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DIFFERENTIATION Differentiation is the process by which an unspecialized
cell (such as a fertilized egg cell), divides many times to produce specialized cells that work together and make up the body.
Every cell in the body was originated from a single fertilized egg, the zygote, that divides many times to produce an embryo.
Embryonic cells differentiate into many different cell types (250), from a new-born baby to an elderly adult.
A differentiated cell will develop specific structures and perform certain functions.
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Body Tissues Tissues
Groups of cells with similar structure and function
Four primary types Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Body Tissues Tissues
Groups of cells with similar structure and function
Four primary types Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue
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Epithelial Tissues Locations
Body coverings Glandular tissue
Functions Protection Absorption Filtration Secretion
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Epithelium Characteristics
Cells fit closely together and often form sheets
Regenerate easily if well nourished
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Epithelium Characteristics
Figure 3.17a
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Classification of Epithelia
Number of cell layers Simple—one layer Stratified—more
than one layer
Figure 3.17a
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Classification of Epithelia Shape of cells
Squamous flattened
Cuboidal cube-
shaped Columnar
column-likeFigure 3.17b
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Simple Epithelia Simple squamous
Single layer of flat cells (much wider than they are thick).
(The thinnest tissue of the body). Usually forms membranes
Lines body cavities, lungs and capillaries
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Simple Squamous Epithelia
Figure 3.18a
Allows transport across membranes in lungs and capillaries, secretes fluid in serous membranes (pericardial and pleural), covers organs…
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Simple Epithelia Simple cuboidal
Single layer of cube-like cells Common in exocrine glands and their ducts Forms walls of kidney tubules and covers the
ovaries
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Simple Cuboidal Epithelia
Figure 3.18b
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Simple Epithelia Simple columnar
Single layer of tall cells Often includes mucus-producing goblet cells
or microvilli at surface for absortion. Lines digestive tract.
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Simple Columnar Epithelia
Figure 3.18c
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Simple Epithelia Pseudostratified columnar
Single layer, but some cells are shorter than others. It often looks like a double layer of cells
Sometimes ciliated, such as in the respiratory tract
May function in absorption or secretion
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Simple Pseudostratified Epithelia
Figure 3.18d
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Stratified Epithelia Stratified squamous
Cells at the apical surface are flattened Found as a protective covering where friction
is common Locations
Skin Mouth Esophagus
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Stratified Squamous Epithelia
Figure 3.18e
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Glandular Epithelium Gland
One or more cells responsible for secreting a particular product
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Glandular Epithelium Two major gland types
Endocrine gland Ductless secretions diffuse into blood
vessels All secretions are hormones
Exocrine gland Secretions empty through ducts to the
epithelial surface Include sweat and oil glands
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Body Tissues Tissues
Groups of cells with similar structure and function
Four primary types Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue
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Connective Tissue Found everywhere in the body Functions
Binds body tissues together Supports the body Provides protection
Cells widely separated from each other in a matrix. Extracellular matrix: Non-living material that
surrounds living cells and is produced by them.
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Extracellular Matrix Two main elements
Ground substance (mostly water with proteins and polysaccharides)
Fibers Produced by the cells Three types
Collagen (white) fibers Elastic (yellow) fibers Reticular fibers
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Connective Tissue Types Bone (osseous tissue) Cartilage Dense connective tissue Loose (Areaolar) Connective Tissue:
Areaolar Adipose Reticular
Blood
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Connective Tissue Types Bone (osseous tissue)
Composed of Bone cells (osteocytes) in lacunae
(cavities) Hard matrix of calcium salts
Used to protect and support the body
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Connective Tissue Types
Figure 3.19a
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Connective Tissue Types Cartilage
Composed of Abundant collagen fibers and elastic
fibers Rubbery matrix Chondrocytes
Locations Larynx, fetal skeleton, cushion-like discs
between vertebrae, bronchi, nose, ears…
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Connective Tissue Types
Figure 3.19b
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Connective Tissue Types Dense connective tissue (dense fibrous tissue)
Main matrix element is collagen fiber Locations
Tendons—attach skeletal muscle to bone Ligaments—attach bone to bone at joints Dermis—lower layers of the skin
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Connective Tissue Types
Figure 3.19d
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Connective Tissue Types Loose connective tissue types
Adipose tissue Matrix is an areolar tissue in which fat
globules predominate Many cells (adipocytes) contain large lipid
deposits Functions
Insulates the body Protects some organs Serves as a site of fuel storage
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Connective Tissue Types
Figure 3.19f
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Connective Tissue Types Blood (vascular tissue)
Blood cells surrounded by fluid matrix called blood plasma
Fibers are visible during clotting Functions as the transport vehicle for
materials Formed elements– ErythrocytesErythrocytes –red blood cells– LeukocytesLeukocytes –white blood cells– PlateletsPlatelets -blood clotting
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Connective Tissue Types
Figure 3.19h
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Body Tissues Tissues
Groups of cells with similar structure and function
Four primary types Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue
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Muscle Tissue Function is to produce movement Three types
Skeletal muscle Cardiac muscle Smooth muscle
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Muscle Tissue Types Skeletal muscle
Under voluntary control Contracts to pull on bones or skin Produces gross body movements or facial
expressions Characteristics of skeletal muscle cells
Striated Multinucleate (more than one nucleus) Long, cylindrical (each cell is the length of
the muscle)
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Muscle Tissue Types
Figure 3.20a
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Muscle Tissue Types Cardiac muscle
Under involuntary control Found only in the heart Function is to pump blood Characteristics of cardiac muscle cells
Cells are attached to other cardiac muscle cells at intercalated disks
Striated One nucleus per cell
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Muscle Tissue Types
Figure 3.20b
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Muscle Tissue Types Smooth muscle
Under involuntary muscle Found in walls of hollow organs such as
stomach, uterus, and blood vessels Characteristics of smooth muscle cells
No visible striations One nucleus per cell Spindle-shaped cells
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Muscle Tissue Types
Figure 3.20c
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Body Tissues Tissues
Groups of cells with similar structure and function
Four primary types Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue
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Nervous Tissue Composed of neurons and nerve support cells Sends impulses to other areas of the body Irritability Conductivity Neurons and glial cells