Endocrine Flashcards
Where is the hypothalamus located
In the anterior end of the diencephalon
What are the direct links between the hypothalamus and the anterior pituitary gland
The vascular links of the hypothalamic – hypophyseal portal system
How is secretion of the posterior pituitary controlled
By nerve signals that originate in the hypothalamus
Name six hormones released from the hypothalamus
Corticotropin releasing hormone (CRH)
Growth hormone releasing hormone (GHRH)
Thyrotrophin releasing hormone (TRH)
Gonadotrophin releasing hormone (GnRH)
Growth hormone release inhibiting hormone/somatostatin
Dopamine
What is another name for the anterior pituitary
What does it consist of
Adenohypophysis
Glandular epithelial tissue
What hormones do we need to know that are secreted from the anterior pituitary
Growth hormone, prolactin, adrenocorticotrophic hormone, thyroid stimulating hormone follicle stimulating hormone luteinising hormone
What secretes GH
Somatotrophs (about 50% of bulk of anterior pituitary)
What secretes prolactin
Lactotrophs– 20% of anterior pituitary but this increases during pregnancy
What secretes ACTH
How much of the anterior pituitary does this take up
Corticotrophs
20%
What secretes TSH
Thyrotrophs (5% of anterior pituitary)
What secretes FSH and LH
How much of the anterior pituitary does this take up
Gonadotrophs
5%
What does pars distalis refer to
The major anterior part of the anterior pituitary
It is separated from the posterior pituitary by the Pars intermedia
What is the pars tuberalis
An upward extension of the anterior pituitary which forms a partial or total collar of cells around the infundibular stem
The pars tuberalis and infundibular stem together make up the pituitary stalk
What is the pars intermedia
A thin area of tissue lying against the posterior pituitary
It is rudimentary in humans compared to other mammals
It secretes MSH
What is MSH
Melanocyte stimulating hormone
What is the pars nervosa
The posterior pituitary or neurohypophysis
How is the posterior pituitary connected to the hypothalamus
Via the pituitary stalk
What are the staining properties of anterior pituitary hormones
Acidophilic: GH, PRL
Basophilic: ACTH, FSH, TSH, LH
Are the neurons of the posterior pituitary myelinated
No
How are the nerves divide in the posterior pituitary
Neurons in the supra optic nuclei are primarily ADH producing
Paraventricular nuclei produce mainly oxytocin
What are the terminal axons from the hypothalamus to the posterior pituitary supported by
Glial cells known as pituitcytes which surround the unmyelinated axons
Discuss The ultrastructure of cells in the anterior pituitary
They are typical of those of a peptide secreting cell
They are characterised by numerous secretory granules in the cytoplasm as well as prominent Golgi apparatus, ER and mitochondria
The Endocrine cells are surrounded by numerous sinusoid capillaries of the pituitary portal system that have penetrated endothelium and carry away secreted hormones
Where is the thyroid located and what does it consist of?
Located in the anterior neck region in front of the upper trachea
It consists of two lateral lobes is connected by a breach of tissue called the isthmus
Where is the pyramidal lobe of the thyroid
Extends up from the isthmus
How many parathyroid glands are there
Usually 4 but this number can vary
What is T4 and T3
T4= thyroxine
T3= triiodothyronine
They are iodine containing hormones synthesised by the follicular cells of the thyroid gland
What are C cells
Parafollicular cells in the thyroid which release calcitonin
What does calcitonin do
Plays a role in calcium regulation
What do the parathyroid glands synthesise
What does it do
Parathyroid hormone (PTH)
Plays a role in calcium And phosphate regulation
What is the functional unit of the thyroid
The thyroid follicle
Describe the structure of a thyroid follicle
Spherical structure is composed of one layer of follicular cells which have a nucleus located at the base of the cell
What do thyroid glands contain
Thousands of follicles filled with colloid
What is the main component of colloid
Thyroglobulin
How common are C cells in the thyroid
They are less common and sparsely distributed sometimes referred to as clear cells
What do you C cells look like
Large, rounded, with a clear and light structure
Where are c cells found
In humans: primarily located within the thyroid follicle between the basal area of the follicular cells and the basement membrane such that they have no contact with the colloid
What do parathyroid glands consist largely of
Chief/principal cells and oxyphil/acidophilic cell
What do chief cells and oxyphil cells do in the parathyroid
Chief cells are responsible for the synthesis and secretion of PTH
Oxyphil cells do not secrete PTH their physiological role is not clear
Oxyphil cells are often absent in which group of people
Young individuals: their number increases with age
Describe the difference in morphology between active follicular cells and less active follicular cells
Active: high and columnar
Less active: flattened
How can the inner adrenal medulla be considered
Name 3 things secreted here
As a sympathetic ganglion in which postganglionic neurons have lost axons and become secretory cells
The catecholamines: adrenaline, noradrenaline and dopamine
What does the zona glomerulosa secrete
Mineralocorticoids, mainly aldosterone
What do the cells of the zona glomerulosa look like
They tend to aggregate into a regular round clusters surrounded by capillaries of wide diameter
The cells have a strongly stained round nucleus and poorly stained cytoplasm
What is the widest zone of the adrenal cortex and what do it cells look like?
What does it secrete?
Zona fasciculata
That consists of narrow cords of large cells, separated by a wide diameter, fenestrated capillaries
Glucocorticoids, mainly cortisol
How much of the adrenal cortex is the zona reticularis
What does it consist of
What does this zone secrete
5-10%
Irregular network of branching cords, with numerous capillaries of wide diameter
Androgenic steroids
How is the adrenal medulla arranged
In clumps and cords of cells known as chromaffin cells surrounded by supporting tissue containing numerous wide diameter, fenestrated capillaries
Describe the Venous channels of the adrenal medulla
They drain blood from the capillaries of the cortex past through the middle that towards the central medullary vein
Describe the cells of the adrenal medulla
Large nucleus and a basophilic cytoplasm
What is released from the adrenal medulla
Catecholamines are stored in membrane-bound granules which are released by exocytosis
In humans and dogs which hormone is released most from the adrenal medulla
What about the cats
Adrenaline
Noradrenaline
