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NEURO-ENDO > Endocrine Development > Flashcards

Endocrine Development Flashcards

1
Q

What is Anisotropic growth?

A

Where growth rates are not equal in all directions

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2
Q

What are Oharyngeal arches?

A

Key embryonic structure in the embryo: gives rise to craniofacial structures

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3
Q

What is a Neuroblas?

A

Cell that will develop into a neuron

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4
Q

What is the Mesothelium?

A

Surface layer of mesoderm : simple squamous epithelial cells, mesodermal origin

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5
Q

What is the meaning of Exogenously?

A

Additional/outside

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6
Q

What makes the Forebrain?

A

Telencephalon and Diencephalon

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7
Q

The diencephalon gives rise to what structures?

A

Hypothalamus
Pituitary glands
Pineal gland

Pineal gland and hypothalamus may actually arise from the telencephalon originally and move backwards to final position through growth and folding

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8
Q

Stress is thought to play a role in hypothalamic development. (Due to the location of the hypothalamus its development is not well understood). Also affects postnatal function

True or false?

A

True

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9
Q

Different genes contribute to the development of neurocircuits: FGF8 stimulates growth of GnRH axons
true or false?

A

True

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10
Q

Explain formation of the hypothalamus?

A

Forms from a proliferation of neuroblasts in the diencephalic walls (ie a condensation of neuroblasts forms) in the region of the floor plate.

Formation of mammillary bodies: pea-like swellings on the ventral surface of hypothalamus. These will become the endocrine centres.

A hypothalamus is clearly detectable by 3 months. A new model suggests that there are several movements within the hypothalamus due to anisotropic growth: which displaces other progenitor populations

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11
Q

What is the relationship of the hypothalamus with the pituitary during formation?

A

a, During early embryonic development in vertebrates, a localized thickening called the hypophyseal placode forms at the midline of the rostral ectoderm (blue), adjacent to the part of the central nervous system that is the presumptive hypothalamus. This occurs as the head folds begin to take shape. Indicative of early specification of endocrine tissue.
b, Later in development, the hypophyseal placode remains in close contact with the presumptive hypothalamus, but changes shape as it is pulled upwards, towards the overlying neuroepithelium, to form Rathke’s pouch (RP)

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12
Q

How is the Pituitary gland formed?

A

Ectodermal: but different parts have different ectodermal origins
Adenohypophysis: Anterior pituitary
~ 36d Upgrowth of oral ectoderm of stomodeum gives Rathke’s Pouch

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13
Q

How is the oral cavity formed?

A

Oral cavity formed from a small dimple in the ectoderm. Grows to form the cavity (stomodeum)

Longitudinal section showing the back of the oral cavity (stomodeum)

Pouch visible: rathke’s pouch

Neuroectoderm of neurohypophyseal diverticulum: gives rise to neurohypophyseal bud (floor of hypothalamus)

Neural ectoderm downgrowth (neurohypophyseal diverticulum)

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14
Q

Explain the formation of the Neurohypophysis (posterior pituitary gland)

A

Forms an infundibulum, which folds in and down to surround the developing anterior pituitary

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15
Q

Summarise the development of the pituitary gland?

A

A: Infundibulum and Rathke’s pouch develop from neural ectoderm and oral ectoderm, respectively.

B: Rathke’s pouch constricts at base.

C: Rathke’s pouch completely separates from oral epithelium.

D: Adenohypophysis is formed by development of pars distalis, pars tuberalis, and pars intermedia; neurohypophysis is formed by development of pars nervosa, infundibular stem, and median eminence.

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16
Q

Describe the formation of the pineal gland

A

Pineal gland develops on the roof of the diencephalon

Positioned caudally, it originates as a diverticulum (outgrowing pouch)

Proliferation of the cells in the walls leads to cone shape of the gland. Development not complete until 1-2 years postnatal

17
Q

What is Pineal Hypoplasia?

A

Not enough growth

Associated with retinal disease

18
Q

What are Pineal Tumours?

A

Associated with abnormal puberty development

19
Q

Explain the development of thyroid and parathyroid glands?

A

Form from the pharyngeal pouches and arches.

Pharyngeal arches:
key to creating facial and neck structures

Pharyngeal pouches: endodermal pouches between the arches
3rd pouch → parathyroid glands
4th pouch → other pair of Parathyroid glands
Form during the 4th week. Migrate caudally

20
Q

What is the Haeckel’s theory?

A

Preservation of structures showing evolution

21
Q

What is the importance of Pharyngeal arches?

A

Key to creating facial structures and neck structures

22
Q

What is the Di George syndrome?

A

Lack of thymus and parathyroid glands.

Problems with immunity

Craniofacial features:
•lack of 1st pharyngeal arch,
•palate problems
•Low, notched ears

Heart problems: Ventricular septal defect
Affects tbx1, HIRA and UFDIL genes

23
Q

The thyroid gland forms also from where?

A

Also forms from the pharynx: pharyngeal floor at 2nd arch

Outgrowth of the endoderm. (Thyroid diverticulum), migrates downwards

Cranial NC cells migrate into the parathyroid and thyroid pouches

Expression of FGFs ensure survival and proliferation of cells in the pharyngeal pouches.

24
Q

What is congenital hypothyroidism?

A

genetic defects of transcription factors involved in the development of the thyroid or pituitary gland.

25
Q

Fetal TH is responsible for?

A

Fetal growth in the latter stages of gestation

26
Q

What is Ectopic thyroid?

A

failure to migrate caudally sublingual thyroid gland found in neck at hyoid bone
In 70% of cases it is the only thyroid tissue present. Can be misdiagnosed as a thyroglossal cyst (leftover from thyroid devt)

27
Q

What is the role of the neural crest in endocrine function?

A
  • Neural crest: transient structure
  • Cells form on the boundary of the neural plate.
  • On folding, they end up at the apex of the tube
  • NC cells delaminate to sit above the neural tube. Mesenchymal (Neural Crest)
  • From here, they migrate to form a diverse range of tissues
28
Q

What is the role of the neural crest in endocrine development ?

A

Cranial Neural Crest Cells:
• form connective tissue of thyroid and pituitary glands
• calcitonin producing cells in the parafollicular cells of the thyroid gland.
• Shh expression in the endoderm prevents apoptosis of NCC

Trunk Neural Crest Cells:
cells that travel ventrally form the adrenal medulla

29
Q

What are the components of the adrenal gland?

A

Medulla and cortex

30
Q

How is the Medulla formed?

A

Medulla is formed by the migration of Trunk NC cells to sit above the developing kidney.

31
Q

How the cortex of the adrenal gland formed?

A

Mesenchyme surrounding these cells condenses (6 weeks) and differentiates to form a fetal cortex.

Fetal cortex is later divided into 3 distinct layers and replaced by the adult cortex.

32
Q

Explain adrenal gland maturation

A

Cortex continues to surround the medulla as it grows. At birth (F) all three layers are present and the fetal layer is almost gone by 1 year (G). By 4 years, adult layers have formed, fetal cortex is gone and adrenal gland is smaller than at birth.

Three layers:
Zona fasciculata
Zona glomerulosa
Zona reticularis

33
Q

What is Adrenal hyperplasia?

A

increase in cortex cells
leads to increased androgen production and masculinisation of female genitalia. Rapid growth and skeletal maturation in both sexes.

34
Q

If you know the factors the cells are exposed to: inhibitors, vitamins and paracrine factors it is possible to develop mature Pancreatic β cells.

True or false?

A

True

Replicating Pancreatic β cell development of pluripotent stem cells.

You can cure T1 diabetes

35
Q

What happens during Endocrine disruption?

A

Exposure to exogenous hormones and hormone mimickers/disruptors affects development.

May have multigenerational effects

Moderate amounts have subtle physiological effects.

Phthalates, DDT, Atrazine, bisphenol A

BPA: sensitises tissue to oestrogen
•May predispose to breast cancer in later life

Atrazine: promotes oestrogen by converting testosterone to oestrogen
• produces gonadal abnormalities may produce ovaries as well as testes: hermaphroditism or ambiguous genitalia.

NEURO-ENDO (21 decks)

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