In this note, we’re going to explore the anatomy and function of the pituitary gland, also known as the hypophysis.
It’s a key endocrine gland in our body and is intricately connected both structurally and functionally with the hypothalamus, forming the hypothalamic-pituitary system.
The pituitary gland is responsible for producing a wide array of hormones. These hormones play crucial roles in regulating various aspects of our functions, including metabolism, growth, sexual functions, blood pressure, and much more.
Anatomy of the pituitary gland
The pituitary gland is located in the hypophyseal fossa (fossa hypophysialis) within the sella turcica of the sphenoid bone.
It is covered from above by the diaphragma sellae, which is formed by the dura mater.
Adjacent to the gland in front and slightly below is the sphenoidal sinus (sinus sphenoidalis),
in front and above is the optic chiasm (chiasma opticum),
and laterally lies the cavernous sinus (sinus cavernosus).
The pituitary gland is connected to the hypothalamus by the infundibulum,
which forms the pituitary stalk (truncus infundibularis).
The pituitary gland consists of two lobes:
The anterior lobe (lobus anterior) or anterior pituitary, or adenohypophysis, which produces several hormones under the influence of the hypothalamus.
The posterior lobe (lobus posterior) or posterior pituitary, or neurohypophysis, which releases hormones into the blood that were initially produced by the hypothalamus.
Sometimes, a small middle section, or intermediate lobe, is also identified.
Within the infundibulum, there are two systems that provide interaction between the pituitary gland and the hypothalamus.
The first system is the pituitary portal system, which consists of blood vessels connecting the anterior pituitary (adenohypophysis) and the hypothalamus. This system starts with the superior hypophyseal artery, a branch of the internal carotid artery.
It travels to the median eminence of the hypothalamus, forming the primary capillary network.
From this network, hypophyseal portal veins extend out, creating a secondary capillary network, and from there, blood flows into the general bloodstream.
The second system is the hypothalamo-hypophyseal tract, which is made up of nerve fibers connecting the posterior pituitary (neurohypophysis) and the hypothalamus.
Pituitary hormones
Let’s delve into the hormones of the pituitary gland in more detail.
Ok, the first one is the posterior lobe. As previously mentioned, it doesn’t directly produce hormones, but releases into the bloodstream substances that come from the hypothalamus via the hypothalamo-hypophyseal tract.
- These include the antidiuretic hormone (ADH or vasopressin), which is produced in the supraoptic nucleus of the hypothalamus
- And oxytocin, which is produced in the paraventricular nucleus
The diagram illustrates the impacts of these hormones.
Now, let’s move on to the anterior lobe. Here, the synthesis of hormones is controlled by the hypothalamus using so-called releasing factors, which stimulate the adenohypophysis, as well as statins, which, conversely, slow down hormone production.
The hormones of the anterior pituitary include:
- Growth hormone (somatotropin)
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Lipotropic hormone (lipotropin)
- Prolactin
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
The last two, FSH and LH, are collectively referred to as gonadotropins.
The effects caused by these hormones you can see in the diagram.
Pituitary gland
- pituitary gland
- hypophysis
- pituitary fossa
- fossa hypophysialis
- sellar diaphragm
- diaphragma sellae
- sphenoidal sinus
- sinus sphenoidalis
- optic chiasm
- chiasma opticum
- cavernous sinus
- sinus cavernosus
- infundibulum
- infundibulum
- infundibular stalk
- truncus infundibularis
- anterior lobe / adenohypophysis
- lobus anterior
- posterior lobe / neurohypophysis
- lobus posterior
- intermediate lobe / middle part
- pars intermedia
- superior hypophyseal artery
- a. hypophysialis superior
- hypothalamohypophyseal tract
- tractus hypothalamohypophysialis
