Pituitary Gland – Tutorial
Please read Unit 6 – Introduction to Endocrine Tissues prior to completing the activities in this chapter.
Introduction to the Pituitary Gland
The pituitary gland (hypophysis) is a complex endocrine structure attached to the inferior hypothalamus of the brain by a narrow stalk-like connection known as the infundibulum. The pituitary gland is divided into anterior and posterior lobes which secrete a variety of hormones. The posterior pituitary gland (neurohypophysis) is responsible for secreting two hormones into the bloodstream and the anterior pituitary gland (adenohypophysis) produces and secretes seven different hormones into the blood.
The two hormones secreted from the posterior pituitary gland are antidiuretic hormone (ADH) and oxytocin (OXT). These two hormones are produced in the cell bodies of neurons originating in the hypothalamus of the brain and then transported along axons that extend through the infundibulum to the posterior pituitary gland where the hormones are secreted into capillaries. In other words, antidiuretic hormone and oxytocin are hypothalamic hormones that are secreted from the posterior pituitary gland.
The anterior pituitary gland is divided into three regions. The pars tuberalis is the small, superior portion of the anterior pituitary located in the infundibulum. The pars tuberalis partially wraps around axons descending from the hypothalamus through the infundibulum toward the posterior lobe. The pars distalis is the largest portion of the anterior pituitary gland and contains the largest volume of secretory cells. The pars intermedia is a narrow band sandwiched between the pars distalis and the posterior lobe of the pituitary gland.
The seven hormones produced and secreted from the anterior pituitary gland are thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), growth hormone (GH), and melanocyte-stimulating hormone (MSH). MSH is produced and secreted by cells in the pars intermedia and the other six anterior pituitary hormones are produced and secreted by cells in the pars distalis. Production and secretion of anterior pituitary hormones is controlled by regulatory hormones that are produced in the hypothalamus of the brain and delivered directly to the anterior pituitary via a special network of blood vessels known as the hypophyseal portal system.
