What two components are most endocrine glands composed of?
Endocrine secretory (epithelium)
Capillary plexus (note: Endocrine organs have rich vascular supply)
Describe the general appearance of an endocrine secretory cell.
Secretory cells are usually polarized (apical face towards vasculature) and rich in organelles such as Golgi, rER, mitochondria.
Where is the pituitary gland located? What structures are nearby it?
Describe its structural division.
In the anterior and inferior aspect of the brain, nestled in the Sella Turcica. It is just posterior to the optic chiasm.
It is split into anterior and posterior (adenohypophysis/neurohypophysis), both suspended by the infundibulum.
Describe the structure and function of the anterior pituitary gland.
How are its hormones released?
It is divided into pars distalis/intermedia/tuberalis and secretes the hormones GH, FSH/LH, ACTH, and prolactin.
These hormones are released by exocytosis into the capillary plexus (hypothalamohypophyseal portal system)
Describe the structure and function of the posterior pituitary gland.
How are its hormones released into circulation?
This gland is comprised of neurons originating in the hypothalamus. It secretes oxytocin and vasopressin.
These hormones are released from Herring bodies (dilations of the neurons rich with neurosecretions)
Which of the anterior pituitary cells are acidophils, and which are basophils?
How are they more reliably identified?
Somatotrophs and lactotrophs are both acidophilic; they outnumber the corticotrophs, thyrotrophs, and gonadotrophs (which are basophilic)
Immunohistochemistry for their secretory products.
What nuclei do the neurons which secrete oxytocin and vasopressin originate from?
What is the source of blood for the hypophyseal system?
Originate from the supraoptic and paraventricular hypothalamic nuclei.
Blood from superior hypophyseal vessels from the internal carotid artery.
Describe the functional unit of the thyroid.
A follicle; comprised of a central colloid (fluid full of inactive thyroid hormone), circumscribed by secretory epithelium. C cells are also interspersed between and within these follicles.
What are the secretory products of thyroid follicular cells?
Of parafollicular C cells?
How can these cells be distinguished based on morphology?
Thyroid follicular cells produce T3, T4, and thyroglobulin.
C cells produce calcitonin.
C cells are larger and paler, and are not as neatly arranged.
What comprises the "stroma" of a parathyroid gland?
What two cell populations can be found here?
The adipocytes (which are abundant here) serve this function.
Chief/principal cells and oxyphil cells.
What are the products of the parathyroid chief cells?
Of the oxyphil cells?
How can you tell them apart?
Chief cells produce PTH.
Oxyphil cells are not secretory (unknown function).
By distribution (they tend to segregate). Oxyphil cells are larger and eosinophilic with small nuclei.
What are the three layers of the adrenal cortex?
Describe their appearances.
What is the product of each layer?
(from superficial to deep)
Glomerulosa: Clusters, produces mineralocorticoids.
Fasciculata: Columns/bundles interspersed by capillaries, produces glucocorticoids.
Reticularis: Cords/network; cells are smaller and may contain lipofuscin, produces androgens (and some glucocorticoids)
Name 3 morphological characteristics of steroid-producing cells.
1. Abundant smooth ER for synthesis.
2. Abundant mitochondria for energy.
3. Membrane lipid droplets (for both, probably)
The adrenal medulla is comprised of cells which secrete ____ and ____. It is innervated by ______. Staining with an oxidizer causes it to turn ____ in color.
Secretes NE/Epi, innervated by preganglionic SNS neurons, and turns brown with oxidant (due to catecholamine presence).
What is the functional unit of the endocrine pancreas?
What cells comprise it? In what proportion?
The islet of langerhans.
Beta > Alpha > Delta > (other cells)
What are the secretory products of the pancreatic islet cells?
How may you distinguish them on histology?
Glucagon (from alpha cells)
Insulin & amylin (from beta cells)
Somatostatin (from delta cells)
Distinguish using IHC against the products.
What is the effect of sympathetic and parasympathetic stimulation of the endocrine pancreas?
SNS: Inhibit insulin release.
PNS: Increase insulin (and glucagon???) release.
What gland is pictured here?
What is labeled?
The posterior pituitary gland (this is the same image as from our lecture!)
What gland is pictured here?
Thyroid; note the large follicles filled with colloid.
What region of the adrenal cortex is pictured?
The zone fasciculata; note the columnar arrangements punctuated by capillaries.