unit 1 tissue level of organisation

8/10/2019 Unit 1 Tissue Level of Organisation

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Tissue level of organisation

Dr. S. Francis


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Outline

Histology is the study of tissue.

4 major tissue types

Epithelial

Connective tissue

Muscle tissue

Neural tissue

Examining their function, main

characteristics, the various types, and places

where they are commonly found.


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Tissues

Collection of spec. Cells and extracellular

matrix, that forms a spc. but ltd. range of

functions.


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Epithelial tissue

Covers exposed areas of the body.

Covers outer edges of organs or innerlining of blood vessels or ducts

Lines passageways and chambers.

Forms glands.

They are avascular.

Connective tissue

Fills internal spaces.

Provides structure and support forother tissues.

Transport materials within the body.

Stores NRG.

Muscle tissue

Contracts to perform specific

movements.

In the process of contraction and

movement, they are able to generate

heat.

Most are amitotic

Neural tissue

Carries info. from one region of the

body to another via electricalimpulses.

They are amitotic


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The need for different tissue types, along with

cell differentiation, is the main reason why higher

organisms are unable to regenerate themselves.

Muscle and neural cells are amitotic, and hence

these tissues seldom develop cancer.


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Epitheal

Protective tissues Lining of the epidermis in the skin

Lining of the mouth

Fluid filled cavity

Of the brain, eye or Blood vessels (prevents friction)

Regulate movement of substances

Lining of the intestine Movement of nutrients across its membrane

Lining of the alveoli within the lungs

Diffusion of gases

Capillaries Allows the filtration of blood and nutrients to the tissues/cells.

Glandular cells

Mammary, sweat, salivary glands

Secrete substances (liquids, mucus, hormones or enzymes).


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Provides sensation

Highly innervated though avascular

Touch receptors in the skin, responds to stimulus bystimulating adjacent sensory nerve cells.

Neuroepithelium (epithelium containing sensory nerves),

responds to smell, taste, sight, equilibrium and hearing.


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Cells are tightly bounded

By one or more tight junctions or desmosomes, and

in addition they are bounded to a basal membrane byCell Adhesive Molecules (CAMs)

(CAMs can be visualised as cement holding ceramic tiles to the grounding, while

specialised cell junctions,can be visualised as the grouting holding the tiles together) Polarity

Always have an exposed surface where the plasma

membrane may be specialised

Microvilli (intestine) or ciliated (trachea), keratinised (skin)

Regeneration

Continuously damaged, therefore constantly

regenerated from stem cells within the epithelium.


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Simple

1 layer of cells covering the basal

membrane

Only in protected areas (i.e.passage ways, vessels, chambers,

body cavity.

Allows secretion & absorption

(i.e. it reduces diffusion time, e.g.

reabsorbs H2O in kidney tubules)Stratified

Many layers of cells covering

the basal membrane.

Named by the shape of the cellsin the superficial layer.

Provides protection (found over

areas that endure chem. or

mech. stress, e.g. skin, lining of

the mouth and anus.

Squamous

(plate or scales)

thin and flat

nuclei occupies thickest portion of cell.

Cuboidal

Appears square or hexagon

Nuclei lies near centre of cells.

Columnar

Boxlike, taller and more slender

Nuclei near base.


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Simple Squamous epithelium

In protective regions, allowing absorption

Alveoli of the lung, kidney tubulesSlick surface - reduce friction.

lining of ventral cavities, blood vessels.

Those not linked with the envn. have spec. names

"Meso"thelium (simple squamous epithelial cells in the serous

membrane, lining the ventral body cavities and covering the

organs "middle").

Pleura, peritoneum, pericardium.

"Endo"thelium (simple squamous epithelial cells lining vessels

and hollow organs "inside covering").

lining the heart and the lymph and blood vessels.


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Stratified Squamous epithelium

Most wide spread of stratified epithelium.

Located where chem. or mech. stress and dehydration

is severe.

Superficial cells are normally atrophied (without

nutrients)

Superficial layer of stressed areas are normally

packed with the protein filament keratin (tough and

water resistant).

Nonkeratinised layers provides resistance to abrasion,

but they have to be kept moist.

Oral cavity, pharynx, esophagus, anus, vagina.


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Simple cuboidal epithelial cells

Nucleus are perfectly aligned within the tissue, causing

it to look like a string of beads.

Ltd. protection

Main function is secretion and absorption

Forms ducts of glands in kidney tubules, pancreas, salivary,and thyroid glands.

Stratified Cuboidal epithelial cells

Rare, located along the ducts of large glands sweat and mammary glands.


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Simple columnar epithelium

Assc. with absorption and secretion

E.g. stomach, small intestine, large intestine.

Digestive sys. Has two modifications of these cells

Dense microvilli & goblet cells (secrete mucus - Its

secretion provide protection from chemical stresses).

Stratified columnar epithelium

Relatively rare, provides protection

Occurs at transition areas / junctions b/w 2 other typesof epithelial cells.

Small portion of pharynx, urethra, anus as well as a few

large excretory ducts.


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Transitional epithelium

Appearance changes when stretched

In the urinary sys., when bladder empty cells resemble stratifiedcuboidal or columnar depending on the degree of stretch.

Pseudostratified Columar epithelium

All cells rest on the basal membrane, however cells are ofdifferent height and they appear stratified, as their nuclei lies

at diffn. levels.

They secrete and absorb substances.

A ciliated version containing goblet cells occur in the respiratory tract,

lining the nasal cavity, trachea, bronchi, and a portion of the male

reproductive tract.


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Glandular epithelia Secreting epithelial cell

Make and secrete H2O base fluid, either protein or steroid rich.

Unicellular (scattered w/in the epithelial)

Multicellular (formed from in or evagination of the

epithelial sheet Most have ducts

Internally or externally secreting cells.


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"Endo" crine - "w/in"

Secrete within the interstitial fluid Via exocytosis

Secrete hormones

Regulatory substances

Ductless secretions

Most are multicellular

Not all are epithelial derived.

Part of the epithelial surface

Lining of digestive tract (amine and peptide hormones that regulatedigestion), kidney (erythropoietin) etc.

Separated from the surface

Pancreas (insulin, Glucogan), pituitary (oxytocin), adrenal

(corticosteriods), testes/ ovaries (sex hormones), etc.

"E " i " id "


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"Exo"crine - "outside"

Secretions are onto epithelial surface

On body surface or within body cavity

Secretions usually protective

Sweat, saliva, digestive enzymes)

Unicellular glands

Goblet cells via exocytosis

Mucin w/in columnar epithelial cells of trachea, digestive tract.

Multicellular glands (secreting sheets)

Secrete via ducts

2 main parts Ducts, derived from epithelium

Secretory units consisting of secretory cells

Surrounded by supportive connective tissues; supplies blood

vessels and nerve fibres.

M l i ll l i l d


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Multicellular secreting glands

Describes according to structure

Simple duct structure

Unbranched from the main duct (1 duct)

Cmpd. duct structure

Branched (many ducts, linked to a main duct)

Tubular(Secretory cells forms tubes)Alveolar(small hollow cavity)/ Acinar(berrylike)

(Secretory cells form small flask like sacs).

Tubuloalveolar (Mixed)

Mode of secretion


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"Mero"crine - "part"

- Very common- via exocytosis (cells r not altered, prds. r secreted as they r

manufactured)

- Salivary, most sweat glands, pancreatic glands, mammary glands

"Apo"crine - "off"

- Loss of the apex portion of the cytoplasm and secretion(cells accum. secretion until they break off, then they repair themselves)

Lipid droplets in the mammary glands

"Halo"crine - "entire"

- Cell burst and die (cells accum. secretion until rupture and die)

- highly mitotic cells

- sebaceous glands of skin.


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Secretions may be

Serous

Watery based, with enzymes (parotid salivary gland)

Mucous

Protein mucin which gives mucous when dissolved

in H2O

Mixed

Contains one or more glands and prd. different

secretions

Submandibular salivary gland


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Connective Tissue

Found w/in the body, most abundant and widely

distributed. Bone, blood, adipose tissue

Support the body

protect and interconnect other tissues.

Transport materials

Fluid connective tissues provides means of transport for

dissolved and essential materials

Storage of energy reserves Fats in the adipose tissues store energy

Defense

Responds to microorganisms and prd. antibodies.


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Many are highly vascularised

Contains many receptors

Pain, pressure, temp.

Derived from mesoderm (embryonic) tissue

Share basic characteristics

3 basic components

Protein fibres

Grd. subst.

Specialised cells


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Protein fibres Collagen, reticular, elastic

Collagen Long and straight, adds structure (flexible and strong)

Most common

E.g. tendons have a high constituent of collagen fibres

Reticular (network) Thin, branched fibres (tough but flexible)

Stabilises position of cells, organs blood vessels, nerves etc.

Elastic fibres Contain the protein elastin

Branched, wavy, stretchable and recoils


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Ground substance

Fill the spaces b/w the cells

A/c for cell volume Water based

Blood plasma and interstitial fluid in the lymph

Viscous

Collagen proper (adipose tissue, tendons, ligaments) Its density slows bacterial pathogens

Firm rubbery gel

Cartilage

Calcified Bone

Specialised

cells vary between the types of tissues.

Connective tissue proper


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Connective tissue properMany types of cells and fibres in an syrupy grd. fluid.

The tissue types differ in their proportion of fibres and cells

Loose or Areolar (little space)

(fibres create a loose open framework)

(e.g. Adipose tissue, brown fat; highly vascularised, in infants)

Dense(fibres are densely packed)

(Tendons; connect muscles to bones. Ligaments; connects bones to each other)

Fluid connective tissueMany of the cells and fibres are in a fluid matrix

Blood and lymph

Supporting connective tissueCells and fibres in a rubbery

(Cartilage)

or Calcium grd. Fluid(Bone)


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Connective tissue proper

Cells are involved in

Local maintenance, repair, energy storage

Cell popn

Fibroblast

Prd. Hyaluronan (polysacc) and proteins (fibres)

both forms proteoglycan Macrophages

Microphages (neutrophils and eosinophils)

Adipocytes

Meschymal cells (stem cells for regeneration) Melanocytes

Mast cells

Filled with granules of histamine and heparin

Lymphocytes


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Loose / Areolar connective proper tissues

Packaging materials of the body

Fills spaces b/w organs

Sep. skin from muscles

Provides cushioning

Supports epithelial, blood vessels, nervesStores lipids

Adipose tissue have a higher concnof fat cells

Allows a route for diffusion of materials

Provides nutrients for epithelial cells

Extensive blood supply

(e.g. buttocks, belly, surrounds kidney and bony

sockets of the eye)


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Dense connective tissue

Regular and Irrregular

Dense regular

Contain high % of collagen and elastin arranged

parallel to each other.

E.g. tendons and ligaments

Dense irregular

Collagen and elastin fibres are interwoven

Provide strength, support (e.g. skin) Attachment to other body parts

sheath around cartilages (the perichondrium), sheath around

bones (periosteum), capsule surrounding kindneys, spleen,

encloses cavities of joints.


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Fl id ti ti


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Fluid connective tissue

Blood

Cell popn

Erythrocytes (RBC)

Leukocytes (WBC)

PlateletsLymph

(returns interstitial fluid to the circulatory sys.;

removes dead cells and pathogens)

Cell popn

Leukocytes

Lymphocytes

Supportive connective tissue


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pp

Cartilage

Avascular (nutrients & waste diffuses across matrix

Gel matrix from chondroitin sulphate (polysacc) +

fibreous protein

Cell popn Chondrocytes

Found in small pockets called Lacunae

Prd. a chem. (antiangiogenesis factor) that inhibits vascular growth


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3 types of cartilages

Hyaline (hylos - glass) most common

Numerous loosely packed collagen fibresNasal, b/w rib & sternum, b/w trachea walls, covers bones.

Elastic cartilage

Numerous elastin fibres

Flaps of the ear and epiglottis, middle ear

Fibrocartilage

Little grd. subst, many interwoven collagen fibres

Lies b/w the spinal vertebrates, b/w pubic bone of pelvis,around or within some joints and tendons.

Resist compression

Prevent bone to bone contact.


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B


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Bone

Matrix .Collagen fibres + CaPO4/ CaCO3

Cell popn Osteocytes in lacunae

Cells communicate w/ central blood vessels via

canaliculi (little canals)

Unlike cartilage bone r reparable


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M b


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Membranes

Formed b/w epithelial and connective tissues

Protect and cover other structures 4 types

Mucus, serous, cutaneous, synovial

Mucus membraneLoose connective tissue (Lamina propria ) + simple

epithelium

Lines cavities that commun. w/ exterior

Digestive, respiratory, urinary

Epithelial r kept moist

by mucus prding goblet cells, multicellular glands, urine,

semen.


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Serous membrane

Lines the sealed internal divisions of the ventral

cavity Pleura, pericardium, peritoneum.

Has a parietal & visceral portion

Mesothelium (cavity epithelium) + loose connectivetissue

Cutaneous membrane (skin)

Covers body surface

Water proof and Dry

Stratified squamous epithelial + loose (lamina

propria)& dense (reticular lamina) connective tissue


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M l ti


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Muscle tissue Spec. for contractions

Derived from the mesoderm Cytoplasm differs from reg. cells called

sarcoplasma (made up of actin & myosin proteins)

Plasma mem. called sacrolemma3 types

Skeletal, cardiac, smooth


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Skeletal Muscle

Cells long and slender.called muscle fibres

Fibres are tied together by looses connective tissue

Grp of cells attach to muscle via tendons)

Actin and Myosin arranged in bands.striated

Multinucleated

Amitotic

Depend on myoblast/ myosatellite cells

Voluntary muscles


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Cardiac muscle

Situated only in the heart

Cells appear like skeletal muscles but fibres aresmaller.

Usually uni-nucleated

Cells form extensive connections w/ oneanother..called Intercalated disc

Attached by desmosomes, intercement, gap

junctions (allows ionic movement to twitch)

Amitotic, have no satellite cells Irreparable


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Neural tissue


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Derived from the ectodermal layer

Conduct electrical impulses from one partof the body to the next

amitotic

2 basic types


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2 basic types

Neurons (nerve cells)

Communicate via trans membrane potential

Head region with the nucleus, which sends out dentrites,

dendrites (tree) are contacted by other neurons.

Tail/ axon (nerve fibre), which ends in synaptic terminals,

these attach directly to cells and dendrites, carry info.

Neuroglia (nerve glue - supporting cells)

Provide a supportive framework for neural tissue

Supply nutrients & performs phagocytosis

Maintains physical structure of the tissue

6 cell types (4 CNS & 2 PNS)


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unit 1 tissue level of organisation

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