This study unit will help you to:
- Understand the gross structure of the pituitary gland.
- Name the main parts and other major features of the pituitary gland.
- Describe the location, relations, and functions of the pituitary gland.
- Appreciate the structure and functions of the hypophyseal portal system.
The pituitary gland, also known as the hypophysis, is a small, ovoid structure, situated in the sella turcica of the sphenoid bone. Although it is relatively small (weighing only about 0.5g) it is considered to be the ‘master’ gland of the endocrine system. This is primarily due to the fact that it controls the activity of other endocrine glands in the body and consequently has many vital functions and roles in metabolism, growth, sexual maturation, reproduction, blood pressure and many other vital physical functions and processes.
The pituitary gland is comprised of two main lobes:
- Adenohypophysis (anterior lobe)
- Neurohypophysis (posterior lobe)
Both parts of the pituitary have distinct connections and functions. The anterior lobe is the hormone-producing area (‘adeno-’ = gland (Gr.)), therefore the majority of the pituitary hormones get produced here. In contrast, neurohypophysis doesn't produce hormones, but rather stores and releases hormones produced by certain areas of the hypothalamus.
The hypothalamus is the primary regulator of the pituitary gland, and consequently the endocrine system. It does this via two pathways: neural and nonneural/vascular. In the neural pathway, the hypothalamus controls the neurohypophysis via the hypothalamohypophyseal tract. In the vascular path, the hypothalamus influences the adenohypophysis via a vascular network known as the hypophyseal portal system.
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|Definition||‘Master’ gland of the endocrine system which controls the rest of the endocrine glands|
|Main parts||Adenohypophysis (anterior lobe): Derived from oral ectoderm
Neurohypophysis (posterior lobe): Derived from neural ectoderm
Adenohypophysis: Growth hormone (somatotropin), prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH)
Neurohypophysis: Oxytocin, vasopressin
|Functions||Regulation of metabolism, growth, sexual maturation, reproduction, blood pressure, breastfeeding, immune response and many other vital physical functions and processes|