeps the PDA open- if you take them away (bc of O2), the PDA will close.

92

How to close/open a PDA

Indomethicin helps close PDA
If you want to keep it open, use prostaglandins.

93

Umbilical vein becomes...

ligamentum teres hepatis (in the falciform ligament of the liver)

94

UmbiLical arteries become...

mediaL umbilical ligaments

95

AllaNtois becomes...

urachus --> mediaN umbilical ligament
the urachus is the part of the allanotic duct bt the bladder and the umbilicus. Urachal cyst or sinus is a remnant.

96

Ductus arteriosus becomes...

ligamentum arteriosum

97

Ductus venosus becomes...

ligamentum venosum

98

Formen ovale becomes...

Fossa ovalis

99

Notochord becomes...

nucleus pulpous of the IVD

100

1st aortic arch becomes...

part of maxillary artery (branch of ext carotid)
1st arch is MAXimal

101

2nd aortic arch becomes...

Stapedial artery and hyoid artery
Second = Stapedial

102

3rd aortic arch becomes...

Common Carotid artery, and proximal part of the internal carotid artery
C for carotid is the 3rd letter of the alphabet (3rd arch)

103

4th aortic arch becomes...

left side: aortic arch
right side: proximal part of right subclavian artery
4th arch - 4 limbs - systemic

104

6th aortic arch becomes...

Proximal part of pulmonary arteries and (on left side only)- ductus arteriosus
6th - pulm and pulm-to-systemic shunt (DA)

105

List the right-to-left shunts

R-to-L are early cyanosis (blue babies)
The 5 T's:
Tetrology of Fallot
Transposition of great vessels
Truncus arteriosus
Tricuspid atresia
TAPVR- total anomalous pulmonary venous return

106

List the left-to-right shunts

L-to-R are late cyanosis (blue kids)
VSD
ASD
PDA

107

Tetrology of Fallot

4 things:
1. Pulmonary stenosis (RV outflow obstruction- most imp factor determining pgx)
2. RVH (so boot-shaped heart)
3. Overriding aorta (overrides VSD)
4. VSD

Early cyanosis is caused by R->L shunt across the VSD. R->L shunt exists bc of the increased prs caused by the stenotic pulmonic valve.
Pts suffer from cyanotic spells
ToF is caused by anterosuperior displacement of the infundibular septum

108

Why do ToF pts squat?

Compression of femoral arteries causes increased resistance (incrsd TPR) on the left side, so the R->L shunting will be decreased, and more blood from the RV will go into the lungs as it should.
Compression --> increased resistance --> increased prs

109

What is transposition of the great vessels?

Aorta leaves the RV (anterior)
Pulm trunk leaves the LV (posterior)
So there is separation of systemic and pulmonary circulations (there are 2 separate circular systems)
Not compatible w life unless a shunt (right-to-left) is present to allow adequate mixing of oxygenated blood (VSD, PDA, Patent FO)
D/t failure of the aorticopulmonary septum to spiral.
w/o surgical correction, die in first few months of life.

110

What is Truncus Ateriosus?

aka persistent TA
failure of truncus arteriosus to divide into pulm trunk and aorta
get R->L shunt

111

What is Tricuspid atresia?

Absence of tricuspid valve (bt RA and RV) and hypoplastic RV.
Requires both ASD and VSD for viability
Right to left shunt.

112

What is TAPVR?

total anomalous pulmonary venous return
pulmonary veins drain into right heart circulation (SVC, coronary sinus)

113

Which left-to-right shunt is most common?

VSD.
VSD > ASD > PDA

114

VSD

L->R shunt, late cyanosis (blue kids)
most common congenital cardiac anomaly
40% close by the first 6mo

115

ASD heart sounds

L-->R shunt, late cyanosis (blue kids)
loud S1
wide, fixed split S2

116

PDA closure

L-->R shunt, late cyanosis (blue kids)
close with indomethacin
but most close by themselves in first 24 hrs

117

Pulmonary problems in VSD, ASD, PDA

increased pulm resistance due to arteriolar thickening.
leads to progressive pulm HTN, R-->L shunt (Eisenmenger's)

118

What is Eisenmenger's Syndrome?

Uncorrected VSD, ASD, or PDA causes compensatory vascular hypertrophy, resulting in progressive pulm HTN

As pulm resistance increases, the L --> R shunt reverses to a R-->L shunt, which causes late cyanosis (clubbing and polycythemia)

119

Coarctation of the aorta

2 types:
Infantile type- aortic stenosis proximal to insertion of ductus arteriosus (preductal)
Assoc w Turner's Syndrome XO
INfantile is IN close to the heart
Adult type- stenosis is distal to DA (post ductal). assoc w notching of ribs d/t collateral circulation, HTN in upper extremities, weak pulse/hypotension in lower extremeties
aDult: Distal to Ductus
Check femoral pulses of phys exam
Can result in aotic regurg
Most commonly assoc w bicuspid aortic valve

120

PDA

in fetal period, shunt is R --> L (normal)
in neonatal period, lung resistance decreases, so shunt becomes L-->R, w subsequent RVH and failure (abn).
Continuous machinery murmur
Patency maintained by PGE2 and low O2 tension.
Uncorrected PDA can result in late cyanosis in lower extremities

121

Indomethicin, Prostaglandins, PDA

Indomethicin- closes PDA
ENDomethicin ENDs PDA (closes it)

Prostaglandins (PGE) keep it open
PGEE KEEps it open- may be nec to sustain life in conditions like txposition of great vessels

PDA is normal in utero, closes after birth

122

Cardiac defect w 22q11 syndromes

e.g. Digeorge
Defect in truncus arteriosus, ToF

123

Cardiac defect in Down Synd

ASD, VSD, AV septal defect (endocardial cushion defect)

124

Cardiac defect in congenital rubella

Septal defects, PDA, pulm artery stenosis

125

Cardiac defect in Turner's Syndrome

XO
coarctation of the aorta (infantile/preductal type)

126

Cardiac defect in Marfan's syndrome

Aortic insufficiency (late complication), dissection of the aorta

127

Cardiac defect in infant of diabetic mom

Transposition of great vessels

128

Path of blood through PDA

PATENT DA = L -->R
Blood goes from aorta to pulmonic.
(This is backwards from DA in fetus)

129

What are the parts of the brain in Week 4

Prosencephalon
Mesencephalon
Rhombencephalon

130

What does the prosencephalon turn into in week 5?

Telencephalon and Diencephalon

131

What does the mesencephalon turn into in week 5?

Stays as Mesencephalon

132

What does the Rhombencephalon turn into in week 5?

Metencephalon and Myelencephalon

133

What are the adult dervatives of the telencephalon?

Walls: cerebral hemispheres (+basal ganglia, hippocampus, amygdala)
Cavities: Lateral ventricles

134

What are the adult derivatives of the Diencephalon?

Walls: thalami, hypothalamus, optic nerves and tracts
Cavities: 3rd ventricle

135

What are the adult derivatives of the mesencephalon?

Walls: Midbrain
Cavities: part of aqueduct

136

What are the adult derivatives of the metencephalon?

Walls: Pons and Cerebellum
Cavities: part of aqueduct (pons); part of 4th ventricle (cerebellum)

137

What are the adult derivatives of the myelencephalon?

Walls: medulla
Cavities: part of 4th ventricle

138

Folic acid vitamins

Normal multivitamin has 0.4 mg
Prenatal has 0.8-1mg
Prenatal for high risk has 4mg

139

Neural tube defect

Neuropores fail to fuse at 4th week, so connection bt amniotic cavity and spinal canal stays open.
Assoc w low folic acid intake
See elevated alpha-fetoprotein (AFP) in amniotic fluid and in maternal serum.
See elevated AFP and AChE in CSF (these are both made in the neural canal)
Can have spina bifida occulta
Meningocele
Myelomeningocele
These usu present in lower part of spine

140

Spina bifida occulta

Failure of bony spinal canal to close, but no structural herniation
Dura is intact.
Usually seen at lower vertebral levels, often have tuft of hair at the level.

141

Meningiocele

Bony spinal canal defect w meninges herniating through (dura not intact)
But SC itself is still in the right place and didn't herniate through

142

Myelomeningocele

Defect in bony spinal canal with both meninges and SC herniating through.

143

What does increased maternal AFP mean?

neural tube defects
anterior abd wall defects

144

Anencephaly

Anterior end of neural tube is malformed
No brain/calvarium- not bc it didn't develop, but bc the amniotic fluid is acidic (d/t urine) and eats away at it.
No swallowing center in brain--> fetus pees but doesn't drink, so get polyhydramnios (too much amn fluid)
See elevated AFP

145

Holoprosencephaly

Decreased separation of hemispheres across the midline
D/t problem w Sonic Hedgehog gene
See cyclopia and cleft lip/palate
Assoc w Patau's Trisomy 13 and severe FAS

146

Syringomyelia

Enlarged central canal of SC, causing nerve compression
Crossing fibers of spinothalamic tract are usu dmgd first.
Cape-like bilateral loss of P/T sensation in upper extremities (but touch sensation is okay)
Severe cases- weakness and atrophy of hand muscles
Most common at C8-T1
Often in pts w Arnold-Chiari II malformation

147

Arnold-Chiari Type II

Tonsil of cerebellum herniates through the foramen magnum, causing aqueductal stenosis (blockage) and hydrocephaly (water on brain)
Often presents w syringomyelia (enlgd central canal of SC) and with throacolumbar myelomeningocele (both meninges and SC herniate out of spinal canal)

148

Dandy-Walker

Large posterior fossa, no cerebellar vermis (absent), and cystic enlgmt of 4th ventricle
Can lead to hydrocephalus and spina bifida

149

Brachial clefts

On the outside.
Derived from ectoderm
aka brachial grooves

150

Brachial arches

On the outside.
Derived from mesoderm (muscles, arteries) and neural crests (bones, cartilage)

151

Brachial pouches

On the inside.
Derived from endoderm
Kangaroo pouch is on the inside.

152

Ecto/meso/endoderm are assoc'd w which brachial apparatuses?

CAP covers from outside to inside:
Cleft = ectoderm
Arch = mesoderm
Pouch = endoderm (INdo is INside- kangaroo)

153

Brachial Arch 1 innervation

CN V2 and V3
5 trigeminal
Note: all arch innervation is by nerves that are both sensory and motor only except V2, which only carries sensory info.

154

Arch 2 innervation

CN VII
7 facial

155

Arch 3 innervation

CN IX
9 glossopharyngeal

156

Arch 4 innervation

CN X
10 vagus

157

Arch 6 innervation

CN X
10 vagus

158

Actions of arches (and their nerves)

1- chewing (V2, V3)
2- facial expression (VII)
3- Styolpharyngeus (IX)
4- swallowing (X)
6- speaking (X)

1 man sat chewing
2 hands on his face
the 3rd with his pharynx
swallowed the 4th plate
speak up, speak up said the 6th in return
your cricothyroid
makes me want to burn

159

Brachial arch (mesoderm) derivatives: Arch 1
Cartilage/Musc/Nerves/Arteries

Ms, Ts
Cartilage:
Meckel's cartilage, Mandible, Malleus, incus, sphenoMandibular ligament

Muscles:
Muscles of Mastication (teMporalis, Masseter, lateral and Medial pterygoids); Mylohyoid, anterior belly of digastric, Tensor Tympani, Tensor veli palatini, anTerior Two-Thirds of Tongue

Nerves:
CN V2, V3

Arteries:
Maxillary artery (branch of ext carotid)

160

Brachial arch (mesoderm) derivatives: Arch 2
Cartilage/Musc/Nerves/Arteries

S's

Cartilage:
Reichert's cartilage,
Stapes,
Styloid proceSS,
LeSSer horn of hyoid
Stylohyoid ligament

Musc:
muscles of facial expression, Stapedius, Stylohyoid, poSterior belly of digastric

Nerves: CN VII

Arteries
Stapedial artery, hyoid artery

161

Brachial arch (mesoderm) derivatives: Arch 3
Cartilage/Musc/Nerves/Arteries

3 = pharyngeal

Cartilage: greater horn of hyoid

Muscle:
Stylopharyngeus (think of stylopharyngeus innervated by glossopharygeal nerve)

Nerve: IX

162

Brachial arch (mesoderm) derivatives: Arch 4-6
Cartilage/Musc/Nerves/Arteries

4-6 = neck, voice box

Cartilage:
thyroid, cricoid, arytenoid, corniculate, cuneiform

Muscles:
4th arch- most pharyngeal constrictors, cricothyroid, levator palatini
6th arch- all intrinsic musc of larynx except the cricothyroid (that's 4th)

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

163

Treacher-Collins syndrome

1st arch neural crest fails to migrate- get mandibular hypoplasia, facial abn

164

Congenital pharyngocutaneous fistula

Persistence of cleft and pouch, causes fistula bt tonsillar area and cleft in lateral neck (lateral cleft does NOT move when you swallow)

165

Arch 5

No mjr developmental contributions

166

Which arch forms posterior 1/3 of tongue?

Arches 3 and 4

167

Brachial cleft (ectoderm) derivatives: 1st cleft

External auditory meatus

168

Brachial cleft (ectoderm) derivatives: 2nd, 3rd, 4th clefts

Form temporary cervical sinuses, which are obliterated by proliferation of 2nd arch mesenchyme

169

Persistent cervical sinus

Leads to brachial cleft cyst within lateral neck
Lateral, and does NOT move with swallowing

170

Brachial pouch (endoderm) derivatives: 1st pouch

Middle ear cavity
Eustacian tube
Mastoid air cells
(contributes to endoderm-lined structures of the ear)

171

Brachial pouch (endoderm) derivatives: 2nd pouch

Epithelial lining of palatine tonsil

172

Brachial pouch (endoderm) derivatives: 3rd pouch

Dorsal wings develop into inferior parathyroids
Ventral wings develop into thymus
3rd pouch contributes to 3 structures: thymus, left and right inf parathyroids
3rd pouch structures end up below 4th pouch structures

173

Brachial pouch (endoderm) derivatives: 4th pouch

Dorsal wings develop into superior parathyroids- 4th ends up higher than 3rd

174

Aberrant development of 3rd and 4th pouches

DiGeorge syndrome (22q11 deletion)- leads to Tcell deficiency d/t thymic aplasia and hypocalcemia d/t no parathyroid devt.

175

MEN 2A

Mutation of germline RET gene (neural crest cell abn)
Affects 3 things:
Adrenal medulla (pheochromocytoma)
Parathyroid (tumor) - 3rd/4th pharyngeal pouch
Parafollicular C cells (medullary thyroid cancer)- neural crest cells

176

Tongue devt

1st brachial arch forms ant. 2/3 (so sensation- V3, taste- CN VII)
3rd and 4th arches form post. 1/3 (so sensation and taste- mainly CN IX, extreme posterior is CN X)
Motor innervation of all tongue is CN XII
Muscles of the tongue come from occipital myotomes

177

CN of the tongue

Taste: CN VII, IX, X (solitary)
Pain(sensation): CN V3, IX, X
Motor: CM XII

Taste: ant 2/3 by CN 7, post 1/3 by 9/10
Pain: ant 2/3 by V3, post 1/3 by 9/10
Motor: all by 12

178

Ear devt: 1st arch

1st arch - M's and T's
Malleus/incus bones
Tensor Tympani (V3)

179

Ear devt: 2nd arch

2nd arch - S's
Stapes bone
Stapedius (VII)

180

Ear devt: 1st cleft

External auditory meatus

181

Ear devt: 1st brachial membrane

Tympanic mbr

182

Ear devt: 1st pouch

Eustacian tube, middle ear cavity, mastoid air cells

183

Brachial cleft cyst vs Thyroglossal duct cyst

Brachial cleft cyst - lateral, does NOT mv w swallowing
Thyroglossal duct cyst - midline, DOES mv w swallowing

184

Thyroid devt

Thyroid diverticulum comes from floor of primitive pharynx, descends into neck.
Connected to tongue by thyroglossal duct- normally disappears, but can persist as benign pyramidal lobe of thyroid.
Foramen cecum is normal remnant of thyroglossal duct.
Most common ectopic thyroid tsu site is tongue

185

Thyroglossal duct cyst

In midline neck, DOES mv w swallowing.
Benign, but usu remove d/t high infection rate

186

Cleft lip

failure of fusion of maxillary and medial nasal processes (formation of primary palate)
Cosmetic, doesn't affect fn

187

Cleft palate

failure of fusion of lateral palatine processes, nasal septum, and/or the median palatine process (formation of secondary palate)
cleft palate interferes w fn- can't suckle

188

Cause of cleft lip, cleft palate

Many things!
Can be folic acid def, genetic, teratogens, any combo of these or other things.

189

Diaphragm is derived from...

SPBD (several parts build diaphragm):
Septum transversum --> central tendon
Pleuroperitoneal folds
Body wall
Dorsal mesentery of esophagus --> crura

190

Innervation of diaphragm

C3,4,5
Diaphragm descends during devt but keeps innervation from above

191

Diaphragmatic hernia

Abd contents can herniate into thorax bc of incomplete diaphragm devt and lead to hypoplasia of thoracic organs (eg no lungs), space compression (eg compressed heart), scaphoid abd, and cyanosis.