What is the Difference Between Adenohypophysis and Neurohypophysis?

The pituitary gland is a small, pea-sized organ located at the base of the brain, below the hypothalamus. It plays a crucial role in the endocrine system, secreting various hormones. The pituitary gland has two distinct lobes: the adenohypophysis (anterior lobe) and the neurohypophysis (posterior lobe).

The main differences between the adenohypophysis and neurohypophysis are:

1. Origin: The adenohypophysis is derived from the oral ectoderm and is epithelial in origin, while the neurohypophysis is derived from the neural ectoderm.
2. Function: The adenohypophysis regulates various physiological processes, such as stress, growth, reproduction, and lactation. In contrast, the neurohypophysis regulates fluid balance and reproductive actions.
3. Hormone synthesis: The adenohypophysis synthesizes hormones, while the neurohypophysis does not. Instead, it serves as a site where axons project from neuronal cell bodies in the supraoptic and paraventricular nuclei of the hypothalamus.
4. Proportion: The adenohypophysis accounts for 80% of the total weight of the pituitary gland, while the neurohypophysis accounts for 20%.
5. Connection to the hypothalamus: The neurohypophysis contains axonal knobs and blood vessels connecting it to the hypothalamus, while the adenohypophysis contains a portal system with blood sinusoids connecting it to the hypothalamus.

Comparative Table: Adenohypophysis vs Neurohypophysis

The main differences between the adenohypophysis and neurohypophysis are their tissue composition, location, and function. Here is a table summarizing these differences:

The adenohypophysis is the larger anterior lobe of the pituitary gland and is responsible for producing hormones that regulate various physiological processes, such as growth hormone, prolactin, and thyroid-stimulating hormone. On the other hand, the neurohypophysis is the smaller posterior lobe and does not synthesize hormones. Instead, it secretes hormones produced in the hypothalamus, such as oxytocin and arginine vasopressin (ADH).