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Human Reproduction > First Aid: Reproductive Embryology > Flashcards

First Aid: Reproductive Embryology Flashcards

1
Q

List of important genes of embryogenesis

A
  • Sonic Hedgehog gene
  • WNT-7 gene
  • Fibroblast growth factor (FGF) gene
  • Homeobox (Hox) genes
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2
Q

Description of the Sonic Hedgehog gene

A
  • Produced at the base of limbs in zone of polarizing activity
  • Involved in patterning along anteroposterior axis and CNS development
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3
Q

Where is Sonic Hedgehog produced?

A

Produced at the base of limbs in the Zone of Polarizing Actibity (ZPA)

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4
Q

What is the function of Sonic Hedgehog gene

A

Involved in patterning along the anteroposterior axis and CNS development

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5
Q

What happens with a mutation in Sonic Hedgehog

A

Mutation can cause holoprosencephaly

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6
Q

What is WNT-7 gene

A
  • Produced at the apical ectodermal ridge (thickened ectoderm at distal end of each developing limb).
  • Necessary for proper organization along the dorsal-ventral axis
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7
Q

Where is Wnt-7 produced?

A

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

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8
Q

What is the function of Wnt-7?

A

Necessary for proper organization along the dorsal-ventral axis

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9
Q

FGF AKA

A

Fibroblast Growth Factor

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10
Q

Description of FGF

A
  • Produced at apical ectodermal ridge
  • Stimulates mitosis of underlying mesoderm, providing for the legnthening of limbs
  • “Look at that Fetus, Growing Fingers”
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11
Q

FGF is produced where?

A

Produced at the apical ectodermal ridge

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12
Q

FGF function

A

Stimulates mitosis of underlying mesoderm, providing for the lengthening of limbs

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13
Q

FGF Nmemonic

A

“Look at that Fetus, Growing Fingers”

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14
Q

Description of Homeobox (Hox) genes

A
  • Involved in segmental organization of embryo in a craniocaudal direction
  • Code for transcription factors
  • Hox mutations result in -> appendages in the wrong locations
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15
Q

Hox genes AKA

A

Homeobox genes

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16
Q

Hox genes gunction

A
  • Involved in segmental organization of embryo in craniocaudal direction
  • Code for transcription factors
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17
Q

Hox gene mutations result in

A

Appendages in wrong locations

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18
Q

Describe early embryonic development

A
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19
Q

Describe Early fetal development within the first week

A
  • hCG secretion begins around the time of implantation of blastocyst
  • Blastocyst“sticks” at day 6
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20
Q

Describe Early fetal development within week 2

A
  • Bilaminar disc (epiblast, hypoblast)
  • 2 weeks = 2 layers
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21
Q

Describe Early fetal development within week 3

A
  • Gastrulation forms trilaminar embryonic disc
  • Cells from epiblast invaginate -> primitive streak -> endoderm, mesoderm, ectoderm
  • Notochord arises from midline mesoderm; overlying ectoderm becomes neural plate
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22
Q

Describe Early fetal development weeks 3-8 (embryonic period)

A
  • Neural tube formed by neuroectoderm and closes by week 4
  • Organogenesis
  • During this time embryo is extremely susceptible to teratogens
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23
Q

Describe Early fetal development week 4

A
  • Heart begins to beat
  • Upper and lower limb buds begin to form
  • 4 weeks = 4 limbs and 4 heart chambers
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24
Q

When does the heart begin to beat?

A

4 weeks

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25
Q

When do the upper and lower limb buds begin to form?

A

4 weeks

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26
Q

Describe Early fetal development week 6

A

Fetal cardiac activity visible by transvaginal ultrasound

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27
Q

Describe Early fetal development week 8

A
  • Fetal movements start
  • Gait at week 8
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28
Q

Describe Early fetal development week 10

A
  • Genitalia have male/female characteristics
  • week 10 = Tenitalia (genitalia)
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29
Q

When do genitalia have male/female characteristics?

A

Week 10

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30
Q

What are the main embryonic derivatives?

A
  • Ectoderm
  • Mesoderm
  • Endoderm
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31
Q

Components of ectoderm

A
  • Surface ectoderm
  • Neural tube
  • Neural crest
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32
Q
A
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33
Q

Surface ectoderm derivatives

10 listed

A
  • Epidermis
  • Adenohypophysis AKA anterior pituitary (from Rathke pouch)
  • Lens of eye
  • Epithelial linings of oral cavity
  • Sensory organs of the ear
  • Olfactory epithelium
  • Anal canal below below the pectinate line
  • Parotid glands
  • Sweat glands
  • Mammary glands
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34
Q

Issues with surface ectoderm

A

Craniopharyngioma - benign Rathke pouch tumor with cholesterol crystals, calcifications

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35
Q

Neural tube derivatives

A

Neuroectoderm (think CNS)

  • Brain
    • Neurohypophysis
    • CNS neurons
    • Oligodendrocytes
    • Astrocytes
    • Ependymal cells
    • pineal glands
  • retina
  • Spinal cord
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36
Q

Craniopharyngioma embronic origin

A

Surface ectoderm

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37
Q

What is Craniopharyngioma?

A

Benign Rathke pouch tumor with cholesterol crystals and calcifications

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38
Q

Neural crest derivatives

A
  • Melanocytes
  • Myenteric (Auerbach) plexus
  • Odontoblasts
  • Endocardial cushions
  • Laryngeal cartilage
  • Parafollicular (C) cells of the thyroid
  • PNS (dorsal root ganglia, cranial nerves, autonomic ganglia)
  • Adrenal medulla and all ganglia
  • Spiral membrane (aorticopulmonary septum)
  • Schwann cells
  • Pia and arachnoid
  • bones of skull

MMOtEL PPASS

Neural crest - think PNS and Non-neural structures nearby

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39
Q

Mesoderm derivatives

A
  • Muscle
  • Bone
  • Connective tissue
  • serous linings of body cavities (eg peritoneum, pericardium, pleura)
  • Spleen (derived from foregut mesentary)
  • cardiovascular structures
  • lymphatics
  • blood
  • wall of gut tube
  • upper vagina
  • kidneys
  • adrenal cortex
  • dermis
  • testis
  • ovaries
  • Notochord induces ectoderm to form neuroectoderm (neural plate); its only postnatal derivative is the nuclues pulposus of the intervertebral disc
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40
Q

Mesoderm derivatives Nmemonic

A

Middle/”meat” layer

Mesodermal defects = VACTERL

  • Vertebral defects
  • Anal atresia
  • Cardiac defects
  • Tracheo-Esophageal fistula
  • Renal defects
  • Limb defects (bone and muscle)
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41
Q

Endoderm derivatives

A
  • Gut tube epithelium (including anal canal above the pectinate line)
  • Most of the urethra and lower vagina (Derived from urogenital sinus)
  • Luminal epithelial derivatives (eg lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, thyroid follicular cells)

Endoderm = “Enternal” layer

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42
Q

What are the types of errors in morphogenesis?

7 listed

A
  • Agenesis
  • Aplasia
  • Hypoplasia
  • Disruption
  • Deformation
  • Malformation
  • Sequence
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43
Q

What is agenesis

A

Type of error in morphogenesis where:

Absent organ due to absent primordial tissue

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44
Q

What is aplasia?

A

Type of error in morphogenesis:

Absent organ despite presence of primordial tissue

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45
Q

What is hypoplasia?

A

Type of error in morphogenesis:

Incomplete organ development where the primordial tissue is present

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46
Q

What is Disruption?

A

Type of error in morphogenesis:

2o breakdown of previously normal tissue or structure (eg amniotic band syndrome)

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47
Q

What is Deformation?

A

Type of error in morphogenesis:

Extrinsic disruption; occurs after the embryonic period (weeks 3-8)

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48
Q

When is the embryonic period?

A

weeks 3-8

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49
Q

What is malformation?

A

Type of error in morphogenesis:

Intrinsic disruption; occurs during the embryonic period (weeks 3-8)

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50
Q

What is sequence?

A

Type of error in morphogenesis:

Abnormalities result from a single 1o embryolodic event (eg oligohydramnios -> Potter sequence)

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51
Q

Example of Disruption error in morphogenesis

A

Amniotic Band Syndrome

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52
Q

Example of Sequence error in morphogenesis

A

Oligohydramnios -> Potter sequence

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53
Q

When is the embryo most susceptible to teratogens?

A

Most susceptible 3-8 weeks (embryonic period - organogenesis)

Before week 3, “all-or-none” effects

After week 8, growth and function affected

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54
Q

Teratogen sensitivity before 3 weeks

A

Before week 3, “all-or-none” effects

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55
Q

Teratogen sensitivity after 8 weeks

A

After week 8, growth and function affected

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56
Q

Examples of classes of medications that are teratogenic

A
  • ACE Inhibitors
  • Alkylating agents
  • Aminoglycosides
  • Antiepileptic drugs
  • Diethylstilbestrol
  • Folate antagonists
  • Isotretinoin
  • Lithium
  • Methimazole
  • Tetracyclines
  • Thalidomide
  • Warfarin
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57
Q

Examples of substances that can be teratogenic in the setting of substance abuse

A
  • Alcohol
  • Cocaine
  • Smoking (nicotine, CO)
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58
Q

Other teratogenic exposures

5 listed

A
  • Iodine (lack or excess)
  • Maternal diabetes
  • Methylmercury
  • Vitamin A excess
  • X-rays
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59
Q

Ace inhibitors effects on fetus

A

Renal damage

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60
Q

Alkylating agents effects on fetus

A
  • Absence of digits
  • multiple anomalies
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61
Q

Aminoglycosides effects on fetus

A

Ototoxicity

Aminoglycosides = A mean guy hit the baby in the ear

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62
Q

Antiepileptic drugs effects on fetus

A
  • Neural tube defects
  • Cardiac defects
  • cleft palate
  • skeletal abnormalities (eg, phalanx/nail hypoplasia, facial dysmorphism)

High dose folate supplementation is recommended

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63
Q

Which antiepileptic drugs are most teratogenic?

A

Most commonly

  • Valproate
  • Carbamazapine
  • Phenytoin
  • Phenobarbital
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64
Q

Diethylstilbestrol effects on fetus

A
  • Vaginal clear cell adenocarcinoma
  • Congenital Müllerian anomalies
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65
Q

Folate antagonists effects on fetus

A
  • Neural tube defects
  • Includes Trimethoprim, methotrexate, antiepileptic drugs
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66
Q

Isotretinoin effects on fetus

A
  • Multiple severe birth defects
  • Contraception MANDATORY
  • IsoTERATinoin
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67
Q

Lithium effects on fetus

A

Ebstein anomaly (apical displacement of the tricuspid valve)

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68
Q

What drug causes Ebstein anomaly

A

Lithium

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69
Q

What is Ebstein Anomaly?

A

Ebstein anomaly = apical displacement of tricuspid valve

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70
Q

Methimazole effects on fetus

A

Aplasia cutis congenita

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71
Q

Tetracyclines effects on fetus

A
  • Discolored teeth
  • Inhibited bone growth (teeth?)

Tetracyclines = “TEETHracyclines”

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72
Q

Thalidomide effects on fetus

A
  • Limb defects (phocomelia, micromelia -“flipper” limbs)

Limb defects with “ tha-limb-domide”

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73
Q

Warfarin effects on fetus

A
  • Bone deformities
  • fetal hemorrhage
  • abortion
  • Ophthalmologic abnormalities

Do not wage Warfare on the baby; keep it heppy with heparin (does not cross the placenta)

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74
Q

Alcohol effects on fetus

A
  • Common cause of birth defects and intellectual disability
  • Fetal alcohol syndrome
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75
Q

Cocaine effects on fetus

A
  • Low birth weight
  • preterm birth
  • IUGR
  • placental abruption

Cocaine -> vasoconstriction

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76
Q

Smoking (nicotine and CO) effects on fetus

A
  • Low birth weight (leading cause in developed countries)
  • Preterm labor
  • Placental problems
  • IUGR
  • SIDS
  • ADHD

Nicotine -> vasoconstriction

CO -> impaired O2 delivery

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77
Q

What is the leading cause of low-brith-weight in developed countries?

A

Smoking

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78
Q

Iodine effects on fetus

A

Either from excess or lack of)

Congenital goiter (Excess)

hypothyroidism (Cretinism) (Lack)

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79
Q

Maternal Diabetes effects on fetus

A
  • Caudal regression syndrome (anal atresia to sirenomelia)
  • Congenital heart defects (eg VSD, transposition of the great vessels)
  • Neural tube defects
  • Macrosomia
  • Neonatal hypoglycemia
  • Polycythemia
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80
Q

Methylmercury effects on fetus

A
  • Neurotoxicity

Highest in

  • Swordfish
  • Shark
  • Tilefish
  • King mackerel
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81
Q

Vitamin A excess effects on fetus

A

Extremely high risk for spontaneous abortions and birth defects (cleft palate, cardiac)

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82
Q

X-rays effects on fetus

A
  • Microcephaly
  • Intellectual disability

Minimized by lead shielding

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83
Q

What is Fetal Alcohol Syndrome?

A

Newborns of alcohol-consuming mothers have ↑ incidence of congenital abnormalities, including pre- and postnatal

  • developmental retardation
  • microcephaly
  • facial abnormalities (eg. smooth philtrum, thin-vermillion border [upper lip], small palpebral fissures)
  • Limb dislocation
  • Heart defects
  • Heart and lung fistulas and holoprosencephaly in its most severe form of FAS
84
Q

What is the leading cause of intellectual disability in the US

A

Fetal Alcohol Syndrome

85
Q

Clinical manifestations of the most severe form of FAS

A
  • Heart-lung fistulas
  • Holoprosencephaly
86
Q

FAS AKA

A

Fetal Alcohol Syndrome

87
Q

FAS pathophysiology

A

Mechanism is failure of cell migration

88
Q

NAS AKA

A

neonatal abstinence syndrome

89
Q

What is neonatal abstinence syndrome?

A

A complex disorder involving CNS, ANS and GI systems which is 2o to maternal opiate use/abuse.

90
Q

Risk factors of NAS

A
  • Maternal substance abuse during pregnancy
  • poor mental health
  • poor prenatal care
  • low SES
  • Lack of family support
  • HCV
91
Q

NAS prophylaxis

A

Universal screening for substance abuse is recommended in all pregnant patients

92
Q

NAS clinical manifestations

A

Newborns may present with:

  • Uncoordinated sucking reflexes
  • irritability
  • high-pitched crying
  • tremors
  • tachypnea
  • sneezing
  • diarrhea
  • possibly seizures
93
Q

Possible mechanisms of twinning

A
  • Dizygotic (“fraternal”)
  • Monozygotic (“identical”)
94
Q

Fraternal Twins AKA

A

Dizygotic twins

95
Q

Identical twins AKA

A

Monozygotic twins

96
Q

Monozygotic twins AKA

A

Identical twins

97
Q

Dizygotic twins AKA

A

Fraternal twins

98
Q

Explain Dizygotic twins

A

Fraternal twins arise from 2 eggs that are separately fertilized by 2 different sperm (always 2 zygotes) and will have 2 separate amniotic sacs and 2 separate placentas (chorions)

99
Q

Explain Monozygotic twins

A
  • Identical twins arise from 1 fertilized egg (1 egg + 1 sperm) that splits in early pregnancy
  • The timing of cleavage determines chorionicity (number of chorions) and amniocity (number of amnions) (SCAB)
100
Q

How to determine the number of chorions in Monozygotic twins

A

SCAB

Separate chorion and amnion = Cleavage in 0-4 days

Shared Chorion = Cleavage in 4-8 days

Shared Amnion = Cleavage in 8-12 days

Shared Body (conjoined) = Cleavage in 13+ days

101
Q

SCAB

A

SCAB

Separate chorion and amnion = Cleavage in 0-4 days

Shared Chorion = Cleavage in 4-8 days

Shared Amnion = Cleavage in 8-12 days

Shared Body (conjoined) = Cleavage in 13+ days

102
Q

What is the Placenta?

A

1o site of nutrient and gas exchange between mother and fetus

103
Q

Components of the placenta

A
  • Fetal component
  • Maternal component
104
Q

Fetal component of the placenta

A
  • Cytotrophoblast
  • Syncytiotrophoblast
105
Q

Maternal component of the placenta

A

Decidua basalis

106
Q

Cytotrophoblast is derived from what component of the placenta?

A

Fetal Component

107
Q

Syncytiotrophoblast is derived from what component of the placenta?

A

Fetal component

108
Q

Decidua basalis is derived from what component of the placenta?

A

Maternal component

109
Q

What is the Cytotrophoblast?

A

Part of the fetal component of the placenta that has:

  • inner laver of chorionic villi
  • Cytotrophoblast makes Cells
110
Q

What is the Synctiotrophoblast?

A

Part of the fetal component of the placenta and has:

  • Outer layer of chorionic villi
  • synthesizes and secretes hormones (eg hCG which is structurally similar to LH)
  • Stimulates corpus luteum to secrete progesterone during the first trimester)

Syncytiotrophoblast synthesizes hormones

*Lacks MHC-1 expression → ↓ chance of attack by the maternal immune system*

111
Q

What helps prevent attack of the fetal component placenta from the maternal immune system?

A

Syncytiotrophoblast lacks MHC-1 expression → ↓ chance of attack by the maternal immune system

112
Q

What is the Decidua basalis?

A

The maternal component of the placenta that is:

  • Derived from endometrium
  • Maternal blood in lacunae
113
Q

Decidua basalis is derived from

A

Maternal endometrium

114
Q

Umbilical arteries function

A

Return deoxygenated blood from fetal internal iliac arteries to placenta

115
Q

Umbilical vein function

A

Supplies oxygenated blood from placenta to fetus, drains into IVC via liver or via ductus venosus

116
Q

How many umbilical arteries are there?

A
  • 2
  • However, a single umbilical artery (2 vessel cord) is associated with congenital and chromosomal anomalies
117
Q

How many umbilical veins are there?

A

1

118
Q

Umbilical veins are derived from?

A

Allantois

119
Q

Umbilical arteries are derived from?

A

allantois

120
Q

What is the Urachus?

A

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

Allantois becomes the urachus, a duct between fetal bladder and umbilicus.

Failure of urachus to involute can lead to anomalies that may increase risk of infection and/or malignancy (eg adenocarcinoma) if not treated.

Obliterated urachus is represented by the median umbilical ligament after birth, which is covered by median umbilical fold of the peritoneum

121
Q

Failure of the urachus to…

A

failure of urachus to involute can lead to anomalies that may increase risk of infection and/or malignancy (eg adenocarcinoma) if not treated

122
Q

Describe patent urachus

A

Total failure of urachus to obliterate → urine discharge from umbilicus

123
Q

Describe urachal cyst

A
  • Partial failure of urachus to obliterate; fluid-filled cavity lined with uroepithelium, between umbilicus and bladder.
  • Cyst can become infected and present as painful mass below umbilicus
124
Q

Describe vesicourachal diverticulum

A

Slight failure of urachus to obliterate → outpouching of bladder

125
Q

What is the Vitelline duct?

A

7th week - obliteration of vitelline duct (omphalomesenteric duct), which connects yolk sac to midgut ligament

126
Q

Vitelline duct AKA

A

Omphalomesenteric duct

127
Q

Omphalomesenteric duct AKA

A

Vitelline duct

128
Q

What is vitelline fistula?

A

Vitelline duct fails to close → meconium discharge from umbilicus

129
Q

What is meckel diverticulum?

A
  • Partial closure of vitelline duct, with patent portion attached to ileum (true diverticulum)
  • May have heterotopic gastric and/or pancreatic tissue → melena, hematochezia, abdominal pain
130
Q

What is Hematochezia?

A

Hematochezia is the passage of fresh blood through the anus, usually in or with stools (contrast with melena).

131
Q

Vitelline duct failures

A
  • Vitelline fistula
  • Meckel diverticulum
132
Q

Aortic arch derivatives

A
  • 1st - Part of the maxillary artery (branch of external carotid) - 1st arch is maximal
  • 2nd - Stapedial artery and hyoid artery - Second = Stapedial
  • 3rd - Common Carotid artery and proximal part of internal Carotid artery - C is the 3rd letter of the alphabet
  • 4th - on left, aortic arch; on right, proximal part of right subclavian artery - 4th arch (4 limbs) = systemic
  • 6th - Proximal part of pulmonary arteries and (on left only) ductus arteriosus - 6th arch = pulmonary and the pulmonary-to-systemic shunt (ductus arteriosus).
133
Q

What is Bronchial apparatus?

A
  • Composed bronchial clefts, arches, pouches.
  • Bronchial clefts - derived from ectoderm. Also called bronchial grooves.
  • Branchial arches - derived from mesoderm (muscles, arteries) and neural crest (bones, cartilage)
  • Branchial pouches - derived from endoderm

CAP covers outside to inside:

Clefts = ectoderm

Arches = mesoderm + neural crest

Pouches = endoderm

134
Q

Branchial apparatus is composed of?

A
  • Branchial clefts
  • Branchial arches
  • Branchial pouches
135
Q

Branchial clefts AKA

A

Branchial grooves

136
Q

Branchial clefts derived from?

A

derived from ectoderm

137
Q

Branchial arches derived from?

A

derived from mesoderm (muscles, arteries) and neural crest (bones, cartilage)

138
Q

Branchial pouches derived from?

A

derived from endoderm

139
Q

Branchial apparatus derivatives Mnemonic

A

CAP

Clefts = ectoderm

Arches = mesoderm + neural crest

Pouches = endoderm

140
Q

Branchial cleft derivatives

A
  • 1st cleft develops into external auditory meatus
  • 2nd through 4th clefts form temporary cervical sinuses, whic are obliterated by proliferation of 2nd arch mesenchyme
  • Persistent cervical sinus → branchial cleft cyst within lateral neck, anterior to sternocleidomastoid muscle
141
Q

1st branchial cleft derivative

A

1st branchial cleft develops into external auditory meatus

142
Q

2nd-4th branchial cleft derivative

A

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

143
Q

2nd branchial arch derivatives: Cartilage

A

Reichert cartilage:

  • Stapes
  • Styloid process
  • lesser horn of hyoid
  • Stylohyoid ligament
144
Q

Persistent cervical sinus derivative

A

Persistent cervical sinus → branchial cleft cyst within lateral neck, anterior to sternocleidomastoid muscle

145
Q

1st branchial arch derivatives: Cartilage

A
  • Maxillary process → Maxilla, zygoMatic bone
  • Mandibular process
    • → Meckel cartilage
    • → Mandible, Malleus and incus, SphenoMandibular ligament
146
Q

3rd branchial arch derivatives: Cartilage

A

Greater horn of hyoid

147
Q

4th-6th branchial arch derivatives: Cartilage

A
  • Arytenoids
  • Cricoid
  • Corniculate
  • Cuneiform
  • Thyroid
  • (Used to sing and ACCCT)
148
Q

4th-6th branchial arch derivatives: Muscles

A

4th arch: most pharyngeal constrictors; cricothyroid, levator veli palatini

6th arch: all intrinsic muscles of larynx except cricothyroid

149
Q

3rd branchial arch derivatives: Muscles

A

Stylopharyngeus (think of stylopharyngeus innervated by glossopharyngeal nerve)

150
Q

2nd branchial arch derivatives: Muscles

A

Muscles of facial expression

Stapedius

Stylohyoid

platySma

Posterior belly of digastric

151
Q

1st branchial arch derivatives: Muscles

A
  • Muscles of Mastication
    • teMporalis,
    • Masseter,
    • lateral and Medial pterygoids
  • Mylohyoid
  • anterior belly of digastric, tensor tympani, anterior 2/3 of tongue, tensor veli palatini
152
Q

1st branchial arch derivatives: Nerves

A

CN V3 chew

153
Q

2nd branchial arch derivatives: Nerves

A

CN VII (facial expression) smile

154
Q

3rd branchial arch derivatives: Nerves

A

CN IX (stylo-pharyngeus)

Swallow stylishly

155
Q

4th-6th branchial arch derivatives: Nerves

A
  • 4th arch: CN X (superior laryngeal branch)
    • simply swallow
  • 6th arch: CN X (recurrent/inferior laryngeal branch)
    • speak
156
Q

1st branchial arch derivatives: abnormalities

A
  • Pierre Robin Sequence
  • Treacher Collins Sndrome
157
Q

2nd branchial arch derivatives: abnormalities

A
  • Pierre Robin Sequence
  • Treacher Collins Syndrome
158
Q

What is Pierre Robin Sequence?

A

Abnormality in 1st and 2nd branchial arches

  • micrognathia
  • glossoptosis
  • cleft palate
  • airway obstruction
159
Q

What is Treacher Collins Syndrome?

A

Abnormality in 1st and 2nd branchial arches

  • Neural crest dysfunction → mandibular hypoplasia, facial abnormalities
160
Q

3rd-6th branchial arches: Comments

A
  • Arches 3 and 4 form posterior 1/3 of tongue
  • Arch 5 makes no major developmental contributions
161
Q

3rd and 4th branchial arches form

A

Arches 3 and 4 form the posterior 1/3 of the tongue

162
Q

5th branchial arch developmental contributions

A

The 5th branchial arch makes no major developmental contributions

163
Q

Cranial Nerve V2 type of function

A

Sensory only

164
Q

Branchial Arch Mnemonic

A

When at the restaurant of the golden arches, children tennd to first chew (1st arch), then smile (2nd arch) and then swallow stylishly (3rd arch) or simply swallow (4th arch), and then speak (6th arch)

165
Q

Branchial pouches with derivatives

A

1, 2, 3 and 4

166
Q

1st Branchial pouch derivatives

A
  • Middle ear cavity
  • Eustachian tube
  • Mastoid air cells
167
Q

1st Branchial pouch notes

A

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

168
Q

2nd Branchial pouch derivatives

A
  • Epithelial lining of palatine tonsil
169
Q

3rd Branchial pouch derivatives

A
  • Dorsal wings → inferior parathyroids
  • Ventral wings → thymus
170
Q

3rd Branchial pouch notes

A
  • 3rd pouch contributes to 3 structures (thymus, left and right inferior parathyroids)
  • 3rd-pouch structures end up below 4th-pouch structures
171
Q

4th Branchial pouch derivatives

A
  • Dorsal wings
    • → superior parathyroids
  • Ventral wings
    • → ultimobranchial body
    • → parafollicular (C) cells of thyroid
172
Q

Branchial Pouch Derivatives Mnemonic

A

Ear, tonsils, bottom-to-top:

1 (ear)

2 (tonsils)

3 dorsal (bottom for inferior parathyroids)

3 ventral (to = thymus)

4 (top = superior parathyroids)

173
Q

What is DiGeorge Syndrome?

A
  • Chromosome 22q11 deletion
  • Aberrant development of 3rd and 4th pouches → T-cell deficiency (thymic aplasia) and hypocalcemia (failure of parathyroid development)
  • Associated with cardiac defects (conotruncal anomalies)
174
Q

What is Cleft lip?

A

Failure of fusion of the maxillary and merged medial nasal processes (formation of 1o palate)

175
Q

Pathophysiology of Cleft lip

A

Failure of fusion of the maxillary and merged medial nasal processes (formation of 1o​ palate)

176
Q

Cleft palate pathophysiology

A

failure of fusion of the two lateral palatine shelves or failure of fusion of lateral palatine shelves with the nasal septum and/or median palatine shelf (formation of 2o palate)

177
Q

Cleft lip and cleft palate etiologies

A

cleft lip and cleft palate have distinct multifactorial etiologies, but often occur together

178
Q

Female genital embryology

A
  • Default development
  • Mesonephric duct degenerates and paramesonephric duct develops
179
Q

Male genital embryology

A
  • SRY gene on Y chromosome - produces testis-determining factor → testes development
  • Sertoli cells secrete Müllerian inhibitory factor (MIF) that suppresses development of paramesonephric ducts
  • Leydig cells secrete androgens that dtimulate development of mesonephric ducts
180
Q

Describe the role of the Paramesonephric (Müllerian) duct

A
  • Develops into female internal structures - fallopian tubes, uterus, upper portion of vagina (lower portion from urogenital sinus)
  • Male remnant is appendix testis
181
Q

Müllerian agenesis AKA

A

Mayer-Rokitansky-Küster-Hauser Syndrome

182
Q

Mayer-Rokitansky-Küster-Hauser Syndrome AKA

A

Müllerian agenesis

183
Q

Describe Müllerian agenesis

A

may present as 1o amenorrhea (due to a lack of uterine development) in females with fully developed 2o characteristics (functional ovaries)

184
Q

Mesonephric duct AKA

A

Wolffian duct

185
Q

Wolffian duct AKA

A

Mesonephric duct

186
Q

Describe the role of the mesonephric duct in genital embryology

A

Develops into male internal structures (except the prostate)

(SEED)

  • Seminal vesicles
  • Epididymis
  • Ejaculatory duct
  • Ductus deferens
187
Q

Wolffian duct female remnant

A

Female remnant is Garter duct

188
Q

Paramesonephric duct male remnant

A

male remnant is appendix testis

189
Q

Describe the mechanism of sexual differentiation abnormalities

A
  • No Sertoli cells or lack of Müllerian Inhibitory Factor (MIF) → develop both male and female internal genitalia and male external genitalia
  • 5α-reductase deficiency - inability to convert testosterone into DHT → male internal genitalia, ambiguous external genitalia until puberty (When ↑ testosterone levels cause masculinization)
190
Q

Sexual differentiation Mnemonic

A

In the testes:

  • Leydig Leads to male (internal and external) sexual differentiation
  • Sertoli Shuts down female (internal) sexual differentiation
191
Q

Sexual differentiation diagram pg 604

A
192
Q

Uterine anomalies AKA

A

Müllerian duct abnormalities

193
Q

Types of Uterine anomalies

3 listed

A
  • Septate uterus
  • Bicornuate uterus
  • Uterus didelphys
194
Q

What is septate uterus?

A
  • A Uterine anomaly
  • A common anomaly vs normal uterus
  • Incomplete resorption of septum
  • ↓ fertility and early miscarriage/pregnancy loss
195
Q

septate uterus treatment

A

Treat with septoplasty

196
Q

What is Bicornuate uterus?

A
  • Incomplete fusion of Müllerian ducts

↑ risk of complicated pregnancy, early pregnancy loss, malpresentation, prematurity

197
Q

What is Uterus didelphys?

A
  • Complete failure of fusion → double uterus, cervix, vagina
  • Pregnancy possible
198
Q

Uterine anomalies pg 605

A
199
Q

Genital tubercle -estrogen→

A
  • Glans clitoris
  • Vestibular bulbs
200
Q

Genital tubercle -testosterone→

A
  • Glans penis
  • Corpus cavernosum and spongiosum
201
Q

Urogenital sinus -estrogen→

A
  • greater vestibular glands (of Bartholin)
  • Urethral and paraurethral glands (of Skene)
202
Q

Urogenital sinus -testosterone→

A
  • Bulbourethral glands (of Cowper)
  • Prostate gland
203
Q

Urogenital folds -estrogen→

A

Labia minora

204
Q

Urogenital folds -testosterone→

A

Ventral shaft of penis (penile urethra)

205
Q

Labioscrotal swelling -estrogen→

A

Labia majora

206
Q

Labioscrotal swelling -testosterone→

A

Scrotum

Human Reproduction (40 decks)

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