ANATOMY & PHYSIOLOGY UNIT 2 - TISSUES

Unit 2:  Cells and Tissues p.55-73

Part I:  CELLS

Overview of the Cellular Basis of Life

1.    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 functions

                                                    i.     Ca:  blood clotting (and other things)

                                                  ii.     Fe:  manufacturing hemoglobin

                                                iii.     I:  manufacturing thyroid hormone

                                                iv.     Electrolytes:  Metals (Ca, Na, K) can carry on an electrical charge; essential for nerve impulses and muscle contraction

3.    Water:

a.     Cells about 60% water

b.    Interstitial fluid:  solution that surrounds cells in body—dilute salt water

                                                    i.     All exchanges between cells and blood

4.    Cells vary in size and structure

5.    Cells vary in function

Anatomy of a Generalized Cell

1.    Plasma Membrane

a.     Mostly phospholipids:  hydrophobic regions impermeable to most water soluble molecules

b.    Cholesterol

c.     Proteins:  responsible for specialized functions

                                                   i.     Enzymes

                                                  ii.     Integral Proteins:  extend through the lipid bilayer

1.    Transport (channels, pumps)

2.    Receptors (binding sites) for hormones etc

3.    Carriers (bind to a substance and move it through the membrane)

                                                iii.     Peripheral Proteins:  loosely attached to the exterior or interior surface of the membrane

1.    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 Membrane

                                                    i.     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

                                                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 acids

                                                  ii.     Convert free radicals to hydrogen peroxide, then broken down by catalase

                                                iii.     Found in liver, kidney

                                                iv.     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

3.    What is the importance of cell junctions?

4.    Compare and contrast lysosomes with peroxisomes.

Cell Diversity:  200 different cell types

1.    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 organs

a.     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 parts

a.     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 cytoplasm

5.    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 functions

a.     Nerve cell (neuron):  receive and transmit messages; long “processes,” plentiful RER to make plasma membrane components

7.    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 Physiology

            10^th 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 cells

o   Covers outer layer of skin

o   Line body cavities

o   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 filters

o   Secretion:  glands produce substances in perspiration, oil, digestive enzymes and mucus

1.    Special Characteristics of Epithelium

a.     Fit closely together:  continuous sheets

                                                    i.     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 present

f.      Can regenerate easily when well nourished

2.    Classification of Epithelium

Two names: 

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

a.     Simple squamous epithelium

                                                                                  i.     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 epitheliumn

                                                                                  i.     Description:  One layer of cuboidal cells on a basement membrane

                                                                                ii.     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

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 Epithelium

                                                                                  i.     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:  Protection

                                                                              iii.     Location:  Found in sites that undergo a lot of friction:  esophagus, mouth, covers tongue, vagina, outer portion of skin,

b.    Stratified Cuboidal Epithelia

                                                                                  i.     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 Epithelia

                                                                                  i.     Description:  Columnar surface cells, basal cells vary in size and shape

                                                                                ii.     Function:  Protection and secretion

                                                                              iii.     Location:  large ducts and some glands

c.     Transitional Epithelia

a.     Modified, Stratified squamous epithelia

b.    able to slide past one another and change shape to stretch

c.     forms lining organs in urinary system (urinary bladder, ureters, part of urethra)

                                                                                  i.     subject to considerable stretching

d.    basal layer cells are cuboidal or columnar

e.    free surface cells vary

f.      When not stretched, membrane is many layered, superficial cells are rounded and domelike

g.     When distended with urine, epithelium thins, surface cells flatten and become squamouslike

d.    Glandular Epithelium

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

b.    Secretion:  contains protein molecules in solution

                                                                                  i.     Glandular cells obtain materials from blood to make secretion which is discharged back into blood

c.     Two types of glands:

                                                                                 i.     Endocrine glands

1.    Ductless glands:  not connected to surface

2.    Hormones (secretions) diffuse directly into blood vessels surrounding glands

3.    Thyroid, adrenals, pituitary

                                                                               ii.     Exocrine glands

1.    Empty secretions through ducts to the epithelial surface

2.    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? 

8.    Compare the size of the cells found in the basal layer with those of the apical layer.

9.    Explain why cell proliferation occurs near the basal layer, and not the apical layer.

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 Tissue

a.    Variations in blood supply

                                                    i.    

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

                                                  ii.     Tendons, ligaments poor blood supply

                                                iii.     Cartilages avascular (no blood supply)

b.    Nerve supply present – like epithelial (except cartilage)

c.     Consists of two basic elements:  Cells & Extracellular matrix

2.    Types of Connective Tissue

Muscle Tissue – muscle fibers

·       Highly specialized to contract: 

o   produce movement

o   maintain posture

o   stabilize joints

o   produce heat

·       Muscle Tissue Characteristics

o   Elongated cells – provide long axis for contraction

o   Excitability/Irritability:  Able to receive and respond to nerve impulses

o   Contractility:  contracts when sufficient stimulus is received

o   Extensibility:  Able to stretch and extend

o   Elasticity:  Returns to relaxed state after stretching

1.    Types of Muscle Tissue

10.What is the function of muscular tissue?

11.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 glands

o   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 neurons

o   Maintain homeostasis in interstitial fluid that bathes neurons

o   Smaller, more numerous than neurons

o   Do not conduct impulses

o   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

Tissue Repair (Wound Healing)

·       Replaces worn-out, damaged or dead cells

1.    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.     Regeneration

                                                    i.     Replacement of destroyed tissue by same kinds of cells

b.    Fibrosis

                                                    i.     Repair by scar tissue (dense (fibrous) connective tissue)

3.    Process after injury

a.     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 clot

1.    Stops loss of blood

2.    Holds edges of wound together

3.    “walls” off injured area, preventing spread of bacteria/harmful substances to other tissues

4.    Where exposed to air, forms a scab

b.    Granulation tissue forms

                                                    i.     Contains new capillaries that grow into area of injury from nearby blood vessels

1.    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 scab

1.    Scab soon detaches

                                                  ii.     Results in new epithelium that covers the scar

1.    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, bone

b.    Poor:  skeletal muscle, cartilage

c.     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)

Developmental Aspects of Cells and Tissues

1.    Humans begin life as a single cell

a.     Divides thousands of times to form embryo

b.    Specialize to form different tissues

2.    Cell division: continues until end of puberty (overall growth ends)

a.     Divide to replace cells worn away:  skin, intestinal, etc

b.    Divide if cells are damaged or die:  liver

c.     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 life

1.    Presence of toxic chemicals (alcohol, drugs, carbon monoxide)

a.     Glucose haphazardly added to proteins in/outside cells

                                                                                                                i.     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 arteries

b.    Antioxidants:  inhibit free radical formation; vitamin E, vitamin C, betacarotene and selenium

3.    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 programmed

2.    Telomeres:  specific DNA sequences found at  chromosome tips; protect chromosomes from erosion and sticking to one another

a.     become shorter with each cell division

b.    Sometimes disappear altogether with some functional DNA

                                                iv.     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 tissues

                                                    i.     Epithelial

1.    Thinner

2.    Easily damaged

3.    Loses elasticity (sags/wrinkles)

4.    Exocrine glands less active         

a.     “Dry out”; produce less oil, less mucus, less sweat

5.    Endocrine glands less active

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

                                                  ii.     Connective tissues

1.    Bones become more porous, and weaken

a.     Osteoporosis

b.    longer heal time

2.    Muscle and nervous tissue atrophy

a.     Due to decreased efficiency of circulatory system

                                                                                                                i.     Delivers less oxygen/nutrient to body

b.    May be due to poor diet

4.    Other causes of tissue changes

a.     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 choice

1.    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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