Histology PDF

Histology Reference: MTT, pgs 51 - 78, BB, pgs 44 - 47 I. Introduction A. histology – study of tissues 1. tissues – similar cells with common function 2. four general classes a. epithelial – cover body sur...

Histology Reference: MTT, pgs 51 - 78, BB, pgs 44 - 47 I. Introduction A. histology – study of tissues 1. tissues – similar cells with common function 2. four general classes a. epithelial – cover body surfaces, line ducts & cavities b. connective – bind, support, protect c. muscle – produce movement, pressure d. nervous – regulation, communication 3. cell junctions (BB: 44 - 47) a. points of contact between cells b. types: (1) tight junction (occluding junction) a. apical border of epithelial cells b. function - liquid tight junction (enable epithelia boundary role) - establish cell membrane domains (basolateral & apical) c. adhesion via occludins proteins (2) anchoring junctions (a) desmosomes (i) “rivets or spot welds” (ii) anchored by intermediate filaments (iii) transmembrane adhesion protein - cadherins b. adherens junctions (i) anchored by actin filaments (ii) concentrated in tissues undergoing distortion, stretch (iii) transmembrane adhesion protein - cadherins (3) communicating junctions – gap junctions (a) allow cytoplasmic continuity (b) low resistance pathway (c) enables intracellular signaling (d) structure (i) comprised of sets (6) of connexins (ii) two sets - comprise continuous channel connexin connexon channel II. Epithelial Tissue A. functions 1. physical protection 2. control permeability 3. provide sensation 4. produce secretions B. membranous - general features 1. simple vs stratified 2. apical & basilar border 3. non-vascularized 4. mitotically active C. simple 1. squamous a. flattened, irregularly shaped cells b. adapted for filtration, diffusion and osmosis c. e.g. lung alveoli, capillary endothelium, etc 2. cuboidal a. cube-shaped cells b. function in excretion, secretion & absorption c. e.g. kidney tubules, glands, pancreas 3. columnar a. tall, column shaped b. function in secretion, excretion and absorption c. e.g. line small intestine and colon d. goblet cells = specialized unicellular glands 4. columnar, ciliated a. cilia on apical border b. e.g. line uterine tubes 5. pseudostratified, ciliated columnar a. all cells contact basement membrane b. not all cells reach apical border c. e.g. line trachea and bronchi D. stratified 1. squamous a. keratinized (skin) b. non-keratinized (anus, vagina, oral cavity, etc.) 2. stratified cuboidal (rare) a. two or more layers of cuboidal cells b. sweat and salivary glands 3. transitional a. specialized to permit distension b. bladder summary table E. glandular epithelium 1. functions to produce & secrete substances 2. classification a. ducts (1) endocrine (ductless) – secreted into blood (2) exocrine - secreted via ducts to target b. cellular organization (1) unicellular (a.) single modified columnar cells (b.) e.g. - goblet cells (2) multicellular (a) simple (b) compound C. mechanism of secretion 1. merocrine a. secrete by exocytosis b. salivary and pancreatic glands 2. apocrine a. apical cell sloughed b. mammary glands 3. holocrine a. entire cell sloughed b. sebaceous glands III. Connective Tissue A. Introduction 1. function a. binds tissue together b. provides support c. stores energy d. produces erythrocytes e. most abundant tissue class 2. general character a. consists of cells dispersed in matrix (1) no cell connective systems (2) matrix = ground substance (solid, semisolid, fluid) + protein fibers 3. no free surface 4. highly vascularized b. major cell types 1. fibroblast - produce fibers 2. macrophages - engulf bacteria and foreign particles 3. plasma cells - mature β-lymphocytes, produce antibodies 4. mast cells - produce histamine, heparin c. matrix (1) ground substance – glycosaminoglycans (GAG) (2) fibers a. collagenous b. elastic c. reticular B. loose (areolar) connective tissue 1. binds tissues, surrounds blood vessels and nerves, e.g. fascia, 2. all fiber and cell types 3. function - elasticity and support C. dense, regular connective tissue 1. parallel, densely packed collagen fibers 2. e.g. tendons and ligaments collagen D. dense, irregular connective tissue 1. interwoven, random packed collagenous fibers 2. dermis of skin, organ and gland capsules E. elastic connective tissue 1. bundles of elastin fibrils 2. irregularly arranged, easily stretched 3. walls of arteries, bronchi & trachea elastin F. reticular connective tissue 1. network of thin, delicate, collagen fibers 2. lymph nodes, liver, spleen, basement membrane G. adipose tissue 1. protects, insulates, stores energy 2. adipocytes – specialized to store triglycerides 3. hypodermis, perirenal and pericardiac H. cartilage 1. supports, forms attachments a. chondrocytes, w/i lacunae b. matrix (i) elastic semisolid – chondroitin sulfate (ii) collagen fibers c. covered by perichondrium 2. hyaline cartilage a. flexible, matrix of fine collagen fibers b. articular surface, trachea, costal cartilage 3. fibrocartilage a. supports, withstands compression b. intervertebral discs, symphysis pubis, menisci 4. elastic cartilage a. flexible & supporting matrix b. outer ear, larynx and auditory canal I. Bone (presented in detail in lecture #5) 1. most rigid tissue a. osteocytes (1) occupy lacunae (2) concentric layers surround central canal of Haversian system (a) layers termed lamellae (b) canaliculi radiate from lacunae  b. matrix (1) calcium hydroxyapatite (2) collagen fibers 2. types a. compact (1) outer hard portion of bone (2) covered by periosteum b. spongy (1) inner porous, highly vascularized tissue (2) provides space for marrow J. vascular, blood (discussed second semester) 1. highly specialized fluid, connective tissue 2. formed elements a. erythrocytes b. leukocytes c. platelets 3. plasma IV. Muscle Tissue (detailed in lecture # 8 – 10) A. introduction 1. characterized by ability to contract or shorten 2. fn in movement, peristatsis, regulation, pressure B. classification 1. skeletal a. striated, multinucleated, cylindrical fiber b. voluntary c. skeletal movement 2. cardiac a. striated, branched, single nuclei b. intercalated discs - gap junctions c. involuntary, syncytial activity 3. smooth muscle a. non-striated, fusiform shaped cells b. involuntary c. GI tract, arteries, bladder, uterus V. Nervous Tissue (detailed in lecture #14) A. Introduction 1. central a. brain b. spinal cord 2. peripheral 1. neurons a. components (1) perikaryon (cell body) (2) axon – conducts impulse from cell body (3) dendrites – receptive surface (w. cell body) 2. neuroglia a. support and bind neurons together mesenchyme - embryonic connective tissue all connective tissue during embryonic development period large irregularly shaped cells surrounded by jellylike matrix