Tissues, Glands,

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Chapter 4

• Tissues, Glands, Membranes

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General Definitions

• Tissue - group of cells similar structure and
  function along with similar extracellular
  substances between the cells
• Histology microscopic study of tissue structure
• Histo- tissue, -ology study

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Four Basic Types of Tissues

• Epithelial tissues
• Epi on thele covering or lining
• Connective tissues
• Muscle tissues
• Nervous tissues

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Epithelial Tissue, Unique characteristics

1. Very little extracellular material between cells.
2. Free surface layer of cells not in contact with
   other cells.
3. Basement membrane attaches the epithelial cells
   to underlying tissues.
4. Avascular capillaries do not extend from the
   underlying tissues, so gases, nutrients, wastes
   must diffuse across the basement membrane.

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Classification of Epithelia

• Classified based on number of cell layers and
  cell shape
• Layers
• Simple epithelium 1 layer of cells
• Stratified epithelium - gt1 layer of cells
• Note When epithelium is stratified, it is named
  according to the shape of the cells at the free
  surface.

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Classification of Epithelia

• Shape
• Squamous (flat and scale-like)
• Cuboidal (cube shaped)
• Columnar (tall and thin)

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Layers or Arrangement
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Shapes
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Simple Squamous Epithelium

• Single layer of thin, flat cells
• Line blood vessels, lymphatic vessels, heart,
  alveoli, kidney tubules, serous membranes
• Diffusion, filtration, anti-friction, secretion,
  absorption

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Simple Cuboidal Epithelium

• Single layer of cube-shaped cells, some with
  microvilli or cilia
• Kidney tubules, glands/ducts, brain, bronchioles,
  ovary surface
• Secretion, absorption, movement of particles

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Simple Columnar Epithelium

• Single layer of tall, narrow cells, some with
  cilia/microvilli
• Lining of stomach, intestines, glands, ducts,
  bronchioles, auditory tubes, uterus, uterine
  tubes
• Secretion, absorption, movement of
  particles/oocytes

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Pseudostratified ColumnarEpithelium

• Single layer of cells, some tall and thin, others
  not, nuclei at different levels, appear
  stratified, almost always ciliated
• Lining of nasal cavity, nasal sinuses, auditory
  tubes, pharynx, trachea, bronchi
• Synthesis/ secretion/ movement of mucus

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Transitional Epithelium

• Stratified cells appear cuboidal when not
  stretched and squamous when stretched
• Lining of bladder, ureters, superior urethra
• Deals with changing volume of fluid in an organ,
  protects from urine contact

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Lets practice
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• Simple Columnar Epithelium

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• Simple Squamous Epithelium

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• Stratified Squamous Epithelium

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• Simple Cuboidal Epithelium

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• Stratified Columnar Epithelium

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• Pseudostratified Epithelium

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bladder
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• Transitional Epithelium

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• Stratified Cuboidal Epithelium

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Structural FunctionalRelationships

• Cell Layers Cell Shapes
• Single layers control passage of materials
  through epithelium
• Gas diffusion across lung alveoli
• Fluid filtration across kidney membranes
• Gland secretion
• Nutrient absorption in intestines
• Multiple layers protect underlying tissues
• Damaged cells replaced by underlying cells
• Protect from abrasion (ex skin, anal canal,
  vagina)

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Structural FunctionalRelationships

• Cell Layers Cell Shapes, continued
• Flat/thin (squamous) diffusion, filtration
• Diffusion in lung alveoli
• Fluid filtration in kidney tubules
• Cuboidal/columnar secretion, absorption
  contain more organelles
• Secretory vesicles (mucus) in stomach lining
• Mucus protects against digestive enzymes and acid
• Secretion/absorption in kidney tubules made
  possible by ATP production by multiple
  mitochondria
• Active transport of molecules into/out of kidney

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Structural Functional Relationships

• Free Cell Surfaces
• Smooth reduces friction
• blood vessel lining smooth blood flow
• Microvilli increase cell surface area cells
  involved in absorption or secretion
• Small intestine lining
• Cilia propel materials along cells surface
• Nasal cavity/trachea moves dust and other
  materials to back of throat (swallowed/cough up)
• Goblet cells secrete mucus to entrap the junk

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Structural FunctionalRelationships

• Cell Connections
• Tight junctions bind adjacent cells together
• Permeability layers prevent passage of
  materials
• Intestinal lining and most simple epithelia
• Desmosomes anchor cells to one another
• Hemidesmosomes anchor cells to basement
  membrane
• Epithelia subject to stress (skin stratified
  squamous)
• Gap Junctions allow passage of molecules/ions
  between adjacent cells (communication)
• Most epithelia

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Cell Connections
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Glandular Epithelium

• Gland multicellular structure secreting
  substance onto a surface, into a cavity, or into
  the blood. There are two types
• Exocrine gland (exo-outside krino-to separate)
  glands with ducts secretions pass through ducts
  onto a surface or into an organ
• Simple ducts w/o branches
• Compound ducts w/ branches
• Tubular tubes
• Acinus/alveolus saclike
• Endocrine gland (endo-within) glands w/o ducts
  that secrete into blood
• Hormones are secreted into blood

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Exocrine Gland Structures - Simple
Goblet cells are the only unicellular gland.
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Exocrine Gland Structures - Compound
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Exocrine glands Classified according to what it
Releases

• Merocrine FLUID is released (Most glands are in
  this group)
• Serous cells produce a watery secretion
  w/enzymes
• Mucous cells produce thicker secretions
• Apocrine Small portions of the cell break off
  are released
• Mammary glands, Ceruminous (ear wax), and some
  sweat glands
• Holocrine ENTIRE CELLS are released-Sebaceous
  Glands oil in the skin)

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Connective Tissue

• The most abundant and widely distributed tissue
  in the body
• Multiple types, appearances and functions
• Relatively few cells in extracellular matrix
  (think fruit cells floating or suspended
  in Jell-O).
• Matrix is made up of
• Protein fibers
• Ground substance
• Fluid

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Structure of Connective Tissue

• Three types of protein fibers
• Collagen fibers
• Rope-like resist stretching
• Reticular fibers
• Fine, short collagen fibers branched for support
• Elastic fibers
• Coiled stretch and recoil to original shape
• Ground substance combination of proteins and
  other molecules
• Varies from fluid to semisolid to solid
• Proteoglycans protein/polysaccharide complex
  that traps water

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Collagenous Fibers
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Elastic Fibers Mast Cells
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Reticular Connective Tissue
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Naming of Connective Tissue Cells

• Based on function
• Blast (germ) produce (build) matrix
• Cyte (cell) cells maintain it
• Clast (break) cells break down for remodeling
• Osteoblast (osteo-bone) form bone
• Osteocyte maintain bone
• Osteoclast break down bone
• Cells associated with the immune system are also
  found in connective tissue
• Macrophage (makros-large phago-to eat) large,
  mobile cells that ingest foreign substances found
  in connective tissue
• Mast Cells nonmotile cells that release
  chemicals that promote inflammation

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Functions of Connective Tissue

• Enclose Separate organs and tissues from one
  another
• Liver, kidney (capsules form around)
• muscles, blood vessels, nerves
• Connect tissues to each other
• Tendons muscles to bone
• Remember TTT (tendons 2 types)
• Ligaments bone to bone
• Remember LLL (ligaments like to like)
• Support and movement
• Bones, cartilage, joints

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Functions of Connective Tissue, (cont.)

• Storage
• Fat stores energy bone stores calcium
• Cushion and insulation
• Fat cushions/protects/insulates (heat)
• Transportation
• Blood transports gases, nutrients, enzymes,
  hormones, immune cells
• Protection
• Immune blood cells protect against
  toxins/tissue injury bones protect underlying
  structures

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Classification of Connective Tissues
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Loose Connective Tissue (Areolar)

• Composition ECM has fibroblasts, other cells,
  collagen, fluid-filled spaces
• Functions forms thin membranes between organs
  and binds them (loose packing material)
• Locations widely distributed, between glands,
  muscles, nerves, attaches skin to tissues,
  superficial layer of dermis

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Adipose Connective Tissue

• Composition very little ECM (has collagen and
  elastic fibers) large adipocytes filled with
  lipid
• Functions Stores fat, energy source, thermal
  insulator, protection/ packing material
• Locations Beneath the skin, in breasts, within
  bones, in loose connective tissues, around organs
  (kidneys and heart)

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Dense Fibrous/Collagenous Connective Tissue

• Composition ECM mostly collagen (made by
  fibroblasts), orientation varies
• Functions withstands pulling forces, resists
  stretching in direction of fibers orientation
• Locations tendons, ligaments, dermis of skin,
  organ capsules

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Dense Elastic Connective Tissue

• Composition ECM collagen and elastic fibers
  orientation varies
• Functions stretches and recoils strength in
  direction of fiber orientation
• Locations arterial walls, vertebral ligaments,
  dorsal neck, vocal cords

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Cartilage

• Chondrocytes (cartilage cells) inside lacunae
  (small spaces)
• No blood vessels slow healing, cant bring
  cells/nutrients necessary for tissue repair
• Three types
• Hyaline cartilage
• Elastic cartilage
• Fibrocartilage

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Types Locations of Cartilage
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Examples of Cartilage
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Hyaline Cartilage

• Composition solid matrix, small evenly
  distributed collagen fibers, transparent matrix,
  chondrocytes in lacunae
• Functions supports structures, some flexibility,
  forms smooth joint surfaces
• Locations costal cartilages of ribs, respiratory
  cartilage rings, nasal cartilages, bone ends,
  epiphyseal (growth) plates, embryonic skeleton

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Fibrocartilage

• Composition similar to hyaline, numerous
  collagen fibrous arranged in thick bundles
• Functions somewhat flexible, withstands great
  pressure, connects structures under great
  pressure
• Locations intervertebral disks, pubic symphysis,
  articulating cartilage of some joints (knee, TMJ)

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Elastic Cartilage

• Composition similar to hyaline cartilage,
  abundant elastic fibers
• Functions rigidity, more flexibility than
  hyaline (elastic fibers recoil to original shape)
• Locations external ears, epiglottis, auditory
  tubes

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Bone

• Composition hard, mineralized matrix, osteocytes
  inside lacunae, lamellae layers
• Functions strength, support, protects organs,
  muscle/ligament attachments, movement (joints)
• Locations all bones of body

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Blood

• Composition blood cells in a fluid matrix
  (plasma)
• Functions transportation (O2, CO2, hormones,
  nutrients, waste, etc.), protect from infection,
  temperature regulation
• Locations in blood vessels and heart, produced
  by red bone marrow, WBCs leave blood vessels and
  enter tissues

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Muscle Tissue

• General features
• Can contract
• Contractile proteins
• Enables movement of the structures that are
  attached to them
• Muscle fibers cells
• Three (3) types of muscle tissue
• skeletal
• smooth
• cardiac

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Skeletal Muscle

• Composition striated muscle fibers, large,
  cylindrical cells that have many nuclei near
  periphery
• Functions body movement, voluntary control
• Locations attached to bone

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Cardiac Muscle

• Composition cylindrical cells, striated, single
  nucleus, branched and connected with intercalated
  disks
• Functions pump blood, involuntary control
• Locations heart

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Smooth Muscle

• Composition cells tapered at each end, not
  striated, single nucleus
• Functions regulates organ size, forces fluid
  through tubes, regulates amount of light entering
  eye, goose bumps, involuntary control
• Locations walls of hollow organs and tubes
  (stomach, intestine, blood vessels), eye

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Nervous Tissue

• Forms brain, spinal cord, peripheral nerves
• Functions
• Conscious control of skeletal muscles
• Unconscious control of cardiac muscles
• Self and environmental awareness
• Emotions
• Reasoning skills
• Memory
• Action potentials electrical signals
  responsible for communication between neurons and
  other cells

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Nervous Tissue Structure

• Neurons conducts action potentials (a.p.s)
• Cell body contains nucleus, site of general
  cell functions
• Dendrite conduct a.p.s toward cell body
• Axon conducts a.p.s away from cell body
• Neuroglia support cells nourish, protect,
  insulate neurons

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Inflammation

• In response to tissue damage
• Viral/bacterial infections
• Trauma
• Functions
• Mobilize bodys defenses
• Destroy microorganisms, foreign materials,
  damaged cells
• Pave way for tissue repair

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Symptoms of Inflammation

• Redness
• Heat
• Swelling
• Pain
• Disturbance of function
• Inflammation is beneficial, though painful!

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Inflammatory Response

• Mediators of inflammation cause dilation ?
  permeability of blood vessels (redness/heat)
• Bring blood and important substances to site
• Edema swelling (water, proteins, etc.) of
  tissues
• Fibrin protein that walls off site keeps
  infection from spreading
• Neutrophils ingest bacteria (phagocytic WBC)
• Macrophage ingest tissue debris
• Pus mixture of dead neutrophils, cells, fluid

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Inflammation is adaptive

• Inflammation warns person from further injury
• Pain
• Limitation of movement (edema)
• Tissue destruction
• Fibroclast migrate to damaged tissue and digest

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Tissue Repair

• Substitution of viable cells for dead cells
• Regeneration same type of cells takes place of
  previous cells same function
• Replacement different type of tissue develops
  forms scars loss of some function
• Fibroclast lays down fibrin and forms scar tissue
• Type of tissue repair is determined by
• Wound severity
• Tissue types involved

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Not all cells divide alike

• Labile cells (not fixed)
• Divide continuously through life
• Skin, mucous membranes
• Stable cells
• Dont actively divide, but can after injury
• Connective tissue, glands (liver, pancreas)
• Permanent cells
• Little to no ability to divide
• Neurons, skeletal muscle
• If killed, replaced by connective tissue
• Recover from limited damage (axon of neuron)

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Review steps of tissue repair

1. Clot (fibrin)
2. Scab (seal)
3. Blood vessel dilation Fibroclast-clean up
4. Fibrin walls off
5. Epithelium replaced
6. Scab sloughs
7. Fibroblasts form granulation tissue
8. Wound contracture

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Its tough getting old

• Tissue changes with age
• ? neurons and ? muscle cells
• ? visual acuity, smell, taste, touch
• ? in functional capacities of respiratory and
  cardiovascular systems
• Slower cell division means slower healing
• ? flexibility (irregular collagen fibers in
  tendons ligaments)
• ? elasticity (elastic fibers bind to Ca2,
  becoming brittle) makes skin wrinkled too ?
• Atherosclerosis plaques in blood vessels