Overview of the Cellular Basis of Life

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Chapter 3 Cells and Tissues

• Overview of the Cellular Basis of Life
• building blocks of all living things
• human body has 50 to 60 trillion of these tiny
  building blocks.
• carry out all chemical activities needed to
  sustain life.
• made of four primary elements- carbon, hydrogen,
  oxygen and nitrogen
• 60-80 of our cells are made of water (one reason
  it is essential for life)
• constantly bathed in a dilute saltwater solution
  called interstitial fluid where all exchanges
  between cells and blood are made

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II. Anatomy of a Cell

• Anatomy of a Cell
• Cells are organized into three main regions
• 1. Nucleus that contains DNA
• 2. Cytoplasm
• 3. Plasma Membrane (cell membrane)
• a. barrier for cells contents
• b. double phospholipids bilayer
• c. Selectively permeable- regulates what enters
  and leaves the cell

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d. Plasma membrane junctions the meeting of two
adjacent cell membranes. There are three types

1. Tight junctions- fit together like a zipper
   forming an impermeable junction. These exist in
   cells lining the digestive tract to keep
   digestive enzymes and microorganisms from seeping
   into the bloodstream.
2. Desmosomes- anchoring junctions that prevent cell
   separation. These are abundant in tissues that
   are subjected to great mechnical stress, such as
   skin cells.
3. Gap junctions- the cells are connected by hollow
   cylinders (connexons) which allows chemical
   substances to pass between cells. These are
   abundant in heart muscle tissue where the
   movement of ions from cell to cell to synchronize
   the heart rhythm.

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Cell Diversity

• All cells share the same general structures a
  cell membrane, a nucleus and cytoplasm. However,
  their function in the body is different. See
  examples below

Secretory vs. Absorptive Epithelial Picture
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Eukaryotic Cell
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• 4 Tissue types found in the body

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III. Body Tissues

• Tissues are groups of cells with similar
  structure and function.
• Four primary tissues types
• 1. Epithelium (covering)
• 2. Connective (support)
• 3. Nervous Tissue (control)
• 4. Muscle (movement)

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IV. Epithelium

• Found in different areas of the body, such as
  body coverings, body linings, and glandular
  tissue.
• Functions are for protection (skin), absorption
  (small intestine), filtration (kidneys), and
  secretion (glands).
• Characteristics of epithelial tissue include
• 1. Cells fit closely together
• 2. Tissue layer always has one free surface (the
  apical surface) that is exposed to the cavity of
  an internal organ or the bodys exterior.
• 3. The lower surface is bound by a basement
  membrane.
• 4. Avascular (these tissues have no blood supply
  of their own)
• 5. Regenerate well if nourished.
•  
• .

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Classification of epithelium- not in your notes
but may want to write

• Number of cell layers
• simple- one layer
• stratified- more than one layer
• Shape of cells
• squamous- flattened
• cuboidal- cube shape
• columnar- column- like

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• SIMPLE SQUAMOUS - single layer (simple) of very
  thin, flattened cells (squamous).
• Function diffusion and filtration. Found in air
  sacs of lungs, walls of capillaries.

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• SIMPLE CUBOIDAL - single layer, cube-shaped
  cells. Function Secretion and absorption. Found
  Lining of kidney tubules, ducts of glands,
  covering surface of ovaries

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• SIMPLE COLUMNAR - single layer, elongated cells
  with their nuclei in about the same position in
  each cell (usually near the basement membrane).
  Protection, secretion, absorption. Found in the
  lining of digestive tract and uterus- contains
  scatter goblet cells functioning in the secretion
  of mucus- some columnar cells (involved in
  absorption) have tiny finger-like processes from
  their free surface called microvilli (increases
  surface area)

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• STRATIFIED SQUAMOUS - muli-layered, squamous
  cells. Thicker tissue.Functions in protection.
  Found lining body cavities like the mouth and
  outer layer of skin

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• PSEUDOSTRATIFIED COLUMNAR - appear "stratified"
  but really a single layer with nuclei at various
  levels giving the appearance of layered cells.
  Usually ciliated (tiny, hair-like projections for
  sweeping materials along a surface). Contains
  goblet cells.- Function secretion and
  cilia-aided movement- Location lining air
  passages like the trachea and tubes of the
  reproductive system

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• TRANSITIONAL EPITHELIUM - thick, layered cuboidal
  cells. "Stretchable" tissue, also forms barrier
  to block diffusion. Found lining of urinary
  bladder.

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Types of Epithelium
Thin for gas exchange between alveoli and
capillaries
Can secrete mucus and have cilia to help clean air
Some cells Shorter and nuclei Appear at
different Heights above membrane
Contain lots of golgi and ER to manufacture and
secrete or absorb
Many layers of cells to replace those lost when
swallowing
Common in glands
Adapted for secretion (goblet cells) of mucus
and ciliated to propel food
Stretches as bladder fills with urine
Cells at basal layer Are cuboidal or columnar
and vary at the free surface
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Connective Tissue

• A Found everywhere in the body, the most abundant
  and widely distributed tissue.
• Functions include binding tissues together,
  support, and protection
• Characteristics of connective tissue
• 1. Variations in blood supply- some tissue types
  are well vascularized (have good blood supply),
  while some have a poor blood supply (tendons and
  ligaments). Cartilage is avascular.

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Connective Tissue

• 2. Extracellular matrix- the nonliving material
  that surrounds the tissue. (This is what makes
  connective tissue so different from other
  tissues.)
• Matrix is composed of a ground substance (water,
  protein, and other molecules) and fibers
  (collagen, elastic, reticular).
• The matrix allows connective tissue to act as a
  soft packing tissue around organs (adipose
  tissue), to bear weight, or withstand stretching
  and abrasion (bones, tendons and ligaments).

• Mast cells (prevents clots)
• ? Macrophages (consumers)
• ? Fibroblasts (produce fibers)

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Connective Tissue D. Connective tissue types

• Bone (osseous) - composed of bone cells, hard
  matrix of calcium salts, large numbers of
  collagen fibers.
• used to protect and support the body

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Connective Tissue D. Connective tissue types

• Hyaline Cartilage- most common type of cartilage,
  composed of collagen and matrix
• Entire fetal skeleton is hyaline cartilage, but
  by the time of birth, most cartilage is replaced
  by bone.

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V. Connective Tissue D. Connective tissue
types

• Elastic cartilage- provides elasticity
• Example- supports the external ear
• Fibrocartilage- highly compressible
• Example- forms cushion-like discs between
  vertebrae

 
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V. Connective Tissue D. Connective tissue types

• Dense connective tissue- main matrix element is
  collagen fibers which form strong rope-like
  structures, (the collagen producing cells are
  called fibroblasts)
• Example- tendons (attach muscle to bone),
  ligaments (attach bone to bone)

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V. Connective Tissue D. Connective tissue types

• Areolar connective tissue- most widely
  distributed connective tissue that serves as a
  kind of universal packing material between other
  tissues
• contains all fiber types,
• can soak up excess fluid (this is the tissue that
  swells causing edema)
• universal packing tissue and glue that holds
  internal organs together

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V. Connective Tissue D. Connective tissue types

• Adipose tissue- commonly called fat

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V. Connective Tissue D. Connective tissue types

• Blood- blood cells surrounded by a fluid matrix
• fibers are visible during clotting
• functions as the transport vehicle for materials

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IV. Muscle Tissue

• Functions to produce movement
• Three types are
• Skeletal muscle- voluntary, striated
• Smooth muscle involuntary, surrounds organs
• Cardiac muscle- involuntary, only in heart,
  striated
• Intercalated disks are the junctions that allow
  heart cells to rapidly conduct electrical
  impulses through the heart.

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VII. Nervous Tissue

• Composed of neurons and nerve support cells
• Functions to send and receive impulses to other
  areas of body
• Located in nervous system structures such as the
  brain, spinal cord and nerves.

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How can we tell the difference between
connective, muscle, epithelial and nervous tissue?
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What are mast cells?

• Mast cell A connective tissue cell whose normal
  function is unknown but which is frequently
  injured in allergic reactions, releasing
  chemicals including histamine that are very
  irritating and cause itching, swelling, and fluid
  leakage from cells. These allergic chemicals may
  also cause muscle spasm and lead to lung and
  throat tightening, as in asthma. Also known as a
  mastocyte or labrocyte.

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Wound healing videos

• http//www.youtube.com/watch?vFraKUUetOpc

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3 Phases of Wound Healing

• Inflammatory-
• Redness, swelling, pain are symptoms
• Increase in capillary permeability
• Clotting occurs (platelets)
• Phagocytes (type of WBC) moves in
• Growth factors attract fibroblasts (cells that
  make matrix and collagen)

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Proliferative Phase

• Granulation tissue forms, this involved
  fibroblast cells actively secreting collagen
• Angiogensis- new blood vessels form
• Endothelial cells from granulation tissue- which
  is the foundation of scar tissue development
• Epithelialization- new epithelial cells
• White blood cells leave, swelling goes down

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Remodeling Phase

• Final scar tissue formed
• Scar becomes avascular

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VIII. Tissue Repair (Wound Healing) A. Two
types of tissue repair 1. Tissue regeneration
is the replacement of destroyed tissue by the
same kind of cells 2. Fibrosis occurs when
repair by dense fibrous connective tissue
called scar tissue forms. Fibrosis occurs in
cardiac and nervous tissues of the body. B.
The type of tissue repair depends on the type of
tissue damage and the severity of the injury.
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C. Steps in Tissue repair 1. Capillaries become
very permeable. 2. Clotting proteins, platelets,
macrophages, and other substances seep into the
injured area. 3. A clot is constructed to wall
off the injured area (when the clot dries and
hardens this forms the scab). 4. Formation of
granulation tissue (delicate tissue that is
made of new capillaries that grow into the
damaged area). Replaces the clot! a. this
tissue also contains fibroblasts that synthesize
collagen fibers that bridge the gap 5. Surface
epithelium regenerates this covers an
underlying layer of fibrosis (the scar).
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• D. The regeneration of tissue
• 1. Tissues that regenerate easily epithelial,
  fibrous connective, and bone
• 2. Tissues that regenerate poorly skeletal
  muscle
• 3. Tissues that are replaced largely with scar
  tissue cardiac and nervous tissue within the
  brain and spinal cord. Scar tissue lacks the
  normal flexibility of tissues which hinders the
  functioning.
• As we age there is a decrease in mass and
  viability of most tissues. The epithelia thin,
  the amount of collagen in the body declines which
  makes tissue repair less efficient, and nervous
  tissues begins to atrophy.

CNS neurons cannot regenerate, but PNS neurons
can!