Term Paper on "Adrenal Gland"

Term Paper 8 pages (2250 words) Sources: 5 Style: APA

[EXCERPT] . . . .

Adrenal Gland

KEEPING the BODY WHOLE and FUNCTIONAL

The Body Organization

The human body is an organized system, which consists of cells, tissues, organs and organ systems (Degen 2008). A cell is the basic unit of structure and function in every living thing or organism. It performs the basic functions to keep the organism alive. Most cells are microscopic. Each cell is covered by a cell membrane. Inside it is the nucleus, which controls and directs the cell's activities. It also contains all the information on the cell's characteristics. Cells form a tissue to perform the same function. The four basic types of tissue are muscle, nervous, connective and epithelial. Tissues, in turn, form an organ. Every organ performs a specific function, which is often more complex than that of a tissue. And organs form an organ system. They perform the same and unified function. An example is the circulatory system. The body's different organ systems function together and depend on one another. When they function well together, they create a condition known as homeostasis (Degen).

Homeostasis

The body consists of 11 organ systems, which coordinate to keep the body functioning normally (Farabee 2006). This occurs according to a set of internal conditions collectively known as homeostasis. Homeostasis is the maintenance of that internal environment for survival. The term was first used in 1959 to describe physical and chemical conditions required by an organism in order to remain functional. The organism consists of component cells, tissues, organs and organ systems. For example, enzymes perform best within a specific range of temperature and pH. Cells must keep a balance between too much and too little water in their external environment. Both show homeostasis. The body works best within a particular temperature. That too is homeostasis. Multi-celled organisms, including human beings, achieve this through their organs and organ systems when they coordinate. Single-celled organisms must accomplish this within their single-celled environment.

Body Systems

The vertebrae of animals, including human beings, consist of two cavities, namely the thoracic and the abdominal (Farabee 2006). The thoracic cavity contains the heart and lungs, while the abdominal cavity contains the digestive organs. Four of the five physical senses are contained in the head or cephalic region and protected by the bony skull. The organ systems have been classified according to their functions. The muscular system enables the body to move. It produces those movements, body heat, and posture and props the body up. It consists mainly of muscle fibers. This system closely coordinates with the skeletal system. The skeletal system supports and protects attachment points for the muscles. It is the rigid framework of the body for movement. Aside from supporting and protecting body parts, it also produces blood cells in the bone marrow and stores minerals. The integument or skin system provides outermost protective layers. Its functions include preventing water loss and invasion of foreign microorganisms into the body itself. The skin consists of three layers, namely the epidermis as the outermost; the dermis; and subcutaneous layer. The basal cells on the epidermis undergo continuous mitosis. Structures, like sweat glands, hair follicles and oil glands, are found on the dermis. Loose connective tissue and adipose tissue are found in the subcutaneous layer (Farabee).

The respiratory system brings in oxygen from outside the body to the inside and eliminates carbon dioxide at the same time (Farabee 2006). This exchange also maintains the blood pH. The digestive system breaks down food ingested into nutrient molecules and eliminates solid wastes from the body. Digestive processes change food into particles, which can pass into the bloodstream. These food molecules are absorbed at the small intestines where they enter the circulatory system. This system also recycles water and brings back vitamins food in the large intestine. The circulatory system carries oxygen, carbon dioxide, nutrients, wastes, immune components and hormones where they should go. The major circulatory organs, which perform this function, are the heart, capillaries, arteries and veins. The lymphatic system likewise brings excess fluids to and from the circulatory system and fat to the heart (Farabee).

The immune system plays a very important role in the body's organization. It defends the internal environment from external invaders, like harmful microorganisms and viruses (Farabee 2006). It releases cells, which fight disease by triggering an antibody or antigen response. An autoimmune disorder occurs when a person's own immune system attacks the body's own cells and causes the destruction of his own tissues (Lohr 1999). Autoimmunity has been recognized as the cause of many disorders, whether general or specific. An autoimmune disease is generalized if it occurs simultaneously in many tissues. It is specific it the autoimmune reaction occurs in a single organ. Why the system becomes dysfunction has remained mysterious. But most medical experts agree that genetic, environmental and hormonal factors are involved in the dysfunction. They also suspect the mechanisms of particular substances not usually exposed to the immune system, some bodily changes and the immune system's own failure to recognize the body's own components (Lohr).

The excretory system eliminates excess internal body fluids and metabolic wastes from the internal environment (Farabee 2006). It eliminates organic wastes from the blood as urine through the kidneys. This system also keeps fluid levels at normal levels. The nervous system coordinates the functions of internal organs and systems within the body organization. Among these functions are memory, learning and conscious thought. It also regulates and maintains autonomic functions like heartbeat, breathing, and involuntary muscular actions. And the endocrine system controls body metabolism, growth and reproduction. The organs involved are not in direct contact but transmit messages through chemical messages in the bloodstream (Farabee).

Of the various body systems, the nervous system and the endocrine system assert the ultimate control on homeostasis (Farabee 2006). That control is most often in the form of negative feedback loops. A negative feedback turns off the stimulus, which sets it off. A positive feedback increases the stimulus (Farabee).

The "Masterly" Endocrine System

The tissue cells of this system secrete hormones, which perform the chief tasks of the body system (Bauer 2005). Hormones are substances, classified as polyprotein or peptides, steroids, or amines. Steroid hormones bind to receptors within the cytoplasm of the cell and cause a change in the activity of the gene. Other hormones require other messengers to effect control or change in the system. The major organs in this system are the hypothalamus, anterior pituitary gland, posterior pituitary gland, thyroid gland, parathyroid gland, adrenal gland, endocrine pancreas, ovaries, and testes. The hypothalamus influences the function of the thyroid gland, adrenal cortex, the ovaries and the testes. It produces hormones, which travel to the anterior pituitary gland and bring on the release of certain hormones. These hormones are corticotrophin-releasing, thyrotropin-releasing, gonadotrophin-releasing, somastatin, and growth-releasing (Bauer).

The glands

The hypothalamus produces and stores antidiuretic hormone or ADH and oxytocin in the posterior pituitary until they are released and circulated in the body (Bauer 2005). ADH helps regulate the re-absorption of water by the kidneys while oxytocin plays a significant role in lactation and uterine contraction. The releasing hormones stimulate this gland to produce adrenocorticotropic hormone, thyroid-stimulating hormone, luteinizing hormone, follicle-stimulating hormone, prolactin and growth hormone. The hypothalamus and negative feedback regulate the secretions of the anterior pituitary gland. The thyroid gland is found below the cricoid cartilage of the neck. It secretes the three major hormones, namely, thyroxine, triiodothyronine and calcitonin. Thyroxine and triiodothyronine produce energy, while calcitonin stimulates the uptake of calcium ions from the blood to the bones. The four parathyroid glands are approximate or embedded in the back part of the thyroid. They secrete a parathyroid hormone, needed to maintain serum calcium levels. Adrenal glands consist of the adrenal medulla and the adrenal cortex. They are found in the superior pole of each kidney. The hormones, epinephrine and norepinphrine, produce the alarm response to fight or flee along with that of the sympathetic nervous system. Among the cortical hormones are glucocorticoids, aldoesterone, and the adrenal androgens. Glucocorticoids stimulate gluconeogenesis, the metabolism of protein and lyposysis. Aldosterone asserts major control of sodium balance and volume. The adrenal androgens play a major role in the development of secondary sex characteristics. And the pancreas, located behind the stomach, has two functions. It regulates blood sugar by secreting insulin, glucagons, somatostatin and polypeptide. Many other organs produce other hormones. The gonads produce sex hormones. The pineal gland produces the hormone melatonin, necessary to induce sleep. The heart produces the natriuretic hormone and the kidneys produce erythropoietin (Bauer).

Tampering with the endocrine system can disturb the intake of fluid or food, elimination, energy level, body characteristics, reproductive or sexual functioning, tolerance and many other bodily changes (Bauer 2005). Disorders to the endocrine glands can be in the form of acromegaly or gigantism, galactorrhea, amenorrhea, gynecomastia, dwarfism, diabetes insipidus, hyperthyroidism or hypothyroidism, Cushing's syndrome or Addison's disease, hyperaldosteronism, pheochromocytomas, and diabetes mellitus (Bauer).

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