Respiratory System Flashcards
Why is the inferior aspect of each lung curved up?
It lies on top of the domed diaphragm
What 2 types of membrane does the respiratory system contain and where are they found?
A MUCOUS MEMBRANE which lines the conducting portion of the respiratory tract. It bears mucus-secreting cells to varying degrees.
SEROUS MEMBRANES which line the pleural sacs which envelope each lung.
Other than lubricating fluid, what may fill the pleural cavity
Air (pneumothorax)
Blood (haemothorax)
Pus (empyema)
A watery transudate or exudate (pleural effusion)
How can fluid be drained from the pleural cavity?
Fluid can be drained from the pleural cavity by inserting a wide-bore needle through an intercostal space (usually the 7th posteriorly). Nowadays done under ultrasound guidance.
When fluid is drained, precisely where is the needle inserted and why?
The needle is inserted a fraction above the superior border of the lower rib, thus avoiding the intercostal nerves and vessels, which run along the inferior border of each rib.
Intercostal nerves and vessels run in the costal groove along the inferior border of each rib
Below the 7th intercostal space there is a danger of penetrating the diaphragm.
How could cancer cause paralysis of the diaphragm?
Cancer of the lung can cause a paralysis of one side of the diaphragm, if tumour impinges on the left or right phrenic nerve.
How could lung cancer cause wasting of the lower arm muscles?
Cancer in the apex of the lung can impinge on the brachial plexus, causing wasting of muscles in the lower arm.
Some wasting of muscles of the thenar eminence, and some wastage of interosseus muscles in the palm due to the encroachment of the apical lung tumour on C8 and T1 nerve roots of the brachial plexus
What could cause Horner’s syndrome?
Cancer in the apex of the lung can impinge upon nerves called the sympathetic trunk, giving rise to Horner’s Syndrome, characterized by miosis (a constricted pupil), ptosis (a weak, droopy, upper eyelid), and apparent anhidrosis (localised, decreasd sweating).
There are other benign causes of this syndrome.
How could cancer cause a hoarse voice?
Cancer of the lung can result in a hoarse voice as a result of impingement on the left recurrent laryngeal nerve, which loops under the aorta.
An aneurism of the aorta can also cause such hoarseness.
What are the two portions of the respiratory tract?
Conducting portion of respiratory tract = nasal cavity to bronchioles.
Respiratory portion of respiratory tract = respiratory bronchioles to alveoli.
Name the components of the respiratory system from exterior to interior
CONDUCTING PORTION Nasal cavity Pharynx Larynx Trachea Primary bronchi Secondary bronchi Bronchioles Terminal bronchioles
RESPIRATORY PORTION
Respiratory bronchioles
Alveolar ducts
Alveoli
Which components of the respiratory system are extra pulmonary and which are intrapulmonary
EXTRAPULMONARY Nasal cavity Pharynx Larynx Trachea Primary bronchi
INTRAPULMONARY (within lungs) Secondary bronchi Bronchioles Terminal bronchioles Respiratory bronchioles Alveolar ducts Alveoli
How do the thicknesses of the walls of the passageways compare to the diameter of the lumens
The walls become thinner as the lumen decrease in diameter
What kind of epithelium is found in the nasal cavity through to the largest bronchioles?
Psuedostratified epithelium with cilia and goblet cells
What type of epithelium is found in the smallest and terminal bronchioles?
Simple columnar with cilia and Clara cells but no goblet cells.
What kind of epithelium is found in the respiratory bronchioles and alveolar ducts?
Simple cuboidal with Clara cells and sparsely scattered cilia
What kind of epithelium is found in the alveoli?
Simple squamous/type 1 (+septal/type 2) cells
Describe the epithelium of the non-olfactory regions of the nasal cavity
Pseudostratified ciliated epithelium. Mucous glands and venous sinuses in lamina propria.
Describe the airflow in the non-olfactory regions of the nasal cavities
Venous plexuses swell every 20-30 minutes, alternating air flow from side to side, preventing overdrying. Arterial blood flow warms inspired air.
Patency maintained by surrounding cartilage or bone.
Describe the epithelium of the olfactory regions of the nasal cavities
Pseudostratified epithelium located in the posterior, superior region of each nasal fossa:
• particularly tall in olfactory region
• no mucus-secreting goblet cells
• cilia non-motile
• contains olfactory cells (bipolar neurons – one dendrite extends to the surface to form a swelling from which non-motile cilia extend parallel with the surface. These cilia increase surface area and respond to odours).
Describe the lamina propria of the olfactory regions of the nasal cavity
Lamina propria blends with submucosa.
• Serous glands (Bowman’s glands) flush odorants from the epithelial surface.
What forms an olfactory nerve?
Axons of olfactory cells join each other
Describe the structure and function of cartilage in the trachea and primary bronchi
In the trachea the cartilage is arranged in regularly spaced C-
shaped rings, (you can feel these under the skin of your throat). The trachealis muscle has some control over the tracheal lumen.
Primary bronchi have a histology similar to that of the trachea, but their cartilage rings and spiral muscle completely encircle the lumen.
In both cases the cartilage maintains the patency (open lumen) of the airway, and provides strength to the wall.
Rings of cartilage permit more flexibility than would a solid, hollow, cylindrical wall of cartilage.
What can happen to cartilage with ageing?
Ossification
Where is the trachealis muscle contained?
Fibroelastic membrane
How can choking occur?
Something caught in the oesophagus can seriously compromise the tracheal lumen.
There are two types of choking.
- one caused by a large static oesophageal bolus
- the other by something caught in the tracheal lumen.
What comprises secretions form the epithelium and submucosal glands
SECRETIONS from the epithelium (E) and submucosal glands (SM) of the trachea and bronchi contain mucins, water, serum proteins, lysozyme (destroys bacteria), antiproteases (inactivate bacterial enzymes). Lymphocytes contribute immunoglobulins (esp. IgA).
At what frequency do cilia beat?
Cilia beat at 12 Hz beneath a moveable, viscoelastic mucus blanket (5μm deep).
- These structures and their mode of action are often collectively referred to as the ‘mucociliary escalator’.
Describe the histology of the tracheal mucosa
Unusually thick basement membrane
Lamina propria rich in immune cells and with layer of elastic fibres
What type of epithelium lines the upper respiratory tract
Pseudostratified ciliated epithelium of this type lines most of the upper respiratory tract and is therefore named ‘respiratory epithelium’ (a misnomer? - no significant exchange of O2 and CO2)
What happens to cilia and goblet cells in COPD?
In chronic obstructive pulmonary disease (COPD) there is goblet cell hyperplasia, a smaller proportion of ciliated cells, and hypertrophy of the submucous glands……. (so, more mucus and fewer cilia to move the mucus).
What is missing from the apical membranes of the epithelial cells in cystic fibrosis and what consequences does this have?
An ion channel molecule named cystic fibrosis transmembrane regulator (CFTR) is not present in the apical membranes of the epithelial cells of cystic fibrosis sufferers.
As a result chloride ion transport across the membrane is substantially compromised.
CFTR moves chloride out, so sodium follows, so mucus is suffice to salty - water moves in to keep mucus hydrated
Consequently, in the respiratory tract, water does not leave the epithelium in sufficient quantities to adequately hydrate the secreted mucus. The mucus becomes viscous and can less readily be moved to the oropharynx for swallowing. Serious pulmonary infection often results.
Describe cartilage in he secondary and tertiary bronchi
C shaped
It maintains airway patency
Do bronchioles have cartilage?
No cartilage
No glands
What do pulmonary arteries and bronchial arteries carry?
Pulmonary - deoxygenated blood
Bronchial - oxygenated blood
What keeps bronchioles open?
No cartilage or glands
Surrounding alveoli keep lumen open
What can happen to bronchioles in patients with asthma
Absence of cartilage in walls of bronchioles can be problematic because it allows these air passages to constrict and almost close down when smooth muscle contraction becomes excessive.
In asthma an overreaction or hyper-responsiveness of the airways results in bronchospasm, which is excessive contraction or spasm of the bronchial smooth muscle. The airways themselves have also become inflamed with swelling of the bronchial mucous membrane (mucosa) and secretion of excessive thick mucus that is difficult to expel.
Such bronchoconstriction can become excessive in asthma and cause more difficulty with expiration than inspiration (the positive pressure in the alveoli facilitates the closure of the bronchioles).
The worst sign is the silent chest, in which the patient becomes so fatigued that they are unable to generate enough airflow to wheeze. This is an ominous sign of impending respiratory failure.
What are Clara cells?
As bronchioles get smaller, goblet cells give way to Clara cells, interspersed between ciliated cuboidal cells. Clara cells secrete a surfactant lipoprotein,
which prevents the walls sticking together during expiration.
Clara cells also secrete abundant Clara cell protein (CC16):
- a measurable marker in bronchoalveolar lavage fluid (if lowered then lung damage).
- a measurable marker in serum (if raised then leakage across air-blood barrier).
Why don’t terminal bronchioles have goblet cells
Airways too narrow for mucus
Do terminal bronchioles have alveolar openings?
No
Where are there openings onto alveoli?
Respiratory bronchioles have some openings onto alveoli
Duct walls have ubiquitous openings onto alveoli
Alveolar sac - composite air space onto which many alveoli open
Alveoli can open onto each other via alveolar pores
Describe the structure of alveolar walls
Alveolar walls:
- have abundant capillaries
- are supported by a basketwork of elastic and reticular fibres.
- have a covering composed chiefly of type I pneumocytes.
- have a scattering of intervening type II pneumocytes.
What types of cells make up the alveolar walls and what type of cells line their surface?
Type I alveolar cells (type I pneumocytes) (simple squamous) cover 90% of surface area and permit gas exchange with capillaries.
Type II alveolar cells (type II pneumocytes) (cuboidal) cover 10% of surface area and produce surfactant.
Numerous macrophages line alveolar surface (phagocytose particles).
Gas exchange occurs across blood-air barrier.
What is emphysema?
Destruction of alveolar walls and permanent enlargement of air spaces (due to loss of elastin). This can result from smoking, or alpha 1- antitrypsin deficiency.
Alveolar walls normally hold bronchioles open, allowing air to leave the lungs on exhalation. When these walls are damaged, bronchioles collapse, making it difficult for the lungs to empty. Air becomes trapped in the alveoli. Classic sign is barrel chestedness.
Disease described by Thomas Baillie in 1793 – illustrated lung was that of lexicographer, Samuel Johnson.
What is pneumonia?
Inflammation of the lung caused by bacteria. The lung consolidates as the alveoli fill with inflammatory cells.
Most common causative bacterium is Streptococcus pneumoniae but other pathogens can cause pneumonia.
