Anatomy And Physiology

Anatomy Physiology



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Hormones are substances that help maintain a variety of metabolic processes in the human body, including growth and development, energy levels and other important bodily functions. The regulated secretion of hormones in the body helps maintain homeostasis (balance of body systems). There are three distinct structures of hormones: amino acid derivatives, petide derivatives, and lipid derivatives. Hormones are produced and stored in glands and organs throughout the body.

Hormones function as chemical messengers secreted by endocrine glands and transported in the blood stream throughout the body. Their function is to regulate various body processes, including growth, temperature control, digestion, reproduction, maturation, energy levels, glucose levels in the blood, etc. hormones only bind to cells that have receptor sites for that particular hormone. Receptors may be in the surface of the cell or inside the cell.

Water soluble hormones (glycoprotein hormones) bind with their cell receptor at surface level, resulting in a rapid action, while lipid steroid hormones generally react inside the DNA of the cell where they exert their effects through the nuclear receptors that control gene transcription and protein synthesis, resulting in a slower action.

Hormones are extremely powerful chemical substances. For this reason, small quantities of a given hormone can exert profound metabolic effects. The appropriate regulation of hormone secretion helps maintain homeostasis in the body. Hormone secretion is controlled by some kind of negative feedback mechanism; or by gland secretion in response to other hormones. Another method of hormone regulation is by direct nervous stimulation.

In a typical example of a negative feedback mechanism, the thyroid gland secretes thyroxine (T4). The secretion of thyroxine is stimulated by thyroid-stimulating hormone (TSH) produced by the pituitary gland. TSH is secreted in response to decreasing levels of thyroxine and triiodothyronine in the thyroid gland due to an iodine deficiency. The secretion of TSH is suppressed when T4 and T3 levels are increased. This mechanism helps maintain regular concentrations of thyroid hormones.

Endocrine gland hormones:

The endocrine system consists of glands that produce, store, and secrete hormones. These hormones control the physical and chemical processes (metabolism) occurring inside the human body. These hormones are secreted into the blood stream and transported to target cells throughout the body. The function of hormones is to transmit information from one group of cells to another in order to coordinate the functions occurring in the different organs which compose the human body.

The glands that composed the endocrine system include the hypothalamus, the pineal gland, the pituitary gland, the thyroid gland, the parathyroid gland, the adrenal gland, the gonads, and the pancreas. Each gland and organ of the endocrine system secretes different types of hormones which function differently in the cells they affect.

The gonads:

The male testes and the female ovaries produce sperm and ova respectively. These organs also secrete hormones (androgens in males and estrogens and progesterone in females) and are therefore considered as endocrine glands. In addition to the endocrine glands, other organs with hormonal activity include the stomach, the thymus, the small intestines, the heart and the placenta.

Hormone deficiency can originate from a number of endocrine disorders, including growth hormone deficiency (GHD), autoimmune inflammation, tumors, etc. In children GHD has no identifiable cause, while in adults, it is usually due to a pituitary tumor. If you or a loved one is experiencing hormone deficiency, you should seek the help of an endocrinologist.

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