A&P Ch 4 Tissues: The Living Fabric (EPITHELIAL TISSUE)
Epithelial Tissue
a sheet of cells that covers a body surface or lines a body cavity
Functions of simple columnar epithelium
absorption, secretion of mucus, enzymes and other substances.
Holocrine
accumulate products within then rupture.
Function of simple squamous epithelium
allows material to pass by diffusion and filtration in sites where protection isnt important; secrets lubricating substances in serosae.
Apical Surface
an upper free surface exposed to the body exterior or the cavity of an internal organ
With which portion of an epithelial cell in the stomach would food be in contact?
apical surface
cells farthest from basal layer of Stratified squamous epithelium
are less viable and depends on diffusion of nutrients from deeper connective tissue
Next to the basal surface of an epithelium is a thin supporting sheet called the
basal lamina
Endocrine Glands
because they usually lose their duct, they're called "ductless glands". through exocytosis, they secrete hormones that travel through lymph or blood to their specific target organs. each hormones prompts its target organs to respond in some characteristic way.
Connective Tissues composed of
bones, tendons, fat and other soft padding tissue
Cuboidal cells
boxlike and approximately as tall as they are wide nucleus round
Nervous Tissue composed of
brain, spinal cord, and nerves
Some epithelial tissues such as that lining the trachea(windpipe) have motile
cilia
Characteristics; Avascular but Innervated: Epithelial
contains no blood vessels (avascular) so it must be nourished by diffusion from blood vessels in the underlying connective tissues. supplied by nerve fibers (innervated)
Reticular Lamina
deep to basal lamina layer of extracellular material containing network of collagen protein fibers that belongs to the underlying connective tissues
Basal lamina acts as a selective filter that
determines which molecules diffusing from the underlying connective tissues are allowed to entered the epithelium.
Characteristics; Specialized Contacts: Epithelial
epithelial cells fit closely together to form continuous sheets. Lateral contacts including tight junctions and desmosomes bind adjacent cells together at many points.
Mesothelium
epithelium of serous membrane in the ventral body cavity
Stratified Squamous Epithelium forms the
external part of the skin . epidermis of the skin (outer layer) has keratin, a tough protective protein. the other stratified squamous epithelia of the body has no keratin.
Microvilli
fingerlike extensions of the plasma membrane.
Squamous cells
flattened and scale like nucleus flatened
Covering and Lining Epithelium
forms the outer layer of the skin. covers the walls and organs of the closed ventral body cavity.
Basal Lamina consists of
glycoproteins secreted by the epithelial cells plus some fine collagen fibers.
Characteristics; Supported by Connective Tissues: Epithelial
has reticular lamina and a basement membrane
Characteristics: Regeneration: Epithelial
high regenerative capacity so there is some degree of mitosis present for life. stimulated by loss of apical-basal polarity: some exposed to friction and some exposed to hostile substances. can replace lost cells by cell division as long as it is receiving nutrients
Location of Simple Squamous Epithelium
kidneys glomeruli air sacs of lungs lining of heart, blood vessels and lymphatic vessels; lining of ventral body cavity (serosae).
Location of simple cuboidal epithelium
kidneys tubules, ducts & secretory portions of small glands; ovary surface.
Stratified Columnar Epithelium
limited distribution in the body small amounts in pharynx, male urethra and lining some glandular ducts. occurs at transition areas between 2 other types of epithelia. only apical layer columnar
Location of Transitional Epithelium
lines the ureters, bladder & part of the urethra.
Epithelial Tissues forms
lining of digestive tract organs and other hollow organs
Endothelium
lining of lymphatic vessels, blood vessels and heart
Basal Surface
lower-attached facing the basement membrane
Multicellular Exocrine Glands
made of a duct and a secretory unit usually surrounded by supportive connective tissue supplies blood and nerve fibers extends into and divides glands into lobes
Epithelial membrane
made up of at least 2 primary tissues types; 1. an epithelium bound to underlying connective tissue proper 2. are simple organs
Basement Membrane
makes up the basal lamina and reticular lamina reinforces epithelial sheet resists stretching and tearing define epithelial boundary
Glandular epithelium
makes up the secreting portion of glands such as the thyroid gland, adrenal glands, and sweat glands.
Merocrine
most secrete products by exocytosis as produced
Stratified Squamous Epithelium
most widespread of the stratified epithelia. made up of many layers, thick and has protective role in the body. free surface cells are squamous and cells of deeper layers are cuboidal or columnar. found in areas subjected to wear and tear.
Mucous Membranes
mucosa indicates location, not cell composition also called mucosae -line body cavities open to the exterior (digestive, respiratory, urogenital tracts) may secrete mucus.
Unicellular Exocrine Glands
mucous and goblet cells found in epithelieal linings of the intestinal and respiratory tracts. all produce mucin - complex glycoprotein that dissolves in water when secreted to form mucus (slimy protective, lubricating coating).
Exocrine glands include
mucous, sweat, oilnand salivary glands, the liver (secretes bile), the pancreas (synthesizes digestive enzymes) and etc.
Muscle Tissues composed of
muscles attached to bones muscles of heart muscles of walls of hollow organs (smooth)
Location of simple columnar epithelium
noncilia types lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands. lines small bronchi, uterine tubes, and some regions of the uterus.
Location of Pseudostratified Columnar Epithelium
nonciliated type in males sperm carrying ducts and ducts of large glands, ciliated variety lines the trachea, most of the upper respiratory tract.
Special Characteristics of Epithelial Tissue
polarity, specialized contacts, suppported by connective tissues, being avascular but innervated and ability to regenerate.
Functions of Epithelial Tissue
protection, absorption, filtration, excretion, secretion & sensory reception
Tight junctions in epithelial helps keep
proteins in the apical region of the plasma membrane from diffusing into the basal region and helps to maintain epithelial polarity.
Stratified Cuboidal Epithelium
quite rare found in some sweat and mammary glands typically 2 cell layers thick
Transitional Epithelium
resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar shape.
Glands
secrete material endocrine glands are ductless exocrine glands have ducts.
Functions of Pseudostratified columnar epithelium
secrete substances particulary mucus, pushing of mucus by ciliary action.
Exocrine Glands
secretes their products on body surfaces (skin) or into body cavities. more numerous than endocrine glands. multicellular glands secrete products into ducts.
Function of simple cuboidal epithelium
secretion and absportion
Serous Membranes
serosae- found in closed ventral body cavity simple squamous epithelium parietal serosae line internal body cavity walls visceral serosea covers internal organs serous fluid between layers moist membranes pluerae (lungs), pericardium (heart), peritoneum (abdomen).
Which of the following types of epithelial tissues is best suited for areas of the body where diffusion or filtration occurs?
simple squamous
Simple Epithelial Tissue
single layer of cells. typically found where absorption, secretion, and filtration occurs very thin.
Simple cuboidal epithelium
single layer of cubelike cells with large, spherical (circular) central nuclei.
Simple squamous epithelium
single layer of flattened cells with disc-shaped central nuceli and scattered cytoplasm. the simplest of the epithelia.
Simple columnar epithelium
single layer of tall closely packed cells aligned like soldiers in a row. round to oval nuclei. some cells have cilia. may contain muscus-secreting unicellular glands.
Pseudostratified columnar epithelium
singler layer of cells of differeing heights. some not reaching the apical surface. nuclei seen at different levels.may contain cilia and mucus bearing cells.
Cutaneous Membranes
skin has keratin stratified squamous epithelium (epidermis) attached to a thick layer of connective tissues (dermis) dry membrane
Function of Transitional Epithelium
stretches readily, permits stored urine to inflate urinary organ
Histology
study of tissues
Columnar cells
tall and column shaped nucleus elongated
Locations of stratified squamous epithelium
the no keratin types forms moist lining of the esophagus, mouth and vagina. keratin type forms the epidermis of the skin, a dry membrane.
Cilia
tiny hairlike projections that move substances along their free surface.
What is the function of serous membranes
to reduce friction and organs from rubbing against each other because if that happened, it would produce heat.
Stratified Epithelial Tissues
two or more layers of cells stacked on top of each other. common in areas where protection is important such as skin surface and the lining of the mouth.
Characteristics; Polarity: All Epithelial have an
1. Apical Surface 2. Basal Surface
3 common shapes of Epithelial cells
1. Squamous cells 2.Cuboidal cells 3.Columnar cells
Multicellular exocrine glands can be classified by structure and by the type of secretion
1. Structure: simple or compound glands. cells tubular, alveolar or tubuloalveolal. 2 Types of Secretion: 1.Merocrine 2.Holocrine
3 types of epithelial membrane
1. cutaneous membranes 2. mucous membranes 3. serous membranes
2 types of simple squamous epithelium
1. endothelium 2. mesothelium
Glands are classified by 2 sets of traists
1. site of product release - may be endocrine (internally secreting) or exocrine (externally secreting) 2. may be unicellular or multicellular
2 Types of Epithelium
1.Covering and lining 2.Glandular
Classification of Epithelial Tissue
1.Simple Epithelial 2.Stratified Epithelial.
Tissue
A group of cells similar in structure and that perform a common or related function.
What kind of process is secretion
Active Process
4 Primary Tissues
Epithelial (covers), Connective(supports), Muscle (produces movement) and Nervous (controls)
Glands are made up of
Epithelial Tissue
An area in the body exposed to the external environment would be composed of which of the following tissue types?
Epithelial tissue
Epithelial tissue is the only tissues type that has polarity, that is, an apical and basal surface? Why is this important?
Epithelial tissues lines body cavities and covers the body's external surface; thus polarity with one free (apical) surface is a requirement.
Which gland type - merocrine or holcrine - would you expect to have the highest rate of cell division? Why?
Holocrine glands have the highest rate of cell division. The secretory cells fragment and are lost in the secretion; thus the secretory cells must be continuously replaced.
Most apical surfaces have
Microvill(e.g. brush border of intestinal lining)
Some epithelia are pseudostratifed. What does this mean?
Pseudostratified epithelia appear to be stratified because their cell's nuclei lie at different distances from the basement membrane. However, all cells rest on the basement membrane.
Stratified epithelia are "built" for protection or to resist abrasion. What are the simple epithelia better at?
SImple epithelia are "built" to provide for an efficient absorption and filtration across their thin epithelial barriers.
Where is transitional epithelium found and what is its importance at those sites?
Transitional epithelium is is found in the urinary bladder and other hollow urinary organs. The ability of this epithelium to thin allows the urinary organs to store a larger urine volume when necessary.
Glandular Epithelia
a gland has one or more cells that makes and secretes an aqueous fluid (secretion)
