Chapter 4: Tissues Flashcards
What is a tissue?
A tissue is a group of cells that function together to carry out specialized activities.
What are the 4 basic types of tissues
connective, epithelial, muscular and nervous
T or F: tissues can be made of 2 or more cell types
True
Any surface is covered by…
epithelial cells
Cell junctions
contact points between the plasma membranes of tissue cells
5 types of cell junctions
tight, adherins, desmosomes, hemidesmosomes, gap junctions
What do tight junctions inhibit
they inhibit the passage of substances between cells and prevent the contents of these organs from leaking into the blood or surrounding tissues. “water proof”
Adhering junctions
contain plaque, a dense layer of proteins inside the plasma membrane thay attaches to both membrane proteins and to micro filaments of the cytoskeleton. Uses cadherins. not water proof
Cadherins in adherent junctions
inserts into the plaque from the opposite side of the plasma membrane, partially crosses the intracellular space and connects to cadherins of the adjacent cell
Tight junctions
tight junctions consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between cells
Purpose of tight junctions
inhibit the passage of substances between cells and prevent the contents of these organs from leaking into the blood in surrounding tissues
Where are tight junctions found
tissues lining the surface of body cavities; stomach, intestines, urinary bladder
Desmosomes
contain plaque and have transmembrane glycoproteins (cadherins) that extend into the intracellular space between adjacent cell membranes and attach to one another. attach to intermediate filaments in the cytoskeleton
Where are desmosomes abundantly found
in the epidermis of the skin
Hemidesmosomes
resemble desmosomes but they do not link adjacent cells. they anchor cells not to eachother but to basement membranes.
What do hemidesmosomes use instead of cadherins
the transmembrane glycoproteins in hemidesmosomes are integrins rather than cadherin. Integrins attach to intermediate filaments made of the protein keratin.
Basement membranes location in directional terms
basement membranes are deep to the epithelium and superficial to the connective tissue.
Gap junctions
At gap junctions membrane proteins called connexins form tiny fluid filled tunnels called connexons that connect neighbouring cells.
Gap junctions allow;
electrical impulses to pass rapidly from one cell to another which allows for synchronous action.
What do connexons do
allow the ions and small molecules to diffuse from the cytosol of one cell to another, but the passage of large molecules such as vital intracellular proteins is prevented
Epithelial cells
are arranged in sheets and are densely packed with little extracellular matrix. mitosis occurs frequently
Function of basement membranes
thin extracellular layer that connects the epithelial cells to the underlying connective tissues.
Do epithelial tissues contain blood vessels?
no epithelial tissue is avascular but does have a nerve supply.
Name the different types of epithelial tissue cells
- simple squamous
- simple cuboidal
- nonciliated simple columnar
- ciliated simple columnar
- nonciliated pseudostratified columnar
- ciliated pseudostratified columnar
- stratified squamous
- stratified cuboidal
- stratified columnar
- urothelium
Simple squamous epithelium
single layer of flat cells that resembles a tiled floor when viewed from apical surface. Lines the cardiovascular and lymphatic system (called endothelium); forms epithelial layer of a serous membrane in abdominal and thoracic cavities
Function of simple squamous epithelium
present at sites of filtration (kidneys) or diffusion (lungs) and secretion in serous membranes
Simple cuboidal epithelium
single layer of cube shaped cells. covers surface of ovary, lines anterior surface of eye lens, lines kidney tubules and small ducts in glands.
Function of simple cuboidal epithelium
secretion and absorption; becayse nutrients only have to go through on layer of cells
Nonciliated simple columnar epithelium
- single layer of nonciliated column-like cells with oval nuclei near base of cells
- has microvilli on apical surface
- goblet cells in between that secrete mucus
- Lines GI tract, ducts of many glands and gallbladder
Function of nonciliated simple columnar epithelium
- secretion and absorption; mucus lubricates lining of digestive respiratory, and reproductive tracts and urinary tract
- helps prevent destruction of stomach lining by acidic stomach juices.
Ciliated simple columnar epithelium
single layer of ciliated columnlike cells with oval nuclei near the base of cells. Goblet cells usually interspersed. Lines some bronchioles, uterine tubes, uterus, paranasal sinuses
Function of ciliated simple columnar epithelium
In respiratory system, cilia beat in unison to move mucus and foreign particles toward throat to be coughed up or swallowed. Cilia also move oocytes(egg) from ovaries through the fallopian tubes into uterus.
Nonciliated pseudostratified columnar epithelium
appears to have several layers because nuclei are at various levels. even though the cells are attached to the basement membrane in a single layer, some cells do not extend to the apical surface. Does not contain goblet cells
Function of nonciliated pseudostratified columnar epithelium
absorption and secretion.
Ciliated pseudostratified columnar epithelium
appears to have several layers because cell nuclei are at various levels. all cells attached to basement menbrane in a single layer but some cells do not extend to apical surface. Contains cells that extend to the surface and secrete mucus (goblet cells) or bear cilia.
Ciliated pseudostratified columnar epithelium lines…
airways of most upper respiratory tract
Function of ciliated pseudostratified columnar epithelium
secretes mucus and traps foreign particles, and cilia sweep away mucus for elimination from body.
Stratified squamous epithelium
- contains 2 or more layers of cells; cells in apical layer and several layers deep to it are squamous –> cells in deeper layers are cuboidal and columnar. Keratinized variety forms superficial layer of skin. Nonkeratinized lines wet surfaces like (lining of mouth, esophagus, vagina)
Function stratified squamous epithelium
protection against abrasion, water low, UV radiation, and foreign invasion. First line of defense against microbes.
Stratified cuboidal epithelium
has 2 or more layers of cells; cells in apical layer are cube-shaped; fairly rare type. found in ducts of adult sweat glands, an part of male urethra
Function of stratified cuboidal epithelium
Protection; limited secretion and absorption . (limited because of multiple layers)
Stratified columnar epithelium
Basal layers consist of shortened, irregularly shaped cells; only apical layer has columnar cells; uncommon. Lines part of the urethra, small areas of anal mucous membrane, part of conjunctiva of eye.
Function of stratified columnar epithelium
protection and secretion
Urothelium
- cells will change shape
- in a relaxed or unstretched state, looks like stratified cuboidal epithelium, except apical layers tend to be large rounded.
- as tissues stretch, the cells become flatter giving the appearance of stratified squamous epithelium
Function of urothelium
Allows urinary organs to stretch and maintain protective lining while holding variable amounts of fluid without rupturing
Location of urothelium
lines urinary bladder, ureters, and portions of the urethra
Glandular epithelium
a gland is a single cell or a mass of epithelial cells adapted for secretion
Endocrine glands
secretions enter interstitial fluid and then diffuse into bloodstream without flowing through a duct.