Special Pathology

The Endocrine System 1. Introduction The human body is regulated by two main systems: Endocrine system Nervous system A third system called the  Neuroendocrine system  connects the two and plays a key role in hormonal control. 2. Neuroendocrine System This system includes cells that produce hormones with both nerve-like and gland-like functions. These cells are called  APUD cells  (Amine Precursor Uptake and Decarboxylation). Major Neuroendocrine Cells and Their Locations : Gastrointestinal mucosa  → Peptide hormones Sympathetic ganglia  → Amines Adrenal medulla  → Epinephrine & Norepinephrine Thyroid parafollicular (C) cells  → Calcitonin Islets of Langerhans (Pancreas)  → Insulin Atrial cells (Heart)  → Atrial natriuretic peptide (ANP) Other Non-Endocrine Hormone-Like Substances : Acetylcholine ,  dopamine  (neurotransmitters) Erythropoietin ,  Vitamin D3  (from kidneys) 3. Major Endocrine Organs The endocrine s...

🧠 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...