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Download Chapter 5: Tissues - Plainview Schools
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CHAPTER 5: TISSUES Tissues • Groups of cells similar in structure and function • The four types of tissues • Epithelial • Connective • Muscle • Nerve Epithelial Tissue • Cellularity – composed almost entirely of cells • Covers organs, forms the inner lining of body cavities, & lines hollow organs • Special contacts – form continuous sheets held together by tight junctions and desmosomes • Polarity – apical (free surface side) and basal (thin, nonliving basement membrane) surfaces Epithelial Tissue • Supported by connective tissue – reticular and basal laminae • Avascular but innervated – contains no blood vessels but supplied by nerve fibers • Get nutrients and excrete wastes via diffusion • Regenerative – rapidly replaces lost cells by cell division • Ex) skin Classification of Epithelia • Simple (one layer) or stratified (2 or more layers) • Name is based on the apical surface • Functions • Simple – filtration, absorption, secretion • Stratified - protection Classification of Epithelia • Squamous, cuboidal, or columnar • Have hexagon shape • Makes it more efficient Epithelia: Simple Squamous • Single layer of flattened cells with disc-shaped nuclei & sparse cytoplasm • Fit tightly together (floor tiles) • Functions • Diffusion & filtration • Provide a slick, friction-reducing lining in lymphatic and cardiovascular systems • Present in kidney glomeruli, lining of heart, blood vessels, lymphatic vessels, & serosae Epithelia: Simple Squamous • Substances pass pretty easily through it • Ex) lines the air sacs (alveoli) in lungs where oxygen and carbon dioxide are exchanged • Since it is so thin and delicate, it is easily damaged Simple Squamous • Description: single layer of flattened cells with disc- shaped central nuclei & sparse cytoplasm; the simplest of the epithelia • Function: allows passage of materials by diffusion & filtration in sites where protection is not important; secretes lubricating substances in serosae • Location: kidney glomeruli, air sacs of lungs, lining of heart, blood vessels & lymphatic vessels, lining of ventral body cavity (serosae) Simple Squamous Epithelium Simple Cuboidal Epithelium • Single layer of cube-shaped cells • Usually have large, centrally located, spherical nuclei • Present in ovaries, kidney tubules (filtration), & ducts of certain smaller glands like the salivary, thyroid, pancreas, & liver glands • Tissue secretes glandular products Simple Cuboidal Epithelium Simple Columnar Epithelium • Single layer of elongated cells with large, spherical nuclei • Goblet cells are often found in this layer • Secrete mucus for protection on the apical surface • Functions: secretes digestive fluids & absorbs nutrients from digested foods • Found in most organs of the digestive tract (stomach, large & small intestines) and the uterus Simple Columnar Epithelium • Absorption cells have microvilli on their apical surface • This increases their surface area so more of the substance can be absorbed Simple Columnar Epithelium Pseudostratified Columnar Epithelium • Single layer of cells with different heights; some do not reach the free surface • Nuclei are seen at different layers • Nonciliated cells are present in the male sperm-carrying ducts • Ciliated cells have cilia on the apical surface of the cells • Constantly moving, goblet cells are present and cilia sweeps the mucus away • Present in the passages of the respiratory system • Mucus from goblet cells trap dust & microorganisms; the cilia move the mucus & captured particles up and out of the airways Pseudostratified Columnar Epithelium Stratified Squamous Epithelium • This membrane composed of several layers of cells • Function in protection from underlying areas subjected to abrasion • Forms the external part of the skin’s epidermis (keratinized cells) and linings of the esophagus, mouth, and vagina (nonkeratinized cells) • Good at regeneration – lost cells are replaced by ones from below Stratified Squamous Epithelium • Upper layers may be dead because they do not receive enough nutrients • Keratinized cells – contain a protective protein • Cells in the top layer DON’T contain nuclei • Nonkeratinized cells – do not contain the protective protein • Top layer of cells DO contain nuclei Stratified Squamous Epithelium Stratified Cuboidal Epithelium • Two or three layers of cuboidal cells that form the lining of a lumen • Layering of cells provides more protection than a single layer • Lines the larger ducts of the mammary glands, sweat glands, salivary glands, and pancreas • Pretty rare in the body Stratified Cuboidal Epithelium Stratified Columnar Epithelium • Limited distribution in the body • Found in the pharynx, male urethra, and lining some glandular ducts • *also occurs at transition areas between two other types of epithelia Stratified Columnar Epithelium Transitional Epithelium • Specialized to change in response to increased tension • Has several cell layers, basal cells are cuboidal, surface cells are dome shaped • Stretches to permit the distension of the urinary bladder • Forms a barrier that helps prevent the contents of the urinary tract from diffusing back into body • Lines the urinary bladder, ureters, and part of the urethra (only found in organs of the urinary system) Transitional Epithelium Glandular Epithelium • A gland is one or more cells that makes and secretes an aqueous fluid • Usually found within columnar and cuboidal epithelia • Contain a lot of rough ER • Secretory vesicles fuse w/ membrane & secrete fluid • Secrete lipids, proteins, steroids • Classified by: • Site of product release – endocrine or exocrine • Relative number of cells forming the gland – unicellular (goblet) or multicellular Endocrine Glands • Ductless glands that produce hormones • Secretions include amino acids, proteins, glycoproteins & steroids • Release secretions to surrounding systems & the hormones are transported by blood or lymphatic fluid to organs • Ex) estrogen & testosterone Exocrine Glands • More numerous than endocrine glands • Secrete their products onto body surfaces (skin) or into body cavities • Ex) mucous, sweat, oil & salivary glands • The only important unicellular gland is the goblet cell • Multicellular exocrine glands are composed of a duct and secretory unit Connective Tissue • Found throughout the body; most abundant and widely distributed of the primary tissues • Types of connective tissue: • Loose connective tissue • Adipose tissue • Dense connective tissue • Cartilage • Bone • Blood Functions of Connective Tissue • Binding & support of surrounding tissues • Protection • Insulation (adipose) • Transportation • Materials are able to go through the extracellular matrix Characteristics of Connective Tissue • Connective tissues have: • Mesenchyme as their common tissue of origin • Varying degrees of vascularity • Nonliving extracellular matrix consisting of ground substances and fibers fills spaces between cells • Collagen fibers • Elastic fibers • Reticular fibers Structural Elements of Connective Tissue • Ground substance – unstructured material that fills the space between cells • Fibers – collagen, elastic, or reticular • Cells – fibroblasts, chondroblasts, osteoblasts, and hematopoietic stem cells Ground Substance • Interstitial (tissue) fluid • Adhesion proteins – fibronectin and laminin • Proteoglycans – glycosaminoglycans (GAGs) • Functions as a molecular sieve through which nutrients diffuse between blood capillaries and cells Fibers • Collagen – tough; provides high tensile strength (thickest) • Elastic – long, thin fibers that allow for stretch (medium) • Reticular – branched collagenous fibers that form delicate networks (thinnest) Cells • Fibroblasts – connective tissue proper • Chondroblasts – cartilage • Osteoblasts – bone • Hematopoietic stem cells – blood • White blood cells, plasma cells, macrophages, and mast cells Loose Connective Tissue • Also know as areolar tissue • Forms delicate, thin membranes throughout the body; widely distributed • The cells of this tissue are mainly fibroblasts; they are separated by a gel-like matrix that contains many collagenous and elastic fibers • Binds the skin to the underlying organs and fills spaces between muscles • Wraps and cushions organs Loose Connective Tissue Adipose Tissue • Fat • Develops when certain cells store fat in droplets within their cytoplasm and enlarge • When these cells are so numerous that they crowd other cells types they form adipose tissue • Lies beneath the skin, spaces between muscles, around the kidneys, behind the eyeballs, in abdomen, on the surface of the heart, and around certain joints • Cushions joints and the kidneys, insulates the body, stores energy in fat molecules Adipose Tissue Dense Connective Tissue • Consists of many closely packed, thick, collagenous fibers • • • • • and a fine network of elastic fibers It has relatively few cells most are fibroblasts Collagenous fibers of dense connective tissue are very strong enables the tissue to withstand pulling forces Often binds body parts together as parts of tendons and ligaments Protective white layer of the eyeball & in the deeper skin layers Tissue repair is slow because of the poor blood supply to dense connective tissue Dense Connective Tissue • Attaches muscles to bone or to other muscles and bone to bone • Found in: • Tendons – attaches muscle to bone • Ligaments – attaches bone to bone • Aponeuroses – attaches muscle to muscle Dense Connective Tissue Cartilage • Rigid connective tissue • Provides support, frameworks, and attachments, protects underlying tissues and forms structural models for many developing bones • Cartilage matrix is abundant and largely composed of collagenous fibers embedded in a gel-like ground substance • Chondrocytes cartilage cells • Occupy small chambers called lacunae and are completely within the matrix Cartilage • Cartilaginous structure is enclosed in a covering of connective tissue call perichondrium • Perichondrium contains blood vessels that provide cartilage cells with nutrients by diffusion • Cartilage does not heal quickly and chondrocytes do not divide frequently because of a lack of a direct blood supply Cartilage • Three types of cartilage: • Hyaline cartilage • Elastic cartilage • Fibrocartilage matrix similar to hyaline cartilage but less firm with thick collagen fibers • Provides tensile strength and absorbs compression shock • Found in the intervertebral discs, the pubic symphysis, and in discs of the knee joint Hyaline Cartilage • Amorphous, firm matrix w/ imperceptible network of collagen fibers • Supports, reinforces, cushions, and resists compression • Found in embryonic skeleton, the end of long bones, nose, trachea, and larynx Elastic Cartilage • Similar to hyaline cartilage but with more elastic fibers • Maintains shape and structure while allowing flexibility • Supports external ear (pinna) and the epiglottis Fibrocartilage • Matrix similar to hyaline cartilage but less firm with thick collagen fibers • Provides tensile strength and absorbs compression shock • Found in the intervertebral discs, the pubic symphysis, and in discs of the knee joint Bone • Hard, calcified matrix with collagen fibers found in bond • Osteocytes are found in lacunae and are well vascularized • Supports, protects, and provides levers for muscular action • Stores calcium, minerals, and fat • Marrow inside bones is the site of hematopoiesis making of red blood cells Bone Blood • Red and white cells in a fluid matrix (plasma) • Contained within blood vessels • Functions in the transport or respiratory gases, nutrients, and wastes Nervous Tissue • Branched neurons with long cellular processes and support cells • Transmits electrical signals from sensory receptors to effectors • Receptors Brain Effectors • Found in the brain, spinal cord, and peripheral nerves Nervous Tissue Muscle Tissue • Contractile – the elongated cells (muscle fibers) can shorten • As muscle tissues contract, the fibers pull at their attached ends • This moves body parts • Three types: • Skeletal • Smooth • Cardiac Skeletal Muscle Tissue • Long, cylindrical, multinucleated cells with obvious striations • Multinucleated because many cells are fused together to make 1 long cell • Initiates and controls voluntary movement • Found in skeletal muscles that attach to bones or skin Skeletal Muscle Tissue Smooth Muscle Tissue • Sheets of spindle-shaped cells with central nuclei that have no striations why its called smooth • Shorter than skeletal muscle • Usually can’t be stimulated to contract by conscious efforts • Propels substances along internal passageways • Ex) food down the digestive tract, constricts blood vessels, empties the urinary bladder • Found in the walls of hollow organs • Stomach, intestines, urinary bladder, uterus, blood vessels Smooth Muscle Tissue Cardiac Muscle Tissue • Only found in the walls of the heart • Cells are striated with a single nucleus • Where cells connect to one another it is a specialized intercellular junction intercalated disk • Cardiac muscle is controlled involuntarily • Pumps blood through the heart chambers and into blood vessels Cardiac Muscle Tissue
