Usmle Step 1 Questions And Answers Full Test Bank With Complete Solution

Ischemic area of Brain {Ans: ACA/MCA/PCA boundary areas (watershed areas*) -Neurons most vulnerable to hypoxic-ischemic insults include Purkinje cells of the cerebellum and pyramidal cells of the hippocampus and neocortex}Elevated Alveolar-Arterial Gradient: Diffusion defects {Ans: -Pulmonary fibrosis -Emphysema -Asbestosis}Testis descent {Ans: - transabdominal phase: descend to lower abd/ pelvic brim= Müllerian inhibitory substance (MIS) is responsible for this phase - inguinoscrotal phase: androgen- and hCG-dependent}Paget's Disease associate Bone Tm {Ans: OSTEOSARCOMA! arising from tibia, femur, humerus, and other bones -pain doesnt resolve with OTC analgesics}t(14;18) {Ans: Follicular lymphoma (BCL-2 activation) [Diffuse Large B-Cell Lymphoma] -bcl-2 inhibits apoptosis normally -in this CA, there is constant anti-apoptotic activity}Polycystic ovary syndrome (PCOS) {Ans: -↑incidence insulin-resistance, obesity, acanthosis nigricans -LH/FSH ratio >3 -↑serum free tesosterone/ androstenedion - ↓serum SHBG; normal to ↓serum FSH -↑secretion LH → follicular hyperthecosis (hyperplasia ovarian thecal cells) → ↑production testosterone, androstenedione → hyperandrogenicity (e.g., hirsutism) -chronic anovulation (less aromatization of androgens to estrogen) -follicular arrest, subcortical cysts -↑conversion androstenedione to estrone → ↑endometrial hyperplasia/cancer, breast cancer risk - oligomenorrhea, hirsutism, obesity, infertility - first line tx: OCPs= Induce regular menses, inhibits ovarian androgen production, increases sex hormone-binding globulin (SHBG) production}