The Tissue Level of Organization Chapter 4

Tissues A group of similar cells that function together to perform a specific function

Cell Junctions

Tight Junctions Web-like strands of transmembrane proteins Fuse cells together Seal off passageways between adjacent cells Common in epithelial tissues of the stomach, intestines, and urinary bladder Help to retard the passage of substances between cells and leaking into the blood or surrounding tissues

Adherens Junctions Resist separation of cells during contractile activities Structural components Transmembrane glycoproteins called cadherins insert into the plaque and join cells Located inside of the plasma membrane attached to both membrane proteins and microfilaments of the cytoskeleton In epithelial cells, adhesion belts encircle the cell

Desmosomes Contain plaque and cadherins that extends into the intercellular space to attach adjacent cells together Desmosome plaque attaches to intermediate filaments that contain protein keratin Prevent epidermal cells from separating under tension and cardiac muscles cells from pulling apart during contraction

Hemidesmosomes Resemble half of a desmosome Do not link adjacent cells but anchor cells to the basement membrane Contains transmembrane glycoprotein integrin Integrins attach to intermediate filaments and the protein laminin present in the basement membrane

Gap Junctions Connect neighboring cells via tiny fluid-filled tunnels called connexons Contain membrane proteins called connexins Plasma membranes of gap junctions are separated by a very narrow intercellular gap (space) Communication of cells within a tissue Ions, nutrients, waste, chemical and electrical signals travel through the connexons from one cell to another

4 Basic Tissues Epithelial Tissue covers surfaces because cells are in contact lines hollow organs, cavities and ducts forms glands when cells sink under the surface Connective Tissue material found between cells supports and binds structures together stores energy as fat provides immunity to disease Muscle Tissue cells shorten in length producing movement Nerve Tissue cells that conduct electrical signals detects changes inside and outside the body responds with nerve impulses

Epithelial Tissue General Features: Basic Functions: Closely packed cells forming continuous sheets Cells sit on basement membrane Apical (upper) free surface Avascular - nutrients diffuse in from underlying connective tissue Good nerve supply Rapid cell division Covering / lining versus glandular types Basic Functions: - protection - secretion - absorption - filtration

Types of Epithelium Covering and lining epithelium epidermis of skin lining of blood vessels and ducts lining respiratory, reproductive, urinary & GI tract Glandular epithelium secreting portion of glands thyroid, adrenal, and sweat glands

Basement Membrane Basal lamina Reticular lamina from epithelial cells collagen fibers Reticular lamina secreted by connective tissue cells reticular fibers Holds cells to connective tissue Guide for cell migration during development

Classification of Epithelium Classified by arrangement of cells into layers simple stratified pseudostratified Classified by shape of surface cells squamous cuboidal columnar transitional

Epithelial Tissue Classification

Epithelial Tissues 1. Simple Epithelium a. Squamous b. Cuboidal c. Columnar 2. Stratified Epithelium 3. Pseudostratified columnar 4. Transitional 5. Glandular

Simple Squamous Epithelium

Simple Squamous Epithelium Side view Glomerular capsules of the kidney

Simple Cuboidal Epithelium

Simple Cuboidal Epithelium

Simple Columnar Epithelium

Simple Columnar Epithelium Digestive tract

Simple Columnar Epithelium Digestive tract

Pseudostratified Columnar Epithelium

Pseudostratified Columnar Epithelium Pseudostratified ciliated columnar Trachea

Pseudostratified Columnar Epithelium

Stratified Squamous Epithelium

Stratified Squamous Epithelium Epidermis of the skin

Stratified Cuboidal Epithelium

Stratified Columnar Epithelium

Transitional Epithelium

Transitional Epithelium Urinary bladder

Glandular Epithelium Derived from epithelial cells that sank below the surface during development Exocrine glands cells that secrete---sweat, ear wax, saliva, digestive enzymes onto free surface of epithelial layer connected to the surface by tubes (ducts) unicellular glands or multicellular glands Endocrine glands secrete hormones into the bloodstream hormones help maintain homeostasis

Glandular epithelium

Methods of Glandular Secretion cells release their products by exocytosis: - saliva - digestive - enzymes - sweat upper part of cell pinches off - sweat - milk whole cells die & rupture to release their products - oil gland

Connective Tissue General Features: Cells rarely touch due to extracellular matrix Matrix(fibers & ground substance secreted by cells Consistency varies from liquid, gel to solid Does not occur on free surface Good nerve & blood supply except cartilage & tendons Basic Functions: - support to body organs - storage - protection - binds body parts together

Connective Tissue 1. Ground substance: interstitial fluid, cell adhesion proteins, proteoglycans 2. Fibers: Collagen, Elastin, Reticular 3. Cells: - blast mast cells - cyte macrophages - clast blood cells

Connective Tissue 1. Loose connective tissue a. Areolar connective tissue b. Adipose tissue c. Reticular connective tissue 2. Dense connective tissue a. Dense regular connective tissue b. Dense irregular connective tissue c. Elastic connective tissue 3. Cartilage a. Hyaline cartilage b. Fibrocartilage c. Elastic cartilage Bone Tissue 5. Blood tissue

Areolar Connective Tissue

Areolar Connective Tissue Areolar (4x) fibroblasts; macrophages; mast cells stretchable; loosely arranged fibroelastic tissue packages organs supports capillaries

Adipose Tissue

Adipose Tissue Adipose (10x) fat containing cells; act as packing around and between organs

Reticular Connective Tissue

Reticular Connective Tissue framework; spleen

Dense Regular Connective Tissue

Dense Regular Connective Tissue tendons

Dense Irregular Connective Tissue

Dense Irregular Connective Tissue dermis of the skin

Elastic Connective Tissue

Elastic Connective Tissue ligaments

Hyaline Cartilage

Hyaline Cartilage Hyaline cartilage (10x) precursor of skeleton; articular surface; trachea; tip of nose perichondrium chondrocytes chondroblasts

Fibrocartilage

Fibrocartilage Fibrocartilage (40x) dense and resistant to stretching; vertebral discs; pubic symphysis

Elastic Cartilage

Elastic Cartilage Elastic cartilage (4x) flexible; predominance of elastic fibers; external ear; epiglottis; larynx

Bone Tissue

Bone Tissue Compact Bone (10x) matrix- inorganic salts (calcium phosphate and calcium carbonate)

Blood Blood red blood cells eosinophil (red arrow) neutrophil (yellow arrow)

Blood Blood

Muscle Tissue Cells that shorten Provide us with motion, posture and heat Types of muscle skeletal muscle cardiac muscle smooth muscle

Skeletal Muscle Cells are long cylinders with many peripheral nuclei Visible light and dark banding (looks striated) Voluntary or conscious control

Skeletal Muscle Skeletal (40x)

Cardiac Muscle Cells are branched cylinders with one central nuclei Involuntary and striated Attached to and communicate with each other by intercalated discs and desmosomes

Cardiac Muscle

Smooth Muscle Spindle shaped cells with a single central nuclei Walls of hollow organs (blood vessels, GI tract, bladder) Involuntary and nonstriated

Smooth Muscle Smooth (10x)

Nervous Tissue Cell types -- nerve cells and neuroglial (supporting) cells Nerve cell structure nucleus & long cell processes conduct nerve signals dendrite --- signal travels towards the cell body axon ---- signal travels away from cell body

Tissue Repair Inflammation: protect damaged area and bring in supplies for repair Fibrosis: replacement with stromal connective tissue cells, scar formation (fibroblasts) Regeneration: replacement with original cell types (parenchymal cells) some cell types can divide (liver & endothelium) some tissues contain stem cells that can divide bone marrow, epithelium of gut & skin some cell types can not divide & are not replaced muscle and nervous tissue