Special Pathology

🧠 Central Nervous System (CNS) 🧩 1. Overview CNS includes : Brain and spinal cord Protected by : Skull and vertebrae (rigid compartments) Average brain weight : Males: ~1400 gm Females: ~1250 gm Main divisions of brain: Cerebrum – largest part Cerebellum – smaller, posterior part No lymphatic drainage in brain 🧬 2. Types of CNS Tissues Tissue Type Origin Examples Neuroectodermal Ectoderm Neurons & neuroglia Mesodermal Mesoderm Microglia, meninges, blood vessels 🧠 3. Neurons Functional unit of CNS Do not divide after birth → damage is irreversible Parts : Cell body (Perikaryon) – contains nucleus, Nissl bodies Axon – sends signals Dendrites – receive signals Special features: Nissl substance : RNA + rough ER (basophilic) Other structures : Neurofilaments, lipofuscin, synaptic vesicles Neuromelanin : Found in substantia nigra neurons Responses to Injury : Central chromatolysi...

The Musculoskeletal System The skeleton is made of cartilage and bone . Cartilage helps in growth and repair of bone and forms joints . Bone provides support , movement , and acts as a calcium reservoir . Human body contains 206 bones which can be long , flat , or tubular . Normal Structure of Bone Two Types of Bone: Cortical (Compact) Bone – 80% of skeleton Dense outer shell Strong and rigid Contains osteons with Haversian canals Trabecular (Cancellous) Bone – 20% of skeleton Spongy with bone trabeculae Involved in mineral balance Histology of Bone Bone Cells and Matrix: Osteoblasts Bone-forming cells Produce bone matrix (osteoid) Marker: ↑Alkaline Phosphatase Active in growth, fracture healing Osteocytes Mature osteoblasts trapped in matrix Reside in lacunae Help maintain bone Woven vs. Lamellar Bone: Woven bone = immature, random collagen (children, fractures) Lamellar bone = mature, organ...