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
What causes Cystic Fibrosis?
- Mutation in CFTR gene
- deficiancy in Cl ions release
- mucous very sticky
What are the effects of cystic fibrosis?
- Airways : clogging and infection of bronchial passage, breathing obstructed
- Liver : small bile duct blocked - disrupts digestion
State the characteristics and functions of clara cells
Characteristics
- on airway side of terminal bronchioles
- club like apical surfaces
- no cilia, no basal bodies
Function
- Protect bronchiolar epithelium - secrete uteroglobin
- Detoxify harmful substances inhaled into lungs
- Act as stem cells - regenerate bronchiolar epithelium
State the characteristic and functions of Microfold cells
Characteristic
- Found only in small intestine, close to lymphatic nodule
- Have folded extensions
Function
- Trap pathogens and present to dendretic cells
*weakness : portal of entry for pathogens
State the functions of Stereocilia
Inner ear
- mechanosensing organelles
- respond to fluid motion for hearing and balance
epididymis and vas deferens
- facilitate absorption of residual sperm body
What are the cell renewal rates of the airway epithelium?
- Clara cells : never
- Trachea : 1-2 months
- Goblet cells : 10 days
- Alveoli : 8 days
What is the effect of smoking on lungs at the early stage?
- mucus layer thickens
- cilia die
- ciliagenesis : 2-4 days
What is the effect of smoking on lungs at the chronic stage?
- goblet cells poliferate
- clara cells die
- carcinogens induce mutations
- fibroblast lay down scar tissue
What are the common respiratory conditions related to smoking ?
- Acute bronchitis
- Chronic bronchitis
- Emphysema
- COPD
- Asthma
Describe some of the common respiratory conditions related to smoking
1. Emphysema :
shortness of breath - permanent widening of airspaces
2. Asthma :
- wheeze, shortness of breath, chest tightness and cough.
- Caused by bronchospasm, obstruction from mucus and narrowing of airways
3. Chronic bronchitis :
- chronic inflammation of bronchi and bronchioles.
- Reduced lung function - excess mucus in the lung passage
- irreparable damage to bronchioles and alveoli
Describe the mucocilliary escalator in trachea
- mucous lining trachea traps inhaled particles
- upward beating of cilia drives debris-laden mucus towards the pharyx
What is epithelia metaplasia
capacity of epithelial cell to differentiate to another cell
What is neoplasia
- Changes that occur in epithelia - give rise to tumour
What is adrenocarcinoma?
Tumour of epithelial origin
How are cross sections of cuboidal and columnar cells differentiated under slide?
cuboidal : polygonal
columnar : hexagonal
