Chapter 4: The Tisse Level of Organization

Nervous Tissue

Internal Comminication

• 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

Main Function: protection, absorption, filtration, excretion, secretion, and sensory reception

A sheet of cells that cover body surfaces or cavities

• Lining of digestivetract and other hollow organs

• Glands

• Skin Surface

Connective Tissue

Supports, protects, binds, other tissues together

• Bones

• Tendons

• Fat and other soft padding tissue

Tissues

Group of cells similar in structure that perform common or related function

Histology

Study of Tissues

Covering and lining epithelia

on external and internal surfaces

Glandular Epithelia

Secretory tissues in glands

Polarity

Cells have polarity (top and bottom)

Apical Surface

Upper free side, is exposed to surface or cavity. Most ____ surfaces are smooth, but some have specialized fingerlike projections called microvilli

Basal Surface

Lower attached side, faces inwards toward body.attaches to ____ lamina, an adhesive sheet that holds _____ surface of epithelial cells to underlying cells

Specialized Contacts

• Epithelial Tissues need to fit closely together

• Many form continuous sheets

• Specialized contact points bind adjacent epithelial cells together

• lateral contacts include: Tight junctions and Desmosomes

Supported by Connectve Tissues

• All epithelia sheets are supported by ______ ____

• Reticular Laminal

• Basement Membrane

Reticular Lamina

• Deep to basal lamina

• Consists of network of collagen fibers

Basement Memebrane

• Made up of basal and reticular lamina

• Reinforces epithelial sheet

• Resist stretching and tearing

• Defines epithelial boundary

Avascular by innervated

• No blood tissues are found in epthelial tissue

• Epithelia are supplied by nerve fibers

Regeneration

• Epithelia cells have high regenerative capactities

• Stimulated by loss of apical-basal polarity and broken lateral contacts

• Some cells are exposed to friction, some to hostile substances resulting in damage

Simple Epithelia

A single layer thick involved in absorption, secretion, or filtration processes

Simple Squamous Epithelium

Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia

Function: Allows material to pass by difussion and filtration in sites where protection is not important; secretes lubricating substances in serosae (linings of ventral body cavity)

Located in the kindey, air sacs of lungs, lining of hear, blood vessels, and lymphastic vessels

Simple Cuboidal Epithelium

Single layer of cubelike cells with large, spherical central nuclei

Function: Secretion and Absorption

Simple Columnar

Single layer of tall cells with round to oval nuclei; many cells bear microvilli, some bear cillia; layer may contain mucus-secreting uniceullular glands

Function: Absorption; secretion of mucus, eznymes, and other substances; cilliated type propels mucus (or reproductive cells) by cillary action

Pseudstratified Columnar

Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia

Function: Secrete substances, particularly mucus; propulsion of mucus by cillary action

Stratified Squamous

Thick epithelium composed of several cell layers; basal cells and surface cells; 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

Function: Protects underlying tissues in areas subjected to abrasion

Transional Epithelium

Resembles both stratifed squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch

Function: Stretches readily, permits stored urine to distend urinary organ

Gland

One or more cells that makes and secretes an aqueous fluid called a scecretion

Classifed by Endocrine and Exocrine

Endocrine

Internally secreting (example: hormones)

• Ductless glands

Exocrine

externally secreting (example: sweat)

Unicellular Exocrine Glands

• The only important unicellular glands are mucous cells and goblet cells

• Found in epithelial linings of intestinal and respiratory tracts

• All produce mucin

Mucin

A sugar-protein that can dissolve in water to form mucus, a slimy protective, lubricating coating

Multicellular Exocrine Glands

• Are composed of a duct and a sectetory unit

• Usually surrounded by supportive connective tissue that supplies blood and nerve fibers to gland

Merocrine

• Part of Mode of Secretions of multicellular exocrine gland

• Most secrete products by exocytosis as secretions are produced (sweat, pancreas)

Holocrine

• Part of Mode of Secretions of multicellular exocrine gland

• Accumulate products within, then rupture (sebaceous oil glands)

Aprocrine

• Part of Mode of Secretions of multicellular exocrine gland

• Accumulate products within, but only apex ruptures; whether this types exists in humans is controversial

Connective Tissue Proper

• Six different types; vary in density and types of fibers

• Functions as a binding tissue

• Resist mechanical stress, particularly tension

• Provides resrvoir for water and salts

• Energy (fat) storage

Cartilage

• Resists compression because of large amounts of water held in the matrix

• Functions to cushion and support body structures

Bone Tissue

• Hard tissue that resists both compression and tension

• Functions in support

Blood

• A fluid tissue

• Functions to carry O2, CO2, nutrients, wastes, and other substances (such as hormones)

Ground Substance

• Unstructuredgel-like material that fills space between cells

• Medium through which solutes diffuse between blood capillaries and cells

Connective Tissue Fibers

Three types of fibers provide support

• Collagen

• Elastic

• Reticular

Collagen Tissue Fiber

• Strongest and most abundant type

• Tough; provides high tensile strength

Elastic Tissue Fibers

Networks of long, thin, elastin fibers that allow for stretch and recoil

Reticular

• Short, fine, highly branched collagenous fibers (different chemistry and form from collagen fibers)

• Branching forms networks that offer more “give”

Blast Cells

Immature form of cell that actively secretes ground substance and ECM fibers

Fibroblasts

Found in connective tissue proper

Chrondroblasts

Found in cartilage

Osteoblasts

Found in bone marrow

Cyte Cells

Mature, less active form of “blast” cell that now becomes part of and helps maintain health of matrix

Fat Cells

Store nutrients

White Blood Cells

• Neutrophils, eosinophils, lymphocytes

• Tissue reponse to injury

Mast Cells

Initiate local inflammaorty response against foreign microorganisms they detect

Macrophages

Phagocytic cells that “eat” dead cells, microorganisms; function in immune system

Connective Tissue Proper

Consists of all connective tissues except bone, cartilage, and blood

Two Subclasses:

• CT Proper - loose connective tisses: areolar, adipose, reticular

• CT Proper - dense connective tissues: dense regular, desne irregular, elastic

Areolar Connecitve Tissue

• Part of Loose Connective Tissue

• Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells

• Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissues fluid

Adipose Tissue

• Part of Loose Connective Tissue

• Matrix as in areolar, but very sparse; colsely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet

• Function: Provides reserve food fuel, insulates against heat loss, supports and protects organs

Reticular Tissue

• Part of Loose Connective Tissue

• Loose network of _______ fibers in a gel-like ground substance; ______ cells lie on the fibers

• Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells and macrophages

Regular Tissues

• Part of Dense Connective Tissue

• Primarly parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast

• Function: attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction

Irregular Tisses

• Part of Dense connective Tissues

• Primarily irregularly arranged collagen fibers; some elastic fibers; fibroblast is the major cell type

• Function: withstands tension exerted in many directions; provides structural strength

Elastic Tissues

• Part of Dense Connective Tissue

• Dense regular connective tissue containing a high proportion of elastic fibers

• Function: allows tissue to recoil after stretching; maintains pulsatile flow of blood through artieries; aids passive recoil of lungs following inspiration

Chrondroblasts

During Growth

Chrondrocytes

Adults

Cartilage

• Matrix secreted from chrodroblasts and chrondrocytes

• Tough yet flexible material that lacks nerve fibers

• Avascular

• Three types: Hyaline, Elastic, and Fibro

Avascular

Recieves nutrients from membrane surrounding it (perichondrium)

Hyaline Cartilage

• Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature lie in lacunae

• Function: supports and reinforces; serves as resilient cushion; resist compressive stress

Elastic Cartilage

• Similar to hyaline cartilage, but more elastic fibers in matrix

• Function: maintains the shape of a structure while allowing great flexibility

Fibrocartilage

• Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate

• Function: Tensile strength allows it to absorb compressive shock

Bone Tissue

• Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized

• Function: supports and protects (by encolsing ); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones in the site for blood cell formation (hematopoiesis)

Blood Tisse

• Red and white blood cells in a fluid matrix (plasma)

• Function: Transports, respiratory gases, nutrients, wastes, and other substances

Muscle Tissue

• Highly vascularized

• Responsible for most types of movement

• Three types: Skeletal, cardiac, and smooth

Skeletal Muscle Tissue

• Long, cykindrical, multinucleate cells; obvious striations

• Function: voluntary movement; locomotion; manupulation of the environment; facial expression; voluntary control

Cardiac Muscle Tissue

• Branching, striated, generally uninucleate cells that connet at specialized junctions (intercalated discs)

• Function: As it contracts, it propels blood into the circulation; involuntary control

Smooth Muscle Tissue

• Cells are spindle shaped (tapered on both ends) with central nuclei; no striations; cells arranged closely to form sheets

• Function: Propels substances or objects (foodstuffs, urine, a baby) along internal passageways; involuntary control

Nervous Tissue

• Neurouns are banching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are nonexcitable supporting cells

• Function: Neurons transmit electrical signals from sensory receptors and to effectors (muscles and glands); supporting cells support and protect neurons

Neurons

Specialized nerve cells that generate and conduct nerve impulses

Supporting cells

Cells that support, insulate, and protect neurons

Steps in tissue Repair

1. Inflammation Sets Stage

2. Organization Restores Blood Supply

3. Regneration and Fibrosis effect permanent repair