Pituitary gland

Pituitary glandAnatomy and function of the pituitary gland. Adenohypophysis. Neurohypophysis. Pituitary hormones
~ 6 min

In this note, we’re going to explore the anatomy and function of the pituitary gland, also known as the hypophysis.

Pituitary gland (hypophysis)
Pituitary gland (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.

Pituitary gland in the hypothalamic-pituitary system
Pituitary gland in 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.

Hypophyseal fossa (fossa hypophysialis)
Hypophyseal fossa (fossa hypophysialis)
Hypophyseal fossa (fossa hypophysialis)
Hypophyseal fossa (fossa hypophysialis)
Hypophyseal fossa (fossa hypophysialis)
Hypophyseal fossa (fossa hypophysialis)

It is covered from above by the diaphragma sellae, which is formed by the dura mater.

Diaphragma sellae (diaphragma sellae)
Diaphragma sellae (diaphragma sellae)

Adjacent to the gland in front and slightly below is the sphenoidal sinus (sinus sphenoidalis),

Sphenoidal sinus (sinus sphenoidalis)
Sphenoidal sinus (sinus sphenoidalis)

in front and above is the optic chiasm (chiasma opticum),

Optic chiasm (chiasma opticum)
Optic chiasm (chiasma opticum)
Optic chiasm (chiasma opticum)
Optic chiasm (chiasma opticum)

and laterally lies the cavernous sinus (sinus cavernosus).

Cavernous sinus (sinus cavernosus)
Cavernous sinus (sinus cavernosus)
Cavernous sinus (sinus cavernosus)
Cavernous sinus (sinus cavernosus)

The pituitary gland is connected to the hypothalamus by the infundibulum,

Infundibulum (infundibulum)
Infundibulum (infundibulum)
Infundibulum (infundibulum)
Infundibulum (infundibulum)

which forms the pituitary stalk (truncus infundibularis).

Pituitary stalk (truncus infundibularis)
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.

Anterior pituitary (lobus anterior)
Anterior pituitary (lobus anterior)

The posterior lobe (lobus posterior) or posterior pituitary, or neurohypophysis, which releases hormones into the blood that were initially produced by the hypothalamus.

Posterior pituitary (lobus posterior)
Posterior pituitary (lobus posterior)

Sometimes, a small middle section, or intermediate lobe, is also identified.

Middle section / intermediate lobe (pars intermedia)
Middle section / intermediate lobe (pars intermedia)

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.

Superior hypophyseal artery (a. hypophysialis superior)
Superior hypophyseal artery (a. hypophysialis superior)

It travels to the median eminence of the hypothalamus, forming the primary capillary network.

Primary capillary network
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.

Secondary capillary network
Secondary capillary network

The second system is the hypothalamo-hypophyseal tract, which is made up of nerve fibers connecting the posterior pituitary (neurohypophysis) and the hypothalamus.

Hypothalamo-hypophyseal tract (tractus hypothalamohypophysialis)
Hypothalamo-hypophyseal tract (tractus hypothalamohypophysialis)

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.

Glossary

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
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