Epithelial cells & surface specialisations Flashcards
What is epithelial tissue?
Sheets of contiguous cells of varied embryonic origin that cover external surfaces of the body and line internal surfaces
Functions of simple squamous epithelium (4 things)
- Lubrication (mesothelium in serous membranes)
- Gas exchange
- Water, nutrient & waste product exchange
- Barrier
Locations of simple squamous epithelium as a barrier (5 things)
- Bowman’s capsule
- Skin
- Oesophagus
- Conjunctiva of eye
- Brain
Simple cuboidal epithelium
A single layer of polygonal cells whose height and width are approximately equal
Functions of cuboidal epithelium (4 things)
- Absorption & conduit (exocrine glands)
- Absorption & secretion (kidney tubules)
- Barrier/covering (ovary)
- Hormone synthesis, storage & immobilisation (thyroid)
Simple columnar epithelium
A single layer of cells whose heights are significantly greater than their widths
Functions of simple columnar epithelium (3 things)
- Absorption
- Secretion
- Lubrication
Locations of simple columnar epithelium (3 things)
- Small intestine & colon (ASL)
- Gall bladder (A)
- Stomach and gastric glands (S)
Pseudostratified epithelia
All cells make contact with the basement membrane but not all reach the epithelial cell surface
Functions of pseudostratified epithelium (3 things)
- Secretion & conduit (RT and ductus deferens)
- Mucus secretion
- Particle trapping and removal
Locations of pseudostratified epithelium (3 things)
- Lining of nasal cavity
- Trachea
- Bronchi
Functions of goblet cells (2 things)
- Release of mucins through exocytosis
- Release of water increased by release of ions
Cystic fibrosis- which organs affected and how? (6 things)
- Airways
- Liver (bile ducts)
- Pancreas (lack of zymogen secretions)
- Small intestine (thick, non-motile stools)
- Reproductive tracts (thick mucous plugs, absence of fine ducts)
- Skin
Stratified squamous epithelium
Multiple layers of cells, the outer of which are thin squamous epithelial cells
Stratified squamous non-keratinised epithelium functions (2 things)
- Protection against abrasion
- Reduces water loss but stays moist
Stratified squamous non-keratinised epithelium locations (6 things)
- Oral cavity
- Oesophagus
- Vagina
- Part of anal canal
- Surface of cornea
- Inner surface of eyelid
Stratified squamous keratinised epithelium
Outermost layer is dead cells with no nuclei (stratum corneum)
Stratified squamous keratinised epithelium functions (4 things)
- Protection against abrasion & physical trauma
- Water loss prevention
- Microbial ingress prevention
- Shielding against UV damage
Stratified squamous keratinised epithelium locations (2 things)
- Surface of skin
- Limited distribution in oral cavity
Transitional epithelium (urothelium)
Surface cells vary in shape from columnar/cuboidal to flattened
Functions of urothelium (2 things)
- Distensibility
- Protection of underlying tissues from toxin chemicals
Stratified columnar epithelium locations (4 things)
- Conjunctiva of eye
- Urethra of penis
- Oesophageal glands
- Intralobular ducts of salivary glands
What are serous membranes?
Thin 2 part membranes which line certain closed body cavities and envelope the viscera
What do serous membranes line and what is their function?
They line the peritoneum, pleural sacs and pericardium and excude a lubricating fluid that promotes relatively friction-free movement
What do serous membranes consist of (3 things)?
- Mesothelium (simple squamous) that excudes the fluid
- Thin layer of connective tissue that attaches mesothelium to adjacent tissue
- Vascular
Club cells
On airway side of terminal bronchioles, have club like apical surfaces and no cilia or basal bodies
Functions of club cells (3 things)
- Protect bronchiolar epithelium
- Detoxification of harmful substances inhaled into lungs
- Act as a stem cell to regenerate bronchiolar epithelium
Microfold cells (3 things)
- Found in small intestine and very close to lymphatic nodules
- Folded extension that samples lumen by endocytosis
- Many pathogens exploit it as a portal of entry
Functions of microfold cells (3 things)
- Trap pathogens and underlying molecules
- Present to underlying dendritic cells that process material
- Present to lymphocytes and macrophages in basal pockets not linked to basement membrane (APC)
Functions of stereocilia (3 things)
- Inner ear: mechanosensing organelles of hair cells responding to fluid, motion and balance
- Epididymis & vas deferens: facilitate absorption of residual sperm body
- Contain actin and myosin filaments so could be involved in sperm movement?
Cell renewal rates- early stage (3 things)
- Normal mucus layer thickens
- Cilia die off
- Ciliagenesis
Cell renewal rates- chronic stage (4 things)
- Goblet and basal cells proliferate
- Club cells (metaplasia) or die
- Carcinogens induce mutations and malignancy
- Pneumocytes in alveoli die (fibroblasts lay down scar tissue, remaining type II proliferate)
Acute bronchitis (3 things)
- Cough and mucus production (narrowing of lung airways)
- Breathlessness less than 3 months (inflammation)
- Later stage: increased risk of respiratory diseases
Chronic bronchitis (2 things)
- Chronic inflammation more than 3 months or more during a 2 year period
- Start of irreparable damages to bronchioles and alveoli
Emphysema (4 things)
- Shortness of breath
- Permanent widening of airspaces distal to terminal bronchiole without fibrosis (destruction of air sacs)
- Damage to air sacs
- Loss of recoil and permanent changes to size of alveoli
What is COPD?
Umbrella condition that includes both emphysema and chronic bronchitis
Asthma (6 things)
- Wheeze, shortness of breath, chest tightness & cough
- Variable expiratory airflow limitation
- Often has a trigger
- Bronchospasm (tightening of smooth muscle)
- Obstruction from mucus
- Narrowing of conducting airways
