Anterior Pituitary vs Posterior Pituitary
Pituitary gland weighs approximately 500mg to 900mg and lies immediately beneath the third ventricle and just above the sphenoidal sinus in the sella turcica (Turkish saddle). Pituitary glands and the hypothalamus together act as master regulators of the endocrine system. The hormones secreted by these organs collectively control important homeostatic and metabolic functions such as reproduction, growth, lactation, thyroid and adrenal gland physiology, and water homeostasis. The pituitary gland consists of two lobes; interior pituitary and posterior pituitary. Although two lobes are originated from different embryonic tissues, the hypothalamus regulates the secretion of pituitary hormones. Pituitary hormones, which are either produced or stored by the pituitary gland, alter the activities of peripheral endocrine organs.
Anterior Pituitary
Anterior pituitary produces hormones of its own, but their secretion is controlled by hypothalamus. Anterior pituitary hormones are proteins and glycoproteins, including somatotropic hormones (growth hormone (GH) and prolactin) and glycoprotein hormones (luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH)). Neurons in the hypothalamus release regulatory factors. These factors are carried by hypothalamic-pituitary portal system to the anterior pituitary where they control the release of anterior pituitary hormones. Hence, there is no direct nervous connection between the hypothalamus and interior pituitary gland. Anterior pituitary consists of a collection of cell types, each of which respond to specific stimuli and release specific hormones into the systemic circulation.
Posterior Pituitary
Posterior pituitary lies immediately beneath the hypothalamus, and it is connected through the pituitary stalk to the hypothalamus. Posterior pituitary that secretes posterior hormones is made up of glial tissue and axonal termini. It basically stores hormones, which are synthesized in the cell bodies of the supraoptic and paraventricular neurons in the hypothalamus. It does not produce its own hormones unlike the anterior pituitary does. Posterior pituitary secretes only two hormones; antidiuretic hormone (ADH), which is the regulator of plasma volume, and oxyticin that has an influence on uterine contraction and lactation.
What is the difference between Anterior and Posterior Pituitary?
• Anterior pituitary is derived from ectodermal tissue, whereas posterior pituitary is derived from the ventral surface of the diencephalon.
• Anterior pituitary produces its own hormones while posterior pituitary stores hormones which are originally produced in the hypothalamus.
• Anterior pituitary secretes GH, prolactin, LH, FSH and TSH hormones while posterior pituitary secretes ADH and oxyticin hormones.
• Anterior pituitary is highly vascularized than posterior pituitary.