1. Define endocrine glands. What are the major differences between endocrine and exocrine glands?
a) Endocrine glands are ductless glands that produce hormones and release them directly into the blood stream.
b) Exocrine glands produce nonhormonal substances that include sweat, mucous, oil, and saliva and many others. They have ducts that secrete these substances into body cavities and onto body surfaces . They secrete enzymes, may or may not have ducts. Endocrine glands are ductless glands that produce hormone. They are vascularized glands and they secrete internally. They include the pituitary, thyroid, parathyroid, adrenal, and pineal glands as well as the hypothalamus, pancreas, gonads and placenta.
2. What is pituitary gland? Define the major hormones and their actions secreted by anterior and posterior pituitary gland.
a) The pituitary gland is the neuroendocrine gland located near beneath the brain that serves a variety of functions including regulation of gonads, thyroid, adrenal cortex, lactation, and water balance.
b) Anterior pituitary hormones include: growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), Follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL). Posterior pituitary hormones include oxytocin and antidiuretic hormone (ADH) or vasopressin.
Growth Hormone (GH)- stimulates growth
Thyroid-stimulating Hormone (TSH) (thyrotrophin)- stimulates the thyroid gland to secrete its own
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The adrenal glands are composed of two sections, the medulla and the cortex. The medulla part of the gland is what produces adrenaline-like hormones. The cortex produces a group of hormones called corticosteroids
Hormone cells are typically of a particular cell type, residing within a certain endocrine gland, such as thyroid gland, ovaries, and testes. Hormones exit their cell of origin through the process of exocytosis
The pituitary is stimulated to release growth hormone (GH) by growth hromone releasing hormone (GHRH) produced in the hypothalamus. It is inhibited from releasing growth hormone by growth hormone release-inhibiting hormone(GHRIH), also produced by the hypothalamus.
According to Shier, Butler & Lewis (2009) “other glands that produce hormones and thus are parts of the endocrine system include the pineal gland and the thymus gland”. Shier et al., 2009 argued the pineal gland, located deep between the cerebral hemispheres, secretes hormone melatonin that acts on certain brain regions that function as a biological clock. The changing levels of melatonin across 24 hours enable the body to know when day is and when is night.
Exocrine gland release substances through ducts or tubes that lead the external surface of the membrane, sweat glands, saliva, or the gastrointestinal tract. Endocrine gland doesn’t have any duct that lead to the surface, it diffuses its secretion into the bloodstream.
Gonadotropin is released from the hypothalamus. It travels through the hyposeal tract into the anterior pituitary lobe. The anterior pituitary lobe is stimulated by gonadotropin to release follicle-stimulating hormones (FSH) and lutenising hormones (LH) into the blood to stimulate the gonads to produce sex steroids such as testosterone. Growth hormones also operate using this mechanism.
The Pituitary Gland - The pituitary gland is a pea-sized structure located at the base of the brain, just below the hypothalamus, to which it is attached via nerve fibers. It is part of the endocrine system and produces critical hormones, which are chemical substances that control various bodily
Adrenal glands, located near the kidneys, secrete several hormones that are activated by the nervous system. These hormones dictate the body’s reaction to stressful situations. Each person secretes a different amount of hormones, therefore affecting behavior in stressful situations differently (Morris & Maisto, 2005).