Lecture 12: Thorax 2 - Cavity Flashcards
Define Thoracic Cavity: What does it contain?
THORACIC CAVITY: the space enclosed by the thoracic wall, containing the mediastinum and the left and right pulmonary cavities
Define pulmonary cavity
Paired (left/right); located laterally in completely separate compartments containing the lungs and pleura
Define mediastinum location, and what important organs does it contain?
Unpaired; located centrally; important contents include the heart, great vessels, trachea, esophagus
Identify the indicated parts of the thoracic cavity
Identify the bounaries of the mediastinum
superior / inferior / anterior / posterior / lateral
- SUPERIOR: superior thoracic aperture
- INFERIOR: thoraco-abdominal diaphragm
- ANTERIOR: sternum and costal cartilages
- POSTERIOR: thoracic vertebrae
- LATERAL: left/right pulmonary cavities
Explain the locations of the superior and inferior mediastinum
SUPERIOR MEDIASTINUM: located between the superior thoracic aperture and a transverse plane through the sternal angle
INFERIOR MEDIASTINUM:
located between a transverse plane through the sternal angle and the thoraco-abdominal diaphragm
Use definitions of superior and inferior mediastinum to explain their locations in the diagram
SUPERIOR MEDIASTINUM: located between the superior thoracic aperture and a transverse plane through the sternal angle
INFERIOR MEDIASTINUM:
located between a transverse plane through the sternal angle and the thoraco-abdominal diaphragm
What are the 3 subdivisions of the inferior mediastinum?
Anterior, Middle and Posterior
Define the locations of the anterior, middle and posterior inferior mediastinum.
- Anterior mediastinum: between the sternum and the pericardium surrounding the heart
- Middle mediastinum: between the anterior mediastinum and the posterior mediastinum
- Posterior mediastinum: between the pericardium and the thoracic vertebrae
Identify indicated features of thoracic cavity
Identify indicated features
What are the contents of the superior mediastinum? 4 structures
- Trachea
- Esophagus (extends from superior to posterior mediastinum)
- Arch of the aorta
- Thymus (extends from superior to anterior mediastinum
Contents of the anterior mediastinum
Thymus (superior to anterior)
Contents of the middle mediastinum
- Pericardium
- Heart and associated structures
Contents of posterior mediastinum? 3 structures
- Esophagus
- Descending aorta
- Azygos venous system
What three subsections of the mediastinum comprise the inferior mediastinum?
Anterior, Middle and Posterior Mediastinum comprise the inferior mediastinum
Define pleural sac
PLEURAL SAC: the tissue that invests and encloses each lung; made up of pleura
Define pleurae, and what are the three layers?
Pleurae: (plural, singular = pleura) the membranous layers that surround the lung, forming the pleural sac
- Parietal Pleura
- Visceral Pleura
- Pleural Cavity
Define Parietal Pleura, and what structures it adheres to.
- PARIETAL PLEURA: outer layer; lines the pulmonary cavities; adheres to the thoracic wall, mediastinum, and diaphragm
What are the four named parts of the parietal pleura?
- Costal part (costal pleura)
- Mediastinal part (mediastinal pleura)
- Diaphragmatic part (diaphragmatic pleura)
- Cervical part (cervical pleura)
Parietal Pleura: Where is the costal part?
lines internal surfaces of the thoracic wall
Parietal Pleura: Where is the mediastinal part?
lines the lateral aspects of the mediastinum
Parietal Pleura: Where is the diaphragmatic part?
: lines the superior surface of the thoraco-abdominal diaphragm on either side of the mediastinum
Parietal Pleura: Where is the cervical part?
lines the superior most portion of each lung; extends into the root of the neck
Define Visceral Pleura
- VISCERAL PLEURA: inner layer; covers the lungs; adheres to all the surfaces of the lungs
Define pleural cavity
- PLEURAL CAVITY: the potential space between the parietal and visceral pleurae
What fluid is present in the pleural cavity, and its function?
The pleural cavity contains a thin layer of serous fluid (pleural fluid), which lubricates the pleura and facilitates movement
What keeps the surface of the lung pressed against the thoracic wall?
Surface tension in the pleural fluid keeps the surface of the lung pressed against the thoracic wall
When can the pleural cavity become a REAL space?
The pleural cavity can become a real space (not a potential space) due to pathology or injury
What are pulmonary recesses, and what are they important for?
PULMONARY RECESSES: areas in which the pleural cavity is enlarged (i.e., because the lungs do not completely fill the pulmonary cavities)
They are potential spaces containing only a small amount of pleural fluid
Important for accommodating changes in lung volume during breathing
What are the 2 pulmonary recesses?
COSTOMEDIASTINAL RECESS
COSTODIAPHRAGMATIC RECESS
What is the location of the costodiaphragmatic recess?
the pleura recess that lies inferiorly between the thoracic wall and the thoraco-abdominal diaphragm (i.e., surrounding the upward convexity of the thoraco-abdominal diaphragm and the thoracic wall)
What is the location of the costomediastinal recess?
the pleura recess that is located posterior to the sternum where the mediastinal pleura and costal pleura contact each other
When will substances accumulate in pulmonary recesses and what three diseases can it cause?
As a consequence of disease or trauma, substances may accumulate in the pleural recesses (especially the costodiaphragmatic recess), resulting in one or more of the following conditions:
- Hemothorax
- Pneumothorax
- Hydrothorax
Define hemothorax
an accumulation of blood in the pleural cavity
Define pneumothorax
an accumulation of air in the pleural cavity
Define hydrothorax
an accumulation of pleural fluid in the pleural cavity
What are the lungs?
LUNGS: the primary organs of respiration whose function is to oxygenate blood by bringing it into close contact with inspired air
Define the Apex of the Lung and Base of the Lung
- Apex of the lung: the superiormost area, which extends superiorly into the neck
- Base of the lung: the concave, inferior portion adjacent to the diaphragm
What are the three lobes of the right lung, and the 2 fissures?
THREE LOBES: SUPERIOR/UPPER, MIDDLE, INFERIOR/LOWER
TWO FISSURES:
* OBLIQUE: separates the inferior lobe from the
middle and superior lobes
- HORIZONTAL: separates the middle lobe from
the superior lobe
What are the 4 impressions of the right lung?
Impressions:
i. Impression for the superior vena cava
ii. Impression for the inferior vena cava
iii. Impression for the azygos vein
iv. Impression for the esophagus
What are the 2 lobes of the left lung, and the one fissure?
TWO LOBES: SUPERIOR/UPPER, INFERIOR/LOWER
ONE FISSURE:
* OBLIQUE: separates the superior lobe from inferior lobe
What is the lingula, and which lung is it on?
The lingula of the left lung is a medial extension of the lung that lies anterior to the mediastinum; it is homologous with the middle lobe of the right lung
What is the notch and the impression on the left lung?
i. Cardiac notch: for the anterior surface of the heart (primarily the left ventricle)
ii. Aortic impression: impression for the ascending aorta and thoracic aorta
Define bronchopulmonary segment.
How many are in each lung?
- Bronchopulmonary segment: one segment of a lung and one segmental branch of the bronchi and pulmonary artery
- Both lungs consist of ~10 segments
What is each pulmonary segment supplied by
- Each segment is supplied by a segmental branch of the respective pulmonary artery and by a segmental branch of the bronchus
Are different bronchopulmonary segments independent from one another?
Yes, bronchopulmonary segments are anatomically and functionally independent of other segments
What is the Hilum of the lung?
- HILUM OF THE LUNG: area on the medial surface of the lung at which structures enter/exit
What is the root of the lung, and its 3 associated structures?
- ROOT OF THE LUNG: all the structures that enter/exit the lungs
1) MAIN BRONCHUS (one on each side)
2) PULMONARY ARTERY (one on each side)
3) PULMONARY VEINS (two on each side)
What is the pulmonary ligament?
- PULMONARY LIGAMENT: double layer of parietal pleura located directly inferior to the hilum/root
Identify the indicated structures
Describe the route of pulmonary circulation beginning from the heart to pulmonary trunk.
- Deoxygenated blood enters the RIGHT ATRIUM via the superior and inferior vena cava
- Blood then travels from the right atrium to the RIGHT VENTRICLE, then to the pulmonary trunk
Describe route of pulmonary circulation from the pulmonary trunk into the segmental arteries of the lung.
Pulmonary trunk: convey deoxygenated blood from the right ventricle
- In the mediastinum, the pulmonary trunk divides into the right and left pulmonary arteries
- The right and left pulmonary arteries course toward the hilum of the lung, where they divide into lobar arteries, each of which serves a single lobe of the lung (see below)
- Within the lung, each of the lobar arteries divides into segmental arteries, each of which serves a single segment of the lung (see below)
Once blood is oxygenated, how does it return to the heart?
Tributaries of the pulmonary veins course between (and drain) segments (see below).
These tributaries converge to form pulmonary veins, which convey oxygenated blood from the lungs to the left atrium (NOTE: there are typically two pulmonary veins on
either side)
What is the function of the trachea and bronchial tree?
The trachea and bronchial tree convey inspired air into the lungs and expired air out of the lungs (TRACHEOBRONCHIAL TREE)
Describe structure and location of trachea
TRACHEA: a fibrocartilaginous tube consisting of C-shaped rings (courses through neck and into mediastinum)
Where are the R/L main bronchi?
R/L MAIN BRONCHI: in the mediastinum, the trachea divides into the right and left main bronchi, which extend into the respective lungs
What do the right and left main bronchi divide into at the hilum?
lobar bronchi (each serving one lobe of the lung), which divide into segmental bronchi (each serving one segment of the lung)
What do the airways divide into after the segmental bronchi?
- Each segmental bronchus divides into terminal bronchioles, which, in turn, give rise to respiratory bronchioles
What does each respiratory bronchiole lead to?
Each respiratory bronchiole opens into several alveolar ducts, which end in alveolar sacs, into which clusters of alveoli (plural; singular = alveolus) open
What maintains the volume of the lungs?
The volume of the lungs is maintained by the surface tension in the pleural fluid in the pleural cavity, which presses the parietal pleura against the thoracic wall
Explain how increases / decreases in thoracic cavity dimensions affects volume and pressure.
- Increases/decreases in thoracic cavity dimensions cause increases/decreases in volume
- Increases in volume cause decreases in pressure, and vice versa.
Why is air drawn into the lungs?
The increased volume decreases pressure below atmospheric pressure
Air travels from higher pressure to lower pressure, filling the lungs.
What muscles and structures contribute to increasing the size of thoracic cavity during inspiration?
a. Contraction/flattening out of the thoraco-abdominal diaphragm
b. Movements of the ribs
What muscles and structures contribute to decreasing thoracic cavity size during expiration?
a. Relaxation of the thoraco-abdominal diaphragm, which causes it to return to its dome shape
b. Movements of the ribs
When does expiration occur?
When the pressue increase from the decrease in size rises above atmostpheric pressure
Air will flow from higher pressue lungs, to lower pressure atmostphere
Which of the following statements about the differences between the right and left lungs is
correct?
A. Both lungs contain an oblique fissure
B. The left lung bears an impression for the azygos vein
C. The left lung contains an oblique fissure and a transverse fissure
D. The left lung has three lobes, and the right lung has two lobes
E. The right lung bears an impression for the thoracic aorta
A. Both lungs contain an oblique fissure
The pleural cavity is the potential space between which two structures?
A. Mediastinal pleura and diaphragmatic pleura
B. Parietal pleura and visceral pleura
C. Root of the lung and hilum of the lung
D. Thoracic wall and parietal pleura
E. Visceral pleura and lung tissue
B. Parietal pleura and visceral pleura
