General Pathology: Cell Adaptation

• Pathology is the study of disease, encompassing its causes, mechanisms, progression, and effects.
• Pathology bridges science and medicine by examining tissues, organs, bodily fluids, and the whole body to understand illnesses.
• Pathology is divided into general pathology, concerning basic disease mechanisms, and systemic pathology, focusing on diseases of specific organ systems.

General Pathology

• General Pathology studies the basic reactions of cells and tissues to abnormal stimuli that underlie all diseases.
• These reactions can manifest as adaptations, cell injury, inflammation, or neoplasia.

Cell Adaptation

• Cells adapt to changes in their environment to protect themselves from injury.
• Adaptations include hypertrophy (increase in cell size), atrophy (decrease in cell size), hyperplasia (increase in cell number), metaplasia (change in cell type), and dysplasia (disordered growth).
• Hypertrophy and hyperplasia can occur together and are often due to increased functional demand or hormonal stimulation.
• Atrophy results from decreased workload, loss of innervation, diminished blood supply, inadequate nutrition, or aging.
• Metaplasia involves a reversible change where one adult cell type is replaced by another, often in response to chronic irritation.
• Dysplasia is characterized by abnormal cell growth and differentiation, often considered pre-cancerous.

Cell Injury and Cell Death

• Cell injury occurs when cells are unable to adapt to stress or are exposed to damaging agents.
• Injury can be reversible or irreversible, leading to cell death.
• Common causes of cell injury include hypoxia, ischemia, toxins, infections, and immunological reactions.
• Two main types of cell death are necrosis and apoptosis.
• Necrosis is accidental and unregulated cell death caused by external factors like infection, toxins, or trauma. It induces inflammation.
• Apoptosis is programmed cell death. It's a regulated process involved in normal development and tissue homeostasis and doesn't induce inflammation.
• Key morphological features of necrosis include cellular swelling, membrane rupture, and karyolysis (nuclear dissolution).
• Apoptosis is characterized by cell shrinkage, chromatin condensation, cytoplasmic blebbing, and formation of apoptotic bodies.

Inflammation

• Inflammation is a protective response to injury or infection, aimed at eliminating the cause of injury and initiating tissue repair.
• It involves vascular changes, recruitment of immune cells, and activation of inflammatory mediators.
• Acute inflammation is rapid in onset and characterized by edema, neutrophil infiltration, and vascular changes.
• Chronic inflammation is prolonged and characterized by lymphocyte and macrophage infiltration, tissue destruction, and fibrosis.
• Cardinal signs of acute inflammation include heat, redness, swelling, pain, and loss of function.
• Major components of acute inflammation include vascular changes (increased blood flow and permeability) and cellular events (neutrophil recruitment and activation).
• Inflammatory mediators, such as histamine, prostaglandins, and cytokines, regulate the inflammatory response.
• Outcomes of acute inflammation include complete resolution, abscess formation, fibrosis, or progression to chronic inflammation.
• Chronic inflammation can arise from persistent infections, autoimmune diseases, or prolonged exposure to irritants.
• Granulomatous inflammation is a specific type of chronic inflammation characterized by the formation of granulomas, which are aggregates of macrophages, lymphocytes, and other immune cells.

Tissue Repair

• Tissue repair is the process of restoring tissue architecture and function after injury.
• It involves regeneration (replacement of damaged cells with identical cells) and/or repair (replacement by connective tissue, i.e., fibrosis or scarring).
• Regeneration can occur in tissues with high proliferative capacity, such as the skin and liver.
• Repair occurs when tissue damage is extensive or when cells are unable to regenerate.
• The repair process involves angiogenesis (formation of new blood vessels), fibroblast proliferation, and extracellular matrix deposition.
• Wound healing is a specific type of tissue repair that involves a complex series of events leading to the restoration of tissue integrity.
• Factors that influence wound healing include infection, nutrition, blood supply, and certain medications.

Neoplasia

• Neoplasia is the abnormal and uncontrolled growth of cells, leading to the formation of a tumor or neoplasm.
• Neoplasms can be benign (non-cancerous) or malignant (cancerous).
• Benign neoplasms are localized, well-differentiated, and do not metastasize.
• Malignant neoplasms are invasive, poorly differentiated, and can metastasize to distant sites.
• Cancer is a generic term for malignant neoplasms.
• Carcinogenesis is the multistep process by which normal cells are transformed into cancer cells.
• Genetic mutations, epigenetic changes, and environmental factors contribute to carcinogenesis.
• Oncogenes are genes that promote cell growth and proliferation when mutated or overexpressed.
• Tumor suppressor genes are genes that inhibit cell growth and proliferation; their inactivation can contribute to cancer development.
• Metastasis is the spread of cancer cells from the primary tumor to distant sites, a hallmark of malignancy.
• Diagnosis of neoplasms involves histological examination of tissue samples, as well as imaging studies and molecular tests.
• Treatment of neoplasms may involve surgery, radiation therapy, chemotherapy, targeted therapy, or immunotherapy.

Systemic Pathology

• Systemic Pathology examines diseases affecting specific organ systems.
• Each organ system can be affected by a range of pathological processes, including inflammation, infection, vascular disorders, and neoplasia.

Cardiovascular Pathology

• Includes diseases of the heart and blood vessels.
• Common conditions include atherosclerosis, hypertension, ischemic heart disease, heart failure, and congenital heart defects.
• Atherosclerosis is characterized by the formation of plaques in the arterial walls, leading to narrowing of the arteries and reduced blood flow.
• Hypertension (high blood pressure) can damage blood vessels and contribute to heart disease, stroke, and kidney failure.
• Ischemic heart disease results from reduced blood supply to the heart muscle, often due to atherosclerosis.
• Myocardial infarction (heart attack) occurs when blood flow to the heart is completely blocked, leading to death of heart muscle.
• Heart failure is a condition in which the heart is unable to pump enough blood to meet the body's needs.
• Congenital heart defects are abnormalities present at birth that affect the structure and function of the heart.

Respiratory Pathology

• Concerns diseases of the lungs and airways.
• Common conditions include pneumonia, chronic obstructive pulmonary disease (COPD), asthma, lung cancer, and cystic fibrosis.
• Pneumonia is an infection of the lungs caused by bacteria, viruses, or fungi.
• COPD is a chronic lung disease characterized by airflow obstruction, often caused by smoking.
• Asthma is a chronic inflammatory disease of the airways, characterized by reversible airflow obstruction and bronchospasm.
• Lung cancer is a malignant neoplasm of the lung, often associated with smoking.
• Cystic fibrosis is a genetic disorder that affects the lungs and other organs, leading to mucus buildup and chronic infections.

Gastrointestinal Pathology

• Focuses on diseases of the digestive tract.
• Common conditions include esophagitis, gastritis, peptic ulcer disease, inflammatory bowel disease (IBD), and colorectal cancer.
• Esophagitis is inflammation of the esophagus, often caused by acid reflux.
• Gastritis is inflammation of the stomach lining, which can be caused by infection, autoimmune disease, or certain medications.
• Peptic ulcer disease involves sores in the lining of the stomach or duodenum, often caused by Helicobacter pylori infection.
• Inflammatory bowel disease (IBD) encompasses chronic inflammatory conditions of the gastrointestinal tract, such as Crohn's disease and ulcerative colitis.
• Colorectal cancer is a malignant neoplasm of the colon or rectum, often arising from polyps.

Liver and Biliary Pathology

• Pertains to diseases of the liver, gallbladder, and bile ducts.
• Common conditions include hepatitis, cirrhosis, liver cancer, and gallstones.
• Hepatitis is inflammation of the liver, caused by viral infections, alcohol abuse, or autoimmune diseases.
• Cirrhosis is chronic liver damage characterized by fibrosis and nodule formation, leading to impaired liver function.
• Liver cancer (hepatocellular carcinoma) is a malignant neoplasm of the liver, often associated with cirrhosis or hepatitis.
• Gallstones are hard deposits that form in the gallbladder, which can cause pain and inflammation.

Renal Pathology

• Concerns diseases of the kidneys.
• Common conditions include glomerulonephritis, pyelonephritis, kidney stones, and renal cell carcinoma.
• Glomerulonephritis is inflammation of the glomeruli (filtering units) in the kidneys, often caused by immune-mediated mechanisms.
• Pyelonephritis is a bacterial infection of the kidneys.
• Kidney stones are hard deposits that form in the kidneys, which can cause pain and urinary obstruction.
• Renal cell carcinoma is a malignant neoplasm of the kidney.

Endocrine Pathology

• Addresses diseases of the endocrine glands (e.g., thyroid, adrenal glands, pancreas).
• Common conditions include diabetes mellitus, hypothyroidism, hyperthyroidism, and adrenal tumors.
• Diabetes mellitus is a metabolic disorder characterized by high blood sugar levels, due to insulin deficiency or resistance.
• Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone.
• Hyperthyroidism is a condition in which the thyroid gland produces too much thyroid hormone.
• Adrenal tumors are neoplasms of the adrenal glands, which can cause hormonal imbalances.

Musculoskeletal Pathology

• Focuses on diseases of bones, joints, and muscles.
• Common conditions include osteoarthritis, rheumatoid arthritis, osteoporosis, and bone tumors.
• Osteoarthritis is a degenerative joint disease characterized by cartilage breakdown and inflammation.
• Rheumatoid arthritis is an autoimmune disease that causes chronic inflammation of the joints.
• Osteoporosis is a condition characterized by decreased bone density, leading to increased risk of fractures.
• Bone tumors can be benign or malignant.

Neuropathology

• Encompasses diseases of the nervous system.
• Common conditions include stroke, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and brain tumors.
• Stroke occurs when blood supply to the brain is interrupted, leading to brain damage.
• Alzheimer's disease is a neurodegenerative disorder characterized by progressive memory loss and cognitive decline.
• Parkinson's disease is a neurodegenerative disorder that affects movement, causing tremors, rigidity, and slow movement.
• Multiple sclerosis is an autoimmune disease that affects the brain and spinal cord, causing a range of neurological symptoms.
• Brain tumors can be benign or malignant.