Body Systems and Medical Terminology 2

Course Introduction This course is a continuation of Body Systems and Medical Terminology 1. You'll continue to learn about various body systems, drug delivery systems, drug administration routes, drug classifications, and commonly used medications for various organ system disorders. You'll also learn basic medication calculations, storage, how to assist patients with administration, and proper documentation.   Course Materials All of your course materials are included in this course experience. You'll find it easiest to study this course by following these steps: Look over the syllabus, paying close attention to the course and lesson objectives. Read each objective. Pay close attention to main concepts and definitions. Complete each assignment as you come to it. When you've completed each section, look over the lesson review. When you're confident you understand the material, complete the lesson review.   Course Objectives By the end of this course, you'll be able to Identify the anatomy, physiology, and diseases and treatments of the integumentary and musculoskeletal systems Identify the anatomy, physiology, and diseases and treatments of the sensory and nervous systems Identify the anatomy, physiology, and diseases and treatments of the immune system Explain how the Six Rights of Drug Administration dictate proper drug administration and storage  

Lesson 1 Overview In this lesson, you’ll learn the basic principles of the integumentary and musculoskeletal systems. The integumentary system is comprised of skin, hair, nails, and various glands. The main function of the integumentary system is to protect your internal organs as well as regulate various secretions and senses. The musculoskeletal system is comprised of bones, joints, and muscles and is mainly responsible for protection, support, and body movements. You’ll also gain knowledge of various diseases of the integumentary and musculoskeletal systems along with available treatment options. While discussing the treatment of these disorders, you’ll learn about the medications used to treat each disorder. Medications listed throughout this lesson are listed as generic names with brand names provided in parenthesis.   Lesson Objectives Describe the anatomy and physiology of the integumentary system Explain integumentary system disorders and common treatment options Explain various components and functions of the musculoskeletal system Describe diseases and treatments of the musculoskeletal system  

Introduction The integumentary system is the body system that provides protective coverage for your internal organs. This integumentary system comprises the skin, hair, nails, sweat glands, and sebaceous (oil) glands. Nails protect the ends of fingers and toes. The skin, hair, sebaceous glands, and sweat glands enable the body to regulate temperature.   Skin Although the skin may appear to be an inactive sheet of tissue, it's a dynamic organ with blood vessels and nerves just like any other organ. The skin is a vital organ that interacts with several other organ systems and has several functions.  Some of the skin's functions are as follows: The skin provides protection from the outer environment. The skin acts as a barrier against foreign pathogens. The skin sends the pain, temperature, pressure, and touch stimuli to the brain. When skin is exposed to the sun, it helps in synthesizing vitamin D, an essential vitamin needed to carry out various body functions. The skin weighs somewhere between seven and nine pounds and takes up, on average, 20 square feet. There are about 300 million skin cells. Each square centimeter of your skin contains about four meters of small branches of the peripheral nerves. This intricate system of nerves allows you to sense very subtle changes in the immediate environment.   Your skin senses touch, pressure, temperature, and pain with different types of nerve fibers. These then send a signal to the brain; the brain decodes the signal and sends a response to the affected body part.   A single centimeter of skin contains meter-long blood vessels. In addition to supplying blood and essential nutrients to the skin, blood vessels allow the skin to help regulate body temperature. Think of the last time you exercised. Whenever you exercise, your heart rate increases to deliver more oxygen to your working muscles. The metabolism of your muscles generates heat. To maintain a stable body temperature, your body must get rid of this extra heat. This occurs mainly through sweating. Evaporation of sweat from your skin carries away heat. The tiny blood vessels in your skin dilate to lose heat, making your skin warm and flushed. In the opposite situation, when you're exposed to extremely cold temperatures, the blood vessels in your skin become more constricted. This shunts blood flow, along with heat, away from skin and inward to protect vital organs. Shivering also is an attempt of your body to produce heat to counteract extremely cold temperatures. *Your skin is an organ that can grow on its own. Skin grafting is commonly used to grow and repair blood vessels, trauma wounds, deep injuries, and burns. Grafting is a process of taking a piece of your own skin or a piece of donor skin and transplanting it to the affected site to grow and repair.   Sweat and Sebaceous Glands Sweat glands are located deep in the dermal layer, very close to the subcutaneous layer of the skin. There are two types of sweat glands: eccrine and apocrine. There are both sweat glands and modified sweat glands. Eccrine sweat glands are numerous, important, and widespread throughout your body. These tiny coiled tubes reach the epidermis through crooked ducts called pores. Eccrine sweat glands produce a watery sweat. Apocrine sweat glands are found primarily in the axillae (armpits) and in the pigmented skin areas around the genitals. The apocrine sweat glands produce a thicker, milky secretion that can be odorous. The milk-producing mammary gland is actually a modified sweat gland, but it doesn't work full time like the sweat gland. The mammary gland secretes milk only after the birth of a child. Other modified sweat glands are the ceruminous glands, located in the skin that lines the external auditory canals (your ears). Instead of sweat, these glands secrete earwax, or cerumen.  Flask-shaped sebaceous glands are also located in the...

Introduction Skin tissue is mainly affected by aging. Aging affects every organ system in the body, but skin changes are the most obvious. As you grow older, the skin loses its elasticity and becomes rough and dry, resulting in wrinkles. Skin can be damaged by sun exposure for long time periods. There are many cosmetic products available to help protect the skin. It's important to apply an appropriate amount of sunscreen frequently if your skin is exposed to the sun. Common disorders of the skin include infections, lesions, pressure ulcers, inflammatory diseases, burns, and acne. Infections can be caused by bacteria, viruses, fungi, and parasites. Allergic reactions can affect the skin and include symptoms such as inflammation, itching, and hives. Injuries and wounds can also traumatize the skin.    Skin Infection Skin infections can be caused by various microorganisms, including bacteria, fungi, viruses, and parasites. An infection can be local, with symptoms of inflammation, pus, blisters, and pain. If untreated, an infection can spread to internal organs and cause systemic infection if it reaches the bloodstream. Signs and symptoms of severe infections include fever, dehydration, and increased white blood cells (WBCs) in the blood. Severe infection might require intravenous antibiotics and prolonged hospitalization. Bacterial infections are caused by bacteria. Staphylococcus is a common bacterium that causes skin infections. Treatment includes topical, oral, or intravenous antibiotics. Severe infections may require drainage of the infected wound and hospitalization. The following are common antibiotics used to treat bacterial infections.                                                                                                                                                                                1) Azithromycin (Zithromax)                                                                                                                                                                                                            2) Bacitracin (Bacitracin)                                                                                                                                                                                                                    3) Bacitracin/Neomycin/Polymyxin B (Neosporin, Triple Antibiotic)                                 ...

Introduction The aging process has a significant effect on bones, joints, and muscles. As you age, the number and function of your bone cells decline—as well as the amount of cartilage in your body, the flexibility of your joints, and the function of your muscles. As the muscle tissue diminishes, it's replaced by fibrous tissue that can't contract appropriately. Thus, the overall strength of muscle declines with age. Many musculoskeletal diseases are the result of physical injury and aging. Balanced nutrition, vitamin supplementation, and regular exercise can help prevent many musculoskeletal disorders.   Injury Disorders Muscles and joints are at a high risk of wear and tear due to daily activities. Overuse of certain muscle groups and performing high-impact activities may also result in injury to your muscles, joints, and tendons. An accident or trauma may cause injury to musculoskeletal organs. The most common type of musculoskeletal injuries are strains, sprains, and spasms. A strain is a tear in a tendon or muscle fiber as a result of overstretching a muscle. Strains usually result from an injury or vigorous exercise without appropriate stretching. The tearing of tendons may result in internal bleeding and bruising. Pain and inflammation may also result at the site of an injury when the muscle is contracted. Preventative measures for strains include careful stretching before and after exercise and gradually warming up intense exercise. It should be noted that a muscle strain isn't the same as a joint sprain.   A sprain is a tear in a ligament as a result of trauma or due to the joint being twisted beyond its normal range of motion. Based on the severity of the injury or trauma to the affected joint, one or more ligaments can be damaged or torn. Ankle and wrist joints are at the highest risk of sprains. A sprained joint, if severe, may require surgical repair and may result in prolonged immobility.  A spasm or cramp is a condition characterized by the undesired, prolonged contraction of a muscle. Spasms can range from painless to extremely painful and can occur after vigorous exercise. For example, you might get calf cramps after playing basketball for too long. Muscle spasms can accompany a joint or bone problem because the surrounding muscles are forced to contract constantly to compensate for any joint dysfunction.   Treatment of musculoskeletal injuries is decided based on the type and severity of the injury. Minor injuries may only require an ice pack to the affected area or over-the-counter pain relievers or anti-inflammatory medications. Severe injuries may require surgical intervention, prolonged immobility, stronger prescription pain medications, and antibiotics.   Bone Disorders Osteomyelitis Osteomyelitis is the infection inside a bone. It's a common complication for diabetes patients with foot infections. Inflammation can reduce the blood supply to the bone, resulting in bone necrosis. Necrosis is the process of tissue death that may require amputation of the affected bone. The symptoms of osteomyelitis are pain or tenderness in the affected area, inflammation, redness, and a high fever. Osteomyelitis requires an intense treatment of intravenous antibiotics in high doses and for a long duration. Severe cases may require surgery to clean out the dead bone tissue in addition to antibiotics. Patients are also prescribed medications to reduce pain and swelling. Common antibiotics used to treat osteomyelitis are: Cefazolin (Kefzol, Ancef) Daptomycin (Cubicin) Linezolid (Zyvox) Vancomycin (Vancocin) Osteoporosis Osteoporosis is a condition characterized by a decrease in total bone mass. Bones are comprised of 50 percent water and 50 percent solids. Vitamins and minerals make up over half of the solid material, and the rest is white fibrous tissue. Healthy bone breaks down old tissue and manufactures new tissue to replace it. In osteoporosis, the new tissue...

Lesson 2 Overview In this lesson, you'll learn the basic components, functions, and diseases of sensory organs and the nervous system. Sensory organs include general sensory receptors as well as special organs, such as the eyes, ears, nose, and tongue. Sensory organs enable you to see, hear, smell, and taste. General sensory receptors throughout your body enable you to feel pressure, pain, touch, vibration, and changes in temperature. The nervous system comprises the brain, the spinal cord, and a vast network of nerves. The nervous system controls all of your bodily functions as well as all voluntary and involuntary movements in your body. This lesson will help you gain knowledge of various diseases and treatment options related to sensory organs and nervous system diseases, including psychiatric disorders. While discussing treatment of these disorders, you'll learn about the medications used to treat each disorder. Medications listed throughout this unit are listed as generic names with brand names provided in parenthesis.    Lesson Objectives Illustrate various sensory organs, common diseases, and treatment options Explain the basic anatomy and physiology of the nervous system Describe common nervous system diseases and psychiatric disorders along with treatment options   Introduction The senses are divided into two groups: general sense organs and special sense organs. Sensory organs include general sensory receptors as well as special organs, such as the eyes, ears, nose, and tongue. Sensory organs enable you to see, hear, smell, and taste. General sensory receptors throughout your body enable you to feel pressure, pain, touch, vibration, and changes in temperature.   General Sense Organs The general sense organs are the tactile receptors, the temperature receptors, the pain receptors, and the proprioceptors. General sense organs enable you to experience touch, pressure, vibration, pain, changes in temperature, and muscle stretch. The receptors for these senses are spread throughout the integumentary system of your body and within some of its internal organs. Tactile Receptors  Tactile receptors bring you information about pressure, touch, and vibration. They're located throughout your skin but are more abundant in areas such as the fingertips and the lips. Temperature Receptors Temperature receptors enable you to sense changes in temperature. Although they're found throughout the body, they're concentrated in the lips, the mouth, and the anus. Pain Receptors Pain receptors are located throughout the skin and within certain internal organs. Some organs, however, are poorly supplied with pain receptors, making it difficult for you to determine where it actually hurts. An example of that is a headache; headaches can be felt due to the pain in the brain, the skull, the neck, or the blood vessels. Proprioceptors These enable you to sense the position of various body parts without looking and to sense whether the body parts are moving and in what direction. This sense of positioning is called proprioception, or kinesthesia. The receptors are located within muscles, joints, and tendons. Once the receptors detect a stimulus such as pain, pressure, or touch, the stimulus is converted into an electrical signal or a nerve impulse. The signal then travels the nerve pathways to the brain, where the sensation is interpreted. After the brain interprets the stimulus, it sends orders back along the nerve pathways to the organs and/or other muscles to react appropriately to the receptor.   Special Sense Organs The special sense organs are the eyes, the ears, the nose, and the taste buds. The special senses are touch, vision, hearing, smell, and taste. Touch is mediated through the integumentary system. The remaining senses are mediated by the eyes, the ears, the nose, and the tongue.  These organs receive sensory signals and transmit to the brain by way of the cranial...

Introduction The nervous system is the most sophisticated and complex body system because it regulates and coordinates the rest of your body systems. It controls every function of your body. Some of these functions are voluntary, such as running, jumping, and climbing. Other functions are involuntary, such as breathing, digesting, and pumping blood. But no matter what the function is, all of your body systems depend on the nervous system. The nervous system is mainly composed of the brain, spinal cord, and nerves. The brain and the spinal cord are referred to as the central nervous system (CNS) and nerves make up the peripheral nervous system (PNS).    Central Nervous System The central nervous system earned its name from its central location in your body, a good location for a system that functions as the communication headquarters. Whether you're awake or not, the central nervous system continuously receives information, makes decisions, and sends information to nerves located throughout your body.   The central nervous system contains the two most important structures in the body—the brain and the spinal cord. These delicate structures are vital to our survival, and therefore have two coverings—an outer covering of bone and an inner covering of membrane. Two types of bone form the outer covering:  1. The cranial bone, which encases the brain 2. The vertebrae, which encase the spinal cord Three distinct layers of tissues, also known as meninges, form the inner covering: 1. Dura mater—a tough outside layer 2. Arachnoid mater—a web of delicate fibers connecting dura mater to pia mater 3. Pia mater—a soft and tender inside layer   In addition to protecting the brain and the spinal cord from injury, the meninges allow nourishment to pass through a complex channel system. The dura mater is a thick, tough membrane that contains channels for blood to pass into the brain tissue. The subdural space below the dura mater contains many blood vessels that carry nourishment to the tissue. Between the arachnoid mater and the pia mater is another space called the subarachnoid space, and this space contains the cerebrospinal fluid. The pia mater layer is made of connective tissues and a rich supply of blood vessels.   Cerebrospinal fluid (CSF) is a built-in shock absorber for the central nervous system. This colorless fluid circulates around and within the brain through the ventricles (cavities in the brain), the central canal of the spinal cord, and the subarachnoid space. The ventricles and the meninges form a dynamic system that regulates the amount of CSF covering the brain. The ventricles produce the fluid which is reabsorbed by the meninges to prevent buildup of excess fluid. Therefore, the meninges and the cerebrospinal fluid not only form a physical layer of protection for the brain but also serve a circulatory role by providing nutrients and removing waste products. The CSF is produced by a collection of blood vessels called the choroid plexus, located within each ventricle. These blood vessels also perform a special function within the brain. They help form what's known as a blood cerebrospinal fluid brain barrier (BCSFB). This barrier helps protect the brain by controlling which substances enter and leave the brain.   Your spinal column is the characteristic that qualifies you as a vertebrate. Inside the spinal column lies the spinal cord, a slightly hollow cylinder of neural tissue, which is attached to the brain stem. Gray matter composes its inner section. The white matter, which composes its outer region, contains sensory and motor neurons to transmit nerve impulses to and from the brain. The spinal cord begins at the medulla and continues down the vertebral column to the level of the second lumbar vertebra. At the lower end of the spinal column is the cauda equina, which is a...

Introduction Nervous system and psychiatric diseases include many complicated disorders involving nerve transmission, neurotransmitters, mood and behavior, and sensory and motor impulse disturbances. The medical specialty of neurology diagnoses and treats nervous system disorders. Psychology and psychiatry diagnose and treat psychiatric diseases. Some nervous system and psychiatric diseases are difficult to diagnose in early stages and may cause severe impairment and long term damage if left untreated. Many medications are available to treat these disorders, but a combination of psychotherapy and behavioral therapy produce the best results in treating behavioral disorders.    Nervous System Disorders and Treatments Because the nervous system is so complex and fragile, it's vulnerable to various disorders. Nervous system disorders may be caused by functional impairments, brain tissue degeneration, vascular abnormalities, trauma, or infections. Aging plays a role in decreased nerve signal reception and conduction. This results in varying degrees of decreased vision, hearing, muscle coordination, confusion, and weakness. Some of the common symptoms of nervous system disorders include tremors, blurred vision, paralysis, irritability, change in respiration and pulse, restlessness, and speech difficulties.   Parkinson's disease is a slowly degenerative disease caused by shrinking levels of the neurotransmitter dopamine. It may result from the loss of dopamine-producing neurons in the brain.   Dopamine is a neurotransmitter vital for the normal functioning of posture control, physical support, and voluntary movement. Causes of Parkinson's disease are unknown, and there's no cure. Medications are used to relieve symptoms of the disease.  The following are four hallmark signs of Parkinson's disease: 1. Resting tremor (shakiness in hands and feet) 2. Muscular stiffness or rigidity  3. Slowing of movements (bradykinesia) 4. Impaired postural reflexes (the most debilitating because it increases the risk of falls)   The following medications are used to relieve Parkinson's disease symptoms: Levodopa/Carbidopa (Sinemet) Entacapone (Comtan) Entacapone/Levodopa/Carbidopa (Stalevo) Benztropine (Cogentin) Rasagiline (Azilect)   Alzheimer's disease (AD) is characterized by loss of memory, poor judgment, and general withdrawal from daily life. The exact causes of this disease are unclear. This disease can be traumatic for family members because the patient's personality changes. One important fact about AD is that it's not a normal process of aging. Early warning signs of Alzheimer's disease include memory loss, difficulty performing familiar tasks, speech impairment, disorientation, and significant mood or behavior changes.  The following medications are commonly used to treat Alzheimer's disease: Donepezil (Aricept) Rivastigmine (Exelon) Galantamine (Razadyne) Memantine (Namenda)   Multiple sclerosis (MS) is caused by an inflammation of the myelin sheath that covers the nerve pathways in the brain and spinal cord. Once the myelin sheath is damaged, nerves are unable to conduct impulses appropriately. Causes of MS are unknown, but some believe a virus is responsible. MS is more common in women than men and occurs more frequently between the ages of 15 and 45. Although steroids and muscle relaxants may help, there's no effective treatment for MS. The symptoms of MS are tingling, numbness, and weakness affecting certain areas of the body. It may also result in loss of balance, poor coordination, shaking or tremors, muscle spasticity, difficulty in speaking clearly, and bladder dysfunction. The following medications are commonly used to treat MS: Glatiramer (Copaxone) Interferon beta-1a (Avonex) Interferon beta-1b (Betaseron) Azathioprine (Imuran) Cyclophosphamide (Cytoxan) Mitoxantrone (Novantrone) Diazepam (Valium), baclofen (Lioresal), and tizanidine...

Lesson 3 Overview In this lesson, you'll learn the basic components, functions, and diseases of the immune system. The immune system is comprised of white blood cells, enzymes, hormones, skin, bone marrow, and the lymphatic system. The immune system is your body’s defense mechanism to protect itself against various infections that can be caused by pathogens such as bacteria and viruses.  In addition, you'll learn in detail about the development and presentation of the most debilitating diseases—HIV infection and cancer. HIV is a virus that can destroy the immune system and expose your body to various infections. Cancer is a disease of uncontrolled cell division and growth that can spread to your entire body, taking over the normal bodily functions. You'll gain knowledge of various treatment options for immune system disorders, HIV infection, and cancer. While discussing treatment for these diseases, you will learn about the medications used to treat each disease. Medications are listed throughout this unit by their generic names, with brand names provided in parenthesis.   Lesson Objectives Illustrate immune system components and functions Describe the common immune system diseases and treatments Explain cancer and chemotherapy medications used to treat cancer   Introduction The immune system is your body's defensive network against any disease-causing microorganisms. It's a complex system composed of various organs, cells, enzymes, and hormones that provide protection against infection-causing microorganisms. Your body has two levels of protection against bacteria, viruses, parasites, and cancer. The integumentary system and certain types of blood cells are part of the first line of defense. Hair and the fluids lining the mucous membranes of the body openings provide physical and chemical barriers against pathogen invasion. Apart from producing an immediate immune response against pathogens, your body has a complex mechanism to produce antibodies against particular pathogens that are successful in invading the physical barrier. These antibodies then protect against future invasion of the same pathogen by initiating a full-blown immune response at the first trigger.    Functions of the Immune System The main function of the immune system is to prevent or decrease the risk of various infections. Individuals with weaker immune systems due to hereditary factors or concomitant diseases such as cancer and human immunodeficiency virus (HIV) infection are at higher risk of contracting life-threatening bacterial, viral, fungal, and parasitic infections. Microorganisms that a normal body is able to fight off easily can overtake patients with compromised immune systems.  Pregnant women have weaker immune systems as a protecting measure against the developing baby in the womb. The body may recognize new cells of the baby as foreign and may initiate an immune-mediated response to reject the pregnancy. Decreased effectiveness of the immune system in pregnant women is crucial, but puts women at risk of infections.  The immune system has a mechanism that differentiates between normal, healthy cells and unhealthy cells. The unhealthy cells may have been invaded by foreign microorganisms such as viruses, bacteria, and fungi, or they may have been damaged by noninfectious conditions such as sunburn and cancer. When the immune system first recognizes specific signals from these unhealthy cells, it immediately activates immune processes to attack these cells. If your immune system is unable to recognize and get activated when there's an invasion of pathogens, serious infections may occur. However, if the immune system gets activated without the invasion of disease-causing organisms, allergic reactions and autoimmune diseases occur. *The immune system is made up of a complex network of numerous cell types that either circulate throughout the body or reside in a particular tissue. Each cell type plays...

Introduction The immune system mainly serves to protect your body from various infections. Its components achieve this goal by being specific for each pathogen, by being mobile to reach all body organs, and by memorizing the antigen to provide future protection. Immune cells possess the ability to replicate themselves to amplify the immune response. Without a healthy immune system, your body is exposed to many pathogens capable of causing severe and fatal infections. Weak or comprised immune systems drastically increase the risk of infections. However, hyperactive or prolonged immune response causes hypersensitivity or allergic reactions. Allergic reactions may be caused by a disease-causing allergen or by any otherwise normal environmental component. Your body can initiate an immune response against your own body cells or tissues, resulting in autoimmune diseases.    Diseases of the Immune System Diseases such as myasthenia gravis (MG), rheumatoid arthritis (RA), insulin-dependent diabetes mellitus (IDDM), multiple sclerosis (MS), and Lupus (SLE) are known to be caused by the body's autoimmune response. Autoimmune diseases can be treated using immunosuppressive medications such as cyclosporine, azathioprine, and mycophenolate. Immunodeficiency is another disease related to the immune system.  Acquired immune deficiency syndrome (AIDS), caused by human immunodeficiency virus (HIV), is one of the most serious immunodeficiency diseases. HIV is a virus that causes AIDS, a disease that suppresses the body's natural immune system. The virus destroys T lymphocytes (T cells) that fight infections, leaving patients prone to deadly infections. In some cases, the immune system is suppressed using medications to protect against autoimmune diseases and certain cancers. It's also sometimes done to prevent organ rejection after an organ transplant.  When HIV infection first began spreading in the United States, it was thought to be an exclusive disease among the homosexual male population. Soon thereafter, it became evident that HIV infection was being passed not only between homosexual males, but also through blood transfusions, intravenous drug use, male-to-female sexual contact, female-to-female sexual contact, mother to baby, and exposure in the workplace from patient to healthcare worker.   Human Immunodeficiency Virus (HIV) Infection HIV is most commonly found in blood, semen, and vaginal secretions. The greatest risk factors for contracting HIV infection are participating in unprotected sexual activity and intravenous drug abuse where a needle is shared with an HIV-positive person. The virus can be passed along from the mother to the fetus or from the mother to the infant during delivery. Before 1985, transmission occurred through transfusion of HIV-contaminated blood products, but this form of transmission has virtually stopped due to blood screenings.  It's important to note that a person can be infected with HIV for years before developing AIDS. During this time, the infected person can unknowingly transmit the virus to others. AIDS is a fatal disease because it's impossible to cure. HIV infection suppresses the immune system so that it can no longer fight diseases and infections, eventually leading to death. There are treatments available now that may prevent the virus from actually developing into AIDS. Even though these HIV medications may not cure AIDS, they're helping patients to live longer. During the early stage of HIV infection, the patient experiences mild symptoms such as fever, diarrhea, sore throat, and muscle aches. The ability to fend off diseases remains quite good.  A mid-stage period of HIV infection is persistent generalized lymphadenopathy, in which enlarged lymph nodes, skin rashes, chronic fatigue, and weight loss occur. Finally, full-blown AIDS strikes, rendering the immune system powerless. The...

Introduction Cells in your body are constantly growing and dividing. Sometimes, cells begin to multiply in an uncontrolled fashion and develop an abnormal tissue or growth. The abnormal cells or growth have no useful physiological purpose in the body and can cause irreparable damage. These abnormal growths are called neoplasms. The study of neoplasms is called oncology. A neoplasm can be benign or malignant. Both types of neoplasm can cause a lump to form in the tissue, called a tumor. Tumor is a word that's used synonymously with neoplasm. A benign neoplasm is sometimes referred to as a benign tumor. A malignant neoplasm is called cancer. Cancer isn't always a solid tumor. Cancer can originate in body cells that are floating around, such as blood cells and lymph cells. These cells aren't fixed to a particular organ or body structure. Abnormalities in these floating cells are even more dangerous because cancer can spread to various body parts much quicker.    Causes of Cancer The following characteristics differentiate benign tumors from cancerous tumors: Benign tumors grow slowly; cancer grows rapidly. Benign tumors are often enclosed by a well-defined membrane border; cancerous tumors are non-encapsulated, with an ill-defined membrane border, and project into surrounding tissues. Benign tumors don't usually cause harm to the body unless they're large and interfere with the proper functioning of surrounding tissue. For example, due to the limited space in the cranium, benign brain tumors may be harmful to the surrounding brain tissue. Malignant neoplasms or cancer cells are always dangerous, no matter where they are, since the cells will travel through blood and lymph to invade tissues near and far. Benign neoplasms don't usually grow back after surgical removal; cancer cells frequently regenerate after surgical removal.   Normal cells can transform into cancerous cells through a process called carcinogenesis. Researchers believe this process occurs in the genetic code of the cells, the deoxyribonucleic acid (DNA) of chromosomes. In normal cell division, a group of genes called proto-oncogenes handle the proteins necessary for that division. In normal DNA, DNA repair genes and tumor suppressor genes can reverse damage in the cells. The DNA repair genes correct any abnormalities in cells before they divide. The tumor suppressor genes control the growth rate of cells, instructing them to kill themselves (apoptosis) if they start multiplying too rapidly or if the DNA repair genes can't fix the defect. If these protooncogenes mutate, they become known as oncogenes. Oncogenes instruct cells to make proteins that result in excessive cell growth and abnormal division. These oncogenes can convert normal cells to cancer cells. If the oncogene has affected the DNA repair genes and the tumor suppressor genes, the cells have no instructions to slow down. Thus, they continue to produce abnormalities in daughter cells faster and faster. Once the genetic material of a cell has transformed, or mutated, the correct genetic code is lost. During mitosis, or cell division, the oncogene parent cell will produce two new abnormal cells instead of healthy cells. The mutated cells grow quickly in number and form a tumor. A change in DNA structure can be passed down to subsequent generations through the transfer of DNA from parents to a fetus.   Some cancers result from a defect in the arrangement of DNA chromosomes in the original egg and sperm that created the individual. A child can be born with a defect in the chromosomes that will cause mutation if activated. The factors that activate a gene are unclear. Some cancers have biological causes, relating to factors such as aging and reproductive history. These changes happen during a person's lifetime. They're called acquired, or somatic, mutations. For instance, the risk of...