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M2 Endo/Repro > Endocrine Development - Bolender > Flashcards

Endocrine Development - Bolender Flashcards

1
Q
  1. In general, both endocrine and exocrine glands are derived from what type of embryonic tissue?
  2. What second tissue type does the former invade into during the gland’s development?
A
  1. Embryonic epithelium
  2. The adjacent mesenchyme
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2
Q

What components of the mature gland are derived from mesenchyme?

A

The connective tissue components of the capsule and any subdivisions of the gland

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3
Q
  1. As a generalized rule of thumb, when do the endocrine glands begin their formation?
  2. When do they begin to release their hormones?
A
  1. The embryonic period
  2. Early in the fetal period
    • Initial hormone products from fetal glands may be very small or just biologically inactive
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4
Q
  1. What are the two primordia that the pituitary gland is derived from?
  2. What germ layer do each of these primordia originate from?
A
  1. Primordia:
    • Hypophyseal Diverticulum (HD), aka Rathke’s Pouch
    • Infundibulum
  2. Both primordia are ectoderm-derived
    • HD is oral ectoderm
    • Infundibulum is neural ectoderm
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5
Q

The HD / Rathke’s Pouch begins as a **placode **that evaginates cranially to form the pouch.

  1. Following folding in the sagittal plane, where is this placode located in the embryo?
  2. When does the placode evaginate?
  3. What tissue type does it evaginate into?
A
  1. Within the surface ectoderm that will form the roof of the oral cavity. Specifically, in the midline just ventral to the oropharyngeal membrane.
  2. Week 3
  3. Surrounding mesenchyme
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6
Q

When does the HD / Rathke’s Pouch lose its connection with the oral cavity?

A

(Toward the end of) Week 8

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7
Q
  1. Formation of the HD / Rathke’s Pouch is mediated by what two signalling molecules?
  2. What additional signalling molcule promotes proliferation and survival of HD epithelial cells?
A
  1. BMP-4 and FGF-8
  2. Hesx-1
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8
Q
  1. Which half of the pituitary gland is derived from the HD / Rathke’s Pouch?
  2. What is an alternative name for this part of the pituitary?
A
  1. Anterior pituitary
  2. Adenohypophysis
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9
Q
  • What three parts make up the mature anterior pituitary?
  • How is each part formed from the immature HD / Rathke’s Pouch?
A
  1. Pars Distalis
    • Expansion / thickening of the anterior wall of the HD
    • Note: Comprises the bulk of the mature anterior pituitary
  2. Pars Tuberalis
    • A small superior extension
    • Grows along the infundibulum (stalk) of the neurohypophysis and eventually surrounds it
  3. ​Pars Intermedia
    • Forms from the posterior wall of the HD
    • Small and indistinct in humans (Wiki)
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10
Q
  1. When does the pars tuberalis begin to form?
  2. When does it surround the infundibulum?
A
  1. Week 11
  2. Week 16
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11
Q

While observing a microscope section of a mouse pituitary, you notice a small, slit-like gap between the pars distalis and pars intermedia. What are you looking at?

A

The remnant of the original HD lumen

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12
Q

What signalling molecule(s) is/are expressed in the following anterior pituitary cells?

  1. Somatotrophs
  2. Gonadotrophs
  3. Melanotrophs
A
  1. PIT-1 & Wnt
  2. SF-1
  3. HES-1
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13
Q

When can ACTH be first detected in pituitary cells?

LH/FSH?

[Likely (hopefully) low yield]

A

ACTH: Week 8

LH/FSH: Week 10

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14
Q
  1. The infundibulum is an inferior midline diverticulum in the floor of what embryonic tissue?
  2. When does the infundibulum form?
A
  1. The diencephalon
  2. Week 3
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15
Q

When are the neurovascular links between hypothalamus and pituitary established by?

A

Week 12

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16
Q

What is the result of deficient migration / evagination of Rathke’s Pouch?

A

A pharyngeal hypophysis

(aka, pituitary gland in the roof of your mouth. Not good.)

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17
Q
  1. What is the name for a tumor that froms from the remnants of the HD / Rathke’s Pouch?
  2. Where (in the head) does this tumor form?
  3. What symptoms can arise from the mass of the tumor itself?
A
  1. Craniopharyngioma
  2. Typically in the sella turcica
  3. Symptoms:
    • Impingement of optic chiasm –> vision problems
    • Impingement of pituitary itself –> pituitary dysfunction
    • Hydrocephalus
      • Tumor mass blocks the flow of CSF through the ventricular system, causing an accumulation that increases ICP
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18
Q

What type of tissue does the thyroid gland originate from? Where is this precursor located and what is it called?

A

A midline invagination of pharyngeal endoderm, called the Thyroid Diverticulum

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19
Q
  1. When is the thyroid diverticulum first visible?
  2. Where does it extend?
A
  1. Week 4
  2. Inferiorly from the floor of the pharynx, between the median tongue bud and copula
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20
Q
  1. What structure connects the migrating thyroid diverticulum to the pharynx during development?
  2. When does this connecting structure dissapear?
  3. What remnant of this structure can be found in an adult?
A
  1. Thyroglossal Duct
  2. ~Week 11
  3. Foramen cecum of the adult tongue

(N.B. Part of the duct may persist as a “pyramidal” lobe of the thyroid)

21
Q

As the thyroid diverticulum is displaced inferiorly, does it pass anterior or posterior to the hyoid bone?

A

Anterior

22
Q
  1. When does the thyroid arrive at its final location?
  2. Where is this location in relation to the cricoid cartilage?
  3. Which cartilages of the trachea does the mature thyroid lay anterior to?
A
  1. Week 7
  2. Inferior
  3. Cartilages 2 & 3
23
Q
  1. When are follicles visible in the thyroid?
  2. When do the follicle cells begin to produce complete thyroid hormone?
A
  1. By Week 10
  2. By the end of Month 3
24
Q
  1. What primordia to the ultimopharyngeal bodies originate from?
  2. What tissue are the bodies invaded by prior to their migration to the thyroid?
  3. Once the bodies reach the thyroid, they disperse within the gland and form what cells?
  4. What do these cell produce again?
A
  1. 4th pharyngeal pouch
  2. Neural crest
  3. Parafollicular cells / C cells
  4. Calcitonin (reduces plasma Ca2+)
25
Q

What aberrant formation can develop within the remnants of the thyroglossal duct?

What are two complications of these formations?

A

Cysts

Rupture or form a fistula to the skin

26
Q
  1. Where can aberrant thyroid tissue be found?
  2. Where is it most common?
A
  1. Anywhere along the path of thyroid primordia displacement
  2. Base of the tongue
27
Q

The two sets of parathyroid glands form from which primordia? Be specific.

A
  • The superior pair of parathyroids originates from the dorsal wing of each 4th pharyngeal pouch
  • The inferior pair of parathyroids originates from the **dorsal wing **of each 3rd pharyngeal pouch

NOTE THE UNINTUITIVE SPATIAL RELATIONSHIP.

The superior pair begins more caudally than the inferior pair, but ends more cranially.

28
Q

When is it possible to start seeing parathyroid cells in the pharyngeal pouches?

A

Week 5

29
Q

Where can aberrant parathyroid tissue be found?

A

Analagously to the thyroid - anywhere along the parathyroid’s path of inferior displacement

30
Q
  1. The adrenal cortex originates from which cells?
  2. When does this occur?
A
  1. Coelomic epithelial cells on the medial side of the urogenital ridge
  2. Weeks 4-5
31
Q

What transcription factor is expessed in adrenal cortex precursor cells?

A

SF-1 (Steroidogenic Factor-1)

32
Q

During the formation of the adrenal cortex, two successive waves of precursor cells enter the surrounding mesenchyme.

  1. Following the migration of both waves, what is the spatial relationship between the two sets of cells?
  2. What structure does the primary wave eventually form?
  3. What structure does the second wave eventually form?
A
  1. The second wave surrounds the primary wave.
  2. Primary wave –> Fetal adrenal cortex
  3. Second wave –> Adult adrenal cortex
    • (Yes, all of it. The zonas glomerulosa, fasciculata, and reticularis.)
33
Q

By week 9, a capsule of what tissue type surrounds each adrenal primordium?

A

Mesenchyme

34
Q

Compare the sizes of the fetal and adult adrenal cortexes.

A
  • During development, the fetal cortex takes up 80% of the volume of the entire (fetal) adrenal gland
  • The adult cortex, in contrast, is 1/20th the size of the fetal cortex and takes up a much smaller proportion of the entire (adult) adrenal gland
35
Q
  1. Which cells of the placenta stimulate the adrenal cortex during early development?
  2. What protein does this cell type secrete to accomplish this stimulation?
  3. What stimulates the adrenal cortex later in development?
A
  1. Trophoblasts
  2. hCG
  3. ACTH from the fetal pituitary!
36
Q

Why is the fetal adrenal cortex unable to produce the sex hormones progesterone and androstenedione?

What does the fetus rely on to produce these hormones instead?

A

The fetal cortex lacks 3ß-hydroxysteroid dehydrogenase

The placenta produces these hormones instead

37
Q
  1. When does the fetal adrenal cortex completely involute?
  2. When does the definitive adrenal gland reach its normal size?
A
  1. By six months to one year of age (postnatal)
  2. By two years of age
38
Q

What is mean by the term “Maternal-Fetal-Placental Unit” in terms of endocrine development?

A

The mother, fetus, and placenta all cooperate to produce the requisite steroid hormones for the fetus.

While the placenta produces many steroids for the fetus, it cannot produce many precursors. The fetus and mother’s body increase production of weak androgens, which the placenta’s aromatase enzyme allows for conversion to estrogens.

39
Q

The adrneal medulla is derived from which cell type?

What is the name for the mature cells derived from these precursors?

What signal is believed to play a role in differentiating the precursor cells into the mature cells?

A

Neural crest

Chromaffin Cells

Gucocorticoids from the adjacent adrenal cortex

40
Q

The adrenal medulla is supplied by (sympathetic / parasympathetic), (preganglionic / postganglionic) nerve fibers that are also of neural crest origin.

A

sympathetic, preganglionic

41
Q

What is the pathogenesis of Congenital Adrenal Hyperplasia?

Which part of the adrenal gland englarges and why?

A
  • Mutation in enzyme needed for cortisol and/or aldosterone
    • Mostoften 21-hydroxylase
  • The cortex redirects the excess steroid precursors into androgen production
  • Increased ACTH from the pituitary causes hyperplasia
    • Loss of negative feedback from cortisol and/or aldosterone
42
Q

How does Congenital Adrenal Hyperplasia present in boys?

In girls?

A
  • Boys:
    • Early development of secondary sex characteristics
  • Girls:
    • Early virilization of the forming external genitalia
    • Results in ambiguous genitalia at birth
43
Q

Where is the pineal gland located in relation to the thalamus?

A

Superior to the thalamus

44
Q

What does the pineal gland secrete?

When?

How does the pineal gland affect the pituitary gland?

A

Melatonin

Usually at night

Melatonin inhibits the pituitary-gonadal axis

45
Q

How does the pineal gland form?

When is it visible by?

A

It begins as a midline, dorsal diverticulum of the roof of the diencephalon

Visible by about 10 weeks

46
Q

Which of the three germ layers primarily makes up each of the following endocrine glands?

Which glands also contain neural crest?

  1. Pituitary
  2. Thyroid
  3. Parathyroid
  4. Adrenal
A
  1. Pituitary: Ectoderm (two layers)
  2. Thyroid: Endoderm (+ neural crest)
  3. Parathyroid: Endoderm
  4. Adrenal: Mesoderm (+ neural crest (medulla))
47
Q

Which bone of the skull does the pituitary gland untimately reside in?

A

Sphenoid

48
Q
A

M2 Endo/Repro (57 decks)

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