Anatomy Lungs and Respiration
Into which two arteries does the Internal Thoracic artery divide near the 6th rib?
#4: Superior epigastric artery (supplies anterior abdominal wall) #5: Musculophrenic artery (passes through diaphragm)
What is the root of the lung?
A collection of structures (bronchus, pulmonary arteries and veins) that anchors the lung to the mediastinum. (Be careful not to confuse with the hilum, a structure that surrounds the root.)
What is the hilum of the lung?
An opening located centromedially in each lung through which the lung root (bronchus, pulmonary arteries and veins) pass. It is the only site of entrance or exit of structures associated with the lungs.
From what vessel do most of the posterior intercostal arteries branch?
Aorta
What is the name for the most superior point of the lung?
Apex
Name the four major divisions of the aorta from the heart to the common iliac artery.
Ascending aorta Aortic arch Descending Aorta (or Thoracic Aorta) Abdominal Aorta
Which three major arteries branch off superiorly from the aortic arch from most proximal to most distal?
Brachiocephalic trunk Left common carotid artery Left subclavian artery
Describe the Left Recurrent Laryngeal Nerve.
Branches off the left vagus nerve at inferior margin of aortic arch artery. Goes up groove btw. trachea and esophagus to supply larynx. (NOTE: Lecture slides say this nerve found ONLY on left side, but drawing here also shows a right recurrent laryngeal nerve.)
Which structures anchor the lungs medially to the mediastinum?
Bronchi, pulmonary blood vessels, nerves
Features of the pulmonary artery?
Carries deoxygenated blood from right ventricle to lungs (blue) Usually (not always) placed superiorly in hilum Can appear as one or two arteries depending on anatomy and how the artery was cut
Features of the pulmonary vein?
Carries oxygenated blood from lungs to left atrium of heart (red) See two veins per lung at root
Describe the vagus nerve (R and L branches).
Cranial nerve X Mixed nerve: parasympathetic efferents/somatic afferents to thoracic viscera
What is the name for the concave, inferior border of the lung?
Diaphragmatic surface
Secondary bronchi features
Divisions off main bronchi Each secondary bronchus supplies a single lobe of a lung
Tertiary bronchi features
Divisions off secondary bronchi Each tertiary bronchus supplies a bronchiopulmonary segment
Features of the trachea?
Flexible tube surrounded by C-shaped cartilaginous rings (allow food bolus to move freely down esophagus) Extends from level of C6 to level of T4/T5
Describe the phrenic nerve.
From anterior rami C3-C5 Splits into R and L phrenic nerve, passes anterior to lung root Mixed nerve (sensory and motor): innervates diaphragm, fibrous pericardium, parietal layer of serous pericardium
Describe the intercostal nerves.
From anterior rami T1-T11 Between interior intercostal muscles and innermost intercostal muscles, inferior to intercostal groove so not protected by rib. Mixed nerves: include motor innervation to thoracic wall muscles as well as sensory innervation from thoracic skin, pleura
What is unique about the branching of the first two posterior intercostal arteries?
Instead of branching off the aorta, they branch off the subclavian artery ==> costocervical trunk ==> supreme intercostal artery ==> intercostal arteries A1, A2 (C, D, and E in picture)
Which veins drain the muscles of the ribcage?
Intercostal veins
Which two veins merge to form the Brachiocephalic Trunk Vein?
Internal Jugular Vein Subclavian Vein
What major artery branches off the subclavian artery proximal to its origin (right or left), descends down the anterior side of the thorax, and can be seen running under the transversus thoracis muscle?
Internal Thoracic Artery
From which vessels do the anterior intercostal arteries branch?
Internal thoracic arteries
Name two morphological features that are unique to the left lung.
Lingula (tongue-like extension that sits over bulge of heart) Cardiac notch (allows room for heart)
What is the name of the single-cell thick epithelium that lines the pleural cavities?
Mesothelium
Name two morphological features that are unique to the right lung.
Middle lobe Horizontal fissure (separates superior and middle lobes)
Carina
Most inferior tracheal cartilage ring before bifurcation into main bronchi
Left main bronchus features
Narrower than right main bronchus More horizontal orientation Divides into two secondary bronchi (one for each lung); however, superior secondary bronchus quickly bifurcates again
Describe the pulmonary plexus.
Near bifurcation of trachea into bronchi Consists of anterior, posterior pulmonary plexuses Visceral efferents from vagus nerve (constrict bronchioles), sympathetic system (dilate bronchioles)
Features of the bronchi at lung root?
One main bronchus per lung (brown) Easily distinguished from blood vessels by surrounding cartilage
After the brachiocephalic trunk branches off the aortic arch, into which two arteries does the brachiocephaic trunk bifurcate?
Right Common Carotid Artery Right Subclavian Artery
What is serous fluid? What is its function?
Serous fluid is a lubricating fluid secreted by the pleura. Its function is to allow the visceral pleura and parietal pleura to glide easily over each other during breathing.
Bronchiole features
Smallest division of the bronchial tree; between tertiary bronchi and alveoli
Bronchopulmonary Segment
Smallest functionally independent region of a lung Has own blood supply, air supply (via its own tertiary bronchus) Smallest area of lung that can be isolated and removed Can fuse in left lung
Surface landmarks (anterior) for left lung
Superior Lobe: Superior to clavicle to rib 5/costal cartilage rib 6 Inferior Lobe: Safest to say laterally, at level of rib 6
Surface landmarks (anterior) for right lung
Superior Lobe: superior to clavicle to inferior to rib three Horizontal Fissure: Superior to rib four (intercostal space between rib 3 and 4) Middle Lobe: Level of Ribs 4 and 5, superior portion of costal cartilage rib 6 Inferior Lobe: Laterally, at level of bony rib 6 and 7
Into what structure do the brachiocephalic trunk veins (R and L) drain?
Superior Vena Cava
Name three morphological features the left and right lungs have in common.
Superior lobe Inferior lobe Oblique fissure (separates superior and inferior lobe)
Surface landmarks (posterior) for both lungs
Superior lobes at level T2-T4 Oblique fissures: follow curve of rib 6 (or, follow medial border of rotated scapula) Inferior lobe at level T5-T10
Describe the differences in thoracic drainage between the right and left sides of the body.
The 2nd-12th intercostal veins on the right side of the body drain into the azygos vein, which is found along the right side of the spinal column. The azygos vein then empties into the superior vena cava. The superior intercostal veins on the left side of the body drain into the Accessory Hemiazygos Vein, which crosses the spinal column inferiorly to join the azygos vein. The inferior intercostal veins on the left side of the body drain into the Hemiazygos Vein, which crosses the spinal column superiorly and drains into the azygos vein.
Describe the costodiaphragmatic recess. What is its function?
The costodiaphragmatic recess is a space between the costal pleura and the diaphragmatic pleura and is located inferiorly to the lungs. Its function is to allow room for the lungs to expand during deep inspiration. The costodiaphragmatic recess is much larger than the costomediastinal recess. It is important clinically because its large size and inferior placement make it a potential collection site for fluid.
Describe the costomediastinal recess. What is its function?
The costomediastinal recess is a space between the costal pleura and the mediastinal pleura and is located anteriorly to the lungs. Its function is to allow room for the lungs to expand during deep inspiration. The costomediastinal recess is larger on the left side, overlying the heart (upper arrow, in photo).
Describe the parietal pleura.
The parietal pleura is a serous membrane that attaches to the inner surface of the thoracic cavity. It is superficial to the visceral pleura.
Describe the visceral pleura.
The visceral pleura is a serous membrane that adheres to and covers the lung. It extends from the medial wall of the pleural cavity onto the surface of the lung. It is deep to the parietal pleura.
Describe the placement of the intercostal arteries in the intercostal space.
They are found at the superior margin of the intercostal space, protected by the intercostal groove of the superior rib. Intercostal arteries run between intercostal veins (superior) and intercostal nerves (inferior). They are bordered superficially by the inferior internal intercostal muscle and deeply by the innermost intercostal muscle.
Alveoli
Tiny sacs were oxygen and carbon dioxide exchange takes place; found ends of terminal bronchioles. (Each sac is an alveolus, not the whole cluster.)
Which two structures surround the pleural cavity?
Visceral Pleura Parietal Pleura
Right main bronchus features
Wider than left main bronchus More vertically oriented Inhaled objects commonly lodge: "path of least resistance" Divides into three secondary bronchi (one for each lobe of right lung)
