T1 L3 Nuts and bolts of the endocrine system Flashcards
What are the roles of the endocrine system?
Normal growth and development
Adaption to internal and external environment
Contribute to process of sexual reproduction
Describe the structure of endocrine glands
Functional unit consisting of cuboidal secretory cells with a lumen at the centre
Secretory cells supported by myoepithelial cells
Not all functional units have a lumen
What factors influence the effect a hormone will have on a cell’s metabolism?
Number of molecules available
Number of receptors available
Affinity hormone - receptor
What are the classifications of hormones?
Steroid
Protein / peptide
What does endocrine mean?
Action of a hormone on a target organ away from the secreting cell
What does autocrine mean?
Action of the hormone on the secreting cell
What does paracrine mean?
Action of the hormone on the adjacent cell
What does neuroendocrine mean?
Neural stimulation of endocrine cells to secrete hormones e.g. medulla of the adrenal gland
Where is the hypophysis located?
In sella turcica in sphenoid bone
What is the blood supply to the hypophysis?
2 blood vessels branching from internal carotid
Superior hypophyseal
Inferior hypophyseal
What does the superior hypophyseal supply?
Median eminence and upper park of stalk
What does the inferior hypophyseal supply?
Neurohypophysis and lower part of stalk
Describe the pathway of blood flow through the hypophyseal
1) Capillary plexus in median eminence and stalk ending
2) Portal vein
3) Anterior lobe of pituitary
4) Secondary capillary plexus
Describe the size and shape of the thyroid gland
Bilobed gland in the neck
4 x 2cms, 30g
2 lateral lobes connected by isthmus
Where are para-follicular cells or clear (C) cells found?
Between follicles of thyroid tissue
What do C cells do?
Secrete calcitonin which promotes reduction of calcium concentration in the blood
What is the thyroid gland derived from?
Endoderm
Develops as a growth from floor of pharynx near base of tongue
What is the role of the thyroid?
Regulate tissue metabolism
Growth
Development
What is the blood supply to the thyroid gland?
Superior thyroid from external carotid
Inferior thyroid from subclavian
What is the blood drainage from the thyroid?
External plexus into internal jugular vein and brachiocephalic vein
Describe the parathyroid glands
2 superior and 2 inferior embedded in capsule of thyroid
Describe the development of the parathyroid glands
From cells originating from 3/4th pharyngeal pouches
Migrate caudally with thymus
Inferior parathyroids travel further to lie lower compared to superior parathyroids
What is the role of the parathyroid glands?
Secrete parathyroid hormone to regulate calcium and phosphate levels within homeostasis
What happens if the parathyroid glands are removed?
1) Fall in blood calcium levels
2) Muscles (including respiratory and laryngeal) go into titanic contraction
3) Death
What is the blood supply to the parathyroid glands?
Inferior thyroid
Superior thyroid
What is the blood drainage from the parathyroid glands?
Superior thyroid
Middle thyroid
Inferior thyroid
What is the nervous supply to the parathyroid glands?
Middle cervical ganglions
Inferior cervical ganglions
Where are the adrenal glands located?
Superior pole of kidneys
Retroperitoneal
What is the structure of the adrenal glands?
Outer capsule
Cortex
Medulla
Pyramidal and semilunar
What does the cortex of the adrenal glands stem from?
Mesoderm
What does the medulla of the adrenal glands stem from?
Neural crest cells
In the adrenal glands, what do the cells subadjacent to the capsule do?
Secrete mineralocorticoids e.g. aldosterone
Function to maintain electrolyte balance
In the adrenal glands, what do the cells in the deeper part of the cortex do?
Secrete glucocorticoids e.g. hydrocortisone
Affect metabolism and electrolyte balance
What are the 3 distinct zones in the cortex of the adrenal glands?
Zona glomerulose
Zona fasciculata
Zona reticularis
What does the zona glomerulosa secrete?
Mineralocorticoids
Aldosterone
Absorption of sodium
What does the zona fasciculate secrete?
Glucocorticoids
Cortisol and corticosterone
Sex hormones
What does the zona reticularis secrete?
17 ketosteroids
Sex hormones
What are chromaffin cells?
Secretory cells
Develop from same embryonic tissue as sympathetic ganglia
What do the compact cells in the medulla secrete?
Adrenaline
Noradrenaline
What is the blood supply to the adrenal glands?
Superior suprarenal arteries
Middle suprarenal arteries
Inferior suprarenal arteries
Where do the superior suprarenal arteries come from?
Inferior phrenic artery
Where do the middle suprarenal arteries come from?
Aorta
Where do the inferior suprarenal arteries come from?
Renal artery
What is the venous drainage of the right adrenal gland?
Right adrenal vein into the IVC
What is the venous drainage of the left adrenal gland?
Left adrenal vein into renal vein
What do acidophils do?
Take up acidic dyes
What do basophils do?
Take up basic dyes
What hormones do somatotrophy cells produce?
Growth hormone that is taken up by bone
What hormones do lactotroph cells produce?
Prolactin which targets breasts
What hormones do corticotrophy cells produce?
ACTH which targets the adrenal glands
What hormones do gonadotroph cells produce?
FSH which targets the ovary and testis
What hormones do thydrotoph cells produce?
TSH which target the thyroid gland
Describe the pathology of pituitary adenomas
Benign tumours
Arise from anterior lobe
Functional or non-functional
10% of intra-cranial neoplasms
What symptoms are caused by the space occupying effect of adenomas?
Headaches Vomiting Nausea Diplopia Impaired vision
What impact does a lack of iodine have on the thyroid gland
Enlarges (goitre) to absorb the maximum concentration of iodine
Describe Grave’s disease
Hyperthyroid Auto-antibodies stimulate TSH receptors Hyperplasia of thyroid cells leads to diffuse enlargement of thyroid gland Infiltrative opthalmopathy Infiltrative dermopathy
What is infiltrative opthalmopathy?
Accumulation of soft tissue and inflammatory cells behind the eye leading to proptosis
What is infiltrative dermopathy?
Thickening and induration of skin on anterior shin leading to pre-tibial myxoedema
Describe Hashimoto’s disease
Hypothyroid
Autoimmune disease
Progressive depletion of thyroid cells by inflammation leading it to be replaced by fibrosis
What are the results of clinical tests in Hashimoto’s disease?
Decreased T3/T4
Increased TSH
What is the pathologic evidence of Hashimoto’s disease?
Irregular with solid cut surface
Prominent lymphocytic infiltrate
What is a follicular adenoma?
Benign tumour of thyroid follicular cells
What can cause adrenocortical hyperactivity?
Hyperplasia, adenoma or cancer
Cushing’s syndrome - excess cortisol
Conn’s syndrome - excess aldosterone
Adrenogenital syndrome - excess androgens
What can cause adrenocortical insufficiency?
Addison’s disease
What is phaechromocytoma?
Tumour of adrenal medulla
Caused by high levels of catecholamines
What are the consequences of phaechromocytoma?
Increased BP Tachycardia Palpitations Headache Sweating Tremor
What are the consequences of increased BP?
Congestive heart failure
Ischaemic heart disease
Cardiac arrhythmias
Cerebrovascular accident
What is Cushing’s syndrome?
Excess cortisol
What is Conn’s syndrome?
Excess aldosterone
What is Adrenogenital syndrome?
Excess androgens
