Ch3 cells tissues 8 21

© 2013 Pearson Education, Inc.

Compartmentation: Cells and Tissues

Chapter 3a

Cell Membrane: Function

• Physical isolation: separates intracellular fluid from surrounding extracellular environment

• Regulation of exchange with the environment: controls then entry of ions/nutrients/molecules into the cell and regulates the exit of wastes

• Communication between the cell and its environment: contains proteins that allow the cell to change and respond to its external environment

• Structural support: cytoskeleton, junctions between neighboring cells, extracellular matrix-material synthesized and secreted by cells


• Proteins– Integral

– Transmembrane– Lipid-anchored

– Peripheral

Cell Membrane: Composition

• Lipids – Phospholipids– Sphingolipids– Cholesterol

• Carbohydrates– Glycoproteins– Glycolipids


Table 3.1 Composition of Selected Membranes

• ratio of protein to lipid varies widely, depending on cell type• generally, the more metabolically active, the more protein

Figure 3.2a ESSENTIALS – The Cell Membrane

Membrane Phosphlipids

Phospholipid bilayerforms a sheet.

Micelles are droplets of phospholipids. They are important in lipid digestion.

Liposomes havean aqueous center.

Stylizedmodel

Polar head (hydrophilic)

Nonpolar fatty acid tail (hydrophobic)

can arrange themselves as

Membrane phospholipids form bilayers,micelles, or liposomes. They arrangethemselves so that their nonpolar tailsare not in contact with aqueoussolutions such as extracellular fluid.

– Phospholips orient themselves so that polar head interact with water and the non-polar fatty acid tails are sandwiched in between.

– Miscelles are small phospholipids, single layer, important in digestion, absorption of fats

– Sphingolipids: can have glycolipid heads and have longer fatty acid tails, components of lipid rafts

– Cholesterol: hydrophobic, btw heads of phospholipids, add rigidity to membrane, help to make membrane impermeable to small molecules

Figure 3.2b ESSENTIALS – The Cell Membrane

The Fluid Mosaic Model of Biological Membranes

Peripheral proteinscan be removed

without disruptingthe integrity of the

membrane.

Phospholipid headsface the aqueousintracellular and

extracellularcompartments.

Lipid tailsform the

interiorlayer of themembrane.

Cholesterol molecules insertthemselves into the lipid layer.

This membrane-spanning protein

crosses the membraneseven times.

Lipid-anchoredproteins Peripheral

protein

Cytoskeletonproteins.

Cytoplasm

Cellmembrane

Transmembraneproteins cross the lipid bilayer.

Glycoprotein

Carbohydrate

Phosphate

Cytoplasmic loop

Extracellular fluid

Intracellularfluid

COOH

NH2

Figure 3.2c ESSENTIALS – The Cell Membrane

Concept Map of Cell Membrane Components

Cell Membraneconsists of

together form together form together form

CarbohydratesCholesterol Phospholipids, Sphingolipids

Lipid bilayer Glycolipids Glycoproteins

functions as whose functions include

Selective barrier between cytosoland external environment Structural stability Cell recognition Immune response

Proteins

– Integral proteins: tightly bound to membrane, some span the membrane from intracellular to extracellular. Ex. transmembrane proteins

– Peripheral proteins: typically attached to other membrane proteins, sit on the surface of the plasma membrane, often enzymes and structural binding proteins that anchor the cytoskeleton to the membrane

– Transmembrane proteins: proteins extend from intracellular to extracellular, classified into families by number of transmembrane segments (how many loops), some are lipid anchored proteins

Type of membrane bound proteins

Figure 3.3 Lipid rafts are made of sphingolipids

– External to the plamsa membrane, carbohydrates are attached to proteins (glycoproteins) or lipids (glycolipids)

– Glycocalyx: protective layer beyond the plasma membrane, containing glycoproteins and glycolipids. Ex. ABO blood type determined by number and composition of sugars attached to membrane sphingolipids.

Glycocalyx

Cytosol

Extracellular fluid

InclusionsProteinfibers

Membranousorganelles

• Cytoskeleton• Centrioles• Cilia• Flagella

• Lipid droplets• Glycogen

granules• Ribosomes

• Mitochondria• Endoplasmic reticulum• Golgi

apparatus• Lysosomes• Peroxisomes

is composed of

THE CELL

Nucleus Cytoplasm

Cellmembrane

Figure 3.4-1a REVIEW – Cell Structure

Intracellular Compartments

• Cytoplasm: all material inside the cell, besides the nucleus– Cytosol: intracellular fluid, contains dissolved nutrients

and proteins, ions, waste– Inclusions: insoluble material: stored nutrients and non-

membrane bound organelles (ribosomes)– Cytoskeleton: support, transport, communication– Organelles: membrane bound compartments that

perform specific functions. Ex. Mitochondria

• Nucleus: houses DNA, replication occurs


Inclusions Have No Membranes

• No transport required• most inclusion made of protein or protein and RNA

combo• Ribosomes: RNA + protein, manufacture proteins

– Fixed: attached to organelles, rough endoplasmic reticulum

– Free: floating in cytosol– Polyribosomes: group of 10-20 free ribosomes that

form a group


Figure 3.4-2i REVIEW – Cell Structure

The endoplasmic reticulum (ER) is a network of interconnectedmembrane tubes that are a continuation of the outer nuclearmembrane. Rough endoplasmic reticulum has a granularappearance due to rows of ribosomes dotting its cytoplasmicsurface. Smooth endoplasmic reticulum lacks ribosomes andappears as smooth membrane tubes. The rough ER is the main siteof protein synthesis. The smooth ER synthesizes lipids and, insome cells, concentrates and stores calcium ions.

Endoplasmic reticulum (ER)

Smooth ER

Rough ER

Ribosomes

Cytoplasmic Protein Fibers• Protein fibers classified by diameter

• 2 purposes: structural support and movement (of molecules/nutrients with aid of motor proteins)

• Actin (microfilaments): smallest

• Intermediate filaments: next largest– Keratin, Neurofilaments

• Microtubules: hollow, largest, made of protein tubulin– Centrioles, cilia, flagella


Microtubule Function

• Centrosome– Assembles tubulin monomers into microtubules

• Centrioles– Direct DNA movement in cell division

• Cilia– Fluid movement across cells

• Flagella– Cell (sperm) movement through fluid


Cytoskeleton: Function

5 important functions of cytoskeleton:

1. Cell shape : provides mechanical strength and can determine shape of cell, help support microvilli

2. Internal organization: anchor organelles, compartmentalize the cell

3. Intracellular transport: allow for movement of molecules and organelles, act as “roads”

4. Assembly of cells into tissues: connect to extracellular space to link cells together and to outside substances, allow for transfer of information

5. Movement: cell sculls to move (Ex. white blood cells moving in and out of blood vessels), cilia and flagella movements,


Figure 3.4-1b REVIEW – Cell Structure

Cytoskeleton

Microvilli increase cellsurface area. They aresupported by microfilaments.

Intermediate filaments

include myosin and keratin.

Microtubules are the largest cytoskeleton fiber.

Microfilaments form a networkjust inside the cell membrane.

Motor Proteins: Function

• Motor proteins are proteins that are able to covert energy into movement

• Motor proteins associated with the cytoskeleton:

1. Myosins: Muscle contraction

2. Kinesins and dyneins: Movement of vesicles along microtubules

3. Dyneins: Movement of cilia and flagella


Organelle

Direction of movement

ATP

Cytoskeletal fiber

Motorprotein

Figure 3.6 Motor proteins

Mitochondria

• Two membranes create two compartments– Mitochondrial matrix

– Unique DNA– Intermembrane space

– Cellular ATP production


Membrane bound organelles:Mitochondria

– Organelles: subcellular compartments with one or more phospholipid membranes, this allows for the cell to separate substances and functions (like rooms in a house)

– Mitochondria: role is to generate ATP (“power house of the cell”)

– double wall with inner and outer membrane

– mitochondrial matrix

– mitochondrial DNA: made their own proteins and replicate

– intermembrane space: important in ATP production, btw inner and outer membrane

Outer membraneIntermembrane space

Cristae

Matrix

Mitchondria are spherical to elliptical organelles with a doublewall that creates two separate compartments within the organelle.The inner matrix is surrounded by a membrane that folds intoleaflets called cristae. The intermembrane space, which liesbetween the two membranes, plays an important role in ATPproduction. Mitochondria are the site of most ATP synthesis in thecell.

Mitochondria

Endoplasmic Reticulum (ER)

• Network of tubes, purpose is synthesis, storage, and transport of biomolecules

• Rough ER– Ribosomes attached– Protein assembly and modification

• Smooth ER, no ribosomes– Synthesis of fatty acids, steroids, lipids– Modified forms in liver, kidney, muscles (stores Ca2+)


The endoplasmic reticulum (ER) is a network of interconnectedmembrane tubes that are a continuation of the outer nuclearmembrane. Rough endoplasmic reticulum has a granularappearance due to rows of ribosomes dotting its cytoplasmicsurface. Smooth endoplasmic reticulum lacks ribosomes andappears as smooth membrane tubes. The rough ER is the main siteof protein synthesis. The smooth ER synthesizes lipids and, insome cells, concentrates and stores calcium ions.

Endoplasmic reticulum (ER)

Smooth ER

Rough ER

Ribosomes

Golgi Apparatus (Golgi Complex)

• Stacked membranes (cisternae) surrounded by vesicles

• Modifies protein from rough ER• Packages proteins into vesicles


Golgi Apparatus

VesicleCisternae

The Golgi apparatus consists of a series of hollow cured sacscalled cisternae stacked on top of one another and surroundedby vesicles. The Golgi apparatus participates in proteinmodification and packaging.

Cytoplasmic Vesicles

• Secretory vesicles– Released from cell

• Storage vesicles• Lysosomes

– Enzymes to degrade bacteria or old organelles– Acidic interior, enzymes are active only in low pH

• Peroxisomes- smaller than lysosomes– Enzymes to degrade long-chain fatty acids and toxic

foreign molecules– Generate hydrogen peroxide, rapidly convert it to oxygen

and water using catalase© 2013 Pearson Education, Inc.

Lysosomes are small,spherical storage vesiclesthat contain powerfuldigestive enzymes.

Lysosomes Peroxisomes

Peroxisomes containenzymes that break downfatty acids and some foreignmaterials.

Nucleus• Houses DNA

• Nuclear envelope: two membranes, nuclear pores

• Nuclear pore complex: large protein complex with central channel that regulates what goes through (ions flow thru when open, lg proteins and RNA require energy)

• Chromatin: DNA and associated proteins

• Nucleoli: dark area – Control RNA synthesis: contains DNA and proteins that

control the synthesis of RNA for ribosomes


Nucleus

Nucleolus

Nuclearpores

Nuclearenvelope

The nucleus is surrounded by a double-membrane nuclearenvelope. Both membranes of the envelope are pierced here andthere by pores to allow communication with the cytoplasm. Theouter membrane of the nuclear envelope connects to the endoplasmic reticulum membrane. In cells that are not dividing,the nucleus appears filled with randomly scattered granularmaterial composed of DNA and proteins. Usually a nucleus alsocontains from one to four larger dark-staining bodies of DNA, RNA,and protein called nucleoli.

Figure 3.7 Protein synthesis

Ribosome

mRNA

DNA

Nucleus

Nuclearpore

Endoplasmicreticulum

Targetedproteins

Growing amino-acid

chainCytosolicprotein

Peroxisome

Transport vesicle

RetrogradeGolgi-ERtransport

Golgi apparatus

Golgi

Golgiapparatus

Secretory vesicle

Lysosome or storage vesicle

Cell membrane

Cytosol

Extracellular fluid

Mitochondrion

Proteins are modified as they passthrough the lumen of the ER.

mRNA is transcribed from genes inthe DNA.

mRNA leaves the nucleus and attachesto cytosolic ribosomes, initiating proteinsynthesis.

Some proteins are released by freeribosomes into the cytosol or are targetedto specific organelles.

Ribosomes attached to the roughendoplasmic reticulum direct proteinsdestined for packaging into the lumen ofthe rough ER.

Transport vesicles move the proteins fromthe ER to the Golgi apparatus.

Golgi cisternae migrate toward the cellmembrane.

Some vesicles bud off the cisternae andmove in a retrograde or backward fashion.

Some vesicles bud off to form lysosomesor storage vesicles.

Other vesicles become secretory vesiclesthat release their contents outside the cell.

Tissues of the Body

Primary Tissue Types

• Histology: study of tissue structure and function• Types of Tissues

• Epithelial• Connective • Muscle• Neural/nerve


Extracellular Matrix

• Synthesized and secreted by cells• Vary from cell type to cell type• 2 Components

1. Proteoglycans• Glycoproteins

2. Insoluble protein fibers• Examples: collagen, fibronectin, laminin• Strength• Anchor cells to matrix for communication


Cell Junctions and Cell Adhesion Molecules (CAMs)• Cell Adhesion Molecules (CAMs): membrane spanning proteins responsible for cell

junctions and cell adhesion (temp)• Cell to cell

– Gap junction (communicating junction): allow direct and quick cell-cell communication, connexin proteins act as channels that regulate movements of ions and small molecules, allow chemical and electrical signal to move rapidly from one cell to the next, present in nerve, muscle,liver, pancreas, ovary, thyroid, during development

– Tight junction (occluding junction): limit the movement of material btw cells, cell membranes are partially fused by claudins and occludins, “tightness” varies. Ex. kidneys, digestive tract, blood-brain barrier

– Anchoring junction-hold position, like a picket fence– Cell–cell with cadherins

– Adherens junctions: link actin fibers in adj cells– Desmosomes: attache to intermediate filaments of cytoskeleton, strongest cell-cell junction

– Cell–matrix with integrins: can also act as signaling molecules, transferring information from the environment

– Hemidesmosomes: anchor intermediate filaments of cytoskeleton to cell matrix, like laminin– Focal adhesions: actin to matrix proteins, like fibronectin


Table 3.3 Major Cell Adhesion Molecules (CAMs)

Figure 3.8a ESSENTIALS – Cell Junctions

CELL JUNCTIONS

Function

Matrixprotein

Type

Location

Membraneprotein

Cytoskeletonfiber

Gap junction

Tight junction

Adherens junction

Focaladhesion

Hemi-desmosome

Desmosome

Claudin,occludin

Intermediatefilaments

Connexin Cadherin Integrin

Actin Actin Actin

Laminin

Keratin (intermediate

filaments)

Fibronectin and otherproteins

AnchoringOccludingCommunicating

Cell-cell junctions Cell-matrix junctions

Cellmembrane

Intercellular space

Connexinproteins

Cytosol

Cell2

Cell1

Clusters of gapjunctions

Freeze fracture of cell membrane

Gap junctions arecommunicatingjunctions.

Figure 3.8b ESSENTIALS – Cell Junctions

Figure 3.8c ESSENTIALS – Cell Junctions

Claudinand occludinproteins

Intercellular space

Cellmembrane Cell

2Cell1

Tight junctionsare occludingjunctions.

Tight junctionsprevent

movementbetween cells.

Adherensjunction

Cytosol

Cadherinproteins

Intermediatefilament

Plaqueglycoproteins

Intercellularspace

Cellmembrane

A desmosome is acell-to-cell anchoringjunction.

Adherensjunction

Desmosomes anchorcells to each other.

Tight junctionsprevent

movementbetween cells.

Figure 3.8d ESSENTIALS – Cell Junctions

Epithelial Tissue: Structure

• One or more layers of epithelial cells• Separated from underlying tissue by basal lamina or

basement membrane: composed of collagen and laminin embedded in proteoglycans that hold the epithelial cells to underlying layers

• Cell junctions varied as “leaky” (Ex. capillaries) or “tight” (Ex. kidneys)

• Two types– Sheets of cells lining body surfaces– Secretory epithelia that make and release substances


1) Epithelial

• Protect the internal layers of the body, regulate exchange of materials btw internal and external

Figure 3.9c ESSENTIALS – Epithelial Tissue

Epithelial cells attachto the basal laminausing cell adhesionmolecules.

Basal lamina(basement membrane)is an acellular matrixlayer that is secretedby the epithelial cells.

Underlying tissue

Most epithelia attach to an underlyingmatrix layer called the basal laminaor basement membrane.

Epithelial Tissue: Classified

• Epithelial Classified by # of layers and shape of cells in surface layer

• Layering– Simple or stratified

• Shapes– Squamous, cuboidal, columnar

• Classify by Function:

1)exchange 2) transporting 3) ciliated 4) protective 5)secretory


Figure 3.10 ESSENTIALS – Types of Epithelia

Figure 3.9b ESSENTIALS – Epithelial Tissue

This diagramshows thedistribution ofthe five kindsof epithelia inthe bodyoutlined in thetable above.

Respiratorysystem

Circulatorysystem

Integumentary System

Digestivesystem

Urinarysystem

Musculo-skeletalsystem

Reproductivesystem

Cells

KEY Secretion Exchange

Figure 3.10a ESSENTIALS – Types of Epithelia

Exchange Epithelium

The thin, flat cells ofexchange epitheliumallow movement throughand between the cells.

Capillary

Capillary epithelium

Extracellular fluid

Blood

Pore

– Exchange epithelia: composed of thin, flattened cells that allow gases to pass across rapidly, lines blood vessels land lungs, gaps btw cells also allow for passage of material=“leaky”

– histology=simple squamous

Figure 3.10e ESSENTIALS – Types of Epithelia

Transporting Epithelium

Transporting epithelia selectively move substances between a lumen and the ECF.

Apical membrane

Tight junctions in atransporting

epithelium preventmovement between

adjacent cells.Substances must

instead pass throughthe epithelial cell,

crossing twophospholipid cell

membranes asthey do so.

Lumen of intestine or kidney

Extracellular fluid

Transportingepithelial

cell

Microvilli

Basolateral membrane

• actively and selectively regulates exchange of material (not gases, ions, molecules)

• digestive and kidneys

• absorption: external to internal

• secretion: internal to external

Transporting Epithelium: Characteristics

• Cell shape: cells much thicker than exchange epithelia cells, act as a barrier, 1 cell thick but cuboidal or columnar

• Membrane modification– Apical membrane: microvilli that increase the surface area

for transport– Basolateral membrane: side that faces extracellular

membrane/matrix: may have folds to increase surface area

• Cell junctions: firmly attached to adj cells, • Cell organelles: lots of mitochondria to generate ATP for

transport• Hormones can control the transport of ions (Ex. kidneys


Figure 3.10c ESSENTIALS – Types of Epithelia

Ciliated Epithelium

Beating cilia create fluidcurrents that sweep across the epithelial surface.

Cilia

Microvilli

Basal lamina

Mitochondrion

NucleusGolgi apparatus

SEM of the epithelialsurface of an airway

• non-transporting tissues, line respiratory tract and female reproductive tract

• surface of tissue facing lumen are lined with cilia

• move rhythmic fashion

Figure 3.10b ESSENTIALS – Types of Epithelia

Protective Epithelium

Protective epithelia havemany stacked layers ofcells that are constantlybeing replaced. This figure shows layers inskin (see Focus on Skin, p. 91).

Section of skinshowing cell layers.

Epithelialcells

• prevents exchange btw internal and external environments to protect areas from mechanical or chemical stresses

• stratified tissues• toughened by keratin• epidermis, mouth,

pharynx, esophagus• because their role is

protective and they are often damaged their lifespan is short

• new cells in the deeper layers replace older cells on surface

Figure 3.10d ESSENTIALS – Types of Epithelia

Secretory Epithelium

Secretory epithelial cellsmake and release a product.Exocrine secretions, such asthe mucus shown here, aresecreted outside the body.The secretions of endocrinecells (hormones) arereleased into the blood.

Goblet cells secrete mucusinto the lumen of holloworgans such as the intestine.

Golgiapparatus

Nucleus

SEM of goblet cell

Mucus

Secretory Epithelium

• Scattered among epithelium • Grouped into multicellular glands

– Exocrine: release products to external environment (most through ducts) onto the surface of skin or epithelium – Exocrin glands produce 2 types of secretions:1. Serous secretions: watery solutions (many with enzymes).

Tears, sweat, digestive enzyme solutions

2. Mucous secretions/mucus: sticky solutions, contain glycoproteins, produced by goblet cells (single exocrine cell), can act as lubricant (swallowed food) or as a protective barrier (nasal passage ways)

– Endocrine: ductless, release hormones into extracellular compartments, hormones enter blood stream© 2013 Pearson Education, Inc.

Figure 3.11 Development of endocrine and exocrine glands from epithelium

Epithelium

Connectivetissue

EndocrineExocrine

Blood vessel

Duct

Connectingcells disappear

Exocrinesecretory cells

Endocrinesecretory cells

2)Connective Tissue

– Many roles and many types of tissues– Distinguishing factor=extensive matrix with widely

scattered cells that secret and modify the matrix– Ex. bone, blood, cartilage, adipose,

Connective Tissues: Structure

• Ground substance= extracellular matrix of connective tissue, contains proteoglycans and water with insoluble proteins– Highly variable consistency, depends on type (Ex. blood vs bone)

• Cells: lie embedded in the matrix– Fixed: if they remain in one place

– Blasts, clasts, and cytes– Mobile: if they move (immune cells)

• Matrix fibers (non-living): constantly modified by cells– Collagen: most abundant (bone, skin, muscles), flexible but inelastic– Elastin: returns to length following stretching– Fibrillin: elastin combines with fibrillin to form sheets of elastic

fibers (lungs, blood vessels, skin)– Fibronectin: connect cells to extracellular matrix, plays role in

wound healing, blood clotting


Figure 3.12a-1 ESSENTIALS – Connective Tissue

Fixed

Macrophages

Mobile

Blood cells

Cells

is composed of

CONNECTIVE TISSUE

Red bloodcells

White bloodcells Adipocytes Fibroblasts

synthesizeFight invaders Store energy in fat

O2 and CO2

transport

Matrix

Figure 3.12a-2 ESSENTIALS – Connective Tissue

Mineralized

• Loose connective tissue• Dense connective tissue• Cartilage• Adipose tissue

Gelatinous

Bone

Syrupy Watery

Bloodplasma

Ground substance

Fibronectin Fibrillin Elastin Collagen

Protein fibers

can be divided into

Stiff butflexible

Stretchand recoil

Formsfilaments

and sheets

Connectscells tomatrix

Matrix

Cells

is composed of

CONNECTIVE TISSUE

Figure 3.12b ESSENTIALS – Connective Tissue

Types of Connective Tissues

Most common types:

1. loose connective tissue

2. dense connective tissue

3. adipose tissue

4. blood

5. cartilage

6. bone

Figure 3.13a ESSENTIALS – Types of Connective Tissue

Loose Connective Tissue

Loose connectivetissue is very flexible,with multiple celltypes and fibers.

Light micrograph of looseconnective tissue

Fibroblasts arecalled that secrete

matrix proteins.Ground substanceis the matrix of looseconnective tissue.

Collagen fibers

Elastic fibers

Free macrophage

– Loose connective tissues: elastic tissue that underlie skin and provide some support for small glands

Dense Connective Tissues

• Provides strength and flexibility• Tendons: collagen, lack ability to stretch (no elastic

fibers)– Skeletal muscles to bone

• Ligaments: collagen and elastic fibers– Bones to bones


Figure 3.13c ESSENTIALS – Types of Connective Tissue

Dense Regular Connective Tissue

Collagen fibers of tendonare densely packed intoparallel bundles.

Collagen fibers

Light micrograph of tendon

Supporting Connective Tissues

• Cartilage– Solid and flexible– Lacks blood supply: nutrients and oxygen reach cells

by diffusion (slow healing)– Nose, ears, knee, windpipe/trachea

• Bone – Calcified: mineral deposits (calcium phosphate)– Strong and rigid


Figure 3.13b ESSENTIALS – Types of Connective Tissue

Bone and Cartilage

Hard bone forms when osteo-blasts deposit calciumphos-phate crystals in the matrix. Cartilage has firm but flexible matrix secreted by cells called chondrocytes.

Chondrocytes

Light micrograph of hyaline cartilage

Matrix

Matrix

Light micrograph of bone

Additional Connective Tissues

• Adipose connective tissue: adipocytes– White

– Single lipid droplet– Brown (temp regulation in infants)

– Multiple lipid droplets

• Blood – Plasma matrix: ions and dissolved molecules, gases,

glucose (insoluble protein fibers that are in other connective tissues, such as collagen, are absent)

– Free blood cells


Figure 3.13e ESSENTIALS – Types of Connective Tissue

Adipose Tissue

In white fat, the cell cytoplasm is almostentirely filled with lipid droplets.

Lipid droplets

Light micrograph of adipose tissue

Nucleus

Figure 3.13d ESSENTIALS – Types of Connective Tissue

Blood

Blood consists of liquid matrix (plasma) plus red andwhite blood cells and the cell fragments called platelets.

PlateletRed blood cell

Lymphocyte

Neutrophil

Eosinophil

WhiteBloodCells

Light micrograph ofa blood smear

Muscle Tissues

• Excitable: ability to generate and propagate electrical signals (action potentials)

• minimal matrix (supportive matrix called external lamina)• Contractile

– Force and movement

• Three types– Cardiac– Smooth– Skeletal


Figure 12.1a The Three Types of Muscle

Figure 12.1b The Three Types of Muscle

Figure 12.1c The Three Types of Muscle

Nervous Tissues

• 2 Types:• Neurons (nerve cells) send signals

– Excitable

• Glial cells (neuroglia) “support”, regulation of neurotransmitters, ions, internal environment, fluid, insulation btw neurons, pathogen removal


Figure 8.2f Nervous Tissue

Parts of a Neuron

Nucleus

Dendrites

Inputsignal

Cellbody

Integration Output signal

Axonhillock

Axon (initialsegment)

Myelin sheath Postsynapticneuron

Presynapticaxon terminal

Synapticcleft

Postsynapticdendrite

Synapse: Theregion where anaxon terminalcommunicateswith itspostsynaptictarget cell

Table 3.4 Characteristics of the Four Tissue Types

Tissue Remodeling

• Cell death– Necrosis: physical trauma, toxins, lack of oxygen

– cells swell, organelles detoriate, and cells rupture– releases digestive enzymes to neighboring cells=damaging or leads to

inflammation – Apoptosis (programmed cell death, cell suicide): do not disrupt neighboring cells,

signals to immune cells to engulf– normal event – common during development to remove unneeded cells

• Stem cells– Totipotent– Pluripotent– Multipotent


Organs

• Groups of tissues with related function• Skin as an example of an organ


The layers of the skin

Hair follicles secrete thenonliving keratin shaft ofhair.

Sweat glands secrete a dilutesalt fluid to cool the body.

Sensory receptors monitorexternal conditions.

Epidermis consists of multiplecell layers that create a

protective barrier.

The dermis is loose connectivetissue that contains exocrine

glands, blood vessels, muscles,and nerve endings.

Sebaceous glands areexocrine glands thatsecrete a lipid mixture.

Hypodermis contains adiposetissue for insulation.

Apocrine glands in the genitalia, anus,axillae (axilla, armpit), and eyelids releasewaxy or viscous milky secretions inresponse to fear or sexual excitement.

Blood vessels extendupward into the dermis.

Sensorynerve

Artery Vein

Arrector pili muscles pullhair follicles into a verticalposition when the musclecontracts, creating “goosebumps.”

Figure 3.15-1 FOCUS ON … The Skin (1 of 4)


Epidermis The skin surface is a mat oflinked keratin fibers left behindwhen old epithelial cells die.

Phospholipid matrix acts as theskin’s main waterproofing agent.

Surface keratinocytes producekeratin fibers.

Desmosomes anchor epithelialcells to each other.

Melanocytes containthe pigment melanin.

Epidermal cell

Basal lamina


Connection between epidermis and dermis

Basal lamina orbasement membrane is anacellular layer betweenepidermis and dermis.

Hemidesmosomes tieepidermal cells to fibersof the basal lamina.

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