Endocrine -- Pituitary and Pineal Flashcards
The pituitary gland is attached to what part of the brain? What structure attaches it?
Hypothalamus. Infundibulum.
Name the glandular portion of the pituitary.
Adenohypophysis
Embryonic Origin of Adenohypophysis?
Ectoderm of Primitive Oral Cavity
Regions of the adenohypophysis?
Pars distalis, Pars tuberalis, and pars intermedia
Name the neural portion of the pituitary.
Neurohypophysis.
Embryonic origin of neurohypophysis?
Neuroectoderm
Regions of neurohypophysis?
Pars nervosa and infundibulum
Components of the Anterior Lobe of the Pituitary?
Pars distalis and pars tuberalis
Components of the posterior lobe of the pituitary?
Pars intermedia and pars nervosa
Where do the signals that trigger anterior pituitary activity come from?
Peptide hormones from specialized neurons of the hypothalmic nuclei
How do peptide hormones get from the hypothalmic nuclei to the anterior pituitary?
Capillary plexus of the infundibulum
Name the blood supply of the pituitary
Superior and Inferior hypophyseal arteries
Inferior hypophyseal artery supplies…
Pars Nervosa
Superior hypophyseal arteries supply….
median eminence, upper infundibulum, and lower infun. via a connection to inferior
How the the arteries supplying the median eminence and infundibulum end?
Capillary plexuses
What vein drain the areas supplied by the capillary plexuses?
Hypophyseal portal veins
Name the two broad categories of cells in the pars distalis.
Chromophobes and Chromophiles.
Describe chromophobes appearance.
Poorly staining, appear clear/white. Approx 50% of cells.
Name types of chromophobes.
Undifferentiated non-secretory cells, degranulated chromophils, and connective tissue/follicular cells.
Why keep follicular cells around?
They form a stromal network to support chromophil cells and may have phagocytic functions.
Name two types of chromophiles.
Acidophiles and Basophiles.
Describe acidophile staining.
Stains with eosin and orange G – not PAS.
Name the two listed acidophiles.
Somatotrophs and Mammotrophs
What do somatotrophs make? Who Controls them?
Growth hormone (Somatotropin). Controlled by GH-releasing/inhibiting factor (Somatostatin).
What do mammotrophs make?
Prolactin
What does prolactin do?
Stimulates and maintains lactation
Who controls mammotrophs?
Thyrotropin-releasing factor (TRF) and Prolactin-inhibiting factor (dopamine)
Name the three types of basophiles mentioned in the packet. What do they secrete (in a non-specific sense)
Gonadotrophs, Corticotrophs, and Thyrotrophs secrete glycoprotein hormones.
How do Basophile cells stain?
Stain with hematoxylin and other basic dyes. Hormones stain PAS-positive.
What hormones are released by gonadotrophs?
FSH and LH
What does FSH do?
In women – stimulated development of ovarian follicles
In men – Stimulates androgen binding protein production of Sertoli cells
What does LH do?
In women – stimulates steroidogenesis in ovarian follicles and corpus luteum.
In men – Controls rate of testosterone synthesis from Leydig Cells.
What do corticotrophs make?
Adrenocorticotropin (ACTH)
What does ACTH do?
Stimulates growth and steroid synthesis in zona fasciculata and zona reticularis
What do thyrotrophs secrete?
Thyrotropin (Thyroid-stimulating hormone)
Who controls thyrotroph secretion?
TRF
What can an H&E stain distinguish in the pituitary?
Acidophils, Basophils, and chromophobes.
What is the pars tuberalis?
A highly vascular region containing the veins of the hypophyseal portal system. Contains mostly gonadotropes.
What is the pars intermedia? What cell types does it contain?
A small region in humans that contains basophils, chromophobe cells, and Rathke’s cysts.
What are Rathke’s cysts?
Cuboidal epithelium lined cavities. They are remnants of Rathke’s pouch.
What comprises the pars nervosa?
Non-myelinated axonal processes and pituicytes
Where do the pars nervosa axons have their cell bodies?
Paraventricular and supraoptic nuclei of hypothalmus
What are pituicytes?
Astrocyte-like glial cells with fibrillary acidic proteins. They often have pigment granules.
What structure will the end of the neurons (of the pars nervosa) be close to?
Fenestrated capillary network
What do the axons of the pars nervosa contain?
Neurosecretory granules and herring bodies
What are herring bodies?
Large granule filled dilations near axon terminals
What hormones does hypothalmus neurons release?
Oxytocin and antidiuretic hormone (vasopressin) near the capillary plexus.
Specifically – who makes oxytocin
1 – Paraventricular nucleus cells
2 – Supraoptic nucleus cells
What does oxytocin do?
Stimulates milk ejection from mammary glands and uterine smooth muscle contraction during childbirth.
Specifically - who makes ADH?
1 - Supraoptic Nucleus Cells
2 – Paraventricular Nucleus Cells
What does ADH do?
Stimulates water reabsorption by renal-medullary collecting ducts.
What is neurophysin?
A carrier protein that transports neurohypophyseal hormones for transport down axons.
Who is the carrier protein that moves neurohypophyseal hormones down axons?
Neurophysin
Name that disease – Too much growth hormone.
Acromegaly
Prolactin secreting tumors can lead to….
infertility due to lack of ovulation
Most common cause of hypopituarism in adults?
Pituitary tumors (adenomas)
What occurs during intrinsic pituitary destruction?
Hormone secreting cells of the anterior pituitary are destroyed. Can mess with some or all pituitary hormones.
Symptoms of poor pituitary anterior lobe function.
Failure of lactation, amenorrhea (no period), poor thyroid function, adrenal insufficiency
Symptoms of poor pituitary posterior lobe function.
Diabetes insipidus - impairment of water reabs in distal tubuli: polyurea, polydipsia
The pineal gland is covered by…
pia matter
Does the pineal gland have a blood-brain barrier?
No
What divides the pineal into lobes?
Connective tissue septa (trabeculae) from the capsule
What cell types does the pineal consist of?
Pinealocytes and glial cells
What do pinealocytes make?
Melatonin
What is melatonin important for?
Regulation of the sleep cycle
Describe the structure of pinealocytes.
Basophilic with irregular lobed nuclei and distinct nucleoli. Silver stained cells have long tortuous branches.
What is a unique structure feature occasional seen in the pineal gland?
Corpora arenacea (brain sand)
What is brain sand made of? What does it look like?
Calcium phosphate or calcium carbonate granules
Irregular in shape, lamellar in appearance
Innervation of the pineal gland?
Post ganglionic sympathetic nerves from the superior cervical ganglia
Name a stimulus that may alter pineal function.
External lighting causes signals from retinal neurons to inhibit melatonin secretion.
Problems with a pineal tumor?
Stops CSF flow through the aqueduct of Sylvius (causes hydrocephalus)
