9.14.11+-+Lungs

=Lungs=

Pleural cavities are the two spaces within the thorax that flank the mediastinum and enclose the lungs. The left is slightly smaller than the right due to the heart. The pleural cavities are roughly 4-sided pyramids with the lateral edge of the base tilted inferiorly**.** Superior tip is called the pleural cupula and is lined by the cervical pleura. The cupula is at the level of the clavicle near the base of the neck. Inferior base is in contact with the diaphragm muscle, called "diaphragmatic pleura". The posterior, lateral and anterior walls contact the thoracic cage and parietal pleura is called the c ostal pleura. Medially, the pleural cavities are called the "mediastinal pleura". 2/3 of the way up is the hilum. The pleural cavities are lined by a mesothelium (squamous epithelium) called "parietal pleura". Deep to the parietal pleura and on the surface of the lungs themselves is the "visceral pleura". These layers are nearly frictionless together, which allows respiration. The hilum (root) of the lungs is where ALL the vessels carrying blood, air and lymph transverse between the mediastinum and the lungs. Only connection for lungs to anything. Pleura covering hilum is transitional between parietal and visceral pleura.
 * 1) Describe the anatomy of the pleura and pleural cavities.**
 * Name those structures that serve as the walls of the pleural cavities.**
 * Describe the difference between the parietal pleura and visceral pleura and name the different parts of the parietal pleura.**
 * Describe the hila of the lungs and name the structures found within the hila.**

Under the mediastinal pleura are the vagus nerve (CN X) and the phrenic nerve (C3, C4, C5). The vagus nerve innervates visceral motor and visceral sensory innervation of the heart, gut etc and the lungs. It is just posterior to the hilum of the lungs. Phrenic nerve provides somatic sensory and somatic motor fibers to the diaphragm (CRITICAL FOR BREATHING!). Is just anterior to the hilum.
 * 2) Name and locate the two major nerves which lie just under the mediastinal pleura. Describe the roles of these two nerves with regards to the functions of the lung.**

The medial surface of the lungs contains several indentations corresponding to important structures. Right Lung: groove for the esophagus (runs sup/inf posterior to hilum) groove for superior vena cava (runs sup/inf anterior to hilum) and groove for the arch of the azygos vein (superior to the hilum). Left Lung: groove of the aorta (arches sup. over hilum and passes anterior to hilum on descent). Large cardiac impression from apex off the heart. Right Lung has 3 lobes: superior right lobe (horizontal fissure) middle right lobe (diagonal fissure) and inferior right lobe. Left Lung has 2 lobes: superior left lobe (oblique fissure) and inferior left lobe.
 * 3) Name the structures that cause the indentations evident on the surface of the right and let lungs.**
 * State how many lobes each lung has and name the fissures that separate these lobes.**

Expansion of lungs during inspiration is driven by negative pressure in the pleura space. Inspiratory muscles raise the ribs and lower the diaphragm. Quiet expiration is driven by elastic recoil of the lungs and relaxation of the diaphragm. Active expiration is carried out by muscles lowering the ribs. Air in the pleura cavity. Since inspiration uses hydrostatic pressure (relying on incompressible liquids) this is very dangerous. During a pneumothorax, increases in pleural space have little to no affect on lung expansion. Primary muscle is the diaphragm (phrenic n [C3, C4, C5]) a flat dome shaped muscle attached to inferior base of lungs. Contraction causes dome to descend, pulling down diaphragmatic pleura. In addition, the external intercostal muscles and interchondral gegions of the interal intercostal muscles. These muscles raise the ribs. Quiet expiration occurs by passive recoil of lungs due to natural elasticity of lungs. Active expiration involves internal intercostal muscles (except near midline) as well as various abdominal muscles which lower the ribs.
 * 4) Describe how inspiration and expiration occurs.**
 * What is a pneumothorax**
 * What muscles are involved in inspiration**
 * What muscles are involved in expiration**

Air enters the mouth and travels down the trachea. At the level of the sternal angle, trachea bifurcates to form primary bronchi. Inferior portion forms wedge called the carina, important radiographic landmark. Each of the primary bronchi enter the lungs. The secondary bronchi split again to form 5 secondary bronchi (one to each lobe). A PALM, SAM, LP Superior Lobe Apical bronchus Posterior bronchus Anterior bronchus Medial Lobe Lateral bronchus Medial bronchus Inferior Lobe Superior bronchus Anterior-basal bronchus Medial-basal bronchus Lateral-basal bronchus Posterior-basal bronchus precise terminology: _ tertiary bronchus of the lobe of the lung ASIA ALPS Superior Lobe Apicoposterior bronchus Anterior bronchus Superior bronchus Inferior bronchus Inferior Lobe Superior bronchus Anteromedial-basal bronchus Lateral basal bronchus Posterior basal bronchus precise terminology: _ tertiary bronchus of the lobe of the lung
 * 5) Name the primary, secondary and tertiary bronchi of the right and left lungs.**
 * Name the Tertiary Bronchi of the Right Lung**
 * Name the Tertiary Bronchi of the Left Lung**

The bronchial arterial supply (minor one) and pulmonary arterial supply (major one). Bronchial artery supply (1 on right, 2 on left) branch from proximal portions of descending thoracic aorta and carry oxygenated blood to subserve trachea, primary and secondary bronchi. Pulmonary arteries carry non-oxygenated blood directly from right ventricle of the heart and subserve tertiary bronchi, bronchioles and most of lung tissue. Right and left bronchial arteries arise from a bifurcation of the pulmonary trunk, with the right pulmonary artery passing inferior to the arch of the aorta. Pulmonary arteries enter hila of the lungs and branch following the airways. The pulmonary veins (2 on right, 2 on left) follow a similar branching pattern, eventually coalescing into 4 pulmonary veins into the hila of the lungs, which dump their venous contents directly into the left atrium.
 * 6) Name the two sources of arterial blood for the bronchi and lungs, and describe the anatomy of these two sources.**

Lymph nodes drain through channels alongside the bronchioles and bronchi. Lymph node clusters occur near the hila of the lungs (pulmonary nodes), surrounding the carina (carinal nodes), and alongside the trachea (tracheal nodes)
 * 7) Describe the lymphatic drainage of the lungs, and name the locations of the relevant lymph nodes.**



Visceral afferent fibers carry information such as irritation to the CNS via the vagus nerve. The visceral sympathetic axons arise from neuronal cell bodies located within the thoracic paravertebral sympathetic chain and directly innervate arteriolar smooth muscle cells within the lung. Release of norepinephrine from the sympathetic terminals causes vasoconstruction. Activation of sympathetic nervous system also indirectly causes relaxation of bronchiolar smooth muscle cells via circulating levels of norepinephrine and epinephrine released by the adrenal medulla. This is basis for albuterol. Axons arise from neuronal cell bodies located in terminal ganglia located within the peribronchial plexi of the lungs themselves, which are in turn innervated by pre-ganglionic neurons from the brain stem which travel the vagus nerve. Axons release acetylcholine, which activates bronchiolar smooth muscle cells (causing bronchiolar constriction) and relaxes arteriolar smooth muscle cells (causing vasodilation). Production of phlegm requires fluid transfer from the blood to the secretory cells. During stressful situation, one desn't want buildup of phlegm and coughing.
 * 8) Describe the sensory innervation of the lungs**
 * Sympathetic Innervation of Lungs**
 * Parasympathetic Innervation of Lungs**
 * Why does Sympathetic Nervous System reduce blood to the lungs?**