Natomy, Physiology and of the Integumentary and Lymphatic Systems - Coursework Example

Anatomy, Physiology and of the Integumentary and Lymphatic Systems In Conjunction with the Immune System An integument is any natural outer coveringin a plant or animal; the word is derived from the Latin ‘integument’, which translates as “enclosure” or “cover.” For humans, the integumentary system encompasses the skin, accessory features (such as nails and hair) and exocrine glands (which open to the skin surface and secrete or absorb certain substances) (Gale, 2005, Design introduction). Keratin, a fibrous protein also found in the skin, is highly concentrated to form the fingernails (Farabee, 2001a, Hair and Nails section). The hair shaft, pushed out by the hair follicle, is likewise made almost entirely of protein, a tissue constituting much of the skin. The inner core is keratin, while the outer layer is a single layer of overlaid flat cells (Gale, 2005, Hair section). All integumentary external cells, of nails, hair, and skin, are dead cells. This is because new cells are generated beneath the surface; this process pushes the dead cells towards the outside. This process is easiest to discuss through an anatomical dissection of the skin into it’s three layers: the epidermis, the dermis, and the subcutaneous layers. The epidermis is composed of multiple layers of epithelial cells, which are extremely flat and range from two extremes. The outermost layer is entirely dead and made entirely of keratin, which is tightly joined so as to be waterproof. The innermost layer, consists of basal and melanocyte cells: the former produces keratin; the latter, melanin. Beneath these layers lies the live cells of the dermis, which produces all of the accessory features, contain the nerve fibers and blood vessels, and is constructed of fibrous proteins of collagen combined with connective tissue. The dermis is much thicker than the epidermis and is anchored to the muscles by the subcutaneous layer (Gale, 2005, Epidermis and Dermis sections). Farabee ( 2001a) notes that “Skin functions… include protection, regulation of body temperature, sensory reception, water balance, synthesis of vitamins and hormones, and absorption of materials.” The external layer both prevents excessive water loss while allowing the body to cool itself via sweat glands and the process of evaporation. The glands contract when the body has cooled. Other glands secrete acidic solutions to the skin surface to prevent fungus growth. Sebaceous (oil) glands secrete a mixture of fatty proteins both through hair follicles and directly to the skin surface. These oils prevent the dead hair and skin cells from drying out, while simultaneously killing bacteria on the skin surface (Gale, 2005, Sebaceous glands section). The epidermal melanocytes help prevent harm from UV radiation by producing melanin - it is this pigment which gives the skin both it’s coloring and it’s ability to darken (Gale, 2005, Epidermis section). The dermis sends nutrients to the epidermis through extended capillaries into the basal cells called dermal papillae. The dermal papillae result in looped ridges on the outer surface, i.e. fingerprints and similar markings. The sweat glands of the dermis are divided into two categories: the eccrine and the apocrine (Gale, 2005, Dermis section). The first are the sweat gland found all over the body, the second refers particular sweat glands found in the armpit, groin, and nipple area. The apocrine are normally larger glands which empty out into hair follicles; their production attracts a bacteria which produces what is generally termed ‘body odor’. The dermis layer also contains the hair follicles (attached to pili muscles), and sensory receptors, which communicate information of temperature or pressure to the brain, thus allowing the brain to process external information (Gale, 2005, Hair and Sensory Reception sections). The lymphatic system mimics the circulatory system: it is a system of tubes that spread throughout the body anywhere the blood is carried. Plasma from the blood washes cell walls and is then transported away through the lymphatic vessels. The clear liquid is now called lymph. Along the path of the lymphatic vessels are small nodes (lymph glands). These nodes are located throughout the body: in the armpits, the neck, the groin, the pelvis, chest and in the abdomen. Lymphatic System body organs involved are the adenoids, thymus, tonsils, bone marrow and spleen (Cancer Research UK, 2002). Lymph nodes serve to filter the lymph as it circulates. The spleen, filled with both lymph and blood, acts as a filter for both lymph and blood (Farabee, 2001b, Lymphatic system section) - it is situated above the left kidney (Cayuga College, n.d.a, Spleen section). Adenoids and tonsils are situated near the external openings of the nose and throat, respectively, and filter the entrance to the lugs and the digestive tract. The thymus, located beneath the breastbone, matures white blood cells, or T-lymphocytes (T-cells), in the bloodstream. Bone marrow produces lymphocytes in general; the ones that mature there are referred to as B-lymphocytes (B-cells), or red blood cells (Farabee, 2001b, Lymphatic system section). The Cancer Research UK (2002) defines the main purposes of the lymphatic system. These are 1) to actively drain away tissue fluid and restore them to the blood, 2) to filter the lymph fluid itself, and 3) to stave off infections. The first process works because of the one-way nature of the lymphatic vessels. Once the fluid has entered there, pumping action is provided by skeletal muscle contraction (Farabee, 2001b, Lymphatic system section). As mentioned above, the spleen operates as the main filter: it does so by replacing decaying red blood cells with new ones (Cancer Research UK, 2002). The process of fighting off infections involves the entire lymphatic system. The lymphocytes produced by the stem cell bone marrow and matured in the thymus produced hormone thymosin (Farabee, 2001b Lymphatic system section), become T-cells, which are capable of producing antibodies. Macrophages, found within the lymph nodes, are capable of enclosing and consuming invading germs. Yet these aspects are but a fraction of the body’s defenses against harmful outside forces. The lymphatic system, combined with the integumentary system, form the body’s immune system, a delicate balance between protective measure and active defense (Cancer Research UK, 2002). The immune system first line of defense covers nonspecific immunity (Cayuga College, n.d.a.) and consist of the skin and mucous membranes. The skin acts as a barrier preventing foreign elements direct entry. Skin gland secretions deter much bacteria growth on the surface; enzymes in saliva and tears attack the cell walls of bacteria (Farabee, 2001b, General Defenses section). Hair surrounding or within orifice openings actively deter large foreign body entry, while mucous provides a sticky surface in which to trap invaders. Trace elements of hydrochloric acid complete the general arsenal of the skin and mucous membranes (Cayuga College, n.d.a., Nonspecific Immunity section). When microorganisms penetrate any of these physical barriers, the next stage of nonspecific immunity is inflammation (Farabee, 2001b, General Defenses section). The effected cells release such mediator chemicals as histamine, prostaglandins, kinins… any of which start a process known as chemo taxis which attracts white blood cells (Cayuga College, n.d.a., Nonspecific Immunity section). Capillaries increase blood flow, thereby increasing the localized temperature and generally killing off the invader. Capillary fluid in the area causes swelling. Specialized T-cells called monocytes break down the last elements of the invader and remove any debris from the episode (Farabee, 2001b, General Defenses section). There are three further forms of general defense. The macrophages (an enlarged monocyte cell) and the Natural Killer (NK) cells directly attack microbe infection, the former by essentially consuming the offending target and the latter by killing of any of the body’s affected cells. Some body cells, when infected, produce the chemical interferon, which prevents a virus from reproducing within the cell (Cayuga College, n.d.a., Nonspecific Immunity section). The final method is called the complement system. Proteins produced by the liver bind to a bacteria and allow a sudden influx of salt and water through the membrane, causing the cell to burst (Farabee, 2001b, General Defenses section). Specific immunity comes in two forms, either of which involves time for the system to identify the invading germ. The first form, regulated by B-cells, is antibody-mediated. This specific defense responds to the invasion of bacteria or viruses (Farabee, 2001b, Specific Defenses section). A B-cell bonds with an antigen (invader), at which point it begins to produce antibodies to fight the invader by cloning itself. Some of the cloned antibodies are not used, kept instead as a kind of immune memory against future invasion. Antibodies defuse antigens by bonding with them and either making it detoxifying it or by making it easier for phagocytes (such as macrophages) to encompass (Cayuga College, n.d.a., Antibody-Mediated section). T-cells control the other form, known as cell-mediated immunity. It protects body cells from fungi, protozons, and other parasites; it also kills cancerous cells or handles infected cells (Farabee, 2001b, Specific Defenses section). T-cells bond with antigens and become sensitized. They clone more sensitized cells, which travel to the invaders point of entry. There, T-cells release cytokines, which draw macrophages to the area and increase their efficiency in consuming the antigens. Killer (or catatonic) T-cells release a poison called lymph toxin, which destroys antigens directly (Cayuga College, n.d.a., Cell-Mediated section). There are three methods of attaining specific immunity. Inherited immunity develops within the body before birth. Natural immunity can occur either through having the infection once and developing an immunity or by receiving immunity through the mother’s milk or placenta. Artificial immunity refers to deliberate exposure. The active method involves direct introduction of the antigen into the body via a vaccine dose; the passive method involves an injection of another person’s antibodies into one’s own body (Cayuga College, n.d.a., Types of Specific Immunity section). Works Cited Cancer Research UK (2002). The Lymphatic System. Last updated June 23, 2006. Retrieved July 28, 2006 from http://www.cancerhelp.org.uk/help/default.asp?page=117 Cayuga College (n.d.a). Immune System. Retrieved July 28, 2006 from http://www.cayuga- cc.edu/people/facultypages/greer/biol204/lymphatic3/lymphatic3.html Cayuga College (n.d.b). Lymph Nodes. Retrieved July 28,2006 from http://www.cayuga- cc.edu/people/facultypages/greer/biol204/lymphatic2/lymphatic2.html Farabee, M.J. (2001a). The Integumentary System. Estrella Mountain College. Retrieved July 28, 2006 from http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookINTEGUSYS.html Farabee, M.J. (2001b). Lymphatic System and Immunity. Estrella Mountain College. Retrieved July 28, 2006 from http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookIMMUN.html Gale, Thomas (2005). The Integumentary System. U*X*L Complete Health Resource. Retrieved July 28, 2006. from http://www.faqs.org/health/Body-by-Design-V1/The-Integumentary-System.html Read More