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STEP 1 (1) > Repro-Embryo > Flashcards

Repro-Embryo Flashcards

1
Q

What are the important genes of embryogenesis?

A

Sonic hedgehog

Wnt-7 gene

FGF

Homeobox (Hox)

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2
Q

What is sonic hedgehog involved in during embryogenesis?

A

Involved in patterning along anterior-posterior axis, and CNS development.

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3
Q

Mutation in Hox would result in what?

A

Appendages in wrong locations

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4
Q

What occurs at Day 0 of gestation?

A

Fertilization occurs at the ampulla of the fallopian tubes

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5
Q

What hormones begin to elevate within one week of fertilization?

A

hCG secretion begins after implantation of the blastocyst in the uterine wall (stimulated by progesterone levels from the corpus luteum)

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6
Q

What embryogenic developments occur during week 2 of gestation? Week 3?

A

A bilaminar disc forms (epiblast and hypoblast)

2 weeks= 2 layers

During week 3 gastrulation causes the formation of a trilaminar embryonic disc. Cells from the epiblast invaginate to form the primitive streak and then the endo, meso, and ectoderm. The notochord form from the midline mesoderm and the overlying ectoderm becomes the neural plate (3 weeks= 3layers)

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7
Q

What embryogenic developments occur during weeks 3-8 of gestation?

A

neural tube formed by neuroectoderm and closes by week 4. Organ development begins during this time and fetus is extremely susceptible to teratogens during this time

Note that at week 6 fetal cardiac activity is visible by transvaginal ultrasound, and by week 8 fetal movements occur (gait at week 8)

The genital have male/female characteristics by week 10

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8
Q

When can a heart beat first be heard in a fetus?

A

typically around 4-5 weeks

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9
Q

What else is the fourth week of gestation marked by?

A

the heart begins to beat AND the limbs begin to form

4 weeks= 4 limbs

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10
Q

Describe the timeline between fertilization and implantation in the uterine wall

A

Fertilization occurs at day 0, followed by formation of a zygote at day 2, a morula by day 3, a blastocyst by day 5, and implantation by day 6

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11
Q

What is gastrulation?

A

The process that forms the trilaminar disc during week 3 of gestation. This process establishes the ectoderm, mesoderm, and endoderm.

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12
Q

What does the surface ectoderm develop into?

A

adenohypophysis (from Rathke’s pouch)

lens of the eyes

lining of the oral cavity

sensory organs of the ear and olfactory epithelium

Epidermis

anal canal below the pectinate line

parotid, sweat, and mammary glands

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13
Q

What does the neuroectoderm develop into?

A

Brain (neurohypophysis, CNS neurons, astrocytes, pineal gland)

retinal and optic nerve

spinal cord

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14
Q

What does the neural crest develop into?

A

PNS (dorsal root ganglia, cranial nerves, celiac ganglion, Schwann cells, and ANS)

melanocytes

chromaffin cells of adrenal medulla

parafollicular cells of the thyroid

pia and arachnoid

bones of the skull

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15
Q

What does the mesoderm develop into?

A

Muscle, bone, CT, serous linings of the body cavities (peritoneum)

spleen

CV structures

lymphatics and blood

wall of the gut tube and bladder

urethra, vagina, testes, and ovaries

dermis

kidneys

adrenal cortex

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16
Q

What are the effects of mutated mesodermal development?

A

VACTERL

Vertebral defects

Anal atresia

Cardiac defects

Tracheo-esophageal fistula

Renal defects

Limb defects (bone and muscle)

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17
Q

What does the endoderm develop into?

A

Gut tube epithelium (including anal canal above the pectinate line) and luminal epithelial derivatives (lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, and thyroid follicular cells)

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18
Q

Define agenesis and aplasia

A

Agenesis is the absence of an organ due to absent primordial tissue while aplasia is absent organ despite the presence of primordial tissue

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19
Q

Embryo are most susceptible to teratogens when?

A

During the 3rd’-8th weeks of development when organogenesis is occuring. If mutation occurs before then, either nothing will happen or the fetus will die.

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20
Q

What are the potential teratogenic effects of ACEIs?

A

renal damage

An ACE in the hole, kid

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21
Q

What are the potential teratogenic effects of Alkylating agents?

A

Absence of digits

Alk Charlie

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22
Q

What are the potential teratogenic effects of Aminoglycosides agents?

A

deafness

A mean guy hit the baby in the ear

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23
Q

What are the potential teratogenic effects of DES agents?

A

Vaginal clear cell adenocarcinoma (from vaginal adenosis) and congenital mullerian abnormalities

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24
Q

What are the potential teratogenic effects of Folate antagonist agents?

A

Neural tube defects (includes methotrexate, trimethoprim, and antiepileptic drugs)

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25
Q

What are the potential teratogenic effects of Lithium agents?

A

Ebstein abnormality (apical displaceent of the tricuspid valve)

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26
Q

What are the potential teratogenic effects of tetracyclines agents?

A

discolored teeth

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27
Q

What are the potential teratogenic effects of Thalidomide agents?

A

Limb defects (flipper limbs)

Limb defects with tha-limb-domide

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28
Q

Which is teratogenic, warfarin or heparin?

A

Warfarin

Dont wage warfare on a baby, keep it heppy

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29
Q

What are the potential teratogenic effects of Warfarin agents?

A

bone deformities, fetal hemorrhage, eye problems, SAB

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30
Q

What substance use during pregnancy has been linked to ADHD?

A

smoking. Nicotine is also related to low birth rate, placental problems, SIDS, and preterm labor

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31
Q

How would an iodine deficiency present during childbirth?

A

congenital goiter or hypothyroidism (cretinism)

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32
Q

What teratogen has been linked to increased prevelance of spontaneous abortions and birth defects including cleft palates and neural tube defects?

A

Vitamin A excess

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33
Q

How might X-ray exposure affect a fetus?

A

microcephaly or mental retardation

34
Q

How are dizygotic twins made?

A

These arise from two seperate eggs that are seperately fertilized by 2 different sperm (always 2 zygotes), and will have 2 seperate amniotic sacs and placentas.

35
Q

How are monozygotic twins made?

A

These twins arise from a single fertilized egg (1 sperm and 1 egg) that splits into two zygotes in early pregnancy

36
Q

Conjoined monozygotic twins can arise if cleavage of the zygotes occurs after what point in gestation?

A

Day 13

37
Q

What are the fetal components of the placenta?

A

cytotrophoblasts, which comprise the inner layer of the chorionic villi, and syncytiotrophoblasts, which comprise the outer layer

38
Q

What do cytotrophoblasts do?

A

Make cells

39
Q

What do syncytiotrophoblasts do?

A

secretes hCG, which stimulates the corpus luteum to secrete progesterone during the first trimester (lacks MHC I expression so there is less of a chance of attack by the maternal immune system)

syncytiotrophoblasts synthesis hormones

40
Q

What is the maternal portion of the placenta?

A

Decidua basalis, which is derived from the maternal endometrium

41
Q

What are the contents of the umbilical cord?

A

The umbilical cord consists of 2 umbilical arteries that return deoxygenated blood from fetal internal iliac arteries to the placenta, and a single umbilical vein which supplies oxygenated blood from the placenta to the fetus (drains via the ductus venosus into IVC)

42
Q

The umbilical arteries and veins are derived from what?

A

the allantois

43
Q

When does the allantois form?

A

during the 3rd week from the yolk sac.

44
Q

What happens to the allantois (which removes nitrogenous wastes in utero)?

A

It forms part of the umbilicus and becomes the urachus, a duct between the bladder and yolk sac

45
Q

What happens if the urachus fails to regress (i.e a patent urachus)?

A

urine discharges from the umbilicus after birth

NOTE: A urachal cyst forms when there is partial failure of the urachus to obliterate, leaving a fluid-filled cavity lined with uroepithelium between the umbilicus and the bladder. This can lead to infection or adenocarcinoma

46
Q

What connects the yolk sac to the midgut lumen during gestation?

A

vitelline duct

47
Q

When does the vitelline duct regress?

A

7th week of gestation

48
Q

What happens if the vitelline duct fails to close?

A

A vitelline fistula forms, marked by meconium leaking from the umbilicus after birth

49
Q

What is a Meckel’s divericulum?

A

Partial closure of the vitelline duct before birth, with a patent portion attached to the ileum.

50
Q

What are the derivatives of the first aortic arch?

A

part of the maxillary artery from the external carotid a. (1st arch is maximal)

51
Q

What are the derivatives of the second aortic arch?

A

stapedial artery and hyoid artery

Second= stapedial

52
Q

What are the derivatives of the third aortic arch?

A

Common carotid artery and proximal part of the internal carotid artery

3rd letter of the alphabet is C

53
Q

What are the derivatives of the fourth aortic arch?

A

on the left, the aortic arch, and the proximal aprt of the right subclavian artery on the right

54
Q

What are the derivatives of the sixth aortic arch (fifth=0)?

A

proximal part of the pulmonary aa. and ductus arteriosis

55
Q

Why does the left recurrent laryngeal nerve get caught under the aortic arch?

A

ligamentum arteriosum

56
Q

What is the branchial apparatus?

A

Aka the pharyngeal apparatus, composed of branchial clefts, arches, and pouches

CAP covers outside from inside

Clefts (aka grooves)= ectoderm

Arches= mesoderm (and some neural crest)

Pouches= endoderm

57
Q

What does the first branchial cleft develop into?

A

the external auditory meatus

58
Q

What does the 2nd-4th branchial cleft develop into?

A

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

NOTE: A persistance cervical sinus results in a branchial cervical sinus within the lateral neck

59
Q

What are the cartilage derivatives of the 1st branchial arch?

A

Meckel’s cartilage; mandible, malleus, incus,

mandibular ligament

60
Q

What are the muscle derivatives of the 1st branchial arch?

A

Muscles of mastication (tmeporalis, massester, lateral and medial pterygoids)

Mylohyoid

anterior belly of the digastric

tensor tympani

tensor veli palatini

61
Q

What are the nerve derivatives of the 1st branchial arch?

A

CN V2 and V3 chew

62
Q

What would abnormality of the 1st branchial arch cause?

A

Treacher Collins syndrome: 1st arch neural crest fails to nigrate leading to mandibular hypoplasia, and facial abnormalities

63
Q

What cartilage structures derive from the 2nd branchial arch?

A

Reichert’s cartilage; stapes, styloid process, less horn of the styloid, and stylohyoid ligament

64
Q

What muscle structures derive from the 2nd branchial arch?

A

Muscles of facial expression including the:

stapedius

stylohyoid

posterior belly of the dagastric

65
Q

What nerve structures derive from the 2nd branchial arch?

A

CN VII-smile

66
Q

What cartilage structures derive from the 3rd branchial arch?

A

greater horn of the hyoid

67
Q

What muscle structures derive from the 3rd branchial arch?

A

stylopharyngeus (remember, the sytlopharyngeus is innervated by the glossopharyngeal nerve)

68
Q

What nerve structures derive from the 3rd branchial arch?

A

CN IX (swallow stylishly)

69
Q

What cartilage structures derive from the 4th-6th branchial arch?

A

thyroid, cricoid, arytenoids, corniculate, and cuneiform

70
Q

What muscle structures derive from the 4th-6th branchial arch?

A

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

6th arch: all intrinsic muscles of the larynx except cricothyroid

71
Q

What nerve structures derive from the 4th-6th branchial arch?

A

4th: CN X (superior laryngeal branch)-simply swallow
6th: CN X (recurrent laryngeal branch)-speak

72
Q

Nmeomic for nerve derivation of the branchial arches:

A

When at the restaurant with the golden arches, children tend to first chew (1), then smile (2), then swallow stylishly (3), or simply swallow (4), and then speak (6)

73
Q

What are the derivatives of the 1st branchial pouch?

A

middle ear cavity, eustachian tube, and mastoid air cells

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

74
Q

What are the derivatives of the 2nd branchial pouch?

A

epithelial lining of the palatine tonsil

75
Q

What are the derivatives of the 3rd branchial pouch?

A

dorsal wings- develops into inferior parathyroids

ventral wings- develops into thyrmus

The 3rd pouch develops into 3 structures (thymus, and right/left inferior parathyroids)

76
Q

What are the derivatives of the 4th branchial pouch?

A

dorsal wings- develop into superior parathyroids

77
Q

What is DiGeorge Syndrome?

A

Aberrant development of the 3rd and 4th branchial pouches that results in T-cell deficiency (thymis aplasi) and hypocalcemia

78
Q

What is MEN2A?

A

Mutation in germline RET (neural crest cells) causing:

parathyroid tumor, medullary thyroid cancer, and a pheochormocytoma

79
Q

What causes cleft lip?

A

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

80
Q

What causes cleft palate?

A

failure of fusion of the lateral palatine processes, the nasal septum, and/or the median palatine process (formation of the 2ndary palate)

NOTE: Cleft lip and celft palate have 2 distinct etiologies, but often occur together

81
Q
A

STEP 1 (1) (28 decks)

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