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Chapter 4: The TissueLevel of Organization

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Epithelia - 1 of 4 tissues of the body

Characteristics

1. Cellularity (cell junctions)2. Polarity (apicaland basalsurfaces)

3. Attachment (basal lamina)

4. Avascularity

5. Regeneration (Epithelia are replaced by division ofgerminative cells(stem cells)near basal lamina)

1. Provide physical protection

2. Control permeability

3. Provide sensation

4. Produce specialized secretions (glandular epithelium)

Functions

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Specializations of Epithelial Cells1. Move fluids overthe epithelium (protection)

2. Move fluids throughthe epithelium(permeability)

3. Produce secretions(protection and

messengers)

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Figure 41

Increasing Surface Area

Microvilliincreaseabsorption or secretion

Cilia(ciliated epithelium)

move fluids

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Classes of Epithelia - based on shape and layers

Table 41

Simple epithelium- single layer of cells

Stratified epithelium- several layers of cells

Shapes Squamous epithelia-flat shaped

Cuboidal epithelia - square shaped

Columnar epithelia - tall shaped

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Squamous Epithelia (2) Simple squamous epithelium-absorption & diffusion

Mesothelium- lines body cavities

Endothelium- lines heart and blood vessels

Stratified Squamous Epithelium - protects against attacks

Keratin proteins add strength and water resistance

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Cuboidal Epithelia (2) Simple cuboidal epithelium- secretion & absorption

Kidney tubules

Stratified cuboidal epithelia- sweat and mammary ducts

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Columnar Epithelia (3) Simple columnar

epithelium-

absorption &secretion

Pseudostratifiedcolumnar

epithelium- ciliamovement

Stratified

columnar

epithelium-

protection

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Glandular Epithelia - Endocrine& exocrineglands

Figure 46

Endocrine Glands -

Release hormones

into interstitial

fluid; no ducts

Exocrine Glands -

Produce secretions

onto epithelialsurfaces; through

ducts

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Modes of Secretion Merocrine secretion

Figure 46a

Apocrine secretion

Are produced in Golgi apparatus

Are released by vesicles(exocytosis)

e.g.,sweat glands

Are produced in Golgi apparatusAre released by shedding cytoplas

e.g.,mammary gland

Holocrine secretion Are released by cells bursting, killing

gland cells

Gland cells replaced by stem cells

e.g.,sebaceous gland

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Connective - 2 of 4 tissues of the body

Function1. Connect epithelium to the rest of the body (basal lamina)

2. Provide structure (bone)

3. Store energy (fat)

4. Transport materials (blood)

5. Have no contact with environment

Characteristics

1. Specialized cells

2. Solid extracellular protein fibers

3. Fluid extracellular ground substance

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Classification of Connective Tissues (3) Connective tissue proper: connect and protect

Fluid connective tissues: transport Supportive connective tissues: structural strength

Connective Tissue Proper

Categories Loose connective tissue:

more ground substance,

less fibers e.g.,fat

(adipose tissue)

Dense connective tissue:

more fibers, less ground

substance e.g.,tendons

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Fibers in Connective Tissue Proper Collagen fibers:

most common fibers in CTP, strong and flexible

resists force in 1 direction, e.g.,tendons andligaments

Reticular fibers: network of interwoven fibers (stroma), strong and

flexible resists force in many directions, e.g.,sheaths

around organs Elastic fibers:

contain elastin, return to original length afterstretching

e.g.,elastic ligamentsof vertebrae

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Ground Substance in Connective Tissue

Proper In connective tissue proper and ground

substance:

is clear, colorless, and viscous

fills spaces between cells and slows

pathogens

L C ti Ti

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Loose Connective Tissues The packing materials of the body

3 types in adults: areolar, adipose, reticular

Areolar Tissue - Least specialized, Elastic fibers, Holdsblood vessels and capillary beds (e.g.,under skin(subcutaneous layer))

Adipose Tissue White fat:most common, stores fat, slows heat loss

(insulation)

Brown fat: more vascularized, breaks down fat,produces heat

Reticular Tissue - Supportive fibers (stroma) that support

functional cells, reticular organs: spleen, liver, lymph nodes,

and bone marrow

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Dense Connective Tissues Connective tissues proper, tightly packed with

high numbers of collagen or elastic fibers: dense regular connective tissue

Attachment and stabilization

tendons, ligaments

dense irregular connective tissue

Interwoven networks of collagen fibers

layered in skin, around cartilage, around bones, form

capsules around some organs (e.g.,liver, kidneys)

elastic tissue

made of elastic fibers

elastic ligaments of spinal vertebrae

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Fluid Connective Tissues Fluid connective tissues:

bloodand lymph watery matrix of dissolved proteins

carry specific cell types (formed elements)

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S ti C ti Ti

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Supportive Connective Tissues Support soft tissues and body weight:

cartilage:

gel-type ground substance for shock absorption and protection

bone:

calcified(made rigid by calcium salts, minerals)

for weight support

C til M t i P t l d

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Cartilage MatrixProteoglycans, ground

substance proteins, cells (chondrocytes)

surrounded by lacunae(chambers)

Cartilage Structure

No blood vessels:chondrocytesproduce

antiangiogenesis factor

Perichondrium:outer, fibrous layer (for strength),inner, cellular layer (for growth and maintenance)

T f C til (3)

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Types of Cartilage (3)Hyaline cartilage, Elastic cartilage, Fibrocartilage

Hyaline cartilage: stiff, flexible support

reduces friction between bones

found in synovial joints, rib tips, sternum, and

trachea

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Elastic cartilage:

supportive but

bends easily

found in external

ear and epiglottis

Fibrocartilage Limits movement

Prevents bone-to-bone

contact

Pads knee joints

Found between pubic

bones and

intervertebral discs

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H d ith li l d ti ti bi t

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How do epithelial and connective tissues combine toform 4 types of membranes?

Membranes - are physical barriers that line or

cover portions of the body consisting of anepitheliumand supported by connective

tissues 4 Types of Membranes

1. Mucous

2. Serous

3. Cutaneous

4. Synovial

Mucous membranes (mucosae):

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Mucous membranes(mucosae):

line passageways that have external connections

also in digestive, respiratory, urinary, and

reproductive tracts

Mucous Tissues

Epithelial surfacesmust be moist to reduce

friction, to facilitate absorptionand excretion

Lamina propria is areolar tissue

Serous Membranes

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Serous Membranes Line cavities not open to the outside

Are thin but strong

Have fluid transudateto reduce friction Serous

membranes:

double, have aparietal portion

covering the

cavity and avisceral portion

(serosa) covering

the organs

Pleural membrane lines pleural

cavities covers lungs Peritoneum lines peritoneal

cavity covers abdominal organs

Pericardium lines pericardial

cavity covers heart

Cutaneous membrane:

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Cutaneous membrane:

is skin, surface of the body

thick, waterproof, and dry

S no ial Membranes

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Synovial Membranes Line articulating (moving) joint cavities

Produce synovial fluid(lubricant)

Protect the ends of bones

Lack a true epithelium

What are the structures and functions of the

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What are the structures and functions of thethree types of muscle tissue?

3 Types of Muscle Tissue Skeletal muscle:

large body muscles responsible for movement

Cardiac muscle: found only in the heart

Smooth muscle:

found in walls of hollow, contracting organs (blood

vessels; urinary bladder; respiratory, digestive and

reproductive tracts)

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Classification of Muscle Cells

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Classification of Muscle Cells

Striated(muscle cells with a banded

appearance): or nonstriated(not banded)

Muscle cells can have a single nucleus:

or be multinucleate Muscle cells can be controlled voluntarily

(consciously):

or involuntarily (automatically)

k l l l ll

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Figure 418a

Skeletal muscle cells:

Striated, voluntary, and multinucleated

are long and thin are usually called muscle fibers

do not divide

new fibers are produced by stem cells (satellite

cells)

Cardiac muscle cells:

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Cardiac muscle cells:

are called cardiocytes

form branching networks connected at

intercalated disks

are regulated by pacemaker cells

striated, involuntary, and single nucleus

Smooth muscle cells:

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Smooth muscle cells:

are small and tapered

can divide and regenerate

nonstriated, involuntary, and single nucleus

Wh t i th b i t t d l f

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What is the basic structure and role ofneural tissue?

Neural tissue is concentrated in the centralnervous system:

brain

spinal cord

2 Kinds of Neural Cells1. Neurons:

nerve cells

perform electrical communication

2. Neuroglia:

support cells

repair and supply nutrients to neurons

Cell Parts of a Neuron

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Cell Parts of a Neuron Cell body:

contains the nucleus and nucleolus

Dendrites: short branches extending from the cell body

receive incoming signals Axon(nerve fiber):

long, thin extension of the cell body

carries outgoing electrical signals to their destination

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Neuroglia