Problem 17 - Objective Biology for NEET

Question

Which of the following is incorrect about pituitary? (a) Located in bony cavity called sella turcica. (b) Attached to hypothalamus by stalk. (c) Divided anatomically into adenohypophysis and neurohypophysis. (d) Secretes released and inhibitory hormones.

Step-by-Step Solution

Answer

The incorrect statement about the pituitary gland is: (d) Secretes released and inhibitory hormones.

Step 1: Anatomy of Pituitary Gland

The pituitary gland is located in a small bony cavity at the base of the brain called the sella turcica. So, statement (a) is correct.

Step 2: Connection with Hypothalamus

The pituitary gland is connected to the hypothalamus by a short stalk. The hypothalamus controls the pituitary gland's secretion of hormones. Therefore, statement (b) is correct.

Step 3: Structural Division

Structurally and functionally, the pituitary gland is divided into two parts: the anterior pituitary (or adenohypophysis) and the posterior pituitary (or neurohypophysis). Thus, statement (c) is also correct.

Step 4: Hormone Release

The pituitary gland releases several hormones that affect various parts of the body, including the adrenal glands, thyroid gland, ovaries, and testes. The anterior pituitary releases hormones upon receiving releasing hormones from the hypothalamus. There exist both releasing and inhibitory hormones in the hypothalamus, not the pituitary. Therefore, statement (d) is incorrect.

Key Concepts

Hypothalamus

The hypothalamus is a small but crucial part of the brain that regulates many essential bodily functions. Positioned at the base of the brain near the pituitary gland, it acts as a critical link between the nervous system and the endocrine system.
This connection allows the hypothalamus to play a vital role in maintaining homeostasis, which is the body's stable internal environment. The hypothalamus monitors various states of the body, such as temperature, hunger, and thirst, and responds accordingly to maintain equilibrium.
Some of its key functions include:

• Regulating body temperature
• Controlling hunger and thirst
• Managing sleep cycles
• Influencing emotional responses

One of the most significant roles of the hypothalamus is to produce and release hormones that regulate the pituitary gland. These hormones can either prompt or inhibit hormone production in the anterior pituitary, demonstrating its role as a master regulator of the endocrine system.

Adenohypophysis

The adenohypophysis, also known as the anterior pituitary, is the front portion of the pituitary gland. It originates from an outgrowth of oral ectoderm, which separates from the roof of the embryo's mouth during development. This gland segment plays a crucial role in hormone production and secretion, profoundly influencing growth, metabolism, and reproduction.
Key hormones secreted by the adenohypophysis include:

• Growth hormone (GH) - Stimulates growth and cell reproduction.
• Adrenocorticotropic hormone (ACTH) - Stimulates the production of cortisol by the adrenal glands.
• Thyroid-stimulating hormone (TSH) - Encourages the thyroid gland to produce hormones that regulate metabolism.
• Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) - Control reproductive processes, including ovulation and sperm production.
• Prolactin (PRL) - Responsible for milk production in mammals.

The adenohypophysis receives signals from the hypothalamus in the form of releasing or inhibiting hormones, which determines whether it should increase or decrease hormone output accordingly.

Neurohypophysis

The neurohypophysis, or posterior pituitary, is the back part of the pituitary gland. Unlike the anterior pituitary, it does not produce hormones itself. Instead, it serves as a storage site and release point for hormones produced by the hypothalamus.
The neurohypophysis is unique as it consists of neural tissue, allowing it to effectively communicate with the central nervous system. It is primarily involved in the storage and release of two important hormones:

• Antidiuretic hormone (ADH) - Also known as vasopressin, ADH helps regulate water balance in the body. It prompts the kidneys to reabsorb water, thus decreasing urine output and preventing dehydration.
• Oxytocin - This hormone plays a crucial role in childbirth and lactation. It stimulates contractions in the uterus during labor and assists milk ejection during breastfeeding.

Thus, the neurohypophysis functions mainly as a conduit for hormones synthesized by the hypothalamus, releasing them into the bloodstream as needed to maintain physiological balance.