Chapter 5: Tissues

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Chapter 5 Tissues
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Introduction

• Cells are the basic units of structure and
  function within the human organism
• Cells are organized into groups and layers called
  tissues

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Major Types Tissues

• Epithelial form protective coverings and
  function in secretion and absorption
• Connective support soft body parts and bind
  structures together
• Muscle produces body movements
• Nervous conducts nerve impulses that control
  and coordinate body activities

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Epithelial Tissues General Characteristics

• Found throughout whole body
• Covers organs
• Forms inner linings of body cavities
• Lines hollow organs
• Anchored by connective tissue by thin, non-living
  layer, called basement membrane

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Epithelial Tissue General Characteristics
Cont.

• Lacks blood vessels
• Cells divide easily and frequently (allows injury
  to heal rapidly)
• Ex. Skin cells and cells that line the stomach

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Classification of Epithelial Tissues

• Epithelial tissues are classified according to
  shape and number of layers of cells
• Simple single layer of cells
• Stratified two or more layers of cells
• Squamous thin, flattened cells
• Cuboidal cube shaped cells
• Columnar elongated cells

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Simple Squamous Epithelium

• Single layer of flattened cells
• Cells fit tightly together
• Can be easily damaged (thin and delicate)
• Allows substances to pass rather easily
• Common site for diffusion and filtration
• Ex. Lines air sacs of lungs, forms walls of
  capillaries, blood and lymph vessels, covers
  membranes that line body cavities

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Simple Cuboidal Epithelium

• Single layer of cube-shaped cells
• Centrally located nucleus
• Covers ovaries, kidney tubules, ducts of glands
• Sometimes functions in secretion and absorption
  (ex. Kidneys, glands)

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Simple Columnar Epithelium

• Single layer of Elongated cells
• Nuclei usually located near the basement membrane
• Cells can be cilliated or non-cilliated
• Cillia move constantly and aid in movement of
  substances across the membrane

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Simple Columnar Epithelium Cont.

• Microvilli specialized cylindrical processes
  that extend from the surface of cell
• Serve to increase the surface area of the cell
  membrane (increases absorption)
• Goblet Cells specialized, flask-shaped
  glandular cells scattered among columnar cells
• Secrete mucus onto tissue surface (protection)

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Pseudostratified Columnar Epithelium

• Tissue appears to be layered, but is not
• Cell nuclei are at two or more levels in a row of
  aligned cells
• Usually have cillia
• Goblet cells are usually present
• Lines passages of respiratory system
• Cillia moves the mucus (produced by the Goblet
  cells) away

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Stratified Squamous Epithelium

• Many cell layers thick
• Cells divide in deeper layers and newer cells
  push older ones outward
• As cells are moved outward, they become flattened
• Forms the outer layer of the skin
• As some cells age they become hardened,
  keratinization

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Stratified Cuboidal Epithelium

• Two or three layers of cuboidal cells
• Form the lining of a lumen
• Ducts of mammary glands
• Sweat glands
• Salivary glands
• Pancreas
• Reproductive organs

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Stratified Columnar Epithelium

• Several layers of cells
• Cells near top (superficial) are elongated
• Cells near bottom (basal) are cube shaped
• Male urethra, vas deferens
• Pharnyx

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Transitional Epithelium

• Specialized to change in response to increased
  tension
• When walls of organ contract, tissue appears
  cuboidal, when walls are distended (stretched)
  cells appear more squamous
• Inner lining of urinary bladder
• Ureters
• Urethra

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Glandular Epithelium

• Composed of specialized cells that produce and
  secrete substances into ducts or body fluids
• Found within columnar and cuboidal epithelia
• Cells make up our glands
• Exocrine glands secrete product into ducts that
  open onto internal or external surface
• Endocrine glands secrete product onto tissue
  fluid or blood

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Connective Tissues

• Bind structures
• Provide support and protection
• Fill spaces
• Store fat
• Produce blood cells
• Protect against infections
• Help repair damaged tissues
• Spaced further apart than epithelial cells

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Connective Tissue

• Tissues have good blood supplies and are well
  nourished
• Some connective tissues are rigid
• Bone and cartilage
• Some connective tissues are flexible
• Loose connective tissue, adipose tissue, dense
  connective tissue

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Connective Tissue Cell Types

• Tissues can either be composed of fixed cells or
  wandering cells
• Fixed cells present in stable numbers
• Fibroblasts large star shaped cells, that
  produce fibers by secreting proteins
• Mast Cells Large cells, located near blood
  vessels, function to prevent blood clotting,
  inflammation and alllergies
• Wandering Cells
• Macrophages originate as white blood cells,
  carry out phagocytosis, can move around, clear
  foreign particles from tissue

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Connective Tissue Fibers

• Fibroblasts produce three types of connective
  tissue fibers
• Collagenous fibers (white fibers) composed of
  collagen protein, and is a dense connective
  tissue
• Function to hold structures together (ex. Tendons
  and ligaments)
• Elastic fibers (yellow fibers) composed of
  protein called elastin
• Can easily be stretched (ex. Vocal cords)
• Reticular fibers composed of thin collagenous
  fibers, form delicate supporting networks

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Elastic Connective Tissue
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Dense Connective Tissue
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Loose Connective Tissue
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Categories of Connective Tissue

• Connective tissue proper
• Loose Connective Tissue
• Adipose Tissue
• Dense Connective Tissue
• Specialized connective tissue
• Cartilage
• Bone
• Blood

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Loose Connective Tissue

• Also known as areolar tissue
• Cells found in this type of tissue are mainly
  fibroblasts
• Cells are separated
• Binds the skin to underlying organs
• Fills spaces between muscles
• Contains many blood vessels

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Adipose Tissue

• Fat
• Specialized form of loose connective tissue
• Cells are called adipocytes
• Lies beneath the skin and between muscle spaces,
  around certain organs and joints
• Cushions joints and organs
• Insulates and stores energy

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Dense Connective Tissue

• Closely packed thick collagenous fibers and
  elastic fibers
• Composed mostly of fibroblasts
• Strong fibers allows tissue to withstand pulling
  forces
• Binds body parts together (ex tendons and
  ligaments)
• White protective layer of eyeball
• Poor blood supply

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Cartilage

• Rigid connective tissue
• Provides support, frameworks and attachments,
  forms structural models for developing bones
• Mostly composed of collagenous fibers
• Cartilage cells chondrocytes

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Types of Cartilage

• Hyaline Cartilage most common, looks like white
  glass, found on ends of bones and joints, soft
  part of nose, important in bone growth
• Elastic Cartilage contains elastic fibers,
  flexible, framework for external ears and larynx
• Fibrocartilage tough tissue, contain
  collagenous fibers, shock absorber,
  intervertebral discs, cushions bones in the knee
  and pelvic girdle

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Hyaline Cartilage
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Elastic Cartilage
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Fibrocartilage
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Bone

• Most rigid connective tissue
• Hardness due to mineral salts (calcium
  carbonateand phosphate)
• Bone cells osteocytes
• Active tissue, heals rapidly
• Bone matrix forms concentric patterns around
  longitudinal tubes called central canals
• Functional unit of bone is the osteon

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Blood

• Transports materials between interior body cells
  and those that exchange substances with the
  external environemnt
• Helps maintain stable internal environment

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Blood

• Formed elements
• Red blood cells
• White blood cells
• Platelets
• Blood plasma

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Muscle Tissues General Characteristics

• Muscle fibers cal shorten (contract)
• As they contract, the muscle fibers pull at their
  attached ends, producing movement
• Three types of muscle tissue
• Skeletal
• Smooth
• Cardiac

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Skeletal Muscle Tissue

• Found in muscles that attach to bones
• Controlled by conscious effort (voluntary muscle
  tissue)
• Tissue composed of alternating light and dark
  striations
• Stimulated by nerve impulses
• Many nuclei per cell

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Skeletal Muscle
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Smooth Muscle Tissue

• Cannot be stimulated by conscious effort
  (involuntary)
• Cells do not have striations
• Shorter than skeletal muscle
• Spindle shaped
• Single centrally located nucleus
• Found in walls of hollow internal organs
• Stomach
• Intestine
• Bladder
• Uterus
• Blood vessels

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Smooth Muscle
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Cardiac Muscle Tissue

• Only found in the heart
• Striated
• Cells join end to end, resulting in branched and
  connected networks
• Single nucleus in each cell
• Each junction between cells has an intercalated
  disc
• Controlled involuntarily

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Cardiac Muscle
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Nervous Tissue

• Found in the brain, spinal cord and peripheral
  nerves
• Nerve cells neurons
• Sense changes in their surroundings
• Respond by transmitting impulses to other
  neurons, muscles or glands
• Serve to coordinate, regulate and integrate body
  functions

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Nervous Tissue
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Nervous Tissues Cont.

• Nervous tissue also contains Neuroglial cells,
  which are supporting cells (support and bind
  nervous tissue)