The Pituitary Gland Flashcards
Describe the properties of the pituitary gland
- Not part of brain!
- Also referred to as hypophysis
- Acts as second in command to hypothalamus
Label the main regions of the pituitary gland
The pituitary gland has two connections with the hypothalamus.
What are they?
Direct - neuronal connection via the infundibulum (posterior pituitory)
Indirect - portal blood vessels (anterior pituitary)
How is the hypothalmus intimately linked to the hypothalamus?
In the embryo, they effectively merge because the hypothalamus grows downwards and the pharynx grows upwards and these two growths form the pituitary gland
- Hypothalamus (downward growth) forms Prosterior pituitary
- Pharynx (upward growth) forms Anterior pituitary
Posterior pituitary mainly neuronal tissue (axons and neurones that link to the paraventricular nucleus, PVN and supraoptic nucleus, SON)
Anterior pituitary is mainly endocrine cells
Explain blood supply to the pituitary
- The blood supply to the pituitary is massively important to its function
- The anterior pituitary (AP) receives blood after it has been through the hypothalamus
- The blood drains into the hypothalamic-hypophysial portal system and runs down the infundibulum and releases into the AP
- Releasing hormones from the hypothalamus can therefore enter the AP before they enter general circulation
- Hormones secreted by the pituitary are then taken away into the venous return
TRUE or FALSE: The posterior and anterior pituitary have the same blood supply
• The posterior lobe has a separate blood supply and drainage
NB – there are a small number of blood vessels that pass from PP through AP and into the hypothalamus forming a feedback loop
Explain how hormones released from the hypothalmus control the release of pituitary hormones
- Hypophysiotropic hormones (releasing hormones and inhibiting hormones) produced by neurosecretory neurons in the hypo- thalamus enter the hypothalamic capillaries.
- These hypothalamic capillaries rejoin to form the hypothalamic–hypophyseal portal system, a vascular link to the anterior pituitary.
- The portal system branches into the capillaries of the anterior pituitary.
- The hypophysiotropic hormones, which leave the blood across the anterior pituitary capillaries, control the release of anterior pituitary hormones.
- When stimulated by the appropriate hypothalamic releasing hormone, the anterior pituitary secretes a given hormone into these capillaries
- The anterior pituitary capillaries rejoin to form a vein, through which the anterior pituitary hormones leave for ultimate dis- tribution throughout the body by the systemic circulation.
Draw a diagram to show anterior pituitary hormones and the feedback loops they are involved in/ effects they mediate
Draw a diagram to show prosterior pituitary hormones and the effects they mediate
- The paraventricular and supraoptic nuclei both contain neurons that produce vasopressin and oxytocin. The hormone, either vasopressin or oxytocin depending on the neuron, is synthesized in the neuronal cell body in the hypothalamus.
- The hormone travels down the axon to be stored in the neuronal terminals within the posterior pituitary.
- When the neuron is excited, the stored hormone is released from the terminals into the systemic blood for distribution throughout the body.
List the anterior pituitary hormones
- ACTH
- TSH
- LH
- FSH
- GH
- Prolactin
List the posterior pituitary hormones
- Oxytocin
- Vasopressin
These hormones are produced in the hypothalamus and passed down into the posterior pituitary
Draw a diagram to show the different stimuli that cause the hypothalamus to stimulate hormone release from the posterior pituitary
Draw a table to show the different posterior pituitary hormones, their targets and their effects
Draw a table to show the different anterior pituitary hormones, their targets and their effects
