Human health is shaped by the proper functioning of many interconnected systems. Disturbances in the blood, hormones, brain, and digestive system can lead to life-threatening or chronic disorders. This unit explores some of the most important diseases affecting these systems, including their causes, mechanisms, and consequences.
Haematological Disease
A hematological disease is a disorder of the blood. Anemia is the most common type, characterized by low red blood cell count or hemoglobin. Hemophilia is a bleeding disorder caused by a lack of clotting factors.
Anemias
Anemia is a condition where the blood doesn’t have enough healthy red blood cells or hemoglobin, leading to reduced oxygen delivery to the body’s tissues.
- Iron Deficiency Anemia: The most common type of anemia, caused by a lack of iron, which is essential for making hemoglobin. It results in small, pale red blood cells (microcytic hypochromic anemia). Causes include poor diet, blood loss, or impaired iron absorption.
- Megaloblastic Anemia: Characterized by abnormally large, immature red blood cells due to a deficiency of either Vitamin B12 or folic acid. Both are vital for DNA synthesis. A lack of intrinsic factor, a protein needed for B12 absorption, leads to a specific type called pernicious anemia.
- Sickle Cell Anemia: A genetic disease where a mutation in the hemoglobin gene causes red blood cells to become stiff, sticky, and sickle-shaped. These cells can get stuck in blood vessels, blocking blood flow and causing pain, organ damage, and episodes called crises.
- Thalassemia: An inherited blood disorder where the body produces less hemoglobin than normal due to genetic mutations affecting the production of globin chains. The severity depends on the number of mutated genes.
Endocrine System
The endocrine system is a network of glands that produce and secrete hormones, which are chemical messengers that regulate various body functions. When this system malfunctions, it can lead to several disorders, including diabetes, thyroid diseases, and disorders of sex hormones.
Diabetes
Diabetes mellitus is a chronic disease where the body either doesn’t produce enough insulin or can’t effectively use the insulin it produces. Insulin is a hormone made by the pancreas that regulates blood sugar (glucose). Without enough effective insulin, glucose builds up in the blood (hyperglycemia), which can cause serious long-term damage to nerves and blood vessels.
- Type 1 Diabetes: An autoimmune condition where the body’s immune system attacks and destroys the insulin-producing cells in the pancreas. It requires daily insulin injections for survival and typically appears in childhood or young adulthood.
- Type 2 Diabetes: The most common form, where the body either doesn’t produce enough insulin or becomes resistant to its effects. It’s often linked to lifestyle factors like obesity and physical inactivity, and its symptoms develop slowly over many years.
- Gestational Diabetes: Occurs during pregnancy when blood glucose levels rise above normal. It usually resolves after childbirth but increases the risk of the mother developing type 2 diabetes later in life.
Thyroid Diseases
The thyroid gland, a butterfly-shaped gland in the neck, produces hormones that regulate metabolism, heart rate, and body temperature. Thyroid diseases are caused by the gland producing either too much or too little of these hormones.
- Hyperthyroidism (Overactive Thyroid): The thyroid produces an excess of hormones. Common symptoms include weight loss despite an increased appetite, a rapid or irregular heartbeat, anxiety, and heat intolerance. The most common cause is the autoimmune disorder Graves’ disease.
- Hypothyroidism (Underactive Thyroid): The thyroid doesn’t produce enough hormones. Symptoms often include fatigue, unexplained weight gain, cold intolerance, dry skin, and depression. The most common cause is the autoimmune disease Hashimoto’s thyroiditis.
Disorders of Sex Hormones
Sex hormones (estrogen, progesterone, and testosterone) are crucial for puberty, fertility, and sexual function. Disorders can arise from an imbalance in these hormones, affecting both men and women.
- Polycystic Ovary Syndrome (PCOS): A common hormonal disorder in women, characterized by high levels of androgens (male hormones). Symptoms include irregular periods, excess body hair (hirsutism), weight gain, and infertility.
- Hypogonadism: A condition where the sex glands (gonads) produce little or no sex hormones. In men, this can lead to low testosterone levels, causing a decrease in libido, erectile dysfunction, and loss of muscle mass.
- Androgen Insensitivity Syndrome (AIS): A genetic condition where a person with male chromosomes (XY) is resistant to the effects of androgens. The body is unable to respond to testosterone, which can lead to the development of female external sex characteristics.
The nervous system, a complex network of nerves and cells, coordinates actions and sensory information. Disorders of this system can be neurological or psychiatric.
Neurological Disorders
These disorders involve physical changes or damage to the brain, spinal cord, or nerves.
- Epilepsy: A neurological condition marked by recurrent, unprovoked seizures. Seizures are sudden bursts of abnormal electrical activity in the brain. They can cause a wide range of symptoms, including convulsions, loss of consciousness, staring spells, and unusual sensations or behaviors. The cause is often unknown, but it can be linked to genetic factors, head trauma, or infections.
- Parkinson’s Disease: A progressive neurodegenerative disorder primarily affecting movement. It’s caused by the death of neurons in a part of the brain called the substantia nigra, leading to a significant drop in dopamine production. This loss of dopamine results in the main symptoms: tremor (shaking), bradykinesia (slowness of movement), rigidity (muscle stiffness), and impaired balance.
- Stroke: Occurs when the blood supply to part of the brain is interrupted or reduced, depriving brain tissue of oxygen and nutrients. Brain cells begin to die within minutes.
- Ischemic Stroke: The most common type, caused by a blood clot that blocks an artery.
- Hemorrhagic Stroke: Caused by a blood vessel in the brain bursting and bleeding.
- Symptoms are sudden and can include numbness or weakness on one side of the body, trouble speaking, confusion, and loss of balance.
Gastrointestinal System
A peptic ulcer is an open sore that forms on the inner lining of the stomach (gastric ulcer) or the first part of the small intestine, called the duodenum (duodenal ulcer). They occur when the protective mucus layer of the digestive tract is damaged, allowing digestive acids to erode the tissue.