Module 2 - Cells and Tissues PDF

MODULE 2: CELLS AND TISSUES PRESENTED BY: ALARZAR  CELLS šSmallest unit of life šAll organisms are made of one or more cells šActivities of cells are dictated by their shapes, types and relative numbers of the subcellular structures they contain šCells only arise from other cells šThere...

MODULE 2: CELLS AND TISSUES PRESENTED BY: ALARZAR  CELLS šSmallest unit of life šAll organisms are made of one or more cells šActivities of cells are dictated by their shapes, types and relative numbers of the subcellular structures they contain šCells only arise from other cells šThere are over 250 different cell types CELLS šA generalized, composite cells has: 1. Plasma Membrane – selectively permeable barrier 2. Cytoplasm – intracellular fluid packed with organelles 3. Nucleus – organelle that controls cellular activities EXTRACELLULAR MATERIALS š Substances contributing to body mass that are found outside of the cells š ECF (extracellular fluid) – includes interstitial fluids, blood plasma, cerebrospinal fluid (CSF) š Cellular secretions – substances that aid in digestion (gastric fluids) or act as lubricants (saliva) š Extracellular matrix (ECM) – most abundant material, jellylike substance composed of proteins and polysaccharides PLASMA MEMBRANE š Phospholipid bilayer with protein molecules plugged in as a fluid mosaic 1. Membrane Lipids – forms the fabric of the membrane (phospholipid + cholesterol) 2. Membrane Proteins – allows the membrane to communicate with its environment, responsible for specialized membrane function 3. Membrane Carbohydrates – includes glycoproteins and glycolipids. Glycocalyx (carbohydrate rich area) provides identity molecules for specific biologicals markers. 4. Cell Junctions - allow neighboring cells to adhere and to communicate, inhibit or aid in allowing movement of molecules between cells Plasma Membrane Functions of the Plasma Membrane 1. Physical Barrier – encloses the cell, separating the cytoplasm from the extracellular fluid 2. Selective Permeability – determines which substances enters or exit the cell 3. Communication – plasma membrane proteins interact with specific chemical messengers and relay messages to the cell interior 4. Cell Recognition – cell surface carbohydrates allow cells to recognize each other Membrane Lipids Membrane Proteins Functions Membrane Proteins Functions Cell Junctions PASSIVE MEMBRANE TRANSPORT 1.Simple Diffusion – diffuse directly through the lipid bilayer (usually small nonpolar molecules that readily dissolve in lipids) 2.Facilitated Diffusion – either through a) binding to carrier proteins or 2) through water filled channel proteins 3.Osmosis – diffusion of a solvent through a membrane TONICITY š Refers to the ability of a solution to change the shape of cells by altering the cells; internal water volume š Isotonic – have the same concentrations of nonpenetrating solutes as those found in the cells, retain shape, exhibit no net loss or gain of water š Hypertonic – higher concentration of nonpenetrating solutes than seen in the cell, lose water, shrivel or crenate š Hypotonic – more dilute than cells, cells plump up or lyse ACTIVE TRANSPORT šRequires transport proteins that combine specifically and reversibly with the transported substances šMove solutes uphill, against a concentration gradient using energy ACTIVE TRANSPORT ACTIVE TRANSPORT Membrane Potential š Also termed as voltage, electrical potential energy resulting from the separation of oppositely charged particles š In cells, charged particles are ions and the barrier is the plasma membrane š RESTING MEMBRANE POTENTIAL – ranging from (-)50 – (-)90 mV. š All cells are electrically polarized at the membrane š The cell interior remains electrically neutral  PISO, POTASSIUM AND SODIUM ROLES š The resting membrane potential is determined mainly by the concentration gradient of K+ š Sodium drives the extracellular concentration  Cell Adhesion Molecules (CAMs) š According to Ren, Roberts and Shi (2011), adhesion molecules are cell surface proteins that mediate the interaction between cells, or between cells and the extracellular matrix (ECM). š Plays key roles in: 1. Used as an anchor to other molecules in the extracellular space 2. arms that migrating cells use to haul themselves past one another 3. Signals that stick out from the blood vessel lining that rally WBCs to a nearby infected or injured area 4. Mechanical sensors that transmit information about changes in the ECM Ren G, Roberts AI, Shi Y. Adhesion molecules: key players in Mesenchymal stem cell-mediated immunosuppression. Cell Adh Migr. 2011 Jan-Feb;5(1):20-2. doi: 10.4161/cam.5.1.13491. Epub 2011 Jan 1. PMID: 20935502; PMCID: PMC3038091.  š Diverse group of integral proteins that serve as binding sites which play a role in: 1. Contact Signaling – in which cells come together, touch and recognize one another. Useful in development and Plasma immunity Membrane 2. Chemical Signaling – process in which a Receptors ligand (chemical messenger) binds a specific receptor and initiates a response  š Includes Ligands 1. Neurotransmitters – signals from the nervous system 2. Hormones – signals from the endocrine system 3. Paracrines - chemicals that act locally and are rapidly destroyed  CHEMICAL SIGNALING 1. Ligand is sent out and binds to a specific receptor 2. The receptor’s structure changes and cell proteins are altered 3. Cell response Types of Chemical Signaling G-Protein-Coupled Receptors (GPCR) š Types of plasma membrane receptor that act through G-protein to start a second messenger cascade š G-protein – regulatory molecule that acts as a middle-man to activate either 1) membrane bound enzyme or 2) ion channel š 2 Important second messengers are 1) Cyclic AMP and Ionic Calcium and activates protein kinase enzymes Cytoplasm “Cell Forming Material” š Cell material between the plasma membrane and the nucleus š Stie of most cellular activities š Includes 3 major elements: 1) Cytosol - viscous, semi-transparent fluid in which other cytoplasmic elements are suspended 2) Organelles – metabolic machinery of the cell that synthesize proteins, generate ATP 3) Inclusions – chemical substances like stored nutrients, lipid droplets and pigments  CYTOPLASM Organelle Function and Characteristics Mitochondria Powerplants of the cell, providing ATP supply Lozenge-shaped organelles that contains its own DNA, RNA, ribosomes and able to reproduce themselves Ribosomes Sites of protein synthesis Small-dark staining granules composed of proteins and RNA Endoplasmic Extensive system of interconnected tubes and parallel sacs Reticulum Rough ER – studded with ribosomes that manufacture all proteins secreted from cells; manufacture of integral proteins and phospholipids that form part of all cellular membranes Smooth ER – contains integral proteins called enzymes that catalyze reactions  CYTOPLASM Organelle Function and Characteristics Golgi Modify, concentrate and package the proteins and lipids Apparatus Stacked, flattened membranous sacs associated with tiny membranous vesicles Peroxisomes Spherical membranous sacs containing enzymes (numerous in kidneys and livers) Oxidases and Catalases detoxify alcohol and formaldehyde and neutralize free radicals Lysosomes Spherical membranous organelles containing activated hydrolytic enzymes Digests all kinds of biological molecules including invading bacteria and cell debris ENDOMEMBRANE SYSTEM š System of organelles that work together mainly to š Produce, degrade, store and export biological molecules š Degrade potentially harmful substances š Includes the Golgi apparatus, ER, secretory vesicles and lysosomes  š Elaborate network of rods running through the cytosol and hundreds of accessory proteins that link these rods to other Cytoskeleton cell structures Cellular Extensions š Cilia – whiplike, motile cellular extensions that occur on the exposed surfaces of certain cells. Its actions move substances in one direction across the cell surfaces š Flagella – projections formed by centrioles but longer. The only flagellated cell is a sperm which has one propulsive flagellum. It propels the cell itself š Microvilli – tiny, finger-like extensions of the plasma membrane that project from an exposed cell surface. It increase the cell surface and and most often found in absorptive cells in the intestine and kidney Cellular Extensions  NUCLEUS š Control center and contains the instructions to build nearly all the body’s proteins š Most cells have only one nucleus but skeletal muscles, bone destruction cells and some liver cells are multinucleate š Except for RBCs (mature), all body cells have nuclei š Anucleate cells cannot reproduce and therefore live in the bloodstream for only 3-4 months before they deteriorate  CELL CYCLE šSeries of changes a cell goes through from the time it is formed until it reproduces INTERPHASE š Interphase – period from cell formation to cell division šSubphases šG1 subphase(Gap 1) – metabolically active cell, synthesizing proteins rapidly and growing vigorously, duration is variable. šS subphase – DNA is replicated, ensuring 2 future cells will receive identical copies of the genetic material šG2 subphase (Gap 2) – enzymes and other proteins are synthesized, centriole replication is complete  š Before a cell can divide, its DNA must be replicated exactly DNA š During S phase, replication begins simultaneously on several chromatin REPLICATION threads and continues until the DNA has been replicated š Sequence: 1) Uncoiling 2) Separation 3) Assembly 4) Restoration  MITOTIC PHASE : CELL DIVISION š Mitosis – division of the nucleus, is the series of events that parcels out the replicated DNA of the parent cell to two daughter cells š Prophase š Metaphase š Anaphase š Telophase š Cytokinesis – division of the cytoplasm ROLE OF RNA š Gene is the segment of a DNA molecule that carries instructions for creating one polypeptide chain š Four nucleotide bases 1) Adenine, 2) Cytosine, 3) Guanine, 4) Thymine š RNA is single strand and has 3 forms that act together to carry out DNA’s instructions for polypeptide synthesis: š Messenger RNA – carries the coded information to the cytoplasm, where protein synthesis occurs š Ribosomal RNA – 2 units form functional ribosomes which are sites of protein synthesis š Transfer RNA – ferry amino acids to the ribosomes Disposal of the Unneeded š Autophagy “self-eating” – sweeps up bits of cytoplasm and organelles into double-membrane vesicles called autophagosomes then delivered to lysosomes for digestion š Disposal of worn out proteins and organelles, allow cells to cannibalize parts to survive during starvation, helps restructure during development š Ubiquitin-Proteasome Pathway š Ubiquitin proteins attach to marked proteins ready for destruction and then hydrolyzed by proteasomes š Apoptosis – programmed cell death, rids the body of cells that are programmed to have a limited life span Developmental Aspects of Cells š The first cell of an organism is the fertilized egg. Early in development, cell specialization begins and reflects differential gene activation. š During adulthood, cell numbers remain fairly constant. Cell division occurs primarily to replace lost cells. š Cellular aging may reflect chemical insults, progressive disorders of immunity, or a genetically programmed decline in the rate of cell division with age. TISSUES  Tissues š Groups of cells that are similar in structure and perform a common or related function šEpithelial tissue covers šConnective tissue supports šMuscle tissue moves šNervous tissue controls EPITHELIAL TISSUE š Sheet of cells that covers a body surface or lines a body cavity, a boundary-forming tissue š 2 forms include: š Covering and lining epithelium – forms the outer layer of the skin, lines the cavities (urogenital, digestive and respiratory), and covers the walls and organs of the ventral cavity š Glandular epithelium – fashions the glands of the body š Functions: š Protection, absorption, filtration, excretion, secretion and sensory reception  CHARACTERISTICS OF THE EPITHELIUM 1. Polarity š Apical Surface – some are smooth and slick, most have microvilli š Basal Lamina – non-cellular, adhesive sheet consisting of glycoproteins that acts as a selective filter that determines which molecules are allowed to enter the epithelium CHARACTERISTICS OF THE EPITHELIUM 2. SPECIALIZED CONTACTS – cells fit together closely to form continuous sheets tied together by tight junctions and desmosomes 3. SUPPORTED BY CONNECTIVE TISSUE – epithelial sheets rest upon connective tissue. In between the layers, is the basement membrane that reinforces the epithelium preventing it from stretching and tearing 4. AVASCULAR BUT INNERVATED – has no blood vessels but supplied with nerve fibers 5. REGENERATION- as long as epithelial cells receive adequate nutrition, cells are replaced by cell division  CLASSIFICATION OF EPITHELIAL TISSUE š SIMPLE – found where absorption, secretion and filtration occurs š STRATIFIED – with 2 or more layers, common in high abrasion area such as lining of the mouth and skin surface CLASSIFICATION OF EPITHELIAL TISSUE BASED ON CELL SHAPE GRANDULAR EPITHELIA š GLAND – consists of one or more cells that make and secrete a particular product š SECRETION – product of a gland that can be aqueous, lipid or steroid-rich containing proteins š Glands are either š ENDOCRINE – internally secretion or EXOCRINE – externally secreting š UNICELLULAR – one-celled or MULTICELLULAR – many celled GLANDS š ENDOCRINE š Product hormones that enter the blood or lymphatic fluid to specific target organs š Structurally diverse and secretions also varies š EXOCRINE š Secrete their products onto body surfaces or into body cavities, include the liver, pancreas, salivary glands among others CONNECTIVE TISSUE š Does much more than just connect body parts š Functions include: š Binding and supporting š Protecting š Insulating š Storing reserve fuel š Transporting substances CHARACTERISTICS OF CONNECTIVE TISSUE š EXTRACELLULAR MATRIX – a structural support network made up of diverse proteins, sugars and other components and responsible for the physical maintenance of cells š COMMON ORIGIN – arise from mesenchyme (embryonic tissue)  STRUCTURAL COMPONENTS 1. GROUND SUBSTANCE - 3. CELLS – has resident cell type that unstructured materials that fills the exists in immature (blast) and space between cells and fibers mature (cyte) forms š Interstitial fluid š Mast cells š Cell adhesion proteins š Macrophages š Proteoglycans š WBC 2. FIBERS š Osteoblasts š Collagen fibers š Elastic fibers š Reticular fibers TYPES OF CONNECTIVE TISSUE  MUSCLE TISSUE š Well-vascularized tissues that are responsible for most type of body movement š Possesses myofilaments with networks of actin and myosin that bring about movement or contraction NERVOUS TISSUE š Main component of the nervous system (brain, spinal cord and nerves) which regulates and controls body functions š NEURONS – high specialized nerve cells that generate and conduct nerve impulses which enables them to 1) respond to stimuli and 2) transmit electrical impulses š SUPPORTING CELLS / GLIAL/ NEUROGLIA – non-conducting cells that support, insulate and protect delicate neurons  Membranes š Continuous multicellular sheets composed of at least 2 primary tissue types (epithelium + connective tissue) STEPS OF TISSUE REPAIR STEPS OF TISSUE REPAIR STEPS OF TISSUE REPAIR