~NRe
Epithelial tissue or epithelium is a sheet of cells that covers a body surface or lines a
body cavity
. Two
forms occur in the
body :
covering and
lining epithelium which forms the outer layer of the skin , dips and lines the open
cavities of the urogenital digestive
, ,
and
respiratory system ,
and covers the walls and
organs of the close
ventral body cavity
.
Glandular and epithelium which fashions the glands of the body
Functions of epithelium
) protection 2) absorption 3) filtration
& 4) excretion 5) secretion 6) sensory reception
Special Characteristics of Epithelium
Apical surface not attached to surrounding tissue and is exposed to either the outside of the body
or the cavity of an internal organ
.
BasalSurface is attached to the underlying connective issue
Microvilli fingerlike extensions of the membrane
plasma
Cilia tiny hair like , projections of a cell that propel substances along their free surface .
Basal lamina adjacent to the basal surface of an epithelium is a thin
supporting sheet .
Specialized
Contacts
The sides of adjacent cells are tied together by tightjunctions and desmosomes .
Supported by Connective Tissue
Basement Membrane between the epithelial and connective tissue
Reticular Lamina is deep to the the basal lamina It consist of
. a layer of extracellular material a fine
network of collagen fibers that "belong to "the underlying connective tissue
.
Avascular but innervated
epithelium is avascular (no blood vessels) it is innervated (supplied by nerve fibers). Epithelial cells nourishe
by substances diffusing from blood vessels in the underlying connective tissue
Regeneration
Epithelium has a
. Some epithelia
high regenerative energy are
exposed to friction and their surface cells ru
Off .
Epithelial tissue or epithelium is a sheet of cells that covers a body surface or lines a
body cavity
. Two
forms occur in the
body :
covering and
lining epithelium which forms the outer layer of the skin , dips and lines the open
cavities of the urogenital digestive
, ,
and
respiratory system ,
and covers the walls and
organs of the close
ventral body cavity
.
Glandular and epithelium which fashions the glands of the body
Functions of epithelium
) protection 2) absorption 3) filtration
& 4) excretion 5) secretion 6) sensory reception
Special Characteristics of Epithelium
Apical surface not attached to surrounding tissue and is exposed to either the outside of the body
or the cavity of an internal organ
.
BasalSurface is attached to the underlying connective issue
Microvilli fingerlike extensions of the membrane
plasma
Cilia tiny hair like , projections of a cell that propel substances along their free surface .
Basal lamina adjacent to the basal surface of an epithelium is a thin
supporting sheet .
Specialized
Contacts
The sides of adjacent cells are tied together by tightjunctions and desmosomes .
Supported by Connective Tissue
Basement Membrane between the epithelial and connective tissue
Reticular Lamina is deep to the the basal lamina It consist of
. a layer of extracellular material a fine
network of collagen fibers that "belong to "the underlying connective tissue
.
Avascular but innervated
epithelium is avascular (no blood vessels) it is innervated (supplied by nerve fibers). Epithelial cells nourishe
by substances diffusing from blood vessels in the underlying connective tissue
Regeneration
Epithelium has a
. Some epithelia
high regenerative energy are
exposed to friction and their surface cells ru
Off .
