Simple Squamous Epithelium

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Simple Squamous Epithelium

• alveoli and capillaries of lungs where gas
  exchange occurs
• kidney glomerulus and tubules where filtration
  and diffusion processes form urine
• capillaries where diffusion and osmosis occur
• ventral body cavities as mesothelium of serous
  membranes
• all vessels and the heart as endothelium

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• Simple squamous epithelium

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Simple Cuboidal Epithelium

• secretory portions exocrine and endocrine glands
• ducts of many exocrine glands
• kidney tubules

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Exocrine duct
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Kidney tubules
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Simple Columnar Epithelium

• ducts of exocrine glands
• larger tubules or collecting ducts of the kidney
• stomach, small intestine, and large intestine
• smaller respiratory tubes or bronchioles
• fallopian tubes
• goblet cells

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Ducts of exocrine glands
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Tubules of kidneys
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Digestive system
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Goblet cells
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Pseudostratified epithelium

• Nasal Mucosa

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Trachea
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Stratified EpitheliumSquamous

• Keratinized stratified squamous epithelium is
  found only in the skin!
• Thick skin has many layers of these dead cells
  cemented together.
• Thin skin has fewer layers of  living and dead
  cells but same structure.

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Thick Skin
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Thin Skin
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Non Keratinized

• the oral cavity
• esophagus to the stomach junction
• anus and rectum
• vagina and cervix

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esophagus
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Transitional

• Transitional epithelium is only found in the
  urinary tract!
• Transitional epithelium in the bladder!
• Transitional epithelium in the urethra!

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Bladder
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urethra
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Stratified Cuboidal and Columnar epithelium

• In certain ducts and along transition zones in
  body tracts, stratified columnar and cuboidal
  epithelia can occur.  As epithelial types, both
  are uncommon.  Basal cells are typically cuboidal
  with surface cells either columnar or cuboidal in
  appearance.  These types can be found in the
  larger ducts of various glands, including the
  pancreas, salivary, and sweat glands.  If you are
  viewing an epithelium and it consists of more
  than 3-4 layers of cells, it will not be one of
  these types.  Stratified squamous types and
  transitional are the only epithelia consisting of
  multiple cell layers.

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Stratified Columnar
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Stratified Cuboidal
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Glands

• Cells that secrete products via the merocrine
  method form membrane-bound secretory vesicles
  internal to the cell.  These are moved to the
  apical surface where the vesicles coalesce with
  the membrane on the apical surface to release the
  product. Most glands release their products in
  this way.

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Merocrine
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Apocrine

• In those glands that release product via the
  apocrine method, the apical portions of cells are
  pinched off and lost during the secretory
  process.  This results in a secretory product
  that contains a variety of molecular components
  including those of the membrane.  Mammary glands
  release their products in this manner.

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apocrine
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Holocrine

• The third type of secretory release, holocrine,
  involves death of the cell.  The secretory cell
  is released and as it breaks apart, the contents
  of the cell become the secretory product.  This
  mode of secretion results in the most complex
  secretory product.  Some sweat glands located in
  the axillae, pubic areas, and around the areoli
  of the breasts release their products in this
  manner.  Sebaceous glands also are of this type.

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holocrine
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Endocrine

• Endocrine glands are the hormone producing
  structures of the body.  Some, like the thyroid
  are large and obvious.  Others, for instance the
  islet cells of the pancreas, are small islands of
  endocrine cells embedded within the larger
  exocrine portion of this organ.
• In lacking ducts, endocrine cells release their
  secretory products into the interstitial spaces
  around the cells.  The hormones diffuse into
  nearby capillaries and are then carried to all
  parts of the body.  Only when the hormones
  encounter a "target organ" do they exert an
  effect.

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Islet cell of Langerhans - endocrine
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Connective

• Fluid lymph and blood
• Connective Tissue Proper loose and dense
• Supportive Connective Tissue bone and cartilage

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Lymph
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Blood
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CT Proper Loose areolar

• As the name implies, loose connective tissue
  consists of a loosely woven mix of fibers, cells,
  and ground substance.  Areolar, a more technical
  name used for this tissue type means "spaces".
   Loose connective tissue therefore possesses
  randomly arranged protein fibers with abundant
  intercellular spaces.  Scattered within the
  spaces are 7 cell types worth mentioning for
  their physiological roles

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Adipose with sweat gland
Sweat gland
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Reticular Connective - loose
Although present as the supportive tissue of
lymph nodes, glands, organs, and bone marrow,
reticular connective tissue is not that obvious.
 Small, branching, collagen fibers that form the
reticular connective tissue are usually hidden
from view by the numerous lymphatic, epithelial,
or bone marrow cells anchored to them.  The
stroma, or supporting network of reticular fibers
is best seen with special stains.
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Dense Connective Tissue (fibrous type) tendon
Notice the nuclei of fibroblasts squeezed and
flattened in rows between the collagen fibers.
 Edges of these fibers are difficult to resolve
and the elongate nuclei can be mistaken for those
of smooth muscle.  However, the "box car"
arrangments of nuclei between the fibers is a key
characteristic for dense, regular fibrous
connective tissue.
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DRCT (elastic type)
In this side by side comparison of fibrous and
elastic tendons cut in cross-section, the
relative sizes of fibers is compared.  Notice how
large and robust the collagen fibers are compared
to the smaller elastic types.  Nuclei of
fibroblasts visible along the edges of fibers are
a good indicator these are tendons in
cross-section.
Elastic type
Fibrous type
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Irregular CT - collagen

• in the dermis and hypodermis(thick skin)
• in walls of organs forming the submucosa layer
• in periosteum, perichondreum, perineurium(special
  stain), and perimysium
• in the articular capsules of synovial joints

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General structure of DICT
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Osseous Tissue
Osteon cell which produces bone matrix
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Osteocyte in lacuna
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Hyaline cartilage

• Hyaline Cartilage
• The type of protein fiber embedded within the
  matrix of cartilage determines the cartilage
  type.  In hyaline cartilage protein fibers are
  large and predominantly collagen.  The optical
  density of these fibers is the same as the ground
  substance surrounding them and as a result, they
  are not visible within the extracellular matrix.
   Hyaline cartilage subsequently appears as a very
  uniform, glossy type tissue with evenly dispersed
  chondrocytes in lacunae.  Typically,
  perichondrium is found around hyaline cartilage.

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Elastic cartilage

• Elastic Cartilage
• Elastic cartilage has a preponderance of
  dark-staining elastic fibers embedded in ground
  substance.  These fibers are clearly visible and
  this trait is the single, best identifier to be
  used for differentiating elastic cartilage from
  hyaline.  Perichondreum is also typically found
  around elastic cartilage.  Elastic cartilage is
  found in the pharyngotympanic(eusatachian) tubes,
  epiglottis, and ear lobes where needs dictate
  supportive tissues possess elasticity.

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Elastic cartilage
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Fibrocartilage

• Fibrocartilage
• Fibrocartilage(fibrous) is a type of cartilage
  that contains fine collagen fibers arranged in
  layered arrays.  In contrast to the very uniform
  appearance of hyaline cartilage, fibrocartilage
  possesses a more open or spongey architecture
  with gaps between lacunae and collagen fiber
  bundles.  It is this open spongey structure that
  makes fibrocartilage a good shock-absorbing
  material in the pubic symphysis and
  intervertebral disks.  It can appear quite
  different in these two locales.  Most textbooks
  show images of fibrocartilage from the
  intervertebral disks where it is very open and
  loose.  In the pubic symphysis, it can be much
  tighter in construction, appearing like a dense
  connective tissue with lacunae.  

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Smooth Muscle/non striated
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S.M. in arterial wall
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Striated Muscle Skeletal and Cardiac

• Skeletal

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Cardiac muscle

• Cardiac muscle is only found in the heart.  In
  views of this muscle type, striations are not as
  strong as those of skeletal muscle.  Other
  structural features are usually apparent and of
  use for identification if the striations are
  weak.
• Due to constant activity cardiac muscle has a
  constant need for oxygen and glucose delivery.
   Since these are supplied from the blood, expect
  to see more capillaries in cardiac muscle.  These
  are visible in longitudinal and cross section
  views.

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Neurons

• A view of nervous tissue will always show neurons
  with a variety of supportive cells called
  neuroglia.  Keep in mind, the only conductive
  cells(those sending impulses) are neurons.
   Neuroglia perform other functions within the
  nervous system.

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Multipolar Neuron
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Nerves

• In Cross-section

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Nerve with myelin sheath
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Pacinian Corpuscle
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Lets review again.
Connective tissue is classified as
Loose Dense regular irregular
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The 3 shapes of epithelial cells are
A. simple, stratified, pseudostratified
B. transitional, stratified, simple C.
squamous, simple, columnar D. squamous,
cuboidal, columnar E. columnar, cuboidal,
stratified
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Which region of the epithelial cell contains
microvilli or cilia?
A. apical B. lateral C. basal D. a and b are
correct E. b and c are correct
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Types of epithelial tissues include all EXCEPT

A. Stratified columnar B. Simple columnar C.
Pseudostratified D. Cuboidal E. Simple cuboidal

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What type of epithelial tissue lines blood
vessels?
A. Stratified squamous B. Simple columnar C.
Simple squamous D. Pseudostratified E. Simple
cuboidal
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All of the following are functions of epithelial
tissue EXCEPT
A. protection B. secretion C. lining D.
support E. barrier
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Which intercellular specialization allows ions
to pass from cell to cell?
A. Tight junction B. Gap junction C. Adhering
junction D. Desmosome E. C and D are correct
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The primary component of connective tissue is
A. the fibroblast (the cell) B. ground substance
(the stuffing) C. collagen (the support) D.
glycoproteins(the glue)
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All of the following are functions of connective
tissues EXCEPT
A. support B. transport C. framework D.
storage E. communication
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Tendons are composed of what type of connective
tissue?
A. loose B. dense regular C. dense irregular
D. simple squamous E. adipose