Endocrine Flashcards
2 parts of pituitary gland
Anterior and posterior
Origin of posterior pituitary
Neuronal origin
Down-growth of the brain
What attaches the posterior pituitary to the brain
Pituitary stalk to the median eminence of the midbrain in the floor of the third ventricle
Where is the posterior pituitary attached to the brain
Median eminence of midbrain in the floor of the third ventricle
Which hormones does the posterior pituitary secrete
Vasopressin (ADH)
Oxytocin
What does the posterior pituitary contain
Nerve endings of axons whose cell bodies lie in the supraoptic and para-ventricular nuclei of hypothalamus
Origin of anterior pituitary
Epithelial in origin
Derived from roof of primitive gut tube
Adherence of anterior pituitary
Adheres to anterior border of posterior pituitary
Surrounds the pituitary stalk (pars tuberails)
What regulates the release of trophic hormones from the anterior pituitary gland
Releasing or inhibiting factors produced by neurons of the hypothalamus
How does the hypothalamus communicate with the anterior pituitary gland
Pituitary portal system
3 sub groups of cells in the anterior pituitary
Alpha cells/acidophils
Beta cells/basophils
Chromophobes
Which cells stain weakly with either type of dye
Chromophobes
Which cells fail to stain
Immature cells without granules
Which cells stain heavily with acid dyes
Alpha cells/ acidophils
Which cells stain heavily with basic dyes
Beta cells/ basophils
5 main classes of cell in anterior pituitary
Somatotrophs
Lactotrophs
Corticotrophs
Thyrotrophs
Gonadotrophs
What do Somatotrophs secrete
Growth hormone
What do Lactotrophs secrete
Prolactin
What do Corticotrophs secrete
Adrenocorticotropin hormone
What do Thyrotrophs secrete
Thyroid stimulating hormone
What do Gonadotrophs secrete
Follicle stimulating hormone
Luteinising hormome
Staining the posterior pituitary
Stains palely with H&E in routine wax embedded tissue
Herring bodies
Swollen nerve terminals containing dark staining neuro-secretory granules
Neurophysin
Carrier protein in posterior pituitary that binds to ADH or oxytocin
Adenohypophysis
Anterior pituitary - epithelial origin
Neurohypophysis
Posterior pituitary- neuronal origin
What colour do neuro-secretory granules (I.e. posterior pituitary) stain
Brown
Pars tuberalis
An upward extension of the anterior pituitary that surrounds the pituitary stalk to form the tuberal lobe
Contains mostly gonadotrophic cells
Which cell type is mostly found in the pars tuberalis
Gonadotrophic
Intermediate lobe
Lies between the anterior and posterior pituitary
Contains cyst-like aggregations of colloidal material
Pineal gland location
Backward projection from the 3rd ventricle below the corpus callosum
Covered by meninges
Function of pineal gland
Secretes melatonin
Function of melatonin
Regulator of diurnal rhythm
Innervation of pineal gland
Autonomic
Structure of pineal gland
Irregular clumps of neuron-like pinealocytes linked by glial cells
Calcium accumulates as particles in its capsule
Why does the pineal gland appear radio opaque and visible on x-rays
Calcium accumulates as particles in its capsule
Location of thyroid gland
Arises from floor of the mouth (stomatodeum)
Descends during development to lie in neck between the level of the thyroid cartilage superiorly and the 4th tracheal ring inferiorly
Structure of thyroid gland
2 lobes joined in the mid-line by an isthmus
Function of thyroid gland
Synthesises, stores and secretes thyroxine and calcitonin
Where are the parathyroid glands located
Embedded in posterior border of each lobe of thyroid gland
What links the thyroid gland to the Foramen caecum of the tongue
Midline thyroglossal ligament
Thyroid follicles
Form a single layered cuboidal epithelium surrounded by a basement membrane
Centre of each follicle is filled with amorphous colloid rich in thyroglobulin
Height of cells depends on metabolic activity
Thyroglobulin
Inert stored form of thyroxine hormone
First thyroid follicle phase- synthetic phase
Synthesis of thyroglobulin and store it within the follicle (upper panel)
2nd phase of thyroid follicle
Dormant period
3rd phase of thyroid follicle- resorbtive phase
Cells re-absorb and breakdown the colloid releasing the active hormone, mainly T4 (tetraiodothyronine), into the bloodstream (lower panel)
Characteristics of thyroid follicles in active phase
Cells enlarge and appear columnar in shape
Characteristics of thyroid follicles in dormant phase
Loose some organelles
More stored colloid
Low cuboidal profile
Where are C cells located
Thyroid gland
In clumps between the follicles (parafollicular cells)- some occur singly, trapped between the basement membrane and epithelial cells of the follicle
Function of C cells
Produce calcitonin
Composition of parathyroid glands
A mixture of fat cells (adipocytes) and secretory cells
Secretory cells of parathyroid gland structure
Arranged in clusters or short cords
Main type of secretory cells in parathyroid gland
Chief cells
Structure of chief cells
10um in diameter
Palely stained
Contain large numbers of very small granules
Types of secretory cells in parathyroid gland
Chief cells
Oxyphil cells
Oxyphil cells
Larger pink-staining
Fewer numbers than chief cells
Role is uncertain
Pancreatic islets of Langerhans
Small spherical masses of endocrine cells embedded throughout the exocrine pancreas
Constitute about 5% of the mass of the gland
Most numerous at the tail
Where are pancreatic islets of Langerhans most numerous in the pancreas
Tail
Number of cell types in islets of Langerhans
5
5 secretory cell types in islets of Langerhans
Insulin secreting beta cells
Glucagon secreting alpha cells
Somatostatin secreting delta cells
Pancreatic polypeptide secreting cells
Ghrelin secreting cells
What percentage of the islets of Langerhans is made up of insulin secreting beta cells
70%
What percentage of the islets of Langerhans is made up of glucagon secreting alpha cells
20%
What percentage of the islets of Langerhans is made up of somatostatin secreting delta cells
8%
What percentage of the islets of Langerhans is made up of pancreatic polypeptide secreting cells
2%
What percentage of the islets of Langerhans is made up of ghrelin secreting cells
<1%
What is required to differentiate between types of secretory cells in the islets of Langerhans
Immunohistochemical staining
What colour do the islets of Langerhans stain
Pale
Which cells are mostly distributed around the periphery of the islets of Langerhans
Beta cells
Distribution of beta cells
Mainly around the periphery of the islets and form anastomosing cords that penetrate to the centre of the
Location of adrenal glands
In the abdomen superior to the kidney
Enclosed within renal fascia
Structure of adrenal glands
Outer cortex
Inner medulla
Centripetal blood supply to adrenal gland
Arterioles from the capsular arteries supply the cortical sinusoids and provide direct links to the medulla (medullary arterioles)
Both systems drain into the same central vein that carries the mixed cortical and medullary hormones to the renal vein (left) or IVC (right)
3 zones of adrenal cortex
Outer glomerular zone
Intermediate fascicular zone
Inner reticular zone
Outer glomerular zone of adrenal gland
Narrow
Rounded clumps of cell
Produces aldosterone and other mineralocorticoids
Intermediate fascicular zone of adrenal gland
Thick
Long parallel cords of cells
Produce cortisol and other glucocorticoids
Inner reticular zone of adrenal gland
Anastomosing cords of cells
Produce testosterone and other androgenic hormones
Where are the hormones produced by the adrenal cortex stored
Sinusoids that run between the cords of cells
Why are the secretory cells of the adrenal cortex pale staining
Accumulate droplets of fat and cholesterol from the hormones that are synthesised
Structure of adrenal medulla
Irregular clumps of cells interspersed by blood vessels
2 types of secretory cells in adrenal medulla
- Synthesise and secrete adrenaline
- Secrete noradrenaline
Are the hormones in the adrenal cortex stored
No- discharge into sinusoids that run between the cords of cells as soon as produced
Are the hormones synthesised in the adrenal medulla stored
Yes- in small neurosecretory granules within the cytoplasm of cells until required
What influences cells of the adrenal medulla
Steroid hormones produced by the adrenal cortex in the blood that bathes the cells
Autonomic (mainly sympathetic) innervation
Central vein in adrenal medulla
Large vein
Thickened by bundles of smooth muscle fibres that run parallel to the vein, foreshortening it and helping to keep it open
Other hormone secreting tissues
Ovary
Testis
Placenta
Locations of isolated clumps of neuro-endocrine cells
Epithelium of the gut
Respiratory tract
Paraganglia
Carotid bodies
What do acidophils secrete
Growth hormone
Prolactin
What do basophils secrete
Thyrotrophs
Corticotrophs
Gonadotrophs
From which brain nuclei do the neurons that give rise to herring bodies originate
Supraoptic and paraventricular nuclei in the walls of the third ventricle and receive input from the hypothalamus
What stimulates calcitonin secretion
High blood calcium
Action of calcitonin
Lowers serum calcium by promoting the uptake of calcium in the blood particularly into bones and muscles
Inhibits absorption of calcium from the gut and reabsorption of calcium in the kidney
What hormone has an antagonist action to calcitonin
Parathormone
Action of oxytocin on the uterus
Contraction of muscles of uterus
Dilation of birth canal
Action of oxytocin on breasts
Contraction of smooth muscle in nipple causing it to become erect
Contraction of myoepithelial cells of secretory alveoli aiding expression of milk
What hormone do chief cells produce
Parathormone
Action of parathormone
Mobilisation of calcium mainly from the bones
Which hormone secreting glands are derived directly from the primitive gut tube
Anterior pituitary
Thyroid
Parathyroid glands
Endocrine pancreas
Where are Catecholamines produced
Chromaffin cells of adrenal medulla
Post ganglionic fibre of sympathetic nervous system
Cells of adrenal medulla are derived from 2 distinct embryonic primordia - what are they
Modified postganglionic axons of sympathetic nervous system
Derived from neural crest
Synthesise melanin and small granules can be seen in the cytoplasm
All endocrine organs are composed of glandular epithelium apart from….
Posterior pituitary
What percentage of cells in the anterior pituitary are somatotrophs
50%
What percentage of cells in the anterior pituitary are Lactotrophs
25%
What percentage of cells in the anterior pituitary are Corticotrophs
15-20%
What percentage of cells in the anterior pituitary are Gonadotrophs
10%
What percentage of cells in the anterior pituitary are Thyrotrophs
1%
Where are somatotrophs predominantly found in the anterior pituitary
Lateral wings
Present throughout
Lactotrophs structure
Polygonal cells
Cytoplasmic processes wrap around other cells
Variable prolactin staining
Thyrotrophs structure
Angular Chromophobes
Elongated cytoplasmic processes
Variable TSH staining
Gonadotrophs structure
Scattered round/oval cells
Stain with either:
Alpha subunits
Beta LH
beta FSH
Corticotrophs structure
Round basophilic cells
Median of gland
Large cytoplasmic vacuoles- enigmatic bodies
What supports pituicytes in the anterior pituitary
Sustentacular cells
Surrounds the normal follicles
Stains with S100
Pituitary adenoma
Benign tumour of pituitary
Structure of pinealocytes
Eosinophilic cytoplasm
Central rounded nuclei
Arranged in rosettes
Parathyroid chief cell structure
Polygonal cells
Scant cytoplasm
How to determine between parathyroid and thyroid tissue
Parathyroid= no calcium oxalate crystals
Parathyroid Oxyphil cell structure
Large polygonal cells
Increase with age
Abundant eosinophilic cytoplasm
Finely granular- rich in mitochondria
Number of islets of Langerhans in pancreas
Approximately 1 million
What secretes adrenaline and noradrenaline
Chromaffin cells
Which statement concerning endocrine organs is true?
All have a rich vascular supply
Which are the least common cells in the anterior pituitary?
Thyrotrophs
Which are the most common cells in the anterior pituitary?
Somatotrophs
Parathyroid chief cells…
Have scanty cytoplasm
Which gland contains fat cells
Parathyroid glands
The adrenal zona fasciculata principally secretes
Cortisol
Which hormones are produced by the islets of Langerhans
Insulin
Glucagon
Somatostatin
Pancreatic polypeptide
Ghrelin
Which endocrine organ receives its blood supply through a portal circulation?
Anterior pituitary
What hormones are produced by arachidonic acid
Prostaglandins
What is produced from glutamic acid
Histamine
What is produced from tryptophan
Melatonin
What is produced from cholesterol
Adrenal cortical hormones (steroid)
What is produced from tyrosine
Thyroxine
Catecholamines
Peptide
