Development of Midline Structures Flashcards

1
Q

Where does the pituitary gland sit?

A

In the sella turcica, or pituitary fossa, of the sphenoid bone

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2
Q

What is the pituitary gland made up of?

A

Anterior and posterior lobe

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3
Q

What is the anterior lobe of the pituitary gland also known as?

A

Adrenohypophysis

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4
Q

What is the embryological origin of the anterior lobe of the pituitary gland?

A

Ectoderm

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5
Q

What kind of tissue is the anterior lobe of the pituitary gland?

A

Endocrine

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6
Q

What is Rathke’s pouch?

A

Idk jono wasn’t very clear

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7
Q

What is the posterior lobe of the pituitary also known as?

A

Neurohypophysis

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8
Q

What is the embryological origin of the posterior lobe of the pituitary?

A

Neuroectoderm

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9
Q

What kind of function does the posterior lobe of the pituitary have?

A

Neuroendocrine

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10
Q

What is the infundibulum?

A

Idk

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11
Q

How are the embryological origins of the anterior and posterior pituitary gland related?

A

They have entirely separate embryological origins, which later become structurally and functionally linked.

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12
Q

What is the posterior pituitary gland derived from?

A

The developing brain

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13
Q

What is the first step in the development of the posterior lobe of the pituitary gland from the developing brain?

A

A down-growth from the dicephalon forms in the midline, called the infundibulum

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14
Q

What happens to the part of the dicephalon from which the infundibulum arises as development proceeds?

A

It becomes the floor of the hypothalamus

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15
Q

What does the connection between the dicephalon and infundibulum become?

A

The pituitary stalk

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16
Q

Where does the infundibulum extend?

A

Down towards the roof of the developing oral cavity

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17
Q

What does the infundibulum retain when it extends down towards the roof of the oral cavity?

A

It’s connection with the brain

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18
Q

How does the infundibulum retain its connection to the brain?

A

By the pituitary stalk

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19
Q

What develops in the pituitary stalk?

A

Nerve fibre tracts

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20
Q

How do nerve fibre tracts develop in the pituitary stalk?

A

They grow down from the hypothalamus

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21
Q

What happens simultaneously to the infundibulum forming?

A

An out-pouching from the roof of the oral cavity grows up to meet the infundibulum

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22
Q

What is the out-pouching that pushes out from the roof of the oral cavity to meet the infundibulum known as?

A

Rathke’s pouch

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23
Q

What happens to Rathkes pouch once it has met the infundibulum?

A

It loses its connection with the roof of the mouth

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24
Q

Where does Rathke’s pouch come to lie?

A

Anterior to the infundibulum, and wrapped around the pituitary stalk

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25
Q

What happens to the cells of Rathke’s pouch?

A

They differentiate into the endocrine cells of the anterior pituitary

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26
Q

What functionally links the anterior lobe and posterior lobe of the hypothalamus?

A

A network of blood vessels, the hypophyseal portal system

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27
Q

What may persistent remnants of Rathke’s pouch form?

A

Cysts

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28
Q

When does the tongue appear in development?

A

4th week

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29
Q

What does the appearance of the tongue in development coincide with?

A

It is about the same time as the palate begins to form

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30
Q

What appears first in development of the tongue?

A

Two lateral lingual swellings

Three medial lingual swellings

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31
Q

What are the lateral lingual swellings derived from?

A

1st pharyngeal arch

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32
Q

What are the medial lingual swellings derived from?

A

1st, 2nd, 3rd, and 4th pharyngeal arch

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33
Q

What part of the tongue is derived from the 1st pharyngeal arch portion of the medial lingual swellings?

A

Tuberculum impar

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34
Q

What part of the tongue is derived from the 2nd and 3rd pharyngeal arch portion of the medial lingual swellings?

A

Cupola

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35
Q

What part of the tongue is derived from the 4th pharyngeal arch portion of the medial lingual swellings?

A

Epiglottal swelling

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36
Q

What happens to the lateral lingual swellings as development proceeds?

A

They over-grow the tuberculum impar

37
Q

What happens to the 3rd arch component of the cupola as development proceeds?

A

It overgrows the 2nd arch component

38
Q

How is the tongue freed from the floor of the oral cavity?

A

Extensive degeneration occurs

39
Q

What part of the tongue is not freed from the floor of the oral cavity?

A

Lingual frenulum

40
Q

What is the general sensory innervation of the anterior 2/3 of the tongue?

A
Lingual nerve (CN VIII - mandibular branch of trigeminal) 
Nerve of 1st pharyngeal arch
41
Q

What is the general sensory innervation of the posterior third of the tongue?

A
Glossopharyngeal arch (CN IX)
Nerve of 3rd pharyngeal arch
42
Q

What is the special sensory innervation to the anterior 2/3 of the tongue?

A

Chorda tympani (CN VII - facial nerve)

43
Q

What pharyngeal arch is the facial nerve related to?

A

2nd pharyngeal arch

44
Q

Where does the nerve of the 2nd pharyngeal arch pass?

A

Into the 1st pharyngeal arch, through the middle ear

45
Q

What is the special sensory innervation of the posterior third of the tongue?

A

Glossopharyngeal nerve (CN IX)

46
Q

What pharyngeal arch is the glossopharyngeal nerve associated with?

A

3rd

47
Q

What are both the intrinsic and extrinsic muscles developed from?

A

Myogenic precursors that migrate into the developing tongue

48
Q

What is the palatoglossus innervated by?

A

The vagus nerve (CN X)

49
Q

What are all muscles of the tongue apart from the palatoglossus innervated by?

A

Hypoglossal nerve (CN XII)

50
Q

What is the first endocrine gland to develop?

A

The thyroid gland

51
Q

Where does the thyroid gland appear in development?

A

On the floor of the pharynx, between the tuberculum impar and cupola

52
Q

What does the thyroid gland appear as in development?

A

An expansion of the mesenchyme

53
Q

Where does the site of origin of the thyroid gland lie in relation to the brachial arches?

A

Between the 1st and 2nd

54
Q

What is the site of origin of the thyroid gland marked by in the adult?

A

Foramen cecum

55
Q

Where is the final position of the thyroid gland?

A

The anterior neck

56
Q

How does the thyroid gland reach its final position from its embryonic origin?

A

At its point of origin, the thyroid bifurcates and descends as a bi-lobed diverticulum, connected by the itsthmus

57
Q

What is the relationship between the thyroid gland and the tongue during its descent?

A

It remains connected to the tongue by the thyroglossal duct

58
Q

What are the constituent cells of the thyroid gland?

A
Follicular cells
Parafollicular cells (C-cells_
59
Q

What do the follicular cells of the thyroid gland secrete?

A

Thyroxine and triiodothyronine

60
Q

What are the follicular cells of the thyroid gland formed from?

A

The thyroid diverticulum

61
Q

What is the thyroid diverticulum derived from?

A

1st/2nd brachial arches

62
Q

What do the parafollicular cells of the thyroid gland secrete?

A

Calcitonin

63
Q

What are the parafollicular cells of the thyroid gland formed from?

A

The ultimobranchial body of the 4th pouch

64
Q

What are the potential thyroid abnormalities of development?

A
Thyroglossal cysts and fistulae 
Ectopic thyroid tissue
First arch syndrome
Di-George syndrome
CHARGE syndrome
65
Q

Where may a thyroglossal cyst lie?

A

At any point along the migratory path of the thyroid gland, but always near, or in, the midline of the neck

66
Q

What are thyroglossal cysts/fistulae?

A

Cystic remnants of the thyroglossal duct

67
Q

What % of thyroglossal cysts are close to, or just inferior, to the body of the hyoid bone?

A

Approximately 50%

68
Q

What is a thyroglossal fissure?

A

When a thyroglossal cyst is connected to the outside by a fistulouscanal, a thyroglossal fissure

69
Q

What is the usual scenario in which a thyroglossal fissure arises?

A

Secondarily, after a rupture of a cyst

70
Q

When may a thyroglossal fistula occur, other than secondary to a rupture of a cyst?

A

May be present at birth

71
Q

Where may ectopic thyroid tissue be found?

A

Anywhere along the path of descent of the thyroid gland

72
Q

Where is ectopic thyroid tissue commonly found?

A

In the base of the tongue, just behind the foramen cecum

73
Q

What pathologies is ectopic thyroid tissue subject too?

A

The same as the thyroid gland itself

74
Q

What is First Arch syndrome?

A

A spectrum of defects in the development of the eyes, ears, mandible, and palate

75
Q

What is First Arch syndrome thought to result from?

A

Failure of colonisation of the 1st arch with neural crest cells

76
Q

What is the presentation of First Arch syndrome known as?

A

Treacher-Collins syndrome

77
Q

What is the inheritance pattern of Treacher-Collins syndrome?

A

Autosomal dominant

78
Q

What is Treacher-Collins syndrome characterised by?

A

Hypoplasia of the mandible and facial bomes

79
Q

What is DiGeorge Syndrome also known as?

A

Congential thymic aplasia

80
Q

What is the abnormality in DiGeorge syndrome?

A

Absence of parathyroid hormone

81
Q

What causes DiGeorge syndrome?

A

Deletion of chromosome 22

82
Q

What are the features of DiGeorge syndrome?

A
Cardiac abnormality (especially tetralogy of Fallot)
Abnormal facies (not a typo)
Thymic aplasia
Cleft palate
Hypocalcaemia/hypoparathyrodism
83
Q

What is the abnormality in CHARGE syndrome?

A

CHD7 heterozygous mutation

84
Q

What does the CHD7 gene code for?

A

Chromodomain helicase DNA-binding domain, an ATP-dependant chromatin remodeller

85
Q

What is CHD7 expression essential for?

A

The production of multipotent neural crest cells

86
Q

What are the features of CHARGE syndrome?

A
Coloboma
Heart defects
Atresia (choanal)
Retardation of growth and development
Genital hypoplasia
Ear defects
87
Q

What is coloboma?

A

Hole in iris

88
Q

What is choanal atresia?

A

Blockage of posterior nasal cavity