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Tissues structures and Functions Dr. Amjad El-Shanti 201

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Title: Tissues structures and Functions Dr. Amjad El-Shanti 201


1
Tissues structures and Functions
  • Dr. Amjad El-Shanti
  • 2011

2
Tissues
  • Tissue is a collection of similar cells that
    group together to perform a specialized function.
  • There are 4 primary tissue types in the human
    body
  • Epithelial tissue,
  • Connective tissue,
  • Muscle tissue
  • Nerve tissue.

3
1.Epithelial Tissues
  • Epithelial tissue covers the whole surface of the
    body.
  • It is made up of cells closely packed and ranged
    in one or more layers.
  • This tissue is specialised to form the covering
    or lining of all internal and external body
    surfaces.
  • Epithelial tissue that occurs on surfaces on the
    interior of the body is known as endothelium.
  • Epithelial cells are packed tightly together,
    with almost no intercellular spaces and only a
    small amount of intercellular substance.
  • Epithelial tissue, regardless of the type, is
    usually separated from the underlying tissue by a
    thin sheet of connective tissue basement
    membrane.
  • The basement membrane provides structural support
    for the epithelium and also binds it to
    neighbouring structures.

4
Types of Epithelial Tissue
  • Epithelial tissue can be divided into two groups
    depending on the number of layers of which it is
    composes.
  • Epithelial tissue which is only one cell thick
    is known as simple epithelium.
  • If it is two or more cells thick such as the
    skin, it is known as stratified epithelium.

5
Simple epithelium
  • Simple epithelium can be subdivided according to
    the shape and function of its cells
  • Simple Squamous (pavement) epithelium
  • Simple Cuboidal Epithelium
  • Simple Columnar Epithelium
  • Ciliated Columnar Epithelium
  • Glandular Epithelium
  • Pseudo-stratified columnar epithelium

6
Simple Squamous (pavement) epithelium
  • Squamous cells have the appearance of thin, flat
    plates.
  • The shape of the nucleus usually corresponds to
    the cell form and help to identify the type of
    epithelium.
  • Squamous cells, for example, tend to have
    horizontall flattened, elliptical nuclei because
    of the thin flattened form of the cell.
  • They form the lining of cavities such as the
    mouth, blood vessels, heart and lungs and make up
    the outer layers of the skin.

7
Simple Cuboidal Epithelium
  • As their name implies, cuboidal cells are roughly
    square or cuboidal in shape.
  • Each cell has a spherical nucleus in the centre.
  • Cuboidal epithelium is found in glands and in
    the lining of the kidney tubules as well as in
    the ducts of the glands.
  • They also constitute the germinal epithelium
    which produces the egg cells in the female ovary
    and the sperm cells in the male testes.

8
Simple Columnar Epithelium
  • Columnar epithelial cells occur in one layer.
  • The cells are elongated and column-shaped.
  • The nuclei are elongated and are usually located
    near the base of the cells.
  • Columnar epithelium forms the lining of the
    stomach and intestines.
  • Some columnar cells are specialized for sensory
    reception such as in the nose, ears and the taste
    buds of the tongue.
  • Goblet cells (unicellular glands) are found
    between the columnar epithelial cells of the
    duodenum.
  • They secrete mucus or slime, a lubricating
    substance, which keeps the surface smooth.

9
Ciliated Columnar Epithelium
  • These are simple columnar epithelial cells, but
    in addition, they posses fine hair-like
    outgrowths, cilia on their free surfaces.
  • These cilia are capable of rapid, rhythmic,
    wavelike beatings in a certain direction.
  • This movement of the cilia in a certain direction
    causes the mucus, which is secreted by the goblet
    cells, to move (flow or stream) in that
    direction.
  • Ciliated epithelium is usually found in the air
    passages like the nose.
  • It is also found in the uterus and Fallopian
    tubes of females. The movement of the cilia
    propel the ovum to the uterus.

10
Glandular Epithelium
  • Columnar epithelium with goblet cells is called
    glandular epithelium.
  • Some parts of the glandular epithelium consist of
    such a large number of goblet cells that there
    are only a few normal epithelial cells left.
  • Columnar and cuboidal epithelial cells often
    become specialised as gland cells which are
    capable of synthesising and secreting certain
    substances such as enzymes, hormones, milk,
    mucus, sweat, wax and saliva.
  • Unicellular glands consist of single, isolated
    glandular cells such as the goblet cells.
  • Sometimes a portion of the epithelial tissue
    becomes invaginated and a multicellular gland is
    formed.
  • Multicellular glands are composed of clusters of
    cells.
  • Most glands are multicellular including the
    salivary glands.

11
Pseudo-stratified columnar epithelium
  • appears stratified, typically with nuclei located
    in at least two more-or-less distinct levels.
  •  But in fact every cell rests on the basement
    membrane, so the epithelium is technically
    "simple", in spite of appearances.
  • A pseudo-stratified columnar epithelium is
    characteristic of the respiratory tract and of
    the ducts in the male reproductive system.

12
Stratified Epithelium
  • Stratified epithelium is formed of many layers of
    cells (3 or more layers).
  • Types of stratified epithelium the stratified
    epithelium is named according to the most
    superficial cells
  • Stratified Squamous epithelium
  • Stratified Columnar epithelium
  • Stratified Cuboidal epithelium
  • Transitional epithelium

13
Stratified Squamous epithelium
  • Where body linings have to withstand wear and
    tear, the epithelia are composed of several
    layers of cells and are then called compound or
    stratified epithelium.
  • The top cells are flat and scaly and it may or
    may not be keratinised (i.e. containing a tough,
    resistant protein called keratin).
  • The mammalian skin is an example of dry,
    keratinised, stratified epithelium.
  • The lining of the mouth cavity is an example of
    an unkeratinisied, stratified epithelium.

14
Stratified Squamous epithelium
15
Stratified Columnar epithelium
  • It is rare.
  • It is similar in structure to stratified Squamous
    epithelium.
  • But the layers number is less in number. 
  • The basal layer of cells are cuboidal cells.
  • The layer nearest the apical surface includes
    columnar cells. 
  • The large droplets are mucus, in Goblet cells.
  • One place you can find it is in the largest ducts
    of salivary glands (parotid, submandibular, etc). 

16
Stratified Cuboidal epithelium
  • Sweat gland ducts are examples of stratified
    cuboidal epithelium.
  • usually however there are only two layers of
    cells. 

17
Transitional epithelium
  • It is also called urothelium, is a stratified
    epithelium lining the distensible walls of the
    urinary tract.  
  • The name "transitional" derives from this
    tissue's ability to change its shape from
    cuboidal to squamous when stretched.

18
Functions of Epithelial Tissue
  • Protection
  • Epithelial cells from the skin protect underlying
    tissue from mechanical injury, harmful chemicals,
    invading bacteria and from excessive loss of
    water.
  • Sensation
  • Sensory stimuli penetrate specialised epithelial
    cells. Specialised epithelial tissue containing
    sensory nerve endings is found in the skin, eyes,
    ears, nose and on the tongue.
  • Secretion
  • In glands, epithelial tissue is specialised to
    secrete specific chemical substances such as
    enzymes, hormones and lubricating fluids.

19
  • Absorption
  • Certain epithelial cells lining the small
    intestine absorb nutrients from the digestion of
    food.
  • Excretion
  • Epithelial tissues in the kidney excrete waste
    products from the body and reabsorb needed
    materials from the urine. Sweat is also excreted
    from the body by epithelial cells in the sweat
    glands.
  • Diffusion
  • Simple epithelium promotes the diffusion of
    gases, liquids and nutrients. Because they form
    such a thin lining, they are ideal for the
    diffusion of gases (eg. walls of capillaries and
    lungs).

20
  • Cleaning
  • Ciliated epithelium assists in removing dust
    particles and foreign bodies which have entered
    the air passages.
  • Reduces Friction
  • The smooth, tightly-interlocking, epithelial
    cells that line the entire circulatory system
    reduce friction between the blood and the walls
    of the blood vessels.

21
2.Connective Tissues
  • Connective tissue is one of the four types of
    tissue in traditional classifications (the others
    being epithelial, muscle, and nervous tissue.)
  • It is largely a category of exclusion rather
    than one with a precise definition, but all or
    most tissues in this category are similarly
  • Involved in structure and support.
  • Derived from mesoderm (there are exceptions.(
  • Characterized largely by the traits of non-living
    tissue.
  • Blood, cartilage, and bone are usually considered
    connective tissue, but because they differ so
    substantially from the other tissues in this
    class, the phrase "connective tissue proper" is
    commonly used to exclude those three.

22
2.1.Connective tissue proper
  • A. Areolar or (Loose) connective Tissue holds
    organs and epithelia in place, and has a variety
    of proteinaceous fibres, including collagen and
    elastin. It is also important in inflammation.

23
2.1.Connective tissue proper
  • B. Adipose tissue contains adipocytes, used for
    cushioning, thermal insulation, lubrication
    (primarily in the pericardium) and energy
    storage. (fat(

24
2.1.Connective tissue proper
  • C. Dense connective tissue (or, less commonly,
    fibrous connective tissue) forms ligaments and
    tendons.
  • Its densely packed collagen fibres have great
    tensile strength.

25
2.1.Connective tissue proper
  • D. Reticular connective tissue is a network of
    reticular fibres (fine collagen) that form a soft
    skeleton to support the lymphoid organs (lymph
    nodes, bone marrow, and spleen.(

26
Types of connective tissue fibers
  • released by subunits secreted by fibroblasts
  • Collagen fibers, the most common fibers in
    connective tissue proper, are long, straight, and
    unbranched.
  • Elastic fibers contain the protein elastin and
    are branched and wavy, returning to their
    original length after being stretched.
  • Reticular fibers are the least common of the
    three, thinner than collagen fibers, forming a
    branching, interwoven network in various organs.

27
Connective tissue proper cell types
  • Fibroblasts are the most abundant cells
    responsible for the production and maintenance of
    the connective tissue fibers and the ground
    substance.
  • Macrophages are scattered among the fibers, which
    engulf (phagocytize) pathogens or damaged cells
    encountered in the tissue responsible for
    chemicals released that mobilize the immune
    system into drawing more macrophages into an
    area.
  • Fat cells are also called adipocytes. A fat cell
    contains such a large droplet of lipid that the
    nucleus and other organelles are pushed to one
    side. The number of cells varies from one tissue
    type to another, from one region of the body to
    another, and from one individual to another.
  • Mast cells are mobile connective tissue cells
    often found near blood vessels. The cytoplasm is
    packed with vesicles filled with chemicals that
    are released to start the body's defence system
    when the need arises.
  • Phagocytic and antibody-producing WBCs may move
    throughout the connective tissue increasing their
    numbers during an injury.

28
2.2.Specialized connective tissues
  • Blood - plasma (matrix), RBCs, WBCs, and
    platelets within the blood vessels plasma
    (transports materials), RBCs (carries oxygen),
    WBCs (destroys pathogens), and platelets
    (prevents blood loss)
  • Bone - osteocytes in a matrix of calcium salts
    and collagen bones supports the body,
    protects internal organs from mechanical injury,
    stores excess calcium, and contains and protects
    red bone marrow.
  • Cartilage chondrocytes in a flexible protein
    matrix walls of trachea (keeps airway open), on
    joint surface of bones (smooth to prevent
    friction), on tip of nose and outer ear
    (support), and between the vertebrae (absorbs
    shock)

29
Major types of cartilages
  • Hyaline cartilage is the most common type,
    connecting ribs to the sternum, supporting the
    conducting pathways of the respiratory tract, and
    covering the surfaces of bones within joints.
  • Elastic cartlage contains numerous elastic
    fibers, making it extremely resilient and
    flexible. Elastic cartilage supports the pinna
    (external flap of the ear), the epiglottis, and
    the tip of the nose.
  • Fibrocartilage is dominated by collagen fibers,
    making it extremely durable resisting
    compression, absorbing shocks, and preventing
    damage from bone to bone contact. It also lies
    between the bones of the pelvis and around, or
    within, some joints and tendons. Damaged tissue,
    especially in such joints as the knee, can
    interfere with movement and tends to heal poorly.

30
3. Muscle Tissue
  • Muscle tissue is composed of cells that have the
    special ability to shorten or contract in order
    to produce movement of the body parts.
  • The tissue is highly cellular and is well
    supplied with blood vessels.
  • The cells are long and slender so they are
    sometimes called muscle fibers, and these are
    usually arranged in bundles or layers that are
    surrounded by connective tissue.
  • Actin and myosin are contractile proteins in
    muscle tissue.

31
Muscle Tissue
  • Muscle tissue can be categorized into
  • skeletal muscle tissue
  • smooth muscle tissue
  • cardiac muscle tissue

32
Skeletal Muscle Tissue
  • the triceps muscle, is attached at its Origin to
    a large area of bone in this case, the humerus
  • At its other end, the insertion, it tapers into a
    glistening white tendon, which, in this case, is
    attached to the ulna, one of the bones of the
    lower arm.
  • As the triceps contracts, the insertion is pulled
    toward the origin and the arm is straightened or
    extended at the elbow.
  • Thus the triceps is an extensor. Because
    skeletal muscle exerts force only when it
    contracts, a second muscle a flexor is needed
    to flex or bend the joint. The biceps muscle is
    the flexor of the lower arm. Together, the biceps
    and triceps make up an antagonistic pair of
    muscles.
  • Similar pairs, working antagonistically across
    other joints, provide for almost all the movement
    of the skeleton.

33
Skeletal Muscles
  • Skeletal muscle is made up of thousands of
    cylindrical muscle fibers often running all the
    way from origin to insertion.
  • The fibers are bound together by connective
    tissue through which run blood vessels and
    nerves.

34
Muscle Fibers
  • Each muscle fibers contains
  • an array of myofibrils that are stacked
    lengthwise and run the entire length of the
    fiber.
  • mitochondria
  • an extensive smooth endoplasmic reticulum (SER)
  • many nuclei.
  • The multiple nuclei arise from the fact that each
    muscle fiber develops from the fusion of many
    cells (called myoblasts).

35
Parts of skeletal Muscle Fibers
  • Because a muscle fiber is not a single cell, its
    parts are often given special names such as
  • sarcolemma for plasma membrane
  • sarcoplasmic reticulum for endoplasmic reticulum
  • sarcosome for mitochondrion
  • sarcoplasm for cytoplasm

36
Bands and Zones of Skeletal muscles
  • The striated appearance of the muscle fiber is
    created by a pattern of alternating
  • Dark A bands and
  • Light I bands.
  • The A bands are bisected by the H zone
  • The I bands are bisected by the Z line.

37
Filaments of myofibrils
  • Each myofibril is made up of arrays of parallel
    filaments.
  • The thick filaments have a diameter of about 15
    nm. They are composed of the protein myosin.
  • The thin filaments have a diameter of about 5 nm.
    They are composed chiefly of the protein actin
    along with smaller amounts of two other proteins
  • troponin and
  • tropomyosin.

38
Smooth Muscle Tissue
  • Smooth muscle is made of single, spindle-shaped
    cells.
  • It gets its name because no striations are
    visible in them.
  • Nonetheless, each smooth muscle cell contains
    thick (myosin) and thin (actin) filaments that
    slide against each other to produce contraction
    of the cell.
  • The thick and thin filaments are anchored near
    the plasma membrane (with the help of
    intermediate filaments)).

39
Smooth Muscle stimulation or Inhibition
  • Smooth muscle (like cardiac muscle) does not
    depend on motor neurons to be stimulated.
  • However, motor neurons (of the autonomic system)
    reach smooth muscle and can stimulate it or
    relax it depending on the neurotransmitter they
    release (e.g. noradrenaline or nitric oxide, NO)).

40
Smooth Muscle contraction
  • Smooth muscle can also be made to contract
  • by other substances released in the vicinity
    (paracrine stimulation)
  • Example release of histamine causes contraction
    of the smooth muscle lining our air passages
    (triggering an attack of asthma)
  • by hormones circulating in the blood
  • Example oxytocin reaching the uterus stimulates
    it to contract to begin childbirth.

41
  • Cardiac or heart muscle resembles skeletal muscle
    in some ways it is striated and each cell
    contains sarcomeres with sliding filaments of
    actin and myosin.
  • However, cardiac muscle has a number of unique
    features that reflect its function of pumping
    blood.
  • The myofibrils of each cell (and cardiac muscle
    is made of single cells each with a single
    nucleus) are branched.
  • The branches interlock with those of adjacent
    fibers by adherens junctions. These strong
    junctions enable the heart to contract forcefully
    without ripping the fibers apart.

42
  • The action potential that triggers the heartbeat
    is generated within the heart itself.
  • Motor nerves (of the autonomic nervous system) do
    run to the heart, but their effect is simply to
    modulate increase or decrease the intrinsic
    rate and the strength of the heartbeat.
  • Even if the nerves are destroyed (as they are in
    a transplanted heart), the heart continues to
    beat.
  • Cardiac muscle has a much richer supply of
    mitochondria than skeletal muscle. This reflects
    its greater dependence on cellular respiration
    for ATP.
  • Cardiac muscle has little glycogen and gets
    little benefit from glycolysis when the supply of
    oxygen is limited.
  • Thus anything that interrupts the flow of
    oxygenated blood to the heart leads quickly to
    damage even death of the affected part.

43
4. Nervous tissue
  • Nervous Tissue is found in the brain, spinal
    cord, and nerves.
  • It is responsible for coordinating and
    controlling many body activities.
  • It stimulates muscle contraction, creates an
    awareness of the environment, and plays a major
    role in emotions, memory, and reasoning.
  • To do all these things, cells in nervous tissue
    need to be able to communicate with each other by
    way of electrical nerve impulses.

44
  • The cells in nervous tissue that generate and
    conduct impulses are called neurons or nerve
    cells.
  • These cells have three principal parts
  • the dendrites,
  • the cell body,
  • and one axon.
  • The main part of the cell, the part that carries
    on the general functions, is the cell body.
  • Dendrites are extensions, or processes, of the
    cytoplasm that carry impulses to the cell body.
  • An extension or process called an axon carries
    impulses away from the cell body.

45
Neuron Structure
46
Neuroglia cells
  • Nervous tissue also includes cells that do not
    transmit impulses, but instead support the
    activities of the neurons.
  • These are the glial cells (neuroglial cells),
    together termed the neuroglia.
  • Supporting, or glia, cells bind neurons together
  • and insulate the neurons.
  • Some are phagocytic and protect against
    bacterial invasion,
  • while others provide nutrients by binding blood
    vessels to the neurons. 

47
Classification of Neurons
  • One way to classify neurons is by the number of
    extensions that extend from the neuron's cell
    body (soma)
  • 1.Bipolar neurons have two processes extending
    from the cell body (examples retinal cells,
    olfactory epithelium cells).
  • 2.Pseudounipolar cells (example dorsal root
    ganglion cells). Actually, these cells have two
    axons rather than an axon and dendrite. One axon
    extends centrally toward the spinal cord, the
    other axon extends toward the skin or muscle.
  • 3.Multipolar neurons have many processes that
    extend from the cell body. However, each neuron
    has only one axon (examples spinal motor
    neurons, pyramidal neurons, Purkinje cells).

48
Classification of Neurons
  • Neurons can also be classified by the direction
    that they send information
  • Sensory (or afferent) neurons send information
    from sensory receptors (e.g., in skin, eyes,
    nose, tongue, ears) TOWARD the central nervous
    system.
  • Motor (or efferent) neurons send information
    AWAY from the central nervous system to muscles
    or glands.
  • Interneurons send information between sensory
    neurons and motor neurons. Most interneurons are
    located in the central nervous system.

49
Difference between Axon Dendrites
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