Lungs and Diaphragm Flashcards
Thoracic cavity
Region enclosed by the thoracic wall
Pleurae
Serous sacs surround the lungs
Visceral pleura lines lung
Parietal pleura lines walls of thoracic cavity
Visceral and parietal pleurae are continuous with each other
Visceral pleura
Lines surface of the lung
Closely adherent to the lungs and extends into lung fissures
Has visceral sensory innervation
Does NOT have somatic sensory (pain, temperature, touch) innervation
Parietal pleura
Lines walls of the thoracic cavity
Does HAVE somatic sensory (pain, temperature, touch) innervation by intercostal nerves and phrenic nerves
Pleuritis
Inflammation of the pleura
Can lead to adhesion of visceral and parietal layers, resulting in acute pain association with elevated activity
Pleural cavity
Potential space between the visceral and parietal pleurae
Normally contains only a thin layer of serous fluid, which acts as a lubricant, facilitating movement of lungs during respiration
Right and left pleural cavities are independent
Hydrothroax
Accumulation of fluid in pleural cavity
Pneumothorax
Accumulation of air in pleural cavity
Hemothorax
Accumulation of blood in pleural cavity
Costodiaphragmatic recess
With inspiration, lungs expand and recess decreases in area
With expiration, recesses enlarge again
Thoracentesis
Procedure to drain excess fluid or blood from pleural cavity
Following an intercostal nerve block, a needle is inserted into an intercostal space (avoiding the inferior border of the rib above and superior border of the rib below)
Good place to perform thoracentesis is the posterior aspect of 7-9 intercostal space. Needle will enter costodiaphragmatic recess, avoiding injury to lungs and abdominal organs
However, other locations can be targeted depending on the effusion
Lungs
Organ of respiration - function is to oxygenate blood
Pink color darkens over time with exposure to particulates in air
Due to elasticity, if thoracic wall is breached (knife, GSW, etc), the lung will shrink to 1/3 of its normal size (as result of a pneumothorax)
Anatomy of lung
Root - collection of structures entering and exiting the lung (pulmonary vessels and bronchi)
Apex - superior portion extending into the neck
Base - concave inferior portion adjacent to diaphragm
Right lung
3 lobes - superior, inferior, and middle
Horizontal fissure separates superior and middle
Oblique fissure separates inferior
Left lung
2 lobes - superior and inferior
Oblique fissure separates
Superior lobe has cardiac notch on anterior margin
Organization of trachea and bronchi
Trachea
Right and left main bronchi
Lobar bronchi
Segmental bronchi
Trachea
Inferior to larynx
Palpable at jugular notch due to cartilaginous rings
C shaped hyaline cartilages (open posteriorly because esophagus is there and will expand when eating)
Bifurcates at sternal angle (T4 / T5 level)
Carina - ridge of cartilage at the bifurcation
Right and left main bronchi
Extrapulmonary (outside the lungs)
Also supported by C shaped rings of cartilage
Right main bronchus is wider, shorter, and more vertical than left
Therefore, aspirated foreign objects are more likely to lodge in the right bronchus
Lobar bronchi
Each main bronchus divides into lobar bronchi
Intrapulmonary (within the lungs)
Right lung has 3 lobar bronchi
Left lung as 2 lobar bronchi
Segmental bronchi
Each lobar bronchi divides into segmental bronchi, which each correspond to specific bronchopulmonary segment
Bronchopulmonary segment
10 segments per lung
An area of the lung supplied by a segmental bronchus and a segmental branch of the pulmonary artery
Segments are separated by connective tissue, therefore a segment can be surgically resected if needed
Pulmonary veins are intersegmental - run within the connective tissue that separates the segments
Pulmonary vessels
Pulmonary trunk
Pulmonary arteries
Pulmonary veins
Pulmonary trunk
Exits right ventricle of heart and divides into right and left pulmonary arteries, when then enter lungs
Pulmonary arteries
Carry O2 poor blood from heart to lungs for oxygenation
Each pulmonary artery divides into lobar and segmental arteries, running parallel with the bronchi
Pulmonary veins
Carry O2 rich blood from the lungs to left atrium of the heart
2 pulmonary veins bilaterally (vs. 1 artery bilaterally)
Lie in intersegmental connective tissue separating the bronchopulmonary segments and do NOT course with arteries and bronchi
Bronchial arteries
Carry O2 rich blood to the tissues of the lung itself
Most are branches off the thoracic aorta
Bronchial veins
Return O2 poor blood from the tissues of the lung to the azygos system or intercostal veins
Innervation of the lungs
Innervation of the lungs is via pulmonary plexus with contributions from vagus nerve (CN X) and pulmonary nerves
All organs are innervated by the AUTONOMIC NS
Remember: autonomic NS includes sympathetic (fight or flight) and parasympathic (rest and digest)
Parasympathetic - bronchoconstriction
Sympathetic - bronchodilation
Parasympathetic innervation of lungs via vagus nerve (CN X)
Achieves bronchoconstriction of smooth muscle of bronchial tree
Parasympathetic:
Preganglionic cell bodies - brain
Preganglionic fibers - vagus nerve
Postganglionic cell bodies - wall of target organ (lung)
Postganglionic fibers - wall of target organ (lung) and are very short in length
Sympathetic innervation of lungs
Achieves bronchodilation of smooth muscle of bronchial tree
Sympathetic:
Preganglionic cell bodies - lateral horn of thoracic spinal cord
Preganglionic fibers - ventral root, spinal nerve, ventral ramus, white ramus communicans, sympathetic trunk
Postganglionic cell bodies - upper thoracic paravertebral ganglia
Postganglionic fibers - pulmonary nerves
Diaphragm
Separates the thoracic and abdominal cavities
Composted of skeletal muscle surrounding C shaped central tendon
Pericardium surrounding heart is attached to central tendon
2 domes - right sits higher than left due to liver
Attachments to the diaphragm
All are peripheral -
Xiphoid process
Costal margin
Ribs 11-12
Lumbar vertebrae (via right and left crura)
Openings in the diaphragm
I ate 10 eggs at 12
Inferior vena cava (caval opening) at T8 - goes through central tendon
Esophagael hiatus at T10 - for esophagus and vagus nerve (CN X)
Aortic hiatus at T12 - for aorta, thoracic duct, and azygos vein
Sensory innervation for diaphragm
Primary phrenic nerves
Peripherally, via intercostal nerves
Motor innervation for diaphragm
Phrenic nerves - ventral rami C3, 4, and 5 keep the diaphragm alive
Primary muscle of inspiration
Phrenic nerves
Phrenic nerves course along lateral mediastinum and anterior to roots of lungs
Phrenic nerves independently innervate left and right domes
Lesion of a phrenic nerve
This paralyzes the corresponding side of the diaphragm
X-ray during inspiration will show a depressed (active side) and raised (paralyzed side) of the diaphragm
Diaphragm is primary muscle of inspiration
When diaphragm contracts, the domes descend and flatten, increasing vertical dimension of thoracic cavity. This also decreases volume of abdominal cavity, which increases abdominal pressure.
Diaphragm relaxes during expiration, allowing domes to rise.
Basic principles of respiration
Inspiration
- To draw air into lungs, thoracic pressure must be less than atmospheric pressure
- An increase in the volume of the thoracic cavity will decrease the thoracic pressure
Expiration
- To expel air from the lungs, thoracic pressure must be higher than atmospheric pressure
- A decrease in the volume of the thoracic cavity will increase the thoracic pressure
Movements of thorax during inspiration
Contraction (flattening) of the diaphragm causes the abdominal contents to be forced down, thereby increasing the vertical dimension of the thorax
Contraction of muscles that elevate the ribs (external intercostals) expands the thoracic cavity transversely (laterally) as a “bucket handle” movement and anteroposteriorly as a “pump handle” movement
During forceful inspiration, may also use pectoral muscles
Movements of thorax during expiration
Thoracic cavity reduces in size primarily due to relaxation of the diaphragm and elastic recoil of lungs
During forceful expiration, abdominal muscles are recruited to compress abdominal viscera upward, expelling air from lungs
