4
Tissue: The Living Fabric
Part A
Tissues
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Groups of cells similar in structure and function
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The four types of tissues
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Epithelial
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Connective
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Muscle
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Nerve
Epithelial Tissue
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Cellularity composed almost entirely of cells
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Special contacts form continuous sheets held together
by tight junctions and desmosomes
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Polarity apical and basal surfaces
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Supported by connective tissue reticular and basal
laminae
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Avascular but innervated contains no blood vessels
but supplied by nerve fibers
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Regenerative rapidly replaces lost cells by cell
division
Classification of Epithelia
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Simple or stratified
Classification of Epithelia
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Squamous, cuboidal, or columnar
Epithelia: Simple Squamous
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Single layer of flattened cells with disc-shaped nuclei
and sparse cytoplasm
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Functions
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Diffusion and filtration
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Provide a slick, friction-reducing lining in lymphatic
and cardiovascular systems
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Present in the kidney glomeruli, lining of heart, blood
vessels, lymphatic vessels, and serosae
Epithelia: Simple Squamous
Epithelia: Simple Cuboidal
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Single layer of cubelike cells with large, spherical
central nuclei
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Function in secretion and absorption
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Present in kidney tubules, ducts and secretory portions
of small glands, and ovary surface
Epithelia: Simple Cuboidal
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Single layer of cubelike cells with large, spherical
central nuclei
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Function in secretion and absorption
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Present in kidney tubules, ducts and secretory portions
of small glands, and ovary surface
Epithelia: Simple Columnar
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Single layer of tall cells with oval nuclei; many
contain cilia
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Goblet cells are often found in this layer
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Function in absorption and secretion
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Nonciliated type line digestive tract and gallbladder
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Ciliated type line small bronchi, uterine tubes, and
some regions of the uterus
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Cilia help move substances through internal passageways
Epithelia: Simple Columnar
Epithelia: Pseudostratified Columnar
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Single layer of cells with different heights; some do
not reach the free surface
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Nuclei are seen at different layers
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Function in secretion and propulsion of mucus
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Present in the male sperm-carrying ducts (nonciliated)
and trachea (ciliated)
Epithelia: Pseudostratified Columnar
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Single layer of cells with different heights; some do
not reach the free surface
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Nuclei are seen at different layers
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Function in secretion and propulsion of mucus
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Present in the male sperm-carrying ducts (nonciliated)
and trachea (ciliated)
Epithelia: Stratified Squamous
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Thick membrane composed of several layers of cells
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Function in protection of underlying areas subjected to
abrasion
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Forms the external part of the skins epidermis
(keratinized cells), and linings of the esophagus, mouth, and vagina
(nonkeratinized cells)
Epithelia: Stratified Squamous
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Thick membrane composed of several layers of cells
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Function in protection of underlying areas subjected to
abrasion
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Forms the external part of the skins epidermis
(keratinized cells), and linings of the esophagus, mouth, and vagina
(nonkeratinized cells)
Epithelia: Stratified Cuboidal and Columnar
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Stratified cuboidal
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Quite rare in the body
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Found in some sweat and
mammary glands
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Typically two cell
layers thick
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Stratified columnar
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Limited distribution in
the body
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Found in the pharynx,
male urethra, and lining some glandular ducts
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Also occurs at
transition areas between two other types of epithelia
Epithelia: Transitional
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Several cell layers, basal cells are cuboidal, surface
cells are dome shaped
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Stretches to permit the distension of the urinary
bladder
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Lines the urinary bladder, ureters, and part of the
urethra
Epithelia: Transitional
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Several cell layers, basal cells are cuboidal, surface
cells are dome shaped
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Stretches to permit the distension of the urinary
bladder
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Lines the urinary bladder, ureters, and part of the
urethra
Epithelia: Glandular
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A gland is one or more cells that makes and secretes an
aqueous fluid
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Classified by:
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Site of product release endocrine or exocrine
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Relative number of cells forming the gland
unicellular or multicellular
Endocrine Glands
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Ductless glands that produce hormones
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Secretions include amino acids, proteins,
glycoproteins, and steroids
Exocrine Glands
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More numerous than endocrine glands
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Secrete their products onto body surfaces (skin) or
into body cavities
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Examples include mucous, sweat, oil, and salivary
glands
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The only important unicellular gland is the goblet cell
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Multicellular exocrine glands are composed of a duct
and secretory unit
Multicellular Exocrine Glands
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Classified according to:
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Simple or compound duct type
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Structure of their secretory units
Structural Classification of Multicellular Exocrine Glands
4
Tissue: The Living Fabric
Part B
Modes of Secretion
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Merocrine products are secreted by exocytosis (e.g.,
pancreas, sweat, and salivary glands)
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Holocrine products are secreted by the rupture of
gland cells (e.g., sebaceous glands)
Modes of Secretion
Connective Tissue
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Found throughout the body; most abundant and widely
distributed in primary tissues
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Connective tissue proper
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Cartilage
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Bone
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Blood
Connective Tissue
Functions of Connective Tissue
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Binding and support
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Protection
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Insulation
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Transportation
Characteristics of Connective Tissue
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Connective tissues have:
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Mesenchyme as their common tissue of origin
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Varying degrees of vascularity
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Nonliving extracellular matrix, consisting of ground
substance and fibers
Structural Elements of Connective Tissue
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Ground substance unstructured material that fills the
space between cells
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Fibers collagen, elastic, or reticular
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Cells fibroblasts, chondroblasts, osteoblasts, and
hematopoietic stem cells
Ground Substance
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Interstitial (tissue) fluid
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Adhesion proteins fibronectin and laminin
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Proteoglycans glycosaminoglycans (GAGs)
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Functions as a molecular sieve through which nutrients
diffuse between blood capillaries and cells
Ground Substance: Proteoglycan Structure
Fibers
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Collagen tough; provides high tensile strength
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Elastic long, thin fibers that allow for stretch
§ Reticular
branched collagenous fibers that form delicate networks
Cells
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Fibroblasts connective tissue proper
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Chondroblasts cartilage
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Osteoblasts bone
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Hematopoietic stem cells blood
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White blood cells, plasma cells, macrophages, and mast
cells
Connective Tissue: Embryonic
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Mesenchyme embryonic connective tissue
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Gel-like ground substance with fibers and star-shaped
mesenchymal cells
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Gives rise to all other connective tissues
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Found in the embryo
Connective Tissue: Embryonic
Connective Tissue Proper: Loose
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Areolar connective tissue
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Gel-like matrix with all three connective tissue fibers
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Fibroblasts, macrophages, mast cells, and some white
blood cells
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Wraps and cushions organs
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Widely distributed throughout the body
Connective Tissue Proper: Loose
Connective Tissue Proper: Loose
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Adipose connective tissue
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Matrix similar to areolar connective tissue with
closely packed adipocytes
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Reserves food stores, insulates against heat loss, and
supports and protects
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Found under skin, around kidneys, within abdomen, and
in breasts
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Local fat deposits serve nutrient needs of highly
active organs
Connective Tissue Proper: Loose
Connective Tissue Proper: Loose
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Reticular connective tissue
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Loose ground substance with reticular fibers
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Reticular cells lie in a fiber network
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Forms a soft internal skeleton, or stroma, that
supports other cell types
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Found in lymph nodes, bone marrow, and the spleen
Connective Tissue Proper: Loose
Connective Tissue Proper: Dense Regular
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Parallel collagen fibers with a few elastic fibers
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Major cell type is fibroblasts
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Attaches muscles to bone or to other muscles, and bone
to bone
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Found in tendons, ligaments, and aponeuroses
Connective Tissue Proper: Dense Regular
Connective Tissue Proper: Dense Irregular
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Irregularly arranged collagen fibers with some elastic
fibers
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Major cell type is fibroblasts
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Withstands tension in many directions providing
structural strength
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Found in the dermis, submucosa of the digestive tract,
and fibrous organ capsules
Connective Tissue Proper: Dense Regular
4
Tissue: The Living Fabric
Part C
Connective Tissue: Cartilage
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Hyaline cartilage
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Amorphous, firm matrix with imperceptible network of
collagen fibers
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Chondrocytes lie in lacunae
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Supports, reinforces, cushions, and resists compression
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Forms the costal cartilage
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Found in embryonic skeleton, the end of long bones,
nose, trachea, and larynx
Connective Tissue: Hyaline Cartilage
Connective Tissue: Elastic Cartilage
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Similar to hyaline cartilage but with more elastic
fibers
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Maintains shape and structure while allowing
flexibility
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Supports external ear (pinna) and the epiglottis
Connective Tissue: Elastic Cartilage
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Similar to hyaline cartilage but with more elastic
fibers
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Maintains shape and structure while allowing
flexibility
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Supports external ear (pinna) and the epiglottis
Connective Tissue: Fibrocartilage Cartilage
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Matrix similar to hyaline cartilage but less firm with
thick collagen fibers
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Provides tensile strength and absorbs compression shock
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Found in intervertebral discs, the pubic symphysis, and
in discs of the knee joint
Connective Tissue: Fibrocartilage Cartilage
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Matrix similar to hyaline cartilage but less firm with
thick collagen fibers
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Provides tensile strength and absorbs compression shock
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Found in intervertebral discs, the pubic symphysis, and
in discs of the knee joint
Connective Tissue: Bone (Osseous Tissue)
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Hard, calcified matrix with collagen fibers found in
bone
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Osteocytes are found in lacunae and are well
vascularized
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Supports, protects, and provides levers for muscular
action
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Stores calcium, minerals, and fat
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Marrow inside bones is the site of hematopoiesis
Connective Tissue: Bone (Osseous Tissue)
Connective Tissue: Blood
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Red and white cells in a fluid matrix (plasma)
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Contained within blood vessels
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Functions in the transport of respiratory gases,
nutrients, and wastes
Connective Tissue: Blood
Epithelial Membranes
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Cutaneous skin
Epithelial Membranes
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Mucous lines body cavities open to the exterior
(e.g., digestive and respiratory tracts)
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Serous moist membranes found in closed ventral body
cavity
Epithelial Membranes
4
Tissue: The Living Fabric
Part D
Nervous Tissue
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Branched neurons with long cellular processes and
support cells
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Transmits electrical signals from sensory receptors to
effectors
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Found in the brain, spinal cord, and peripheral nerves
Nervous Tissue
Muscle Tissue: Skeletal
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Long, cylindrical, multinucleate cells with obvious
striations
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Initiates and controls voluntary movement
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Found in skeletal muscles that attach to bones or skin
Muscle Tissue: Skeletal
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Long, cylindrical, multinucleate cells with obvious
striations
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Initiates and controls voluntary movement
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Found in skeletal muscles that attach to bones or skin
Muscle Tissue: Cardiac
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Branching, striated, uninucleate cells interlocking at
intercalated discs
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Propels blood into the circulation
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Found in the walls of the heart
Muscle Tissue: Cardiac
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Branching, striated, uninucleate cells interdigitating
at intercalated discs
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Propels blood into the circulation
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Found in the walls of the heart
Muscle Tissue: Smooth
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Sheets of spindle-shaped cells with central nuclei that
have no striations
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Propels substances along internal passageways (i.e.,
peristalsis)
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Found in the walls of hollow organs
Muscle Tissue: Smooth
Tissue Trauma
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Causes inflammation, characterized by:
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Dilation of blood vessels
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Increase in vessel permeability
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Redness, heat, swelling, and pain
Tissue Repair
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Organization and restored blood supply
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The blood clot is replaced with granulation tissue
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Regeneration and fibrosis
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Surface epithelium regenerates and the scab detaches
Tissue Repair
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Fibrous tissue matures and begins to resemble the
adjacent tissue
Tissue Repair
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Results in a fully regenerated epithelium with
underlying scar tissue
Developmental Aspects
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Primary germ layers: ectoderm, mesoderm, and endoderm
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Three layers of cells formed early in embryonic
development
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Specialize to form the four primary tissues
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Nerve tissue arises from ectoderm
Developmental Aspects
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Muscle, connective tissue, endothelium, and mesothelium
arise from mesoderm
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Most mucosae arise from endoderm
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Epithelial tissues arise from all three germ layers
Developmental Aspects