epithelial tissue I A Flashcards
c.t.
- connective tissues
2. embedded tissues
submucosa
- CT
2. embedded tissue
mucosa
- epithelium
2. C.T.
muscularis mucosa
smooth muscle
mucosa has two layers and multiple tissues
- epithelium
2. lamina propria
lamina propria
- C.T
- embedded tissue
- Blood vessels
- muscle
- epithelium
epidermis=
epithelium
dermis is
- C.T
- Blood vessels
- epithelium
- muscle
- nerve
hypodermis
- superficial fascia
- C.T
- blood vessels
- epithelium
- muscle
- nerve
types of epithelium
- simple squamous
- simple cuboidal
- simple columnar
- stratified columnar
- pseudostratified columnar
- transitional
- stratified squamous
stem cell function
divide, renew and produce differentiated progeny
What are epithelia?
Epithelia are the tissues that line body surfaces, body cavities, and the surfaces of internal tubes, ducts, and other spaces in organs.
What do epithelia comprise?
They comprise the main functional units of glands and several organs.
properties of epithelia?
- adhere together
- arranged in one to several layers or sheets
- most are polarized
- epithelial cells themselves are polarized
- attached to basal lamina
- undergo turnover or renewel
- avascular
- highly diverse
How are most epithelia are polarized (asymmetric)?
apical and basal surfaces
apical surface
free outer surface
exposed to the fluids or environment
basal surface
or basolateral surface
connected to underlying connective tissue
What is the basal lamina?
(a sheet of extracellular material)
It lines and is attached to the basal surface and is also attached to elements of the underlying connective tissue
Explain how epithelial tissues undergo turn-over or renewal:
cells die and must be replaced by cell division and differentiation, processes that are driven by epithelial stem cells.
What is the consequence of epithelial tissues being avascular?
Because they have no direct blood supply, nutrients and oxygen must diffuse through connective tissue and through the basal lamina to reach epithelial cells
within any given epithelium, there can be______
several different cell types
Functions of epithelia?
- barrier that protects against abrasion, infection, harmful chemicals or radiation
- selective absorption and transport of various molecule from the environment
- Selective secretion of various molecules and fluids.
- Movement of particles and mucous through passage ways.
- Biochemical modification of molecules (e.g. liver)
- Communication to (and from) other tissues and organs
- Reception of sensory stimuli (e.g. smell, taste and touch)
Different epithelia have distinct functions:
Some carry out a very specific function (e.g. cells of the anterior pituitary gland secrete pituitary hormones) while some carry out many of the functions listed above (e.g. the intestinal epithelium protects, absorbs, secretes, and sends molecular signals to other organs/tissues)
Two special types of epithelia:
- endothelium
2. mesothelium
endothelium
tissue that faces blood and lymph
Mesothelium:
the sheets of cells that line the enclosed internal spaces of the body cavities
mucosa
moist linings of internal passage ways
epithelia derived from
all 3 primary germ layers (ectoderm, mesoderm and endoderm)
epithelial to mesenchymal transition
embyronic epithelia often disassemble and move into the mesenchymal tissue.
There they may migrate to other locations to form new epithelia or they may transform into distinct non-epithelial cell lineages that give rise to other tissue
Epithelial tissues line
all surfaces that face the outside world (e.g. the air and the passageways of the gastrointestinal tract) and they form the surfaces of internal tubes, ducts, and secretory tissues.
The apical side faces _____
the space or outside world,
Throughout the body, epithelia have a common general relationship to each of the other major tissue types;
connective tissues (CT), blood vessels (and blood), muscles, and nerves.
the basal side is attached to the ____
basal lamina, which in turn is attached to the underlying connective tissue (CT)
some specific sensory nerve cells make intimate contacts with _______.
specific epithelial cells specialized for sensory input (e.g. taste buds in the tongue).
dendritic cells:
which infiltrate epithelia and can migrate out (and in), enter the connective tissue, and get into blood or lymph.
