TBL28 - Pituitary Gland Flashcards
What does the pituitary gland develop from?
The pituitary gland develops from Rathke’s pouch, an ectodermal outpocketing from the roof of the oral cavity, and the infundibular stalk, a downward extension of neural ectoderm from the diencephalon
What are the anterior lobe (pars distalis) and posterior lobe (pars nervosa) derivatives of? Do the pars tuberalis and pars intermedia have function in adults?
1) The anterior lobe (pars distalis) and posterior lobe (pars nervosa) are derivatives of the oral ectoderm and neural ectoderm
2) The pars tuberalis and pars intermedia have minimal function in adults
Where does the sellar diaphragm extend between? What does the infundibular stalk perforate to join the posterior lobe in the hypophyseal fossa?
1) The sellar diaphragm extends between the anterior and posterior clinoid processes
2) The infundibular stalk perforates the dural infolding to join the posterior lobe in the hypophyseal fossa
Why can visual deficits result from pituitary tumors and how is the gland surgically accessed?
1) The pituitary gland is close anterolaterally to the optic chiasm and optic nerves, so pituitary lesions or tumors impinging on these structures can cause significant visual deficits
2) The sphenoid air sinus lies inferiorly to the gland, which allows relatively easy transsphenoidal surgical access to it
What arteries do the hypophyseal arteries arise from? What do the superior hypophyseal arteries supply in the median eminence and what is the median eminence?
1) The hypophyseal arteries arise from the internal carotids
2) The superior hypophyseal arteries supply the capillary plexus in the median eminence, the upper end of infundibular stalk that attaches to the hypothalamus
What does the capillary plexus empty into and where do these veins descend in and unite with?
The capillary plexus empties into the hypophyseal portal veins that descend in the infundibular stalk to unite with a second capillary plexus in the anterior lobe
Interpret how this portal venous system regulates secretory function of the anterior lobe.
1) This portal system is critical for control of the adenohypophysis by neurosecretions from hypothalamic neurons that convey releasing and inhibiting hormones to the primary plexus
2) Neurosecretions reach the secondary plexus to regulate release of specific adenohypophysis hormones, which are also secreted into the secondary capillary plexus
What arteries supply capillaries of the posterior lobe? What do the capillary plexuses in both the posterior and anterior lobes drain into?
1) The inferior hypophyseal arteries supply capillaries of the posterior lobe
2) The capillary plexuses in both the posterior and anterior lobes drain into the cavernous sinus
What hormones do the cells of the anterior lobe secrete and what function do these hormones have?
Cells of the anterior lobe secrete growth hormone (stimulates growth of bones, muscles, and viscera), prolactin (stimulates milk production during pregnancy), and ACTH (activates synthesis and release of cortisol from adrenal cortex)
What do FSH and LH regulate and what does LH activate in the testes? What does TSH activate?
1) FSH and LH regulate the menstrual cycle and ovulation, and LH activates synthesis of testosterone in the testes
2) TSH activates synthesis, storage, and release of thyroid hormone
What do clusters of secretory neurons form in the hypothalamus? What is the hypothalamohypophyseal tract formed by and where does it descend into?
1) Clusters of secretory neurons form the paraventricular and supraoptic nuclei in the hypothalamus
2) The hypothalamohypophyseal tract, which is formed collectively by axons of the secretory neurons, descends in the infundibular stalk into the posterior lobe
What is ADH mainly discharged from and into? What does ADH act on?
1) ADH is discharged mainly from axon terminals of the supraoptic neurons into capillaries of the posterior lobe
2) ADH acts on the collecting ducts of the kidney to concentrate urine
What are causes and symptoms of diabetes insipidus?
1) Damage to supraoptic and paraventricular nuclei of the hypothalamus or destruction of the hypothalamohypophyseal tract may interfere with ADH production and lead to the rare diabetes insipidus
2) Symptoms are polyuria, with great amounts (15-20 L) of hypotonic urine produced daily, and polydipsia (extreme thirst), with a tendency to drink large quantities of fluid
What do paraventricular neurons mainly synthesize and discharge and what does this chemical stimulate in a female?
Paraventricular neurons mainly synthesize and discharge oxytocin that stimulates uterine contraction during childbirth and milk ejection during nursing
