Epithelial Tissues Flashcards
What are epithelial tissues?
Lining tissues that cover all internal and external body surfaces
Eg tissues, tubes, cavities
Give 3 examples of systems epithelial tissues line?
Digestive
Respiratory
Cardiovascular
2 common features of epithelial tissues?
Barrier function - all substances entering/leaving body must pass through
Form continuous boundary between different environments
How are epithelial cells arranged?
Continuous sheets of tightly bound cells with connective tissues Underlying to give nutrients
Why does connective tissues underlay epithelial cells?
To provide nutrients
What do epithelial cells help to control?
What does this prevent?
What substances enter and leave cell therefor prevent microbial invasion
Name the 3 surfaces of epithelial cells?
Apical
Lateral
Basal
Describe a tight junction.
What is it’s purpose?
Creates impermeable seal between adjacent cells
Prevents water passage
Describe desmosomes.
Strong junctions that anchor adjacent cells together.
What do desmosomes ensure?
Epithelial cells can stretch while maintaining contact.
What is the structure of epithelial cells?
Continuous sheets of cells
Tightly bound together
Polarised
Function of epithelial tissues?
Cover and line all surfaces
Form a barrier
Name 4 specialised functions of epithelial tissues.
Protection
Diffusion
Absorption
Secretion
What is the least metabolically active shape of epithelial tissue?
Describe it.
SQUAMOUS
flat thin scale like cells
Has passive diffusion of cells through the epithelial layer.
Name the 3 mains shapes of epithelial tissue.
What is the 4th?
Squamous
Cuboidal
Columnar
Transitional
What does simple epithelium mean?
Single layer of cells
What does stratified epithelium mean?
2 or more layers of cells
What does pseudostratified mean?
One layer by appears stratified
Nuclei are at different heights
Cillia present on apical surface
Describe transitional epithelial cells.
Mix all tall and flat cells
Stratified
Only found in bladder - allow for stretch and recoil
Name 3 apical specialisations.
Microvilli
Cillia
Keratin
What are microvilli?
Small finger like projections that extend into lumen
Found where function is absorption
Increase apical surface area
What is Cillia?
Long hair like projections that best rhythmically to move matter along apical surface
Found where mucous secretions take place
Movement of particular matter
What is keratin?
Strong protective apical layer
Strong interlinked protein
Involved in water proofing and protection
What is the function and location of a simple squamous epithelium?
Function: lines all surfaces involved in passive diffusion (facilitated diffusion)
No energy required
Location:
lungs (alveoli)
Capillaries (endothelium)
Describe the function and location of simple cuboidal epithelia.
Function: line small ducts and tubules involved in absorption/secretion
More metabolically active so bigger to support active function
Location:
renal tubules (absorption)
Salivary glands (secretion)
Describe the function and location of simple columnar epithelium.
Function: lines absorptive surfaces
Thicker so has more protection
Location: small intestine (microvilli present
What do microvilli do on simple columnar epithelium?
microvilli increase surface area which helps to facilitate absorbing nutrients
Describe simple columnar ciliated.
Function and location
Function: ciliary action facilitated transport of ovum from ovary to uterus
Location: female reproductive tract
Describe pseudo-stratified columnar ciliated.
Function and location
Function: ciliary action propel surface layer of mucus containing trapped particles towards pharynx.
Location: always of respiratory system
Position of nucleus is different
What is a goblet cell?
-Modified columnar epithelium
-Synthesise and secrete mucous
-Scattered throughout simple columnar epithelial cell (respiratory/ GIT)
-packed with mucins
- Don’t have cilia
Describe stratified cuboidal epithelium.
Function and location
Function: secretory (have more protection than simple/ more robust
Location: RARE some secretory glands and ducts
Describe stratified columnar epithelium.
Function and location.
Function: secretory & protective
Location: RARE male urethra and lining some glands
Describe features of a stratified squamous epithelium.
- found where function is to protect against mechanical abrasion
- cells migrate to surface and are shed as anucleate squames
Stratified squamous epithelia can be nonkeratinised or keratinised on apical surface.
What does keratin do?
Enhances resistance to physical stress
Accumulate keratin filaments as they mature
Tough, non living surface layer that cross links so doesn’t shed
What does transitional epithelium do?
It allows for expansion and stretch
Found only in bladder
Flat when stretched
Tall when relaxed
What is caused by a break in the continuity of epithelium?
Ulceration
Caused by herpes
Targets cuboidal cells at bottom
No access unless there is damage to top of epithelium cells
What is an oral squamous cell carcinoma?
Dysplastic (abnormal) epithelial cells proliferate in an uncontrolled manner
Destroy/ invade adjacent cells
Attacked by immune system
Suggests cancer
