March 30th
• Text: Chapter 4
• Video: Intro. to Tissues
• Tissues: Part 1: Epithelial Tissue
• Histology Tutor
• Begin Lab 13: Tissues Slides 1-8
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Tissue: The Living Fabric PART 1
Tissues
 Groups of cells similar in structure and function
 The four types of tissues
 Epithelial (covering)
 Connective (support)
 Muscle (movement)
 Nerve (control)
Overview of Tissues
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Preparing Human Tissue for Microscopy
 Steps
 Specimens must be fixed (preserved)
 Sectioned
 Stained to enhance contrast
Overview of Four Tissue Types
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Epithelial Tissue
 List several structural and functional characteristics
of epithelial tissue
 Name, classify and describe the various types of
epithelial tissue and show their chief functions and
locations
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Epithelial Tissue
 Sheets of cells that cover a body surface or line a
body cavity
 Occurs in the body as
 Covering or lining epithelium
 Glandular epithelium
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6 Functions of Epithelial Tissue
1 Protection
2 Absorption
3 Filtration
4 Excretion
5 Secretion
6 Sensory Reception
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Epithelial Tissue Characteristics
1 Cellularity – composed almost entirely of cells
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 and
basal laminae
5 Avascular but innervated – contains no blood
vessels but supplied by nerve fibers
6 Regenerative – rapidly replaces lost cells by cell
division
Classification of Epithelia
 Simple or
stratified
Figure 4.1a
Simple vs. Stratified
 Simple
 One cell layer
 Found where absorption, secretion, filtration occur
 Stratified
 Two or more cell layers
 Found where protection is important
 (Skin surface, lining of the mouth)
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Apical surface
Basal surface
Connective tissue
Classification of Epithelia
 Squamous, cuboidal,
or columnar
Figure 4.1b
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
Epithelia: Simple Squamous
Figure 4.2a
Simple Squamous Epithelium
Flattened laterally, cytoplasm is sparse
2 Special Types of Simple Squamous Epithelium
 Endothelium: lining of lymphatic vessels and
hollow organs of cardiovascular system
 Mesothelium: lining ventral body cavity organs
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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
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
Cubodial Epithelium
Human kidney tubule section showing cuboidal epithelium. LM X360.
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
Epithelia: Simple Columnar
Figure 4.2c
Columnar Epithelium
Human columnar epithelium lining the bronchus of the lung. H&E stain. X180.
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)
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
Pseudostratified Columnar
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)
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
Keratinized Epithelium
Stratified squamous epithelium from mouth mucosa. H&E stain. LM X100.
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
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
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
Transitional Epithelium;
Distended
Transitional Epithelium;
Collapsed
Check Your Understanding
1 What is the purpose for fixing tissues for
microscope viewing?
2 What types of stains are used to stain tissues to be
viewed with an electron microscope ?
3 Epithelial tissue has polarity (an apical and basal
surface). Why is this important ?
4 Which of these properties apply to epithelial
tissue? Has blood vessels, can repair itself, cells
joined by lateral contacts ?
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Check Your Understanding
5 Stratified epithelia are built for protection and to
resist abrasion. What are the simple epithelia
better at ?
6 What is meant by “pseudostratified” epiphelia ?
7 Where is transitional epithelium found and why is
it important at those sites ?
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Label the following Epithelial Tissue Types
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Quiz!!
E
Can You Identify the
Classes of Epithelium?
D
A
B
C