L4 : Epithelial cells and surface specialisations Flashcards
State the characteristics of serous membranes
- Line certain closed body cavities (not open to exterior)
- envelop internal organs
- thin layer of connective tissue
What is the fucntion of serous membrane?
secrete lubricating fluid : promotes friction free movement of structures
Give examples of serous membranes
- perinoteum : envelops abdominal organs
- pleural sacs : envelops lungs
- pericardial sac : envelops heart
What are the outer and inner walls of serous membrane called?
- outer : parietal serosa
- inner : visceral serosa
Define Epithelium
- Sheets of contiguos cells of varied emryonic origin,
- cover the external surface of body and
- line internal surface including blood vessels
What are the surfaces with epithelial linings for exterior, interior opened to exterior and interior not opened to exterior?
- Exterior : Skin
- I E : respiratory tract, GI tract, urinary tract
- I x E : peritoneum, pericardial sac, pleural sac
What are the classifications of epithelial cell types?
Simple (one cell thick):
- squamous
- cuboidal
- columnar
- pseudostratified
Stratified (more than oct):
- squamous
- cuboidal
- columnar
- transitional

State function of simple squamous epithelia
- fast material exchange : respiratory space in lungs
- barrier to fluids : in brain and CNS
- tissue lubrication : serous membrane
State function of simple cuboidal epithe.
- Absorbtion and secretion (exocrine glands, thyroid glands, pancreatic duct, collecting duct…)
- Hormone synthesis
State function of simple columnar epitheli.
- Absorption of nutrients (small intestine, colon)
- *(some contains microvilli - inc SA)
- Secretion (stomach lining, small intestine, colon)
- Lubrication (small intestine, colon)
State the characteristic of pseudostratified epithelia
- All cells make contact with basement membrane
- not all cells reach epithelial surface
- nuclei at different levels
State the function of pseudostratified epithelium
- Mucus secretion
- particle trapping and removal
Where are pseudostratified epithelium located?
Lining of nasal cavity, trachea and bronchi
(conduction portion)
State the function of stratified squamous non-keratinised epithelium
- protection against abrasion
- reduces water loss while remaining moist
Location : oesophagus, vagina, anal canal
What is the key feature of stratified squamous keratinised epithelium?
Stratum corneum : consist of outermost cells which are dead, lost their nuclei and cornified.
State the function of stratum corneum
- reduces water loss
- protect against abrasion
- barrier towards toxins and microbes
Describe the process of keratinocytes maturing from basal layer to stratum corteum
- Stratified squamous keratinised epithelium made up of keratinocytes
- keratinoctyes undergo mitosis at basal layer
- daughter keratinocytes move towards surface, differentiating and losing ability to divide
- keratinocytes synthesis keratins(provide strength for epidermis)
- movement of keratinocytes from basal layer to stratum corteum : 28-40 days
What are the other cells of the epidermis?
- Melanocytes
- Langerhans cells
What is the function of melanocytes?
- produce melanin - main pigments that give skin its colour
- * darker skin, more melanin but same number of melanocytes

What is the function of langerhans cells?
- present antigens to T lymphocytes
- mediate immune reactions

How are melanin from Mature melanosomes transferred to neighbouring keratinocytes?
- Pigment donation - involve phagocytosis of tips of dendritic processes

What is the function of stratified squamous keratinised epith?
- Protection against abration
- prevent water loss
- shielding against UV light
- prevent microbial ingress
Where is transitional epithelium found and state its function
- Urinary tract
- protection of underlying tissue from toxic chemicals
List the different types of cell surface specialisations and state each function
- Keratin : protects against abrasion
- Cilia : controls micro-movement of luminal contents
- Goblet cells : secretes mucus
- Clara cells : act as stem cells for respiratory epithelium
- Microfold cells
- Stereocilia

