<< Chapter < Page Chapter >> Page >

The anterior pituitary produces seven hormones: growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), melanin-stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). Anterior pituitary hormones are sometimes referred to as tropic hormones, because they control the functioning of other organs. While these hormones are produced by the anterior pituitary, their production is controlled by regulatory hormones produced by the hypothalamus. These regulatory hormones can be releasing hormones or inhibiting hormones, causing more or less of the anterior pituitary hormones to be secreted. These travel from the hypothalamus through the hypophyseal portal system to the anterior pituitary where they exert their effect. Negative feedback then regulates how much of these regulatory hormones are released and how much anterior pituitary hormone is secreted.

Posterior pituitary

The posterior pituitary    is significantly different in structure from the anterior pituitary. It is a part of the brain, extending down from the hypothalamus, and contains mostly nerve fibers and neuroglial cells, which support axons that extend from the hypothalamus to the posterior pituitary. The posterior pituitary and the infundibulum together are referred to as the neurohypophysis.

The hormones antidiuretic hormone (ADH), also known as vasopressin, and oxytocin are produced by neurons in the hypothalamus and transported within these axons along the infundibulum to the posterior pituitary. They are released into the circulatory system via neural signaling from the hypothalamus. These hormones are considered to be posterior pituitary hormones, even though they are produced by the hypothalamus, because that is where they are released into the circulatory system. The posterior pituitary itself does not produce hormones, but instead stores hormones produced by the hypothalamus and releases them into the blood stream.

Thyroid gland

The thyroid gland    is located in the neck, just below the larynx and in front of the trachea, as shown in [link] . It is a butterfly-shaped gland with two lobes that are connected by the isthmus    . It has a dark red color due to its extensive vascular system. When the thyroid swells due to dysfunction, it can be felt under the skin of the neck.

The thyroid is located in the neck beneath the larynx and in front of the trachea. It consists of right and left lobes and a narrow central region called the isthmus of thyroid. Above the isthmus of thyroid is the pyramidal lobe.
This illustration shows the location of the thyroid gland.

The thyroid gland is made up of many spherical thyroid follicles, which are lined with a simple cuboidal epithelium. These follicles contain a viscous fluid, called colloid    , which stores the glycoprotein thyroglobulin, the precursor to the thyroid hormones. The follicles produce hormones that can be stored in the colloid or released into the surrounding capillary network for transport to the rest of the body via the circulatory system.

Thyroid follicle cells synthesize the hormone thyroxine, which is also known as T 4 because it contains four atoms of iodine, and triiodothyronine, also known as T 3 because it contains three atoms of iodine. Follicle cells are stimulated to release stored T 3 and T 4 by thyroid stimulating hormone (TSH), which is produced by the anterior pituitary. These thyroid hormones increase the rates of mitochondrial ATP production.

Questions & Answers

what is bilateral symmetry
Mameibi Reply
Explain kingdom of fungi
HARUNA Reply
what are the nutritional requirement of organism
Patience Reply
which part of the alimentary canal were these cross section taken
Getrude Reply
what is alimentary canal were these cross section taken
Getrude
what is matter
Gifty Reply
from which part of the alimentary canal were these cross section taken fig 2.1 fig 2.2 b,c
Getrude Reply
explain the role played by b in the alimentary canal
Getrude
what is biology
Sunday Reply
what is mitosis
David Reply
structure of a kidney
Idriss Reply
explain sexual reproduction of a named flower taking account of pollination, fertilization and the change to seed and fruit.
Chinyi Reply
The study of all life or living matterThe living organisms of a particular region.
Oyewale Reply
what is ology
Green Reply
in which of the following stages of the cell cycle are chromosomes pulled apart to opposite poles of the cell
Amie Reply
Anaphase
Jonah
what is digestive system
Cyprain Reply
Digestive system is a system in mammals associated with the breaking down or assimilation of food substances into simple soluble and diffusable substances by mechanical and chemical means
Emmanuel
what is symbiotic factors of an organisms
Emmanuel Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Biology' conversation and receive update notifications?

Ask