Outline the structure and function of the ribs.
- The rib cage protect the lungs and heart.
- You can locate the 2nd rib by finding the sternal angle between the manubrium and the sternum. The 2nd rib attaches at this point
- Ribs can be counted inferiorly
- The inferior aspect of each lung is curved upwards because it lies on top of the domed diaphragm.
What are the two types of membranes in the respiratory system?
- 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.
Normally the two pleural layers are in close apposition with an exceedingly thin layer of lubricating fluid between them.
The pleural cavity (i.e. the space between the two layers) may however fill with some substances; identify and describe them.
- Air (pneumothorax)
- Blood (haemothorax)
- Pus (empyema)
- A watery transudate or exudate (pleural effusion)
Describe how fluid can 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.
- Below the 7th intercostal space there is a danger of penetrating the diaphragm.
Identify the components of the respiratory tract.
Identify the features of the surface anatomy of the lungs in anterior view.
- Superior lobe of right lung
- Inferior lobe
- Middle lobe
- Superior lobe of left lung
- Primary bronchus
- Secondary (lobar) bronchus
- Tertiary (segmental) bronchus
The conducting portion of the respiratory tract is from the nasal cavity to the terminal bronchioles. Identify the structures included.
- Nasal cavity
- Primary bronchi
- Secondary bronchi
- Terminal bronchioles
The respiratory portion of the respiratory tract is from the respiratory bronchioles to the alveoli. Identify the structures included.
- Respiratory bronchioles
- Alveolar ducts
Categorise the components of the respiratory system into extrapulmonary and intrapulmonary components.
- Extrapulmonary components:
I. Nasal cavity
V. Primary bronchi
- Intrapulmonary components:
I. Primary bronchi
II. Secondary bronchi
IV. Terminal bronchioles
V. Respiratory bronchioles
VI. Alveolar ducts
What structural change does one observe in the respiratory tract?
The walls of the passageways become thinner as their lumens decrease in diameter.
Outline the epithelial changes in the respiratory epithelium.
- Pseudostratified epithelium, with cilia and goblet cells, lines the airways from the nasal cavity to the largest bronchioles - nasal cavity, pharynx, larynx, trachea, primary bronchi, secondary bronchi
- Simple columnar epithelium with cilia and Clara cells but no goblet cells - bronchioles and terminal bronchioles
- Simple cuboidal epithelium with Clara cells and a few sparsely scattered cilia - respiratory bronchioles and alveolar ducts
- Simple squamous/type 1 (+ septal,type 2 cells) - alveoli
Identify the respiratory airways of the head and neck.
Outline the olfactory and non-olfactory regions of the nasal cavities.
- Non-olfactory regions
I. Pseudostratified ciliated epithelium. Mucous glands and venous sinuses in lamina propria.
II. Venous plexuses swell every 20-30 minutes, alternating air flow from side to side, preventing overdrying.
III. Arterial blood flow warms inspired air.
IV. Patency maintained by surrounding cartilage or bone.
- Olfactory regions - Particularly thick pseudostratified columnar epithelium, without goblet cells, located in posterior, superior region of each nasal fossa.
What are the components of the larynx?
- False vocal cord
- True vocal cord
Outline the structure and function of the larynx.
- The ventricular folds of the larynx are lined by pseudostratified epithelium and contain mucous glands and numerous lymph nodules
- The ventricles, together with the ventricular folds, contribute to the resonance of the voice
- The vocal cords help stop foreign objects from reaching the lungs
- Each vocal cord, of the larynx, is line by stratified squamous epithelium and contains:
I. A vocal ligament (large bundle of elastic fibres, running front to back
II. A vocalis muscle (bundle of skeletal muscle)
Outline the structure of the trachea.
- The trachea divides into two primary bronchi in the mid-thorax.
- Primary bronchi have a histology similar to that of the trachea, but their cartilage rings and spiral muscle completely encircle the lumen.
Outline COPD in relation to the tracheal epithelium.
- In Chronic Obstructive Pulmonary Disease, there is goblet cell hyperplasia, a smaller proportion of cilia cells and hypertrophy of the submucous glands.
- Hence, there is more mucus and fewer cilia to move the mucus.
Outline cystic fibrosis.
- 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. (due to misfolded protein)
- As a result, chloride ion transport across the membrane is substantially compromised.
- 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.
Outline the appearance of a bronchus and bronchioles in an H&E stained micrograph.
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.
Why are Clara cells important?
Clara cells also secrete abundant Clara cell protein (CC16):
- A measurable marker in bronchoalveolar lavage fluid
- A measurable marker in serum
- If lowered, then lung damage
- If raised, then leakage across air-blood barrier
Outline the causes and effects of bronchoconstriction and relate it to 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.
- Such bronchoconstriction can become excessive in asthma and cause more difficulty with expiration than inspiration (during expiration the bronchial walls are no longer held open by the surrounding alveoli).
Identify the openings of the alveoli.
Alveoli can open into:
- A respiratory bronchiole
- An alveolar duct
- An alveolar sac
- Another alveolus (via an alveolar pore)
Describe the structure of alveoli walls.
I. Have abundant capillaries
II. Are supported by a basketwork of elastic and reticular fibres.
III. Have a covering composed chiefly of type I pneumocytes.
IV. have a scattering of intervening type II pneumocytes.
- Destruction of alveolar walls and permanent enlargement of air spaces which 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.
- Hallmark sign: pursed-lip breathing.
- Inflammation of the lung caused by bacteria. The lung consolidates as the alveoli fill with inflammatory cells.
- Most common causative bacterium is Streptococcus pneumoniae. Others are: Haemophilus influenzae Staphylococcus aureus Legionella pneumophila & Mycoplasma pneumoniae.
Outline the effects of lung cancer.
- Lung cancer can cause a paralysis of one side of the diaphragm, if tumour impinges on the left or right phrenic nerve.
- Cancer in the apex of the lung can impinge on the brachial plexus, causing wasting of muscles in the lower arm.
- 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, decreased sweating).
- 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.
Define and explain the following terms:
- Surface tension
- Cohesion refers to the attraction of identical molecules towards each other.
- Water molecules have strong cohesive forces thanks to their ability to form hydrogen bonds with one another.
- Cohesive forces are responsible for surface tension, the tendency of a liquid’s surface to resist rupture when placed under tension or stress.
- Water molecules at the surface (at the water-air interface) will form hydrogen bonds with their neighbours, just like water molecules deeper within the liquid.
Outline pleural anatomy.
- Lungs are surrounded by thin tissue called the pleura, a continuous membrane that folds over itself.
I. Parietal pleura lines the chest wall
II. Visceral pleura covers the lung
- Normally, the two membranes are separated only by lubricating pleural fluid.
I. Fluid reduces friction, allowing the pleura to slide easily during breathing.
I. Fluid provides the surface tension needed to prevent the lung from recoiling and collapsing.
Outline pleural physiology in terms of the pleura space.
- Lungs contain a lot of elastin.
- The area between the pleura is called the pleura space.
- Normally, vacuum (negative pressure) in the pleural space keeps the two pleurae together and allows the lung to expand and contract.
- During inspiration, the intrapleural pressure is approximately -8cmH20 (below atmosphere).
- During exhalation, intrapleural pressure is approximately -4cmH20 (below atmospheric).