cells and tissues – part i cell structures

Cells and Tissues – Part ICell Structures

Chapter 3Kelly Trainor

BIO 160

ObjectivesIdentify the three major cell regions (nucleus, cytoplasm, and

plasma membrane).Describe selective permeability, diffusion, osmosis, and the various

transport processes allowing solutes and molecules to pass through a membrane.

Cells and TissuesCarry out all chemical activities needed to sustain lifeCells are the building blocks of all living thingsTissues are groups of cells that are similar in structure and functionCells are not all the sameAll cells share general structuresAll cells have three main regions

NucleusCytoplasmPlasma membrane

Cytoplasmic Organelles

Cellular ProjectionsNot found in all cellsUsed for movement

Cilia move materials across the cell surface Located in the respiratory system to move mucus

Flagella propel the cell The only flagellated cell in the human body is sperm

Cell Diversity

Cell Diversity

Cell Physiology: Membrane TransportMembrane transport—movement of substances into and out of the

cellTwo basic methods of transport

Passive transport No energy is required

Active transport Cell must provide metabolic energy (ATP)

Solutions and TransportSolution—homogeneous mixture of two or more components

Solvent—dissolving medium; typically water in the bodySolutes—components in smaller quantities within a solution

Intracellular fluid—nucleoplasm and cytosolInterstitial fluid—fluid on the exterior of the cell

Selective PermeabilityThe plasma membrane allows some materials to pass while

excluding othersThis permeability influences movement both into and out of the cell

Passive Transport ProcessesDiffusion

Particles tend to distribute themselves evenly within a solutionMovement is from high concentration to low concentration, or

down a concentration gradient

Passive Transport ProcessesTypes of diffusion

Simple diffusion An unassisted process Solutes are lipid-soluble

materials or small enough to pass through membrane pores

Passive Transport ProcessesTypes of diffusion (continued)

Osmosis—simple diffusion of water Highly polar water molecules easily

cross the plasma membrane

Passive Transport ProcessesFacilitated diffusion

Substances require a protein carrier for passive transport

Transports lipid-insoluble and large substances

Active Transport ProcessesSubstances are transported that are unable to pass by diffusion

Substances may be too largeSubstances may not be able to dissolve in the fat core of the

membraneSubstances may have to move against a concentration gradient

ATP is used for transport

Active Transport ProcessesTwo common forms of active transport

Active transport (solute pumping)Vesicular transport

Exocytosis Endocytosis

PhagocytosisPinocytosis

Active Transport ProcessesActive transport (solute pumping)

Amino acids, some sugars, and ions are transported by protein carriers called solute pumps

ATP energizes protein carriersIn most cases, substances are moved against concentration

gradients

Active Transport ProcessesVesicular transport

Exocytosis Moves materials out of the cell Material is carried in a membranous vesicle Vesicle migrates to plasma membrane Vesicle combines with plasma membrane Material is emptied to the outside

Active Transport ProcessesVesicular transport (continued)

Endocytosis Extracellular substances are engulfed by being enclosed in a

membranous vescicleTypes of endocytosis

Phagocytosis—“cell eating” Pinocytosis—“cell drinking”

Cells and Tissues – Part IITissue Types

Chapter 3Kelly Trainor

BIO 160

ObjectivesName the four major tissue types, their chief subcategories and

explain how they differ structurally and functionally.Give the chief locations of the various tissue types in the body.

Body TissuesTissues

Groups of cells with similar structure and functionFour primary types

Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue

Epithelial TissuesLocations

Body coveringsBody liningsGlandular tissue

FunctionsProtectionAbsorptionFiltrationSecretion

Epithelium CharacteristicsCells fit closely together and

often form sheetsThe apical surface is the free

surface of the tissueThe lower surface of the

epithelium rests on a basement membrane

Avascular (no blood supply)Regenerate easily if well

nourished

Classification of EpitheliaNumber of cell layers

Simple—one layerStratified—more than one layer

Classification of EpitheliaShape of cells

Squamous flattened

Cuboidal cube-shaped

Columnar column-like

Figure 3.17b

Simple EpitheliaSimple squamous

Single layer of flat cellsUsually forms membranes

Lines body cavities Lines lungs and capillaries

Simple EpitheliaSimple cuboidal

Single layer of cube-like cellsCommon in glands and their ductsForms walls of kidney tubulesCovers the ovaries

Simple EpitheliaSimple columnar

Single layer of tall cellsOften includes mucus-producing goblet cellsLines digestive tract

Simple EpitheliaPseudostratified columnar

Single layer, but some cells are shorter than othersOften looks like a double layer of cellsSometimes ciliated, such as in the respiratory tractMay function in absorption or secretion

Stratified EpitheliaStratified squamous

Cells at the apical surface are flattenedFound as a protective covering where friction is commonLocations

Skin Mouth Esophagus

Stratified EpitheliaStratified cuboidal—two layers of cuboidal cellsStratified columnar—surface cells are columnar, cells underneath

vary in size and shapeStratified cuboidal and columnar

Rare in human bodyFound mainly in ducts of large glands

Stratified EpitheliaTransitional epithelium

Shape of cells depends upon the amount of stretchingLines organs of the urinary system

Glandular EpitheliumGland

One or more cells responsible for secreting a particular productTwo major gland types

Endocrine gland Ductless since secretions diffuse into blood vessels All secretions are hormones

Exocrine gland Secretions empty through ducts to the epithelial surface Include sweat and oil glands

Connective TissueFound everywhere in the bodyIncludes the most abundant and widely distributed tissuesFunctions

Binds body tissues togetherSupports the bodyProvides protection

Connective Tissue CharacteristicsVariations in blood supply

Some tissue types are well vascularizedSome have a poor blood supply or are avascular

Extracellular matrixNon-living material that surrounds living cells

Extracellular MatrixTwo main elements

Ground substance—mostly water along with adhesion proteins and polysaccharide molecules

Fibers Produced by the cells Three types

Collagen (white) fibersElastic (yellow) fibersReticular fibers

Connective Tissue TypesBone (osseous tissue)

Composed of Bone cells in lacunae (cavities) Hard matrix of calcium salts Large numbers of collagen fibers

Used to protect and support the body

Connective Tissue TypesHyaline cartilage

Most common type of cartilage

Composed of Abundant collagen fibers Rubbery matrix

Locations Larynx Entire fetal skeleton prior to

birth

Connective Tissue TypesElastic cartilage

Provides elasticityLocation

Supports the external earFibrocartilage

Highly compressibleLocation

Forms cushion-like discs between vertebrae

Connective Tissue TypesDense connective tissue (dense

fibrous tissue)Main matrix element is collagen

fiberFibroblasts are cells that make

fibersLocations

Tendons—attach skeletal muscle to bone

Ligaments—attach bone to bone at joints

Dermis—lower layers of the skin

Connective Tissue TypesLoose connective tissue types

Areolar tissue Most widely distributed

connective tissue Soft, pliable tissue like

“cobwebs” Functions as a packing tissue Contains all fiber types Can soak up excess fluid

(causes edema)

Connective Tissue TypesLoose connective tissue types

Adipose tissue Matrix is an areolar tissue in

which fat globules predominate

Many cells contain large lipid deposits

Functions Insulates the bodyProtects some organsServes as a site of fuel

storage

Connective Tissue TypesLoose connective tissue types

Reticular connective tissue Delicate network of

interwoven fibers Forms stroma (internal

supporting network) of lymphoid organsLymph nodesSpleenBone marrow

Connective Tissue TypesBlood (vascular tissue)

Blood cells surrounded by fluid matrix called blood plasmaFibers are visible during clottingFunctions as the transport vehicle for materials

Muscle TissueFunction is to produce movementThree types

Skeletal muscleCardiac muscleSmooth muscle

Muscle Tissue TypesSkeletal muscle

Under voluntary controlContracts to pull on bones or

skinProduces gross body

movements or facial expressions

Characteristics of skeletal muscle cells Striated Multinucleate (more than

one nucleus) Long, cylindrical

Muscle Tissue TypesCardiac muscle

Under involuntary controlFound only in the heartFunction is to pump bloodCharacteristics of cardiac

muscle cells Cells are attached to other

cardiac muscle cells at intercalated disks

Striated One nucleus per cell

Muscle Tissue TypesSmooth muscle

Under involuntary muscleFound in walls of hollow organs

such as stomach, uterus, and blood vessels

Characteristics of smooth muscle cells No visible striations One nucleus per cell Spindle-shaped cells

Nervous TissueComposed of neurons and nerve support cellsFunction is to send impulses to other areas of the body

IrritabilityConductivity