Cell and tissues

Copyright © 2010 Pearson Education, Inc.

CELL AND TISSUE


Cell Theory

• The cell is the smallest structural and functional living unit

• Organismal functions depend on individual and collective cell functions

• Over 200 different types of human cells

• Types differ in size, shape, subcellular components, and functions


Fibroblasts

Erythrocytes

Epithelial cells

(d) Cell that fights disease

Nerve cell

Fat cell

Sperm

(a) Cells that connect body parts, form linings, or transport gases

(c) Cell that storesnutrients

(b) Cells that move organs and body parts

(e) Cell that gathers information and control body functions

(f) Cell of reproduction

SkeletalMusclecell

Smoothmuscle cells

Macrophage

Figure 3.1


Generalized Cell

• All cells have some common structures and functions

• Human cells have three basic parts:

• Plasma membrane—flexible outer boundary

• Cytoplasm—intracellular fluid containing organelles

• Nucleus—control center

Copyright © 2010 Pearson Education, Inc. Figure 3.2

Secretion beingreleased from cellby exocytosis

Peroxisome

Ribosomes

Roughendoplasmicreticulum

Nucleus

Nuclear envelopeChromatin

Golgi apparatus

Nucleolus

Smooth endoplasmicreticulum

Cytosol

Lysosome

Mitochondrion

CentriolesCentrosomematrix

Cytoskeletalelements• Microtubule• Intermediate filaments

Plasmamembrane


Plasma Membrane

• Bimolecular layer of lipids and proteins in a constantly changing fluid mosaic

• Plays a dynamic role in cellular activity

• Separates intracellular fluid (ICF) from extracellular fluid (ECF)

• Interstitial fluid (IF) = ECF that surrounds cells


Membrane Transport

• Plasma membranes are selectively permeable

• Some molecules easily pass through the membrane; others do not


Types of Membrane Transport

• Passive processes

• No cellular energy (ATP) required

• Substance moves down its concentration gradient

• Active processes

• Energy (ATP) required

• Occurs only in living cell membranes


Passive processes

• Simple diffusion - substances diffuse directly through the plasma membrane

• Facilitated diffusion - certain molecules (e.g., glucose, amino acids, and ions) use carrier proteins or channel proteins to pass through the membrane

• Osmosis - movement of solvent (water) across a selectively permeable membrane


Passive Processes

• What determines whether or not a substance can passively permeate a membrane?

1. Lipid solubility of substance

2. Channels of appropriate size

3. Carrier proteins

PLAYPLAY Animation: Membrane Permeability

Copyright © 2010 Pearson Education, Inc. Figure 3.8a

(a) Membrane permeable to both solutes and water

Solute and water molecules move down their concentration gradientsin opposite directions. Fluid volume remains the same in both compartments.

Leftcompartment:Solution withlower osmolarity

Rightcompartment:Solution with greater osmolarity

Membrane

H2O

Solute

Solutemolecules(sugar)

Both solutions have thesame osmolarity: volumeunchanged

Copyright © 2010 Pearson Education, Inc. Figure 3.8b

(b) Membrane permeable to water, impermeable to solutes

Both solutions have identicalosmolarity, but volume of thesolution on the right is greaterbecause only water is free to move

Solute molecules are prevented from moving but water moves by osmosis.Volume increases in the compartment with the higher osmolarity.

Leftcompartment

Rightcompartment

Membrane

Solutemolecules(sugar)

H2O


Tissues

• Groups of cells similar in structure and function

• Types of tissues

• Epithelial tissue

• Connective tissue

• Muscle tissue

• Nerve tissue


Nervous tissue: Internal communication• Brain, spinal cord, and nerves

Muscle tissue: Contracts to cause movement• Muscles attached to bones (skeletal)• Muscles of heart (cardiac)• Muscles of walls of hollow organs (smooth)

Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters• Skin surface (epidermis)• Lining of GI tract organs and other hollow organs

Connective tissue: Supports, protects, bindsother tissues together• Bones• Tendons• Fat and other soft padding tissue


Epithelial Tissue (Epithelium)

• Two main types (by location):

1. Covering and lining epithelia

• On external and internal surfaces

2. Glandular epithelia

• Secretory tissue in glands


Characteristics of Epithelial Tissue

1. Cells have polarity—apical (upper, free) and basal (lower, attached) surfaces

• Apical surfaces may bear microvilli (e.g., brush border of intestinal lining) or cilia (e.g., lining of trachea)

• Noncellular basal lamina of glycoprotein and collagen lies adjacent to basal surface


Characteristics of Epithelial Tissue

2. Are composed of closely packed cells

• Continuous sheets held together by tight junctions and desmosomes

3. Supported by a connective tissue reticular lamina (under the basal lamina)

4. Avascular but innervated

5. High rate of regeneration


Classification of Epithelia

• Ask two questions:

1. How many layers?

1 = simple epithelium

>1 = stratified epithelium


Stratified

Simple

Apical surface

Basal surface

Apical surface

Basal surface

(a) Classification based on number of cell layers.


Classification of Epithelia

2. What type of cell?

• Squamous

• Cuboidal

• Columnar


Squamous

Cuboidal

Columnar(b) Classification based on cell shape.


Overview of Epithelial Tissues

• For each of the following types of epithelia, note:

• Description

• Function

• Location


(a) Simple squamous epithelium

Description: Single layer of flattenedcells with disc-shaped central nucleiand sparse cytoplasm; the simplestof the epithelia.

Function: Allows passage ofmaterials by diffusion and filtrationin sites where protection is notimportant; secretes lubricatingsubstances in serosae.

Location: Kidney glomeruli; air sacsof lungs; lining of heart, bloodvessels, and lymphatic vessels; liningof ventral body cavity (serosae).

Photomicrograph: Simple squamous epitheliumforming part of the alveolar (air sac) walls (125x).

Air sacs oflung tissue

Nuclei ofsquamousepithelialcells


Epithelia: Simple Squamous

• Two other locations

• Endothelium

• The lining of lymphatic vessels, blood vessels, and heart

• Mesothelium

• The epithelium of serous membranes in the ventral body cavity


(b) Simple cuboidal epithelium

Description: Single layer ofcubelike cells with large,spherical central nuclei.

Function: Secretion andabsorption.

Location: Kidney tubules;ducts and secretory portionsof small glands; ovary surface.

Photomicrograph: Simple cuboidalepithelium in kidney tubules (430x).

Basementmembrane

Connectivetissue

Simplecuboidalepithelialcells

Copyright © 2010 Pearson Education, Inc. Figure 4.3c

(c) Simple columnar epithelium

Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells).

Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action.

Location: Nonciliated type lines most of the digestive tract (stomach to anal canal),gallbladder, and excretory ducts of someglands; ciliated variety lines small bronchi, uterine tubes, and some regionsof the uterus.

Photomicrograph: Simple columnar epitheliumof the stomach mucosa (860X).

Simplecolumnarepithelialcell

Basementmembrane

Copyright © 2010 Pearson Education, Inc. Figure 4.3d

(d) Pseudostratified columnar epithelium

Description: Single layer of cells ofdiffering heights, some not reachingthe free surface; nuclei seen atdifferent levels; may contain mucus-secreting cells and bear cilia.

Function: Secretion, particularly ofmucus; propulsion of mucus byciliary action.

Location: Nonciliated type in male’ssperm-carrying ducts and ducts oflarge glands; ciliated variety linesthe trachea, most of the upperrespiratory tract.

Photomicrograph: Pseudostratified ciliatedcolumnar epithelium lining the human trachea (570x).

Trachea

Cilia

Pseudo-stratifiedepitheliallayer

Basementmembrane

Mucus ofmucous cell

Copyright © 2010 Pearson Education, Inc. Figure 4.3e

(e) Stratified squamous epithelium

Description: Thick membranecomposed of several cell layers;basal cells are cuboidal or columnarand metabolically active; surfacecells are flattened (squamous); in thekeratinized type, the surface cells arefull of keratin and dead; basal cellsare active in mitosis and produce thecells of the more superficial layers.

Function: Protects underlyingtissues in areas subjected to abrasion.

Location: Nonkeratinized type formsthe moist linings of the esophagus,mouth, and vagina; keratinized varietyforms the epidermis of the skin, a drymembrane.

Photomicrograph: Stratified squamous epitheliumlining the esophagus (285x).

Stratifiedsquamousepithelium

Nuclei

Basementmembrane

Connectivetissue


Epithelia: Stratified Cuboidal

• Quite rare in body

• Found in some sweat and mammary glands

• Typically two cell layers thick


Epithelia: Stratified Columnar

• Limited distribution in body

• Small amounts in pharynx, male urethra, and lining some glandular ducts

• Also occurs at transition areas between two other types of epithelia

Copyright © 2010 Pearson Education, Inc. Figure 4.3f

(f) Transitional epithelium

Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells domeshaped or squamouslike, depending on degree of organ stretch.

Function: Stretches readily and permits distension of urinary organ by contained urine.

Location: Lines the ureters, urinary bladder, and part of the urethra.

Photomicrograph: Transitional epithelium lining the urinary bladder, relaxed state (360X); note the bulbous, or rounded, appearance of the cells at the surface; these cells flatten and become elongated when the bladder is filled with urine.

BasementmembraneConnectivetissue

Transitionalepithelium


Connective Tissue

• Most abundant and widely distributed tissue type

• Four classes

• Connective tissue proper

• Cartilage

• Bone tissue

• Blood


Major Functions of Connective Tissue

• Binding and support

• Protection

• Insulation

• Transportation (blood)


Characteristics of Connective Tissue

• Connective tissues have:

• Mesenchyme as their common tissue of origin

• Varying degrees of vascularity

• Cells separated by nonliving extracellular matrix (ground substance and fibers)


Structural Elements of Connective Tissue

• Three types of fibers

• Collagen (white fibers)

• Strongest and most abundant type

• Provides high tensile strength

• Elastic

• Networks of long, thin, elastin fibers that allow for stretch

• Reticular

• Short, fine, highly branched collagenous fibers


Structural Elements of Connective Tissue

• Cells

• Mitotically active and secretory cells = “blasts”

• Mature cells = “cytes”

• Fibroblasts in connective tissue proper

• Chondroblasts and chondrocytes in cartilage

• Osteoblasts and osteocytes in bone

• Hematopoietic stem cells in bone marrow

• Fat cells, white blood cells, mast cells, and macrophages


Macrophage

Fibroblast

Lymphocyte

Fat cell

Mast cell

Neutrophil

Capillary

Cell types Extracellularmatrix

Fibers• Collagen fiber• Elastic fiber• Reticular fiber

Ground substance


Overview of Connective Tissues

• For each of the following examples of connective tissue, note:

• Description

• Function

• Location


Connective Tissue Proper

• Types:

• Loose connective tissue

• Areolar

• Adipose

• Reticular

• Dense connective tissue

• Dense regular

• Dense irregular

• Elastic


(a) Connective tissue proper: loose connective tissue, areolar

Description: Gel-like matrix with allthree fiber types; cells: fibroblasts,macrophages, mast cells, and somewhite blood cells.

Function: Wraps and cushionsorgans; its macrophages phagocytizebacteria; plays important role ininflammation; holds and conveystissue fluid.

Location: Widely distributed underepithelia of body, e.g., forms laminapropria of mucous membranes;packages organs; surroundscapillaries.

Photomicrograph: Areolar connective tissue, asoft packaging tissue of the body (300x).

Epithelium

Laminapropria

Fibroblastnuclei

Elasticfibers

Collagenfibers

Figure 4.8a


(b) Connective tissue proper: loose connective tissue, adipose

Description: Matrix as in areolar,but very sparse; closely packedadipocytes, or fat cells, havenucleus pushed to the side by largefat droplet.

Function: Provides reserve foodfuel; insulates against heat loss;supports and protects organs.

Location: Under skin in thehypodermis; around kidneys andeyeballs; within abdomen; in breasts.

Photomicrograph: Adipose tissue from thesubcutaneous layer under the skin (350x).

Nucleus offat cell

Vacuolecontainingfat droplet

Adiposetissue

Mammaryglands


(c) Connective tissue proper: loose connective tissue, reticular

Description: Network of reticularfibers in a typical loose groundsubstance; reticular cells lie on thenetwork.

Function: Fibers form a soft internalskeleton (stroma) that supports othercell types including white blood cells,mast cells, and macrophages.

Location: Lymphoid organs (lymphnodes, bone marrow, and spleen).

Photomicrograph: Dark-staining network of reticularconnective tissue fibers forming the internal skeletonof the spleen (350x).

Spleen

White bloodcell(lymphocyte)

Reticularfibers

Copyright © 2010 Pearson Education, Inc. Figure 4.8d

(d) Connective tissue proper: dense connective tissue, dense regular

Description: Primarily parallelcollagen fibers; a few elastic fibers;major cell type is the fibroblast.

Function: Attaches muscles tobones or to muscles; attaches bonesto bones; withstands great tensilestress when pulling force is appliedin one direction.

Location: Tendons, mostligaments, aponeuroses.

Photomicrograph: Dense regular connectivetissue from a tendon (500x).

Shoulderjoint

Ligament

Tendon

Collagenfibers

Nuclei offibroblasts

Copyright © 2010 Pearson Education, Inc. Figure 4.8e

(e) Connective tissue proper: dense connective tissue, dense irregular

Description: Primarilyirregularly arranged collagenfibers; some elastic fibers;major cell type is the fibroblast.

Function: Able to withstandtension exerted in manydirections; provides structuralstrength.

Location: Fibrous capsules oforgans and of joints; dermis ofthe skin; submucosa ofdigestive tract.

Photomicrograph: Dense irregularconnective tissue from the dermis of theskin (400x).

Collagenfibers

Nuclei offibroblasts

Fibrousjointcapsule

Copyright © 2010 Pearson Education, Inc. Figure 4.8f

(f) Connective tissue proper: dense connective tissue, elastic

Description: Dense regularconnective tissue containing a highproportion of elastic fibers.

Function: Allows recoil of tissuefollowing stretching; maintainspulsatile flow of blood througharteries; aids passive recoil of lungsfollowing inspiration.

Location: Walls of large arteries;within certain ligaments associatedwith the vertebral column; within thewalls of the bronchial tubes.

Elastic fibers

Aorta

HeartPhotomicrograph: Elastic connective tissue inthe wall of the aorta (250x).


Connective Tissue: Cartilage

• Three types of cartilage:

• Hyaline cartilage

• Elastic cartilage

• Fibrocartilage

Copyright © 2010 Pearson Education, Inc. Figure 4.8g

(g) Cartilage: hyaline

Description: Amorphous but firmmatrix; collagen fibers form animperceptible network; chondroblastsproduce the matrix and when mature(chondrocytes) lie in lacunae.

Function: Supports and reinforces;has resilient cushioning properties;resists compressive stress.

Location: Forms most of theembryonic skeleton; covers the endsof long bones in joint cavities; formscostal cartilages of the ribs; cartilagesof the nose, trachea, and larynx.

Photomicrograph: Hyaline cartilage from thetrachea (750x).

Costalcartilages

Chondrocytein lacuna

Matrix

Copyright © 2010 Pearson Education, Inc. Figure 4.8h

(h) Cartilage: elastic

Description: Similar to hyalinecartilage, but more elastic fibersin matrix.

Function: Maintains the shapeof a structure while allowinggreat flexibility.

Location: Supports the externalear (pinna); epiglottis.

Photomicrograph: Elastic cartilage fromthe human ear pinna; forms the flexibleskeleton of the ear (800x).

Chondrocytein lacuna

Matrix

Copyright © 2010 Pearson Education, Inc. Figure 4.8i

(i) Cartilage: fibrocartilage

Description: Matrix similar tobut less firm than that in hyalinecartilage; thick collagen fiberspredominate.

Function: Tensile strengthwith the ability to absorbcompressive shock.

Location: Intervertebral discs;pubic symphysis; discs of kneejoint.

Photomicrograph: Fibrocartilage of anintervertebral disc (125x). Special stainingproduced the blue color seen.

Intervertebraldiscs

Chondrocytesin lacunae

Collagenfiber

Copyright © 2010 Pearson Education, Inc. Figure 4.8j

(j) Others: bone (osseous tissue)

Description: Hard, calcifiedmatrix containing many collagenfibers; osteocytes lie in lacunae.Very well vascularized.

Function: Bone supports andprotects (by enclosing);provides levers for the musclesto act on; stores calcium andother minerals and fat; marrowinside bones is the site for bloodcell formation (hematopoiesis).Location: Bones

Photomicrograph: Cross-sectional viewof bone (125x).

Lacunae

Lamella

Centralcanal

Copyright © 2010 Pearson Education, Inc. Figure 4.8k

(k) Others: blood

Description: Red and whiteblood cells in a fluid matrix(plasma).

Function: Transport ofrespiratory gases, nutrients,wastes, and other substances.

Location: Contained withinblood vessels.

Photomicrograph: Smear of human blood (1860x); twowhite blood cells (neutrophil in upper left and lymphocytein lower right) are seen surrounded by red blood cells.

Neutrophil

Red bloodcells

Lymphocyte

Plasma


Nervous Tissue

• Nervous system (more detail with the Nervous System)


Photomicrograph: Neurons (350x)

Function: Transmit electricalsignals from sensory receptorsand to effectors (muscles andglands) which control their activity.

Location: Brain, spinalcord, and nerves.

Description: Neurons arebranching cells; cell processesthat may be quite long extend fromthe nucleus-containing cell body;also contributing to nervous tissueare nonirritable supporting cells(not illustrated).

Dendrites

Neuron processes Cell body

Axon

Nuclei ofsupportingcells

Cell bodyof a neuron

Neuronprocesses

Nervous tissue


Muscle Tissue

• Skeletal muscle (more detail with the Muscular System)


(a) Skeletal muscle

Description: Long, cylindrical,multinucleate cells; obviousstriations.

Function: Voluntary movement;locomotion; manipulation of theenvironment; facial expression;voluntary control.

Location: In skeletal musclesattached to bones oroccasionally to skin.

Photomicrograph: Skeletal muscle (approx. 460x).Notice the obvious banding pattern and thefact that these large cells are multinucleate.

Nuclei

Striations

Part ofmuscle fiber (cell)


Muscle Tissue

• Cardiac muscle (more detail with the Cardiovascular System)


(b) Cardiac muscle

Description: Branching, striated, generally uninucleate cells that interdigitate atspecialized junctions (intercalated discs).

Function: As it contracts, it propels blood into the circulation; involuntary control.Location: The walls of the heart.

Photomicrograph: Cardiac muscle (500X);notice the striations, branching of cells, andthe intercalated discs.

Intercalateddiscs

Striations

Nucleus


Muscle Tissue

• Smooth muscle


(c) Smooth muscle

Description: Spindle-shapedcells with central nuclei; nostriations; cells arranged closely to form sheets.

Function: Propels substancesor objects (foodstuffs, urine,a baby) along internal passage-ways; involuntary control.Location: Mostly in the wallsof hollow organs.

Photomicrograph: Sheet of smooth muscle (200x).

Smoothmusclecell

Nuclei

Cell and tissues

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