ANA 202 Lungs and Lower Respiratory Tract Flashcards
What is pleura?
It is large, thin sheet/ sac that invest (wrap) the outside of the lungs and lines the inside of the chest
Types of pleura
Parietal pleura (lines the thoracic wall/chest, mediastinum, and diaphragm) and thicker than visceral pleura
*Viscera pleura (adheres to and covers the lung)
Describe the pleural cavity
In between these membranes is a potential space called the pleural cavity
•This pleural cavity is filled with serous fluid
•This fluid lubricates the pleural surfaces and allows the layers of pleura to slide smoothly over each other during respiration
●Note
The pleura cavity superiorly, extends above rib I into the root of the neck
What are the parts of the parietal pleura?
• Costal part
• mediastinal part
•Diaphragmatic part
•cervical pleura
Discuss the costal part of the parietal pleura
Costal part
●This is the part of the pleura that covers the internal part of the thoracic wall
●It is separated from the internal surface of the thoracic wall, intercostal muscles and membranes, and sides of thoracic vertebrae by the endothoracic fascia
Discuss the diaphragmatic part of the parietal pleura
Diaphragmatic part
●It is the part of the pleura covering the diaphragm
●This part of the pleural is connected with the diaphragm by the phrenicopleural fascia
●The phrenicopleural fascia is a thin elastic layer of endothoracic fascia
Discuss the mediastinal parts of the parietal pleura
Mediastinal part
●The part of the pleura covering the lateral aspect of the mediastinum
Discuss the cervical part of the parietal pleura
Cervical pleura
●It covers the apex of the lung (the part of the lung extending superiorly through the superior thoracic aperture into the root of the neck
●forms a cup-like dome called the pleural cupula over the apex of the lungs
●It is reinforced by a fibrous extension of the endothoracic fascia
●This fibrous extension is called the suprapleural membrane/Sibson fascia
● The suprapleural membrane attaches to the internal border of the 1st rib to the transverse process of C7
What is the relationship between the Visceral on the parietal pleura?
The visceral pleura is continuous with parietal pleura at the hilum of each lung where structures enter and leave the organ
What is a pleural recess?
Pleural recesses
•These are potential spaces within the thoracic cavity where the visceral and parietal pleura are relatively distant, particularly during expiration
What are the types of pleural recess?
•There are 2 types;
•Costodiaphragmatic recess
•Costomediastinal recess
Describe the Costodiaphragmatic recess
Costodiaphragmatic recess
•also called the phrenicocostal sinus
• a potential space at the posteriormost tips of the cavity
•located at the junction of the costal pleura and diaphragmatic pleura
• measures approximately 5 cm vertically
• extends from the 8-10th rib along the mid-axillary line
Function of the costodiaphragmatic recess
Function
•The lungs expand into this recess during forced inspiration, however the recess never fills completely
• During expiration, it contains no lung tissue, only pleural fluid
Clinical significance of the of the costodiaphragmatic recess
Clinical significance
1.Pleural effusions collect in the costodiaphragmatic recess when in standing position
●Note
● pleural effusions are excess fluid that accumulates between the two pleural layers
● Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during ventilation
II. A thoracocentesis (pleural tap/ removal of fluid or air )
Why is A thoracocentesis performed with the lungs are in full expiration?
is often performed here while a patient is in full expiration because of less risk of puncturing the lungs and thereby causing pneumothorax
Describe the costomediastinal recess & where is it most obvious
•is a potential space at the border of the mediastinal pleura and the costal pleura
• It helps the lungs to expand during deep inspiration, although its role isn’t as significant as the costodiaphragmatic recess, which has more volume
The costomediastinal recess is most obvious in the cardiac notch of the left lung
Describe the trachea
•The trachea is about 4.5In (11.5cm) in length and nearly 1 In (2.5cm) in diameter.
•It commences at the lower border of the cricoid cartilage (C6) and terminates by bifurcating at the level of the sternal angle of Louis (T4/5) to form the right and left main bronchi.
•(In the living subject, the level of bifurcation varies slightly with the phase of respiration; in deep inspiration is descends to T6 and in expiration it rises to T4.)
Discuss the cervical relations of the trachea
Cervical
•Anteriorly— the isthmus of thyroid gland, inferior thyroid veins, sternohyoid and sternothyroid muscles;
•Laterally—the lobes of thyroid gland and the common carotid artery;
•Posteriorly—the oesophagus with the recurrent laryngeal nerve lying in the groove between oesophagus and trachea.
Discuss the thoracic relations of the trachea
Thoracic
•In the superior mediastinum its relations are:
•Anteriorly—commencement of the brachiocephalic (innominate) artery and left carotid artery, both arising from the arch of the aorta, the left brachiocephalic (innominate) vein, and the thymus;
•Posteriorly—oesophagus and left recurrent laryngeal nerve;
•The left— arch of the aorta, left common carotid and left subclavian arteries, left recurrent laryngeal nerve and pleura;
•To the right—vagus, azygos vein and pleura.
Describe the structure of the trachea
The patency of the trachea is maintained by a series of 15–20 U-shaped cartilages.
•Posteriorly, where the cartilage is deficient, the trachea is flattened and its wall completed by fibrous tissue and a sheet of smooth muscle (the trachealis).
Epithelial lining of the trachea
Within, it is lined by a ciliated pseudostratified columnar epithelium with many goblet cells.
Describe the pathway of the main bronchi
The main bronchi (primary bronchi), one to each lung, pass inferolaterally from the bifurcation of the trachea at the level of the sternal angle to the hila (plural of hilum) of the lungs.
The main bronchi enter the hila of the lungs and branch in a constant fashion within the lungs to form the bronchial tree.
•Each main bronchus divides into lobar bronchi (secondary bronchi), two on the left and three on the right, each of which supplies a lobe of the lung.
•Each lobar bronchus divides into several segmental bronchi (tertiary bronchi) that supply the bronchopulmonary segments.
Describe the right main bronchus. What are its relations?
The right main bronchus is wider, shorter and more vertical than the left.
•It is about 1 in (2.5cm) long and passes directly to the root of the lung at T5.
•Before joining the lung it gives off its upper lobe branch, and then passes below the pulmonary artery to enter the hilum of the lung.
•It has two important relations: the azygos vein which arches over it from behind to reach the superior vena cava, and the pulmonary artery which lies first below and then anterior to it.
Describe the left main bronchus
The left main bronchus is nearly 2 in (5cm) long and passes downwards and outwards below the arch of the aorta, in front of the oesophagus and descending aorta.
•Unlike the right, it gives off no branches until it enters the hilum of the lung, which it reaches opposite T6.
•The pulmonary artery spirals over the bronchus, lying first anteriorly and then above it
What are the bronchopulmonary segments?
A bronchopulmonary segment is a portion of lung supplied by a specific segmental bronchus and its vessels.
Features of the bronchopulmonary segment
•Each segment are pyramidal in shape
•They are surrounded by connective tissue
•Separated from adjacent segments by connective tissue septa
•Each segment have their own artery
Discuss the clinical significance of the bronchopulmonary segment
each bronchopulmonary segment is a discrete anatomical and functional unit,
•this separation means that a bronchopulmonary segment can be surgically removed without affecting the function of the other segments
Vasculature of the bronchopulmonary segments
Each bronchopulmonary segment is supplied by;
•a segmental tertiary bronchus
• and 2 arteries
These 2 arteries are;
• a pulmonary artery
• bronchial artery
•Drained by tributaries of the pulmonary veins that lie in the connective tissue between adjacent bronchopulmonary segment
•Each segment has its own lymphatic vessels and autonomic nerve supply
Division of the bronchopulmonary segment
Division of segmental bronchi
•The segmental bronchi divide repeatedly to form terminal bronchioles
•Each terminal bronchiole gives rise to several generations of respiratory bronchioles
•Each respiratory bronchiole gives rise to 2-11 alveolar ducts, each of which gives rise to 5-6 alveolar sacs
•each alveolar sac contains a bunch of alveoli (the balls)
•The total no of alveoli has been estimated to be between 200 - 600 millions
Clinicals of the bronchopulmonary segment
- The greater width and more vertical course of the right bronchus accounts for the greater tendency for foreign bodies and aspirated material to pass into the right bronchus (and thence especially into the middle and lower lobes of the right lung) rather than into the left.
- The inner aspect of the whole of the trachea, the main and lobar bronchi and the commencement of the first segmental divisions can be seen at bronchoscopy.
- Widening and distortion of the angle between the bronchi (the carina) as seen at bronchoscopy is a serious prognostic sign, since it usually indicates carcinomatous involvement of the tracheobronchial lymph nodes around the bifurcation of the trachea.
Describe the lungs
The lungs are the vital organs of respiration.
•Their main function is to oxygenate the blood by bringing inspired air into close relation with the venous blood in the pulmonary capillaries.
•Although cadaveric lungs may be shrunken, hard to the touch, and discolored in appearance, healthy lungs in living people are normally light, soft, and spongy.
•They are also elastic and recoil to approximately one-third their size when the thoracic cavity is opened .
The lungs are separated from each other by the heart, viscera, and great vessels of the mediastinum.
•The lungs attach to the heart and trachea by structures that comprise the roots of the lungs- formed by structures entering and emerging from the lung at its hilum (hilus)–the bronchus and pulmonary vessels
What is the hilum of the lungs?
The hilum is where structures forming the root enter or exit the lungs e.g. like the area of earth where a plant’s roots enter the ground.
The structures forming the root of the lungs include
•pulmonary artery
•two pulmonary veins
•a main bronchus
•bronchial vessels
•nerves
•lymphatics
pulmonary ligament
A thin blade-like fold of pleura projects inferiorly from the root of the lung and extends from the hilum to the mediastinum
Why so the right lungs a little larger than the left?
The right lung is normally a little larger than the left lung because the middle mediastinum, containing the heart, bulges more to the left than to the right.
What divide the lungs into lobes?
horizontal and oblique fissures
The right lung has three lobes, the left lung has two
Functions of the lungs
Allows air to enters and leave via main bronchi, which are branches of the trachea
•Receives deoxygenated blood from the right ventricle via the pulmonary arteries
•Returns oxygenated blood to the left atrium via the pulmonary vein
Parts of the lungs
Each lungs has;
• An apex (projects above rib I and into the root of the neck)
•A base (which sits on the diaphragm)
•2 or 3 lobes, created by one or two fissures
•3 surfaces (costal, medial, and diaphragmatic)
•3 borders (anterior, inferior, and posterior)
Note: the medial surface is divided into
•vertebral part
• mediastinal part ( related to the mediastinal
Describe the apex of the lungs
The Apex of the Lung
•The rounded, tapered superior end or apex of the lung extends through the superior thoracic aperture into the root of the neck
•Here, it lies in close contact to the dome or the cupula of the pleura
•The apex of the lung is crossed by the subclavian artery, which produces a groove in the mediastinal surface
•The artery, however, is separated from the cupula by the suprapleural membrane
Describe The Base of the Lung
•This is the concave diaphragmatic surface of the lung, which is related to the dome of the diaphragm
•The base of the right lung is deeper because the right dome rises to a more superior level
•Its inferior border is thin and sharp where it enters the costodiaphragmatic recess
List The Main Differences Between the Right and Left Lungs
•The right lung has 3 lobes while the left has 2 lobes
•Right lungs has 2 fissure, left lungs has one
•The right lung is larger and heavier than the left lung
(right lung weighs about 700g, left lung weighs about 600g)
• it is shorter and wider because the right dome of the diaphragm is higher and the heart and pericardium bulge more to the left
•The anterior margin of the right lung is straight, whereas the margin of the left lung has a deep cardiac notch
•Right lung is shorter, wider and more in line with the trachea than the left principal bronchus. Inhaled particles pass more frequently to the right lung as a result of this compared to the left lung
The medial surface of the right lung lies adjacent to a number of important structures in the mediastinum and the root of the neck
These include;
•heart
•inferior vena cava
•superior vena cava
•azygos vein
•Esophagus
•Trachea
•Right vagus nerve
•Right phrenic nerve
•The right subclavian artery and vein arch over and are related to the superior lobe of the right lung as they pass over the dome of cervical pleura and into the axilla.
The medial surface of the left lung lies adjacent to a number of important structures in the mediastinum and root of the neck
These include
•heart,
• arch of aorta
•Descending thoracic aorta
Esophagus
•Thoracic duct
•Pulmonary trunk
•Left vagus nerve
•Left phrenic nerve
•The left subclavian artery and vein arch over and are related to the superior lobe of the left lung as they pass over the dome of cervical pleura and into the axilla
Arterial supply of the lungs
•right and left pulmonary arteries
•Bronchial arteries
Venous drainage of lungs
•Pulmonary veins
•Bronchial veins:
•Right bronchial veins drain into the azygos vein
•Left bronchial vein drains into the hemi azygos vein
Lymphatics of the lungs
lymphatics
•Superficial and deep plexus drain into the bronchopulmonary lymph nodes in the region of the lung hilum
•All the lymph from the lung leaves the hilum and drains into the tracheobronchial nodes and then into the bronchomediastinal lymph trunks
Innervation:
Innervation of the lungs
Innervation:
•Anterior and posterior pulmonary plexus
•Vagus nerve (parasymphathetic) constrict the bronchioles
•2nd -5th spinal segments (symphathetic) dilate the bronchioles
Clinical anatomy of the lungs
Pneumothorax
•Entry of air into the pleural cavity (pneumothorax), resulting from a penetrating wound of the parietal pleura from a bullet
•Fractured ribs may also tear the visceral pleura and lung, thus producing pneumothorax
Hydrothorax
•The accumulation of a significant amount of fluid in the pleural cavity (hydrothorax) may result from pleural effusion (escape of fluid into the pleural cavity)
Haemothorax
•With a chest wound, blood may also enter the pleural cavity (hemothorax)
• Hemothorax results more commonly from injury to a major intercostal or internal thoracic vessel than from laceration of a lung
