Histology EX 1 study guide PDF

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Histology EX 1 study guide...

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Histology Exam 1 Chapter 1: Introduction - What is histology? The study of tissues (histos = tissue; logos = treatise); includes all level of microscopic anatomy from tissues down to cells and cell ultrastructure and how the tissues come to form organs and organ systems. - What are tissues? Collections of cells that have similar structure and function - How many major tissues are there in adults? What are they? o Epithelial tissue (epithelium) o Connective tissue o Muscle Tissue o Nervous Tissue - Histology is the bridge between structure and function. - We begin to see how an organ performs its function at the microscopic level

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Microscopy Light microscope: used to examine specimen by transillumination (light through them) Mechanical components of the microscope o Focus adjustment o Mechanical stage o Light source Optical components of the microscope o Condenser § Concentrates the light and uniformly illuminates the specimen o Objective lens o Ocular lens How does a microscope work? o Condenser illuminates specimen and light from said specimen is refracted (bent) by the objective lens to produce a magnified image, which is then magnified again as it passes though the ocular lens and transmitted to the retina of the eye. Total specimen magnification is the product of power of the objective and ocular lens. Microscope power: 4x (scanning power), 10x (low power), 40x (high dry power), 100x (oil immersion) objectives and 10x oculars = TOTAL is 40x, 100x, 400x and 1000x Resolution is a super important part of microscopy o Ability of a lens to produce a clear image; the closer two points are when they can be seen as separate the better the resolution o Limit of microscopes is about 0.1 mu (~1500x) Electron microscope: uses an electron beam to create an image o Limit of resolution is improved by factor of 1000 but max of 150000x Transmission electron microscopes (TEM): Produce 2D image of an ultrathin section by capturing electrons that have passed though the specimen o Useful for studying a cells interior or ultrastructure Scanning electron microscope: Used to make a 3D image of a specimens surface. o A focused bean of electrons is passed over the gold coasted specimens surface

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o Some electrons are reflected (backscatter electrons) while others (secondary electrons) are emitted from metallic coating. These combine to make the 3D pic. Specimen preparation: o Fixation: Specimen is treated with a chemical fixative like formalin that alters its chemical composition and slows its deterioration § Chemical modification can include protein denaturation and cross linking, and preservation of lipids and carbs o Dehydration: Beginning with a 50 to 70% alcohol solution, specimen is bathed with more and more concentrations alcohols to remove water o Clearing: Treatment with xylene makes specimen transparent o Embedding: Specimen is treated with supporting medium like paraffin then cut into thin slices. Then embedded in paraffin as well which allows it to solidify into a block; this allows for fewer distortions when using plastics o Sectioning: The solidified block that contains the specimen is mounted into a microtome which has a steel or glass blade and a mechanism that moves the block a certain distance after each cut, this makes uniform cuts. Freezing microtome may be used for specimens that need to be examined quickly which then make dehydration and clearing unnecessary. o Mounting: Each section is applied to a glass slide o Staining: To provide contrast § The colored portion of some staining solutions is acidic which colorize basic (alkaline, + charged and acidophilic (acid loving)) cellular structures § Basic stains are used to colorize acidic cellular structures which are basophilic (base loving). § Hematoxylin and eosin stain (H&E) is used for most preparations and consists of both basic and acid components. H= basic, E= acid • Stains pink (negative) and purple (positive) § Most stains are aqueous = paraffin must be removed and reapplied before staining the specimen o After staining: specimen is dehydrated again and a coverslip is mounted over for protection and better image production For electron microscopy specimen prep; glutaraldehyde and osmium tetroxide are used as fixatives. Uranyl acetate, lead citrate and/or osmium tetroxide are also used as stains. Tissues are then embedded in plastic prior to sectioning For scanning electron microscopy specimen prep; fixing and dehydration is involved followed by coating with a thin layer of gold which interacts with the electron beam to then produce the image.

Chapter 3: Epithelial Tissues - Epithelial tissues or epithelia cover most surfaces in the body o Grow downward and into deeper tissues which then form glands - Epithelia rests on a basement membrane o This membrane separates them from the underlying connective tissues o Basement membrane is composed of… § Basal lamina: Derived from epithelial cells § Reticular lamina: Produced by fibroblast cells of the connective tissue

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§ Blood vessels don’t penetrate so BM is avascular Epithelia rely on nourishment from capillaries of underlying connective tissues o This connective tissue carries nerves, lymphatic vessels and other structures that support the epithelium o Combination of epithelia and connective tissue create the epithelial membrane Types of epithelial membrane o Mucous membrane: Line surfaces open to the external environment and often secrete mucus (ex: digestive, respiratory, urinary, reproductive tracts = connective tissue here is called lamina propria) o Serous membrane: Line the pericardial- pericardium, pleural- pleura and peritoneal- peritoneum cavities (ventral body cavities); epithelial part is mesothelium o Cutaneous membrane: The skin Function of epithelia- structure depend on their functions o Mechanical protection from forces (ex: epidermis of the skin) o Absorption of substances from lumen (inner portion) of a tubular organ (ex: intestinal epithelium) Luminal surface is usually modified with microvilli to increase surface area and improve efficiency of absorption o Secretion of material (ex: intestinal epithelium). Often contains single celled, mucus secreting goblet cells o Lubrication of surfaces (ex: mesothelium of serous membranes) o Formation of a surface for diffusion (ex: walls of lung alveoli and capillaries) Epithelial terminology o When cell is actually on surface, that surface edge of the cell is called the … free, apical or luminal surface o The sides contacting other epithelial cells are … lateral surfaces o The edge in contact with the basement membrane is the … basal surface o When epithelium has more than one layer the cells closest to the basement membrane are the … basal cells o Epithelia are named based on what? § Number of cell layers § Shape of cells at surface o Types of epithelia: § Simple: Single layer of cells ; all cells contact the basement membrane § Stratified: Two or more cell layers; only basal cells contact the basement membrane o Types of epithelial cells: § Squamous cells: Flat with flattened nuclei § Cuboidal cells: Tall as they are wide with spherical nuclei in cell’s center § Columnar cells: Taller than wide and most have elongated basal nucleus Simple epithelia o Simple squamous epithelium § Single layer of flat cells § Forms the alveoli of the lungs, helps in forming the respiratory membrane though where gases diffuse and glomerular capsules of the kidney where blood filtration occurs

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Simple squamous lining of blood vessels = endothelium Epithelial part of serous membranes that secretes lubricating liquid is the mesothelium o Simple cuboidal epithelium § Single layer of cube-shaped cells § Found in the glands where its involved in secretion § Found in kidney tubules where its involved in secretion and absorption and various other places o Simple columnar epithelium § Single layer of tall cells § Involved in absorption and secretion and often has microvilli along with goblet cells Stratified epithelia o Stratified squamous epithelium § Many levels of cells with superficial layers being flattened § Thick so is general found in places subjected to abrasion o Keratinized stratified squamous epithelium § Found on dry surfaces (ex: the skin) § As basal cells divide – progeny get pushed to surface – undergo changes including accumulation of keratin and death – dead cells form waterproof, microbe proof, abrasion barrier o Nonkeratinized stratified squamous epithelium § Found in moist area of the body not subject to much abrasion § Ex: oral cavity, esophagus, and vagina) o Stratified cuboidal epithelium AND stratified columnar epithelium § Fairly uncommon § Can be found in ducts of some glands with cell height corresponding to the ducts size Other Transitional epithelium o Stratified and can be found lining the renal calyces, urinary bladder, ureters and male urethra o Also referred to as urothelium o Specialized for stretching and forming a protective barrier against the hyperosmotic urine o While relaxed, the number of cell layers appear greater and middle cells are columnar while surface cells are dome shaped and called umbrella cells o Surface umbrella cells are highly specialized are often binucleate § Their apical membranes have thick patches of the outer lipid layer § These plaques are separated by small regions of ordinary membrane that act as hinges and allow cell to fold and unfold whether epithelium is stretched or relaxed § The plaques along intercellular junctions that protect against the hyperosmotic urine Pseudostratified ciliated columnar epithelium (PSCC) o Not truly stratified because all cells are in contact with basement membrane

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o Not all cells reach the surface though, they have varying heights making it look stratified – this is why its called pseudostratified o Considered columnar since the taller cells are columnar o Found in respiratory tract, lining nasal cavity, trachea and bronchi. o Also in male reproductive tract (epididymis and spongy urethra) Goblet cells? o Produce mucus that traps dust and other particles in inspired air and then cilia sweep up the mucus toward the pharynx, where it is swallowed. o Secrete mucinogen, which converts mucin when hydrated; mucinogen is a major component of mucus Glandular epithelium o Specialized for secreting materials o Develop from typical lining epithelium that grows down (invaginates) into deeper embryonic development and isn’t found on the surface. o Exocrine glands: Remain connected to the surface and deliver their secretion to it by way of a duct o Endocrine glands: Lose connection to the surface during development; their secretion diffuses into the blood where its then distributed through the body o Multicellular exocrine glands § Specialized duct cells and secretory cells § Classified according to their ducts and secretory portions § Simple glands: Ducts is unbranched § Compound glands: Duct branches § Tubular glands: Secretory portion is about same size as the duct § Acinar (alveolar) glands: Secretory cells are larger than the duct o Parenchyma of gland: Comprise of the secreting cells and ducts § May have a connective tissue stroma in the gland that supports it o Larger glands have connective tissue capsule on surface that sends branches into the gland and divides it into lobes and lobules o Myoepithelial cells: Associated with some acini; these are contractile epithelial cells that push the glands secretions into the duct § Found in salivary, mammary and sweat glands

Chapter 4: Fibrous Connective Tissue - Two types o Connective tissue proper o Specialized connective tissue - Connective (supporting) tissues: Anchor organs and join the other tissues of the body into a structurally integrated whole; most organs have a CT covering that penetrates and binds the whole organ together o Unlike epithelia, connective tissue has abundant extracellular (intercellular) matrix and few cells o This extracellular (intercellular) matrix consists of protein fibers, a ground substance, and other supporting biochemicals o May be vascular or avascular - Functions of CTP and SCT

Binding and support (ex: ligament) Defense (ex: macrophages, lymphocytes and mast cells of various tissues) Storage (ex: adipose tissue) Protection (ex: adipose tissue) Transport of materials between blood and other tissues (ex: extracellular fluid in loose connective tissue and others ) Embryonic Connective Tissues o Connective tissues in adults are derived from embryonic tissues – mesenchyme which is derived embryonic mesoderm o Mesenchymal cells: Angular or spindle shaped and form a loose mesh that is functional a rudimentary connective tissue with a viscous ground substance with few fibers § Unspecialized with potential to differentiate into cells typical for adult CT § Play a role in tissue repair (along with fibroblasts and pericytes which are found associated with capillaries) o Mucous tissue § Found only in the umbilical cord and few other locations in embryo § Has fibroblasts and very few collagen fibers coursing through a jellylike ground substance in umbilical cord (Wharton’s jelly) Extracellular Matrix of Adult CT o Properties of a CT is largely because of properties of its extracellular matrix (fibers, ground substance, structural glycoproteins) o Ground substance: Amorphous, gel like material composed of charged glycosaminoglycans – GAGs – (mucopolysaccharides) and proteoglycans (mucoproteins) § Both are polymers of disaccharide subunits; their charges make them hydrophilic which results in tissue fluid mixing readily with the ground substance and help create the gel like state § Essential in transport of nutrients and wastes between blood and other tissues. § Not easily visible in histological preparations o Fibers: Made up of proteins and come in two basic types – collagen and elastic § Collagen fibers: Made of protein collagen and the primary fibers of connective tissue • A collagen molecule consists of three polypeptide chains wound in a triple helix • A collagen fiber is made of many collagen molecules packed together in a regular pattern • Most abundant collagen is… Type 1 • Type i: High tensile strength and is flexible but inelastic • Type iii: Thin, branches, formerly known as reticular fibers. Form the framework of the liver, lymphatic tissue and bone marrow. § Elastic fibers: Made up of the protein elastin and glycoprotein fibrillin • Elasticity is an important property for organs that can be deformed and return to their original shape such as large arteries and the skin o o o o o

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Structural glycoproteins: Involved in anchoring and fastening cells to extracellular material including basement membranes

Cells of Adult CT o Cell types in fibrous CT § Fibroblasts • Derived from mesenchymal cells • Responsible for synthesis and maintenance of the matrix • Very under differentiated = can produce all elements of EC matrix • With H&E stain, only their granular, elongated nuclei and nucleoli are easily visible § Macrophages • Derived from blood monocytes • Found in variety of tissues • Function is to phagocytose (engulf) foreign, dead or dying cells along with cellular debris • They are antigen presenting cells (APCs) and they present antigens to lymphocytes as a part of the immune response • Resident (fixed) macrophages are regular inhabitants of a particular tissue while elicited (wandering/free) macrophages circulate the blood and migrate to where they are needed • They are difficult to identify with regular microscopy prep • Characteristics to look for are an irregular shape; a basophilic, finely granular cytoplasm and an oval- kidney shaped nucleus § Mast cells • Originate in the bone marrow • Occupy various connective tissues • Resemble blood basophils but not developmentally related • Large with prominent cytoplasmic membrane bound granules • The granules contain chemicals like heparin, histamine, and chemotactic factors • Degranulation: release of the granules contents § Adipocytes • Derived from mesenchymal cells and maybe fibroblasts • Specialized to store fat • Unilocular fat cells store the fat as a single, large droplet that pushes the nucleus and cytoplasm to the cells periphery • Multilocular fat cells are smaller and store fat in many droplets and have a spherical nucleus § Leukocytes • White blood cells • Various types seen in CT, at sites of infection and inflammation § Lymphocytes • Dark staining nucleus surrounded by thin layer of cytoplasm § Plasma cells • Derived from lymphocytes and they secrete antibodies

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Purplish cytoplasm and an eccentric nucleus Pale region by nucleus is site of Golgi apparatus Neutrophils have granular cytoplasm and segmented nucleus (they are phagocytic)

Types of Adult CT o Classified according to the arrangement and density of fibers o Regular connective tissue: Fibers are oriented in the same direction o Irregular connective tissue: Fibers are oriented in all directions o Loose connective tissue: Occur singly o Dense connective tissue: Occur in bundles and are tightly packed together o Loose areolar tissue: § CT component of serous and mucous membranes § Acts are filler between muscles and between muscles and skin § Collagen and elastic fibers are present along with fibroblasts, mast cells, macrophages, and other CT cells § Blood vessels, lymphatic vessels and nerves and found here as well o Dense irregular connective tissue: § Densely packed collagen bundles oriented in all directions § Vascular and fibroblasts are the predominant cell type § Comprises dermis and capsules of many organs o Dense regular connective tissue: § Poorly vascularized tissue with fiber bundles in parallel fashion § The fiber arrangement makes great tensile strength along their length § Fibroblasts appear elongated between compact fibers § Ex: Tendons Types of Specialized CT o Elastic CT § Abundance of elastic fibers § Specialized for stretching and returning to original shape § Found in lungs and some vertebral ligaments § In elastic arteries, the fibers form compact concentric laminae (sheets) § Elastic fibers in blood vessels are produced by smooth muscle cells instead of fibroblasts o Adipose Tissue § Vascular tissue § Very cellular with litter intercellular material § White adipose tissue • Composed of unilocular adipocytes • Found in subcutaneous regions and serous membranes • Empty cells are seen with standard slide fixing methods since the fat dissolves • Sometimes fat is retained and stained with Sudan red § Brown adipose tissue • Primarily embryonic tissue • By childhood it is all gone and replaced with white adipose • May be found in perirenal region in adults

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Composed to multilocular adipocytes and is much more vascular than white adipose Involved in generation of body heat and important for infants prior to development of shivering response

o Reticular CT § Loose connective tissue § Abundant reticular fibers (Type III collagen) § Fibers hard to distinguish with H&E but visible with silver stains § Forms framework of bone marrow, lymphoid organs and liver sinusoids Chapter 5: Cartilage and Bone - Cartilage and bone are specialized connective tissue with firm to rigid matrix - Cartilage o On joint surfaces o Avascular § Receives nourishment from blood vessels in perichondrium, the fibrous membrane surrounding the cartilage § Perichondrium: Composed of superficial fibrous layer and a deeper chondrogenic cell layer o Appositional growth: Chondrogenic cells differentiate into chondroblasts that secrete new matrix on the cartilage’s surface o Forms framework of the nose, ears, respiratory tree, and part of rib cage o Located between vertebrae o Comprises majority of embryonic skeletal system before being replaces by bone o Begins developing from mesenchyme in chondrification centers § Mesenchymal cells differentiate into chondroblasts which then begin secreting cartilage matrix § When surrounde...