Thursday, February 26, 2015
Pituitary Gland Anatomy Functions
The hypothalamus is the gland in the body that creates the hormones that are secreted by the pituitary gland’s neurohypophysis. It’s in charge of managing hormone production and secretion in the body, helped along by the actions and counteractions of the pituitary glands. The neurohypophysis releases a hormone, and the adenohypophysis produces hormones that regulate the other’s actions.
Another name for the pituitary gland is the cerebral hypophysis. It is located in the inferior side of the brain, within the diencephalon. The brain is attached to the pituitary gland through the pituitary stalk. Resembling a pea, the pituitary gland is very small with its overall size of 1.3 centimeters. It’s structured by the sphenoid bone’s sella turcica and is covered with dura mater. This gland has quite a demand for blood, and it gets its supply from the cerebral arterial circle.
The gland can be segmented into two parts: the anterior lobe and the posterior lobe. The anterior lobe is called the adenohypophysis and the posterior lobe is the neuropophysis. Each of the segments functions as a structural lobe and a functional lobe. In an adult body, the adenohypophysis is differentiated into the pars distalis and the bulbar segments. The thin section that divides the two is called the pars tuberalis. In a fetal body, what separates the anterior lobe from the posterior lobe is called the pars intermedia. As the fetus develops, this thin tissue begins to belnd with the surrounding cells of the anterior lobe. The process goes on until it gets completely unnoticeable in an adult body. The neural portion of the pituitary gland is neorhypophysis. This is the posterior part of the gland and it’s formed by the bulbar lobus nervosa, in part. A stalk is connected to bulbar lobus nervosa, making it possible for the pituitary gland to attach to the hypothalamus’ base. Resembling a funnel, this stalk is called the infundibulum.
The pituitary gland is composed of two distinctive parts:
The anterior pituitary or adenohypophysis is composed of cells that secrete hormones, such as growth hormone, prolactin, adrenocorticotropic hormone (ACTH), thyroid stimulating hormone (TSH) as well as luteinising hormone (LH) & follicle-stimulating hormone (FSH).
The posterior pituitary or neurohypophysis contains nerve cell axons reaching down from the hypothalamus and they release oxytocin and vasopressin.
The pituitary stalk connects the hypophysis to the base of the brain, to the hypothalamus.
Functions
Hormones secreted from the pituitary gland help control the following body processes:
- Growth (Excess of HGH can lead to gigantism and acromegaly.)
- Blood pressure
- Some aspects of pregnancy and childbirth including stimulation of uterine contractions during childbirth
- Breast milk production
- Sex organ functions in both males and females
- Thyroid gland function
- The conversion of food into energy (metabolism)
- Water and osmolarity regulation in the body
- Water balance via the control of reabsorption of water by the kidneys
- Temperature regulation
- Pituitary gland also makes endorphin to relieve pain and alter mood.
BLOOD SUPPLY
superior hypophyseal artery, infundibular artery, prechiasmal artery, inferior hypophyseal artery, capsular artery, artery of the inferior cavernous sinus
The pituitary gland produces hormones and a healthy balance of these hormones is essential for good health.
| Pituitary Hormones | Abbreviation | Role |
|---|---|---|
| Growth hormone | GH | Growth hormone controls our rate of growth and also regulates our metabolism. Growth hormone enables the body to grow and reproduce and it is essential for good health throughout our lives. Growth hormone is also of considerable interest as a drug used in both humans and animals, and there are problems of abuse of growth hormone in sport. |
| Prolactin | PRL | Prolactin is found in both men and women. Its principal function is to initiate and sustain lactation which is the process of producing and releasing breast milk. |
| Adrenocorticotropic hormone | ACTH | ACTH stimulates the adrenal gland to produce other substances including cortisol. Cortisol controls a number of functions and is particularly important in times of illness and stress. Hormones often have a knock-on effect initiating important processes in other glands and organs. |
| Thyroid stimulating hormone | TSH | TSH stimulates the thyroid gland. Thyroid stimulating hormone tells the thyroid gland to produce thyroid hormones which are needed by the body. The thyroid controls how quickly the body uses energy, makes proteins, and also regulates how sensitive the body should be to other hormones. |
| Luteinising hormone & Follicle-stimulating hormone | LH and FSH | Luteinising hormone and follicle-stimulating hormone are both regulating functions of the gonads (ovary and testis). They are not necessary for life but are essential for reproduction. Together they stimulate the reproductive organs and initiate puberty which enables children to develop into sexually mature adults. In women these hormones control ovulation and are essential for a normal menstrual cycle and for fertility. In men, these hormones stimulate the testes to produce sperm. |
| Vasopressin | AVP or ADH | Vasopressin (also called anti-diuretic hormone, ADH) is one of the hormones of the posterior pituitary. This hormone has a key role in the regulation of water, glucose and salts in the blood. Its single most important effect is as an anti-diuretic hormone. It is released when the body is dehydrated and sent to the kidneys where it concentrates the urine and conserves water. |
| Oxytocin | Oxytocin | Oxytocin is a posterior pituitary hormone. Oxytocin is an important hormone and is largely associated with female reproduction. It is released in large amounts during labour. It is also important after labour in the establishment of maternal behaviour and bonding between mother and child. Oxytocin can also affect our feelings and moods and is present in both men and women. |
The effects of these hormones show that the endocrine system is an information signal system like the nervous system. The endocrine system is connected to the nervous system through the pituitary gland via the hypothalamus. The hypothalamus is an extremely complicated region of the brain. It releases hormones which in turn stimulate or inhibit the activity of the pituitary gland. Disease in the hypothalamus can also adversely affect the function of the pituitary gland.
| Hypothalamic Hormones | Abbr. | Role |
|---|---|---|
| Growth hormone-releasing hormone | GHRH | GHRH is a hypothalamic peptide that stimulates both the synthesis and secretion of growth hormone. |
| Somatostatin | SS | SS inhibits growth hormone release from anterior pituitary. Analogues of somatostatin is used for the treatment of acromegaly and certain other types of tumours as well. |
| Corticotropin-releasing hormone | CRH | CRH is secreted by the hypothalamus in response to stress and it stimulates ACTH. |
| Thyroid stimulating hormone | TRH | Thyrotropin-releasing hormone (TRH) stimulates the release of thyroid-stimulating hormone and prolactin by the anterior pituitary. |
| Gonadotrophin-releasing hormone (also called Luteinizing hormone-releasing hormone (LHRH)) | GnRH | GnRH causes the pituitary gland to make and release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones are involved in reproduction. |
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