Unit 2: Cells and Tissues p.55-73

Part I: CELLS

Overview of the Cellular Basis of Life1. Four major elements: Carbon, Hydrogen, Oxygen and Nitrogen

a. Build most of the cell’s structure (mostly protein)2. Trace elements: necessary in smaller amounts

a. Important for certain cell functionsi. Ca: blood clotting (and other things)

ii. Fe: manufacturing hemoglobiniii. I: manufacturing thyroid hormoneiv. Electrolytes: Metals (Ca, Na, K) can carry on an electrical

charge; essential for nerve impulses and muscle contraction3. Water:

a. Cells about 60% waterb. Interstitial fluid: solution that surrounds cells in body—dilute salt

wateri. All exchanges between cells and blood

4. Cells vary in size and structure5. Cells vary in function

Anatomy of a Generalized Cell

1. Plasma Membranea. Mostly phospholipids: hydrophobic regions impermeable to most

water soluble moleculesb. Cholesterol c. Proteins: responsible for specialized functions

i. Enzymesii. Integral Proteins: extend through the lipid bilayer

1. Transport (channels, pumps)2. Receptors (binding sites) for hormones etc3. Carriers (bind to a substance and move it through the

membrane)iii. Peripheral Proteins: loosely attached to the exterior or

interior surface of the membrane1. Glycoproteins/glycolipids (Cell identity markers:

determine blood type, receptors for bacteria/viruses, cell-to-cell interactions, role in cancer cells development)

1. What molecules make up the plasma membrane and what are their functions?

2. Compare and contrast peripheral proteins and integral proteins.

d. Specializations of Plasma Membranei. Microvilli: tiny fingerlike projections that increase cell’s

surface area for more absorption (many epithelial cells that line hollow organs—small intestine)

ii. Membrane junctions: most epithelial, some muscle and nerve

Tight junctions: bind cells together, leakproof sheets, prevent substances from passing in between cells; adjacent plasma membranes fuse together

Gap junctions: allow communication between cells, chemicals can pass from one cell to another; connexons: hollow protein cylinders

Desmosomes: anchoring junctions prevent cells from being pulled apart under stress (like skin); thickenings of adjacent plasma membranes, connected by protein filaments (cytoskeleton)

iii. Pseudopods:

2. Organelles (mitochondria, ER, Golgi, lysosomes…)a. Peroxisomes: contain powerful oxidase enzymes that use O2 to

detoxify harmful/poisonous substances (alcohol, formaldehyde…)i. Disarm free radicals: highly reactive chemicals with unpaired

electrons, can scramble protein structures and nucleic acidsii. Convert free radicals to hydrogen peroxide, then broken down

by catalaseiii. Found in liver, kidneyiv. Not derived from Golgi—Replicate by pinching in half

3. Cytoskeleton: network of protein through cytoplasm—internal framework for cell shape, supports for organelles, intracellular transport and other cell movements

Microfilaments: thinnest, actin and myosin, involved in cell motility, change cell’s shape, muscle contractions

Intermediate filaments: ropelike, form desmosomes, resist pulling forces on cell

Microtubules: largest, tube-like; determine overall shape of cell and distribution of organelles; important during cell division

3. What is the importance of cell junctions?4. Compare and contrast lysosomes with peroxisomes.

Cell Diversity: 200 different cell types1. Cells that connect body parts

a. Fibroblast: elongated shape; secretes cable-like fibers; abundant RER and a large Golgi to make and secrete protein building blocks of fibers

b. Erythrocyte (RBC): carries oxygen in bloodstream; concave disk shape for extra surface area flows easily; no other organelles

2. Cells that cover and line body organsa. Epithelial cell: hexagonal shape like honeycomb; cells pack tightly

together; abundant intermediate filaments to resist tearing from rubbing or pulling

3. Cells that move organs and body partsa. Muscle cells: elongated, filled with contractile filaments to shorten;

move bones (skeletal) or change size of internal organs (smooth)4. Cells that store nutrients

a. Fat cells: huge spherical shape; large lipid droplet in cytoplasm5. Cells that fight disease

a. Macrophage: phagocytic, pseudopods (false feet) to crawl through tissue to reach infection sites; contain many lysosomes

6. Cells that gather information and control body functionsa. Nerve cell (neuron): receive and transmit messages; long

“processes,” plentiful RER to make plasma membrane components7. Cells of reproduction

a. Oocyte (female): largest cell in body; much cytoplasm with many copies of organelles

b. Sperm (male): long, streamlined for swimming; flagellum for movement

Cell Physiology10th Grade Biology

Part II: BODY TISSUES

Stem cells for fertilized egg differentiate Division of Labor: highly specialized cells; benefit organism as a whole &

contribute to homeostasis Certain hazards: loss of small group of indispensable cells can

disable/destroy body (ex: heart problem can affect entire organism) Tissue: groups of cells similar in structure and function

o Four primary tissues Epithelium: covers body surfaces; lines body cavities, hollow

organs and ducts (tubes); forms glands Connective: protects and supports the body and its organs,

binds organs together, stores energy reserves as fat, and provides immunity

Muscle: generates the force needed to make body structures move

Nervous: detects changes inside and outside the body, initiates and transmits nerve impulses that coordinate body activities to help maintain homeostasis

Epithelial Tissue Glandular epithelium: forms various glands in body Covering and lining epithelium: covers all free body surfaces and contains

versatile cellso Covers outer layer of skino Line body cavitieso Forms boundaries that separate organism from outside environment:

all substances must pass through epithelium to enter/exit body Functions:

o Protection: skin protects from bacterial/chemical damage, lining of lungs (cilia) sweeps away dust/debris

o Absorption: digestive system organs of stomach and sm intestine absorb food

o Filtration: kidney absorbs and filterso Secretion: glands produce substances in perspiration, oil, digestive

enzymes and mucus1. Special Characteristics of Epithelium

a. Fit closely together: continuous sheetsi. By many cell junctions (desmosomes and tight junctions)

b. Apical surface: one free/unattached surface or edge exposed to body’s exterior or cavity.

i. Exposed surfaces may be slick/smooth or have microvilli or cilia

c. Basement membrane: secreted by lower epithelium cells; surface these cells rest on

d. Avascular: lack blood vessels (nutrients/wastes diffuse between epithelium and connective tissue)

e. Nerve supply presentf. Can regenerate easily when well nourished

2. Classification of EpitheliumTwo names:

First name = relative numbers of layers (simple-one layer; stratified-more than on layer)

Second name = cell shapes squamous-

flattened like fish scales

cuboidal cells-cubed like dice

columnar-tall like columns

a. Simple Epithelia: most concerned with diffusion, osmosis, absorption, secretion and filtration; usually very thin

a. Simple squamous epitheliumi. Description: single layer of thin, flat cells resting on

basement membrane, surface view looks like floor tiles

ii. Function: filtration, diffusion, osmosis and secretion in serous membranes

iii. Location: in areas of little wear and tear; lines heart, blood vessels, lymphatic vessels, air sacs of lungs, Bowman’s capsules of kidneys

1. forms serous membranes (serosae): slick membranes that line and cover organs of ventral body cavity

b. Simple cuboidal epitheliumi. Description: One layer of cuboidal cells on a

basement membraneii. Function: Secretion and absorption

iii. Location: Common in glands and their ducts (salivary glands and pancreas), Forms walls of kidney tubules and covers surface of ovaries

c. Simple columnar epithelium (may be non-ciliated or ciliated)

i. Description: Single layer of tall cells, nucleus at base, either have microvilli or cilia

1. Goblet cells: produce lubricating mucus, may be found in some locations

ii. Function: secretion, absorption; moves mucus and other substances by ciliary action

iii. Location: lines GI tract, ducts of many glands and gallbladder; lines upper respiratory tract, fallopian tubes, uterus, paranasal sinuses, mucosae or mucous membranes

d. Pseudostratified Columnar Epithelium (may be non-ciliated or ciliated)

i. Description: Appears stratified because nuclei of cells are at different levels; all cells attached to basement membrane, but not all reach apical surface

ii. Function: Secretion and movement of mucus by ciliary action

iii. Location: lines airways of most upper respiratory tract, non-ciliated lines larger ducts of many glands, epididymis, part of male urethra

Rare, found mainly in ducts of large glands

b. Stratified Epithelia: consist of two or more cell layers; more durable than simple; concerned with protection of underlying tissues where there wear and tear; some produce secretions named for apical cells

a. Stratified Squamous Epitheliumi. Description: Squamous at surface,

Cuboidal/columnar near basement membrane. Basal cells continually divide, new cells are pushed toward apical surface, become dehydrated, shrunken and harder, apical cells lose cell junctions and get sloughed off

1. Keratinized: tough protein in apical layer and several layers deep, protect skin and underlying tissues from microbes, heat, chemicals

2. Non-Keratinized: no keratin deposited, tissue remains moist

ii. Function: Protectioniii. Location: Found in sites that undergo a lot of friction:

esophagus, mouth, covers tongue, vagina, outer portion of skin,

b. Stratified Cuboidal Epitheliai. Description: Usually 2 layers; apical cells cuboidal

ii. Function: Protective, sometimes secretion/absorption

iii. Location: ducts of adult sweat glands, esophageal glands, male urethra

c. Stratified Columnar Epitheliai. Description: Columnar surface cells, basal cells vary

in size and shapeii. Function: Protection and secretion

iii. Location: large ducts and some glandsc. Transitional Epithelia

a. Modified, Stratified squamous epithelia b. able to slide past one another and change shape to stretchc. forms lining organs in urinary system (urinary bladder,

ureters, part of urethra)

i. subject to considerable stretchingd. basal layer cells are cuboidal or columnare. free surface cells varyf. When not stretched, membrane is many layered, superficial

cells are rounded and domelikeg. When distended with urine, epithelium thins, surface cells

flatten and become squamousliked. Glandular Epithelium

a. Gland: one or more cells that make and secrete a product (secretion)

b. Secretion: contains protein molecules in solutioni. Glandular cells obtain materials from blood to make

secretion which is discharged back into bloodc. Two types of glands:

i. Endocrine glands1. Ductless glands: not connected to surface 2. Hormones (secretions) diffuse directly into

blood vessels surrounding glands3. Thyroid, adrenals, pituitary

ii. Exocrine glands1. Empty secretions through ducts to the

epithelial surface2. Sweat, oil, liver, mammary, salivary, pancreas,

earwax – both internal and external surfaces

5. What characteristics are common to all epithelial tissues?6. Describe the various cell shapes and layering arrangements of

epithelium.7. How is the structure of the each kind of epithelium related to its

function?

Due to lack of blood supply, Heal slowly when injured

Connective Tissue Location: Found everywhere: most abundant and widely distributed Function: Varied; Protect, support, strengthens and bind together other

body tissues; insulates; compartmentalizes structures; transport system (blood); major site of stored energy reserves (adipose); main site of immune responses

Form soft packing tissue around other organs Bear weight, withstand stretching, abrasion etc that other tissues cannot

endure Also able to absorb large amounts of water, may serve as a water reservoir

1. Common Characteristics of Connective Tissuea. Variations in blood supply

i. Vascularized: most have a good blood supply (unlike epithelial tissue)

ii. Tendons, ligaments poor blood supplyiii. Cartilages avascular (no blood supply)

b. Nerve supply present – like epithelial (except cartilage)c. Consists of two basic elements: Cells & Extracellular matrix

1. CELL TYPES OF CONNECTIVE TISSUE Immature forms of cells (names end in –blast) Secrete fibers and ground

substance of the matrix Mature/differentiated cells (names end in –cyte) maintain the matrix

Description Location Functiona. FIBROBLASTS large, flat cells

with branching processes

Found in almost all connective tissues;Migrate through connective tissue

Secrete ground substance and fibers of matrix

b. ADIPOCYTES Red Signet Cells: droplet of triglyceride pushes cytoplasm and nucleus to edges creating ring-like appearance

Found below skin, and around organs (like heart and kidneys)

Stores triglycerides

c. RETICULAR CELLS

Fibroblast appearance, long cellular extensions (processes)

Found in loose connective tissue

d. CHONDROBLASTS, CHONDROCYTES

cartilage

e. OSTEOBLASTS, OSTEOCYTES

bone

f. HEMOCYTOBLASTS

Found in bone marrow

Secretes erythrocytes, leukocytes, platelets

i. Erythrocytes (RBC)s

Red, disk shape, filled with hemoglobin

Cardiovascular system (blood vessels and heart)

Transports oxygen & carbon dioxide to/from body cells

ii. Leukocytes (WBC)s

Irregular shaped

- Macrophages (type of leukocyte)

irregular shape with short branching projections

fixed macrophages: stay in a specific tissue (alveolar macrophages stay in lungs, spleen macrophages stay in spleen)wandering macrophages: gather at site of infection

engulfs bacteria and cellular debris through phagocytosis

- mast cells (type of leukocyte)

found in most tissues, particularly in locations in close contact with external

participates in early recognition of pathogen--Release histamine to stimulate immune response;

environment (skin, airways, intestine)

histamine dilates small blood vessels (part of inflammatory response)

- plasma cells (type of leukocyte)

Produce antibodies

iii. Platelets (formerly called thrombocytes)

Cell fragments Participate in blood clotting

2. EXTRACELLULAR MATRIX Nonliving substance found between cells Produced by connective tissue cells and secreted to exterior Consists of Ground Substance and Protein Fibers

a. GROUND SUBSTANCE Material between cells and fibers Role in how tissues develop, migrate, proliferate and change shape Largely water + adhesion proteins + large polysaccharide molecules

i. Adhesive glycoproteins

Like the glue, allows connective tissue cells to attach to matrix fibers in ground substance (fibronectins, laminins)

ii. Proteoglycans Polysaccharide molecules; Trap water as they intertwineb. PROTEIN FIBERS

Various types and amounts of fibers effect consistency: fluid – gel like – firm – rock like

Description Location Functioni. Collagen fibers Very strong, made

of collagen protein (most abundant protein in body: 25%)

Bone, cartilage, tendons, ligaments

Strength without stiffness, Resist pulling forces

ii. Elastic fibers Thinner than collagen, made of elastin protein surrounded by

Skin, blood vessel walls, lung tissue

Able to stretch 1.5X longer and return to original shape

fibrillin glycoprotein (stabilizer)

iii. Reticular fibers Thinnest, much thinner than collagen, produced by fibroblasts, made of collagen protein and glycoprotein

Walls of blood vessels, around fat cells, nerve fibers and muscle cells

Forms stroma –Supporting framework, helps form basement membrane

2. Types of Connective TissueTissue Cells present Fibers

PresentMatrix Characteristics

Locations; function

Loose Connective TissueFewer fibers, loosely intertwined among many cellsAreolar Tissue Many cells:

fibroblasts, macrophages, plasma, adipocytes, mast cells

Collagen, elastic, & reticular

Soft, pliable, cobwebby; semi-fluid ground substance

found in subcutaneous layer, mucous membranes, around blood vessels, nerves and body organs

Most widely distributed Universal “glue”: holds organs in proper position, Lamina propria: Underlies all mucous membranes Found in subcutaneous layer (attaching skin to underlying tissues and

organs) with adipose tissue Reservoir of water and salts for surrounding tissue Surrounding cells obtain nutrients from, and deposit wastes into Edema (inflammation) occurs when excess fluid is soaked up,

phagocytes search for bacteria, dead cells, toxinsAdipose Tissue adipocytes Reticular,

collagenSmall amount of gelatinous ground

Insulation (reduce heat loss), energy

substance reserve, organ protection (eyeballs, kidneys)

Found with areolar tissue, esp in subcutaneous layer Adipocytes: Signet Ring Cells—triglyceride droplet pushes nucleus and

cytoplasm to edges giving ring-like appearance More adipose tissue forms with weight gain-forming more blood

vessels leading to higher blood pressureReticular Tissue Reticular cells

(resemble fibroblasts)

Reticular fibers

Stroma of some organs (liver, spleen, lymph nodes), portion of red bone marrow that gives rise to blood cells, basement membrane, around blood vessels and muscle

Dense Connective TissueDense Regular Fibroblasts Collagen

fibers, arranged regularly in parallel patterns

Silvery white, tough yet pliable;

Withstands pulling along axis; Tendons and most ligaments

Tendons: attach skeletal muscles to bonesLigaments: connect bones to bones at joints, more stretchy, contain more elastic fibers than tendons

Dense Irregular fibroblasts Collagen fibers, irregularly arranged (in

Occurs in sheets

Pulling forces are exerted in various directions; in dermis (lower

different directions)

layers) of skin, heart valves, perichondrium, periosteum

Elastic connective tissue

fibroblasts Elastic Yellowish, strong, can recoil to original shape after stretching; lung tissue, elastic arteries

CartilageHyaline chondrocytes Collagen

(some elastic)

Limited ground substance; dense, rubbery matrix

Larynx, attaches ribs to breastbone, covers ends of bones to form joints

Fibrocartilage chondrocytes Collagen (some elastic)

Limited ground substance, compressible

Cushion-like disks between vertebrae of spinal column; fetal skeleton

Elastic chondrocytes Elastic (threadlike network)

Limited ground substance, flexible but firm gel matrix; perichondrium present

Strength & elasticity, maintains shape; external ear

Chondrocytes: mature cartilage cellsLacunae: spaces between groups of cellsPerichondrium: membrane of dense irregular connective tissue Chondroitin sulfate: rubbery component of ground substance, provides resilience (able to return to original shape after deformation)

Endure more stress than loose and dense connective tissues Collagen fibers provide strength No blood vessels or nerves

Bone (Osseous Tissue)Compact (dense) Osteoblasts,

osteocytes(Bone cells in Lacunae)

Collagen (lots for strength)

osteons present Hard

Support, protection, generates movement (w/ muscular system); stores calcium and phosphorus; stores red & yellow bone marrow

Spongy (cancellous)

Osteoblasts, osteocytes (Bone cells in Lacunae)

Collagen no osteons, trabeculae present; Hard; red bone marrow (in spaces between lamellae)

Osteoblast: immature bone cell, secretes matrix fibersOsteocyte: mature bone cellOsteon (haversian system) composed of:

Lamellae: rings of matrix (phosphates & calcium) and collagen fibers Lacunae: small spaces between lamellae where osteocytes are found Canaliculi: tiny canals provide routes for nutrients/wastes to/from

osteocytes Central canal: contains blood vessel and nerves

Trabeculae: columns of bone found in spongy bone, (much thinner than osteon, greater space between each trabecula); composed of lamellae, lacunae, canaliculi

Bone is an organ that Includes several tissues: Periosteum: connective tissue that lines bones (except at joints) Red bone marrow: produces RBC, WBC, platelets (red from hemoglobin) Yellow bone marrow: produces fat, cartilage, bone (yellow from

carotenoids in fat) Endosteum: membrane that lines a space within bone, stores yellow

bone marrow

Vascular TissueAtypical connective tissue—transport vehicle for cardiovascular system Blood RBC

(erythrocytes, WBC (leukocytes), platelets

Soluble proteins, form during clotting

Blood plasma: Liquid matrix

Within blood vessels and chambers of heart (cardiovascular system)

Red Blood Cells (erythrocytes): transport oxygen and remove carbon dioxide to/from body cells

White Blood Cells: involved in phagocytosis, immunity and allergic reactions

Platelets: involved in blood clotting Blood plasma: pale yellow fluid, consists mostly of water and dissolved

substances (nutrients, wastes, enzymes, hormones, respiratory gases and ions)

Lymph leukocytes Soluble proteins

Liquid lymph (much less protein than blood plasma)

Flows in lymphatic vessels

Muscle Tissue – muscle fibers Highly specialized to contract:

o produce movemento maintain postureo stabilize jointso produce heat

Muscle Tissue Characteristicso Elongated cells – provide long axis for contractiono Excitability/Irritability: Able to receive and respond to nerve

impulseso Contractility: contracts when sufficient stimulus is receivedo Extensibility: Able to stretch and extendo Elasticity: Returns to relaxed state after stretching

1. Types of Muscle TissueMuscle tissue

Location Cell Structure Control/Function

Other Nerve/Vascular

Skeletal

Attached to Skeleton

Long (up to 30-40 cm), cylindrical, multinucleate, striations

Each muscle organ is packaged by connective tissue sheets

Voluntary (conscious)

Attached to bones/skin to form gross body movements

Form flesh of body

Attached to bones by tendons

Direct contact with motor neurons

Richly vascularized

Smooth

In walls of hollow organs (stomach, bladder, uterus, blood vessels)

Uninucleate No striations

visible Spindle

shaped

Involuntary control

Contractions cause organ constriction or dilation to propel materials through organ

Contractions slower, steady

Peristalsis: Wave-like contractions that move materials

Fatigue resistant action

Autonomic nerve endings on some fibers

Moderately vascularized

Cardiac

Found only in heart

Uninucleate, striations, fibers are

branched intercalated-

disk: where branching cells fit tightly together at junctions

Involuntary control

Contracts to pump/propel blood through blood vessels

Intercalated disks strengthen tissue during contractions, route for electrical signals through heart

8. What is the function of muscular tissue?

9. What are similarities between each muscle tissue? What are the differences?

Nervous Tissue Neurons (nervous cells)

o Irritability and conductivity (major functional characteristics) Receive and convert stimuli into nerve impulses (action

potentials) Conduct electrochemical impulses to other neurons, muscle

fibers or to glandso Unique structure: allows a single neuron to conduct impulses

Cell body: contains nucleus and organelles Dendrites: cell processes highly branched, usually short

(receive) Axon: single, thin, cylindrical and may be very long (conduct)

Neuroglia: o Support, nourish and protect neuronso Maintain homeostasis in interstitial fluid that bathes neuronso Smaller, more numerous than neuronso Do not conduct impulseso Able to divide (multiply to fill in spaces of damaged/injured neurons

Membranes Flat sheets of pliable tissue that cover or line a part of the body

Membrane type

Description Locations Tissues Function of tissues

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Mucous (Mucosa)

Lines body cavity that opens directly to exterior

Lines… Digestive Respiratory Reproductive Much of

Urinary systems

Epithelial tissue

Secretes mucus (maintains moisture in cavities); traps particles; lubricates; absorbs food; secretes digestive enzymes

Connective tissue (underlying)

Bind epithelium to underlying structures; provides epithelium with oxygen and nutrients, removes wastes via blood vessels

Serous Membrane

Lines a cavity that does not open directly to the exterior;

Covers the organs that lie within the cavity;

Consist of 2 layers: Parietal layer -attached to cavity wallVisceral Layer – covers and attaches to organs inside the cavity

Pleura: lines Thoracic cavity and covers lungsPericardium:lines heart cavity and covers heart Peritoneum: lines abdominal cavity and covers abdominal organs

Areolar connective tissue sandwiched between two layers of Mesothelium

-simple squamous epithelium: secretes serous fluid, a watery lubricating fluid, allows organs to slide over each other or against cavity walls

Cutaneous Membrane

Skin: discussed in integumentary system

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Lines the cavities of some joints

Joints of knee, hand, food, wrist, elbow, hip…

Areolar connective tissue with elastic fibers and varying amounts of fat

Secrete synovial fluid: lubricates the ends of bones as they move at joints, nourishes articular cartilage covering the bones

Tissue Repair (Wound Healing) Replaces worn-out, damaged or dead cells1. Injury stimulates inflammatory and immune responses

a. Inflammation: generalized responses to attempt to prevent further injury

b. Immune response: specific, mounts vigorous attack against recognized invader (bacteria, viruses, toxins)

2. Occurs in 2 ways, depending on type of tissue damaged and severity of injury

a. Regenerationi. Replacement of destroyed tissue by same kinds of cells

b. Fibrosisi. Repair by scar tissue (dense (fibrous) connective tissue)

3. Process after injurya. Capillaries become very permeable

i. Allows fluid rich in clotting proteins and other substances to leave bloodstream; enter area of injury

ii. Clotting proteins form clot1. Stops loss of blood2. Holds edges of wound together3. “walls” off injured area, preventing spread of

bacteria/harmful substances to other tissues4. Where exposed to air, forms a scab

b. Granulation tissue formsi. Contains new capillaries that grow into area of injury from

nearby blood vessels1. fragile – bleed freely (when scab picked away)

ii. contains phagocytes 1. to dispose of blood clot and fibroblasts which synthesize

collagen fibers (scar tissue)c. Surface Epithelium regenerates

i. Across granulation tissue just beneath scab1. Scab soon detaches

ii. Results in new epithelium that covers the scar1. Scar may be visible depending on severity of wound

4. Ability of tissue regeneration varies (due to ability to divide)a. Good: Epithelial tissue (skin epidermis, mucous membranes), fibrous

connective tissues, boneb. Poor: skeletal muscle, cartilagec. Mostly scar (if at all): cardiac muscle, nervous tissue

5. New cells come from stroma (supporting connective tissue) during cell division, or from parenchyma (cells of the functioning part of the tissue or organ)Each tissue has a different capacity for replenishing parenchymal cells (sometimes due to blood supply)Tissue Renewability DescriptionEpithelial (skin, mucous membranes)

Continuous In some cases, stem cells divide to replace lost/damaged cells

Connective (fibrous, bone)Muscular Poor

Developmental Aspects of Cells and Tissues1. Humans begin life as a single cell

a. Divides thousands of times to form embryo

Homeostatic imbalance Scar tissue strong, but inflexible Unable to perform functions of original tissue Scar tissue on some organs severely hampers function

b. Specialize to form different tissues2. Cell division: continues until end of puberty (overall growth ends)

a. Divide to replace cells worn away: skin, intestinal, etcb. Divide if cells are damaged or die: liverc. Amitotic (lose ability to divide): heart, nervous

i. Handicapped by injury, replaced by scar tissue which cannot carry out normal function

3. Aging: begins once maturity is reached (some argue begins at birth)a. Causes?

i. Result of “chemical insults” which occur throughout life1. Presence of toxic chemicals (alcohol, drugs, carbon

monoxide)a. Glucose haphazardly added to proteins in/outside

cellsi. Forms crosslinks between proteins,

contributes to stiffening and loss of elasticity in tissues

2. Free radicals: oxidative damage to lipids, proteins or nucleic acids

a. Cause wrinkled skin, stiff joints, hardened arteriesb. Antioxidants: inhibit free radical formation;

vitamin E, vitamin C, betacarotene and selenium3. Absence of needed substances (oxygen)

ii. External physical factors (radiation)iii. Genetic

1. Experiments show many normal cell types have limited capability to divide (then stop)

a. Cessation of mitosis genetically programmed2. Telomeres: specific DNA sequences found at

chromosome tips; protect chromosomes from erosion and sticking to one another

a. become shorter with each cell divisionb. Sometimes disappear altogether with some

functional DNAiv. Autoimmune response: immune system begins to attack own

cells

1. Changes in glycoproteins/glycolipids cause antibodies to attach to and mark the cell for destruction (rheumatoid arthritis?)

b. Effect on tissuesi. Epithelial

1. Thinner2. Easily damaged3. Loses elasticity (sags/wrinkles)4. Exocrine glands less active

a. “Dry out”; produce less oil, less mucus, less sweat5. Endocrine glands less active

a. Produce less hormones, some body processes become less efficient or stop (metabolism/reproduction)

ii. Connective tissues1. Bones become more porous, and weaken

a. Osteoporosisb. longer heal time

2. Muscle and nervous tissue atrophya. Due to decreased efficiency of circulatory system

i. Delivers less oxygen/nutrient to bodyb. May be due to poor diet

4. Other causes of tissue changesa. Neoplasm (new growth): abnormal mass of proliferating cells

(tumor)i. Benign or malignant

b. Hyperplasia: tissues or organs enlarge due to some irritant or condition that stimulates the cells

i. Pregnant woman’s breasts enlarge (normal)ii. Kawasaki disease (enlargement of glands)

c. Atrophy: organ or body area decrease in size due to loss of stimulation

i. Muscles that are not used, or lose nerve supply

Review Questions

Multiple choice1. A (Microvilli)2. A, C, D (skeletal muscle, heart muscle, smooth muscle)3. A, B, C (Determination of blood groups, binding sites of toxins or bacteria,

aiding the binding of sperm to egg)4. E (detoxification activities)5. C (smooth ER)6. C (concentration difference)7. B (simple columnar)8. B (stratified squamous)9. A (Areolar connective)10. A (Dense connective)11. A, B, D, E (Striated, intercalated discs, involuntary, branching)

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