Transcript Chapter 3 Body Tissues

Chapter 3 Body Tissues
• Tissues
– Groups of cells with similar structure and function
– Four primary types:
1.
2.
3.
4.
Epithelial tissue (epithelium)
Connective tissue
Muscle tissue
Nervous tissue
© 2015 Pearson Education, Inc.
Epithelial Tissues
• Locations:
– Body coverings
– Body linings
– Glandular tissue
• Functions:
–
–
–
–
Protection
Absorption
Filtration
Secretion
© 2015 Pearson Education, Inc.
Epithelium Characteristics
• Cells fit closely together and often form sheets
• The apical surface is the free surface of the tissue
– The unattached surface
• Can be exposed to exterior or cavity of an organ
• The lower surface of the epithelium (the basal
lamina) rests on a basement membrane
– Consists of reticular connective tissue
© 2015 Pearson Education, Inc.
Epithelium Characteristics
• Avascular (no blood supply)
– Relies on circulatory system to obtain food and
oxygen
• Surrounding connective tissues supply via diffusion
from nearby capillaries
• Regenerate easily if well nourished (through
normal cell division)
– Those on the exterior of the skin are exposed to friction
and other hostile substances and are therefore lost
Classification of Epithelia
• Two name system:
– First name = # of layers
– Second name = shape of cells
• Names using number of cell layers include:
– Simple—one layer
– Stratified—more than one layer
© 2015 Pearson Education, Inc.
Figure 3.17a Classification and functions of epithelia.
Apical surface
Basal
surface
Simple
Apical surface
Basal
surface Stratified
(a) Classification based on number of cell layers
Classification of Epithelia
• Names using shape of cells
– Squamous
• Flattened, like fish scales
– Cuboidal
• Cube-shaped, like dice
– Columnar
• Column-like
© 2015 Pearson Education, Inc.
Figure 3.17b Classification and functions of epithelia.
Squamous
Cuboidal
Columnar
(b) Classification based on cell shape
Figure 3.17c Classification and functions of epithelia.
Number of layers
One layer: simple epithelial
tissues
More than one layer: stratified
epithelial tissues
Squamous
Diffusion and filtration
Secretion in serous membranes
Protection
Cuboidal
Secretion and absorption; ciliated
types propel mucus or
reproductive cells
Secretion and absorption; ciliated
types propel mucus or
reproductive cells
Protection; these tissue types are rare
in humans
Cell shape
Columnar
Transitional
Protection; stretching to accommodate
distension of urinary structures
(c) Function of epithelial tissue related to tissue type
• Remember these general characteristics and you
will be able to classify each type a lot easier !!
Simple Epithelia
• Simple squamous
– Single layer of flat cells
– Location—usually forms membranes
• Lines air sacs of the lungs
• Forms walls of capillaries
• Forms serous membranes (serosae) that line and cover
organs in ventral cavity
– Functions in diffusion, filtration, or secretion in
membranes
© 2015 Pearson Education, Inc.
Figure 3.18a Types of epithelia and their common locations in the body.
Air sacs of
lungs
Nucleus of
squamous
epithelial cell
Basement
membrane
(a) Diagram: Simple squamous
Nuclei of
squamous
epithelial
cells
Photomicrograph: Simple
squamous epithelium forming part
of the alveolar (air sac) walls (275×).
Simple Epithelia
• Simple cuboidal
– Single layer of cube-like cells
– Locations:
• Common in glands and their ducts
• Forms walls of kidney tubules
• Covers the surface of ovaries
– Functions in secretion and absorption; ciliated
types propel mucus or reproductive cells
© 2015 Pearson Education, Inc.
Figure 3.18b Types of epithelia and their common locations in the body.
Nucleus of
simple
cuboidal
epithelial
cell
Basement
membrane
(b) Diagram: Simple cuboidal
Simple
cuboidal
epithelial
cells
Basement
membrane
Connective
tissue
Photomicrograph: Simple cuboidal
epithelium in kidney tubules (250×).
Simple Epithelia
• Simple columnar
– Single layer of tall cells
• Goblet cells secrete mucus
– Location:
• Lines digestive tract from stomach to anus
• Mucous membranes (mucosae) line body cavities
opening to the exterior
– Functions in secretion and absorption; ciliated
types propel mucus or reproductive cells
© 2015 Pearson Education, Inc.
Figure 3.18c Types of epithelia and their common locations in the body.
Nucleus of
simple columnar
epithelial cell
Basement
membrane
(c) Diagram: Simple columnar
Mucus of a
goblet cell
Simple
columnar
epithelial cells
Basement
membrane
Photomicrograph: Simple columnar
epithelium of the small intestine (575×).
Simple Epithelia
• Pseudostratified columnar
– All cells rest on a basement membrane
– Single layer, but some cells are shorter than others
giving a false (pseudo) impression of stratification
– Location:
• Respiratory tract, where it is ciliated and known as
pseudostratified ciliated columnar epithelium
– Functions in absorption or secretion
© 2015 Pearson Education, Inc.
Figure 3.18d Types of epithelia and their common locations in the body.
Cilia
Pseudostratified
epithelial
layer
Pseudostratified
epithelial layer
Basement
membrane
Basement
membrane
Connective
tissue
(d) Diagram: Pseudostratified
(ciliated) columnar
Photomicrograph: Pseudostratified
ciliated columnar epithelium lining the
human trachea (560×).
Stratified Epithelia
(two or more cell layers)
• Stratified squamous
– Named for cells present at the free (apical)
surface, which are flattened
– Functions as a protective covering where friction
is common
– Locations—lining of the:
• Skin (outer portion)
• Mouth
• Esophagus
© 2015 Pearson Education, Inc.
Figure 3.18e Types of epithelia and their common locations in the body.
Nuclei
Stratified
squamous
epithelium
Basement
membrane
(e) Diagram: Stratified squamous
Stratified
squamous
epithelium
Basement
membrane
Connective
Photomicrograph:
tissue
Stratified squamous
epithelium lining of the esophagus (140×).
Stratified Epithelia
• Stratified cuboidal—two layers of cuboidal
cells; functions in protection
• Stratified columnar—surface cells are
columnar, and cells underneath vary in size
and shape; functions in protection
• Stratified cuboidal and columnar
– Rare in human body
– Found mainly in ducts of large glands
© 2015 Pearson Education, Inc.
Stratified Epithelia
• Transitional epithelium
– Unique type of epithelium because of its ability to
become temporarily modified in arrangement and
shape
– Composed of modified stratified squamous epithelium
– Shape of cells depends upon the amount of stretching
– Functions in stretching and the ability to return to
normal shape
– Locations: urinary system organs
© 2015 Pearson Education, Inc.
Figure 3.18f Types of epithelia and their common locations in the body.
Basement
membrane
Transitional
epithelium
Basement
membrane
Transitional
epithelium
Connective
tissue
(f) Diagram: Transitional
Photomicrograph: Transitional epithelium lining of
the bladder, relaxed state (270×); surface rounded cells
flatten and elongate when the bladder fills with urine.
Glandular Epithelium
• Gland
– One or more cells responsible for secreting a
particular product
– Secretions contain protein molecules in an
aqueous (water-based) fluid
– Secretion is an active process
© 2015 Pearson Education, Inc.
Glandular Epithelium
• Two major gland types
– Endocrine gland
• Ductless; secretions diffuse into blood vessels
• All secretions are hormones
• Examples include thyroid, adrenals, and pituitary
© 2015 Pearson Education, Inc.
Glandular Epithelium
• Two major gland types
– Exocrine gland
• Secretions empty through ducts to the epithelial
surface
• Include sweat and oil glands, liver, and pancreas
• Includes both internal and external glands
© 2015 Pearson Education, Inc.