THE RESPIRATORY SYSTEM THE RESPIRATORY SYSTEM VISCERA OF THORACIC - - PowerPoint PPT Presentation

THE RESPIRATORY SYSTEM

VISCERA OF THORACIC CAVITY

THE RESPIRATORY SYSTEM

VISCERA OF THORACIC CAVITY The thoracic cavity is divided into three compartments:

• Right and le9 pulmonary caviBes, bilateral compartments

that contain the lungs and pleurae and occupy the majority of the thoracic cavity.

• A central mediasBnum, a compartment intervening between and

completely separaFng the two pulmonary caviFes, which contains essenFally all other thoracic structures: the heart, thoracic parts of the great vessels, thoracic part of the trachea, esophagus, thymus, and other structures (e.g., lymph nodes).

THE RESPIRATORY SYSTEM

PLEURAE Each lung is invested by and enclosed in a serous pleural sac that consists of two conBnuous membranes: the visceral pleura, which invests all surfaces of the lungs forming their shiny outer surface, and the parietal pleura, which lines the pulmonary caviFes

THE RESPIRATORY SYSTEM

The pleural cavity - the potenBal space between the layers

• f pleura - contains a capillary layer of serous pleural fluid, which

lubricates the pleural surfaces and allows the layers of pleura to slide smoothly over each other during respiraFon. The visceral pleura (pulmonary pleura) closely covers the lung and adheres to all its surfaces, including those within the horizontal and

• blique fissures.

The visceral pleura is conFnuous with the parietal pleura at the hilum

• f the lung, where structures making up the root of the lung (e.g.,

bronchus and pulmonary vessels) enter and leave the lung.

PLEURAE The parietal pleura lines the pulmonary caviFes, thereby adhering to the thoracic wall, mediasFnum, and diaphragm.

THE RESPIRATORY SYSTEM

The parietal pleura consists of three parts:

• costal,
• mediasFnal,
• diaphragmaFc
• and the cervical pleura.

The costal part of the parietal pleura (costovertebral or costal pleura) covers the internal surfaces of the thoracic wall. It is separated from the internal surface of the thoracic wall (sternum, ribs and costal carFlages, intercostal muscles and membranes, and sides of thoracic vertebrae) by endothoracic fascia.

PLEURAE The mediasBnal part of the parietal pleura (mediasFnal pleura) covers the lateral aspects of the mediasFnum

THE RESPIRATORY SYSTEM

The diaphragmaBc part of the parietal pleura (diaphragmaFc pleura) covers the superior (thoracic) surface of the diaphragm on each side of the mediasFnum, except along its costal a.achments (origins)

and where the diaphragm is fused to the pericardium

The cervical pleura covers the apex of the lung - the part of the lung extending superiorly through the superior thoracic aperture into the root of the neck. A thin, more elasFc layer of endothoracic fascia, the phrenicopleural fascia, connects the diaphragmaFc pleura with the muscular fibers of the diaphragm

LUNGS The lungs are the vital organs of respiraFon. Their main funcFon is to

• xygenate the blood by bringing inspired air into close relaFon with

the venous blood in the pulmonary capillaries.

THE RESPIRATORY SYSTEM

The lungs are separated from each other by the mediasBnum. Each lung has:

• apex
• base
• two or three lobes
• three surfaces
• three borders

LUNGS Each lung has: an APEX, the blunt superior end of the lung ascending above the level

• f the 1st rib into the root of the neck; the apex is covered by cervical

pleura. A BASE, the concave inferior surface of the lung, opposite the apex, resFng on and accommodaFng the ipsilateral dome of the diaphragm TWO OR THREE LOBES, created by one or two fissures. THREE SURFACES (costal, mediasFnal, and diaphragmaFc). THREE BORDERS (anterior, inferior, and posterior).

THE RESPIRATORY SYSTEM

LUNGS The right lung is larger and heavier than the leQ

THE RESPIRATORY SYSTEM

The right lung features right oblique and horizontal fissures that divide it into three right lobes:

• superior
• middle
• inferior.

The le9 lung has a single leQ oblique fissure dividing it into two leQ lobes:

• superior
• inferior.

LUNGS The anterior border of the leQ lung has a deep cardiac notch

THE RESPIRATORY SYSTEM

The most inferior and anterior part of the superior lobe into a thin, tongue-like process, the lingula which extends below the cardiac notch The mediasBnal surface of the lung is concave because it is related to the middle mediasFnum The mediasBnal surface includes the hilum, which receives the root

• f the lung.

LUNGS The mediasBnum of the right lung:

• groove for the esophagus
• cardiac impression for the heart
• groove for inferior and superior vena cava
• groove for azygos vein

THE RESPIRATORY SYSTEM

The mediasBnum of the le9 lung:

• cardiac impression for the heart
• groove for the arch of the aorta and the descending aorta
• smaller area for the esophagus

LUNGS The diaphragmaBc surface of the lung, which is also concave, forms the base of the lung, which rests on the dome of the diaphragm.

THE RESPIRATORY SYSTEM

The borders of the lung:

• anterior
• inferior
• posterior

The anterior border of the lung is where the costal and mediasFnal surfaces meet anteriorly and overlap the heart. The inferior border of the lung circumscribes the diaphragmaFc surface of the lung and separates this surface from the costal and mediasFnal surfaces. The posterior border of the lung is where the costal and mediasFnal surfaces meet posteriorly

LUNGS The roots of the lungs – where the lungs are aSached to the

• mediasFnum. A short tubular collecFon of structures that together

aSach the lung to structures in the mediasFnum.

THE RESPIRATORY SYSTEM

The roots of the lungs contains:

• bronchi and associated bronchial vessels,
• pulmonary arteries,
• superior and inferior pulmonary veins,
• pulmonary plexuses of nerves (sympatheFc, parasympatheFc),
• lymphaFc vessels

Generally, the pulmonary artery is superior at the hilum, the pulmonary veins are inferior, and the bronchi are somewhat posterior in posiFon.

THE RIGHT LUNGS The right lung has three lobes and two fissures.

THE RESPIRATORY SYSTEM

The oblique fissure separates the inferior lobe (lower lobe) from the superior lobe and the middle lobe of the right lung. The horizontal fissure separates the superior lobe (upper lobe) from the middle lobe.

THE LEFT LUNGS The le9 lung is smaller than the right lung and has two lobes separated by an oblique fissure.

THE RESPIRATORY SYSTEM

The oblique fissure of the leQ lung is slightly more oblique than the corresponding fissure of the right lung. Inferior to the root of the lung, this conFnuity between parietal and visceral pleura forms the pulmonary ligament, extending between the lung and the mediasFnum, immediately anterior to the esophagus.

LUNGS In the mediasFnum, the vagus nerves pass immediately posterior to the roots of the lungs, while the phrenic nerves pass immediately anterior to them.

THE RESPIRATORY SYSTEM

TRACHEOBRONCHIAL TREE TRACHEA Is approximately 12 cm in length and has 16 to 20 incomplete hyaline carBlaginous rings that open posteriorly toward the esophagus and prevent the trachea from collapsing.

THE RESPIRATORY SYSTEM

Begins at the inferior border of the cricoid carBlage (C6) as a conFnuaFon of the larynx. Ends by bifurcaBng into the right and leQ main stem bronchi at the level of the sternal angle (disc between T4 and T5).

TRACHEOBRONCHIAL TREE TRACHEA Has the carina, a downward and backward projecFon of the last tracheal carFlage, which lies at the level of the sternal angle and forms a keel-like ridge separaFng the openings of the right and leQ main bronchi. Carina may be distorted, widened posteriorly, and immobile in the presence of a bronchogenic carcinoma. May be compressed by an aorFc arch aneurysm, a goiter, or thyroid tumors, causing dyspnea.

THE RESPIRATORY SYSTEM

TRACHEOBRONCHIAL TREE RIGHT BRONCHUS The right main bronchus is wider, shorter, and runs more verBcally than the leQ main bronchus as it passes directly to the hilum of the lung.

THE RESPIRATORY SYSTEM

LEFT BRONCHUS The leQ main bronchus passes inferolaterally, inferior to the arch of the aorta and anterior to the esophagus and thoracic aorta, to reach the hilum of the lung.

TRACHEOBRONCHIAL TREE BRONCHI Each main bronchus divides into secondary lobar bronchi:

• two on the leQ
• three on the right

Each lobar bronchus divides into several terFary segmental bronchi that supply the bronchopulmonary segments

THE RESPIRATORY SYSTEM

TRACHEOBRONCHIAL TREE The bronchopulmonary segments are:

• The largest subdivisions of a lobe
• Pyramidal-shaped segments of the lung, with their apices facing the

lung root and their bases at the pleural surface.

• Separated from adjacent segments by connecFve Fssue septa.
• Supplied independently by a segmental bronchus and terFary

branch of the pulmonary artery.

• Named according to the segmental bronchi supplying them
• Drained by intersegmental parts of the pulmonary veins
• Usually 18–20 in number (10 in the right lung; 8–10 in the leQ lung,

depending on the combining of segments).

• Surgically resectable

THE RESPIRATORY SYSTEM

TRACHEOBRONCHIAL TREE

• segmental bronchi

ê

• terminal bronchioles
• conducFng bronchioles
• respiratory bronchioles

ê

• pulmonary alveolus
• alveolar ducts
• alveolar sacs

THE RESPIRATORY SYSTEM

Bronchioles lack carFlage in their walls ConducFng bronchioles transport air but lack glands or alveoli. The pulmonary alveolus is the basic structural unit of gas exchange in the lung. LOBAR BRONCHI ê

VASCULATURE OF LUNGS AND PLEURAE Each lung has a pulmonary artery supplying blood to it and two pulmonary veins draining blood from it.

THE RESPIRATORY SYSTEM

The right and le9 pulmonary arteries arise from the pulmonary trunk at the level of the sternal angle; they carry low-oxygen (“venous”) blood to the lungs for oxygenaFon. Each pulmonary artery becomes part of the root of the corresponding lung and divides secondary lobar arteries and segmental arteries. Two pulmonary veins, a superior and an inferior pulmonary vein on each side, carry oxygen-rich (“arterial”) blood from corresponding lobes of each lung to the leQ atrium of the heart.

VASCULATURE OF LUNGS AND PLEURAE Bronchial arteries supply blood for nutriFon of the structures making up the root of the lungs, the supporFng Fssues of the lungs, and the visceral pleura.

THE RESPIRATORY SYSTEM

The two le9 bronchial arteries usually arise directly from the thoracic aorta. The single right bronchial artery may also arise directly from the aorta. The pulmonary lymphaBc plexuses communicate freely. The superficial subpleural lymphaBc plexus lies deep to the visceral pleura and drains the lung parenchyma (Fssue) and visceral pleura.

VASCULATURE OF LUNGS AND PLEURAE LymphaFc vessels from this superficial plexus drain into the bronchopulmonary lymph nodes.

THE RESPIRATORY SYSTEM

The deep bronchopulmonary lymphaBc plexus is located in the submucosa of the bronchi and in the peribronchial connecFve Fssue. LymphaFc vessels from this deep plexus drain iniFally into the intrinsic pulmonary lymph nodes, located along the lobar bronchi. Lymph from the tracheobronchial lymph nodes passes to the right and leQ bronchomediasFnal lymph trunks, the major lymph conduits draining the thoracic viscera These trunks usually terminate on each side at the venous angles (juncFons of the subclavian and internal jugular veins).

NERVES OF LUNGS AND PLEURAE The nerves of the lungs and visceral pleura are derived from the pulmonary plexuses anterior and (mainly) posterior to the roots

• f the lungs

THE RESPIRATORY SYSTEM

These nerve networks contain:

• parasympatheFc
• sympatheFc
• visceral afferent fibers

The parasympatheBc fibers conveyed to the pulmonary plexus are presynapFc fibers from the vagus nerve (CN X). The sympatheBc fibers of the pulmonary plexuses are postsynapFc fibers. Their cell bodies are in the paravertebral sympatheBc ganglia of the sympatheBc trunks

NERVES OF LUNGS AND PLEURAE The sympatheBc nerve fibers dilate the lumina of the bronchi and constrict the pulmonary vessels.

THE RESPIRATORY SYSTEM

The parasympatheBc fibers constrict the lumina, dilate the pulmonary vessels, and increase glandular secreFon.

RESPIRATION

THE RESPIRATORY SYSTEM

Is the vital exchange of oxygen and carbon dioxide that occurs in the lungs. The air–blood barrier consists of alveolar type I cells, basal lamina, and capillary endothelial cells. The alveolar type II cells secrete surfactant.

INSPIRATION Occurs when the ribs and sternum (or thoracic cage) are elevated by the following muscles:

• the diaphragm
• external, internal (interchondral part), and innermost intercostal
• sternocleidomastoid
• levator costarum
• serratus anterior
• scalenus
• pectoralis major and minor
• serratus posterior superior muscles.

THE RESPIRATORY SYSTEM

INSPIRATION Involves the following processes:

• 1. ContracFon of the Diaphragm
• 2. Enlargement of the Pleural CaviFes and Lungs
• 3. Forced InspiraBon

Involves contracFon of the intercostal muscles and elevaFon of the ribs (superolateral movement), with the sternum moving anteriorly like a bucket handle. (When the handle is raised, the convexity moves laterally.) Results in increased transverse and anteroposterior diameters of the thoracic cavity. The abdominal volume is decreased with an increased abdominal pressure.

THE RESPIRATORY SYSTEM

EXPIRATION Involves the following muscles: the muscles of the anterior abdominal wall, internal intercostal (costal part) muscles, and serratus posterior inferior muscles.

THE RESPIRATORY SYSTEM

Involves the following processes:

• 1. Overall Process
• 2. ElasFc Recoil of the Lungs
• 3. Forced ExpiraFon

EXPIRATION Involves the following processes:

• 1. Overall Process

Involves relaxaFon of the diaphragm, the internal intercostal muscles (costal part), and other muscles; decrease in thoracic volume; and increase in the intrathoracic pressure. The abdominal pressure is decreased, and the ribs are depressed.

THE RESPIRATORY SYSTEM

EXPIRATION Involves the following processes:

• 1. Overall Process
• 2. ElasBc Recoil of the Lungs

Produces a subatmospheric pressure in the pleural caviFes. Thus, much of the air is expelled. (Quiet expiraFon is a passive process caused by the elasFc recoil of the lungs, whereas quiet inspiraFon results from contracFon of the diaphragm.)

THE RESPIRATORY SYSTEM

EXPIRATION Involves the following processes:

• 1. Overall Process
• 2. ElasFc Recoil of the Lungs
• 3. Forced ExpiraBon

Requires contracFon of the anterior abdominal muscles and the internal intercostals (costal part).

THE RESPIRATORY SYSTEM