Anatomy I + First Aid UNMEB 2023 CM Revision Guide

Mitochondria are the "powerhouses" of the cell - site of aerobic cellular respiration and oxidative phosphorylation, producing ATP. Contain their own DNA and double membrane. The inner membrane's cristae house the electron transport chain. A single cell may contain 1000-2000 mitochondria, especially metabolically active cells like cardiomyocytes. This is the most fundamental and accurate organelle-function pairing in cell biology.

The femoral head (head of femur) is the spherical proximal end that articulates with the acetabulum of the hip bone, forming the hip joint (acetabulofemoral joint). This is a ball-and-socket synovial joint allowing flexion, extension, abduction, adduction, and rotation. The head is covered by hyaline cartilage and receives blood supply from the ligamentum teres and retinacular vessels. Essential for weight-bearing and locomotion.

The hyoid bone is a U-shaped bone in the anterior neck, suspended between the mandible and larynx. It's the only bone in the body that does not articulate directly with any other bone (floats in muscular attachments). Supports tongue and serves as attachment for suprahyoid and infrahyoid muscles. While it's craniofacial in origin, it's not part of the skull proper (neurocranium or viscerocranium). Often fractured in strangulation cases.

Osteoblasts are bone-forming cells derived from mesenchymal stem cells. They synthesize and secrete osteoid (organic matrix of collagen and proteins), which then mineralizes with calcium phosphate to form new bone. Active osteoblasts are cuboidal and line the bone surface. When they become surrounded by matrix, they differentiate into osteocytes (mature bone cells). Osteoblasts respond to mechanical stress (Wolff's law) and hormones (PTH, vitamin D, calcitonin).

The ventrogluteal site (gluteus medius) is the preferred IM injection site in adults as it avoids the sciatic nerve and major blood vessels. The deltoid muscle is used for smaller volumes (1-2 mL) in upper arm. Gluteus maximus (dorsogluteal) is no longer recommended due to risk of sciatic nerve injury. "Biceps" and "triceps" are arm muscles, not gluteal muscles. The question appears to have a typo but the best answer is gluteus medius + deltoid.

AB blood group is the rarest (universal recipient) with prevalence of ~4% in most populations. Group O is most common (~45%), followed by A (~40%), then B (~11%). AB has both A and B antigens on RBCs and no anti-A/anti-B antibodies in plasma. Can receive from any ABO type. Important for blood transfusion planning and emergency management. Rarity makes AB blood donations particularly valuable.

Platelets (thrombocytes) initiate hemostasis through adhesion, activation, and aggregation. When vascular injury occurs, platelets adhere to exposed collagen fibers via von Willebrand factor (vWF), become activated, and release chemical signals (ADP, serotonin, calcium ions, enzymes, prostaglandins) that recruit more platelets. They also provide phospholipid surface for coagulation factors to assemble and initiate the intrinsic and extrinsic clotting cascades, ultimately leading to fibrin formation.

Oxygen is primarily transported bound to hemoglobin within red blood cells (RBCs), not dissolved in plasma. Only about 1-2% of O₂ is carried dissolved in plasma. The vast majority (98%) is bound to hemoglobin's iron-containing heme groups as oxyhemoglobin. This is a critical distinction - oxygen is transported in cells, not plasma. Plasma carries CO₂ (mostly as bicarbonate), nutrients (glucose, amino acids, lipids), hormones, and waste products.

Ventricular systole is the contraction phase where blood is ejected from the ventricles. The left ventricle pumps oxygenated blood into the aorta (systemic circulation), while the right ventricle pumps deoxygenated blood into the pulmonary artery (pulmonary circulation). This creates the systolic blood pressure (top number in BP reading). Atrial systole only tops up ventricles (atrial kick), while diastole is relaxation/filling phase.

Hepatitis B vaccination is mandatory for all healthcare workers and first aiders due to high risk of exposure to blood and body fluids. HBV is transmitted percutaneously and can survive outside the body for 7 days. First aiders may encounter bleeding wounds, making them vulnerable. The vaccine provides >95% protection. WHO recommends 3-dose series (0, 1, 6 months). Hepatitis A is fecal-oral, less relevant. Rubella is vaccine-preventable but lower priority. No HIV vaccine exists yet.

Hypovolaemic shock is the correct term for shock resulting from acute loss of body fluids - whether blood (hemorrhagic), plasma (burns), or other fluids (vomiting, diarrhea). It involves decreased circulating volume → reduced venous return → decreased cardiac output → inadequate tissue perfusion. Characterized by tachycardia, hypotension, cool clammy skin, decreased urine output. Requires fluid resuscitation (crystalloids, blood products) and treatment of underlying cause.

Paralysis is NOT a direct sign of fracture. While a fracture can theoretically cause nerve damage leading to paralysis (especially in spinal fractures), paralysis itself is a neurological deficit, not a musculoskeletal sign. The classic signs of fracture are the "5 D's": Deformity, Discoloration, Dimpling, Denuded skin, and Crepitus (1 C). Tenderness and swelling are cardinal signs. Paralysis suggests nerve/spinal cord injury, which is a complication, not a fracture sign itself.