Chapter 4: Tissue The Fabric of Life. Tissue Group of cells – similar in structure and perform a common function 4 Basic Types – 1.Epithelial – covering

Chapter 4: TissueThe Fabric of Life

Tissue

• Group of cells – similar in structure and perform a common function

• 4 Basic Types – 1. Epithelial – covering2. Connective – support3. Muscle - movement4. Nervous - control

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

Histology

• Study of tissues• Preparing tissue:• Specimen –

1. Must be fixed (preserved)2. Cut into sections (slices)3. Stained – enhance contrast

• Artifacts – minor distortions – tissue on slides, not exactly like living tissue

Epithelial Tissue

• Epithelium• Sheet of cells that cover a body surface or lines a body

cavity• 2 main types:

1. Covering and lining2. Glandular epithelium

• Boundaries between different environments1. Protection2. Absorption3. Filtration4. Excretion5. Secretion6. Sensory reception

Epithelial Tissue

• Special Characteristics1. Polarity – - Apical surface – upper free surface exposed to body

exterior- Basal surface – lower attached surface- Apical – basal polarity - Apical Surfaces: Microvilli- fingerlike extensions of

plasma membrane or Cilia – tiny hair like projections- Basal lamina – supporting sheet – adhesive sheet

Epithelial Tissue

2. Specialized Contacts – adjacent cells bound together by tight junctions and desomosomes

Epithelial Tissue

3. Supported by Connective Tissue- Reticular lamina – layer of extracellular

material - Collagen protein fibers- Basement membrane

Epithelial Tissue

4. Avascular but Innervated – - Innervated – supported by nerve fibers- Avascular – no blood vessels- Nourished by nutrients diffusing from blood

vessels in underlying connective tissue5. Regeneration – reproduces rapidly when

damaged

Epithelial Tissue

• Classification – based on number of layers and type of cell

• 2 names– 1st – number of cell layers present– 2nd – shape of cell

• Simple epithelia – single cell layer• Stratified epithelium – 2 or more cell layers

Stratified

Simple

(a) Classification based on number of cell layers.

Cell Shape

• Squamous cells – flattened and scale like• Cubodial cells – boxlike, ~as tall as they are

wide• Columnar cells – tall and column shaped

Squamous

Cuboidal

Columnar(b) Classification based on cell shape.

Epithelial Tissue

• Simple Epithelia – • Simple – single cell layer• Most concerned with absorption, secretion,

and filtration• Very thin

Epithelial Tissue- Simple

• Simple Squamous Epithelium -• Simple – one cell layer• Flattened laterally• Cytoplasm sparse• Thin, permeable• Found everywhere• Filtration or exchange by rapid diffusion• Ex. Endothelium – slick, friction reducing lining of lymphatic

vessels and blood vessels• Mesothelium – epithelium of serous membrane linign ventral

body cavity and organs

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

Epithelial Tissue - Simple

• Simple Cubodial Epithelium – • Single layer of cube-like cells • Secretion and absorption• Found in walls of smallest ducts and glands

Figure 4.3b

(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


• Simple Columnar Epithelium – • Single layer of tall, closely packed cells aligned

in a row• Lines digestive tract• Absorption and secretion• Modifications in digestive tract

1. Dense microvilli on apical surface of absorptive cells

2. Cells secrete protective mucus

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


• Pseudostratified Columnar Epithelium – • Vary in height• False – pseudo – impression of many cell

layers• Absorbs or secretes substances• Ciliated version lines respiratory tract

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

Epithelial Tissue - Stratified

• Stratified Epithelium – • 2 or more cell layers• Regenerate from below• More durable the simple• Protection – major role


• Stratified Squamous Epithelium – • Several layers• Areas of wear and tare• Cell surface – epidermis – keratinized – cell

surface contains keratin – protective protein

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


• Stratified Cubodial epithelium• Rare• Found in ducts of larger glands: sweat,

mammary• 2 layers of cubodial cells


• Stratified columnar Epithelium – • Small amounts in pharynx, male urethra, and

lining some glandular ducts• Only apical layers of cells is columnar

Epithelial Tissue

• Transitional – • Forms lining of hallow urinary organs which

stretch• Basal layer – cubodial or columnar• Apical – vary in appearance• Ability to change shape• Allows bladder to stretch

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

Epithelial Tissue

• Glandular Epithelium – • Gland – one or more cells that make and secrete (export) a

particular product• Secretion – the product, aqueous 9water-based) fluid that

usually contains proteins, but there is some variation• Active process• Classified as –

– Endocrine – internally secreting– Exocrine – externally secreting– Unicellular – one celled– Multicellular – many cells

Glandular Epithelium

• Endocrine Glands – • Eventually loose their ducts• Ductless glands• Produce hormones – regulatory chemicals• Secrete – exocytosis – directly into

extracellular space• Enter blood or lymph • Travel to target organs


• Exocrine Gland – • Secrete products onto body surfaces (skin) or

into body cavities• Unicellular – exocytosis• Multicellular – epithelium, walled ducts• Include mucus, sweat, etc.


• Unicellular Exocrine Glands –• Mucus cells and goblet cells• Sprinkled in epithelial linings of intestinal and

respiratory tracts• Humans – all produce mucin – glycoprotein that

dissolves in water when secreted , once dissolved forms mucus

• Called goblet cells – b/c accumulation of mucus distends the top of the cell

• Distortion does not occur in mucosal cells

Figure 4.4

(b)(a)

Microvilli

Secretoryvesiclescontainingmucin

Golgiapparatus

Rough ER

Nucleus


• Multicellular Exocrine Glands – • 2 parts – duct and secretory unit (acinus)• Supportive connective tissue surrounds

secretory unit and supplies it with blood vessels

Multicellular Exocrine Glands• Structural Classification – • Simple glands – unbranched duct• Compound glands – branched duct• Secretory units –

1. Tubular – secretory cells form tubes2. Alveolar – small, flask like sacs3. Tubular alveolar - both

• Modes of secretion –1. Merocrine glands – secrete products by exocytosis as they

are produced– Ex. Sweat glands

2. Holorcrine glands – accumulate products within them until the rupture

– Cells – die for their cause– Sebaceous (oil) glands of skin

• Apocrine gland – present in other animals – Controversy – as to if in humans

Figure 4.5

Compound duct structure(duct branches)

Simple tubular

ExampleIntestinal glands

Simple branchedtubular

ExampleStomach (gastric)glands

Compound tubular

ExampleDuodenal glands of small intestine

Compound alveolar

ExampleMammary glands

Simplealveolar

ExampleNo importantexample in humans

Simple branchedalveolar

ExampleSebaceous (oil)glands

Compoundtubuloalveolar

ExampleSalivary glands

Tubularsecretorystructure

Alveolarsecretorystructure

Surface epithelium Duct Secretory epithelium

Simple duct structure(duct does not branch)

Connective Tissue• Found everywhere in body• Most abundant• Widely distributed in primary tissues• 4 main classes

1. Connective tissue proper – fat and fibrous tissue of ligaments2. Cartilage3. Bone tissue4. Blood

• Major functions1. Binding and support2. Protection3. Insulation4. Transportation (blood)

Table 4.1

Connective Tissue

• Common Characteristics – 1. Common origin – all arise from mesenchyme (embryonic

tissue)2. Degrees of Vascularity –

- Cartilage – avascular- Dense – poorly vascularized- Others – highly vascularized

3. Extracellular Matrix – - Nonliving extracellular matrix- Able to bear weight- Withstand great tension- Endure abuses – physical trauma and abrasion

Connective Tissue

• Structural Elements – • 3 main – ground substance, fiber, and cells• Extracellular matrix – ground substance +

fibers

Connective Tissue – Structural Elements

• Ground Substances – • Unstructured material that fill space between cells• Contain fibers• Composed of:

– Interstitial (tissue) fluid– Cell adhesion proteins– proteoglycans

• Cell adhesion proteins – fibronectin, laminin, and others• Connective tissue “glue”• Proteoglycans – protein core with glycoaminoglycans (GAGs) attached• Form gel-like matrix

– Interstitial (tissue) fluid– Cell adhesion proteins– proteoglycans


• Fibers – provide support1. Collagen fibers – fibrous protein collagen

molecules secreted into space- assemble cross linking

- Cross linking – tough and provide tensile strength

- White appearance – also called white fibers


2. Elastic fibers – long, thin form branching networks

- Contain elastin-allows stretch and recoil- Skin, lungs, blood vessel walls- Yellow appearance – yellow fibers


3. Reticular fibers – short, fine collagenous fibers

- Continuous with collagen fibers, branch extensively

- Form delicate networks- “fuzzy” nets- Allow give

Connective Tissue – Cells

• Primary cell types – 1. Connective tissue proper – fibroblast2. Cartilage – chondroblast3. Bone – osteoblast

- Hematopoietic stem cell – undifferentiated cell – produces blood cells

- Home to other cell types –1. Fat cells – store nutrients2. Mobile cells – WBCs –neutrophils, esinophils, lymphocytes3. Mast cells – cluster among blood vessels – detect foreign

organisms4. Macrophages – phagotiyze board variety of foreign materials

Types of Connective Tissue

• All arise from a common embryonic line – mesenchyme derived from embryonic mesoderm

• Connective tissue proper – Loose connective tissue

• 2 subclasses: – loose connective tissue

• Areolar, Adipose, Reticular

– Dense connective tissue• Dense regular, dense irregular, elastic

Loose Connective Tissue

1. Areolar Connective Tissue – - Functions;

- Support and binding to other structures- Holding body fluids- Defending against infection- Storing nutrients as fat

- Loose arrangement of tissue- Loose nature – reservoir for water and salts for

surrounding body tissues- Hold approximately as much as entire blood stream

1. Areolar Connective Tissue

• High content of hyaluronic acid - makes it very viscous

• WBC – secrete hyaluronidase – to liquefy ground substances so they can maneuver

• Edema – in a body region, inflamed, soaks up excess fluid, swells and puffy

• Most widely distributed• Universal packing tissue

(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

2. Adipose (Fat) Tissue

• Similar to areolar tissue in structure and function, but can store nutrients

• Also called white fat or white adipose fat• Adipocytes – adipose of fat cells• 90 % of tissue mass• Matrix – scanty• Cells packed closely together• Chicken wire appearance• Oil droplet occupies most of cells volume, displaces nucleus

to one side• Richly vascularized, high metabolic activity


• With out fat stores body can not survive for more than a few days without eating

• 18 % of average person’s body weight• Chubby – 50 % fat without being considered obese• Can develop anywhere, usually accumulates in

subcutaneous tissue – acts as a shock absorber, insulation, and energy storage

• Poor heat conductor – so prevents heat loss from body• Also accumulates around kidneys, behind eyeballs,

abdomen and hips


• Brown fat – brown adipose tissue• Abundant mitochondria• Which use lipid fuels to heat bloodstream to

warm body rather than produce ATP• Richly vascularized – only occurs in babies who

lack the ability to produce body heat by shivering

Figure 4.8b

(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

3. Reticular Connective Tissue

• Resembles areolar tissue• Only fibers – reticular fibers• Reticular cells – fibroblasts – scattered• Labyrinth – like stroma or internal framework• Support many free body cells in lymph nodes,

spleen, and bone marrow

Figure 4.8c

(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

Connective Tissue Proper – Dense Connective Tissue

• Also called fibrous connective tissue1. Dense regular connective tissue – • Closely packed bundles of collagen fibers

running in the same direction• Parallel to the direction of pull• White, flexible structures with great resistance

to tension (pulling forces) where tension is exerted in a single direction

• Crowded in – rows of fibroblasts

1. Dense Regular Connective Tissue

• Slightly wavy• Allow tissue to stretch• Once straightened – no further give• Few cells – other than fibroblasts• Poorly vascularized• Forms – Tendons– Fascia – fibrous membranes – wrap around muscles, blood

vessels, and nerves– Ligaments – slightly more stretchy

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

2. Dense Irregular Connective Tissue

• Same structural elements• Bundles of collagen fibers – thicker and arranged

irregularly• Runs in more than one plane• Forms sheets in body areas where tension is exerted in

many directions• Skin – leathery dermis• Fibrous joint capsules• Fibrous coverings that surround organs – kidneys,

bones, cartilages, muscles, and nerves

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

3. Elastic Connective Tissue

• Very elastic • Few ligaments – ligamenta nuchea and flara

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).

Cartilage

• Intermediate between dense connective tissue and bone

• Stands up to both tension and compression• Tough but flexible• Provides rigidity• Lacks nerve fibers• Avascular• Receives nutrients by diffusion from blood vessels

localized in connective tissue membrane (perichondrium)

Cartilage

• Exceptional amount of tissue fluid• Approx. 80 % water• Chondroblasts – predominant cell type• Produce new matrix until skeleton stops

growing at end of adolescence• Chondrocytes – mature cartilage cells• Typically found in small groups with in cavities

- lacunae

3 Varieties of Cartilage

1. Hyaline Cartilage –- Most abundant in body- Matrix – amorphous and glassy- Chondrocytes – 1-10% of cartilage- Firm support with some pliability- Articulate cartilage = ends of bones- Springy pads – absorb compression- Tip of nose- Connect ribs to sternum- Embryonic skeleton until bond formed

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


2. Elastic Cartilage – - Nearly identical to hyaline- More elastic fibers- Strength and exceptional stretch ability

required- “skeletons” of external ear and epiglottis

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


3. Fibrocartilage – - Structural intermediate between hyaline and dense

regular- Rows of chondrocytes – alternated with thick collagen

fibers- Resists tension well- Strong support and ability to withstand heavy pressure- Intervertebral discs- Spongy cartilage of knee

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

Bone

• Osseous tissue• Support and protect body structures • Provide cavities for fat, • Storage and synthesis of blood cells• Similar to cartilage• Added to matrix elements – inorganic calcium

salts

Bone

• Osteoblasts – produce organic portion of bone matrix and bone salts are deposited on and between fibers

• Mature bone cells – osteocytes

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

Blood

• Fluid within blood vessels• Atypical connective tissue• Classified as connective tissue because it

comes from mesenchyme• Blood cells surrounded by nonliving fluid

matrix called blood plasma• RBS or erythrocytes• Scattered WBCs

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

• Brain, spinal cord, and nerves• Regulate and control body function• 2 major cell types – Neurons– Supporting cells

Nervous Tissue

1. Neurons – highly specialized nerve cells- Generate and conduct nerve impulses- Branching cells with cytoplasmic processes- Processes allow cell to:

- Respond to stimuli- Transmit electrical impulses

Nervous Tissue

2. Supporting cells – non-conducting sells that support, insulate, and protect neurons

Figure 4.9

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

• Highly cellular, well vascularized tissues• Muscle cell process – myofilaments – actin

and myosin – bring about movement and contraction

• 3 kinds of cells– Muscle– Cardiac– Skeletal

Muscle Tissue

• Skeletal Muscle – • Forms flesh of body• Contracts – pulls on bones or skin• Muscle cells – muscle fibers – – Long cylindrical cells– striated or branded in appearance– Many nuclei

Figure 4.10a

(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 – • Found in walls of the heart• Contractions propel blood through blood vessels

to all parts of the body• Striated• Generally uninucleate• Branching cells fit tightly together at unique

junctions, intercalated discs• involuntary

Figure 4.10b

(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 –• No visible striations • Spindle shaped with one centrally located

nucleus• Found in walls of hallow organs: digestive and

respiratory tracts, uterus, blood vessels, etc.• Squeezes substances through the organs by

contracting and relaxing• Voluntary – under consious control

Figure 4.10c

(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

Covering and Lining Membrane

• 3 types – – cutaneous– Mucous– Serous

• Continuous multicellular sheets composed of 2 – primary tissues

• epithelium bound to underlying connective tissue

Cutaneous Membranes

• Skin• Organ system consisting of keratinized

stratified squamous epithelium (epidermis)• Attached to a thick layer of dense irregular

connective tissue • Exposed to air• Dry membrane

Figure 4.11a

Cutaneousmembrane(skin)

(a) Cutaneous membrane (the skin)covers the body surface.

Mucous Membrane

• Mucosae• Line body cavities open to the exterior• Digestives, respiratory, and urogenital tracts• Wet ‘moist” membranes bathed by body secretions• Either stratified squamous or simple columnar epithelia• Directly underlined by loose connective tissue – lamina

propria• 3rd deeper layer of smooth muscle• Doesn't always secrete mucus – urinary tract

Figure 4.11b

Mucosa ofnasal cavity

Mucosa oflung bronchi

Mucosa ofmouth

Esophaguslining

(b) Mucous membranes line body cavitiesopen to the exterior.

Serosa Membranes

• Serosae• Moist membranes in ventral body cavity• Consists of simple squamous epithelium (mesothelium)• Resting on a thin layer of loose connective tissue

(areolar)• Thin, clear serosa fluid lubrication• Named according to function

– Pleura – lungs– Pericardium – heart– Peritoneums – abdominopelvic and viscera

Figure 4.11c

Parietalpericardium

Visceralpericardium

(c) Serous membranes line body cavitiesclosed to the exterior.

Parietalperitoneum

Visceralperitoneum

ParietalpleuraVisceralpleura

Tissue Repair

• Inflammatory response – nonspecific• Immune response – specific• Steps

1. Regeneration2. Fibrosis

- Depends on 1. Type of issue injured2. Severity of injury

Tissue Repair

1. Inflammation sets stage- Tissue trauma – injured cells - Macrophages, mast cells, and others –

release inflammatory chemicals- Capillaries dilate and become permeable- Allows WBC to seep into area- Construct clot

Figure 4.12, step 1

Scab

Blood clot inincised wound

Epidermis

Vein

Inflammatorychemicals

Inflammation sets the stage:• Severed blood vessels bleed and inflammatory chemicals are

released.• Local blood vessels become more permeable, allowing white

blood cells, fluid, clotting proteins and other plasma proteinsto seep into the injured area.

• Clotting occurs; surface dries and forms a scab.

Migrating whiteblood cell

Artery

1

Tissue Repair

2. Organization restores blood Suppy – - Organization – blot clot replaced by

granulation tissue – delicate pink tissue- Cappillaries lay down new bed- Granulation tissue scar tissue

Figure 4.12, step 2

Regeneratingepithelium

Area ofgranulationtissueingrowth

FibroblastMacrophage

Organization restores the blood supply:• The clot is replaced by granulation tissue, which restores

the vascular supply.• Fibroblasts produce collagen fibers that bridge the gap.• Macrophages phagocytize cell debris.• Surface epithelial cells multiply and migrate over the

granulation tissue.

2

Tissue Repair

• Regeneration and fibrosis– The scab detaches– Fibrous tissue matures; epithelium thickens and

begins to resemble adjacent tissue– Results in a fully regenerated epithelium with

underlying scar tissue

Figure 4.12, step 3

Regeneratedepithelium

Fibrosedarea

Regeneration and fibrosis effect permanent repair:• The fibrosed area matures and contracts; the epitheliumthickens.• A fully regenerated epithelium with an underlying area ofscar tissue results.

3

Regenerative Capacity• Epithelial• Bond• Areolar connective• Dense irregular• Blood forming

• Smooth muscle• Dense irregular

• Skeletal• Cartilage

• Caridac• Nervous

Developmental Aspects

• Primary germ layers: ectoderm, mesoderm, and endoderm– Formed early in embryonic development– Specialize to form the four primary tissues• Nerve tissue arises from ectoderm• Muscle and connective tissues arise from mesoderm• Epithelial tissues arise from all three germ layers

Figure 4.13

MesodermEndoderm

16-day-old embryo(dorsal surface view)

Epithelium

Nervous tissue(from ectoderm)

Muscle and connectivetissue (mostly frommesoderm)

Ectoderm

Cancer

• Cells fail to follow normal controls of cell division• Multiply excessively• Neoplasm – mass of proliferating cells• Classified as benign ‘kindly” or malignant “bad”• Benign – concentrated – 1 area, grows slowly• Malignant – grows restlessly, become killers• Metastasis – ability to travel to other parts of the

body

Carcinogens

• Cancer causers• Physical factors – radiation, viral infections, chemicals,

etc. – All cause mutations – changes in DNA alter gene expression

• Oncogenes – cancer causing genes• Protooncogenes – benign forms of oncogenes• Fragile sites – when exposed to carcinogens – convert to

oncogenes• Loss of enzymatic controls• Cells become evasive and metastasize

Tumor Suppressor Genes

• Anti-oncogenes• Suppress cancer by inactivating carcinogens• Aid in DNA repair• Enhance immune response• 2 important ones:– p53 – – p16 – cancer results in loss or malfunction of

these 2 genes

Cancer Treatments

Diagnosis – 1. Screening procedures2. Biopsy3. Tests to determine extent of cancer- Designated stage 1- 4- 1 – best probability of cure- 4 – worst probability

New Therapies

• Old – cut, burn, poison• New – – Targeted drugs – interrupt signaling pathway of cancer

growth– Drugs/radiation precisely to cancer sparing normal tissue– Genetically modified immune cells to target cancer cells– Drugs – that target cancer cells biogenetics– Others – starve cancer cells– Also – cancer vaccines

Documents

Chapter 4: Tissue The Fabric of Life. Tissue Group of cells – similar in structure and perform a common function 4 Basic Types – 1.Epithelial – covering