1a The Pituitary Gland Flashcards
What is a hormone?
a signalling molecule produced by glands that are transported in the bloodstream to target distant organs
What are peptide hormones synthesized as?
Prohormones
How are steroid hormones synthesized?
In a series of reactions from cholesterol
What is meant by constitutive secretion?
Released as soon as they are produced
Which type of hormone shows constitutive secretion?
Steroid hormones
Which hormones is secreted by regulatory secretion?
Peptide hormones
What is regulatory secretion?
When the hormones is stored in a vesicle and has to be triggered to be released
What is the difference in peptide and steroid hormones in terms of receptors?
Peptide hormones bind receptors on cell membranes and induce a signal via a secondary messenger system
Steroid hormones bind to intracellular receptors to change gene expression directly
What has to hapen to peptide hormones in order for them to be activated?
The pro hormone which is initially secreted has to be cleaved
What is the name of the bone which the pituitary gland sits in?
Sella tursica of sphenoid bone
What is the name of the posterior pituitary?
Pars nervosa
What are the three parts of the anterior pituitary?
Pars tuberalis
Pars intermedia
Pars distalis
What is directly above the pituitary?
The hypothalamus
What is the median eminence?
part of the posterior pituitary which has a blood supply in common with the anterior pituitary
What vascularises the anterior pituitary?
The hypothalamic-pituitary portal system
What regulates anterior pituitary function?
Hypothalamic Parvocellular neurones
Where do hypothalamic parvocellular neurones terminate?
The medial eminence
What length are hypothalamic parvocellular neurones?
Short
What do the hypothalamic parvocellular neurones release and into where?
Release hypothalamic releasing / inhibiting hormones into the capillary plexus of median eminence
what is special about the capillary plexus in the medial eminence?
They are leaky meaning so the hormone factors can enter into the hypothalamic-pituitary portal system
What is the name of the anterior pituitary?
Adenohypophysis
What is the adenohypophysis derived from?
The Rathke Pouch
What are the 5 types of endocrine cells found in the anterior pituitary?
Somatotrophs
Gonadotrophs
Corticotrophs
Lactotrophs
Thyrotrophs
Describe the hypothalamo-pituitary portal system
- Hypothalamic neurosecretory cells terminate at the medial eminence
- Release hypothalamic releasing / inhibiting factors into the capillary plexus
- The capillary plexus of median eminence is leaky, meaning these factors are able to enter into the portal circulation to the anterior pituitary
- These releasing or inhibiting hormones stimulate the release of hormones from anterior pituitary cells
- The hormones leave the gland via the blood
What do somatotrophs secrete?
Growth hormone (somatotrophin)
What do gonadotrophs secrete?
LH and FSH