The human body constantly strives for balance, but various diseases can disrupt its structure and function. Unit 4 focuses on three important areas of pathology: inflammatory bowel and liver diseases, bone and joint disorders, and the principles of cancer. Understanding these conditions helps in both prevention and treatment, as they affect millions of people worldwide.
Inflammatory Bowel Diseases (IBD)
Inflammatory bowel diseases (IBD) are chronic conditions that cause prolonged inflammation of the digestive tract. The main types are ulcerative colitis (inflammation of the large intestine and rectum) and Crohn’s disease (inflammation that can affect any part of the gastrointestinal tract from the mouth to the anus). Unlike Irritable Bowel Syndrome (IBS), which is a functional disorder, IBD causes visible damage and inflammation. Symptoms include persistent diarrhea, abdominal pain, rectal bleeding, and weight loss.
Jaundice
Jaundice is the yellowing of the skin and whites of the eyes caused by a buildup of a substance called bilirubin in the blood. Bilirubin is a yellow pigment that is produced when red blood cells break down. Normally, the liver processes bilirubin and excretes it in the bile. Jaundice occurs when there is an issue with this process, indicating a problem with the liver, gallbladder, or pancreas.
Hepatitis (A, B, C, D, E)
Hepatitis is inflammation of the liver, most commonly caused by a viral infection. The different types of hepatitis viruses (A, B, C, D, and E) are spread through different routes and have varying severity.
- Hepatitis A & E: Transmitted through contaminated food or water (fecal-oral route). They are acute, self-limiting infections that don’t lead to chronic disease.
- Hepatitis B, C, & D: Transmitted through contact with infected blood or other bodily fluids (e.g., sexual contact, sharing needles). These can cause chronic infections, which can lead to severe liver scarring (cirrhosis) or liver cancer. Hepatitis D can only infect people who already have Hepatitis B.
Alcoholic Liver Disease
Alcoholic liver disease is liver damage caused by excessive alcohol consumption. It progresses in stages:
- Fatty Liver: The first stage, where fat builds up in liver cells. It is often reversible if alcohol consumption is stopped.
- Alcoholic Hepatitis: A more severe stage with inflammation and destruction of liver cells.
- Cirrhosis: The final, irreversible stage, where the liver becomes severely scarred and loses its function.
Diseases of Bones & Joints
Rheumatoid Arthritis (RA)
Rheumatoid arthritis is a chronic autoimmune disease where the body’s immune system mistakenly attacks the lining of the joints. This causes painful swelling, which can lead to joint deformity and bone erosion. Unlike osteoarthritis, which is wear-and-tear arthritis, RA affects both sides of the body symmetrically (e.g., both hands or both knees).
Osteoporosis
Osteoporosis is a bone disease that causes bones to become weak and brittle. It is characterized by a decrease in bone density and mass. The disease is often called a “silent disease” because there are typically no symptoms until a bone breaks. Fractures most commonly occur in the hip, spine, or wrist. Risk factors include age, being female, a family history of the disease, and a lack of calcium and vitamin D.
Gout
Gout is a form of inflammatory arthritis caused by an excess of uric acid in the blood (hyperuricemia). Uric acid can form sharp, needle-like crystals that accumulate in a joint, causing a sudden and severe attack of pain, swelling, and redness. Gout most commonly affects the joint at the base of the big toe. Attacks can be triggered by a diet high in purines (found in red meat, seafood, and alcohol).
Principles of Cancer
Classification
Cancer is a broad term for diseases characterized by uncontrolled cell growth. Cancers are classified based on the type of cell or tissue they originate from:
- Carcinomas: Cancers that arise from epithelial cells, which line the internal and external surfaces of the body. Examples include cancers of the breast, lung, colon, and prostate.
- Sarcomas: Cancers that originate in connective and supportive tissues, such as bone, muscle, and fat.
- Leukemias: Cancers of the blood-forming tissues, resulting in an overproduction of abnormal white blood cells.
- Lymphomas: Cancers of the lymphocytes (a type of white blood cell) and the lymphatic system.
Etiology and Pathogenesis
- Etiology: The study of the causes of cancer. Cancer is a genetic disease, caused by mutations in a cell’s DNA. These mutations can be inherited from parents or, more commonly, acquired during a person’s lifetime. Acquired mutations can be caused by exposure to carcinogens, which are cancer-causing substances. Examples of carcinogens include tobacco smoke, UV radiation, and certain chemicals.
- Pathogenesis: The biological mechanism by which cancer develops. It involves a multi-step process known as carcinogenesis, where normal cells are transformed into cancer cells. This process involves mutations in two main types of genes:
- Proto-oncogenes: Genes that normally promote cell growth. When mutated, they become oncogenes, which can cause uncontrolled cell growth.
- Tumor Suppressor Genes: Genes that normally inhibit cell growth. When inactivated by mutation, they lose their ability to regulate cell division, allowing the cell to grow and divide uncontrollably.