8 Meiosis 2N = 46 chromosomes (2 sets) 1N = 23 chromosomes (1set) Takes place only in testes and ovariesIs a reductional divisionMain 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)SoSperm = 1N chromosomes (23)Egg = 1N chromosomes (23)Fertilization restores chromosome number again to 2N = 46 chromosomes (2 sets)
9 Human BodyCellsTissuesOrgansHuman bodyCellTissue
10 Cell Organelles Nucleus Chomatin, Transcription Rough ER Protein synthesis & SegregationSmooth ER Fat & Steroid synthesis & DetoxificationGolgi Complex Concentrating, Modifying & Packaging of secretory productsLysosomes Intracellular digestionPeroxisomes Contain oxidative enzymes; Use catalase to degrade H2O2 = H2O + O2Mitochondria Oxydative phosphorylation & ATP productionCell Membrane Lipid bilayer layer with intramembranous proteinsCell cytoskeleton Actin filaments, Microtubules, intermediate filaments
11 Cell OrganellesMitochondriaLysozomeGolgiNucleusRough ER
12 Cells, Tissues & Various Topics Of Research Subcellular localisation & trafficking of molecules and oganellesCell-cell and cell-extracellular matrix interactionsCell cytoskeleton and receptor dynamics and functionsCell and tissue differentiation and remodellingGenetically engineered cells and tissuesThree-dimensional reconstructions, particularly of expression patterns over timeCell cycle and cell lineage analysis involving gene expression profilesApoptosisGene expression analysis from histological preparationsFunctional genomics & proteomicsTechniques 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 RenewalAvascularityCell PackingDerivation
15 Classifying Principles 1. Number of cell layers:1. Simple epithelia2. Stratified epithelia3. Pseudostratified epithelia2. Shape of the surface cells:1. Squamous cells2. Cuboidal cells3. Columnar cells3. Luminal surface modifications:1. Microvilli (Brush border)2. Cilia3. Stereocilia
22 Trachea (Pseudostratified Epithelium) CiliaCiliated cellsGoblet cellsBasal laminaLamina propria
23 Ureter (Transitional Epithelium) LumenBasal laminaLamina propria
24 Basal LaminaNext to epithelia an acellular sheet like structure is the Basal Lamina.Component Layers & Constinuent Macromolecules:A. Component LayersLamina lucidaLamina densaB. Constituent MacromoleculesLamina 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. FlagellaSpecialization 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 lamina2. Hemidesmosome3. Sodium-potassium ATPaseD. Intracellular Polarity:
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.
43 Collagen Producing Cells Fibroblast-More than one type of collagenChondroblast- Type II collagenOsteoblast-Type IReticular cell- Type IIISmooth muscle-Type I & III
44 Extracellular MatrixExtracellular matrix (Fibers & Ground substance) is synthesized and secreted mainly by the fibroblasts & the fibers are assembled in the extracellular space.FibersPrime function is support & plays strengthing role inGround substanceFunctions are1. Acts as a molecular sieve & stops the spread of noxious substances2. Plays very important role in cellular nutrition & waste removal3. Plays a vital role in aging. Its amount diminishes with age and wrinkles start appearing.
45 Fiberous ComponentsConnective tissue fibers are long, slender protein polymersthat are present in variable proportions in different types ofconnective tissue.In many cases the predominant fiber type is responsible forconferring 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 Fibroblast Procollagen (Triple-helical units) Collagen’s main amino acidsGlycine (34%)Proline (12%)Hydroxyproline (10%)FibroblastProcollagen (Triple-helical units)Procollagen peptidaseTropocollagenCollagen fibrilCollagen fiberIntracellularExtracellular
48 Ground Substance Proteoglycans: Glycoproteins: Tissue fluids: Salts: 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:
51 Elastic Connective tissue Elastic fibers consist of an amorphous protein called elastin and numerous protein microfibrils embedded in it.Diameter range um.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 ( um).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).
54 Mesenchyme Mesenchyme is embryonic connective tissue. Its stellate and fusiform cells (mesenchymalcells) are derived from mesoderm.They give rise to all the connective tissue ofof the body.These are multipotential cells and persist inadults to give rise to new generations of connectivetissue cells especially during wound healing, bonerepair and tissue fibrosis.
59 White Blood Cells (Granulocytes) Neutrophil Eosinophil BasophilsFunctions:-Neutrophils act as first line of defense in infections.Eosinophils respond to allergic states & parasitic infectionBasophils release heparin & histamine
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 NeuronsCell BodyDendritesAxonClassification of Neurons
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 otherneurons through synaptic contacts on itscell membrane and relay them to its axon-Nucleus usually large, central, sphericaland euchromatic-Nucleus with prominent nucleolus-Cytoplasm contains many organelles likemitochondia, lysosomes etc.-Cytoplasm has abundant free polyribosomes &rough endoplasmic reticulum, appearsas basophilic purplish-blue clumps calledNissl bodies-Well developed Golgi to pack & often glycosylatesneurotransmitters 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 incomingsignals-Synaptic contacts are made on them-Some synaptic sites on them look likesharp projections called dendritic spinesgemmules-Proximal ends has some Nissl bodies
81 Neuron (Axon)Axon:-One axon per neuron, its cytoplasm called axoplasm & its plasmamembrane, the axolemma.-A complex cell process (uniform diameter) carries impulses awayfrom the soma.-The part of the cell body where axon exits the soma is called the axonhillock and it lacks Nissl bodies.-Axon can be myelinated or unmyelinated.-Myelin sheath in CNS is provided by the oligodendrocyte , while inPNS by the Schwann cell-Axon diameter & myelin thickness determines the speed of nerveimpulse. 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 inthe formation of synapse is called as presynaptic membrane.
82 Nerve (Myelinated axons) PerineuriumEndoneuriumNodes of RanvierAxonMyelin
83 Myelinated Axon (E.M.)NeurilemmaMyelinAxoplasmNode 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 thickerthan presynaptic membrane due to the presence of receptors forneurotransmitters. When enough receptors are occupied,hydrophilic channels open, resulting in depolarization of thepostsynaptic membrane. Neurontransmitter like acetylcholinethat 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 FunctionMotor neurons (Multipolar neurons of ventral horn etc.)Sensory neurons (Pseudounipolar neurons of dorsal root ganglia)Interneurons (Golgi type II neurons)Based upon Neurotransmitter releasedCholinergic 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 NeuronsUnipolar 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 astrocytesb) Fibrous astrocytesOligodendrocytes:- (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 lamina3. Cytoplasmic processes of astrocytes.
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 can’t 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. Axon’s 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 ECell bodyNissl bodiesAxonSchwann cellsMotor end plateMuscleBefore injury weeks weeks months No healing
99 Basic Properties of Muscle Tissue Excitability- ability to respond to a stimulusConductivity- ability to propagate a limited responseContractility- ability to shortenRelaxability- ability to relax (return to original shape after contraction)