Biomechanics pdf free download
Biomechanics pdf free download
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What is thalassemia? causes, symptoms, clinical features?
Thalassemia Thalassemias are inherited disorders caused by mutations in globin genes that decrease the synthesis of α- or β-globin. Decreased synthesis of one globin results not only in a deficiency of Hb but also in red cell damage that is caused by precipitates formed from excess unpaired "normal" globin chains. The mutations that cause thalassemia are particularly common in Mediterranean, African, and Asian regions in which malaria is endemic. As with HbS, it is hypothesized that globin mutations associated with thalassemia protect against falciparum malaria. Pathogenesis A diverse collection of α-globin and β-globin mutations underlies the thalassemias, which are autosomal codominant conditions. Adult hemoglobin (HbA) is composed of two α chains and two β chains. α chains are encoded by two α-globin genes on chromosome 16. β chains are encoded by a single β-globin gene on chromosome 11. Clinical features vary widely depending on the combination of mutated alleles inherite...
What is hereditary spherocytosis? pathogenesis, morphology, and clinical features.
Hereditary Spherocytosis This disorder stems from inherited (intrinsic) defects in the red cell membrane. Leads to formation of spherocytes — non-deformable cells that are highly vulnerable to sequestration and destruction in the spleen. Usually transmitted as an autosomal dominant trait . A more severe autosomal recessive form affects a small minority of patients. Pathogenesis Caused by inherited defects in the membrane skeleton , a network of proteins stabilizing the lipid bilayer of red cells. Major membrane skeleton protein: spectrin — a long, flexible heterodimer that: Self-associates at one end. Binds short actin filaments at the other. These interactions form a two-dimensional meshwork , connected to transmembrane proteins ( band 3 and glycophorin ) via linker proteins : ankyrin band 4.2 band 4.1 Most common mutations involve: ankyrin band 3 spectrin Pathogenic mutations: Weaken vertical interactions between the m...
What is sickle cell anemia? pathogenesis, morphology, and clinical features.
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Sickle Cell Anemia Hemoglobinopathies are a group of hereditary disorders caused by inherited mutations that lead to structural abnormalities in hemoglobin. Sickle cell anemia, the prototypic hemoglobinopathy, is caused by a mutation in B-globin that creates hemoglobin (HLS) . Numerous other hemoglobinopathies have been described, but these are infrequent and beyond the scope of this discussion. Sickle cell anemia is the most common familial hemolytic anemia. In parts of Africa where malaria is endemic, the gene frequency approaches 30% as a result of a protective effect against Plasmodium falciparum malaria. In the United States, approximately 8% of blacks are heterozygous HbS carriers, and about 1 in 600 have sickle cell anemia. Pathogenesis Sickle cell anemia is caused by a single amino acid substitution in β-globin that results in a tendency for deoxygenated HbS to self-associate into polymers. Normal hemoglobins are tetramers composed of two pairs of similar chains. On average, th...