Week 10 Study Guide0

Week 10 Study Guide0 - Week 10 Study Guide The Adrenal...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Week 10 Study Guide The Adrenal Gland 1. The Adrenal Cortex a) Zona Glomerulosa 1) Mineralocorticoids a. Aldosterone 1. The RAAS Pathway b. Deoxycortisone (DOC) b) Zona Fasciculata 1) Glucocorticoids a. Cortisol c) Zona Reticularis 1) Androgens a. Androstenedione b. DHEA c. DHEA-S 2. The Adrenal Medulla a) Catecholamines 1) Epinephrine 2) Norepinephrine The Adrenal Gland As aforementioned in the “Week 3 Study Guide”, the adrenal gland is derived from two distinct embryologically derived tissues. The adrenal cortex is a true endocrine gland of epidermal origin whereas the adrenal medulla is a specialized neuroendocrine tissue derived from the sympathetic nervous system. The adrenal cortex is composed of three distinct layers, the zona glomerulosa, the zona fasciculata, and the zona reticularis. Refer to Figure 47 . These three layers are differentiated by an asymmetric distribution of various enzymes, which convert the cholesterol precursor to specific steroid hormones. For example, the zona glomerulosa secretes the mineralocorticoids, whereas the zona fasciculata preferentially secretes the glucocorticoids, and the zona reticularis primarily secretes the androgens. It was recently discovered that the zona fasciculata can also secrete the androgens and the zona reticularis also secretes the glucocorticoids. The main difference between the zona glomerulosa from these two layers is that the zona glomerulosa lacks 17-α-hydroxylase, which converts progesterone to 17-α- hydroxyprogesterone, the precursor to both the androgens and the glucocorticoids. Refer to Figure 48. Instead, the zona glomerulosa contains 21-alpha-hydroxylase, which is absent in the zona fasciculata and and zona reticularis and which converts progesterone to the mineralocorticoids, deoxycorticosterone (DOC) and aldosterone. As a result, the zona glomerulosa only participates in the Δ4 pathway, whereas the other two layers undergo the Δ5 pathway. Upon stimulation, the adrenal cortex endocrine cells exhibit increased rates of cholesterol uptake, P450 scc (20,220 desmolase) activity, and upregulation of STAR, which is the enzyme that primarily regulates steroid hormone synthesis by translocating cholesterol into the mitochondrial matrix, where hormone synthesis occurs.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Figure 47. The Adrenal Gland. The zona reticularis is the layer closest to the medulla (posted with permission from The McGraw Hill Companies, Inc. A B Figure 48. Adrenal Cortex Steroid Hormone Synthesis.
Background image of page 2
The Adrenal Cortex The Androgens The zona reticularis secretes androstenedione, DHEA, and DHEA-S. The contribution of the adrenal cortex androgens is relatively insignificant in males. However, in females 40% of the androgens are synthesized from the adrenal cortex. It is for this reason that as women approach post-menopause they may undergo various degrees of virilization, that is, they may develop masculine secondary sex characteristics, such as facial hair and a deepened voice. The Mineralocorticoids
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 8

Week 10 Study Guide0 - Week 10 Study Guide The Adrenal...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online