Adrenal Gland Flashcards
Describe the structure of the adrenal gland
- zona glomerulosa (outer cortex)
- zona fasciculata (middle cortex)
- zona reticularis (inner cortex)
- adrenal medulla (centre of gland)
What is the structure of the Zona glomerulosa ?
- cells arranged in clumps
What is the structure of the Zona fasciculata ?
cells arranged in cords alongside the blood sinusoids
What is the structure of the Zona reticularis ?
network of smaller cells
What is the structure of the adrenal medulla ?
loose network of neurosecretory cells surrounded by blood vessels
Function of the adrenal cortex
secretes 3 classes of steroid hormones
- glucocorticoids
- mineralocorticoids
- androgens
function of the adrenal medulla
- part of the sympathetic nervous system
- produces catecholamines (adrenaline and noradrenaline
What makes us the adrenal cortex ?
- Zona glomerulosa
- zona fasciculata
- zona reticularis
What hormone is produced by the zona glomerulosa ?
mineralocorticoid (aldosterone)
What hormone is produced by the zona fasciculata ?
glucocorticoid (cortisol)
What hormone is produced by the zona reticularis ?
glucocorticoids & androgens
What are external stimuli that affect the control of glucocorticoid secretion
- hypoxia
- hypoglycaemia
- stress
What internal stimuli is involved in the control of glucocorticoid secretion ?
diurnal rhythms
How is the secretion of glucocorticoid stimulated ?
- stimuli affects the hypothalamus
- hypothalamus releases corticotrophin-releasing hormone
- CRH acts on the pituitary gland
- pituitary releases ACTH
- ACTH acts on the adrenal cortex & triggers the release of glucocorticoids
What effect does cortisol have on the immune system ?
immune suppression
What effect does cortisol have on the liver ?
gluco-neogenesis
What effect does cortisol have on muscle ?
protein catabolism
What effect does cortisol have on adipose tissue ?
lipolysis
What is another name for primary adrenal cortical hypofunction ?
Addison’s disease –> acute adrenal insufficiency
What are some clinical features of Addison’s disease ?
lethargy, weakness, weight loss, anorexia, hypotension
What causes Addison’s disease?
- 90% of cases are autoimmune
- remaining 10% can result from ; TB, tumour metastasis, amyloidosis, post adrenalectomy
- withdrawal of glucocorticoids
What is the name of adrenal cortex hyper function the results in excess cortisol?
Cushing’s syndrome
What is the name of adrenal hyperfunciton with results in excess mineralocorticoid ?
Conn’s Syndrome
What causes Conn’s Syndrome?
- adrenal adenoma = 75%
- bilateral hyperplasia of zona glomerulosa
- adrenal carcinoma
What are some clinical features of Conn’s syndrome?
hypertension, muscle weakness, tetany, paresthesia
Define tetany
muscle spasms
Define Paresthesia
abnormal sensation –> tingling or prickling
What are some clinical features of Cushing’s syndrome ?
- moon face
- proximal muscle wasting
- purple striae
- slow healing wounds
What can cause Cushing’s disease?
- antieror pituitary tumour creating excess ATCH –> Excess glucocorticoid released
- Adrenal carcinoma or adenoma
- ectopic ACTH - usually produced by a tumour located elsewhere
- iatrogenic cushings = too much glucocorticoids being taken (medication)
What are Catecholamines?
adrenaline and noradrenaline
What do catecholamines influence ?
- BP
- cardiac output
- fuel metabolism
- sweating
- pupil size
What are the metabolic effects of adrenaline?
- increase glycogen breakdown
- gluconeogenesis
- lipolysis
- increase release of amino acids, lactate & pyruvate
What is Pheochromocytoma ?
- adrenal medulla hyperfunction
- catecholamine secreting tumour
What are some clinical features of pheochromocytoma ?
- hypertension
- vasomotor signs
What are vasomotor signs ?
anxiety, sweating, palpitations, tremors and abdominal pain
