Tissues – a group of similar cells Tissues – a group of similar cells working together to perform a working together to perform a

functionfunction

Tissue TypesTissue Types::EpithelialEpithelial

ConnectiveConnectiveMuscularMuscularNervousNervous

HistologyHistology

The study of tissues at the The study of tissues at the microscopic levelmicroscopic level

HistologyHistology

The human body is composed of The human body is composed of approximately 200 distinctly different approximately 200 distinctly different types of cells. types of cells.

These cells are organized into four These cells are organized into four basic categories of tissues that, in basic categories of tissues that, in turn, are assembled to form organs. turn, are assembled to form organs.

Tissues can be distinguished from Tissues can be distinguished from each other by variations in cell size, each other by variations in cell size, shape, organization, and function.shape, organization, and function.

How Do Cells Form Tissues?How Do Cells Form Tissues?

Remember adhesion proteins embedded in the cell membrane!

Cell Junctions- Cell Junctions- When cells are touching each When cells are touching each other they can be joined in 1 of 3 waysother they can be joined in 1 of 3 ways

Tight Junctions Tight Junctions – sealed together by attachment proteins – sealed together by attachment proteins so that nothing can pass between the cells (if something so that nothing can pass between the cells (if something passes thru, it must go thru the bilayer not between them)passes thru, it must go thru the bilayer not between them)– Typically join cells that form sheetlike layers; digestive tractTypically join cells that form sheetlike layers; digestive tract

DesmosomesDesmosomes – tight junctions with extra protein – tight junctions with extra protein reinforcement so that the cells won’t rip apart when reinforcement so that the cells won’t rip apart when stretched (in skin). The protein reinforcements bind the stretched (in skin). The protein reinforcements bind the attachment proteins to the cytoskeleton of both attaching attachment proteins to the cytoskeleton of both attaching cellscells

Gap Junctions Gap Junctions – where the cells attach, there are small – where the cells attach, there are small tubes connecting the two cells together so that ions can tubes connecting the two cells together so that ions can pass freely between the cells (cardiac muscle in heart and pass freely between the cells (cardiac muscle in heart and smooth muscle in digestive tract); cytoplasm becomes smooth muscle in digestive tract); cytoplasm becomes linked together.linked together.

Epithelial TissueEpithelial Tissue Location – Lines a space - forms inner Location – Lines a space - forms inner

lining of body cavities, covers body surface lining of body cavities, covers body surface and organs, lines hollow organs and glandsand organs, lines hollow organs and glands

Specific Examples:Specific Examples: SkinSkin Lines whole digestive and respiratory passages Lines whole digestive and respiratory passages

(mucous membranes)(mucous membranes) Lines whole urinary systemLines whole urinary system Membranes lining spinal cord and brain (Meniges)Membranes lining spinal cord and brain (Meniges) Lines the inside of the heart cavitiesLines the inside of the heart cavities Capillary wallsCapillary walls Alveoli in lungsAlveoli in lungs Lines the uterus in females, epididymis in malesLines the uterus in females, epididymis in males Makes up the serous membranes (enclosed cavities Makes up the serous membranes (enclosed cavities

like pericardium, pleura, and peritonium) like pericardium, pleura, and peritonium) Prostate gland & other glandsProstate gland & other glands

Functions:Functions:

Protection - from leakage or from Protection - from leakage or from things getting in that aren’t supposed things getting in that aren’t supposed toto

Absorption - nutrientsAbsorption - nutrients

Secretion – mucous, pepsin, HCl, milkSecretion – mucous, pepsin, HCl, milk

Filtration – oxygen and carbon dioxideFiltration – oxygen and carbon dioxide

Characteristics: (structure = Characteristics: (structure = function)function)

Fit closely together (tight junctions or Fit closely together (tight junctions or desmosomes) – sealed so that desmosomes) – sealed so that nothing can pass between the cellsnothing can pass between the cells

Two adjectives describe all epithelial Two adjectives describe all epithelial tissuetissue– Cells are square, rectangular or Cells are square, rectangular or

“squished”“squished” Cuboidal, columnar, squamousCuboidal, columnar, squamous

– Tissue is found in one or multiple layersTissue is found in one or multiple layers Simple vs. stratifiedSimple vs. stratified

Characteristics:Characteristics: Basement membrane Basement membrane – – thin (deepest thin (deepest

layer of epithelial tissue), nonliving layer of layer of epithelial tissue), nonliving layer of collagen protein (created by cells in the collagen protein (created by cells in the connective tissue) that anchors epithelium to connective tissue) that anchors epithelium to underlying connective tissue.underlying connective tissue.

Apical surface Apical surface - - free surface that is free surface that is exposed to the outside of body or organ, or the exposed to the outside of body or organ, or the inside of a cavity, gland or tube (inside of a cavity, gland or tube (lumenlumen))

Characteristics:Characteristics: AvascularAvascular - no direct connection to - no direct connection to

blood vessels; must get nutrients blood vessels; must get nutrients from diffusion from underlying from diffusion from underlying capillaries in connective tissuecapillaries in connective tissue

Side Note: CancerSide Note: Cancer Cancer cells secrete a substance that Cancer cells secrete a substance that

dissolves basement membranes, enabling dissolves basement membranes, enabling the cells to invade tissue layers.the cells to invade tissue layers.

Cancer cells also produce less adhesion Cancer cells also produce less adhesion proteins, or none, which allows them to proteins, or none, which allows them to spread into surrounding tissue. spread into surrounding tissue. (metastasis)(metastasis)

Modified/Specialized CellsModified/Specialized Cells Microvilli – Microvilli – tiny , cylindrical processes tiny , cylindrical processes

extending from the free surface of extending from the free surface of epithelial cellsepithelial cells– Increases surface area of cell membrane Increases surface area of cell membrane

which is exposed to substances being which is exposed to substances being absorbed.absorbed.

– small intestinessmall intestines

Modified/Specialized CellsModified/Specialized Cells Goblet Cells and cilia - Goblet Cells and cilia - in the trachea, in the trachea,

goblet epithelial cells secrete mucus goblet epithelial cells secrete mucus on the free surface of tissue which on the free surface of tissue which provides lubrication to trap bacteria provides lubrication to trap bacteria and dust (ciliated epithelium then and dust (ciliated epithelium then sweeps it away from lungs).sweeps it away from lungs).

Two Types of Epithelial Two Types of Epithelial TissuesTissues

Covering/lining EpitheliumCovering/lining Epithelium

covers the outside covers the outside surfaces of the body surfaces of the body and lines internal and lines internal organs.organs.

Glandular EpitheliumGlandular Epithelium

secretes hormones or secretes hormones or other products other products (mucous, milk).(mucous, milk).– Consists of one or many Consists of one or many

cellscells

Two Types: Endocrine vs. Exocrine Two Types: Endocrine vs. Exocrine GlandsGlands

EndocrineEndocrine - epithelial - epithelial tissue secretes tissue secretes products (hormones) products (hormones) into tissue fluid or into tissue fluid or bloodblood

ExocrineExocrine - epithelial - epithelial tissue that secretes tissue that secretes their substances their substances (sweat, saliva, milk, (sweat, saliva, milk, stomach acid, and stomach acid, and digestive enzymes) digestive enzymes) into tubes, or ducts, into tubes, or ducts, which carry the which carry the secretions to the secretions to the epithelial surface of epithelial surface of cavity or skincavity or skin

Two Types: Endocrine vs. Exocrine Two Types: Endocrine vs. Exocrine GlandsGlands

Endocrine Glands Exocrine Glands

Types of EpitheliumTypes of Epithelium Simple Squamous Simple Squamous – flat, 1-layer, easily – flat, 1-layer, easily

damaged damaged

walls of blood vessel lung alveoli

Locations: Capillary walls, alveoli of the lungsFunction: diffusion and filtration

Types of EpitheliumTypes of Epithelium Simple Cuboidal Simple Cuboidal – square, 1-layer– square, 1-layer

kidney's tubules cut such that they appear as rings of cells

around empty spaces

Locations: lining kidney tubules, salivary ducts, pancreatic ductsFunctions: secretion, excretion, and absorption

Types of EpitheliumTypes of Epithelium Simple Columnar Simple Columnar – tall rectangular, 1-– tall rectangular, 1-

layer, thick to protect underlying tissue; layer, thick to protect underlying tissue; used for absorptionused for absorption– CiliatedCiliated – cells that line the throat and digestive tract. – cells that line the throat and digestive tract.

Funct: trap and move "pollutants" to the mouth where Funct: trap and move "pollutants" to the mouth where they are swallowed. Cells lining the uterine tube to they are swallowed. Cells lining the uterine tube to uterus. Funct: sweeps egg alonguterus. Funct: sweeps egg along

– NonciliatedNonciliated – lines uterus and portions of digestive tract – lines uterus and portions of digestive tract (stomach and small intestines), Funct: secretes digestive (stomach and small intestines), Funct: secretes digestive fluids, absorbs nutrients, protection. )fluids, absorbs nutrients, protection. )

– MicrovilliMicrovilli – minute surface extensions found in small – minute surface extensions found in small intestine, to increase surface area for absorbing intestine, to increase surface area for absorbing substancessubstances

Types of EpitheliumTypes of Epithelium

Statified Squamous Statified Squamous – many layers, – many layers, resistant to damage.resistant to damage.

LocationLocation: where there is a lot of : where there is a lot of abrasion – mouth, outermost layer of abrasion – mouth, outermost layer of skin, esophagus, anal canal. skin, esophagus, anal canal.

FunctionFunction: protection: protection

skin

Types of EpitheliumTypes of Epithelium TransitionalTransitional – Stratified, many layers – Stratified, many layers

–range from flat to tall cells that can –range from flat to tall cells that can extend or compress in response to extend or compress in response to body movement, act as barrier.body movement, act as barrier.– LocationLocation: inner lining of bladder and ureters. : inner lining of bladder and ureters. – FunctFunct: allows to distend and contract without : allows to distend and contract without

compromising it.compromising it.

bladder

Outer Covering View-skin -organs

Cross section view-glands-tubes

Take Note! Multiple Tissues Take Note! Multiple Tissues are On One Slideare On One Slide

Left to rightLeft to right– Epithelial covering, dense fibrous CT, epithelial Epithelial covering, dense fibrous CT, epithelial

glands, dense fibrous CT, cartilageglands, dense fibrous CT, cartilage

Connective TissueConnective Tissue Location - found everywhereLocation - found everywhere

– most abundant tissue by weight most abundant tissue by weight (proteins!)(proteins!)

Major supporting tissue of the Major supporting tissue of the bodybody– Holds everything togetherHolds everything together

Types of Connective Tissue (CT) Types of Connective Tissue (CT) Ordinary CT – Ordinary CT – loose vs. dense depending on the relative loose vs. dense depending on the relative

number of cells, fibers and ground substancenumber of cells, fibers and ground substance

– Loose CTLoose CT AreolarAreolar ReticularReticular ElasticElastic

– Dense CTDense CT Regular & IrregularRegular & Irregular

Specialized CTSpecialized CT– CartilageCartilage– BoneBone– BloodBlood– AdiposeAdipose

Connective Tissue - Connective Tissue - FunctionsFunctions

Protection (can cushion)Protection (can cushion)Serve as frameworksServe as frameworksSupportSupportBind structuresBind structuresFill spacesFill spacesStore fatStore fatProduce bloodProduce blood cells cells

Remember – structure relates to function!

CT Characteristics:CT Characteristics: Cells are not directly connected to each Cells are not directly connected to each

other (can be fixed cells or wandering other (can be fixed cells or wandering cells)cells)

Surrounded by an Surrounded by an extracellular matrix extracellular matrix (ECM) (ECM) (protein fibers, other molecules and (protein fibers, other molecules and interstitial fluid) that is made and secreted interstitial fluid) that is made and secreted by the cellsby the cells

Matrix may be jelly-like, liquid, hard, Matrix may be jelly-like, liquid, hard, fibrousfibrous– The kinds and amounts of fiber and ground substance The kinds and amounts of fiber and ground substance

determine the character of the matrix, which in turn determine the character of the matrix, which in turn defines the kind of connective tissue. defines the kind of connective tissue. (structure = (structure = function)function)

CT CharacteristicsCT Characteristics

Most connective tissue has a good Most connective tissue has a good blood supplyblood supply

Tendons and ligaments have minimal Tendons and ligaments have minimal blood supply and cartilage is avascular.blood supply and cartilage is avascular.– Given this information, why does it makes Given this information, why does it makes

sense that sports injuries involving sense that sports injuries involving tendons and ligaments take a long time to tendons and ligaments take a long time to heal?heal?

– Given this information, why are knee Given this information, why are knee replacements prevalent in old age?replacements prevalent in old age?

Connective Tissue - Cell Connective Tissue - Cell TypesTypes

CT contain a variety of cells CT contain a variety of cells – FibroblastsFibroblasts – most common type in both loose and dense – most common type in both loose and dense

connective tissues, star-shaped, produce fibers (ex: a connective tissues, star-shaped, produce fibers (ex: a protein, collagen) and secrete it from the cell to create protein, collagen) and secrete it from the cell to create the ECM of CTthe ECM of CT

– Mast Cells Mast Cells – release histamine to promote inflammation – release histamine to promote inflammation and allergy/immune response.and allergy/immune response.

– MacrophagesMacrophages – originate as WBCs, play role in immunity – originate as WBCs, play role in immunity by carrying out phagocytosis – engulf foreign and dead by carrying out phagocytosis – engulf foreign and dead cells.cells.

Extracellular Matrix Fibers: Fibroblasts Extracellular Matrix Fibers: Fibroblasts produce 3 proteins that make up ECMproduce 3 proteins that make up ECM– Collagen fibers Collagen fibers – thick threads of protein collagen, major – thick threads of protein collagen, major

structural protein of body, tough and flexible, can resist structural protein of body, tough and flexible, can resist pulling force. (p. 157 collagen disorders)pulling force. (p. 157 collagen disorders) Dense CT – many collagen fibers (tendons-connect Dense CT – many collagen fibers (tendons-connect

muscle to bone & ligaments – connect bone to bone)muscle to bone & ligaments – connect bone to bone) Loose CT – sparse collagen fibers (holds internal Loose CT – sparse collagen fibers (holds internal

organs in position)organs in position)– Elastic fibers Elastic fibers - made of springlike protein elastin, strong - made of springlike protein elastin, strong

and stretchable, can resume form (vocal cords and air and stretchable, can resume form (vocal cords and air passages)passages)

– Reticular fibers Reticular fibers - made of thin collagen fibers, highly - made of thin collagen fibers, highly branched to form delicate supporting networks (spleen)branched to form delicate supporting networks (spleen)

Types of Connective Tissue:Types of Connective Tissue: BoneBone – most rigid connective tissue – most rigid connective tissue

– cells (cells (osteoblasts osteoblasts -premature cells -premature cells /osteocytes /osteocytes -mature -mature cells) cells)

– Lacuna Lacuna – blank space that cells sit in– blank space that cells sit in Lacuna is surrounded by a matrix made of collagen fibers and Lacuna is surrounded by a matrix made of collagen fibers and

hardened due to calcium between the cells.hardened due to calcium between the cells. contains canals to connect to blood vesselscontains canals to connect to blood vessels

– LocationLocation: skeleton: skeleton– FunctionFunction: framework/support, attachement point for : framework/support, attachement point for

muscles, protection, contains red marrow to form muscles, protection, contains red marrow to form RBCs.RBCs.

-Osteoblasts (osteocytes) are bone cells that sit in an open space called a lacuna. -This allows for a blood supply with nutrients to reach the cells.-Good blood supply allows bone to heal when injured as opposed to avascular tissue like cartilage.

Cross section plane – see circle patternFrontal plane – no circle

pattern

Microscope PicsMicroscope Pics

Types of Connective Tissue:Types of Connective Tissue: Cartilage: 3 types - Cartilage: 3 types - hyaline, elastic hyaline, elastic

and fibrousand fibrous– cells in lacunae (cells in lacunae (ChondrocytesChondrocytes) surrounded by ) surrounded by

semi-hard/gel like matrix (collagen or elastic semi-hard/gel like matrix (collagen or elastic fibers)fibers)

– cartilage is tough but flexible, avascular (reason cartilage is tough but flexible, avascular (reason for knee/hip replacements), and without nerves.for knee/hip replacements), and without nerves.

Locations: joints, between vertebrae Locations: joints, between vertebrae (discs), connecting ribs to sternum, (discs), connecting ribs to sternum,

ears, noseears, nose

Cartilage Microscope PicsCartilage Microscope Pics

Elastic – more flexible because of elastic fibers, Location: ear, epiglottis, larynxFunction: flexible support

Fibrous – very tough, many collagen fibers Location: pubic symphysis, intervertebral discs in spinal column, kneesFunction: supports, withstands compression, “shock absorber”

Cartilage Microscope PicsCartilage Microscope Pics

Hyaline – extremely fine collagen fibers, looks glassyLocation: ends of bones andin joints, soft part of nose, rings in trachea,fetal skeleton, connecting ribs to sternumFunction: precursor to bone, support

Types of Connective Tissue:Types of Connective Tissue:

Dense Fibrous CT (regular and irregular) Dense Fibrous CT (regular and irregular) – – few fibroblasts and many collagen fibers few fibroblasts and many collagen fibers made by the fibroblasts, closely packed vs. made by the fibroblasts, closely packed vs. randomly organized fibersrandomly organized fibers

Location/FunctionLocation/Function: : – RegularRegular - tendons and ligaments; - tendons and ligaments;Fibers run one direction and get pulled onFibers run one direction and get pulled on

in one direction; great tensile strength;in one direction; great tensile strength;

binds body parts (ex: achilles tendon)binds body parts (ex: achilles tendon)

– IrregularIrregular – dermis (inner skin); – dermis (inner skin);Sustain tension exerted from Sustain tension exerted from

different directions.different directions.

Looks like rope = very strong

Types of Connective Tissue:Types of Connective Tissue: Areolar (loose fibrous) Areolar (loose fibrous) – – few fibroblasts, few fibroblasts,

loose network of collagen and elastic fibers loose network of collagen and elastic fibers (strong and elastic), lots of liquid space (strong and elastic), lots of liquid space (variety of cells with immune functions)(variety of cells with immune functions)– LocationsLocations: beneath the skin and around : beneath the skin and around

blood vessels, muscles and nervesblood vessels, muscles and nerves– FunctionsFunctions: binds one tissue to another : binds one tissue to another

(connects skin to underlying muscle), (connects skin to underlying muscle), protection and nourishment to the organs & protection and nourishment to the organs & structures it binds, & stores "body fluid"structures it binds, & stores "body fluid"

Types of Connective Tissue:Types of Connective Tissue: ReticularReticular (loose fibrous) (loose fibrous) – fibroblasts, – fibroblasts,

thin collagen fibers (reticular fibers) woven thin collagen fibers (reticular fibers) woven into a 3D mesh, and liquidinto a 3D mesh, and liquid

LocationsLocations: spleen, lymph nodes, liver: spleen, lymph nodes, liver FunctionFunction: gives support to soft organs: gives support to soft organs

Types of Connective Tissue:Types of Connective Tissue: Elastic CT Elastic CT – consists of elastic and – consists of elastic and

collagen fibers and fibroblast cellscollagen fibers and fibroblast cells LocationLocation: large arteries, bronchial : large arteries, bronchial

tubestubes FunctionFunction: Elastic fibers can stretch 1 : Elastic fibers can stretch 1

and 1/2 times their length and then and 1/2 times their length and then recoil, provide elasticity to tissues.recoil, provide elasticity to tissues.

aorta

Types of Connective Tissue:Types of Connective Tissue:

AdiposeAdipose – – fat storing tissue – cells with a fat storing tissue – cells with a big oil vacuole (looks like bubble wrap)big oil vacuole (looks like bubble wrap)

Cells – adipocytes; store fat in droplets in Cells – adipocytes; store fat in droplets in their cytoplasm; accumulate fat, enlarge, their cytoplasm; accumulate fat, enlarge, pushing nuclei to one side of cell; called pushing nuclei to one side of cell; called signet cells because resemble that type of signet cells because resemble that type of class ringclass ring

AdiposeAdipose

LocationLocation – beneath skin, between muscles, – beneath skin, between muscles, around kidneys, behind eyeballs, around kidneys, behind eyeballs, abdominal membranes, surface of heart, abdominal membranes, surface of heart, around jointsaround joints

FunctionFunction – insulates, cushions, lines whole – insulates, cushions, lines whole body underneath skin, energy storage body underneath skin, energy storage (*Function in adipose tissue is less about (*Function in adipose tissue is less about the matrix and more about the cells)the matrix and more about the cells)

-Born with certain number of fat cells-Amount of adipose tissue over time reflects diet (store excess calories as fat) or endocrine disorder.

Types of Connective Tissue:Types of Connective Tissue: BloodBlood – cells (red, white and platelets) in – cells (red, white and platelets) in

a liquid matrix (plasma), protein “fibers” a liquid matrix (plasma), protein “fibers” are soluble that form during clotting.are soluble that form during clotting.

FunctionFunction:: Carries oxygen, carbon dioxide, nutrients, Carries oxygen, carbon dioxide, nutrients,

and wastesand wastes Carries immune cells and antibodies to Carries immune cells and antibodies to

infected or damaged areainfected or damaged area Carries minerals Carries minerals Has lots of proteins for osmotic balanceHas lots of proteins for osmotic balance

Structure/FunctionStructure/Function Blood - cells and extracellular matrix Blood - cells and extracellular matrix

are of equal importanceare of equal importance– Liquid matrix allows for material to be Liquid matrix allows for material to be

dissolved and transported (ex – dissolved and transported (ex – hormones, glucose, amino acids)hormones, glucose, amino acids)

– Cells carry material that can not Cells carry material that can not dissolve in liquid (ex – oxygen)dissolve in liquid (ex – oxygen)

Red blood cellsWhite blood cells andPlatelets all reside in Plasma (liquid matrix)

Muscle TissueMuscle Tissue Shape: Muscle cells Shape: Muscle cells

are also called are also called muscle fibers muscle fibers because the cells because the cells are elongated are elongated (cylindrical or (cylindrical or spindle shaped)spindle shaped)

Function: Length of Function: Length of cell allows for cell allows for contraction; shorten contraction; shorten and thickenand thicken

Three types

Skeletal MuscleSkeletal Muscle LocationLocation – attached to bones – attached to bones FunctionsFunctions – voluntary movement (head, trunk, – voluntary movement (head, trunk,

limbs, facial expressions, write, talk, sing, limbs, facial expressions, write, talk, sing, chew, breathe) and temperature regulationchew, breathe) and temperature regulation

CharacteristicsCharacteristics:: Long (up to 2 inches) and cylindricalLong (up to 2 inches) and cylindrical MultinucleatedMultinucleated Striated (alternating light and dark markings Striated (alternating light and dark markings

due to pattern of actin and myosin)due to pattern of actin and myosin) Voluntary controlVoluntary control

Skeletal MuscleSkeletal Muscle

Cardiac MuscleCardiac Muscle LocationLocation – Heart only – Heart only FunctionFunction – Involuntary pumping of blood from – Involuntary pumping of blood from

heart into blood vesselsheart into blood vessels CharacteristicsCharacteristics::

Cells: long, cylindrical, Cells: long, cylindrical, branched branched Single nucleusSingle nucleus StriatedStriated Involuntarily ControlledInvoluntarily Controlled Has intercalated discs (gap junctions) – Has intercalated discs (gap junctions) –

ions that set off contraction spread from ions that set off contraction spread from cell to cell quicklycell to cell quickly

Intercalated Disc →

Cardiac Muscle

Smooth MuscleSmooth Muscle LocationLocation: Walls of hollow organs (stomach, : Walls of hollow organs (stomach,

intestines, bladder, uterus, blood vessels), intestines, bladder, uterus, blood vessels), glandsglands

FunctionFunction: Squeeze out the contents of an : Squeeze out the contents of an organ such as food through digestive tract or organ such as food through digestive tract or urine from bladder, constricts blood vessels, or urine from bladder, constricts blood vessels, or squeeze hormones down a duct to the bloodsqueeze hormones down a duct to the blood

CharacteristicsCharacteristics Spindle-shaped Spindle-shaped Single central nucleusSingle central nucleus No striationsNo striations Involuntarily controlledInvoluntarily controlled

Smooth Muscle vs. Dense Smooth Muscle vs. Dense CTCT

Long stretched nuclei inside the cells

Nuclei cells are between the fibers

Nervous TissueNervous Tissue

Location: Brain, spinal cord, peripheral Location: Brain, spinal cord, peripheral nervesnerves

Functions:Functions: Communicate quickly with other cells Communicate quickly with other cells Send information from the brain and Send information from the brain and

spinal cord to nervous tissue, muscle spinal cord to nervous tissue, muscle tissue, glandstissue, glands

Carry input from sensory receptors to Carry input from sensory receptors to the brain and spinal cordthe brain and spinal cord

Characteristics of Nervous Characteristics of Nervous TissueTissue

Large cell body with Large cell body with axonaxon which is a long which is a long extension of cytoplasm extension of cytoplasm (may be up to 3 ft.) (may be up to 3 ft.) Many of the long axons Many of the long axons are covered in myelin (a are covered in myelin (a fat) to improve fat) to improve conductivityconductivity

Cell body also has many Cell body also has many short extensions short extensions connecting to other connecting to other close nerve cells called close nerve cells called dendritesdendrites

NeuronNeuron

Cell BodyCell Body

DendriteDendritess

AxonAxon

ReferencesReferences

http://www.cliffsnotes.com/http://www.cliffsnotes.com/study_guide/study_guide/

Holes Human Anatomy and Holes Human Anatomy and PhysiologyPhysiology