Tissue Level of Organization

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Tissue Level Of Organization
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The Tissue Level of Organization

• Group of similar cells
• common embryonic origin
• common function
• bound together by intercellular substance
• Histology
• study of tissues

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The Origin of Tissues
Morula
Blastula
Gastrula
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4 Basic Tissues Types

• Epithelial
• Connective
• Muscle
• Nervous

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Epithelial Tissue -- General Features

• Cover surfaces, line cavities and form glands
• FUNCTION To create tissue that line, cover,
  protect, secrete.
• Attached to underlying connective tissue by a
  basement membrane.
• Cells are tightly packed together, to form tight
  network.
• Avascular---without blood vessels
• nutrients diffuse in from blood vessels in
  underlying connective tissue
• What does this mean for especially thick
  epithelia like skin?
• Rapid cell division responsive to environmental
  stresses.
• Named according to the shape and arrangement of
  cells.

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Epithelial Tissues and Their Basement Membrane
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Simple Squamous Epithelium

• Single layer of flat cells.
• lines blood vessels, form capillary walls, form
  alveoli.
• VERY THIN LAYER--.
• What is the primary function of this tissue?

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Examples of Simple Squamous Epithelium

• Section of intestine

• Surface view of lining of peritoneal (abdominal)
  cavity

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Simple Cuboidal Epithelium

• Single layer of cube-shaped cells viewed from the
  side.
• Cuboidal cells usually are found lining/forming
  gland ducts.

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Example of Simple Cuboidal Epithelium

• Sectional view of kidney tubules.

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Nonciliated Simple Columnar

• Unicellular glands goblet cells secrete mucus
• lubricate GI, respiratory, reproductive and
  urinary systems.
• Microvilli fingerlike cytoplasmic projections
  on the cell membranes top surface. Microvilli
  are designed to increase surface area to increase
  absorption.

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Example Nonciliated Simple Columnar Epithelium

• Section from small intestine
• The term brush border is often used to describe
  this tissue.

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Ciliated Simple Columnar Epithelium

• Single layer of rectangular cells with cilia,
  cilia are locomotive structures that consist of a
  9 2 arrangement of microtubules that are covered
  with cell membrane.
• Mucus from goblet cells moved along by cilia.
• Why would we want the bronchi and bronchioli
  lined with this type of tissue?

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Example Ciliated Simple Columnar Epithelium

• Section of fallopian tube.
• Why would we want this structure lined with
  cilliated columnar cells?

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Stratified Squamous Epithelium

• Several cell layers thick
• Surface cells flat
• Keratinized surface cells dead and filled with
  Keratin protein
• Examples include the skin (epidermis) and mucous
  membranes (non-keratinized)

What is the primary function of this type of
epithelium?
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Example of Stratified Squamous

• Section of vagina

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Stratified Cuboidal Epithelium

• Multilayered
• Surface cells cuboidal
• rare (only found in sweat gland ducts male
  urethra)

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Stratified Columnar Epithelium

• Multilayered
• Surface cells columnar
• Rare (very large ducts part of male urethra)

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Transitional Epithelium

• Multilayered
• Surface cells varying in shape from round to flat
  if stretched
• Lines hollow organs of the urinary tract that
  expand from within.

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Pseudostratified Columnar
PSEUDO FALSE

• Single cell layer
• All cells attach to basement membrane but not all
  reach free surface
• Nuclei at varying depths

Non-Ciliated version found in part of male
Urethra and in Vas Deferens
Ciliated version found in Trachea
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EPITHELIAL Tissues