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Pathophysiology of Otitis Media: Otitis media (OM) is an inflammatory disorder of the middle ear cavity that commonly develops following Eustachian tube dysfunction, often in association with an upper respiratory tract infection. It may involve accumulation of fluid, inflammation, and infection within the middle ear. The condition is particularly common in children because their Eustachian…
Pathophysiology of Otitis Externa: Otitis externa is an inflammatory or infectious condition of the external auditory canal, commonly known as “swimmer’s ear.” It occurs when the protective mechanisms of the ear canal are disrupted, allowing microorganisms to multiply and cause inflammation. The most common bacterial cause is Pseudomonas aeruginosa, although other bacteria and fungi may…
Pathophysiology of Myopia: Myopia (short-sightedness) is a refractive error in which a person can see nearby objects clearly, but distant objects appear blurred. In myopia, light rays from a distant object are focused in front of the retina rather than directly on the retina. Step 1: Normal Refraction of Light Normally, light entering the eye…
Pathophysiology of Cataract: Cataract is a condition in which the normally transparent crystalline lens of the eye becomes progressively opaque, resulting in reduced transmission of light to the retina and causing blurred or decreased vision. Cataract develops because of structural and biochemical changes in lens proteins, particularly crystallins, along with oxidative stress, disruption of lens…
Pathophysiology of Glaucoma: Glaucoma is a group of progressive eye disorders characterized by damage to the optic nerve, particularly the retinal ganglion cell axons, leading to characteristic visual field loss. The major risk factor is often increased intraocular pressure (IOP), although glaucoma can also develop with IOP within the statistically normal range. The disease is…
The Peripheral Nervous System (PNS) is the part of the nervous system that lies outside the brain and spinal cord. It forms an important communication network between the central nervous system (CNS) and the rest of the body. The PNS carries sensory information from receptors in the body to the CNS and transmits motor commands…
Pathophysiology of Iron Deficiency Anemia: Iron deficiency anemia (IDA) is the most common nutritional deficiency disorder and one of the most common causes of anemia worldwide. It develops when the body’s iron requirement exceeds iron availability for a prolonged period, resulting in depletion of iron stores, impaired hemoglobin synthesis, reduced red blood cell production, and…
Pathophysiology of Megaloblastic Anemia: Megaloblastic anemia is a type of anemia caused by impaired DNA synthesis, resulting in abnormal maturation of hematopoietic cells, particularly erythroid precursors in the bone marrow. The two major nutritional causes are vitamin B12 (cobalamin) deficiency and folate (vitamin B9) deficiency. The characteristic feature is nuclear-cytoplasmic asynchrony: cytoplasmic maturation continues relatively…
Mechanism of Inflammation: Inflammation is a protective biological response of living, vascularized tissues to harmful stimuli such as infection, tissue injury, trauma, chemical irritation, toxins, and foreign bodies. Its primary purpose is to eliminate the initial cause of injury, remove damaged cells and tissues, and initiate tissue repair. Inflammation is not itself a disease. It…
Rh Factors and Blood Transfusion: The Rh blood-group system is one of the most important blood-group systems in transfusion medicine after the ABO system. The term Rh factor most commonly refers to the D antigen, a protein present on the surface of red blood cells in some individuals. People who possess the D antigen are…