Histology: The Study of Tissues

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Chapter 1

• Histology The Study of Tissues

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Tissue Level of Organization

• The classification of tissue types is based on
  the structure of cells the composition of
  noncellular substance surrounding cells
  (extracellular matrix) and the functions of the
  cells.

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Tissues and Histology

• Tissue Level of Organization
• Epithelial
• Connective
• Muscle
• Nervous
• Histology Microscopic Study of Tissues

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Overview of Tissue Science

• An Orientation to the Tissues of the Body

Figure 4-1
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Epithelium Characteristics

• Consists almost entirely of cells
• Covers body surfaces and forms glands
• Has free and basal surface
• Avascular
• No spaces between cells

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Functions of Epithelia

• Protecting underlying structures
• Acting as barriers
• Sensation
• Secreting substances
• Absorbing substances
• Excrethion
• Diffusion, Permitting the passage of substances
• Cleaning
• Reduce friction
• contraction

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Classification

• According to the
• Shape of cells
• No. of layers

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Types of Epithelium

• Types of epithelium is based on the shape of the
  epithelial cells
• Squamous cells are flat
• Cuboidal cells are cube-shaped
• Columnar cells are taller tan they are wide.

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Classification of Epithelium

• Simple
• Squamous, cuboidal, columnar
• Consists of a single layer of cells with each
  extending from the basement membrane to the free
  surface
• Stratified
• Squamous, cuboidal, columnar
• Consists of more than one layer of cells, only
  one of which is attached to the basement membrane.

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Classification of Epithelium

• Pseudostratified
• Columnar
• Special type of simple epithelium
• It appears to be stratified but it is not (false
  psuedo)
• Consists of one layer of cells, with all the
  cells attached to the basement membrane.

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Classification of Epithelium

• Transitional
• Cuboidal to columnar when not stretched and
  squamouslike when stretched

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Simple Squamous Epithelium

• Consists of a single layer of cells, with each
  cell extending from the basement membrane to the
  free surface.

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Figure 4-4(a)
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Simple Squamous Epithelium

• Function diffusion, filtration, some protection
  against friction, secretion and absorption
• Locationlining of blood and lymphatic vessels
  (endothelium) and small ducts, alveoli of the
  lungs, loop of Henle in kidney tubules,line the
  heart.

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Types of Epithelium
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Simple Cuboidal Epithelium

• Cuboidal cells are cube-shape about as wide as
  they are tall.
• Single layer of cube-shaped cells, some cells
  have microvilli or cilia.

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• Simple Cuboidal Epithelium

Figure 4-4(b)
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Simple Cuboidal Epithelium

• Function active transport and facilitated
  diffusion result in secretion and absorption by
  cells of the kidney tubules, secretion by cells
  of glands
• movement of particles embedded in mucus out of
  the terminal bronchioles by ciliated cells.

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Simple Cuboidal Epithelium

• Location kidney tubules, glands and their
  ducts, lining of terminal bronchioles of the
  lungs, and surface of the ovaries

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Types of Epithelium
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Simple Columnar Epithelium

• Single layer of tall, narrow cells. Some cells
  have cilia (in bronchioles of lungs, auditory
  tubes, uterine tubes and uterus) or microvilli
  (intestines).

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Epithelial Tissue

• Simple Columnar Epithelium

Figure 4-4(c)
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Simple Columnar Epithelium

• Function movement of particles out of the
  bronchioles of the lungs by ciliated cells. It
  is partially responsible for the movement of the
  oocyte through the uterine tubes by ciliated
  cells. Secretion by cells of the gland, the
  stomach and the intestine. Absorption by cells
  of the intestine.

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Simple Columnar Epithelium

• Location Glands and some ducts, bronchioles of
  lungs, auditory tubes, uterus, uterine tubes,
  stomach intestines, gallbladder, bile ducts and
  ventricles of the brain.

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Types of Epithelium
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Stratified Squamous Epithelium

• Consists of more than one layer of cells, only
  one of which is attached to the basement membrane
• Cells are cubodial in shape in the basal layer
  and progressively flatten toward the surface.

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• Stratified Squamous Epithelium

Figure 4-5(c)
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Stratified Squamous Epithelium

• The epithelium can be moist or keratinized
• In most the surface cells retain a nucleus and
  cytoplasm.
• In keratinized stratified epithelium, the
  cytoplasm of cells at the surface is replaced by
  keratin, and the cells are dead

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Stratified Squamous Epithelium

• Function protection against abrasion and
  infection.
• Location moist-mouth, throat, larynx,
  esophagus, anus, vagina, inferior urethra, and
  cornea.
• Keratinized - skin

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Types of Epithelium
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Stratified Cuboidal Epithelium

• Multiple layers of somewhat cube-shaped cells.
• Function secretion, absorption and protection
  against infection.
• Location sweat gland ducts, ovarian follicular
  cells, and salivary gland ducts.

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Types of Epithelium
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Stratified Columnar Epithelium

• Multiple layers of cells, with tall, thin cells
  resting on layers of more cubodial cells. The
  cells are ciliated in the larynx
• Function protection and secretion
• Location mammary gland duct, larynx and a
  portion of the male urethra.

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Types of Epithelium
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Pseudostratified Columnar Epithelium

• Single layer of cells some cells are tall and
  thin and reach the free surface and other do not.
  The nuclei of these cells are at different
  levels and appear stratified. The cells are
  almost always ciliated and are associated with
  goblet cells that secrete mucus onto the free
  surface.

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Epithelial Tissue

• Pseudostratified Ciliated Columnar

Figure 4-5(a)
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Pseudostratified Columnar Epithelium

• Function synthesize and secrete mucus onto the
  free surface and move mucus (or fluid) that
  contains foreign particles over the surface of
  the free surface and from passages.
• Location lining of nasal cavity, nasal sinuses,
  auditory tubes, pharynx, trachea and bronchi of
  the lungs.

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Types of Epithelium
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Transitional Epithelium

• Stratified cells that appear cubodial when the
  organ or tube is not stretched an squamous when
  the organ or tube is stretched by fluid.

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Transitional Epithelium

• Function accommodates fluctuations in the
  volume of fluid in an organ or tube. Protection
  against the caustic effects of urine.
• Location lining of the urinary bladder, ureter,
  and superior urethra.

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Exocrine Glands

• Unicellular
• Goblet cells

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Exocrine Glands and Secretion Types

• Merocrine
• Sweat glands
• Apocrine
• Mammary glands
• Holocrine
• Sebaceous glands

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Multicellular Exocrine Glands