The posterior pituitary consists mainly of?

Appeared in: AIIMS Patna NO - 2020

Explanation

The posterior pituitary (neurohypophysis) is primarily composed of the unmyelinated axons of neurons whose cell bodies are in the hypothalamus.
These neuronal projections form the hypothalamo-hypophyseal tract, which serves as a conduit for hormones.
It functions as a release site for hormones (ADH and oxytocin) that are synthesized in the supraoptic and paraventricular nuclei of the hypothalamus.
The structure also contains specialized glial cells called pituicytes that support these axons.

Option A: Beta cells are endocrine cells located in the pancreas, not the pituitary gland.
Option B: C cells, or parafollicular cells, are located in the thyroid gland.
Option C: T cells are lymphocytes, a type of white blood cell, and are a component of the immune system, not the endocrine system's structural tissue.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Histological composition of the posterior pituitary gland as background academic context rather than a clinical decision trigger.
Understanding that the posterior pituitary is a collection of nerve endings is crucial for diagnosing endocrine disorders. Damage to the pituitary stalk (e.g., from trauma or surgery) can interrupt hormone release, leading to conditions like central diabetes insipidus (ADH deficiency).
Lesions in the hypothalamus can prevent the synthesis of ADH and oxytocin, while lesions in the posterior pituitary only prevent their release.
What if? If a patient presents with symptoms of excessive thirst and urination (polyuria and polydipsia) after a head injury, a nurse should suspect central diabetes insipidus due to potential damage to the hypothalamic-pituitary axis, affecting ADH release.

How to Approach the Question

First, identify the key term in the question: 'posterior pituitary'.
Recall the basic anatomy and physiology of the endocrine system, specifically the structure of the pituitary gland.
Remember that the pituitary has two distinct parts: the anterior (adenohypophysis) and posterior (neurohypophysis). The prefix 'neuro-' hints at its nervous tissue composition.
Evaluate each option. Beta cells (pancreas), C cells (thyroid), and T cells (immune system) are located in other parts of the body and have different functions.
Conclude that 'Neuronal projections' is the only option that correctly describes the main structural component of the neurohypophysis.

Concept Tested & Keywords

QA3GGJ82RxVJIbZLPBgdCy

E6 Histology Inderbir 11e pp. 139-141, 136-138

E6 Anatomy Applied Ashalatha 4e p. 215-217

Practise the full AIIMS Patna NO - 2020

Attempt every question from this paper in a timed mock, then review the full solution for each one.