Adrenal gland Flashcards
Where are the adrenal glands located?
Situated superiorly over the medial and superior aspect of the kidney
Which types of hormones are secreted by the adrenal glands?
Secretes steroids and catecholamine hormones into systemic circulation
what shape is the right adrenal gland?
Pyramidal shape, contracting with the semi-lunar shape of the left gland
Which type of fascia encloses the adrenal glands?
Perinephric fascia
What is the anatomical relationship between the spleen and adrenal glands?
The spleen is superior to the left adrenal gland
Where does the left adrenal vein drain into?
Traverses into the renal vein
Where does the right adrenal vein drain into?
inferior vena cava
How many arteriole branches supply each adrenal gland?
57 arteriole branches
What is the outer adrenal gland called?
Cortex
What is the inner adrenal gland?
Medulla
What are the three layers of the adrenal cortex?
Zona glomerulosa, zona fasciculata, zona reticularis
Which hormones are secreted from the Zona glomerulsosa?
Aldosterone (mineralcorticoids)
Which hormone is secreted from the zone fasciulata?
Cortisol (A glucocorticoid)
Small proportions of androgens
Which hormone is secreted by the zone reticularis?
Androgens and oestrogens
Smaller proportions of corticosteroids
Which cells are located within the adrenal medulla?
Chromaffin cells
Which hormones are secreted by the adrenal medulla?
Adrenaline and noradrenaline
Which molecule are steroids derived from?
Cholesterol
How many carbon atoms are present in cholesterol?
27
What is the structure of cholesterol?
Cyclic rings
How is cholesterol converted into pregnenolone?
Side chain cleavage (p450scc)
How is pregnenolone converted into progesterone?
3-beta-hydroxy steroid dehydrogenase
What is the next step for progesterone –> aldosterone synthesis?
21-hydroxylase hydroxylates C21, converting progesterone into 11-deoxycorticosterone
How is 11-deoxycorticosterone converted into aldosterone?
11-hydroxylase into corticosterone
How is corticosterone converted into aldosterone?
18-hydroxylase
Describe the pathway of molecules for cholesterol to cortisol synthesis?
Cholesterol –> Pregnenolone –>Progesterone –> 17-hydroxy-progesterone –> 11-deoxycortisol –> cortisol
Which enzymes are involved with cortisol synthesis?
17-hydroxylase
21-hydroxylase
11-hydroxylase
Which hormone influences the synthesis of cortisol?
ACTH
How is cortisol predominantly transported within the body?
Corticosteroid binding globulin
Which transport protein transports 15% of cortisol?
Albumin
Which form is cortisol active?
Unbound form (10%)
What is the function of aldosterone?
Stimulates Na+ reabsorption in the distal convoluted tubule and cortical collecting duct. Essential for kidneys, sweat glands, gastric glands and colon.
Stimulates K+ and H+ secretion in the distal convoluted tubule and cortical collecting duct; alternating pH regulation of the blood.
What effect does aldosterone have on potassium and hydrogen ions?
Stimulates potassium and hydrogen ion secretion in the distal convoluted tubule and cortical collecting duct
What is the mechanism of aldosterone?
permeable, binding to intracellular receptors. Hormone-receptor complex traverses to the nucleus, attaching to the DNA, activating target genes. Hormone-receptor complex behaves as a transcription factor, binding to promoter regions.
Transcription factor results in mRNA transcription, and translation of ion pumps & enzymes. ATPase pump on the basolateral membrane pumps sodium into circulation.
Aldosterone stimulates the synthesis of sodium ion channels in the apical membrane.
How does the glomerulus receive blood?
Afferent arteriole within the nephron
Which arteriole carries blood away from the glomerulus?
Efferent arteriole
Where are the juxtaglomerular cells located?
Lining the ascending limb of the loop of Henle, and the distal convoluted tubule, exposed to the afferent arteriole
What is the function of the juxta-glomerular cells?
Secretes renin
Which region of cells lies adjacent to the JG cells?
Macula densa
What is the function of the macula densa?
Responds to changes in sodium ion concentration.
Which receptors are located on JG cells and afferent arteriole?
beta-1 adrenergic, responds to sympathetic stimulation
Which three factors contribute to renin release?
Decreased renal perfusion pressure
Increased renal sympathetic activity
Decreased sodium load
Which hormone is secreted by the liver, which influences aldosterone synthesis?
Angiotensinogen
What effect does renin have on the renin-angiotensin system?
Renin converts angiotensinogen into angiotensin I
How is angiotensin-1 converted into angiotensin-2?
Angiotensin converting enzymes (ACE)
What effect does angiotensin II have on the zone glomerulosa?
Stimulates the production of aldosterone
What effect does an increase potassium concentration have on angiotensin?
Increases angiotensin concentration
What effect does angiotensin -II have on vasculature?
Vasoconstrictor
Which hormone has a permissive effect (enhancing) On the renin-angiotensin system?
Corticotrophin
What is cortisol typically associated with?
Stress hormone
Where is cortisol made?
Zone fasciculate of the adrenal cortex
What metabolic effects are exerted by cortisol?
Stimulates peripheral protein catabolism,
Hepatic gluconeogenesis
Enhances effects of glucagon and catecholamines
Stimulates glycogenolysis
Fat lipolysis of adipose tissue
Overall effect: Increases blood glucose concentration
What effect does cortisol have on mineralcorticoid receptors?
Behaves as aldosterone, assists with water and sodium ion retention
How is cortisol converted into cortisone?
IIB-Hydroxysteroid dehydrogenase 2, removes cortisol to reduce interference with mineralcorticoid receptors
What is the pattern of secretion of cortisol?
Diurnal rhythms
What is Addison’s disease?
Inadequate secretion of cortisol from adrenal cortex
What are the main causes of Addison’s disease in the UK?
Autoimmune disease
What are the main two main causes of Addison’s disease?
TB and autoimmune disease
How does TB cause Addison’s disease?
TB in the adrenal gland, reduces the cells that consist the zone fasciculate, therefore reducing secretion of cortisol, according to negative feedback system, this would elevate levels of ACTH from the anterior pituitary gland
Which hormonal levels increase in Addison’s?
CRH
ACTH
MSH
What are the clinical effects of Addison’s disease?
Hypoglycaemia Low blood pressure weakness Bronze discolouration Hyponatremia Hyperkalaemia Metabolic acidosis Autoimmune vitiligo Infertility
Why is there bronze pallor and increase pigmentation in Addisons?
Pro-opiomelanocortin precursor protein that is cleaved to form small peptides, including ACTH and MSH
What is MSH?
Melanin stimulating hormone
What are the treatments of Addison’s disease?
Glucose/dextrose intravenous solution
Steroid IV replacement therapy (Hydroxycortisone)
What tests are conducted in regards to the management of Addison’s?
Measure urea electrolytes
Measure blood pressure
Short synacthen test, ACTH, measure cortisol level afterwards
When should cortisol level measurements take place?
8am, when cortisol levels are highest
What is Cushing’s syndrome?
Concerned with elevated levels of cortisol, primarily caused by an adrenal adenoma
What are the main effects of Cushing’s?
Impaired glucose tolerance Hypertension Hyperglycaemia Proximal myopathy (muscle weakness) Mental changes Skin changes Centripetal obesity
What are the common causations of Cushing’s?
Oral consumption of steroids
Ectopic ACTH secretion (Lung cancer)
Where does the adrenal medulla derive from?
Ecotdermal neural crest
Which amino acid is the precursor for adrenaline and noradrenaline
Tyrosine
What stimulates the release of catecholamines in cytoplasmic granules?
Acetylcholine
What molecules are bound to noradrenaline and adrenaline?
Albumin
Which hepatic enzymes degrade catecholamines?
Monoamine oxidase
Catechol-o-methyl transferase
