Download Epithelial Tissue

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky
Tissue: The Living Fabric
Part A
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
4
Tissues
 Tissue is a group of cells similar in structure and
function.
 The study of tissues is called Histology.
 The four types of tissues
 Epithelial
 Connective
 Muscle
 Nerve
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Special Characteristics of the Epithelium:
1.) Cellularity – composed almost entirely of tight
packed cells with very little extracellular space.
2.) Special contacts – form continuous sheets held
together by tight junctions and desmosomes
3.)Polarity – apical and basal surfaces.
4.) Supported by connective tissue – reticular lamina
and basal laminae
Underneath the basal surface is a thin sheet of
glycoproteins called the basal lamina. This sheet
allows the cells to migrate toward a wound and is
selectively permeable.
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Special Characteristics of the Epithelium:
 Avascular but innervated – contains no blood
vessels but supplied by nerve fibers
 Regenerative – rapidly replaces lost cells by cell
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Classification of Epithelia
 Simple or
stratified
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Figure 4.1a
Classification of Epithelia
 Squamous, cuboidal,
or columnar
Figure 4.1b
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Epithelia: Simple Squamous
 Single layer of flattened cells with disc-shaped
nuclei and sparse cytoplasm
 Functions
 Diffusion and filtration
 Provide a slick, friction-reducing lining in
lymphatic and cardiovascular systems
 Present in the kidney glomeruli, lining of heart,
blood vessels, lymphatic vessels, and serosae
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Epithelia: Simple Squamous
Figure 4.2a
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Epithelia: Simple Cuboidal
 Single layer of cubelike cells with large, spherical
central nuclei
 Function in secretion and absorption
 Present in kidney tubules, ducts and secretory
portions of small glands, and ovary surface
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Epithelia: Simple Cuboidal
 Single layer of cubelike cells with large, spherical
central nuclei
 Function in secretion and absorption
 Present in kidney tubules, ducts and secretory
portions of small glands, and ovary surface
Figure 4.2b
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Epithelia: Simple Columnar
 Single layer of tall cells with oval nuclei; many
contain cilia
 Goblet cells are often found in this layer
 Function in absorption and secretion
 Nonciliated type line digestive tract and gallbladder
 Ciliated type line small bronchi, uterine tubes, and
some regions of the uterus
 Cilia help move substances through internal
passageways
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Epithelia: Simple Columnar
Figure 4.2c
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Epithelia: Pseudostratified Columnar
 Single layer of cells with different heights; some do
not reach the free surface
 Nuclei are seen at different layers
 Function in secretion and propulsion of mucus
 Present in the male sperm-carrying ducts
(nonciliated) and trachea (ciliated)
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Epithelia: Pseudostratified Columnar
 Single layer of cells with different heights; some do
not reach the free surface
 Nuclei are seen at different layers
 Function in secretion and propulsion of mucus
 Present in the male sperm-carrying ducts
(nonciliated) and trachea (ciliated)
Figure 4.2d
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Epithelia: Stratified Squamous
 Thick membrane composed of several layers of cells
 Function in protection of underlying areas subjected
to abrasion
 Forms the external part of the skin’s epidermis
(keratinized cells), and linings of the esophagus,
mouth, and vagina (nonkeratinized cells)
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Epithelia: Stratified Squamous
 Thick membrane composed of several layers of cells
 Function in protection of underlying areas subjected
to abrasion
 Forms the external part of the skin’s epidermis
(keratinized cells), and linings of the esophagus,
mouth, and vagina (nonkeratinized cells)
Figure 4.2e
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Epithelia: Stratified Cuboidal and Columnar
 Stratified cuboidal
 Quite rare in the body
 Found in some sweat and mammary glands
 Typically two cell layers thick
 Stratified columnar
 Limited distribution in the body
 Found in the pharynx, male urethra, and lining some
glandular ducts
 Also occurs at transition areas between two other types of
epithelia
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Epithelia: Transitional
 Several cell layers, basal cells are cuboidal, surface
cells are dome shaped
 Stretches to permit the distension of the urinary
bladder
 Lines the urinary bladder, ureters, and part of the
urethra
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Epithelia: Transitional
 Several cell layers, basal cells are cuboidal, surface
cells are dome shaped
 Stretches to permit the distension of the urinary
bladder
 Lines the urinary bladder, ureters, and part of the
urethra
Figure 4.2f
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Epithelia: Glandular
 A gland is one or more cells that makes and secretes
an aqueous fluid
 Classified by:
 Site of product release –
 endocrine (internally secreting)
 Exocrine (externally secreting)
 Relative number of cells forming the gland
 unicellular
 multicellular
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Endocrine Glands
 Ductless glands that produce hormones.
 Release of hormones is via exocytosis
 Secretions include amino acids, proteins,
glycoproteins, and steroids.
 Endocrine glands vary in shape, size and structure.
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Exocrine Glands
 More numerous than endocrine glands
 Secrete their products onto body surfaces (skin) or
into body cavities
 Examples include mucous, sweat, oil, and salivary
glands
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Unicellular Exocrine Gland
 The only important unicellular gland is the goblet
cell.
 These single celled glands line our digestive,
respiratory and intestinal tract.
 They sit in between the columnar cells.
 They produce mucin which breaks down in water to
form mucus.
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Multicellular Exocrine glands
 Multicellular exocrine glands are composed of a
duct and secretory unit.
 Supportive Connective Tissue surrounds the gland
and supplies it with blood vessels and nerve fibers.
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Multicellular Exocrine Glands
 Classified according to structure:
 Simple or compound duct type
 Tubular, alvelar or tubuloaveolar
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Structural Classification of Multicellular
Exocrine Glands
Figure 4.3a-d
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Structural Classification of Multicellular
Exocrine Glands
Figure 4.3e-g
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Modes of Secretion
 Multicellular glands secrete the chemical in different
ways.
 Exocytosis: this type of gland is called a merocrine
gland.
 Rupture: this type of gland has the cells fill with the
chemical and then the whole cell ruptures. This type
of gland is called holocrine gland.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings