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Transcript
Chapter 4 Tissue: The Living Fabric 9/8/2015 © Annie Leibovitz/Contact Press Images Mdufilho 1 Nervous tissue: Internal communication • Brain • Spinal cord • Nerves Muscle tissue: Contracts to cause movement • Muscles attached to bones (skeletal) • Muscles of heart (cardiac) • Muscles of walls of hollow organs (smooth) Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters • Lining of digestive tract organs and other hollow organs • Skin surface (epidermis) Connective tissue: Supports, protects, binds other tissues together • Bones • Tendons • Fat and other soft padding tissue 9/8/2015 Mdufilho 2 4.2 Epithelial Tissue • Epithelial tissue (epithelium) is a sheet of cells that covers body surfaces or cavities • Two main forms: – Covering and lining epithelia • On external and internal surfaces (example: skin) – Glandular epithelia • Secretory tissue in glands (example: salivary glands) • Main functions: protection, absorption, filtration, excretion, secretion, and sensory reception 9/8/2015 Mdufilho 3 Special Characteristics of Epithelial Tissues • Epithelial tissue has five distinguishing characteristics: 1. 2. 3. 4. 5. 9/8/2015 Mdufilho Polarity Specialized contacts Supported by connective tissues Avascular, but innervated Regeneration 4 Classification of Epithelia • All epithelial tissues have two names – First name indicates number of cell layers • Simple epithelia are a single layer thick • Stratified epithelia are two or more layers thick and involved in protection (example: skin) – Second name indicates shape of cells • Squamous: flattened and scale-like • Cuboidal: box-like, cube • Columnar: tall, column-like – In stratified epithelia, shape can vary in each layer, so cell is named according to the shape in apical layer 9/8/2015 5 Mdufilho Figure 4.2a Classification of epithelia. Apical surface Basal surface Simple Apical surface Basal surface Stratified Classification based on number of cell layers. 9/8/2015 Mdufilho 6 Figure 4.2b Classification of epithelia. Squamous Cuboidal Columnar 9/8/2015 Mdufilho Classification based on cell shape. 7 Figure Epithelial tissues. Simple4.3a squamous epithelium Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia. Air sacs of lung tissue Nuclei of squamous epithelial cells Function: Allows materials to pass by diffusion and 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, and lymphatic vessels; lining of ventral body cavity (serosae). 9/8/2015 Mdufilho Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (140×). 8 Figure Epithelial tissues. Simple4.3c columnar epithelium Description: Single layer of tall cells with round to oval nuclei; many cells bear microvilli, some bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells). Microvilli Simple columnar epithelial cell Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action. Location: Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus. 9/8/2015 Mdufilho Mucus of goblet cell Photomicrograph: Simple columnar epithelium of the small intestine mucosa (640×). 9 Figure 4.3e Epithelial Stratified squamous epitheliumtissues. Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers. Stratified squamous epithelium Nuclei Basement membrane Connective tissue Function: Protects underlying tissues in areas subjected to abrasion. Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane. 9/8/2015 Mdufilho Photomicrograph: Stratified squamous epithelium lining the esophagus (285×). 10 4.3 Connective Tissue • Connective tissue is the most abundant and widely distributed of primary tissues • Major functions: binding and support, protecting, insulating, storing reserve fuel, and transporting substances (blood) • Four main classes – Connective tissue proper – Cartilage – Bone – Blood 9/8/2015 Mdufilho 11 Table 4.1-1 Comparison of Classes of Connective Tissues 9/8/2015 Mdufilho 12 Table 4.1-2 Comparison of Classes of Connective Tissues (continued) 9/8/2015 Mdufilho 13 Major Functions of Connective Tissue • • • • • Binding and support Protecting Insulating Storing reserve fuel Transporting substances (blood) 9/8/2015 Mdufilho 14 Common Characteristics of Connective Tissue • Three characteristics make connective tissues different from other primary tissues: – All have common embryonic origin: all arise from mesenchyme tissue as their tissue of origin – Have varying degrees of vascularity (cartilage is avascular, bone is highly vascularized) – Cells are suspended/embedded in extracellular matrix (ECM) (protein-sugar mesh) • Matrix supports cells so they can bear weight, withstand tension, endure abuse 9/8/2015 Mdufilho 15 Structural Elements of Connective Tissue (cont.) • Connective tissue fibers • Three types of fibers provide support – Collagen – Elastic fibers – Reticular 9/8/2015 Mdufilho 16 Structural Elements of Connective Tissue (cont.) • Cells – “Blast” cells • Immature form of cell that actively secretes ground substance and ECM fibers • Fibroblasts found in connective tissue proper • Chondroblasts found in cartilage • Osteoblasts found in bone • Hematopoietic stem cells in bone marrow – “Cyte” cells • Mature, less active form of “blast” cell that now becomes part of and helps maintain health of matrix 9/8/2015 Mdufilho 17 Structural Elements of Connective Tissue (cont.) • Other cell types in connective tissues – Fat cells • Store nutrients – White blood cells • Neutrophils, eosinophils, lymphocytes • Tissue response to injury – Mast cells • Initiate local inflammatory response against foreign microorganisms they detect – Macrophages 9/8/2015 Mdufilho • Phagocytic cells that “eat” dead cells, microorganisms; function in immune system 18 Extracellular Cell types Figure 4.7 Areolar connective tissue: A matrix prototype (model) connective tissue. Ground substance Macrophage Fibers • Collagen fiber • Elastic fiber • Reticular fiber Fibroblast Lymphocyte Fat cell Capillary Mast cell Neutrophil 9/8/2015 Mdufilho 19 Figure 4.8btissue Connective tissues. Connective proper: loose connective tissue, adipose Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet. Nucleus of adipose (fat) cell Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs. Fat droplet Location: Under skin in subcutaneous tissue; around kidneys and eyeballs; within abdomen; in breasts. Adipose tissue Photomicrograph: Adipose tissue from the subcutaneous layer under the skin (350×). Mammary glands 9/8/2015 Mdufilho 20 Figure 4.8g Connective tissues. Cartilage: hyaline Description: Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae. Chondrocyte in lacuna Function: Supports and reinforces; serves as resilient cushion; resists compressive stress. Matrix Location: Forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx. Photomicrograph: Hyaline cartilage from a costal cartilage of a rib (470×). Costal cartilages 9/8/2015 Mdufilho 21 Figure 4.8h Connective tissues. Cartilage: elastic Description: Similar to hyaline cartilage, but more elastic fibers in matrix. Chondrocyte in lacuna Function: Maintains the shape of a structure while allowing great flexibility. Matrix Location: Supports the external ear (pinna); epiglottis. Photomicrograph: Elastic cartilage from the human ear pinna; forms the flexible skeleton of the ear (800×). 9/8/2015 Mdufilho 22 Figure 4.8i Connective tissues. Cartilage: fibrocartilage Description: Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate. Function: Tensile strength allows it to absorb compressive shock. Chondrocytes in lacunae Location: Intervertebral discs; pubic symphysis; discs of knee joint. Collagen fiber Intervertebral discs Photomicrograph: Fibrocartilage of an intervertebral disc (125×). Special staining produced the blue color seen. 9/8/2015 Mdufilho 23 Figure 4.8j tissues. Others: bone Connective (osseous tissue) Description: Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized. Central canal Lacunae Function: Supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis). Lamella Location: Bones Photomicrograph: Cross-sectional view of bone (125×). 9/8/2015 Mdufilho 24 Figure 4.8k Connective tissues. Connective tissue: blood Description: Red and white blood cells in a fluid matrix (plasma). Function: Transport respiratory gases, nutrients, wastes, and other substances. Red blood cells (erythrocytes) White blood cells: • Lymphocyte • Neutrophil Location: Contained within blood vessels. Plasma Photomicrograph: Smear of human blood (1670×); shows two white blood cells surrounded by red blood cells. 9/8/2015 Mdufilho 25 4.4 Muscle Tissue • Highly vascularized • Responsible for most types of movement – Muscle cells possess myofilaments made up of actin and myosin proteins that bring about contraction • Three types of muscle tissues: – Skeletal muscle – Cardiac muscle – Smooth muscle 9/8/2015 Mdufilho 26 Figure 4.9a Muscle tissues. Skeletal muscle Description: Long, cylindrical, multinucleate cells; obvious striations. Part of muscle fiber (cell) Function: Voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control. Nuclei Location: In skeletal muscles attached to bones or occasionally to skin. Striations Photomicrograph: Skeletal muscle (440×). Notice the obvious banding pattern and the fact that these large cells are multinucleate. 9/8/2015 Mdufilho 27 Figure 4.9b Muscle tissues. Cardiac muscle Description: Branching, striated, generally uninucleate cells that interdigitate at specialized junctions (intercalated discs). Intercalated discs Function: As it contracts, it propels blood into the circulation; involuntary control. Striations Nucleus Location: The walls of the heart. Photomicrograph: Cardiac muscle (475×); notice the striations, branching of cells, and the intercalated discs. 9/8/2015 Mdufilho 28 Figure 4.9c Muscle tissues. Smooth muscle Description: Spindle-shaped (elongated) cells with central nuclei; no striations; cells arranged closely to form sheets. Nuclei Function: Propels substances or objects (foodstuffs, urine, a baby) along internal passageways; involuntary control. Location: Mostly in the walls of hollow organs. Smooth muscle cell Photomicrograph: Sheet of smooth muscle from the digestive tract (500×). 9/8/2015 Mdufilho 29 4.5 Nervous Tissue • Main component of nervous system (brain, spinal cord, nerves) – Regulates and controls body functions • Made up of two specialized cells: – Neurons: specialized nerve cells that generate and conduct nerve impulses – Neuroglia: supporting cells that support, insulate, and protect neurons 9/8/2015 Mdufilho 30 Figure 4.10 Nervous tissue. Nervous tissue Description: Neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are nonexcitable supporting cells. Neuron processes Cell body Nuclei of supporting cells Axon Dendrites Cell body of a neuron Function: Neurons transmit electrical signals from sensory receptors and to effectors (muscles and glands); supporting cells support and protect neurons. Neuron processes Location: Brain, spinal cord, and nerves. Photomicrograph: Neurons (350×) 9/8/2015 Mdufilho 31