Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Embryonic stem cell wikipedia , lookup
Cell culture wikipedia , lookup
Stem-cell therapy wikipedia , lookup
Chimera (genetics) wikipedia , lookup
Hematopoietic stem cell wikipedia , lookup
Adoptive cell transfer wikipedia , lookup
Neuronal lineage marker wikipedia , lookup
Cell theory wikipedia , lookup
Nerve guidance conduit wikipedia , lookup
Developmental biology wikipedia , lookup
Ch 4: Tissues Intro to tissues • Tissues – – Groups of cells that are similar in structure and function • 4 primary tissue types – Epithelial (covering & linings) – Connective (support) – Nervous (control) – Muscular (movement) Epithelial tissue • Epithelium – – Epithe = “laid on, covering” – A sheet of cells that covers a body surface or lines a cavity – Forms boundaries between environments – Functions – • Protection • Absorption (process by which the products of digestion pass through the alimentary tube mucosa into the blood or lymph) • Filtration (passage of a solvent and dissolved substances through a membrane or filter) • Excretion (elimination of waste products from the body) • Secretion (passage of material formed by a cell to its exterior) • Sensory reception – Occurs in the body as... • A covering or lining epithelium • Or as glandular epithelium Special characteristics of epithelium • Cellularity – – Composed of closely packed cells with little extracellular material between • Specialized contacts – – Bound together by specialized contacts (desmosomes & tight junctions) – Forms continuous sheets • Polarity – – Possess an apical & basal surface • Apical – free and exposed – most have microvilli – Cilia – propel substances along their free surface (trachea) • Basal – attached surface – Basal lamina – thin supporting sheets made mostly of glycoproteins – acts as a selective filter for the diffusion of nutrients Specialized characteristics cont. • Support – – All epithelial tissue rest & are supported by connective tissue – Reticular lamina – • Below basal lamina • Contains collagen fibers of the connective tissue – Reticular lamina + basal lamina = basement membrane • Reinforces epithelium (helps resist tearing & stretching) • Avascular but innervated – – Avascular = no blood vessels • Nourished by diffusing nutrients from underlying connective tissue – Innervated = supplied by nerves • Regeneration – – High regeneration capacity Cell shapes Classification of epithelium • Naming – – First name – • Indicates the number of layers present • Simple – one layer – Absorption and filtration • Stratified – more than one – Highly abrasive – Shape differs among cell layers – Named due to the apical layer – Second name • Describes the shape of the cell • Squamous – – Flat and scale like • Cuboidal – – Box/cube like • Columnar – – Tall and column shaped Epithelium • Simple epithelia are mostly concerned with absorption, secretion, and filtration – Simple squamous – • • • • • Single layer of flattened cells Sparse cytoplasm Bulging nucleus Filtration & exchange Special examples; – Endothelium – » “inner covering” » Slick & friction reducing » Lymphatic vessels, blood vessels, heart, & capillaries – Mesothelium – » “middle covering” » Serous membrane lining ventral body cavities » Covers organs Simple squamous Epithelium cont. • Simple cuboidal – – Single layer of cube-shaped cells – Forming the smallest ducts of glands – Kidney tubules – Secretion & absorption – Spherical nuclei • Simple columnar – – Single layer of column-shaped cells – Line the digestive tract (stomach to rectum) • Dense microvili to increase absorption – Goblet cells – • secrete protective mucus Simple cuboidal Simple columnar Epithelium cont. • Pseudostratified columnar – – Contains cells of varying heights – Gives the false (psuedo) impression that there are many layers • Nuclei are at various heights – gives the false impression – – – – All cells rest on basement membrane Tallest cells reach the free apical surface May contain cilia & goblet cells Line the respiratory tract Pseudostratified Stratified epithelium • Stratified epithelia’s main function is protection. • Consists of two or more cell layers • Regeneration occurs at the basal surface • More durable than simple epithelium • Stratified cuboidal – – Rare – Ducts of large glands Stratified epithelium cont. • Stratified squamous – – Most common – Several cell layers – Cells on free surface are squamous shaped (named for free exposed surface) – Underlying cells are cuboidal or columnar – Protection – Basal cells replace apical cells – Apical cells are squamous shaped because they are not receiving adequate nutrients • Rely on diffusion of nutrients – External part of the skin & extends into every body opening Stratified squamous Stratified epithelium cont. • Stratified columnar – – Limited distribution – Small amounts in pharynx, male urethra, & some glandular ducts • Transitional – – – – – Forms the hollow organs of the urinary system Allows for stretch Basal cells = cuboidal or columnar Apical cells vary in appearance depending on the level of stretch – Not stretched – multilayered membrane – Stretched (distension) – membrane becomes squamous like Transitional Glandular epithelia • Gland – – Cells that make or secrete (export) a product • Secretion = Active Process – Secretion – aqueous fluid containing proteins – 2 types – • Endocrine – Internally secreting – Ductless (they loose their ducts) – Secrete hormones by exocytosis » Directly into lymph or blood systems » Or directly into the extracellular space • Exocrine – – – – – Externally secreting Have ducts More numerous in the body Secrete onto a surface or into body cavities Sweat, oil, salivary glands Connective tissue • Found everywhere in the body • Consist of living cells surrounded by a matrix • Differences = cell type & fiber type & the amount of the two • Main classes – – – – – Connective tissue proper – fat and fibrous tissue Cartilage Bone Blood • Major functions – – – – – Binding & support Protection Insulation Transportation Connective tissue cont. • Common characteristics – – Common origin – • All connective tissues arises from embryonic tissue called mesenchyme – Degrees of vascularity – • Connective tissue ranges from avascular to highly vascularized • Cartilage – avascular • Dense connective tissue – poor vascularization • All other connective tissue – rich blood supply – Extracellular matrix – • Connective tissue is composed mainly of nonliving extracellular matrix • Separates the cells of the tissue • Allows connective tissue to – – Bear weight – Withstand tension – Endure physical trauma Connective tissue cont. • Ground substance – – Unrestricted material that fills the space between the cells and contains fibers – Mechanism through which nutrients and other dissolved substances can diffuse – Composed of: • Interstitial fluid • Cell adhesion proteins • Proteoglycans – helps determine the stiffness of the ground substance • Fibers – makes the fluid less pliable Connective tissue cont. • Fibers – – Provide support – Collagen fibers – • Strong • Provide large amounts of tensile strength (ability to resist longitudinal strain) • Composed of fiberous protein: collagen • Has a glistening appearance; also called white fibers – Elastic fibers – • Elastin proteins • Allows fibers to stretch & recoil • Skin, lungs, & blood vessels – Reticular fibers – • • • • Reticul – “network” Fine collagenous fibers that form networks Extensive branching network Surrounds blood vessels, supports soft tissue organs, & around basement membranes Connective tissue cont. • Fundamental cell types – – All connective tissues have an immature and mature cell form – “blast” – actively forming cells – secrete ground substance & fibers characteristic of the matrix • 4 primary blast cells – – – – Osteoblast – bone cells Fibroblast – connective tissue proper Chondroblast – cartilage Hematopoietic stem cell – blood – “cyte” – inactive mature cells • Osteocyte – mature bone cells • Chondrocyte – mature cartilage cells Types of connective tissue • Connective tissue proper – – Loose connective • Areolar, adipose, & reticular – Dense connective • Dense regular, dense irregular Loose connective tissue • Areolar – – “areola” – a small open space – Binds body parts together while allowing them to move freely over one another – Wraps small blood vessels & nerves – Surrounds glands – Forms subcutaneous tissue – Most widely distributed connective tissue – Contains fibroblasts –actively mitotic fiber cells – Loose arrangement of tissue – provides a reservoir of water and salt Areolar Loose connective tissue • Adipose – – – – – – Fat tissue Contain a pure fat droplet, displaces nucleus Highly vascularized – high metabolic activity Closely packed cells – little matrix Adipocytes – • Fat cells • Mature cells are some of the largest cells in the body • Mature cells can’t divide – Develops where areolar tissue is plentiful – Insulation, stores nutrients, & shock absorber – Brown fat – • Consumes its stored nutrients to generate heat to warm the body • Occurs in babies who lack the ability to produce their own heat through shivering Adipose Loose connective tissue • Reticular connective tissue – – Resembles areolar tissue – Contains only reticular fibers – Forms stroma • Internal framework • Supports blood cells • Lymph system, spleen, & bone marrow – Limited within the body even though reticular fibers are numerous Reticular Dense connective tissue • Dense regular – – Contains closely packed bundles of collagen fibers running in the same direction – Run parallel to the direction of pull – Makes up tendons (attach muscle to bone) and ligaments (attach bone to other joints) – Great resistance to tension – exerted in a single direction – Poorly vascularized – slow regeneration Dense regular Dense connective tissue • Dense irregular tissue – – Contains thick bundles of collagen fibers – Arranged in an irregular (more than one plane) fashion – Found in: • Dermis • Joint capsules Dense irregular Cartilage • • • • • Lacks nerve fibers (not innervated) Avascular Withstands tension & compression Tough but flexible Ground substance – – Collagen fibers – Elastic fibers – Water (80%) • Allows cartilage to rebound after being compressed • Nourishes the cartilage cells • Chondroblasts – produces new matrix • Chondrocytes – found in small groups w/in cavities (lacunae) Cartilage cont. • Hyaline – – Hyalin = glass – Collagen fibers are not apparent within the matrix – gives it a glass like appearance – Gristle – Most abundant cartilage – Providing firm support with some pliability – Covers the ends of long bones – Absorbs compression – Supports the tip of the nose & connects ribs to sternum – Epiphyseal plates – actively growing regions near the end of long bones – continued growth in length Hyaline Cartilage cont. • Elastic – – Found where strength & exceptional stretch are needed – Contains large amounts of elastin fibers – • Allows for repeated bending – External ear – Epiglottis – covering the respiratory system Elastic Cartilage cont. • Fibrocartilage – – Found where strong support & ability to withstand pressure are required – Rows of chondrocytes alternating with rows of thick collagen fibers – Compresses and resists tension – Intervertebral disks – Spongy cartilage of the knee joint Fibrocartilage Bone • Bone – – Osseous – Supports & protects the body – Additional collagen fibers & calcium salts found in extracellular matrix – Provides cavities for fat storage & blood cells – Osteoblasts – produce organic portions of the matrix – bone salts deposited on & between the fibers – Osteocytes – reside in the lacunae – Highly vascularized Bone (osseous tissue) Blood • Blood – – Classified as a connective tissue because... • Developed from mesenchyme • Consists of blood cells & plasma proteins surrounded by plasma • Fibers – soluble protein molecules that become visible during clotting • Transport vehicle for the body Blood Nervous tissue • Nervous tissue – – Main component of the nervous system – Regulates & controls body functions – Brain, spinal cord, & nerves – Composed of 2 cell types – • Neurons – – Specialized cells that generate and conduct electrical impulses – Branching cells – Cytoplasmic extensions – allows them to transmit electrical impulses • Supporting cells – – Nonconductive cells that support, insulate, and protect the neurons Nervous tissue Muscle tissue • Muscle tissue – – – – – Highly cellular Well vascularized Responsible for movement 3 types – • Skeletal – – – – – – Attaches to the skeleton & produces voluntary body movement Packaged by connective tissue Form the flesh of the body Contain many nuclei & striations (indicates the alignment of myofilaments) Voluntary muscle • Cardiac – – – – – – – Only in the walls of the heart Responsible for the involuntary movement of the heart Contain striations Uninucleated Branching cells that fit together & the intercalated disc junctions Involuntary muscle • Smooth – – No visible striations – One nucleus – Found in the walls of hollow organs (other than the heart) – digestive, reproductive, & urinary organs – Involuntary muscle Muscles Membranes • Cutaneous membrane – – Cutaneous membrane, or skin, is an organ system consisting of keratinized squamous epithelium (epidermis) firmly attached to a thick layer of dense irregular connective tissue (dermis) – Dry membrane because its exposed to the air • Mucous membrane – – – – – – Line hollow body cavities (ie. digestive organs) Open to the exterior Adapted for absorption or secretion Bathed in mucus Contain stratified squamous or simple columnar epithelium • Serous membrane – – Found in closed cavities – Serous fluid that lubricates the facing surface – Named for their location & organ association (ie. pleura, pericardium) – Consist of simple squamous epithelium – Rests on a thin layer of areolar (loose connective) tissue Membranes Tissue repair • Tissue repair occurs in two ways: regeneration (replacement of destroyed tissue with the same kind of tissue) & fibrosis (replaces damaged tissue with fibrous connective tissue – scar tisse) • 3 steps in the repair process – – Inflammation – • Prepares the area for the repair process • Allows white blood cells & plasma to seep into the injured area • Forms a clot & holds the wound together – Organization – • Restores the blood supply • Clot is replaced by delicate pink tissue – granulation tissue • Restores blood supply – Regeneration & fibrosis – • Permanent repair • New tissue regenerates under the scab Embryonic & fetal development • Primary germ layers – – Ectoderm – • Most superficial layer (external layer) • Nervous tissue – Mesoderm – • Middle layer • Muscle and connective tissue – Endoderm – • Deepest layer (internal layer) • Epithelial tissue Primary Germ layers Aging • Increased age – – Epithelia becomes thin – Number of collagen fibers decreases – Bone, muscle, nervous tissue begin to atrophy