HLSC120 – Human Anatomy
Chapter 3: Tissues
Tissues – groups of similar cells and extracellular products that carry out a common
function (i.e. providing protection, facilitating body movement)
Histology – study of tissues and their relationships within organs
4 PRINCIPAL TYPES OF TISSUES
epithelial, muscle, nervous, connective;+ vary in the structure of their specialized
cells and the functions of these cells and the presence of an extracellular matrix that
surrounds the cells and is produced by them
Matrix – womb; composed of varying amounts of protein fibers, water, and
dissolved macromolecules; consistency ranges from fluid to quite solid (i.e. o o Cellularity – cells of an epithelium are bound closely together by diff. types
epithelial, muscle, and nervous tissues have little matrix b/w cells; connective tissue of cell junctions; composed almost entirety of cells
contains varying amounts of extracellular matrix) o Polarity – every epithelium has an apical surface and a basal surface
EPITHELIAL TISSUE apical surface – free or top surface; exposed to the external environment
lines every body surface and all body cavities; forms both the external and internal basal surface – fixed or bottom surface; where the epithelium is attached
lining of many organs; constitutes the majority of glands to the underlying connective tissue
Epithelium – composed of one or more layers of closely packed cells that form a o Attachment – at the basal surface, epithelial layer is bound to a thin basement
barrier b/w 2 compartments having diff. components; o blood vessels penetrate an membrane, a complex molecular structure produced by both the epithelium
epithelium and the underlying connective tissue
CHARACTERISTICS
, o Avascularity – all epithelial tissues lack blood vessels; nutrients are obtained o Tight junction – occluding belt; encircles epithelial cells near their apical surface
either directly across the apical surface or by diffusion across the basal surface and completely attaches each cell to its neighbors
from the underlying connective tissue o Adhering junction – adhesion belt; formed completely around the cell;
o Innervation – ability to detect changes in the environment at that body or neighboring cells toward the direction of the basal surface
organ surface; most nervous tissue is in the underlying connective tissue o Desmosomes – adhering spot; like a button or snap b/w adjacent epithelial
o High regeneration capacity – damaged or lost epithelial cells are replaced as cells; small region that holds cells together and provides resistance to
fast as they are lost; continual replacement occurs through the divisions of the mechanical stress at a single point; does not totally encircle the cell
deepest epithelial cells (stem cells) found w/n the epithelium near its base o Gap junction – formed across the intercellular gap b/w neighboring cells;
FUNCTIONS bridged by connexons; provide a direct passageway for small molecules to
o Physical protection – protect both exposed and internal surfaces from travel b/w neighboring cells (i.e. ions, glucose, amino acids and small solutes)
dehydration, abrasion, and destruction by physical, chemical, or biological GLANDS
agents Individual cells or multicellular organs composed predominantly of epithelial tissue;
o Selective permeability – gatekeepers; regulate movement of materials into and perform a secretory function by producing substances either for use elsewhere in
out of the cells; structure and characteristics may undergo change as a result of the body or for elimination from the body (mucin, hormones, enzymes, wastes)
applied pressure or stress (i.e. walking around w/o shoes may increase the Endocrine glands – lack ducts and secrete their products directly into the interstitial
thickness of calluses on the bottom of the feet -> could alter / reduce the fluid and bloodstream; secretes hormones
movement of materials across the epithelium) Hormones – chemical messengers; influence cell activities elsewhere in the
o Secretions – exocrine gland cells are specialized to produce secretions body
o Sensations – some nerve endings of epithelial tissues detect changes in the Exocrine glands – originate from an invagination of epithelium that burrows into the
external environment at their surface and supply info to the nervous system deeper connective tissues; maintain their contact w/ the epithelial surface by
concerning touch, pressure, temperature, and pain (i.e. receptors in the means of duct
epithelium of the skin respond to pressure by stimulating adjacent sensory Duct – epithelium-lined tube through w/c secretions of the gland are
nerves; neuroepithelium houses specific cells responsible for senses of sight, discharged onto the epithelial surface; leads to an organ/body surface;
taste, smell, hearing, and equilibrium) secrete materials onto the surface of the skin (i.e. sweat from sweat
STRUCTURE glands; milk from mammary glands); secrete materials onto an epithelial
o Basement membrane – thin, extracellular layer b/w the epithelium and the surface lining an internal passageway (i.e. enzymes from pancreas into
underlying connective tissue; provides physical support for the epithelium; small intestine; saliva from salivary glands into the oral cavity)
anchors the epithelium to the connective tissue; acts as a barrier to regulate STRUCTURES
movement of large molecules b/w the epithelium and the underlying o Unicellular – do not contain a duct; located close to the surface (i.e. goblet cell)
connective tissue; has 2 specific layers: Mucin – glycoprotein that upon hydration forms mucus; mucus coats the
o Basal lamina – contains collagen fibers, protein, carbohydrate inner surface of the respiratory passageway to cover and protect its lining
macromolecules that are secreted by the cells of the epithelium and to help warm, humidify, and cleanse the inhaled air before it reaches
o Reticular lamina – cells in the connective tissue underlying the the gas exchange surfaces in the lungs
epithelium; contains protein fibers, protein, carbohydrate o Multicellular – composed of cells that work together to produce a secretion and
macromolecules secrete it onto an epithelium; found in the mammary glands, pancreas, and
INTERCELLULAR JUNCTIONS salivary glands; consists of:
specialized connections in lateral membranes that binds epithelial cells together Acini – secretory portions; produce secretions
Ducts – conducting portions; transports secretion to the epithelium
Chapter 3: Tissues
Tissues – groups of similar cells and extracellular products that carry out a common
function (i.e. providing protection, facilitating body movement)
Histology – study of tissues and their relationships within organs
4 PRINCIPAL TYPES OF TISSUES
epithelial, muscle, nervous, connective;+ vary in the structure of their specialized
cells and the functions of these cells and the presence of an extracellular matrix that
surrounds the cells and is produced by them
Matrix – womb; composed of varying amounts of protein fibers, water, and
dissolved macromolecules; consistency ranges from fluid to quite solid (i.e. o o Cellularity – cells of an epithelium are bound closely together by diff. types
epithelial, muscle, and nervous tissues have little matrix b/w cells; connective tissue of cell junctions; composed almost entirety of cells
contains varying amounts of extracellular matrix) o Polarity – every epithelium has an apical surface and a basal surface
EPITHELIAL TISSUE apical surface – free or top surface; exposed to the external environment
lines every body surface and all body cavities; forms both the external and internal basal surface – fixed or bottom surface; where the epithelium is attached
lining of many organs; constitutes the majority of glands to the underlying connective tissue
Epithelium – composed of one or more layers of closely packed cells that form a o Attachment – at the basal surface, epithelial layer is bound to a thin basement
barrier b/w 2 compartments having diff. components; o blood vessels penetrate an membrane, a complex molecular structure produced by both the epithelium
epithelium and the underlying connective tissue
CHARACTERISTICS
, o Avascularity – all epithelial tissues lack blood vessels; nutrients are obtained o Tight junction – occluding belt; encircles epithelial cells near their apical surface
either directly across the apical surface or by diffusion across the basal surface and completely attaches each cell to its neighbors
from the underlying connective tissue o Adhering junction – adhesion belt; formed completely around the cell;
o Innervation – ability to detect changes in the environment at that body or neighboring cells toward the direction of the basal surface
organ surface; most nervous tissue is in the underlying connective tissue o Desmosomes – adhering spot; like a button or snap b/w adjacent epithelial
o High regeneration capacity – damaged or lost epithelial cells are replaced as cells; small region that holds cells together and provides resistance to
fast as they are lost; continual replacement occurs through the divisions of the mechanical stress at a single point; does not totally encircle the cell
deepest epithelial cells (stem cells) found w/n the epithelium near its base o Gap junction – formed across the intercellular gap b/w neighboring cells;
FUNCTIONS bridged by connexons; provide a direct passageway for small molecules to
o Physical protection – protect both exposed and internal surfaces from travel b/w neighboring cells (i.e. ions, glucose, amino acids and small solutes)
dehydration, abrasion, and destruction by physical, chemical, or biological GLANDS
agents Individual cells or multicellular organs composed predominantly of epithelial tissue;
o Selective permeability – gatekeepers; regulate movement of materials into and perform a secretory function by producing substances either for use elsewhere in
out of the cells; structure and characteristics may undergo change as a result of the body or for elimination from the body (mucin, hormones, enzymes, wastes)
applied pressure or stress (i.e. walking around w/o shoes may increase the Endocrine glands – lack ducts and secrete their products directly into the interstitial
thickness of calluses on the bottom of the feet -> could alter / reduce the fluid and bloodstream; secretes hormones
movement of materials across the epithelium) Hormones – chemical messengers; influence cell activities elsewhere in the
o Secretions – exocrine gland cells are specialized to produce secretions body
o Sensations – some nerve endings of epithelial tissues detect changes in the Exocrine glands – originate from an invagination of epithelium that burrows into the
external environment at their surface and supply info to the nervous system deeper connective tissues; maintain their contact w/ the epithelial surface by
concerning touch, pressure, temperature, and pain (i.e. receptors in the means of duct
epithelium of the skin respond to pressure by stimulating adjacent sensory Duct – epithelium-lined tube through w/c secretions of the gland are
nerves; neuroepithelium houses specific cells responsible for senses of sight, discharged onto the epithelial surface; leads to an organ/body surface;
taste, smell, hearing, and equilibrium) secrete materials onto the surface of the skin (i.e. sweat from sweat
STRUCTURE glands; milk from mammary glands); secrete materials onto an epithelial
o Basement membrane – thin, extracellular layer b/w the epithelium and the surface lining an internal passageway (i.e. enzymes from pancreas into
underlying connective tissue; provides physical support for the epithelium; small intestine; saliva from salivary glands into the oral cavity)
anchors the epithelium to the connective tissue; acts as a barrier to regulate STRUCTURES
movement of large molecules b/w the epithelium and the underlying o Unicellular – do not contain a duct; located close to the surface (i.e. goblet cell)
connective tissue; has 2 specific layers: Mucin – glycoprotein that upon hydration forms mucus; mucus coats the
o Basal lamina – contains collagen fibers, protein, carbohydrate inner surface of the respiratory passageway to cover and protect its lining
macromolecules that are secreted by the cells of the epithelium and to help warm, humidify, and cleanse the inhaled air before it reaches
o Reticular lamina – cells in the connective tissue underlying the the gas exchange surfaces in the lungs
epithelium; contains protein fibers, protein, carbohydrate o Multicellular – composed of cells that work together to produce a secretion and
macromolecules secrete it onto an epithelium; found in the mammary glands, pancreas, and
INTERCELLULAR JUNCTIONS salivary glands; consists of:
specialized connections in lateral membranes that binds epithelial cells together Acini – secretory portions; produce secretions
Ducts – conducting portions; transports secretion to the epithelium
