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Title: INTRODUCTION%20TO%20CELLS%20


1
INTRODUCTION TO CELLS TISSUESByVijay Kapal
Graduate Studies Course CMM 5001 The Pathological
Basis Of Disease
2
Fertilization
Fertilization of egg by the sperm Egg
Sperm (23 Chromo) (23
Chromo) Fertilized egg (Zygote)
(46 Chromosomes) Human body
Sperm
Ovum (Egg) Sperm
Zygote
3
Implantation
Zygote
Blastocyst
Uterus Uterine glands Maternal blood vessels
4
3-layered Flat Embryo
Ectoderm (1) Mesoderm (3) Endoderm (2)
Fertilized egg or Zygote (Single cell) 3-layers
of cells All Tissues Organs of Human body
5
Human Genome
Nucleus Cytoplasm Cell membrane
Cell
Each cell has 46 chromosomes Form 23 homologous
pairs Each parent contributes 23 Autosomes
44 Sex chromosomes 2 (Male XY, Female XX)
Chromosomes (2N 46)
Each autosome of a homologous pair look alike But
each sex chromosome do not look alike
6
Cell Cycle
Paclitaxel Vincristine Vinblastine Colchicine
Nondividing cells (Fixed postmitotics)
M
Resting cells (Reverting postmitotics)
G0
G1
G2
Bleomycin Etoposide
S
Methotrexate
7
Mitosis Meiosis
A Homologous Pair (2 Chromosomes)
1 2 46
1 pair 23 pair
1st Division
2nd Division
Daughter Somatic Cells (2) Gametes (4)
8
Meiosis
Takes place only in testes and ovaries Is a
reductional division Main purpose is to reduce
the number of chromosomes from 2N to 1N in sperms
eggs (Chromosomes of each homologous pair will
separate from each other) Homologous pair 1
chromosome from each parent (at fertilization) 2N
46 chromosomes (2 sets) 1N 23 chromosomes
(1set) So Sperm 1N chromosomes (23) Egg
1N chromosomes (23) Fertilization restores
chromosome number again to 2N 46 chromosomes (2
sets)
9
Human Body
Cells Tissues Organs Human body
Cell
Tissue
10
Cell Organelles
  • Nucleus Chomatin, Transcription
  • Rough ER Protein synthesis Segregation
  • Smooth ER Fat Steroid synthesis
    Detoxification
  • Golgi Complex Concentrating, Modifying
    Packaging of secretory products
  • Lysosomes Intracellular digestion
  • Peroxisomes Contain oxidative enzymes Use
    catalase to degrade H2O2 H2O O2
  • Mitochondria Oxydative phosphorylation ATP
    production
  • Cell Membrane Lipid bilayer layer with
    intramembranous proteins
  • Cell cytoskeleton Actin filaments, Microtubules,
    intermediate filaments

11
Cell Organelles
Mitochondria Lysozome Golgi Nucleus Rough ER
12
Cells, Tissues Various Topics Of Research
  • Subcellular localisation trafficking of
    molecules and oganelles
  • Cell-cell and cell-extracellular matrix
    interactions
  • Cell cytoskeleton and receptor dynamics and
    functions
  • Cell and tissue differentiation and remodelling
  • Genetically engineered cells and tissues
  • Three-dimensional reconstructions, particularly
    of expression patterns over time
  • Cell cycle and cell lineage analysis involving
    gene expression profiles
  • Apoptosis
  • Gene expression analysis from histological
    preparations
  • Functional genomics proteomics
  • Techniques used in molecular histology

13
Epithelial Tissue
Outer layer of skin Inner lining of
trachea Inner lining of ducts of sweat glands
14
General Features
  • Diversity
  • Metaplasia
  • Lining and Covering
  • Basal Lamina
  • Renewal
  • Avascularity
  • Cell Packing
  • Derivation

15
Classifying Principles
  • 1. Number of cell layers
  • 1. Simple epithelia
  • 2. Stratified epithelia
  • 3. Pseudostratified epithelia
  • 2. Shape of the surface cells
  • 1. Squamous cells
  • 2. Cuboidal cells
  • 3. Columnar cells
  • 3. Luminal surface modifications
  • 1. Microvilli (Brush border)
  • 2. Cilia
  • 3. Stereocilia

16
Specific Epithelial Types
  • Simple squamous epithelium
  • Simple cuboidal epithelium
  • Simple columnar epithelium
  • Pseudostratified epithelium
  • Stratified Squamous epithelium
  • a) Keratinized
  • b) Nonkeratinized
  • Stratified cuboidal epithelium
  • Stratified columnar epithelium
  • Transitional epithelium

17
Types of Epithelia
Simple squamous Stratified squamous
Transitional
Simple cuboidal stratified cuboidal
Full Empty Bladder
Simple columnar Pseudostratified
18
Kidney (Epithelium)
Simple squamous Simple cuboidal
Kidney Tubules
19
Small Intestine (Simple Columnar)
Absorptive cells Nucleus Brush border Lamina
propria Lumen of gut
20
Esophagus (Stratified Squamous)
Epithelium Lamina propria
21
Skin (Stratified Squamous)
Epidermis (Epithelium) Dermis (Connective
tissue)
22
Trachea (Pseudostratified Epithelium)
Epithelium Cilia Ciliated cells Goblet
cells Basal lamina Lamina propria
23
Ureter (Transitional Epithelium)
Epithelium Lumen Basal lamina Lamina propria
24
Basal Lamina
  • Next to epithelia an acellular sheet like
    structure is the Basal Lamina.
  • Component Layers Constinuent Macromolecules
  • A. Component Layers
  • Lamina lucida
  • Lamina densa
  • B. Constituent Macromolecules
  • Lamina lucida (Laminin that binds to cell
    surface integrins, collagen IV)
  • Lamina densa (Type IV Collagen)
  • Basement Membrane
  • Basal lamina accompanied by reticular lamina
    (Type III Collagen) is called the basement
    membrane.
  • Functions
  • Forms sieve-like selective barrier between the
    epithelia connective tissue.
  • Aids in cell organization, cell adhesion
    maintainence of cell shape.
  • Has a role in maintaining specific cell
    function.
  • Helps guide migrations of cells during
    development and regeneration of injured tissue

25
Polarity Specialization of Epithelial Cells
  • Specialization of the Apical Surface
  • 1. Microvilli (Enterocytes Proximal convoluted
    tubule cells))
  • 2. Cilia (Trachea, Bronchus etc.)
  • 3. Stereocilia (Epididymis)
  • 4. Flagella
  • Specialization of the Lateral Surfaces
  • 1. Zonula occludens (Tight junctions)
  • 2. Zonula adherens (Intermediate junctions)
  • 3. Macula adherens (Desmosomes)
  • 4. Gap junction (Nexus)
  • Specialization of the Basal Surface
  • 1. Basal lamina
  • 2. Hemidesmosome
  • 3. Sodium-potassium ATPase
  • D. Intracellular Polarity

26
Cell Junctions
Microvilli Zonula occludens Zonula
adherens Terminal web Macula adherens Gap
junction Nucleus Hemidesmosome
27
Mucous Membranes
  • Components of Mucous Membrane
  • 1. Epithelium
  • 2. Basement membrane
  • 3. Lamina propria

28
Mucous Membrane
Epithelium Basal lamina Lamina propria
29
Serous Membranes
  • Components of Serous Membrane
  • 1. Epithelium called mesothelium
  • 2. Basement membrane
  • 3. Submesothelial connective tissue layer

30
Functions of Epithelia
  • 1. Protection from
  • Mechanical trauma
  • Dehydration
  • Pathogens
  • Secretion of
  • Hormones, milk, sweat etc.
  • Enzymes, HCl, glycoproteins,
  • Mucous serous products
  • Lubrication of
  • Contents of GI tract
  • Fetus in birth canal
  • Joints
  • 4. Filtration of wastes (Urine)
  • Absorption of food (Aminoacids, Glucose, Fatty
    acids)
  • Neuroepithelium (Taste, Smell, Hearing)
  • Reproduction (Germ cells)

31
Major Types of Epithelial Cells
  • Epithelial Cells Specialized for Transport
  • 1. Ion-transporting cells (Kidney tubules, Gall
    bladder etc.)
  • 2. Cells that transport by pinocytosis
    (Endothelial cells of blood capillaries
  • Absorption (Enterocytes, Proximal convoluted
    tubule cells)
  • Secretion
  • 1. Protein-secreting cells (Acinar cells of
    pancreas, Hepatocytes)
  • 2. Polypeptide-secreting cells (APUD cells)
  • 3. Mucous cells (Goblet cells)
  • 4. Serous cells (Acinar cells of pancreas
    secretory cells of parotid salivary glands.
  • 5. Steroid-secreting cells (Adrenal cortex,
    Leydig cells etc.)
  • D. Contractile Epithelial Cells (Myoepithelial
    cells of glands)

32
GLANDS
  • Exocrine Endocrine Glands
  • Classification of Exocrine Glands
  • 1. By structure
  • a) Number of cells
  • b) Duct system
  • c) Secretory portion
  • 2. By secretory product
  • a) Mucous secretion
  • b) Serous secretion
  • c) Seromucous secretion
  • 3. By mode of secretion
  • a) Merocrine
  • b) Apocrine
  • c) Holocrine

33
Unicellular Multicellular Simple tubular
Coiled tubular Branched
Simple branched Simple acinar Compound
tubular
Compound tubulo-alveolar
34
Salivary Glands
Mucous acini Serous acini
35
Mode of Secretion
Active transport Merocrine Apocrine
Holocrine Endocrine
36
Connective Tissue
Fat Fat cells Tanden Fibroblasts Bone Osteocyt
es
37
Connective Tissue
  • Is one of the 4 basic tissues of the body.
  • Structurally it is made up of cells and large
    amount of intercellular space containing
    extracellular matrix.
  • Matrix is the dominating component of this
    tissue.
  • It forms framework, connecting, supporting and
    packing tissue of the body.
  • It also plays a dynamic role in the development,
    growth and homeostasis of other tissue types.

38
Connective Tissue
Loose connective tissue Dense connective tissue
Fibroblasts Extracellular matrix
Epithelial tissue
Mammary Glands
39
Composition
  • Cells
  • Extracellular matrix

40
Types of Cells in Loose Connective Tissue
  • Residents
  • Fibroblasts
  • Macrophages
  • Reticular cells
  • Mesenchymal cells
  • Visitants
  • Mast cells
  • Plasma cells
  • Leukocytes
  • Fat cells
  • Melanocytes

41
Loose Connective Tissue
Elastic fibers Capillary Neutrophil Plasma
cell Fibroblast Collagen fibers
Macrophage Adipocyte Mast cell Lymphocyte
42
Fibroblast (Ultrastructure)
Nucleus Rough ER Collagen Extracellular
matrix
43
Collagen Producing Cells
  1. Fibroblast-More than one type of collagen
  2. Chondroblast- Type II collagen
  3. Osteoblast-Type I
  4. Reticular cell- Type III
  5. Smooth muscle-Type I III

44
Extracellular Matrix
  • Extracellular matrix (Fibers Ground substance)
    is synthesized and secreted mainly by the
    fibroblasts the fibers are assembled in the
    extracellular space.
  • Fibers
  • Prime function is support plays strengthing
    role in
  • Ground substance
  • Functions are
  • 1. Acts as a molecular sieve stops the spread
    of noxious substances
  • 2. Plays very important role in cellular
    nutrition waste removal
  • 3. Plays a vital role in aging. Its amount
    diminishes with age and wrinkles start
    appearing.

45
Fiberous Components
  • Connective tissue fibers are long, slender
    protein polymers
  • that are present in variable proportions in
    different types of
  • connective tissue.
  • In many cases the predominant fiber type is
    responsible for
  • conferring specific properties on the tissue.
  • Collagen Fibers
  • Elastic Fibers
  • Reticular Fibers

46
Collagen Fibers
  • Collagen Fibers
  • Most abundant protein in the body.
  • Synthesis assembly
  • Collagen types-
  • Type I- most abundant occurs in loose and
    dense connective tissue bone.
  • Type II- occurs in cartilage.
  • Type III- occurs in hematopoitic tissues.
  • Type IV- occurs in basal laminae does not form
    fibers or fibrils.
  • Type V- in placental basement membranes blood
    vessels.
  • Type X- around hypertrophic, degenerating
    chondrocytes of the growth plate where bone
    formation is to occur.

47
Synthesis of Collagen
Collagens main amino acids
Glycine (34) Proline (12) Hydroxyproline (10)
  • Fibroblast
  • Procollagen (Triple-helical units)
  • Procollagen peptidase
  • Tropocollagen
  • Collagen fibril
  • Collagen fiber

Intracellular
Extracellular
48
Ground Substance
  • Proteoglycans
  • They are made up of a core protein to which
    glycosoaminoglycans (GAGs) are attached. GAGs are
    polysacharides that contain aminosugars.
  • GAGs-Chondroitin sulphate, Dermatan sulphate,
    Keratan sulphate Heparin sulphate.
  • Hyaluronic acid is a GAG but do not form
    proteoglycans.
  • Matrix viscosity and rigidity are determined by
    the amount and types of GAGs, their association
    with the core protein to form proteoglycans,
    GAG-fiber association, and GAG-GAG associations.
  • Glycoproteins
  • Fibronectin-mediates the attachment of cells to
    the extracellular matrix.
  • Laminin-a component of basal laminae that
    mediates the attachment of epithelial cells.
  • Tissue fluids
  • Salts

49
Connective Tissue Types
  • A. Connective Tissue Proper
  • 1. Loose connective tissue
  • 2. Dense connective tissue
  • a) Dense regular connective tissue
  • b) Dense irregular connective tissue
  • Reticular connective tissue
  • Elastic connective tissue
  • Mucous connective tissue

50
Connective Tissue Proper
  • A. Connective Tissue Proper
  • 1. Loose connective tissue (lamina propria)
  • 2. Dense connective tissue
  • a) Dense regular connective tissue (Tendon,
    ligament)
  • b) Dense irregular connective tissue (Dermis,
    organ capsule)

Loose CT Dense CT
51
Elastic Connective tissue
  • Elastic fibers consist of an amorphous protein
    called elastin and numerous protein microfibrils
    embedded in it.
  • Diameter range 0.1-10um.
  • Elastic fibers are collected in thick, wavy,
    parallel bundles seperated by loose collagenous
    tissue with fibroblasts.
  • Ground substance is sparse.
  • Elastic connective tissue provides flexible
    support.
  • Predominates in the ligamentum flava of the
    vertebral column the suspensory ligament of the
    penis.

52
Reticular Connective Tissue
  • These fibers look very similar to collagen but
    are thinner than them (0.1-1.5um).
  • More highly glycosylated.
  • Form delicate silver-staining network instead of
    thick bundles.
  • Composed mainly of type III collagen and some
    glycoprotein.
  • These fibers are covered by long processes of
    the reticular cells.
  • There is very little ground substance.
  • Reticular connective tissue supports motile
    cells filters body fluids.
  • It is found mainly in hematopoietic tissue (bone
    marrow, spleen and lymph nodes).

53
Reticular Connective Tissue
Reticular cell Nu
Reticular fibers Lymphocyte
Reticular cells
Lymph Node
54
Mesenchyme
  • Mesenchyme is embryonic connective tissue.
  • Its stellate and fusiform cells (mesenchymal
  • cells) are derived from mesoderm.
  • They give rise to all the connective tissue of
  • of the body.
  • These are multipotential cells and persist in
  • adults to give rise to new generations of
    connective
  • tissue cells especially during wound healing,
    bone
  • repair and tissue fibrosis.

55
Mesenchymal Tissue (Embryo)
Neural tube Mesenchyme Somite Notochord
Neural tube Extracellular matrix Mesenchymal cells
56
Histophysiology
  • A. Functions
  • 1. Support.
  • 2. Defense.
  • a) Physical
  • b) Immunologic
  • 3. Repair.
  • 4. Storage.
  • 5. Transport
  • Edema
  • Hormonal Effects
  • Nutritional Factors
  • Collagen Renewal

57
Special Types of Connective Tissues
  • Adipose tissue
  • Blood lymph
  • Cartilage
  • Bone

58
Blood
59
White Blood Cells (Granulocytes)
Neutrophil Eosinophil Basophils
Functions- Neutrophils act as first line of
defense in infections. Eosinophils respond to
allergic states parasitic infection Basophils
release heparin histamine
60
Defense System
ADAPTIVE DEFENSES (Requires immunization)
INNATE DEFENSES (Do not require
immunization)
Physical barriers Chemical barriers Soluble
factors
(Skin, mucous membranes)
Directly kill infected cells T lymphocytes B
lymphocytes
(Low pH, Mucous)
Cytotoxic
(Lysosomes, Interferons,
Acute phase proteins,
Complements)
Help
Facilitates
CELLS (Macrophages,
Granulocytes)
ANTIBODIES
Facilitate
Delayed response Highly flexible Highly
specific Memory, lasting immunity
Fast response Limited Flexibility Non-specific No
memory
61
Mast Cells
Mast cells
Functions- Produce heparin, an
anticoagulant Produce histamine to render blood
vessels permeable
62
Monocytes
Nucleus Cytoplasm Phagocytized RBC Nucleus
Nucleus Cytoplasm RBC
63
LYMPHOCYTES
B Lymphocytes deliver antibodies-mediated immune
response T lymphocytes deliver cell-mediated
immune response Natural killer cells kill tumor
nonself cells
64
Plasma Cells
Plasma cells
Lymphocyte
Plasma cells produce antibodies to fight the
infections Immunoglobulins IgG, IgA, IgM, IgE
IgD
65
Macrophage
Macrophage
Functions- Phagocytose, process present
antigens to lymphocytes Act as scavengers etc.
66
Unilocular Adipose Tissue
Adipocytes Nucleus
67
Multilocular Adipose Tissue
68
Cartilage
Perichondrium Chondroblasts Chondrocytes Lacuna Ca
rtilage matrix Isogenous group of chondrocytes
69
Primary Bone
Periosteum Osteoblasts Osteocytes Bone
matrix Bone trabecula
70
Nervous Tissue
Cerebellum Cortical neurons Spinal cord Motor
neurons Spinal ganglion Sensory neurons
71
Divisions of the Nervous System
  • Central Nervous System (CNS)
  • Peripheral Nervous System (PNS)
  • Autonomic Nervous System (ANS)

72
Nervous System
73
General Features
  • Two Classes of Cells
  • 1. Neurons
  • 2. Supporting cells
  • Impulse Conduction
  • Synapses
  • Divisions of the Nervous System
  • Embryonic Development of Nervous Tissue
  • Aging and Repair
  • Meninges
  • Blood-Brain barrier

74
Cells of the Nervous Tissue
  • Two Classes of Cells
  • 1. Neurons.
  • 2. Supporting, neuroglial or glial cells.

75
Neurons
  • Cell Body
  • Dendrites
  • Axon
  • Classification of Neurons

76
Neuron
77
Neuromuscular Junction
Skeletal muscles Motor end plate
Axon
78
Neuron
Blood capillary Glial cells Dendrites Nissl
bodies Axon hillock Nucleus Nucleolus Myelinated
axons
79
Neuron (Cell body)
  • Cell Body
  • -It is also called soma or perikaryon
  • -It is the synthetic trophic center of cell
  • -It can receive signals from axons of other
  • neurons through synaptic contacts on its
  • cell membrane and relay them to its axon
  • -Nucleus usually large, central, spherical
  • and euchromatic
  • -Nucleus with prominent nucleolus
  • -Cytoplasm contains many organelles like
  • mitochondia, lysosomes etc.
  • -Cytoplasm has abundant free polyribosomes
  • rough endoplasmic reticulum, appears
  • as basophilic purplish-blue clumps called
  • Nissl bodies
  • -Well developed Golgi to pack often
    glycosylates
  • neurotransmitters in neurosecretory, or
    synaptic vesicles
  • -Abundant neurotubules (microtubules)
    neurofilaments
  • (intermediate filaments) in soma, dendrites
    axon

80
Neuron (Dendrites)
  • Dendrites
  • -Extensions of cell body, specialized to
  • increase the surface area for incoming
  • signals
  • -Synaptic contacts are made on them
  • -Some synaptic sites on them look like
  • sharp projections called dendritic spines
  • gemmules
  • -Proximal ends has some Nissl bodies

81
Neuron (Axon)
  • Axon
  • -One axon per neuron, its cytoplasm called
    axoplasm its plasma
  • membrane, the axolemma.
  • -A complex cell process (uniform diameter)
    carries impulses away
  • from the soma.
  • -The part of the cell body where axon exits the
    soma is called the axon
  • hillock and it lacks Nissl bodies.
  • -Axon can be myelinated or unmyelinated.
  • -Myelin sheath in CNS is provided by the
    oligodendrocyte , while in
  • PNS by the Schwann cell
  • -Axon diameter myelin thickness determines the
    speed of nerve
  • impulse. Internode (Myelin covered) Node
    (without myelin)
    -Some axons have branches called collaterals.
  • -Terminal branching of axon is called terminal
    arborization.
  • -Each branch ends as a bulb-like sac called
    terminal bouton,
  • each bouton contains many mitochondria
    neurosecretory vesicles.
  • Specialized region of plasma membrane of
    bouton that take part in
  • the formation of synapse is called as
    presynaptic membrane.

82
Nerve (Myelinated axons)
Perineurium Endoneurium Nodes of
Ranvier Axon Myelin Axon
83
Myelinated Axon (E.M.)
Neurilemma Myelin Axoplasm
Node of Ranvier
84
Synapses (Chemical)
  • Synapses are specialized junctions by which a
    stimulus is transmitted from a neuron to its
    target cell.
  • 1. Presynaptic Membrane
  • This is part of plasma membrane of terminal
    bouton.
  • 2. Synaptic Cleft
  • Fluid-filled space between pre and post
    synaptic membranes.
  • 3. Postsynaptic Membrane
  • This is part of plasma membrane of the target
    cell. It is thicker
  • than presynaptic membrane due to the presence
    of receptors for
  • neurotransmitters. When enough receptors are
    occupied,
  • hydrophilic channels open, resulting in
    depolarization of the
  • postsynaptic membrane. Neurontransmitter like
    acetylcholine
  • that remains in the synaptic cleft is degraded
    by acetylcholinesterase.
  • This removal of extra acetylcholine allows
    postsynaptic mambrane to reestablish its resting
    potential and prevents continuous firing of the
    postsynaptic neuron in response to a single
    stimulus.

85
Types of Synapses
  • Axodendritic (Between an axon a dendrite)
  • Axosomatic (Between an axon a cell body)
  • Dendrodendritic (Between dendrites)
  • Axoaxonic (Between axons)

86
Neuron (Types)
  • Based upon Configuration of cell processeses
  • Multipolar (Motor neurons of spinal cord)
  • Bipolar (Retina, olfactry mucosa)
  • Unipolar (Photoreceptors, rods cones of
    retina)
  • Pseudounipolar (Sensory neurons of dorsal root
    ganglia)
  • Based upon Cell size
  • Golgi type I (Motor neurons of spinal cord)
  • Golgi type II (Interneurons of spinal cord)
  • Based upon Function
  • Motor neurons (Multipolar neurons of ventral
    horn etc.)
  • Sensory neurons (Pseudounipolar neurons of
    dorsal root ganglia)
  • Interneurons (Golgi type II neurons)
  • Based upon Neurotransmitter released
  • Cholinergic neurons (Most somatic motor neurons)
  • Adrenergic noradrenergic neurons
    (Postganglionic sympathatic neurons)
  • Dopaminergic (Some neurons of hypothalamus)
  • GABAergic (Some neurons of the brain)

87
Types of Neurons
Unipolar Bipolar
Pseudounipolar Multipolar
88
Supporting Cells
  • Provide structural and functional support to
    neurons.
  • Take part in the formation of blood-brain
    barrier, thus monitoring the passage of materials
    from blood to neurons.

89
Supporting cells of CNS
  • 1. Astrocytes- (Blood-Brain Barrier)
  • a) Protoplasmic astrocytes
  • b) Fibrous astrocytes
  • Oligodendrocytes- (Myelin to axons in CNS)
  • Ependymal cells- (Produce the CSF)
  • Microglial cells- (Macrophages of the nervous
    system)

90
Supporting Cells of PNS
  • Schwann cells
  • A Schwann cell may envelop segments of several
    unmyelinated axons or provide a segment of a
    single myelinated axon with its myelin sheath.
    Each mylinated axon segment (internode) is
    wrapped around by layers of a Schwann cell
    process with most of its cytoplasm squeezed out.
    This multilayered Schwann cell plasma membrane
    (mainly of phospholipids) is called myelin. The
    gaps between myelin sheath segments are the nodes
    of Ranvier.
  • Satellite cells
  • Each neuron outside the CNS is surrounded by a
    single layer of cells, called satellite cells.

91
Aging and Repair
  • A neuron is a terminally differentiated cell.
  • And is incapable of undergoing mitosis.
  • Aging neurons accumulate more of lipofuscin
    pigment.
  • Neurons lost through injury or surgery cannot be
    replaced.
  • If the cell body remains intact, the injured axon
    can regenerate itself.
  • If stimulated by injury, supporting cells, unlike
    neurons, can divide.

92
Blood-Brain Barrier
  • Components of the barrier
  • 1. Endothelial cells of continuous type
    capillaries (Tight junctions)
  • 2. Basal lamina
  • 3. Cytoplasmic processes of astrocytes.

93
Blood-brain Barrier
94
Peripheral nerve
95
Peripheral Nerve (Fascicle)
Perineurium Endoneurium Myelinated axons
96
Response of Nerve Tissue to Injury
  • Damage to the Cell Body
  • A neuron is a terminally differentiated cell
    is unable to divide. So damaged or dead neurons
    cant be replaced.
  • B. Damage to the Axon
  • 1. Degenaration- Distal to the site of
    injury, axon myelin degenerate. Within 2-3
    days, they are removed these clear endoneurial
    channels are occupied by Schwann cells. Proximal
    to the site of injury, retrograde degeneration
    of axon goes up to 2 internodes, then injured
    axon is sealed. Cell body also undergoes
    changes in response to the injury. The Nissl
    bodies disappear (chromatolysis) nucleus moves
    to the periphery. (2 Weeks)
  • 2. Regeneration- Begins at 3rd week, Nissl
    bodies reappear, protein synthesis starts.
    Axons proximal stump gives off a number of
    small processes called neurites. One of these
    enters and grows in an endoneurial channel and
    synaptic contacts are remade with the target
    cell. The target cell or organ deprived of
    innervation often atrophy.

97
Nerve Injury Recovery
A B C
D E
Cell body Nissl bodies Axon Schwann
cells Motor end plate Muscle
Before injury 2 weeks 3 weeks
3 months No healing
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Muscle Tissue
Cardiac muscle Skeletal muscle Visceral
muscle
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Basic Properties of Muscle Tissue
  1. Excitability- ability to respond to a stimulus
  2. Conductivity- ability to propagate a limited
    response
  3. Contractility- ability to shorten
  4. Relaxability- ability to relax (return to
    original shape after contraction)

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IC Disc
Nucleus
Cardiomyocyte in Longitudinal Section
Endomysium
Capillary
Nucleus
Myofibrils
Cardiomyocyte
Purkinje Cell
In Cross Section
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Smooth Muscle
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Skeletal Muscle
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Cardiomyocyte (Long. Section)
Endomysium Cardiomyocytes Nucleus
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Cardiomyocytes (Cross section)
Cardiomyocytes Nucleus Myofibrils Endomysium Capil
laries
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Comparison Of Types Of Muscles
Property Skeletal Muscle Cardiac
Muscle Smooth Muscle
Location Cell size/shape Nuclei Striations
Z lines T tubules Sarcoplasmic reticulum
Cell junctions
Muscles of skeleton Long cylindrical Many
peripherally located Yes
Yes Triads at A-I junctions None
Heart Short, branched Single centrally
located Yes Yes Diads at Z
line Intercalated disks
(Adherens, occludens nexi)
Visceral organs Variable, fusiform Single
central No
Dense bodies Caveolae replace T
tubules sparse Nexi (Gapjunctions)
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EM of Cardiac muscle (IC disc)
Macula adherens
Gap junction
Fascia adherens
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EM of Skeletal muscle
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