ANATOMY AND PHYSIOLOGY - Adrenal Glands Flashcards
Which structure surrounds the adrenal glands?
Fibrous capsule
What are the two main layers of the adrenal gland?
Cortex and Medulla
Which arteries make up the subcapsular plexus located just under the fibrous capsule of the adrenal glands?
The superior, middle and inferior branches of the renal artery make up the subcapsular plexus
What is the difference between the cortical arterioles and the long cortical arterioles?
The cortical arterioles branch from the subcapsular plexus and branch into capillary beds within the cortex, long cortical arterioles branch from the subcapsular plexus and branch into capillary beds within the medulla
Which veins drain the adrenal glands?
Central medullary vein drains into the caudal vena cava or the renal vein
What is the embryological origin of the adrenal cortex?
The adrenal cortex has a mesodermal origin
What is the main function of the adrenal cortex?
Steroid hormone synthesis and secretion
What are the three zones of the adrenal cortex?
Zona glomerulosa
Zona fasciculata
Zona reticularis
Which of the three zones of the adrenal cortex can change size depending on the physiological conditions?
Zona reticularis can change in size depending on the physiological conditions
Which hormone stimulates the beginning of steroid hormone synthesis in the adrenal cortex?
Adrenocorticotropic hormone (ACTH) secreted by the anterior pituitary gland
Which hormones are produced by the zona glomerulosa?
Mineralocorticoids (mainly aldosterone)
What are the cells in the zona glomerulosa which produce mineralocorticoids?
Trabeculae cells
Describe the histological appearance of trabeculae cells
Trabeculae cells are columnar cells with prominent nuclei
List the three physiological changes that stimulate the renin-angiotensin-aldosterone mechanism
Change in blood pressure
Change in sympathetic innervation
Change in Na+ concentration in the filtrate
Describe how the renin-angiotensin-aldosterone mechanism regulates aldosterone secretion from the trabeculae cells
- Decreased blood pressure, increased sympathetic nervous system innervation and/or decreased Na+ concentration in the filtrate stimulates the juxtaglomerular cells to secrete renin
- Renin coverts angiotensin (produced by the liver) into angiotensin I which circulates the body and is converted into angiotensin II in the lungs by the angiotensin conversion enzyme (ACE)
- Angiotensin II stimulates increased aldosterone secretion from the trabeculae cells of the adrenal cortex
What are the main functions of aldosterone?
Regulation of Na+ and K+ secretion from the distal nephron (DCT and collecting ducts) and reabsorption of Na+ into the salivary and sweat glands
What is Hyperaldosteronism (Conn’s Syndrome)?
Hyperaldosteronism (Conn’s Syndrome) is hypersecretion of aldosterone
What can cause primary Hyperaldosteronism (Conn’s Syndrome)?
Primary Hyperaldosteronism (Conn’s Syndrome) can be caused by adrenal tumours which cause hypersecretion of aldosterone from the zona glomerulosa
What can cause secondary Hyperaldosteronism (Conn’s Syndrome)?
Secondary Hyperaldosteronism (Conn’s Syndrome) can be caused by bilateral adrenal hyperplasia
What are six symptoms of Hyperaldosteronism (Conn’s Syndrome)?
Hypokalaemia (decreased plasma K+)
Hypernatraemia (increased plasma Na+)
Metabolic alkalosis
Hypertension
Renal failure
Blindness
What is a symptom of Hyperaldosteronism (Conn’s syndrome) which is specific to cats?
Cervical ventroflexion
Describe the histological appearance of the zona fasciculata
Polyhedral with pale staining cytoplasm
Which hormones are produced by the zona fasciculata?
Glucocorticoids (mainly cortisol/corticosterone)
What is Hyperadrenocorticism (Cushing’s syndrome)?
Hyperadrenocorticism (Cushing’s syndrome) is the hyperseceretion of cortisol
What can cause primary Hyperadrenocorticism (Cushing’s syndrome)?
Adrenal tumours which secrete cortisol independently of adrenocorticotropic hormone (ACTH)
What can cause secondary Hyperadrenocorticism (Cushing’s syndrome)?
Pituitary tumours which cause excess adrenocorticotropic hormone (ACTH) secretion and thus excess cortisol secretion
What are six symptoms of Hyperadrenocorticism (Cushing’s syndrome)?
Polyuria
Polydipsia
Polyphagia
Lethargy
Panting
Recurrent urinary tract infections (UTIs)
What is Latrogenic Cushing’s syndrome?
Latrogenic Cushing’s syndrome is hyperadrenocorticism caused by long term corticosteroid treatment
What is Adrenocortical Insufficiency (Addison’s disease)?
Adrenocortical Insufficiency (Addison’s disease) is inadequate cortisol secretion
The decrease in which steroid hormone (other than cortisol) is often associated with Adrenocortical Insufficiency (Addison’s disease)?
Aldosterone
What can cause primary Adrenocortical Insufficiency (Addison’s disease)?
Adrenal gland defect
Autoimmune disease
What can cause secondary Adrenocortical Insufficiency (Addison’s disease)?
- Pituitary tumours
- Following discontinuation of long term corticosteroid treatment
What is an ‘addisonian crisis’?
An ‘addisonian crisis’ is an episode of acute cortisol insufficiency where the body goes into shock. This is a medical emergency
What are nine symptoms of Adrenocortical Insufficiency (Addison’s disease)?
Lethargy
Vomiting
Diarrhoea
Weight loss
Dehydration
Poor appetite
Polydipsia
Polyuria
Low plasma glucose
Describe the histological appearance of the zona reticularis?
Small cells with strong staining cytoplasm
Which hormones are produced by the zona reticularis?
Androgens
Which three main androgens are produced by the zona reticularis?
Dehydroepiandrosterone (DHEA)
Dehydroepiandrosterone sulphate (DHEAS)
Androstenedione
What is the name of the functional cells within the adrenal medulla?
Chromaffin cells
What is secreted by the chromaffin cells within the adrenal medulla?
Catecholamines (adrenaline, noradrenaline and dopamine)
Describe the histological appearance of the chromaffin cells within the adrenal medulla?
Chromaffin cells are columnar with large nuclei and strong basophilic cytoplasm
What innervates the chromaffin cells within the adrenal medulla?
Sympathetic preganglionic fibres
