respiratory system Flashcards
what is inhalation
route of exposure
respiratory toxicology is _
Toxic responses of the cells of the respiratory tract, regardless of exposure route (may be inhalation or systemic, parent compound or metabolite)
what are the compound of interest in pheumotoxicology
occupational & environmental chemicals
therapuetic agents
what is the structure & function of the lungs
Nasopharangeal region = Nasal cavity, Pharynx and laynx
Trachea and Bronchi which is the conducting airway
Lower respiratory tract = trachea, primary bronchi and lungs
Respiratory bronchioles and alveoli = gas exchange regions
why os the respiratory tract susceptible to toxicty
- Highly perfused (Lung receives 100% of right side cardiac output, Exposed to systemic toxins and their metabolites)
- Exposed to air (Defence mechanisms)
- Highly complex tissues, numerous cell types
- Local xenobiotic metabolism
the air leaving the nasal cavity is
warm, moist, clean, turbulence free
the nasopharyngeal contains _ mucosa
olfactory
contains specialised epithelium which is responsible for the sense of smell
what is the structure of the olfactory mucosa
the olfactory mucosa is high in the nasal cavity and coverted in a mucus layer
- olfactory receptor cells are located in the olfactory epithelium.
- columnar epithelial cells, olfactory stem cells and the cribriform plate separates the olfactory bulb and the mucosa
- nerve fibre are within the bulb which linkeds to the olfactory tract
Can the olfactory mucosa be used for drug transport
- Recent research suggests that the olfactory mucosa is a realistic route for delivery of therapeutics
- Toxicological route = Some evidence in experimental animals that some metals (when inhaled) can translocate into CNS via the olfactory cells, but not others
how would the nasopharyngeal region be described
vascularised mucous epithelium
- large particles filtered out by nostril hairs
- water soluble molecules absorb
- nasal squamous cell carcinoma in long term inhalation studies in rats with HCHO
- perforated nasal septum with chromium (VI)
what is the pharynx
First recognisable tube of the respiratory system. Halfway down there is an opening in the wall of the pharynx which connects to the middle ear. This is called the Eustachian tube and serves to allow pressure changes to be communicated to the ear so that the eardrum can maintain the correct tension
What is formaldehyde and what is caused by inhalation
a common chemical, found primarily in adhesive or bonding agents for many materials found in households and offices, including carpets, upholstery, particle board, and plywood paneling.
The release of formaldehyde into the air may cause health problems, such as coughing; eye, nose, and throat irritation; skin rashes, headaches, and dizziness.
what is the trachea
10cm tube which extends from the larynx
lined with classical psuedo stratified ciliated colomnar epithelium which is risk in goblet cells
how does mucus work in the cilia
bathes the surface of the cilia which beat regularly and move the cilia up the trachea. Any particulate matter that has got through the upper defences will (hopefully) become trapped in this mucous and be moved upwards and expelled by coughing or swallowing. This defence mechanism is also known as the mucociliary escalator.
what is the lamina propria
made up of loose connective tissue; mucous and serous glands and some elastic fibres. It also maintains the characteristic C-shaped cartilage rings which are connected at the anterior of the tube by smooth muscle. These rings serve to maintain an open airway and the smooth muscle allows for control of lumenal diameter.
what is the entire trachea encased in
adventitia of connective tissue
what tissue and cells are located in the thracheobronchial region
(conducting airways)
- smooth muscle – allow lumenal diameter control (salbutamol)
- Ciliated epithelial cells
- Mucous (goblet) and serous epithelial cells
- Club cells (non ciliated)
- nerves
- mucociliary escalator
how does the smooth muscle work to change the dilation of the bronchiole
Parasympathetic nervous system: the vagal nerve releases acetylcholine which acts on the muscurinic receptors causing constriction of the bronchial smooth muscles.
what are club cells and what are they involved in
Cilia-free domed cells, abundant in the tertiary bronchioles. High content of xenobiotic metabolising enzymes. Progenitor cells for a variety of lung epithelial cells
Involved in: Protection (secretion of oxidases and anti-proteases and antimicrobials)
Surfactant secretion (processing of the liquid liner to the lung)
Origin of the most common form of lung cancer
what are the cells involved in the alveoli region
Alveolar type I cells (type 1 pneumocytes)
Alveolar type II cells ( type 2 pneumocytes)
Interstitial cells
Macrophages
how are the two types of pneumocytes different
Type I = squamous, 0.15um, constitutes 95% of area for gas exchange
Type II = cuboidal, granules (for storing surfactant), only 5% of area for gas exchange but 60% of total cells.
Type II cells can differentiate into Type I cells.
what are the defense mechanism of the lungs
- Clearance of particles: (mucociliary escalator, phagocytosis [alveolar macrophages to lymphatics –> dissolution])
- Release of chemical mediators as protectants eg glutathione, protein
- Specific defences - immune system
what are the particle sizes found in the lungs
Nano = Ultrafine = < 100 nm (Conventional)
Nano = <10 nm (suggested by unique quantum and surface-specific functions)
Fine = 100 nm - 3 m
Respirable (rat) = < 3 m (max = 5 m)
Respirable (human) = < 5 m (max = 10 m)
Inhalable (human) = ~ 10 - 50 m
Aerosol particle size influences site of deposition =
- Interception: occurs with the larger particles actually being intercepted by the upper airways
- Inpaction: inertia moves the particle further down the airway and enter the bronchial region
- Sedimentation: deposition in the smaller bronchi, velocity is low
- Diffusion: important in the deposition of particles in the sub-micrometer size
