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UNIT 3: CELLS AND TISSUES CH. 3, 5 Cell Basics Cells are the basic unit of structure and function of living things Pancreas produces insulin Individual acinar cells produce the protein insulin and dump into blood stream action is the result of individual cells Bone is collection of osteocytes – bone cells Structure is repeating units of bone cells Cell Basics - Organelles Nucleus – controls cellular activity; contains DNA a.k.a centrioles Lysosome – contains digestive enzymes Can be attached to ER or free floating in cytoplasm Centrosome – microtubules arranged in “T” formation involved in cell reproduction Chromatin – uncoiled strands of DNA Mitochondria – powerhouse of the cell; site of aerobic respiration Ribosomes – site of protein synthesis Endoplasmic reticulum – folds of interior membranes Golgi Appartus – packages, modifies proteins; gets ready for transport Vesicle – membrane bound storage unit Cytoskeleton – microtubules and microfilaments that provide a framework for cell shape cilia – short, hair-like projections Phagocytes (WBC) Peroxisome – contains catalase to decompose hydrogen peroxide into water and oxygen H2O2 H2O + O2 Smooth – lipid, carb metabolism; detoxification Rough – protein synthesis (ribosomes attached) Move substance across surface Respiratory and Female Reproductive Systems Flagella – longer, hair/tail like projection Used for cellular locomotion - sperm Movement of Materials Into and Out of the Cell Diffusion – passive (no energy) process of materials moving from a high concentration to a lower concentration Facilitated diffusion – diffusion through a protein Diffusion of gases (O2/CO2) between blood an air (in lungs; alveoli) and between blood and tissues (capillaries) Uses protein channel in cell membrane to get across barrier Osmosis – diffusion of water Hypertonic – higher concentration of solutes Hypotonic – lower concentration of solutes Water will always flow towards hypertonic env. A cell with 5% solute concentration is placed in distilled water gains water A cell with 5% solute concentration is placed in sea water (15%) loses water Filtration – uses differences in hydrostatic (water) pressure to drive materials across membrane Urinary system; capillary beds Movement of Materials Into and Out of the Cell Active Transport – use of energy (ATP) to drive materials from an area of lower concentration to an area of higher concentration Ion/proton pumps Na+/K+ pump – necessary for establishing correct ionic concentrations on both sides of a cell membrane 3 Na+ out 2 K+ in Causes a buildup of Na+ out and K+ in Endocytosis – bulk transport into the cell Pinocytosis – cell “drinking” Membrane indents liquids flow in membrane seals off fluid filled vesicle forms Phagocytosis – cell “eating” Membrane extends arms out surrounds large solid particle seals off forms vesicle Usually will fuse wit h lysosome to dissolve/digest contents Exocytosis – opposite of endocytosis; move large materials out Cell Reproduction Mitosis – making genetically identical cells Meiosis – making gametes with half the genetic information multicellular growth and repair Two gametes fuse to form zygote mitosis reproduces copies of zygote many times to form trillions of cells of baby Phases of Mitosis Interphase – individual cell growth; DNA replication Prophase \ Metaphase \ organizes DNA and separates Anaphase / chromosomes to opposite sides Telophase / of cell Cytokinesis – division of cytoplasm and cell itself Cell Reproduction Control of Cell Cycle – different tissues must reproduce at different rates If cells reproduce slower than normal tissue death holes result (stomach ulcers, skin lesions) If cells reproduce to fast, tumors can result Psoriasis – skin cells reproduce too fast Controlled by genes Cancer – loss of a cell’s ability to control the rate at which it divides; mitosis too fast Problems with genes: Tumor Suppressor genes – usually turned on to slow cell division down Oncogenes – normally turned off Cancer results when genes are activated Tumor – a mass of unspecialized cells Caner results when genes are inactivated Benign – non-cancerous Malignant – cancerous Damages healthy tissue by: 1) nutrients flow to tumor, starve out healthy tissue; 2) pressure damage (can cut off blood flow) Metastasis – spread of cancer to other body parts Usually associated with lymph and vascular systems Only takes 1 cancer cell to start new tumor (mitosis produces genetically identical cells) Types of Tissues Tissues – different types of cells working together for a common purpose Kinds: 1) 2) Epithelial Tissue – covering for organs, cavities and surfaces in general Connective Tissue – supports or binds different organs together a) b) 3) Muscle tissue – tissue specialized for contractile motion a) 4) Can be used to fill spaces as well Can be very different in make-up: bone and blood are both types of C. T. Skeletal, smooth and cardiac Nervous tissue – tissue specialized for conduction of impulses Epithelial Tissues General Characteristics Acts as a covering Usually lacks blood vessels (Avascular) Must be nourished via diffusion from underlying tissues Must reproduce rapidly; continually being replaced Cells are tightly packed with little intercellular material between them Function – covering, barrier, protection Free surface – opens to outside Basement membrane – attached to surface that it is covering Also can be specialized for secretion, absorption and excretion Important Terms for Classification Simple – single row of cells Stratified – many layers Squamous – short, flat cells Cuboidal – box-like shape Columnar – tall, elongated cells Ciliated – cilia on free surface Epithelial Tissues Simple Squamous Ep. Single row of flattened cells Thinnest of coverings Allows substances to pass freely important for areas that need diffusion to happen between tissues Simple Cuboidal Ep. Alveoli (air sacs) in lungs; capillary blood vessels Single row of square shaped cells Central, spherical nuclei Ovaries, kidney tubules, ducts of salivary glands, pancreas and liver Simple Columnar Ep. Single layer of tall, elongated cells Nuclei usually at same level, near basement membrane Digestive System – specialized for secretion and absorption Microvilli – tiny folds on surface to increase absorptive surface area Goblet Cells – specialized cells for secreting mucus Epithelial Tissues Pseudostratified Columnar Ep. Appear (pseudo- = fake) to be layered, but actually only a single layer of columnar cells Respiratory tract – cells line trachea, bronchi and larger bronchioles Ciliated – cilia on free surface act to move substances across surface Contain goblet cells for mucus production Also found in reproductive tubes to move female sex cells Stratified Squamous Ep. Many layers of flattened cells Cuboidal cells near basement membrane; flattened near free surface Cells reproduce near basement membrane; flattened as they are pushed away Epidermis of skin Nuclei are at different levels in cells all cells reach basement membrane Keritinization – older cells accumulate “keratin” – protein that hardens and waterproofs the cells Also lines cavities that open directly to outside world: mouth, vagina, anal canal Stratified Cuboidal Ep. Two or three layers of cuboidal cells Generally lines lumen (cavity of a tube) Larger gland ducts – mammary, sweat, salivary and pancreas Ovarian follicles (Female Rep. Sys.) and seminiferous tubules (Male Rep. Sys.) Epithelial Tissues Stratified Columnar Ep. Many layers of columnar cells Male urethra, Vas Deferens, parts of pharynx Transitional Ep. Specialized layers to respond to changes in tension Cells near basement membrane are cuboidal; elongate as they reach free surface Must be able to expand when organ expands and tighten when organ empties Bladder and passages of urinary system Glandular Ep. Cells that are specialized to produce and secrete substances into tubes (ducts) or body fluids Exocrine – secrete into ducts that lead to internal or external surfaces See Classification Types – P141 Simple, compound, tubular, alveolar Also classified by how they secrete Merocrine – substance only Apocrine – substance + part of cell cytoplasm Holocrine – substance + all of cell interior Endocrine – secrete directly into body fluids (commonly blood) Endocrine glands revisited in Ch. 13 Connective Tissue General Characteristics Most abundant by weight Main function – bind structures together Cells generally farther apart with lots of intercellular material (matrix) Also provide support and protection; framework; fill spaces; store fat; produce blood cells; protect against infections; help repair tissue damage Matrix can vary from solid, to semi-solid, to liquid Cells usually able to reproduce – how fast depends on blood supply Cell Types Resident cells – numbers of cells are relatively constant Wandering cells – increase in numbers when needed Fibroblast – cells that produce fibers Macrophages – specialized for phagocytosis Mast Cell – produces compounds histamine and heparine Histamine – associated with inflammatory response Heparin – helps prevent blood clotting Connective Tissue Fiber Types Collagenous Fibers – tough, dense protein fibers Made of collagen – long parallel bundles White fibers Great tensile strength – resist pulling forces Dense – many; loose – few and spread out Elastic Fibers – made of protein elastin Regular – all fibers in similar direction Irregular – fibers are arranged in all directions Weaker than collagenous but can return to original shape Vocal cords and respiratory passages Yellow fibers Reticular Fibers – thin, single strands of collagen fibers Highly branched for a delicate framework Connective Tissue Loose Fibrous C. T. Adipose C. T. Delicate thin membranes Fibroblasts spread out – produce collagenous and elastic fibers Binds skin to underlying tissue Highly vascular Specialized loose C. T. for fat storage Looks like big marshmallows; filled with fat; nucleus squeezed against side Beneath skin, between muscles, around kidneys, behind eyeballs Dense Fibrous C. T. Mostly fibers; few actual cells Can be regular tendons and ligaments Can be irreguar dermis of skin Elastic C. T. Slow to heal b/c of poor vascularization Parallel stands or branching networks of elastic fibers Ligamente flava – attachments between adjacent vertebrae Larger arteries, airways Reticular C. T. Thin, collagenous fibers arranged in 3-D network Walls of liver, spleen and lymphatic organs Connective Tissue Cartilage – rigid connective tissue Provides support, framework, attachment, protection of underlying tissues, structural model for developing bones Composed mainly of collagenous fibers Chondrocytes – cartilage cells Perichondrium – covering of cartilage Ends of bones, soft part of nose, supporting rings of respiratory system Bone forms from this during development Elastic – more flexible than hyaline Provides blood to cartilage (which is avascular; slow healing) Hyaline – most common type Lacunae – spaces that chondrocytes occupy External ears and larynx Fibrocartilage – shock absorber with many collagenous fibers Intervertebral disks Connective Tissue Bones (osseous tissue) – solid connective tissue Solid matrix due to calcium phosphate and calcium carbonate (mineral salts) Attachments for muscles, leverage, protection, inorganic salt storage Osteons – basic repeating unit of bone Blood – liquid connective tissue Cells suspended in liquid plasma Red blood cells, white blood cells, platelets Hematopoietic tissue – blood cell forming tissue Osteonic (Haversion) canal – central tube Osteocytes – bone cells Lacunae – space that bone cells occupy Canaliculi – cytoplasmic extensions that connect osteocytes Red bone marrow found in spaces of bones Reticuloendothelial tissue – largely phagocytic tissue Found in blood, brain, lungs, bone marrow, spleen, liver and lymph glands Muscular Tissue Elongated cells (fibers) specialized for contraction Skeletal: Smooth: Voluntary, striated, movement of body parts Fibers contain many nuclei and mitochondria; very long Involuntary, non-striated, movement of walls of internal organs (digestive, blood vessels, urinary etc.) Cardiac: Involuntary, striated, self-exciting, rhythmic beating of heart Intercalated disks – hold cardiac cells together Nervous Tissue: Tissue specialized to transmit electrochemical messages (nervous impulses) throughout the body Neurons – functional cell of nervous system Dendrites – receiving end Cell body Axon – impulses travel down axon to terminals Synapse – space between neurons Neurotransmitters – chemicals released from axon into synapse Motor neurons – send messages to effectors (muscles and glands) Sensory neurons – receive sensory information from external and internal environment Interneurons – connect and integrate information from sensory neurons to motor neurons Neuroglial cells – accessory cells of nervous system Support, bind components of nervous system together, phagocytosis, help supply nutrients