Lecture 6 - Epithelial Tissues Flashcards
Desc. the function and locations of single squamous (flat, bulging nucleus) epithelia cells.
- Fast exchange of materials + act as barrier (blood brain barrier) + tissue lubrication
- Bowman’s capsule
Desc. function and location of simple cuboidal (width = height) epithelium
- Absorption and secretion (collecting duct)
- Synthesise thyroglobulin and store in colloid (thyroid gland)
- Barrier (ovary)
Desc. function and location of simple columnar (height > width) epithelium cells
- Absorption of nutrients (small intestine [microvilli]
- Movement of lumen contents (small intestine)
- Lubrication (small intestine & colon)
Desc. function and location of pseudostratified epithelia (nuclei at diff layers)
- Upper respiratory tract (nasal cavity –> bronchioles)
- Involved in mucocilliary escalator: goblet cells secrete mucus (trap pathogen) + cilia beat (removal of pathogen)
Desc. function and location of stratified squamous non-keratinised epithelia (bulging nuclei, multiple layers, outermost is thin squamous)
- Oral cavity, oesophagus, vagina, anal canal
- Protect against abrasion
- Reduce water loss, moist
What is a special feature of the stratified squamous epithelia (multiple layers of flattened cells) in the vagina? What is its function?
- Rich in glycogen –> lactic acid–> low pH–> destroy bac. & virus
- Prevent abrasion
- Reduce water loss & moistens
Desc. function and location of stratified squamous keratinised epithelia (outermost layer lost nuclei become keratinised)
- Outermost dead cells - stratum corneum
- Skin: Prevent H2O loss, prevent ingress of pathogen, prevent abrasion, shielding against UV light
What cell type makes up the most of stratified keratinised epithelia cells?
- Keratinocytes
How do keratinocytes divide and what is their function?
- Mitosis at basal layer.
- Move towards apical whilst differentiating –> lose ability to divide –> lose nuclei become keratin
- Normal transit time: 28-40
- Function: synthesise keratins (strength)
What is psoriasis?
- Transit time of keratinocytes frm basal to apical reduce to 2-4 days
- Stratum corneum in abundance: silvery scales
Function of melanocytes
- Produce melanin: give skin color
- Melanin production⬆️ in tan skin but X melanocytes
Function of Langerhans cells
- highly specialised
- Present antigens to T lymphocytes (mediate immune reactions)
Desc. function and location of transitional epithelium. (urothelium, vary in shape from columnar/cuboidal to flattened)
- Urinary tract: Protection to underlying tissue, distension
Function of goblet cells
- Lack of cilia so have microvilli.
- Release mucins thru exocytosis + followed by H2O
Effects of cystic fibrosis. (airways, liver, pancreas, small intestine, reproductive tract, skin)
- Airways: Clogging and infection of bronchial passage w thick sticky mucus (obstruct breathing & dmg lungs)
- Liver: Block bile duct
- Pancreas: Zymogen secretions X released
- S.I: Thick, non-motile stool in neonates
- Skin: Very salty sweat
- Reproductive tract: No vas deferens, thick mucous plug in cervix prevent semen fertilise (infertile)
Function of Club/Clara cells
- In terminal bronchioles
- Protects bronchiolar epithelium (on apical): secrets uteroglobin + pulmonary surfactant
- Detoxification of harmful sub. inhaled
- Act as stem cell, regenerate bronchiolar epithelium (stratified squamous non-keratinised)
Function of microfold cells
- Found in small intestine close to lymph nodes
- Trap pathogens
- Present to lymphocytes n macrophages (immune response)
Why does M cells represent weak point of immune response?
- Some bac (Salmonella bac.) use it as a point of entry
Function of stereocilia
- In inner ear: Hearing & balance
- Vas deferens: Facilitate absorption of residual sperm body
What happens to the lungs in the early and chronic stages of smoking?
Early:
- Normal mucus layer thickens
- Cilia die & regenerate (2-4 days)
Chronic:
- Goblet cells proliferate
- Club cells die (X regenerate)
- Carcinogens induce mutations
- Pneumonocytes (alveoli) die, fibroblasts lay down scar tissue
Renewal rates: A. Trachea B. Alveoli C. Goblet cells D. Club cells
A. 1-2 months
B. 8 days
C. 10 days
D. NEVER
What is the diff btw acute and chronic bronchitis?
- Acute:
i) Cough and excess mucus production + breathlessness (< 3 months)
ii) Reduced lung function due to inflammation, narrowing of airways - Chronic:
i) Chronic inflammation + cough + mucus (> 3 months)
ii) Irreversible damage to bronchioles and alveoli
What is emphysema?
- Permanent widening of air spaces
- Damage to alveoli (no elasticity)
What diseases make up COPD?
Emphysema and chronic bronchitis
What is asthma?
- Wheeze, shortness of breath
- Caused by bronchospasm (tightening of smooth muscle layer in bronchi + bronchioles)
- Mucus obstruction + narrowing of airways
In alveoli of lung, the endothelial cells of the capillaries and the pneumonocytes of the air sacs are separated by what?
- Basal lamina
Compare mucous and serous membranes
Mucous membranes: Line internal tubes which open to the exterior
- GI tract, urinary tract, respiratory tract
- Consists of epithelium lining –> connective tissue (lamina propia) –> smooth muscle (muscularis mucosae)
Serous membranes: Line closed body cavities which DO NOT open to the exterior
- Peritoneum - abdominal organs, pleural sacs- lungs, pericardial sac- heart
- Consists of squamous epithelium (mesothelium) that secretes lubricating fluid (prevent friction) –> thin layer of connective tissue (attach to meso. & adjacent tissues)
What are the outer and inner serous membranes each called?
Outer - parietal serosa (closer to cavity)
Inner - visceral (closer to organ)
Define epithelium
Layer of continuous cells that cover external surface of body and line internal surfaces
Define metaplasia & neoplasia
- Metaplasia: Epithelial cell changes from one type to another (heavy smokers, change from pseudostratified –> stratified squamous)
- Neoplasia: Tumour (carcinoma) in epithelial cells. (goblet cells proliferate in cigarette smoke)
Extra: Adenocarcinoma is tumours of epithelial cells
