Histology Special Stains: Structure and Cell Components

Revision By Dr. Shaimaa Zaher Lecture of Histology Special stain Iron hematoxylin Janus green Silver stain Best's carmine The stained structure Mitochondria Golgi apparatus Reticular fibers Glycogen granules Sudan III Sudan black Fat cells (adipocytes) PAS (Periodic acid-Schiff reagent) Basement membrane Trypan blue Macrophages Toluidine blue Mast cells Mallory trichrome Collagen fibers Orcein stain Elastic fibers Epithelial tissue Connective tissue Origin Endoderm, mesoderm, ectoderm Mesoderm Cells Closely packed Joined by intercellular junctions Rest on Basement membrane Widely separated Intercellular substance Little Extensive Blood vessels Avascular (no blood vessels) Vascular (penetrated by blood vessels) Nerves Has nerve fibers Has nerve fibers High renewal rate Epithelial tissue Surface Simple Glandular Stratified Myoepithelium Neuroepithelium Simple epithelium Squamous Cubical ▪ Bowman's capsule ▪ Endothelium ▪ Alveoli of lungs ▪ Mesothelium ▪ Thyroid follicles ▪ convoluted tubules of kidney Columnar Ciliated ▪ Uterus ▪ Fallopian tubes NONCiliated ▪ Stomach ▪ Small intestine ▪ Large intestine ▪ Gall bladder Pseudostratified columnar Ciliated with goblet cells Upper respiratory tract (nose, trachea, bronchi) With stereocilia (nonciliated) ▪ Vas deferens ▪ Epididymis Stratified epithelium Squamous Cubical Columnar Transitional (urothelium) Keratinized Epidermis of skin NonKeratinized Oral cavity Esophagus Cornea Vagina Duct of sweat glands Conjunctiva Urinary tract (renal pelvis Ureters Urinary bladder Urethra) Glandular epithelium Endocrine Exocrine Mixed (ductless) (have ducts) (Endocrine & exocrine) Thyroid gland ▪ Salivary glands ▪ Sweat glands Pancreas Myoepithelial cells Neuroepithelial cells • Branched cells • Actin and myosin • Contractile cells • Surround acini of: ✓Salivary glands ✓Sweat glands ✓Mammary glands • Sensory receptors • Their bases are surrounded with sensory nerves • Taste buds of the tongue Specializations of epithelial cells Apical Microvilli Stereocilia Lateral Cilia Zonula occludens Zonula adherens Desmosome (Macula adherens) Gap junction (Nexus) Basal Hemidesmosomes Basement membrane Microvilli Stereocilia Cilia Definition non-motile, finger-like cytoplasmic projections long microvilli motile long hair-like processes Structure actin filaments actin filaments Formed of basal body (nine triplets of microtubules) and shaft (peripheral nine doublets and central two singlets of microtubules) Function increase surface area for absorption increase surface area for absorption Movement of ova (in female genital system) Movement of foreign bodies outside (in respiratory passages) Sites cells lining the small intestine epididymis and vas deferens Uterus, fallopian tubes Upper respiratory tract (nose, trachea, bronchi) Flagella: The same structure of cilia but longer & single (i.e. each cell has one flagellum) Sites: tail of sperm Junctions of epithelial cells Zonula occludens (tight junction) Zonula adherens Desmosome (Macula adherens) Gap junction (Nexus) Hemidesmosome Type occluding junction adhering junction adhering junction communicating junction adhering junction Site (in the cell) -Lateral surface of cells -The most apical junction Lateral surface of cells immediately basal to the tight junction scattered along the lateral surface of cells. lateral surface of the epithelial cells. Basal surface of epithelial cells Structure -encircles the cell like a belt -The two adjacent cell membranes fuse -encircles the cell like a belt -spot like junctions -Plaques with actin filaments -Plaques with intermediate inserted into them filaments (tonofilament) inserted into them Connexins transmembrane proteins form channels (connexons) With central pores Half desmosome (one plaque into which tonofilaments are inserted Intercellular space absent 20 nm 30 nm 2 nm --------------------- Sites (in the body) epithelial cells of small intestine epithelial cells of small intestine epithelial cells of small intestine cardiac and smooth muscles. --------------------- Function barrier preventing passage of substances between cells. Anchoring cytoskeleton of adjacent cells. Provide firm cellular adhesion Anchoring cytoskeleton of adjacent cells. Provide firm cellular adhesion Allow passage of ions and small molecules between cells. Binds the epithelial cells to the underlying basement membrane Basement membrane • Extracellular membrane beneath epithelial cells. • Formed of collagen fibers and glycoproteins • Red line by PAS (Periodic acid-Schiff reagent) • Thick in lining epithelium of skin and trachea CT cells 1- Fixed (resident or permanent cells): 2-Wandering (transient or temporary cells): ➢Originate locally within the CT. ➢Originate from stem cells in the bone marrow, circulate in the blood, and then move into connective tissue where they function. ➢They are stable and long-lived cells. ➢They are motile and short-lived cells. ➢They Include: • Undifferentiated mesenchymal cells • Pericytes • Fibroblasts & fibrocytes • Adipocytes ➢They include: • Macrophages • Mast cells • Plasma cells • Leucocytes UMC Pericytes Origin mother cells of all types of CT UMC Sites In embryo as stem cells In adults around blood capillaries (pericytes) around blood capillaries LM: Shape Nucleus Cytoplasm stellate shaped with cytoplasmic processes pale with prominent nucleolus basophilic Branched cell with cytoplasmic processes central oval basophilic EM Nucleus Cytoplasm Euchromatic free ribosomes central oval actin and myosin free ribosomes -Differentiate into all CT cells -Remain after birth around blood capillaries (pericytes) -adult stem cells (in tissue injury, they differentiate into fibroblasts, endothelial cells and smooth muscle cells) -contractile ability (regulate blood flow through the capillaries). Function Fibroblasts Origin UMC Pericytes (in tissue injury) Sites Nearly in all types of CT LM: Shape Nucleus Cytoplasm Branched cells with cytoplasmic processes Large, pale with prominent nucleolus deep basophilic EM Nucleus Cytoplasm (characters of Protein-secreting cells) Euchromatic Well developed RER, Golgi apparatus & mitochondria No secretory granules Function -Synthesis of CT matrix -Synthesis of growth factors enhancing cell growth. -Healing of the wounds Fibrocytes (Less active fibroblasts) Smaller spindle shaped with fewer processes smaller, darker Pale basophilic Heterochromatic Less organelles (less RER) maintenance of CT matrix Unilocular Fat Cells (White fat cells) Multilocular Fat Cells (Brown fat cells) Site In white adipose C.T. In brown adipose C.T. LM -Shape: Large oval cells. -Nucleus: Peripheral and flattened - Shape: Small rounded cells. -Nucleus: Central and rounded -Cytoplasm: A very thin rim around a single large fat droplet. - In H&E stained sections, fat droplet dissolves and the cells appear as large vacuoles with peripheral nucleus (signet-ring appearance). -Cytoplasm: - Contain many fat droplets of various sizes. -Numerous mitochondria -Mitochondria contain large amounts of cytochrome oxidase, -inner mitochondrial membrane contains transmembrane protein called thermogenin --------------------------------------------Fat stains (Orange) with Sudan III or (Black) with Sudan black. ------------------------------------------Fat stains (Orange) with Sudan III or (Black) with Sudan black. Function 1. Storage of fat to release energy. 2. Heat insulation. 3. Support organs. Heat generation. Macrophages Mast cells Plasma cells Origin blood monocytes hemopoietic stem cells B-lymphocytes Sites ---------------------------------- along the blood vessels abundant in lymphoid tissues LM: Shape Nucleus large irregular cells eccentric, kidney-shaped nucleus oval or rounded central and rounded nucleus oval spherical and eccentric nucleus with a cartwheel (clock-face) appearance basophilic granules that obscure the nucleus. deep basophilic, with -ve Golgi image These granules are metachromatically stained by toluidine blue Cytoplasm specially stained by vital stain e.g. trypan blue EM Nucleus Cytoplasm The cell has pseudopodia Kidney shaped Many lysosomes (characters of protein secreting cells) euchromatic nucleus RER, Golgi apparatus, mitochondria Electron dense secretory granules (Characters of Protein-secreting cells) Euchromatic nuclei RER, Golgi apparatus & mitochondria No secretory granules Function -Phagocytosis -Antigen presenting cells -Secrete growth factors for tissue repair -Mast cells carry surface receptors for IgE -Initiate allergic reaction. Synthesis and secretion of antibodies (humoral immunity) N.B. -Macrophages in connective tissue are called also histocytes -Foreign-body giant cells: are multinucleated masses of fused macrophages surrounding a large foreign body Chemical mediators of mast cells are: Heparin, Histamine, Leukotrienes, and Eosinophil chemotactic factor. Leucocytes include: a. Neutrophils: They migrate to sites of acute inflammation. They are first line of cellular defense against bacteria Dead neutrophils are called pus cells b. Eosinophils: They migrate to sites of allergy and parasitic infection c. Basophils: are functionally similar to mast cells. Mast cells and basophils initiate allergy d. Lymphocytes: They migrate to areas of chronic inflammation. They include two types: ➢ T-lymphocytes: that initiate cell-mediated immunity. ➢ B-lymphocytes: that are responsible for humoral immunity and they give rise to plasma cells. e. Monocytes: that give rise to macrophages