Cellular Pathology Lecture 1 - Structural features of muscle, bone, and connective tissue Hematoxylin-eosin stain - Isolated from the heart of the blackwood tree, when oxidised it forms complexes with Al3+ and Fe3+ ions, this complex can then stain acidic and negatively charged structures like DNA. Muscles are separated by epimysium. Muscles are composed of fascicles separated by perimysium. Muscle fibers are coated by membranes. The role of the intimate connection is to convert the axon signal into a muscle contraction. Myosin thick filament is surrounded by thin filaments in the A-band. The actin filament is stabilised by tropomyosin filaments wrapped around. Troponin regulates myosin binding to the thin filament in a Ca2+ responsive manner. Troponin is a complex of three regulatory subunits C, I and T. Smooth muscle differs from striated muscles. Structural differences: No transversal tubules, no myofibrils, sarcoplasmic reticulum forms a loose network, thick filaments have no organisation, thick filaments have more cross-bridges, thin filaments are attached to dense bodies that form a network with intermediate filaments composed of desmin, during contraction the cells shorten and twist, and there are no tendons. Functional differences: Ca2+ ions enter from the extracellular fluid, in the sarcoplasm Ca2+ ion binding calmodium activates myosin light chain kinase (an ATPase that initiates contraction), and smooth muscle cells are able to operate over a wide range of distances. Two types of smooth muscle - Tonally active (Iris, vascular smooth muscle), and rhythmically active (Uterus, GI tract, bladder). Connective tissues Most abundant and widely distributed tissue, it forms from the mesenchyme in embryo, variable degree of vascularity (heal time), and can withstand a variety of forces due to being made up of non-living material separating cells. They bind tissues together, provide structural support, protects and insulates other tissues, and has uses in transportation. Structural elements of connective tissues Ground substance - removed during histological procedures, soluble materials and nutrients diffuse through ground substance, fluid, glycoproteins (cell adhesion, fibronectin, laminin), proteoglycans (trap water, viscosity depends on glycosaminoglycan content), and glycosaminoglycans (hyaluronan). Fibers - Collagen (gives high tensile strength), Elastin (gives elasticity), Reticular fibers (networks of type 3 collagen).
Cells - Primary blast cells secrete ground substance and fibers. Fibroblasts (connective tissue proper), Chondroblasts (cartilage), Osteoblasts (bone), Hematopoietic stem cells (blood forming). Bones - Classification by shape (Long bone, Flat bone, Pneumatized bones, Irregular bone, Short bone, and sesamoid bone. Structural elements: Ground substance - Its amount bears an inverse relationship to the age of the bone, proteoglycans, hyaluronan, water. Fibres - Collagen type 1 Cells - Osteoblasts, osteocytes. Mineral crystals - 65% inorganic, primarily hydroxyl-apatite, lie in and around the collagen fibrils in extracellular matrix, contributing to bone hardness. Lecture 2 - Histochemistry 80% of all surgical procedures result in a biopsy needing histological processing, critical in diagnosis, staging, and treatment, and used in the primary diagnosis of all tumours and many other pathophysiological states. Types of sample can include tissues and cells. Cytology samples can be obtained by exfoliation, abrasion (scraping), or aspiration (fine