Endocrine Devo Flashcards by Meghan May

Both endocrine and exocrine glands are derived from _________. Formation begins as a solid invagination of epithelial cells into the adjacent______

embryonic epithelium

mesenchyme

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The initial invagination and its subsequent development is mediated by reciprocal signaling between the

epithelium and the underlying mesenchyme

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If an_____ gland is to form, the epithelial diverticulum maintains its connection with the epithelium of origin and begins to form a duct system and secretory components. I

exocrine

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if the epithelial diverticulum forms an______ gland, it loses its connection with the epithelium of origin.

endocrine

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In both exocrine and endocrine gland formation, the surrounding_____ will form the connective tissue components of the capsule and any subdivisions of the gland.

mesenchyme

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The Pituitary Gland or Hypophysis is derived from two ectoderm primordia, one from the oral ectoderm, called the ___________and the other from the ________

Hypophyseal Diverticulum(HD) or Rathke’s Pouch

neural ectoderm, the Infundibulum.

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Recent studies suggest that the HD begins as an ectoderm placode located in the midline of a crescent-shaped area of ectoderm adjacent to the cranial end of the neural plate. Moreover, it is believed that the portion of the neural tube adjacent to this placode will become the

infundibulum.

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As a result of embryo folding in the_____ plane, the placode comes to lie in part of the surface ectoderm that will form the roof of the oral cavity, and is located in the midline just ventral to the oropharyngeal membrane.

sagittal

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During week three, the placode epithelium evaginates cranially into the surrounding mesenchyme forming the

HD or Rathke’s pouch.

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Origin of Definitive PItuitary Gland component

The Anterior Wall:

Distal Lobe or Pars Distalis

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Origin of Definitive PItuitary Gland component

The Superior Extension at week 11 =

Tuberal Lobe or pars tuberalis

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Origin of Definitive PItuitary Gland component

The posterior wall =

Intermediate lobe or Pars intermedia

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Origin of Definitive PItuitary Gland component

Infundibulum =

MEdian eminance + pituitary stalk + neural lobe = Posterior pituitiary

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is an inferior, midline diverticulum or thickening in the floor of the Diencephalon during week 3. This grows inferiorly to form the neurohypophysis that consists of the Stalk and the Posterior Lobe (pars nervosa) of the pituitary

The Infundibulum (infundibular process)

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By week 12, neurovascular links between hypothalamus and pituitary are established, HOW?

Axons of hypothalamic neurosecretory cells and glial cells grow into the stalk. The lumen is obliterated except for an infundibular recess of the third ventricle in the floor of the diencephalon.

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Remnants of Rathke’s pouch remaining in the roof of pharynx are called a

Pharyngeal Hypophysis.

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forms in the sella turcica, but can also form along the stalk or in the pharynx. Expansion of the tumor superiorly can impinge on the optic chiasm causing vision problems. The tumor can also cause hydrocephalus as well as pituitary dysfunction by compressing the gland.

tumor forming from Rathke’s pouch remnants is called a **Craniopharyngioma. **

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How does they thyroid gland start out?

The Thyroid Gland begins as a midline invagination of pharyngeal endoderm, theThyroid Diverticulum between 3rd and 4th pharyngeal arches…It extends inferiorly from the floor of the pharynx between the median tongue bud and copula.

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When is the thyroid first visible and what is it’s remanant in an adult?

First visible during week four, the site of this diverticulum will be represented by the foramen cecum in the adult tongue.

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The thyroid primordium becomes bilobed as its distal tip expands. It remains connected to the pharynx by a _____until around week 11. A portion of the duct may persist in the mature thyroid as the pyramidal lobe.

Thyroglossal Duct

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With time, the thyroid diverticulum is displaced_____ lying anterior to the pharynx, hyoid, and forming larynx.

inferiorly

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During week seven, the thyroid arrives at its definitive location

, inferior to the cricoid cartilage and anterior to the trachea (cartilages 2&3).

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The_______ bodies detach from pharyngeal pouch four and migrate or are displaced toward the thyroid diverticulum.

Ultimopharyngeal

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Neural Crest cells invade the ultimopharyngeal bodies prior to separation from the pharynx and will eventually disperse within the thyroid gland as the

Parafollicular Cellsor C Cells.

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What do Parafollicular cells or C cells make?

Calcitonin

Origin of Definitive Thyroid Gland Components Thyroid Follicular Cells

Thyroid Diverticulum (midline)

Origin of Definitive Thyroid Gland Components Parafollicular cells

Neural crest cells from ultimopharyngeal bodies

Origin of Definitive thryoid gland components parathyroid Gland Principal Cells:

Dorsal wing of Pharyngeal pouch 3 and 4

Thyroglossal Duct Cysts can occur at any point along the pathway of thyroid primordium displacement. About half of them are located near \_\_\_\_\_\_\_\_but some are found in the base of tongue or ventral to thyroid cartilage. Thyroglossal duct cysts are\_\_\_\_\_\_\_ structures. They can secondarily rupture or connect to skin forming a fistula.

the body of the hyoid bone, midline

Aberrant Thyroid Tissue can be found anywhere along path of thyroid primordia displacement. It is most commonly located at

the base of the tongue.

The Parathyroid Glands form from pharyngeal pouches

three and four.

What week is the thryoid gland supposed to start migrating down to its final location?

During week 4

If you seen a mass midline in someones neck/throat, what do we suspect it is?

thyroid tissue

The Superior pair of Parathyroids originates from the solid dorsal wing of each ____ pharyngeal pouch. The Inferior pair of Parathyroids originates from the solid dorsal wing of each\_\_\_ pharyngeal pouch.

4th 3rd

Parathyroid cells are recognizable in the pouch by week\_\_\_. The primordia of the parathyroid glands detach from pouch and migrate (become displaced)\_\_\_\_\_. Eventually they join the thyroid diverticulum

five inferiorly

The cortex and medulla have different embryological origins. The cortex produces \_\_\_\_\_\_\_\_while the cells of the medulla produce _________ upon sympathetic stimulation.

steroid hormones epinephrine and norepinephrine

The Adrenal Cortex forms from proliferating coelomic epithelial cellsduring week 4-5. These cells are originate from the _____ covering the medial side of the urogenital ridge between the root of dorsal mesentery and forming gonad.

epithelium

What is the initial or primary wave of adrenal cortical progenitor cells?

During week five, a subset of proliferating cells separates from the coelomic epithelium and enters the underlying mesenchyme.

Later a second wave of proliferating cells separates from the epithelium and enters the underlying mesenchyme were they surround the cells of the primary wave. The epithelial cells become

adrenal cortical cells.

By week\_\_\_\_, a capsule formed from mesenchyme surrounds each adrenal primordium.

nine

What forms the Fetal Adrenal Cortex which is about 20 times larger than the definitive cortex and comprises 80% of the volume of the fetal adrenal gland.

The initial wave of epithelial cells

What stimulates the cortex early during development in a trophoblast? What about later in the development?

productionof hCG ACTH originating from the pituitary stimulates the fetal cortex later in development.

What can't the fetal cortex cannot make progesterone or androstenedione?

enzyme **three beta-hydroxysteroid dehydrogenase** is inactive.

The fetal cortex begins to involute at birth and has regressed completely by ___________ The definitive adrenal gland does not reach its normal size until the child is about\_\_\_\_ years of age.

six months-one yearof age (postnatal). two

The\_\_\_\_\_\_\_\_\_is formed by the **second wave** of proliferating epithelial cells. It begins development in the embryo but this is incomplete at birth.

Definitive Adrenal Cortex

forms a thin layer external to fetal cortex and it's cells will organize into the three zones observed in the adrenal cortex – zona glomerulosa, zona fasciculata and zona reticularis.

Definitive Adrenal Cortex

is a term used to describe the physiological interplay between the placenta, the fetus and the mother.

Maternal-Fetal-Placental Unit

the placenta’s ability to make steroids is incomplete, so it must obtain precursors from the mother and fetus. The mother and fetus (fetal cortex) cooperate to increase\_\_\_\_\_ production by the placenta by providing weak androgens. The placenta has the\_\_\_\_\_\_ enzyme needed to convert the androgen to estrogen.

estrogen aromatase

The cells of the Adrenal Medulla originate from ______ that migrate to the area of the forming cortex prior to capsule formation.

Neural Crest Cells

What makes up the primary adrenal cortex and is activet til birth?

Primary Wave

The crest-derived cells differentiate into the _______ of the adrenal medulla that secrete epinephrine and norepinephrine. Differentiation may be mediated by cortical production of glucocorticoids causing crest-derived progenitor cells to lose their neuronal properties and differentiate

Chromaffin Cells

The medulla is supplied by \_\_\_\_\_\_\_\_nerve fibers also of neural crest origin.In the embryo, chromaffin cells are widely scattered throughout the embryo, but in adults, they only persist in adrenal medulla.

preganglionic sympathetic

Congenital Adrenal Hyperplasia is a group of hereditary disorders of the adrenal gland, The enzyme \_\_\_\_\_\_\_needed to make cortisol and/or aldosterone is mutated leading to a significant **decrease** in activity, so the cortex **produces large amounts of androgen**. The cortex enlarges because of increased ACTH production.

(most commonly 21-hydroxylase)

How does congenital adrenal hyperplasia present in boys? in girls?

In boys,the excess androgen may cause early development of s**econdary sexcharacteristics.** In girls, the excess androgens during development **causes virilization of the forming external genitali**a often resulting in the presence of **ambiguous genitalia** at birth.

The Pineal Gland is located in the\_\_\_\_\_\_ superior to the thalamus. It secretes Melatonin (usually at night) that inhibits the pituitary-gonadal axis of hormonal control.

diencephalon

is a midline, dorsal diverticulum of the roof of the diencephalon. It is visible by week ten or perhaps sooner.

The pineal gland

Pituitary gland is mostly from the

Ectoderm

The thyroid and parathryoid are mostly form the

Endoderm

The adrenal gland is composemd primarly from the

mesoderm