Chapter 4: Tissue Level of Organization

Four basic types of tissue:

Epithelial, Connective, Muscle and Neural

Epithelial tissue:

protective covering of surfaces; consists almost entirely of cells with very little extracellular matrix epithelial cells joined by cell junctions


microscopic study of tissues

4 types of cell junctions:

tight junctions, adherens junctions or desmosomes, gap junctions

Occluding or Tight Junction:

lipid portions of the two p;lasma membranes are tightly bound together by interlocking membrane proteins

Function of Occluding junctions:

isolate the contents of the lumen (passageway) from basolateral surfaces of the cell

Gap Juncctions:

two cells are held together by interlocking channel proteins (connexons) that form narrow passageways for ions and small molecules

Macula Adherens or Demosome:

dens area of cell is connected to the cytoskeleton which gives the cell its strength.

Two types of Macula Adherens:

1) Spot Demosomes - small discs connected to filaments which stabilize cell shape. 2) Hemidesmosomes - half of a spot demosome, attaches cell to extracelular filaments in the basal lamina, anchors cell.

Major functions of Epithelial tissue:

Physicla protection, control permeability, sensation, absorption, specialized secretions

Major characteristics of Epithelial tissue:

cellularity, avascularity, attachement, regeneration

Cellularity is:

epithelia are almost entirely of cells bound closely together by interconnections know as cell junctions

Avascularity is:

lacking blood vessels. Epithelial cells obtain nutrients by diffusion or absorption.

Attachement is:

the base of an epithelium is bound to a thin basal lamina or basement membrane.

Regeneration is:

epithelia cells that are damaged or lost are continuously replaced through the divisions of stem cells in the epithelium.

4 functions of Epithelial Tissue:

1) Provide Physical Protection 2) Control permeability 3) Provide Sensation 4) Produce specialized Secretions

3 Types of Epithelium:

Covering and Lining Epithelium; Glandlular Epithleium

7 types of covering and lining epithelium:

1) simple squamous 2) simple cuboidal 3) simple columnar 4) stratified squamous 5) stratified columnar 6) transitional 7) pseudostratified columnar

Simple Squamous Shape:

Single layer, Flat, scalelike

Where are simple squamous cells found:

lines air sacs of lungs, inner lining of heart and blood vessels, serous membranes, inner ear drum

Simple Cuboidal shape:

Single layer, Cube Shaped

Where are simple cuboidal cells found:

lines surface of ovary, kidney tubules, kidney, thyroid, mammmary glands, salivary glands

Simple Columnar shape:

Single layer, Rectangular

Where are simple columnar cells found:

lines gastrointestinal tract from stomach to anus, uterus, uterine tubes

Stratified Squamous shape:

Several layers, flat scalelike

Where are stratified squamous cells found:

Epidermus of skin (keratinized), lining of mouth, tongue, throat, larynx, esophagus, canal vagina (nonkeratinized)

Stratified Columnar shape:

Several layers, cube shaped

Where are stratified columnar cells found:

male urethra, mammary gland duct

Transitional cell shape:

stratified cells with variable appearance

Transitional cells are found:

lines urinary bladder, ureters

Pseudostratified Columnar Shape:

Attached to basement membrane, but not all reach the surface. Cells are almost always cilated and associated with goblet cells

Where are pseudostratified columnar cells found:

Lining upper respiratory tract, portions of male urethra

Function of Glandular Epithelium:

Produces specialized secretions

2 Types of Glandular Epithelium:

Exocrine glands and Endocrine glands

Function of Exocrine glands:

Discharge secretions onto body surface or into ducts, may be multicellular (simple or compound) or unicellular (globlet cells)

Types of Glandular Secretions:

Serous glands, mucous glands, mixed glands, cytogenic glands

Functino of Serous glands:

Secrete thin fluids: perspiration, tears, milk, digestive juices

Function of Mucous glands:

secrete mucin (glycoprotein); tongue, roof of mouth, goblet cells

Function of mixed glands:

secrete serous fluid and mucous; salivary glands

Function of Cytogenic glands:

release whole cells: testes and ovaries

3 methods of secretion:

Merocrine Glands, Apocrine Glands; Holocrine Glands

Function of Merocrine Glands:

Product released through exocytosis; most common secretion mode (mucous, sweat glands, salivary glands)

Funciton of Apocrine Glands:

Product released through the loss of both the secretory product and cytoplasm (mammary glands)

Function of Holocrine Glands:

Product released through destruction of cell (lysis); oil (sebum), underarm perspiration

Functin of Endocrine Glands:

Discharge secretions (hormones) into surrounding interstitial fluid; lack ducts

Connective Tissue:

Most abundant, makes up part of every organ, cells separated by extracellular matrix

Major Functions of Connective Tissue:

Structural support, transportation, protection of delicate organs, energy storage, immune protection

Major Characteristics of Connective Tissue:

Never exposed to outside environment; vascularity; contain sensory receptors; Extensive extracellular matrix

2 Major components of connective tissue:

Cells, Extracellular Matrix

Connective Cells are:

specialized, produce extracellular matrix

3 types of connective tissue cells:

1) Fibroblasts 2) Chondrocytes 3) Macrophage

Fibroblasts (fib):

Secrete fibers; mast cells - release histimine and heparin

Chondrocytes (cho):

cartilage cells; adipocytes (adp); osteocytes (ost); macrophage (mac)


Fat cells


Bone cells



Extracellular Matrix is made up of:

Fibers and Ground Substance

3 types of extracellular fibers:

1) collage (col) fibers, 2) reticular (ret) fibers, 3) elastic (els) fibers

Collagen Fibers:

Strong and flexible - resist stretching

Reticular Fibers:

Thin collagen fibers, covered with glycoprotein: fill space between tissue and organ

Elastic Fibers:

Resist forces applied in many directions; allow tissue to spring back after they've been stretched

Ground Substance:

Clear viscous fluid that fills space between cells; gelatinous to rubbery consistency

3 Types of Ground Substances:

Glycosaminoglycan (GAG), Proteoglycan, Adhesive Glycoproteins

Glycosaminoglycan (GAG):

Negatively charged polysaccharides that absorb and hold water. (Ex: chondroitan sulfate - found in blood vessels and bones; hyaluronic acid - slippery quality, good lubricant for joint cavities, vitreous humor)


Polysaccharaide and protein; trap large quantities of water

Adhesive Glycoproteins:

Composed of protein and carbohydrate; bind plasma membrane to collagen and proteoglycans outside cell; bind all components of a tissue together.

2 Classifications of Connective Tissue:

Embryonic Connective Tissue; Adult Connectiive Tissue

Embryonic Connective Tissue:

Mesenchyme - made of fiber in semifluid matrix with delicate collagenous fibers; all adult connective tissue develop from mesenchyme

5 Types of Adult Connective tissue:

1) Loose 2) Dense 3) Cartilage 4) Bone 5) Blood

Function of Loose tissue:

much of the space occupied by ground substance, fill spaces between organs, cushion, support epithelia

3 Types of loose tissue:

Areolar, Adipose, Reticular

Areolar loose tissue:

(fib, mst, mac) (col, els, ret) - skin (subcutaneous layer, dermis); forms lamina propria of mucous membranes

Adipose loose tissue:

(adp) (ret) - skin (subcutaneous layer); around heart and kidneys

Reticular loose tissue:

(fib) (ret) - liver; spleen; lymph nodes; thymus

2 Types of Dense tissue:

Regular and Irregular

Regular Dense tissue:

(fib) (col) - fibers oriented in one direction; white appearance; tendons (muscle to bone); ligaments (bone to bone)

Irregular Dense tissue:

: (fib) (col, els) - fibers arranged randomly; skin (dermis), around liver, kidney, spleen; fibrous sheath around cartilages and bones

Function of Cartilage Tissue:

supporting connective tissue; support; flexibility

Composition of Cartilage:

Cartilage cells in a matrix rich in chondroitin sulfate

3 Types of Cartilage:

1) Hyaline, 2) Fibrocartilage, 3) Elastic

Hyaline Cartilage:

(chondrocyte) col-fine fibers - ends of long bone, nose


(Chondrocyte) (Colagen) intervertebral discs, pubic symphasis (junction of hip bones)

Elastic Cartilage:

(Chondrocyte) (Elastic) External ear, epiglottis of larynx

Bone (Osseous) Tissue:

Supporting connective tissue; composed of living cells in a mineralized matrix (fibers and calcium/phosphate crystals); strength & support

2 Types of Bone Tissue:

Compact; Spongy

Compact Bone is made up of:

Lamellae, Lacunae, Canaliculi, Central Canals


Concentric rings on bone matrix


spaces that house bone cells


microscopic channels that lead from bone cell to central canal

Central Canals:

Contains blood vessels

Spongy Bone is made up of:

bony plates and red bone marrow

Bony Plates:

Bone fragments with spaces between the plates

Red Bone Marrow:

Site of blood cell synthesis

Blood (Vascular) Tissue is:

fluid connective tissue; matrix between cells is liquid; transportation of gases, hormones, nutrients, waste products; protection from infections

2 Types of blood tissue:

1) Formed Elements, 2) Plasma

Formed Elements:

RBC (transport gases), WBC (defence agains foreign substances), Plateletes (blood clotting)


water, nutrients, ions, hormones, gases, plasma proteins

Function of Muscle Tissue:

contracts and shortens with force; responsible for movement, heat production; posture

Major Classifications of Muscle Tissue:

1) Skeletal, 2) Cardiac, 3) Smooth

Skeletal Muscle:

multinucleate, striated, voluntary; attached to

Cardiac Muscle:

uni- or binucleate, striated intercalated discs, involuntary; heart

Smooth Muscle:

uninucleate, nonstriated, involuntary; walls of hollow organs (stomach, intestines, urinary bladder);

Function of Nervous Tissue:

Monitors changes in internal and external environments

Neurons are:

Nerve cells; they convert stimulii into nerve impulses

Function of Neuroglia:

Support cells. They nourish, support and protect neurons

Parts of a Neuron:

Cell Body, Dendrites, Axon

Neuron Cell body function:

Contains cytoplasm, nucleus, nucleolus

Neuron Dendrite Function:

Highly branched processes, specialized for receiving stimulii

Neuron Axon Function:

Single process, specialized for conducting impulses to other cells

Function of Membranes:

(epithelia and connective tissue), thin layer of tissue that covers a structure or lines a cavity

4 Types of Membranes:

Mucous, Serous, Cutaneous, Synovial

Serous Membranes:

Internal membranes. Consist of simple squamous epithelium. Basement membrane is a thin layer of areolar connective tissue. Line cavities that do not open to the outside and secrete serous fluid.

Mucous Membranes:

Internal membranes. Consist of epithelial cells. Basement membrane is a thick layer of areolar connective tissue. Line cavities that open to the outside and secrete mucous.

Cutaneous Membranes:

External membrane. Skin - largest membrane of the body. Consists of stratified squamous epithelium, underlying areolar and dense irregular connective tissue.

Synovia Membranes:

consist of connective tissue; line freely movable joints; secrete synovial fluid


occurs when tissues are damaged along with immune response. Redness, heat, swelling and pain.

Tissue Repair:

Tissues replace dead or damaged cells.

Two types of tissue repair:

Regeneration or Replacement


New cells are the same as those destroyed. Normal function of tissue is restored. Involves parenchymal cells - from organs functioning part.


New type of tissue develops (scar tissue). Loss of some tissue function. Involves Fibroblasts through a process of fibrosis.

2 Types of Skin Repair:

Primary Union, Secondary Union

Primary Union:

Surface of clot dries; forms scab. Wound fills with blood; a blood clot forms. Fibrin binds edges together. Surface of clot dries; forms scab. Inflammatory response is occurring. Fibroblasts migrate into clot and produce collagen fibers. Capillaries grow

Secondary Union:

Similar to healing in primary union, except degree of inflammatory response is greater, more cell debris exists. risk of infection is greater. more granulation tissue forms. wound contraction occurs (leads to disfiguring scars)

Tissues and Aging:

cell division declines; collagen fibers become irregular in structure (tendons less flexible and have reduced strength); elastic fibers become fragmented and less elastic (increased skin wrinkling)