L1 - Respiratory Tract Flashcards
At what vertebral point does the trachea bifurcate?
T4-5 segment
What attaches the lungs to the mediastinum?
Pulmonary root and ligament.
What is the mediastinum?
The mediastinum is an area found in the midline of the thoracic cavity, that is surrounded by the left and right pleural sacs.
How do the left and right lungs differ in lobes?
Name the lobes and their fissures between?
Left lung has two lobes - superior and inferior. Separated by oblique fissure
Right lung has three lobes - superior, middle and inferior.
Inferior is separated from the other two by the oblique fissure. Superior and middle are separated by the horizontal fissure.
What is the carina?
Carina is the base of the bifurcation of the tracheal at level T4-5 into the left and right bronchi.
Irritation of the carina initiates the coughing reflex.
Describe the levels of bronchi splitting
Trache splits into left and right bronchi.
The primary bronchi split into lobar (secondary) bronchi, which split further into segmental (tertiary) bronchi.
What is the pulmonary hilum, and what structures do you find inside?
The hilum is formed by the pulmonary ligament and root. It encloses the following, listed from superior to inferior:
1 - Bronchus
2 - Pulmonary arteries (deoxygenated blood)
3 - Pulmonary veins (oxygenated blood)
Which veins drain the left and right lung?
Left lung is drained by the hemiazygous vein.
Right lung is drained by the azygous vein.
What significant impressions are made on the lungs and how can they be used to identify L vs R?
Aorta makes a large impression on the left lung (good for differentiation).
Subclavian artery and vein make impressions on both lungs at the apex.
Left ventricle and right atrium make impressions on the left and right lung respectively.
What is a functional unit of the lung?
Functional unit = tertiary bronchus + arterial branch.
Pulmonary artery carries deoxygenated blood to the alveoli, and veins drain the oxygenated blood away.
How do the parasympathetic and sympathetic nervous systems innervate the lungs?
Parasympathetic - Vagal branches (L+R): Bronchoconstriction and vasodilation
Sympathetic - T1-5 ganglia: Vasoconstriction (bronchodilation is controlled via endocrine)
Describe the levels of the ‘respiratory tree’ past the tertiary (segmental) bronchi.
Tertiary bronchi branch into bronchioles.
These bronchioles branch into terminal bronchioles.
Terminal bronchioles further branch into respiratory bronchioles.
Respiratory bronchioles branch into alveolar ducts, which terminate in alveolar sacs.
Describe the difference between ‘conducive’ and ‘respiratory’ parts of the lung system, and their differences in histology.
Trachea and bronchi = conductive tubes.
Histology - pseudostratified columnar cells with goblet cells and cilia for secretions and protection. Known as respiratory epithelium. Weird.
Bronchioles to alveoli = respiratory tubes
Histology - Transitioning from respiratory epithelium, to cuboidal (in terminal bronchioles) to simple squamous in alveoli. Simple squamous allows for best diffusion.
What are the two types of cells in alveoli and their functions?
Type 1 pneumocyte: 95% of alveolar surface. Simple squamous - responsible for gas exchange.
Type 2 pneumocyte: 5% of alveolar surface. More cuboidal in shape. Responsible for surfactant production.
What is the purpose of surfactant?
Surfactant functions to lower the surface tension at the air-fluid gas exchange in alveoli.
This is to prevent alveolar collapse at the end of expiration.
