Pituitary Anatomy: Sella Turcica Location, Lobes, and Portal Connections

Finding the Pituitary: The Sella Turcica “Seat”

The pituitary gland sits in a bony depression of the sphenoid bone called the sella turcica. Think of the sella as a protective cradle at the skull base: the gland is small, but its location is highly strategic because it lies at the crossroads of brain structures, venous channels, and air-filled sinus spaces.

Step-by-step: Locate it on a skull-base view

• Step 1: Identify the sphenoid bone at the center of the skull base.
• Step 2: Find the sella turcica (a saddle-shaped depression on the superior surface of the sphenoid).
• Step 3: Place the pituitary within the sella; it is covered superiorly by a dural fold (the diaphragma sellae) with an opening for the stalk.

Key neighbors (learn them as “above, beside, below”)

• Superior (above): Optic chiasm (where optic nerves partially cross).
• Lateral (beside): Cavernous sinuses (venous channels on each side of the sella).
• Inferior (below): Sphenoid sinus (air-filled sinus space within the sphenoid bone).

Gross Structure: Two Lobes + a Stalk

Grossly, the pituitary is organized into two main parts with different tissue origins and connections: the anterior pituitary (adenohypophysis) and the posterior pituitary (neurohypophysis). They meet within the sella but behave like two different “interfaces” with the hypothalamus.

Anterior pituitary (adenohypophysis)

• What it is: Glandular tissue that synthesizes and secretes hormones.
• Main control input: Chemical signals from the hypothalamus delivered through a specialized vascular route (the portal system).
• Where it sits: More anterior and bulkier portion within the sella.

Posterior pituitary (neurohypophysis)

• What it is: Neural tissue (an extension of the hypothalamus) that stores and releases hypothalamic hormones delivered by axons.
• Main control input: Direct neural connections (axons) from hypothalamic nuclei.
• Where it sits: More posterior portion, continuous with the stalk.

Infundibulum (pituitary stalk) and hypothalamic relationship

The infundibulum is the stalk connecting the pituitary to the hypothalamus. It is the physical corridor for two different communication routes:

• Neural route: Hypothalamic axons travel down into the posterior pituitary.
• Vascular route: Portal vessels travel from hypothalamus to anterior pituitary to deliver releasing/inhibiting factors efficiently.

Practical mental model: posterior pituitary = wired connection (axons); anterior pituitary = courier system (portal blood vessels).

The Hypophyseal Portal System: Anatomy That Enables Control

The hypophyseal portal system is a two-capillary-bed arrangement that links the hypothalamus to the anterior pituitary. Its purpose is anatomical efficiency: it delivers hypothalamic regulatory factors to the anterior pituitary in high concentration without first being diluted in the general circulation.

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Where the capillary plexuses sit

• Primary capillary plexus: Located in the median eminence at the base of the hypothalamus (near the top of the infundibulum). This is where hypothalamic factors enter the blood.
• Portal veins (hypophyseal portal vessels): Travel down the stalk from the primary plexus to the anterior pituitary.
• Secondary capillary plexus: Located within the anterior pituitary. This is where hypothalamic factors exit the blood and act on anterior pituitary cells.

Step-by-step: Trace the portal pathway like a map

1. Start: Hypothalamic neurons release regulatory factors into the primary capillary plexus (median eminence).
2. Travel: Blood carrying these factors moves through portal veins down the infundibulum.
3. Arrive: Factors enter the secondary capillary plexus in the anterior pituitary.
4. Effect: Anterior pituitary endocrine cells respond by adjusting their hormone secretion into systemic circulation.

Why portal vessels matter (anatomy-to-function link)

• High local concentration: Short, direct vascular route prevents dilution of hypothalamic signals.
• Fast, targeted regulation: Small changes in hypothalamic output can quickly change anterior pituitary secretion.
• Separation of routes: Keeps anterior pituitary control primarily chemical (blood-borne factors) while posterior pituitary control is primarily neural (axons).

Quick check: If a signal must reach the anterior pituitary, it typically uses portal blood. If it must reach the posterior pituitary, it typically uses axons.

Cross-Section Activity: Label the Skull Base Around the Sella

Goal: Build a 3D understanding by labeling a midline (sagittal) cross-section through the skull base. Use the list and prompts below to label structures in relation to the pituitary.

Activity setup (what to use)

• A printed sagittal skull-base diagram (or a blank outline you draw).
• Two colored pencils: one for bone/air spaces, one for neural/vascular structures.

Label list (minimum set)

• Sphenoid bone
• Sella turcica
• Pituitary gland
• Anterior pituitary (adenohypophysis)
• Posterior pituitary (neurohypophysis)
• Infundibulum (stalk)
• Hypothalamus
• Optic chiasm (superior to sella)
• Sphenoid sinus (inferior to sella)
• Diaphragma sellae (dural roof concept)

Labeling prompts (answer on your diagram)

1. Draw a small oval for the pituitary inside the sella. Split it into anterior and posterior portions.
2. Draw the infundibulum as a narrow stalk exiting superiorly through the dural roof opening.
3. Place the optic chiasm directly above the sella (not far away—keep it close).
4. Sketch the sphenoid sinus as an air space directly below the sella, separated by a thin bony layer.
5. Add a small “capillary bed” symbol at the median eminence (primary plexus) and another within the anterior pituitary (secondary plexus). Connect them with two or three vertical lines representing portal veins down the stalk.

Neighbor Risk: Why Proximity Matters Clinically (Anatomy-First)

Because the pituitary sits in a compact bony compartment with critical neighbors, even small changes in the pituitary region can have outsized effects. This segment focuses on spatial risk: what structures are most vulnerable simply because they are close.

1) Superior neighbor risk: optic chiasm

• Anatomy fact: The optic chiasm lies just superior to the sella.
• Practical implication: Anything that occupies extra space upward from the sella region can affect visual signal transmission because there is limited room between the gland and the chiasm.
• Study cue: When you see “sella,” immediately picture “optic chiasm above.”

2) Lateral neighbor risk: cavernous sinus

• Anatomy fact: The cavernous sinuses sit laterally on both sides of the pituitary.
• Practical implication: The pituitary’s side walls are adjacent to venous channels and tightly packed neurovascular pathways, so lateral extension or invasive procedures must respect this boundary.
• Study cue: Picture the pituitary as a midline structure with “venous corridors” on both sides.

3) Inferior neighbor risk: sphenoid sinus

• Anatomy fact: The sphenoid sinus is directly inferior to the sella, separated by bone that can be thin.
• Practical implication: The inferior route provides access to the sella but also means the pituitary’s floor is closely related to an air-filled sinus space.
• Study cue: “Sella sits on sinus.”