Normal Histology PDF

NORMAL HISTOLOGY Hierarchical Organization of Living Matter 4 Basic Tissues ◦Epithelial Tissue ◦Connective Tissue ◦Muscle Tissue ◦Nervous Tissue  Embryonic Origin of Tissues ◦ Conception – sperm and egg cell merge forms zygote ◦ Cleavage – cell division after zygote has formed ◦ Tiss...

NORMAL HISTOLOGY Hierarchical Organization of Living Matter 4 Basic Tissues ◦Epithelial Tissue ◦Connective Tissue ◦Muscle Tissue ◦Nervous Tissue  Embryonic Origin of Tissues ◦ Conception – sperm and egg cell merge forms zygote ◦ Cleavage – cell division after zygote has formed ◦ Tissue appear within first 2 months of embryonic development ◦ Blastocyst ◦ Gastrulation – reorganization of cells into 3 primary germ layers  3 Germ Layer ◦Ectoderm – is the outermost layer of the three germ layers ◦Mesoderm – is the middle of the three primary germ layers of embryo ◦Endoderm – is the innermost layer of the three germ layers. Germ Layer Derivatives 4 Basic Tissues ◦Epithelial Tissue – derived from the 3 germ layers ◦Connective Tissue – derived from mesoderm ◦Muscle Tissue – derived from mesoderm ◦Nervous Tissue – derived from ectoderm  Histogenesis Process of germ layers differentiating into different tissues 4 BASIC TISSUES 4 Basic Tissues ◦ Epithelial Tissue – covers body surfaces, lines body cavities, and forms glands ◦ Connective Tissue – underlies or supports the other three basic tissues, both structurally and functionally ◦ Muscle Tissue – made up of contractile cells and is responsible for movement ◦ Nervous Tissue – receives, transmits, and integrates information from outside and inside the body to control the activities of the body Epithelial Tissue ◦ Avascular ◦ Covers and lines surface and forms glandular tissues 3 Principal Characteristics: ◦ Cells are close to each other ◦ Membranes or sheets of cells ◦ Cells are attached to a basement membrane ◦ Exhibit functional and morphologic polarity. ◦ Apical Surface: Free surface of epithelial tissue, Lateral Domain, & Basal Domain ◦ Specializations: ◦ Cilia ◦ Microvilla ◦ Stereocillia Classification of Epithelial Tissue Classification: 1. Cell Shape (columnar, cuboidal, squamous) ◦ Columnar – when the height of the cell appreciably exceeds the width ◦ Cuboidal – when the width, depth, and height are approximately the same ◦ Squamous – when the width of the cell is greater than its height 2. Arrangement (simple, stratified) ◦ Simple – when it is one cell layer thick ◦ Stratified – when it has two or more cell layers Classification of Epithelial Tissue Two special categories of epithelium: 1. Pseudostratified epithelium – appears stratified but are actually a simple epithelium 2. Transitional epithelium (Urothelium) – is a stratified epithelium ◦ Urothelium – term applied to the epithelium lining the lower urinary tract Epithelial Tissue: Apical Surface Specialization ◦ Microvilli – finger-like cytoplasmic projection that greatly increase the free cell surface area. ◦ Stereocilia – unusually long, immotile microvilli, limited to the epididymis, proximal part of ductus deferens of the male reproductive system, and sensory cells of the inner ear. ◦ Cilia – hair-like extensions of the apical plasma membrane present on nearly every cell in the body. ◦ Motile Cilia ◦ Primary Cilia (Monocilia) – immotile solitary projections ◦ Nodal Cilia – important role in early embryonic development Functions of Epithelial Tissue Diverse epithelial functions: ◦ Secretion – in the columnar epithelium of the stomach and the gastric glands ◦ Absorption – in the columnar epithelium of the intestines and PCT in the kidney ◦ Transportation – transport of materials or cells along the surface of an epithelium (cilia or pinocytosis or endocytosis) ◦ Mechanical protection – in the stratified squamous epithelium of the skin and the transitional epithelium ◦ Receptor function – to receive and transduce external stimuli (taste buds, olfactory epithelium, retina). Epithelial Tissue: Gland 2 Major Group of Glands according to products release: ◦ Exocrine glands – secrete product onto a surface directly or through epithelial ducts or tubes that are connected to a surface. ◦ Merocrine secretion – secretory product is delivered in membrane- bound vesicles to the apical surface of cell by exocytosis ◦ Apocrine secretion – secretory product is released in the apical portion of the cell in vesicles containing a thin layer of cytoplasm ◦ Holocrine secretion – secretory product is released by cell debris from the dying secretory cell ◦ Endocrine glands – ductless system that secrete products into the connective tissue, which they enter bloodstream to reach their target cells. Epithelial Tissue Connective Tissue ◦ Most Abundant ◦ Vary in appearance and function ◦ Main functions: Bind, Protect and Support ◦ Vascularized except cartilage Components of CT: ◦ Cells ◦ Fixed – fibroblast, adipocyte ◦ Wandering – macrophage, mast cells ◦ Extracellular Matrix Connective Tissue: Cells Fibroblast – most common cells in CT proper, produce and maintain most of tissue’s extracellular components – in adults, fibroblast rarely undergo division – involved in wound healing (myofibroblast) ◦ Secrete fibers; as well as GAGs, proteoglycans, & glycoproteins ◦ 3 main types of fiber ◦ Collagen – most abundant; major product of fibroblast ◦ Reticular – found in delicate CT of many organs ◦ Elastic – rubber like properties Connective Tissue: Cells Adipocyte – fat cells found in the CT of many organs. – specialized for cytoplasmic storage of lipid as neutral fats, or less commonly for the production of heat Adipose CT – tx w/ large population of adipocytes, serves to cushion and insulate the skin and other organs Connective Tissue: Adipose Tissue White Adipose Tx ◦ found in many organs throughout the body; typically forming about 20% of the body weight in adults ◦ adipocytes of white fat are typically very large cells; contain primarily one large lipid droplet (unilocular) Brown Adipose Tx ◦ comprises up to 5% of the newborn body weight but smaller amounts in adults ◦ Adipocytes are smaller and contain many small lipid droplets (multilocular) Connective Tissue: Cells Macrophages (Histiocytes) – have highly developed phagocytic ability and specialize turnover of protein fibers and removal of apoptotic cells, tissue debris, other particulate abundant at sites of inflammation. Mast Cell – irregularly shaped cell function in the localized release of many bioactive substances important in the local inflammatory response (heparin, histamine, serine proteases, chemotactic factors) Connective Tissue: ECM Extracellular matrix – major constituent of CT –consist of different combinations of protein fibers (collagen, reticular, elastic fibers) cells and ground substance. Ground substance – is a highly hydrated (much bound water), transparent, complex mixture of macromolecules: proteoglycans, glycoproteins, glycosaminoglycans (GAGs) that resists force of compresion Connective Tissue: Ground Substance GAGs: mucopolysaccharides ◦ Repeating disaccharide units (uronic acid and hexosamine) ◦ Largest, most unique type is Hyaluronic acid ◦ Important in diffusion and lubrication ◦ GAGs found in Proteoglycans (dermatan SO4, chondroitin SO4, keratan SO4, and heparan SO4) Connective Tissue: Ground Substance Proteoglycans ◦ Core protein where different GAGs are covalently attached ◦ Aggrecan (important proteoglycan, dominant in cartilage) ◦ Also bind and sequester signaling proteins (fibroblast growth factor) Connective Tissue: Ground Substance Multiadhesive Glycoproteins ◦ Attached CHO and CHON predominates ◦ Adhesion to substrates ◦ Fibronectin, laminins Connective Tissue: Ground Substance Interstitial/ Tissue Fluid: Free Fluid ◦ Similar to plasma ◦ Hydrostatic Pressure: Pumping action of the heart ◦ forces water out the capillary wall ◦ Osmotic Pressure: Due to plasma proteins ◦ draws water back into the capillaries Connective Tissue: 3 Main Types of Fibers ◦Collagen ◦Elastic ◦Reticular Connective Tissue: Collagen ◦ Most abundant protein; Large Fibers ◦ Great tensile strength ◦ Produced by different cell types ◦ 28 types of collagen (designated as roman numerals) Connective Tissue: Catergories of Collagen ◦ Collagens that form long fibrils ◦ Type I Collagen fibers: tendons, organs, capsule and dermis ◦ Collagens that form Anchoring Fibrils ◦ Type VII: anchoring collagen; Bind basal lamina to reticular fibers ◦ Collagens that form Networks ◦ Type IV Collagen: major structural component of the basal lamina Connective Tissue: Elastic Fiber ◦ Thinner and intermediate fibers made up of elastin and fibrillin ◦ Branching fibers that allow for stretch and recoil ◦ May be stretched up to 150% of their resting length ◦ Interspersed with collagen Connective Tissue: Reticular Fiber ◦ Extremely thin ◦ Consists mainly of collagen type III ◦ Forms networks of very thin and highly glycolysated fibers ◦ Abundant in parenchymal cells of organs and hematopoietic organs ◦ Stain black with silver salts ◦ Argyrophilic fibers Connective Tissue: CT Cells & ECM Classification of Connective Tissue 4 different types ◦Connective Tissue Proper ◦Cartilage ◦Bone ◦Blood All posses a small number of cells surrounded by an extracellular matrix (ECM) Connective Tissue: CT Proper Loose (Areolar) CT ◦ well vascularized, flexible, and not very resistant to stress ◦ fewer fibers but more cells Dense CT ◦ resistance and protection ◦ predominance of collagen fibers ◦ dense regular or dense irregular ◦ more fibers but fewer cells Connective Tissue: Loose (Areolar) CT ◦Very common type of CT ◦Supports epithelial tissues, forms a layer around blood vessels and fills the spaces between muscle and nerve fibers ◦Contains all the CT components ◦ fibroblasts and macrophage (numerous) ◦ Fibers (elastic and collagen) ◦ Flexible, well vascularized but not very resistant to stress Connective Tissue: Dense CT ◦Provide better resistance and protection ◦Fewer cells and more fibers (collagen) ◦ Dense Regular: fibers arranged in a definite pattern ◦ Dense Irregular: fibers arranged without definite orientation Connective Tissue: Dense Regular CT Collagenous ◦Consist mainly of collagen fibers arranged in parallel patterns ◦Present only in tendons and ligaments ◦Provides attachment Connective Tissue: Dense Regular CT Elastic ◦Consist mainly of elastic fibers arranged in parallel patterns ◦Present in artery, aorta, left and right ventricles ◦Ability to recoil for easy blood flow Connective Tissue: Dense Irregular CT ◦Consists of collagen fibers randomly arranged and few fibroblast ◦Dermis of skin and capsules of many organs (pericardium of the heart), perichondrium of cartilage, periosteum, dermis ◦Provides strength Connective Tissue: Cartilage ◦Avascular, fibrous connective tissue ◦Firm Consistency of ECM (Gel-Like) ◦Bear Mechanical Stress without permanent distortion ◦Chondrocytes embedded in the ECM ◦Support soft tissue ◦ Assists in the development of long bones Connective Tissue: Cartilage ◦Type of Cartilage a. Hyaline b. Elastic c. Fibrocartilage Connective Tissue: Hyaline Cartilage ◦Most abundant in the body ◦Serves as temporary skeleton in the fetus ◦Rubbery and tough matrix ◦Bluish white and translucent ◦Trachea, Larynx, Costal Cartilage ◦Provides smooth surface for movement of joints ◦Flexibility and support Connective Tissue: Hyaline Cartilage ◦ Matrix: amorphous GS; proteoglycans (Proteoglacan + Chondronectin); Collagen (Type II) embedded in chondronectin ◦ Perichondrium – dense irregular CT surrounding a cartilage ◦ Chondroblast – manufacture the cartilage matrix ◦ Chondrocyte – mature cells embedded within lacunae in the matrix (ovoid or spherical in isogenous groups) Connective Tissue: Elastic Cartilage ◦Contains elastic fibers ◦Yellowish color ◦Found in external ear, auditory tubes, epiglottis ◦Function = gives support, maintains shape, allows flexibility ◦Less prone to degeneration than hyaline Connective Tissue: Fibrocartilage Cartilage ◦Intermediate between dense CT and Hyaline CT ◦Contains bundles of collagen in the matrix that are usually more visible under microscopy ◦Found in the pubic symphysis, intervertebral discs, and attachments of certain ligaments ◦Function = support and fusion, and absorbs shocks ◦Do not possess distinct perichondrium Connective Tissue: Formation, Growth & Repair of Cartilage ◦ All forms of cartilage form from embryonic mesenchyme a. Interstitial growth – results from cell division of preexisting chondrocytes b. Appositional growth – results from the differentiation of chondrogenic cells in the perichondrium ◦ Repair or replacement of injured cartilage is very slow and ineffective due to avascularity and low metabolic rate Connective Tissue: Bone ◦Main constituent of the adult skeleton (206) ◦Mineralized Tissue ◦Functions: ◦ Support soft tissues and provides attachment ◦ Protects internal organs ◦ Stores minerals ◦ Hematopoiesis Connective Tissue: Bone Chemical Composition of the Bone Matrix 1. Inorganic (non-living) components = hardness and rigidity ◦ 65% dry weight ◦ Primarily hydroxyapatite (Ca10(PO4)6(OH)2) 2. Organic (living) components = tenacity, elasticity, resilience ◦ Type 1 collagen, GS of chondroitin sulfate and keratan sulfate Connective Tissue: Bone Cells 1. Osteoprogenitor cells ◦ Embryonic, Spindle shaped in the periosteum and endosteum ◦ Differentiate into osteoblast 2. Osteoblast ◦ Synthesis of type I collagen, proteoglycans and glycoproteins ◦ Osteocalcinin – bone mineralization ◦ Osteopontin – sealing zone ◦ Osteonectin – bone mineralization ◦ Bone sialoprotein – binding osteoblast to ECM Connective Tissue: Bone Cells Osteoblast ◦ Synthesis of components of bone matrix (organic and inorganic) ◦ Active stage: cuboidal to columnar shape, basophilic cytoplasm ◦ Location: bone matrix surface ◦ PTH: controls osteoblast activity Connective Tissue: Bone Cells Osteoblast ◦ Mature bone cells ◦ enclosed in a lacuna ◦ almond shaped; reduced organelles ◦ cytoplasmic process extends through canaliculi ◦ communicate with each other via gap junctions Connective Tissue: Bone Cells Osteoclasts ◦ Large, motile multinucleated cells ◦ 4 regions ◦ Basal region ◦ Site of active bone resorption: ruffled border ◦ Clear zone surrounds the Howship Lacuna ◦ Vesicular zone – with exocytotic and endocytotic vesicles Connective Tissue: Bone The Periosteum ◦Layer of non calcified CT except at synovial articulations and muscle attachment ◦Distribute blood vessels to bone The Endosteum ◦Lines the marrow cavities ◦Supplies osteoprogenitor and osteoblasts Connective Tissue: Bone Classification Gross Observation a. Compact Bone b. Cancellous/ Spongy Bone Microscopic observation a. Primary Bone Tissue: Woven Bone ◦ Immature and temporary ◦ Many osteocytes ◦ Low mineral content ◦ Replaced by secondary bone b. Secondary Bone: Mature; found in adults ◦ Lamellar bone Connective Tissue: Bone Classification Short Bones - cubical - spongy bone enclosed by compact bone shell ex: bone of wrist and ankle Connective Tissue: Bone Classification Long Bones - cylindrical shape - main shaft : diaphysis, end : epiphysis ex: bones of the limbs Connective Tissue: Bone Classification Flat Bones - thin and flat - two plates (compact) enclose middle layer (spongy) ex: ribs, scapula Connective Tissue: Bone Classification Irregular Bones - irregular/ varied shapes (cannot be classified) - spongy interior, compact exterior ex: vertebrae, some bones of the skull Connective Tissue: Blood Overview of Blood ◦ Red fluid that circulates inside blood vessels ◦ circulates in a closed system of vessels ◦ Consists of formed elements (45%) and a fluid component called plasma (55%) ◦ Volume of blood in an average human adult is 5 to 6L ◦ Have short life spans and are continuously replaced by hemopoiesis Connective Tissue: Blood Functions of Blood ◦ Transports nutrients, waste products, hormones, protein, ions, O2, CO2 and formed elements ◦ Regulates body temperature ◦ Assists in the regulation of osmotic and acid-base balance ◦ Protection (Immune defense) ◦ Prevents excessive blood loss (clot formation) Connective Tissue: Blood Plasma ◦ 90% water, 9% organic compounds, 1% inorganic salts, dissolved gases and nutrients ◦ Main Plasma Proteins ◦ Albumin, a,b,y-Globulin, Fibrinogen, Complement CHON Serum ◦ Yellowish fluid, similar to plasma but lacks fibrinogen and clotting factors Connective Tissue: Formed Elements of Blood Erythrocytes ◦ Life span of 120 Days ◦ Biconcave shape ◦ Hgb for oxygen delivery Leukocytes ◦ Defense against foreign substances ◦ Granulocyte (PMN) ◦ Agranulocytes Thrombocytes ◦ Fragmentation of the megakaryocytes ◦ Anucleated, disk-like cell fragments Connective Tissue: Hematopoiesis Yolk sac Phase ◦ 3rd week of gestation Hepatic Phase ◦ Second Trimester “Liver” Bone Marrow Phase ◦ Second Trimester “Bone Marrow” Post Natal Hemopoiesis ◦ Involves three classes of cells: stem cells, progenitor, and precursor Connective Tissue: Hematopoiesis Stem Cell ◦ Self renewal; undergo enormous proliferation ◦ Can differentiate into multiple cell lineages ◦ Present in circulation (as null cells) and in BM Progenitor Cells ◦ Reduced potentiality and are committed to a single cell lineage ◦ Proliferate and differentiate into precursor cells; indistinguishable from stem cells Precursor Cells ◦ Are all cells in each lineage that display distinct morphological characteristics Muscle Tissue ◦Composed of cells that optimize the universal cell property of contractility Skeletal Muscles Cardiac Muscle Smooth Muscle Muscle Tissue ◦Sarcoplasm – cytoplasm of muscle cells ◦Sarcoplasmic reticulum – smooth ER ◦Sarcolemma – muscle cell membrane and its external lamina Muscle Tissue: Skeletal Muscle ◦Skeletal Muscle – consists bundle of very long muscle fibers, cylindrical multi-nucleated cells with cross-striations. – contraction is quick, forceful, and usually under voluntary control. Skeletal muscle begins to differentiate when mesenchymal cell becomes myoblasts. Align and fuse together to make longer multinucleated tubes called myotubes. Synthesize protein to make up myofilaments (muscle fibers) Muscle Tissue: Organization of Skeletal Muscle ◦Epimysium – external sheath of dense irregular connective tissue, surrounds the entire muscle ◦Perimysium – thin connective tissue layer that immediately surrounds each bundle of muscle fibers termed fascicle ◦Endomysium – a very thin, delicate layer of reticular fibers and scattered fibroblasts within fascicle that surrounds the external lamina of individual muscle fibers (basal lamina) All three layers plus the dense irregular CT of the deep fascia, which overlies the epimysium, are continuous with the tough connective tissue of a tendon at myotendinous junctions which join the muscle to bone, skin, or another muscle Muscle Tissue: Cardiac Muscle ◦Cardiac Muscle – also has cross- striations and is composed of elongated, often branched cells bound to one another at structures called intercalated discs and their contraction is involuntary, vigorous, and rhythmic. Muscle Tissue: Smooth Muscle ◦Smooth Muscle – consists of collections of fusiform cells which lack striations and have slow, involuntary contractions. Nervous Tissue ◦ Nerve tissue is distributed throughout the body as an integrated communication network. ◦ Formed by a network of many billion nerve cells (neuron), all assisted by many more supporting cells called glial cells. ◦ General organization of the nervous system has two major divisions: ◦ CNS ◦ PNS Nervous Tissue: Neurulation Nervous Tissue: Neuron ◦ Functional unit 3 main parts: ◦ Cell body – contains the nucleus and most of the cell’s organelles and serves as the synthetic/ trophic center for the entire neuron ◦ Dendrites – elongated processes extending from the perikaryon and specialized to receive stimuli from other neurons ◦ Axon – a single long process ending at synapses specialized to generate and conduct nerve impulses to other cells Nervous Tissue: Structural Classes of Neuron ◦ Classification according to the number of processes extending from the cell body ◦ Multipolar neurons – one axon and two or more dendrites ◦ Bipolar neurons – one axon and one dendrite ◦ Unipolar/ Pseudounipolar neurons – single process that bifurcates close to the perikaryon with longer branch extending to a peripheral ending and the other toward the CNS ◦ Anaxonic neurons – many dendrites but no true axon Nervous Tissue: Cell Body ◦ AKA Perikaryon or Soma ◦ Contain the nucleus ◦ Acts as a trophic center, producing most cytoplasm for the process ◦ In contact with a great number of nerve endings ◦ Has an unusually large, euchromatic nucleus with a prominent nucleolus ◦ Cytoplasm contains numerous free polyribosomes and highly developed RER (Chromatophilic substance/ Nissl bodies) Nervous Tissue: Dendrite ◦ Typically short, small processes emerging and branching off the soma ◦ Covered with many synapse ◦ Synapses – sites where nerve impulses are transmitted from one neuron to another ◦ Principal signal reception and processing sites on neurons ◦ Become much thinner as they branch Nervous Tissue: Dendrite Nerve Impulse ◦ Action potential ◦ Travels along an axon like a spark move along an explosive’s fuse ◦ An electrochemical process initiated at the axon hillock when other impulses received at the cell body or dendrites meet a certain threshold Nervous Tissue: Axon ◦ Most neurons have only one axon ◦ Longer than dendrites ◦ Axolemma – plasma membrane of axon ◦ Axoplasm – content of axolemma ◦ Originate from the pyramid-shaped region of the perikaryon called the axon hillock Nervous Tissue: Glial Cells ◦ Support neuronal survival and activities ◦ 10 times more abundant than neurons ◦ Substitute for cells of connective tissue in some respects, supporting neurons and creating immediately around those cells microenvironments that are optimal for neuronal activity Nervous Tissue: Glial Cells