Chapter 2 Cells AND Tissues PDF

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CHAPTER 2: CELLS AND TISSUES PART 1: CELLS Cells Structural units of all living things Smallest living unit Overview of the Cellular Basis of Life Cell Theory A  cell  is  the  basic  and  functional  unit  of organisms ; cell properties = properties of life The  activity  of  an  organism  depends  on the collective activities of its cells Principle of Complementarity  --  the  activities  of  cells  are  dictated  by  their  structure, which determines their function Continuity of life has a cellular basis 4 elements that make up a cell Carbon Oxygen Hydrogen Nitrogen Anatomy of a generalized cell The Nucleus the  control  center  ;  contains the DNA (blueprint that  contains  all  the  instructions needed for building the whole body ; contains  genes  --carry instructions  for  building proteins  ;  necessary for cell reproduction) The Nuclear envelope Nuclear  boundary  ;  double  membrane barrier When  2  of  its  layers  fuse,  it generates  openings called n  uclear pores Allows  some  substances  to  pass through Encloses a jelly-like fluid like substance called nucleoplasm Nucleolus Dark staining round bodies It is where ribosomes are assembled Chromatin Chromatin “Beads of a string” Scattered around the nucleus Wound around histones Chromosomes Coiled and condensed chromatin threads Rodlike bodies The Plasma Membrane Fragile  transparent  barrier  that  contains  cell contents  and  separates  them  from the surrounding environment Outer limiting membrane   

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The fluid mosaic model 2  phospholipid  layers  arranged  tail to tail  w/  chole  and  floating  proteins  scattered among them Glycolipids  ( phospholipids  with sugar grps attached 2 it) Hydrophilic head Attracted to water Hydrophobic tail Non polar fatty acid tails Line  up  in  the  center  of the membrane Makes  the  plasma  membrane relatively  permeable  to  most water soluble molecules The  proteins  in  the  lipid bilayer are responsible  for most of  the specialized functions of the membrane Most  proteins that span  the  membrane are involved in transport Glycoproteins  ( sugar  proteins ; determine blood type ; acts as receptors that certain bacteria, toxins and viruses can  bind  to  ;  role  in  cell  to  cell recog and  interaction  ;  acts as  adhesive or cellular glue) Glycocalyx (fuzzy, sugar rich area) Cell membrane junctions Tongue  and  groove  fashion (wavy contours) Tight junctions -

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Impermeable  junctions  that encircle  cells  and bind them together in leak proof sheets Desmosomes Anchoring junctions Prevent  cells subjected to mech  stress  fr being pulled apart Button  like  thickenings  of adj plasma  membrane  that are connected by  fine  protein filaments Strong guy wires Gap junctions Communicating junctions Commonly  found in  the heart and bet embryonic cells Neighboring cells  are connected  by  hollow  cylinders composed  of  proteins -- connexons Chem  molecule  can  pass directly through the waterfilled connexon  channels  from one cell to another

The Cytoplasm Cellular material  outside  the  nucleus  and inside plasma membrane Site of most cellular activities Factory floor 3 major components: Cytosol

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Semi  transparent  fluid  that  suspends the other elements Dissolved in the cytosol inclusions

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Chem  sub  that  may  or  may not be present Stored  nutrients  or  cell products floating in cytosol Lipid  droplets,  glycogen  granules, pigments, hair cells and mucus “Cellular pantry” Organelles -

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Little organs Specialized cellular compartments Each  type  is  specialized  to  carry  out  a  specific function Bounded by a membrane Mitochondria Sausage shaped organelles Consists of double membrane Outer:  smooth ;  featureless Inner:  shelflike protrusion -- cristae   ATP (energy for cellular work) Powerhouse of the cell Ribosomes Tiny, bilobed, dark bodies made of proteins Actual  sites  of protein synthesis Float freely in the cytoplasm Endoplasmic Reticulum -

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Network within the cytoplasm System  of  fluid  filled tunnels that coil and  twist through the cytoplasm Mini circulatory system Smooth   -  lacks  ribosomes ; lipid  metabolism ; detoxification of drugs Rough -  studded with ribosomes  ;  bldg  materials of cell membranes  are formedon or  in  it  ;  cell’s membrane factory  ;  proteins  made  on  its ribosomes  migrate into rER tunnels  ;  proteins  r dispatched in transport vesicles

Golgi Apparatus Stack  of flattened membranous sacs that r assoc w swarms of tiny vesicles Traffic director for cell proteins Secretory vesicles Lysosomes

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Membranous  bags  containing powerful digestive enzymes Capable  of  digesting worn out cell structures Cellular stomachs Abundant in wbc (phagocytes) Peroxisomes Membranous  sacs  containing powerful oxidaseenzymes that use  mol  oxygen  to  detoxify poisonous substance Disarm dangerous free radicals  ( reactive chemicals w unpaired  electrons  that can damage  the  structure of  proteins  and  nucleic  acids  ; normal  byproducts  of cell metabolism Convert  free  radicals  to hydrogen peroxide Catalase  converts  excess hydrogen peroxide to water They  replicate by  pinching in half Cytoskeleton -

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Acts  as  cell’s  bones and muscles Made up of : Microfilaments ( such as  actin and  myosin ; cell motility ) Intermediate filaments ( they help for  desmosomes  ; provide internal guy wires  to resist pulling forces) Microtubules ( made up  of  tubulin ;  determine the  overall shape  of  the cell  and distribution of organelles  ; impt during cell division) Centrioles -

Collective (centrosome) Made up of a pinwheel array of  nine  triplets  of  fine microtubules

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Directing  the  formation of mitotic spindle during cell division

Cell Extensions Cillia Whiplike  cellular  extensions  that move  substances along the cell surface Flagella Longer  projections  formed by the centrioles Sperm cell (ex of flagellated cell) Microvilli Tiny,  finger  like  extensions  of  plasma membrane  that  project  from  an exposed cell surface Increase cell surface area Cell Diversity Cells that connect body parts Fibroblast  -  has abundantroughERand large golgi app to makeandsecretethe protein building blocks of these fibers Erythrocytes  -  carries  oxygen in the blood ; biconcave disc shape Cells that cover and line body organs Epithelial  cell  -  has  abundant intermediate  filaments and desmosomes  that  resist tearing when epithelium is rubbed or pulled Cells that move organs and body parts Skeletal,cardiac,smooth muscle-filled w  abundant  contractile  filaments  so they  can  shorten  forcefully and move the  bones,  pump  blood  or  change size of internal  organs  to  move substances around the body Cells that store nutrients

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Dispose wastes Reproduce Grow Move Respond to a stimulus

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Fat cell -  produced by a large lipid droplet in its cytoplasm Cell that fight disease  WBC  -  such  as  the  macrophage ; extends  long pseudopods  to crawl through tissue to reach infection sites Cell that gathers info and controls body functions -

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Nerve  cell  -  has  long  processes  for  receiving  messages  and  transmitting them to other structures of the body Signalling  molecules : neurotransmitters Cells of reproduction Oocyte - largest cell in the body Sperm - its flagellum acts a motilewhip to propel the sperm Cell Physiology Metabolize Digest foods -

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PART 2: BODY TISSUES Tissues -

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Grp  of  cells  that  are  similar  in  structure and function Has  4  primary  types  :  epithelial,  connective, nervous, and muscle tissues Organized into organs EPITHELIAL TISSUE (covering) Lining, covering and glandular tissue of the body Covers all free body surfaces both in and out Nearly all the substances that the bodygives off or receives must pass thru the epithelium protection , absorption, filtration and secretion Secretion is a specialty of the glands Hallmarks of Epithelium EC fit closely to form cont  sheets. ; neighboring cells  are  bound  together by  specialized cell junctions The membranes have one  free  surface or edge ;  apical  surface  i s  exposed  to  the  body’s  exterior or  cavity  ;  exposed surfaces  of  some  are slick and smooth but some exhibit modifications The  basal  surface  of  epithelium  rests  on a  basement  membrane,  a   structureless  material secreted by both the EC and CTC deep  to  the epithelium ; glue holding the epithelium in place Avascular  :  no  blood  supply  of  their own  ;  they depend on diffusion of capillaries If nourished, they regenerate easily Classification of Epithelia 2 names 1st  (by no of  cell  layers)  simple  - 1 ; stratified - more than 1 2nd (by cell shape) squamous  - flat ; cuboidal -  cube like ; columnar - columns Stratified epithelia are named for cells at thefree surface Simple  epithelia  -  most  concerned with absorption, secretion  and filtration ;  usually very thin Simple squamous epithelium Single  layer  of  thin  squamous cells  resting  on a  basement membrane Like floor tiles Usually  forms  membranes  where filtration or exchange of substances  by  rapid  diffusion occurs Found in  air  sacs  of  the lungs or the alveoli Forms  the  walls of the  capillaries Forms serous membranes or serosae (slick membranes that 

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line  the ventral cavity and cover the organs in that cavity Simple cuboidal epithelium One  layer  of  cuboidal cells resting  on  the basement membrane Common in glands and ducts Forms  the  walls of the kidney tubules  and covers the surface of the ovaries Simple columnar epithelium -

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Made  up  of  a  single  layer of tall cells that fit close together Where we can see  goblet cells which  produce  a  lubricating mucus Lines  the  entire  length of  the digestive  tract  from  the stomach to anus Epithelial  membranes  that line body cavities open to thebody exterior are called mucosae or mucous membrane Pseudostratified columnar epithelium All  rests  on the basement membrane Some  of  its  cells are shorter than the others Absorption and secretion Pseudostratified ciliated columnar epithelium  l ines  most of the respiratory tract Stratified epithelia - consists of  two or morecell layers ; for protection Stratified squamous epithelium Most  common Str Ep in the body Consists of many cell layers Free edge : squamous Basement  membrane : cuboidal or columnar Found  in  sites  that receive a good deal of abuse and friction like  the  mouth, skin and esophagus Stratified cuboidal epithelium Two  cell  layers  with the surface cells  being cuboidal in shape Stratified columnar epithelium Columnar  cells  but  its  basal cells vary in size and shape Transitional epithelium -

Highly  modified, stratified squamous epithelium

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Forms  the lining  of  the urinary bladder, ureters  and part of the urethra Cells  of  the  basal layer are cuboidal or columnar Glandular Epithelium -

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Gland  -  consists  of  one  or  more  cells that  make  and  secrete  a  particular product  (secretion  --  typically  contains protein  molecules  in  aqueous  fluid ; an active process in w/c the glandularcells obtain  needed  materials  for the blood and  use  them  to  make  their  products, which is then discharged by exocytosis Endocrine  -  ductless glands ; their secretions diffuse directly into theblood vessels Exocrine  -  their  secretions  exit  through  the ducts to the epithelial surface

 CONNECTIVE TISSUE (support) Connects body parts Found everywhere in the body Most abundant and widely distributed Protecting, supporting, and binding Hallmarks of Connective Tissue Variations in blood supply -

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Well vascularized(theyhave goodblood supply) but tendons and ligamentshave poor  blood  supply --  heal very slowly when injured Extracellular matrix -

Many  diff  types  of  cells  plus varying amts of a non living substance Extracellular matrix It  what  makes  connective  tissues  diff  fr other tissue types Has 2 main elements Ground  substance  -  water plus  some cell adhesion proteins  (glue that allows connective  tissue  cells  to  attach  themselves  to  matrix  fibers) and large polysaccharide  molecules (traps  the water as they intertwine) FIbers  -  collagen  (white)  ,  elastic (yellow) and reticular fibers ; itsbuilding blocks or m  onomers are made by connective  tissue cells and secreted into ground substance Types of Connective Tissue Bones Osseous tissue Composed  of  osteocytes  sitting in cavities called l acunae Has  exceptional  ability  to  protect  and support other body organs

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Cartilage Less hard and more flexible than bone Chondrocytes is its major cell type Found in a few places in the body Most widespread is the h  yaline cartilage  w  hich  has  abundant  collagen fibers  hidden  by a rubbery matrix with a  glassy blue white appearance ; it  forms  the trachea or the windpipe Fibrocartilage  f orms  cushion like disks between  the  vertebrae  of  the  spinal column Elastic  cartilage -  found  in  structure with elasticity such as external ear Dense connective tissue -

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Collagen  fibers  are  the  main  matrix element Fibroblasts  -  fiber  forming cells ; crowded bet collagen fibers Forms tendons and ligaments Tendons - skeletal muscles to bone Ligaments - bones  to  bones  at  joints ; more stretchy than tendons Makes up the lower layers of the skin Loose connective  tissue -  s  ofter, have more cells, and have fewer fibers than any othertissue type except blood Areolar connective tissue Most widely  distributed connective tissue varietyinthe body Cobwebby  tissue that cushions  and protects the body organs it wraps Universal  packing  tissue and connective tissue glue A  soft  layer of ACT  is called  a  lamina propria Edema  -  an  abnormal accumulation  of  fluid in body parts  or  tissues  ;  causes  swelling Adipose connective tissue Forms  the  subcutaneous tissue beneath the skin Insulates  the body  ;  protects the  kidneys  ;  cushions the eyeballs Reticular connective tissue Consists  of  a delicate networks of interwoven reticular  fibers  assoc w reticular cells It  forms  the stroma -- internal framework of an organ

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Blood -

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“Cellular bleachers” where other  cells  can observe their surroundings

Vascular tissue Consists of  blood cellssurroundedbya nonliving  fluid matrix called b  lood plasma Transport vehicle for the cardiovascular system

 MUSCLE TISSUE (movement) Specialized to contract or shorten Skeletal muscle Packaged  by  connective  tissue  sheets  into organs called skeletal muscles Can be controlled voluntarily Long, cylindrical, multinucleate and haveobvious  striations Often called m  uscle fibers Cardiac muscle Found only in the heart wall Has  striations  but  has  only  one  nucleus and relatively short Intercalated discs - branching cells that fit tightly together at junctions ; contains gap junctions Involuntary control Smooth muscle Striations are not visible Single nucleus Found  in  walls  of  hollow  organs  such  as stomach, uterus, and blood vessels Contracts  much  more  slowly  and  contractions tend to last longer Ex: peristalsis  NERVOUS TISSUE (control) Irritability and conductivity Neuroglia - insulate, support and protectneurons in the structures of the nervous system  TISSUE REPAIR(WOUND HEALING) Inflammation -  general bodyresponsetoprevent further injury Immune response  -  extremely  specific and mounts  a  vigorous  attack  against recognized invaders. Tissue repair occurs in 2 major ways Regeneration  -  replacement  of destroyed  tissue  by  the  same kind of  cell Fibrosis - repair by dense connective tissue  by  the  formation  of  scar tissue which  occurs  depends  on  (1) type of tissue damage and (2) severity of injury

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Tissue  injury  sets  the  ff  series  of  events into motion Inflammation sets the stage Granulation tissue forms  Granulation tissue (delicate pink  tissue composed largely of  new  capillaries  that grow into  the  damaged  area  from undamaged  blood vessels nearby Regeneration and fibrosis effect permanent repair

 Homeostatic Imbalance Contracture -

Permanent  tightening  of the skin affecting the underlying tendons  or muscles

 PART 3: DEVELOPMENTAL ASPECTS OF CELLS AND TISSUES Neoplasm New growth May be benign or malignant Hyperplasia Certain  body  tissues  or  organs  may enlarge bc there  is  some  local  irritant  or  condition  that stimulates the cells Atrophy Decrease in size Can  occur  when  a  body  area  or  organ loses  its  normal stimulation  

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