4. Structure and Functions of Pituitary Gland
4.1 Structure
- The pituitary gland is also called the hypophysis.
- The pituitary gland is approximately the size of a pea.
- It hangs by a stalk from the inferior surface of the hypothalamus of the brain called infundibulum.
- The anterior pituitary gland controls the activity of so many other endocrine glands that it has often been called the “master endocrine gland.”
- It has two functional lobes;
- the anterior pituitary (glandular tissue) (adenohypophysis)
- the posterior pituitary (nervous tissue) (neurohypophysis)
The anterior pituitary
- The network of blood vessels forms part of the pituitary portal system, which transports blood from the hypothalamus to the anterior pituitary.
- This blood transports releasing and inhibiting hormones secreted by the hypothalamus.
- The releasing and inhibiting hormones that stimulate and inhibit secretion of specific anterior pituitary hormones.
The posterior pituitary
- This is formed from nervous tissue and consists of nerve cells surrounded by supporting cells called pituicytes.
- These neurones have their cell bodies in the hypothalamus and their axons form a bundle known as the hypothalamohypophyseal tract.
- Posterior pituitary hormones are synthesised in the nerve cell bodies, transported along the axons and then stored in vesicles within the axon terminals.
- Their release by exocytosis is triggered by nerve impulses from the hypothalamus.
Figure 2– Pituitary Gland
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Structure of Pituitary Gland |
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4.2 Functions
The functions of the hormones released by pituitary gland as follows;
Table 1- Functions of the Pituitary Hormones
| Gland | Hormone | Target Tissue | Response |
| Anterior Pituitary gland | Growth hormone | most tissues | increases gene expression, breakdown of lipids, and release of fatty acids from cells; increases blood glucose levels. |
| Thyroid-stimulating hormone (TSH) | thyroid gland | increases thyroid hormone secretion (thyroxine and triiodothyronine). | |
| Adrenocorticotropic hormone (ACTH) | Adrenal cortex | increases secretion of glucocorticoid hormones, such as cortisol; increases skin pigmentation at high concentrations. | |
| Melanocyte-stimulating hormone (MSH) | melanocytes in skin | increases melanin production in melanocytes to make skin darker in color. | |
| Luteinizing hormone (LH) or Interstitial cell–stimulating hormone (ICSh) | ovary in females, testis in males | Promotes ovulation and progesterone production in ovary; promotes testosterone synthesis and support for sperm cell production in testis | |
| Follicle-stimulating hormone (FSH) | Follicles in ovary in females, seminiferous tubules in males | Promotes follicle maturation and estrogen secretion in ovary; promotes sperm cell production in testis | |
| Prolactin | ovary and mammary gland in females, testis in males | Stimulates milk production and prolongs progesterone secretion following ovulation and during pregnancy in women; increases sensitivity to LH in males | |
| Posterior Pituitary gland | Antidiuretic hormone (Adh) | Kidney | conserves water; constricts blood vessels |
| Oxytocin | uterus | increases uterine contractions | |
| mammary gland | increases milk letdown from mammary glands |
| Explanation is available on
Functions of Pituitary Gland |
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