Unit 1 Tissue Level of Organisation
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Transcript of 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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