Adrenal Histology & Physiology
What are the major products of Zona reticularis stimulation and what hormone stimulates their release?
ACTH stimulates Zona Reticularis to release DHEA and Androstenedione.
In the adrenal gland, structures are innervated by the pre-ganglionic fibers and what structures are innervated by the post ganglionic fibers?
Preganglionic fibers innervate the Chromaffin cells of the adrenal medulla. Post ganglionic fibers from Greater Splanchnic distribute through the celiac plexus and innervate the vasculature in the adrenal gland as a whole.
What layer of the adrenal cortex secretes glucocorticoids?
Zona Fasciculata secretes Cortisol, a glucocorticoid. A small amount of cortisol is also produced and secreted by the zona reticularis.
What is the primary secretion of Zona Glomerulosa and what stimulates its release?
Zona Glomerulosa primarily secretes Aldosterone in response to ANG 2 stimulation via Rennin-Ang-Aldosterone system (RAAS).
What sublayer of the adrenal cortex secretes mineral corticoids?
Zona Glomerulosa secretes aldosterone, a mineral corticoid.
Starting at the capsule, name the different sub layers of the adrenal cortex.
Zona Glomerulosa. Zona Fasciculata. Zona Reticularis.
What cell is found in the adrenal medulla and from what embryonic cell type does it arise from?
Chromaffin cells are located in the adrenal medulla. These cells arise from neural crest cells.
What is the function of Phenylethanolamine N-methyl trasnferase, what cofactor does it require to function, and in what part of the adrenal gland is this enzyme expressed?
PAM transerfase functions to convert norepi into epi in the adrenal medulla. PAM requires S-adenosylmethionine, or SAM, as a cofactor to conduct this conversion.
What embryonic tissue gives rise to the adrenal cortex?
Splanchnic mesoderm.
What is the primary secretion of Zona Fasciculata and what stimulates its release?
Zona Fasciculata primarily secretes Cortisol in response to ACTH.
What adrenal structure is derived from splanchnic mesoderm?
Adrenal Cortex.
What two regions of the adrenal cortex produce and secrete cortisol and which layer is the primary source?
Cortisol is produced and secreted primarily by Zona Fasciculata, but a small amount is produced by the Zona Reticularis.
What embryonic cell type gives rise to the renal medulla?
Neural Crest Cells.
ACTH is a trophic hormone, where in the adrenal cortex would you expect to see hypertrophy in a patient with chonic elevated ACTH levels?
ACTH stimulates both the Zona Fasciculata and Zona Reticularis to secrete cortisol and androgens, respectively. These two sublayers of the adrenal cortex will experince hypertrophy in chronic elevated ACTH levels.
In the adrenal gland, what structure is derived from neural crest cells?
Adrenal Medulla.
What arteries supply the adrenal gland and from what parent arteries do they arise from?
Adrenal gland has three primary arteries that supply it. Superior Suprarenal Artery: Arises from Inferior Phrenic Artery. Middle Suprarenal Artery: Arises directly from Abdominal Aorta. Inferior Suprarenal Artery: Arises from the Renal Artery.
What is unique about the nerve fibers that innervate the adrenal medulla and based on this information, what can be said about the adrenal medulla's physiological behavior?
Adrenal medulla is directly innervated by preganglionic fibers from greater splanchnic instead of post ganglionic fibers from a prevertebral ganglia. This means that the adrenal medulla behaves like a large ganglion physiologically.
Where is aldosterones site of action, what cells does it target, and what processes does it effect?
Aldosterone targets principal cells of the nephron's DCT. Aldosterone upregulates Na/K ATPase activity and increases the expression of sodium channels on the luminal face. Increase sodium and water reabsorption results.
What are the two ways that blood can reach the adrenal medulla?
Blood arrives in the adrenal medulla via long cortical arteries, also called medullary arteries and through connected venous sinusoids from the adrenal cortex.
How is the vasculature of the liver similar to that of the adrenal gland?
Both structures use sinusoids to distribute blood to the tissues. Additionally, the venous drainage from both structures converge on a central vein, sometimes called a medullary vein in the adrenal gland.
What is significant about the adrenal cortex sinusoids emptying into the adrenal medulla with regards to epinephrine production?
Glucocoriticoids from Zona Fasciculata regulate the expression of Phenylethanolamin N-methyl transferase enzyme which is responsible for converting Norepi into Epi.
What nerve innervates the adrenal gland, what part of the adrenal gland actually receives nervous signals, and from what spinal level do these fibers arise from?
Greater splanchnic, from T5-T9 spinal levels, innervates the adrenal glands. Only the adrenal medulla actually receives nerve fibers that synapse with the Chromaffin cells.
With regards to the adrenal gland innervation, what ganglion does the greater splanchnic nerve preganglionic fibers synapse in and with what never plexus do they distribute with?
Preganglionic fibers synapse in the celiac plexus. Post ganglionic fibers then distribute through the celiac plexus to innervate the vasculature of the adrenal gland.
Short cortical arteries of the adrenal gland provide blood to what part of the gland and through what plexus is the blood distributed?
Short cortical arteries supply blood to the adrenal cortex via the Subcapsular Plexus.
