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ENT board review > Empirical Embryology > Flashcards

Empirical Embryology Flashcards

1
Q

At what AOG do the hillocks of His form?

A

4-6 weeks AOG

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2
Q

From what structure do the hillocks of His form?

A

First to second arch

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3
Q

At what AOG do the hillocks of His fuse?

A

7 weeks AOG

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4
Q

At what AOG is the auricle recognizable?

A

15-20 weeks AOG

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5
Q

At what AOG is the tympanic ring formed? When do the ossification centers appear?

A

Mesenchyme condenses around the tympanic membrane to form a c-shaped ring and by the 9th week four centers of ossification appear in the ring and fuse by the 10th week giving rise to the primitive tympanic bone.

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6
Q

At what AOG does the EAC epithelial core begin to reabsorb?

A

21 weeks AOG

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7
Q

At what AOG does the EAC epithelial core completely reabsorb?

A

28 weeks AOG

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8
Q

At what age does the external ear stop growing?

A

9 years old

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9
Q

Anatomic changes in the tube with growth and development include what? (4)

A

“LACE”
L - increased length and diameter
A - increasing tubal angle
C - change in cellular composition of tubal cartilage
E - increased efficiency of tubal opening.

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10
Q

Tubal length in infants vs. adult

A

Tubal length progresses from 17.5 mm in infants to reach an adult length of 37.5 mm.

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11
Q

What are the changes in cellular composition of tubal cartilage during growth and development?

A
  • decrease in cartilage cell density (midcartilaginous portion)
  • increase in intercellular elastin (hinge region between the medial and lateral laminae)
  • medial lamina develops more than the lateral lamina
  • lateral lamina and lateral wall of the tube develop more of an S shape (allow for more efficient tubal recoil)
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12
Q

What are the changes in efficiency of tubal opening during growth and development?

A
  • surface area of the tensor veli palatini

- more perpendicular angle of insertion of the dilatory muscles (dilator tubae) to the cartilaginous tube,

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13
Q

At what AOG do the pharyngeal arches form?

A

Day 28-32

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14
Q

At what AOG do the malleus and incus begin to form?

A

At the 4th week a condensed mesenchymal interbranchial bridge is formed. This connects the upper end of the mandibular visceral bar to the central region of the hyoid visceral bar. It is thought that the head of the malleus and the body of the incus originate from the interbranchial bridge while the manubrium of the malleus, the long process of the incus, the stapedial crura and the lateral (tympanic) surface of the footplate arise from the hyoid visceral bar.

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15
Q

At what AOG does the otic placode appear?

A

Day 25-28 or 3rd week

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16
Q

At what AOG does the optic & nasal placode appear?

A

Day 31-35

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17
Q

At what AOG are the ossicles are clearly formed and are fully formed?

A

Week 15

18
Q

At what AOG is the stapes clearly seen to be separated from the otic capsule?

A

At the 16th week

19
Q

At what AOG do the ossicles get ossified?

A

The malleus and incus gets ossified by the 16th week and the stapes gets ossified by the 18th week.

20
Q

At what AOG are the ossicles are fully developed?

A

At the 25th week

21
Q

At what age does the TM reach its vertical position?

A

At the time of birth the tympanic membrane makes an angle of approximately 30 degrees with the horizontal plane. Its vertical position is only reached by the age of 4 months.

22
Q

At what age does the organ of Corti develop form the epithelium of the cochlear duct?

A

5th week AOG

23
Q

At what age does the organ of Corti reach adult size?

A

25th week AOG

24
Q

At what age does the otic capsule begin to ossify?

A

Ossification of the otic capsule begins in the 15th week. It has 14 distinct centers of ossification.

25
Q

At what age does the otic capsule completely form its bony shell?

A

By the 23rd week these centers are fused without any suture line to form a complete bony shell, the otic capsule.

26
Q

Precursor of Organ of Corti

A

Organ of Kolliker

27
Q

At what week do the ethmoturbinals fuse and regress?

A

8th week

28
Q

Enumerate the structures that the ethmoturbinals (1-5) gives rise to

A

1st ET: ascending portion (agger nasi), descending portion (lateral extension of uncinate)

2nd ET: middle turb

3rd ET: superior turb

4th & 5th ET: supreme turb (when present)

29
Q

What embryological structure gives rise to the inferior turbinate?

A

maxilloturbinal

30
Q

enumerate the embryological structures (5) that contribute to the nose and which part it gives rise to

A

frontonasal prominence (nasal bridge)
2x medial nasal prominence (crest and tip)
2x lateral nasal prominence (alae)

31
Q

At what age does the frontal sinus reach adult size?

A

21 years old

32
Q

At what age does the ethmoid sinus reach adult size?

A

12 years old

33
Q

At what age does the maxillary sinus reach adult size?

A

18 years old

34
Q

At what age does the sphenoid sinus reach adult size?

A

15 years old

35
Q

What is the purpose of the vomeronasal organ?

A

pheromone detection (vestigial remnant)

36
Q

Where is the vomeronasal organ located?

A

pit on the anteroinferior nasal septum

37
Q

Embryologic origin of suprglottis + name the arch

A

bucoopharyngeal primordium from the 3rd and 4th branchial arch

38
Q

Embryologic origin of glottis and subglottis + name the arch

A

tracheobronchial primodium from the 6th branchial arch

39
Q

At what week do the salivary glands begin their development?

A

during the 6th week of life as a solid, ridge-like ingrowths of the oral epithelium

40
Q

Which salivary gland is the first to begin its development? order of the subsequent glands?

A

Parotid anlage is the 1st to develop at 6wk AOG followed by SMG then SL

41
Q

At what week does the parotid gland begin secretion?

A

Secretion by the parotid via parotid duct begins at about 18 weeks of gestation

42
Q

At what week do the cords in the parotid anlage canalize and form ducts?

A

At 10 weeks, these cords are canalized and form ducts with the largest becoming the parotid duct

ENT board review (7 decks)

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