[ENDO] PITUITARY GLAND-2.pdf

~600 mg

What is the approximate weight of an adult pituitary gland?

400-900 mg

What is the range of adult pituitary gland weight?

~13 mm

What is the approximate longest transverse diameter of the pituitary gland?

6-9 mm

What is the vertical height range of the pituitary gland?

9 mm

What is the anteroposterior dimension of the pituitary gland?

4th-5th week

At what gestational age does Rathke's pouch form?

Anterior pituitary origin

What is the origin of Rathke's pouch?

15-25%

What percentage of cells in the anterior pituitary are lactotrophs?

1

How many G-protein-coupled receptor families do dopamine receptors belong to?

2

How many types of dopamine receptors are located on lactotroph cells?

4-20 ng/mL

What are the normal prolactin concentrations in non-pregnant, non-lactating women?

Lower

Are prolactin concentrations in men generally higher or lower than in non-pregnant, non-lactating women?

100-200 ng/mL

What are the typical prolactin concentrations during late pregnancy and lactation?

7 days

How long postpartum does prolactin secretion take to decrease without continuous nipple stimulation?

191

How many amino acids are in a growth hormone molecule?

22,005 Da

What is the molecular weight of growth hormone?

35-45%

What percentage of functional pituitary cells are somatotrophs?

2

How many pre-dimerized GH receptor (GHR) components does GH complex with?

20 hours

What is the half-life of IGF-1 in the blood?

20 minutes

What is the half-life of GH in the blood?

1%

What percentage change in osmolality is plasma vasopressin sensitive to?

10-15%

What percentage change is required in blood volume or pressure for a significant response in plasma vasopressin?

280-295 mOsm/kg H2O

What is the normal range of plasma osmolality maintained by osmoreceptors?

Base of the skull

Where is the pituitary gland located at its base?

Sella turcica (bony)

What bony structure at the base of the skull houses the pituitary gland?

Thin bony roof of the sphenoid sinus

What structure forms the bony roof at the base of the skull near the pituitary gland?

Cavernous sinus

What primarily comprises the lateral walls of the pituitary gland's location?

3rd, 4th, 6th cranial nerves, internal carotid artery (ICA)

What key structures are located within the cavernous sinus adjacent to the pituitary gland?

Superiorly to the pituitary stalk

Where is the roof of the pituitary gland's location situated?

Optic chiasm

What key structure is located anterior to the pituitary stalk, superiorly to the pituitary gland?

Diaphragma sella

What structure is located directly below the optic chiasm, superiorly to the pituitary gland?

Superior hypophyseal

Which artery primarily supplies the hypothalamus and anterior pituitary gland?

Branches from the ICA

What is the origin of the superior hypophyseal artery?

Hypothalamic-portal circulation

What significant circulatory system does the superior hypophyseal artery contribute to in relation to the pituitary gland?

Inferior hypophyseal

Which artery provides systemic arterial supply to the posterior pituitary gland?

Branch of posterior communicating artery and ICA

What is the origin of the inferior hypophyseal artery?

Posterior pituitary gland

Which part of the pituitary gland has a systemic arterial supply via the inferior hypophyseal artery?

Metastases more common

What is a potential implication of the systemic arterial supply to the pituitary gland?

Hypothalamic neurons

What is the origin of the hormones in the hypophyseal portal circulation?

Releasing and inhibiting hormones

What type of hormones are transported in the hypophyseal portal circulation?

Control anterior pituitary hormone secretion

What is the function of the hormones transported in the hypophyseal portal circulation?

Different parts of hypothalamus

Where do the neurons that contribute to the hypophyseal portal circulation originate?

Nerve fibers to median eminence, pituitary stalk

Where do the axons of the hypothalamic neurons in the portal system project to?

Absorbed into portal system

How are hypothalamic hormones transported to the anterior pituitary gland?

Carried to anterior pituitary gland

Where are the hypothalamic hormones transported after being absorbed into the portal system?

Act on anterior pituitary cells

What is the effect of the transported hypothalamic hormones?

Predominantly hypothalamic to pituitary

What is the primary direction of blood flow in the hypophyseal portal circulation?

High concentration of hypothalamic hormones at the anterior pituitary

What is the significance of the predominantly hypothalamic to pituitary blood flow?

Fenestrated

What is a key feature of the vessels in the hypophyseal portal circulation?

Allows diffusion of peptide/releasing factors to sites of action

What is the functional significance of the fenestrated vessels?

Quick and direct communication between hypothalamus and anterior pituitary

What does the hypophyseal portal circulation enable?

External to blood brain barrier

Where is the barrier of the hypophyseal portal circulation located relative to the blood-brain barrier?

Rathke's pouch

What is the embryonic origin of the anterior pituitary lobe (adenohypophysis)?

Hypothalamus (neural)

What is the embryonic origin of the posterior pituitary lobe (neurohypophysis)?

Glandular

What type of tissue characterizes the anterior pituitary lobe?

Neural

What type of tissue characterizes the posterior pituitary lobe?

Hypothalamic releasing/inhibiting hormones

What primarily controls hormone secretion from the anterior pituitary lobe?

Direct nerve innervation from hypothalamus

What primarily controls hormone secretion from the posterior pituitary lobe?

Superior hypophyseal arteries & portal system

What is the main blood supply to the anterior pituitary lobe?

Inferior hypophyseal arteries

What is the main blood supply to the posterior pituitary lobe?

Pituitary cells

Where are the hormones of the anterior pituitary synthesized?

Hypothalamus (stored/released)

Where are the hormones of the posterior pituitary synthesized?

Supraopticohypophyseal and tuberohypophyseal

Name the nerve tracts that innervate the posterior pituitary gland.

Extend from hypothalamus to posterior pituitary

Where do these nerve tracts extend from and to?

Directly innervate the posterior pituitary gland

What is the function of these nerve tracts in relation to the posterior pituitary?

ADH, Oxytocin

Name the two main hormones associated with the posterior pituitary gland that are NOT synthesized there.

Cell bodies in hypothalamus (supraoptic and paraventricular nuclei)

Where are the cell bodies that produce ADH and Oxytocin located?

Transported within axons of nerve fibers

How are ADH and Oxytocin transported from their site of synthesis to the posterior pituitary?

From hypothalamus to posterior pituitary gland

What is the direction of this transport?

Carry hormones for storage and release

What is the purpose of this transport?

Neurosecretory granules

Where are ADH and Oxytocin stored in the posterior pituitary gland?

Axon terminals in posterior pituitary gland

Specifically, where in the posterior pituitary are these hormones stored?

Ready for release upon stimulation

What is the state of the stored hormones in the posterior pituitary?

Secreted from axon endings

Where are ADH and Oxytocin released from?

In the posterior pituitary gland

Where does the release of these hormones occur?

Released into the bloodstream when stimulated

How are ADH and Oxytocin delivered to their target tissues?

Direct neural connection to the hypothalamus

What type of connection does the posterior pituitary have with the hypothalamus?

Rapid release of hormones in response to nervous system signals

What does this hypothalamic connection allow for?

Electrically excitable

What is a key characteristic of neurons in terms of excitability?

Not primarily electrically excitable

What is a key characteristic of endocrine cells in terms of excitability?

Electrically excitable

What is a key characteristic of neurohumoral cells in terms of excitability?

Via synapses with other neurons

How do neurons primarily communicate?

Releases hormones to bloodstream

How do typical endocrine cells communicate with target cells?

Axon terminals lack classic synapses

What is a distinguishing feature of neurohumoral cell communication at their output?

Receives signals via dendrites

How do neurons typically receive signals?

Responds to hormones or other signals

How do typical endocrine cells receive signals?

Receives signals via dendrites

How do neurohumoral cells typically receive signals?

Transmits electrical/chemical signals to neurons

What is the primary output of a neuron?

Secretes hormones into bloodstream

What is the primary output of a typical endocrine cell?

Secretes hypothalamic releasing/inhibiting hormones into tissue fluid

What is the primary output of a neurohumoral cell?

Other neurons

What are the primary targets of neurons?

Target cells via bloodstream

What are the primary targets of typical endocrine cells?

Anterior pituitary gland via tissue fluid

What is the primary target of neurohumoral cells in the hypothalamus?

Neurohumoral cells secrete hormones

What is the relationship between neurons and hormone secretion in the hypothalamus?

Releases hormones

What is the general relationship between endocrine cells and hormones?

Synthesizes and secretes regulatory hormones

What is the hormonal role of neurohumoral cells in the hypothalamus?

Magnocellular neurons of hypothalamus

Give an example of a neurohumoral cell.

Lactotroph cells

What type of anterior pituitary cell secretes Prolactin (PRL)?

Dopamine (inhibitory)

What is the primary hypothalamic control over prolactin secretion?

Breast

What is a primary target organ of prolactin?