Chapter 4

Desmosomes

- linking integral proteins; allow for materials in extracellular fluid to pass through space between cells

Dense regular elastic connective tissue

-CT proper Mostly parallel-oriented elastic fibers with randomly oriented collagen fibers -In walls of organs that must stretch to function (large blood vessels and certain ligaments)

Serous membranes

-Fold over themselves; appearance of two layers; outer parietal layer lines body wall; inner visceral layer covers organ within body cavity -Mesothelial cells produce thin, watery serous fluid; fills space between parietal and visceral layers; reduces friction created when organs (heart or lungs) move within respective membranes

More info on Bone Components

-Osteoblasts (Figure 4.18b) §"Bone-builders" on outer surface of bones; closely associated with dense irregular collagenous connective tissue covering (periosteum) §Carry out process of bone deposition; synthesize and secrete organic ECM and chemicals involved in trapping calcium in ECM -Osteocytes - osteoblasts that have surrounded themselves with ECM in lacunae; mature cells, mostly inactive; continue to make and secrete substances important for bone maintenance -Osteoclasts - large, multinucleated bone destroyers; carry out process of bone resorption; secrete hydrogen ions and enzymes that break down both inorganic and organic ECM

Transport across simple epithelia occurs via two routes

-Paracellular transportation - substances leak between cells in epithelial membrane; limited due to tight junctions that make spaces between cells nearly impermeable -Transcellular transportation - substance enters cell by crossing plasma membrane; diffuses across cytosol; exits cell through plasma membrane at opposite side

More info on Blood Components

-Plasma proteins - not like fibers found in other connective tissues; smaller with a variety of functions, including transport of substances and blood clotting -Erythrocytes (red blood cells) bind to and transport oxygen throughout body -Leukocytes (white blood cells) function in immunity -Platelets - cell fragments; major role in blood clotting

muscle tissue

-Skeletal muscle -Cardiac muscle -Smooth muscle

Epithelial tissue - Cell shapes/classification

-Squamous cells - flattened -Cuboidal cells - short -Columnar cells - tall and elongated

Endocrine glands

-secrete products, usually hormones, directly into bloodstream without use of ducts: §Allow products to have systemic effects (on distant cells) §Example of Cell-Cell Communication Core Principle

Dense connective tissue

CT Proper -mostly protein fibers; three classes: §Dense irregular connective tissue Dense Regular Tissue Dense regular elastic connective tissue

Adipose tissue

CT proper -- fat-storing adipocytes and surrounding fibroblasts and ECM; adipocytes can increase in size to a point where fibroblasts and ECM are scarcely visible (Figure 4.16); functions: §Fat storage (major energy reserve of body) §Insulation (retains warmth) Shock absorption and protection

Fibroblasts

CT proper -Loose connective tissue most common resident cell Location: Superficial fasces Function: support and protection

Dense regular connective tissue

CT proper -Organized into parallel collagen bundles -In tendons and ligaments; subject to tension in one plane of movement

Loose connective tissue

CT proper -mostly ground substance; contains all three types of protein fibers, fibroblasts, and occasionally adipocytes, suspended in ground substance (Figure 4.13): §Beneath epithelium of skin, in membranes lining body cavities, and within walls of hollow organs §Contains and supports blood vessels vital to avascular epithelial tissues; houses immune system cells

Reticular tissue

CT proper mostly reticular fibers produced by fibroblasts (reticular cells) §Forms fine networks that support small structures such as blood and lymphatic vessels §Also in lymph nodes and spleen; forms weblike nets that trap old and foreign cells (Figure 4.15) §Forms part of basement membrane; supports all epithelia and internal structure of liver and bone marrow

Dense irregular connective tissue

CT proper §predominantly disorganized collagen bundles -Strong; resists tension in all three planes of movement -In high tension areas such as dermis (deep to skin) and surrounding organs and joints

Mast cells

Ct proper -largest resident cell §Immune system cells filled with cytosolic inclusions (granules) of inflammatory mediators (histamine) §Release mediators (degranulate) when stimulated, causing inflammation (protective response that activates immune system)

Adipocytes (fat cells)

Ct proper in many different connective tissues; cytoplasm filled with a single large lipid inclusion Function: Protection and insulation and support

epithelial tissue

Functions: •Protection - shield underlying tissues from mechanical and thermal injury •Immune defenses - form physical barriers; prevent invasion by microorganisms; specialized cells of immune system are scattered throughout epithelial tissues to protect underlying tissues •Secretion - form glands that produce substances like hormones and oils; secreted into blood or through ducts respectively •Transport into other tissues - selectively permeable membranes; substances are able to cross these barriers by passive or active transport and enter other tissues •Sensation - most associated with rich nerve supply; detect changes in internal and external environments; taste buds are examples of specialized sensory epithelial cells

Cartilage

Specialized CT -in joints between bones, ear, nose, and segments of respiratory tract •tough, flexible tissue; absorbs shock and resists tension, compression, and shearing forces; ECM consists of collagen and elastic fibers, proteoglycans, and glycosaminoglycans -Populated with two cell types: §Chondroblasts - immature cells; divide by mitosis and make most of ECM §Eventually surround themselves in small cavities (lacunae) in ECM to become mature, largely inactive chondrocytes Avascular

Blood

Specialized CT unique connective tissue with liquid ECM (plasma); consists of mostly water, dissolved solutes, and proteins

Bone tissue (osseous tissue)

Specialized CT •supports body; protects vital organs; provides attachments for muscles that allow for movement; stores calcium; and houses bone marrow (produces blood cells and stores fat)

Cell junctions

another way cells bind to one another; neighboring cell's plasma membranes are linked by integral proteins; three major types of cell junctions: •Tight junctions •Desmosomes Gap junctions

Pseudostratified columnar epithelium

appears layered because nuclei are at various heights; only one cell-layer thick with basal plasma membranes firmly in contact with basement membrane; in segments of respiratory tract and nasal cavity; ciliated

A.Epithelial tissues, or epithelia

are tightly packed sheets of cells with no visible ECM that cover and line all body surfaces and cavities. Specialized _________ form glands that manufacture secretions such as sweat, saliva, or chemical messengers called hormones.

C.Muscle tissues

capable of generating force by contracting, have little ECM between cells.

B.Connective tissues

connect all the other tissues in the body to one another. The ECM is a prominent feature for most connective tissue types with cells scattered throughout. They bind, support, protect, and allow for transportation of substances.

D.Nervous tissues

consist of cells capable of generating, sending, receiving messages, and cells that support this activity all within a unique ECM.

Specialized connective tissues

more specific functions; include three types of tissue Cartilage Bone Tissue Blood

Stratified epithelia

more than one cell layer

Gap junctions

small pores formed by protein channels between adjacent cells; allow small substances to flow freely between each cell's cytoplasm

Histology

study of normal structures of tissues (group of structurally and functionally related cells and their external environment; together perform common functions); all tissues share two basic components:

Extracellular matrix (ECM)

substances in liquid, thick gel, or solid form that surround cells of tissue; two main components: ground substance and protein fibers (Figure 4.1): •ECM performs a variety of functions: -Provides tissue with strength to resist tensile (stretching) and compressive forces -Directs cells to proper positions within tissue and holds those cells in place -Regulates development, mitotic activity, and survival of cells in a tissue

Membranes

thin sheets of one or more tissues; line body surface or cavity: •Most consist of superficial epithelial layer resting on connective tissue layer; sometimes contain smooth muscle •Functions: anchor organs in place, serve as barriers, function in immunity, and secrete various substances •True membranes •Membrane-like structures - mucous and cutaneous membranes; don't fit above structural and functional definitions; perform many of same functions

Fibrocartilage

§filled with bundles of collagen fibers; little room for ground substance in ECM (Figure 4.17b) -Fibroblasts reside in tissue; also chondroblasts and chondrocytes; fill ECM with collagen and some elastic fibers -Tissue has great tensile strength with some degree of elasticity -In between bones of fibrous joints; forms articular discs that improve fit of bones in joints

Hyaline cartilage

§most abundant cartilage -ECM mostly ground substance made of small bundles of fine collagen; gives tissue glossy bluish-gray appearance -On ends of bones in joints (articular cartilage), linking sternum to ribs, framing sections of respiratory tract, and in nose - Most of fetal skeleton is hyaline cartilage; replaced with bone during development

Elastic cartilage

§mostly elastic fibers in ECM (Figure 4.17c) -Allows tissue to vibrate -In limited number of structures; external ear assists with detection of sound in air; larynx assists with production of sound

Connective tissue proper

• Widely distributed in body •Connect tissues and organs to one another •Components of internal architecture of some organs four types= Loose CT, Dense CT, Reticular, Adipose tissue

Gland

•- structure of epithelial origin; synthesizes and secretes product from designated secretory cells -Arises from epithelial tissue that migrated into deeper connective tissue instead of remaining at surface -Classified either by shape or by how products are released -Products released by two mechanisms: §Endocrine Exocrine

Connective tissues Functions

•Connecting and binding - anchor tissue layers in organs and link organs together •Support - bone and cartilage support weight of body •Protection - bone tissue protects internal organs; cartilage and fat provide shock absorption; components of immune system are throughout connective tissues •Transport - blood is fluid connective tissue; main transport medium in body

Components of Epithelial Tissue

•Epithelial tissues consist of tightly packed cells linked together by tight junctions and desmosomes •Make sheets of cells fairly impermeable and resistant to physical stresses and mechanical injury Epithelial tissues are avascular

Nervous tissue repair

•Nervous tissue generally undergoes fibrosis - neurons have lost ability to divide by mitosis; incapable of regeneration: -Neuroglial cells retain ability to divide by mitosis and replace dead and damaged neurons with scar tissue -Axons of neurons outside brain and spinal cord can regenerate given the right conditions

True membranes

•Synovial membranes - line cavities surrounding freely moveable joints (knee or shoulder); two connective tissue layers without layer of epithelial cells (Figure 4.24b): -Outer layer - usually composed of mixture of loose and dense irregular connective tissue -Inner layer - synoviocytes (modified fibroblasts) secrete synovial fluid; watery, slippery fluid; primarily functions to lubricate joint

Smooth muscle tissue

•consists of smooth muscle cells; contractions are involuntary like cardiac muscle (Figure 4.21c): -Location: In walls of nearly every hollow organ, blood vessels, eyes, skin, and ducts of certain glands -Flattened cells with one centrally located ovoid nucleus -In most smooth muscle tissue, plasma membranes of neighboring cells are linked together by gap junctions

Neuroglia Cells

•diverse group of smaller cells; support activity of neurons: -Functions: §Anchoring neurons and blood vessels in place §Monitoring composition of extracellular fluid §Speeding up rate of nerve impulse transmission §Circulating fluid surrounding brain and spinal cord -Able to divide by mitosis (unlike neurons)

Protein fibers

•embedded within ground substance; long molecules composed of multiple fibrous subunits with ropelike structure; enormous tensile strength; three protein fiber types: -Collagen fibers - make up 20-25% of all proteins in body; composed of multiple repeating subunits; form white fibrous protein; resistant to tension (pulling and stretching forces) and pressure -Elastic fibers - composed of protein elastin surrounded by glycoproteins; extensibility allows fibers to stretch up to one and a half times resting length without breaking; once stretched, fibers return to resting length (elasticity) -Reticular fibers - thin, short collagen fibers; form meshwork or scaffold that supports cells and ground substance of many tissues; form weblike structure in organs such as spleen that helps trap foreign cells

Neurons

•excitable (like muscle cells); once mature, no longer divide by mitosis; three main components (Figure 4.22): -Cell body (soma) - biosynthetic center of neuron; location of nucleus and most organelles -Solitary axon extends from one end of soma; responsible for moving nerve impulse from soma to target cell (another neuron, muscle cell, or gland); Cell-Cell Communication Core Principle -Dendrites - other extensions protruding from soma; typically short with multiple branches; receive impulses from axons of neighboring neurons; deliver impulses to soma

Tight junctions

•hold cells closely together; space between is impermeable to movement of macromolecules

Mucous Membranes

•line all passages opening to outside of body; respiratory passages, mouth, nasal cavity, digestive tract, and male and female reproductive tracts (Figure 4.25a): -Layer of epithelium and basement membrane (connective tissue called lamina propria) and occasionally thin layer of smooth muscle -Contain glands with goblet cells; produce and secrete mucus; serve several functions, primarily protection

Nervous tissue

•makes up majority of brain, spinal cord, and nerves; two main cell types and their surrounding ECM -Neurons - capable of sending and receiving messages -Neuroglia cells

Ground substance

•most of ECM; extracellular fluid (ECF or interstitial fluid) with water, nutrients, ions, and three families of macromolecules: -Glycosaminoglycans (GAGs) - chondroitin sulfate (small) and hyaluronic acid (enormous) -Proteoglycans - GAGs bound to protein core (resembles bottle brush) -Cell-adhesion molecules (CAMs) - different types of glycoproteins

Skeletal muscle tissue

•mostly attached to skeleton; contraction produces body movement (Figure 4.21a): -Skeletal muscle must be stimulated by nervous system to contract; under voluntary (conscious) control -Most skeletal muscle cells (muscle fibers) are long, extending to almost entire length of whole muscle -Forms by fusion of embryonic myoblasts, resulting in cells with more than one nucleus (multinucleate); useful for nearly constant synthesis of enzymes, structural proteins, and contractile proteins

Cardiac muscle tissue

•only in heart; composed of cardiac muscle cells; striated like skeletal muscle cells (Figure 4.21b): -Involuntary - brain does not have conscious control over contraction -Cells are short, branched; usually only one nucleus (uninucleate) -Intercalated disc - dark line separating individual cardiac muscle cells; not in skeletal muscle; contains gap junctions and modified tight junctions; allows heart muscle to contract as unit

Cells of connective tissue proper

•resident cells permanently inhabit tissue; migrant cells migrate to areas of body depending on situation -Fibroblasts -Adipocytes -Mast cells -Phagocytes Other immune system cells

Muscle tissues

•specialized for contraction; three types share ability to turn chemical energy of ATP into mechanical energy of movement •Walking, breathing, heart beating, and propulsion of substances through hollow organs all result from contractions of different muscle tissues •Main component of muscle tissue is muscle cell (myocyte); excitable (respond to electrical or chemical stimulation)