L8: Epithelial tissue Flashcards
Epithelium plays an important role in
Diffusion
Absorption
Secretion
Tissue is:
- A diverse group of cells
- With an ordered structure
- Working together for a common function
4 types of tissue:
- Epithelial
- Connective
- Muscle
- Nervous
The basic characteristic of epithelial tissue:
- Covers body surface, lines body cavities
- form glands (skin, airways, digestive lining, and urinary tract lining)
- Closely packed cells
- little extracellular materials
- Basement membrane
- Avascular
- Highly regenerative (using stem cells) (high mitotic activity)
cells in epithelial tissue are joined by….
by Specialized cell-to-cell junctions
describe the Basement membrane:
- It’s a non-cellular membrane
- Compromised of polysaccharide-rich membrane
The function of basement membrane:
- Separates epithelium from underlying connective tissue
- Acts as a sieve to prevent materials from entering the body
The key characteristic of epithelial tissue?
Avascular
why is the epithelial cell highly regenerative
Cells completely lack bloody supply (that’s why they’re highly regenerative)
which is side is the Free surface
- Is the apical side
- Bound to the basolateral side
The function of epithelial tissue:
- Secretion
- Selective absorption
- Protection
- Transcellular transport
- Detection of sensation
Examples of secretion:
- Digestive tract
- Involved in high secretion activity
Selective absorption:
- First contact with the material
- And allows them to be absorbed
selective absorption is associated with a structure known as
microvilli (inc surface area)
the function of Transcellular transport:
- aid the movement of substances from cell-to-cell through a certain distance
- Ex: mucus
What structure does transcellular transport:
cilia
Detection of sensation:
- 1st layer with the outer environment
- To detect sensation along with nerve cells
types/identifications of epithelial tissues:
- 1st through cell shape
- Then layers
Cell shape types:
- Squamous (flat)
- Cuboidal (rectangle)
- Columnar (very elongated)
Surface specialization:
- Keratin
- Microvilli
- Cilia
Keratin:
- Its a protein for hair
- Composes a thick layer of dead cells as protection around the epidermis
Microvilli:
- Inc surface area
- Absorption
- Found in intestine
Cilia:
Involved in motility of substances in the human body
type of layers identification of epithelium
- Simple
- Stratified (multilayer)
- Pseudostratified
- Transitional
Pseudostratified:
Disorganized layering of epithelial tissue that is not simple or stratified
Transitional:
A huge number of disorganized, disproportionate number of epithelia
Transitional is typically found in:
- Urinary bladder
- Why: bc this structure allows the extension & distention of the organ itself
Simple squamous make up the:
- Alveoli (air sacs of the lung)
- The lining of all blood vessels & capillaries (endothelium)
- Various membranes within the body (peritoneum = area where there’s a lot of exchange)
- Glomerulus of kidney
Does it make sense that simple squamous make up The lining of all blood vessels & capillaries (endothelium)
- Yes
- Why: bcs the flatter the surface = the simpler & lesser the layers
- = the more likely it is going to play an important role in facilitating gas exchange
Simple cuboidal makes up the:
- Collecting tubules of the
- kidney
- Liver
- Pancreas
- Thyroid
- & other glands of the body
(synthesis of hormones)
Simple columnar epithelium ciliated makes up:
The lining of the ovary ducts (fallopian tubes)
Simple columnar microvilli epithelium with goblet cells makes up:
- The lining of the intestine
- Secretes mucus
Stratified squamous epithelium:
- Located in areas of body subjected to abrasion
what are the 2 types of Stratified squamous epithelium
Keratinizing stratified squamous
non-Keratinizing stratified squamous:
where can you find Keratinizing stratified squamous:
Skin
where can you find non-Keratinizing stratified squamous:
- Tongue
- Oral mucosa
- Esophagus
- Vagina
Stratified cuboidal epithelium found in:
- Sweat glands
- Salivary glands
- Ovarian follicles
- Seminiferous tubules
Stratified cuboidal epithelium secretes:
- Sweat
- Ovarian hormones
- Sperm
Stratified columnar epithelium are:
- Rare
- Located in the largest ducts of salivary glands (parotid, submandibular)
The basal layer in stratified columnar are:
- Cuboidal cells
- & the layer nearest the apical surface includes columnar cells
- The large droplets are mucus in goblet cells
Epithelia are classified according to
- Cells nearest the lumen
- In stratified columnar case its = columnar
Pseudostratified columnar ciliated epithelium with goblet cells:
- Makes up = lining of the respiratory tract
- Secretes mucus moves mucus, trap foreign particles
Transitional epithelium: (makes up what)
- Makes up: the lining of the urinary bladder & the ureter
- Stratified tissue becomes stretched as the urinary bladder becomes filled with urine (distention)
