Tissues Tissues are layers or groups of similar cells with a
common function 4 types of tissues include: Epithelial Connective
Muscle Nervous
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Epithelial Tissue Epithelial tissue covers all free body
surfaces, forms the inner lining of body cavities, lines hollow
organs, and is the major tissue of glands. A basement membrane
anchors epithelium to connective tissue. Epithelial tissue lacks
blood vessels, has cells that are tightly packed, and is
continuously replaced. It functions in protection, secretion,
absorption, and excretion.
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Epithelial Tissue Apical Surface A free surface or edge exposed
to the bodys exterior or to the cavity/lumen of an internal organ.
Basal Surface Basement membrane Lower surface of epithelium
Structureless material secreted by the cells.
Simple Squamous Epithelial This tissue consists of a single
layer of thin, flattened cells through which substances pass
easily. It functions in the exchange of gases in the lungs and
lines blood vessels, lymph vessels, and membranes within the thorax
and abdomen.
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Simple Cuboidal Epithelium This tissue consists of a single
layer of cube shaped cells. It carries on secretion and absorption
in the kidneys and various glands.
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Simple Columnar Epithelium This tissue is composed of elongated
cells whose nuclei are near the basement membrane. It lines the
uterus and digestive tract, where it functions in protection,
secretion and absorption.
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Pseudostratified Columnar This tissue appears stratified
because the nuclei are at two or more levels. Its cells may have
cilia that move mucus over the surface of the tissue. It lines
tubes if the respiratory system.
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Stratified Squamous Epithelium This tissue is composed of many
layers of cells; the top layers are flattened. It protects
underlying cells from harmful environmental effects. It covers the
skin and lines the oral cavity, esophagus, vagina and anal
canal.
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Stratified Cuboidal Epithelium This tissue is composed of two
or three layers of cube- shaped cells. It lines the larger ducts of
the sweat gland, salivary glands and pancreas. It functions in
protection.
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Stratified Columnar Epithelium The top layer of cells in this
tissue contains elongated columns. Cube-shaped cells make up the
bottom layers. It is in part of the male urethra and parts of the
pharynx Functions in protection and secretion.
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Transitional Epithelium Specialized to become distended. It is
in the walls of organs of the urinary tract. It helps prevent the
contents of the urinary passageways from diffusing out.
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Connective Tissue Connects, supports, protects, fills spaces,
stores fat, produces blood cells, protects against infections, and
helps repair damage tissues Most are well vascularized except
tendons, ligaments and cartilage Fibersmade by CT cells and
secreted Collagen fibers (white) Elastic fibers (yellow) Reticular
fibers (fine collagen)
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Types of Connective tissue From most rigid to softest: Bone
Cartilage Dense connective tissue Loose connective tissue
Blood
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Major Cell types Fibroblasts produce collagenous and elastic
fibers Macrophages are phagocytes Mass cells release heparin and
histamine and usually are near blood vessels
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Bone The extracellular matrix of bone contains mineral salts
and collagen Its cells usually form concentric circles around
osteonic canals Active tissue that heals rapidly Osseus tissue Most
rigid connective tissue, with deposits of mineral salts and
collagen within the matrix. Bone cells, called osteocytes, lie
within lacunae and are arranged in concentric circles Good blood
supply, enabling rapid recovery after an injury. Rocklike hardness
allows protection and support of other body organs
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Cartilage Provides a supportive framework for various
structures. Cartilage cells (chondrocytes) lie within lacunae in
the gel-like fluid matrix.
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Types of Cartilage Hyaline cartilage is white with abundant
fine collagen fibers, is found at the ends of bones, and supports
respiratory passages. Elastic cartilage, with elastic fibers,
provides a framework for the external ears and parts of the larynx.
Fibrocartilage is a tough tissue that provides a shock-absorbing
function in intervertebral disks and in the knees and pelvic
girdle.
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Dense Connective Tissue This tissue consists of densely packed
collagenous fibers and is very strong but lacks a good blood
supply. Fibroblastscells that make fibers It is found as part of
tendons and ligaments.
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Loose Connective Tissue This type of tissue forms delicate,
thin membranes throughout the body that bind body parts together.
Fibroblasts are separated by a gel-like ground substance that
contains collagenous and elastic fibers. It binds the skin to
underlying organs and fills spaces within muscle.
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Areolar Tissue Most widely distributed connective tissue in the
body Cusions and protects body organs it wraps Glue that holds
internal organs together
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Adipose Tissue Fat storing connective tissue Found beneath the
skin (insulates the body), around joints, padding the kidneys and
other internal organs, and in certain abdominal membranes.
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Reticular Connective Tissue Network of interwoven reticular
fibers associated with reticular cells Internal supporting
framework
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Blood Blood is composed of cells (red and white) suspended in a
fluid matrix (plasma). It is formed in the blood-forming tissues
inside red bone marrow and functions to transport substances
throughout the body.
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The Integumentary System The skin and its accessory structures
make up the integumentary system. Five major functions Serving as a
barrier against infection and disease Helping to regulate body
temperature Removing waste products from the body Providing
protection against Ultraviolet radiation from the sun Producing
vitamin D
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Epidermis Dermis Subcutaneous layer beneath dermis not part of
skin Layers of Skin
Epidermis Layer of stratified squamos epithelium that lacks
blood vessels Thickest on Palms Keratonized Outermost Layer Its
layers are made of Mostly DEAD CELLS. Most of the cells of the
epidermis undergo rapid cell division (MITOSIS). As new cells are
produced, they push older cells to the surface of the skin. The
older cells become flattened, lose their cellular contents and
begin making KERATIN.
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Dermis Composed of irregular dense connective tissue that binds
the epidermis to underlying layer Contains blood vessels Nerve
tissue is scattered through the dermis