Respiratory System Anatomy

University of Babylon
College of Nursing Anesthesia Lec.2
Dr. Naji Yassesr Al-Mayyahi 4th Years _______________________________________________________________

I. Respiratory System Anatomy:

Respiratory System is vital to every human being. Without it, we would cease to live outside of the womb. Let us begin by taking a look at the structure of the respiratory system and how vital it is to life. During inhalation or exhalation air is pulled towards or away from the lungs, by several cavities, tubes, and openings.
The respiratory tract is the path of air from the nose to the lungs. It is divided into two sections: Upper Respiratory Tract and the Lower Respiratory Tract. Included in the upper respiratory tract are the Nostrils,Nasal Cavities, Pharynx, Epiglottis, and the Larynx. The lower respiratory tract consists of the Trachea, Bronchi, Bronchioles, and the Lungs



The lungs flank the heart and great vessels in the chest cavity.






Functions of Respiratory System:
1. BREATHING or ventilation
2. EXTERNAL RESPIRATION, which is the exchange of gases (oxygen and carbon dioxide) between inhaled air and the blood.

3. INTERNAL RESPIRATION, which is the exchange of gases between the blood and tissue fluids.
4. CELLULAR RESPIRATION
In addition to these main processes, the respiratory system serves for:•
• REGULATION OF BLOOD pH, which occurs in coordination with the kidneys, and as a
• DEFENSE AGAINST MICROBES
• Control of body temperature due to loss of evaporate during expiration
• Another function of the respiratory system is to sing and to speak. By exerting conscious control over our breathing and regulating flow of air across the vocal cords we are able to create and modify sounds.

Breathing and Lung Mechanics
Ventilation is the exchange of air between the external environment and the alveoli. Air moves by bulk flow from an area of high pressure to low pressure. All pressures in the respiratory system are relative to atmospheric pressure (760mmHg at sea level). Air will move in or out of the lungs depending on the pressure in the alveoli. The body changes the pressure in the alveoli by changing the volume of the lungs. As volume increases pressure decreases and as volume decreases pressure increases. There are two phases of ventilation; inspiration and expiration. During each phase the body changes the lung dimensions to produce a flow of air either in or out of the lungs. Normal adults have a breathing rate of 12-20 respirations per minute.
Although the respiratory system is primarily under involuntary control, and regulated by the medulla oblongata, we have some voluntary control over it also. This is due to the higher brain function of the cerebral cortex.

Control of respiration
central control[edit
Peripheral control[edit]
CO2 is converted to HCO3; most CO2 produced at the tissue cells is carried to lungs in the form of HCO3
• CO2 & H2O form carbonic acid (H2CO3)
• changes to H CO3 & H+ ions
• result is H+ ions are buffered by plasma proteins
Respiratory System:
Upper and Lower Respiratory Tracts
For the sake of convenience, we will divide the respiratory system in to the upper and lower respiratory tracts:
Upper Respiratory Tract]
The upper respiratory tract consists of the nose and the pharynx. Its primary function is to receive the air from the external environment and filter, warm, and humidify it before it reaches the delicate lungs where gas exchange will occur.
Air enters through the nostrils of the nose and is partially filtered by the nose hairs, then flows into the nasal cavity. The nasal cavity is lined with epithelial tissue, containing blood vessels, which help warm the air; and secrete mucous, which further filters the air. The endothelial lining of the nasal cavity also contains tiny hairlike projections, called cilia. The cilia serve to transport dust and other foreign particles, trapped in mucous, to the back of the nasal cavity and to the pharynx. There the mucus is either coughed out, or swallowed and digested by powerful stomach acids. After passing through the nasal cavity, the air flows down the pharynx to the larynx.
Lower Respiratory Tract
The lower respiratory tract starts with the larynx, and includes the trachea, the two bronchi that branch from the trachea, and the lungs themselves. This is where gas exchange actually takes place.
1. Larynx
The larynx (plural larynges), colloquially known as the voice box, is an organ in our neck involved in protection of the trachea and sound production. The larynx houses the vocal cords, and is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The larynx contains two important structures: the epiglottis and the vocal cords.
The epiglottis is a flap of cartilage located at the opening to the larynx. During swallowing, the larynx (at the epiglottis and at the glottis) closes to prevent swallowed material from entering the lungs; the larynx is also pulled upwards to assist this process. Stimulation of the larynx by ingested matter produces a strong cough reflex to protect the lungs. Note: choking occurs when the epiglottis fails to cover the trachea, and food becomes lodged in our windpipe.
The vocal cords consist of two folds of connective tissue that stretch and vibrate when air passes through them, causing vocalization. The length the vocal cords are stretched determines what pitch the sound will have. The strength of expiration from the lungs also contributes to the loudness of the sound. Our ability to have some voluntary control over the respiratory system enables us to sing and to speak. In order for the larynx to function and produce sound, we need air. That is why we can t talk when we re swallowing.
1. Trachea
2. Bronchi
3. Lungs

The Passage Way From the Trachea to the Bronchioles
There is a point at the inferior portion of the trachea where it branches into two directions that form the right and left primary bronchus. This point is called the Carina which is the keel-like cartilage plate at the division point. We are now at the Bronchial Tree. It is named so because it has a series of respiratory tubes that branch off into smaller and smaller tubes as they run throughout the lungs.
Right and Left Lungs

Diagram of the lungs
The Right Primary Bronchus is the first portion we come to, it then branches off into the Lobar (secondary) Bronchi,Segmental (tertiary) Bronchi, then to the Bronchioles which have little cartilage and are lined by simple cuboidal epithelium (See fig. 1). The bronchi are lined by pseudostratified columnar epithelium. Objects will likely lodge here at the junction of the Carina and the Right Primary Bronchus because of the vertical structure. Items have a tendency to fall in it, where as the Left Primary Bronchus has more of a curve to it which would make it hard to have things lodge there.
The Left Primary Bronchus has the same setup as the right with the lobar, segmental bronchi and the bronchioles.
The lungs are attached to the heart and trachea through structures that are called the roots of the lungs. The roots of the lungs are the bronchi, pulmonary vessels, bronchial vessels, lymphatic vessels, and nerves. These structures enter and leave at the hilus of the lung which is "the depression in the medial surface of a lung that forms the opening through which the bronchus, blood vessels, and nerves pass" (medlineplus.gov).
There are a number of terminal bronchioles connected to respiratory bronchioles which then advance into the alveolar ducts that then become alveolar sacs. Each bronchiole terminates in an elongated space enclosed by many air sacs calledalveoli which are surrounded by blood capillaries. Present there as well, are Alveolar Macrophages, they ingest any microbes that reach the alveoli. The Pulmonary Alveoli are microscopic, which means they can only be seen through a microscope, membranous air sacs within the lungs. They are units of respiration and the site of gas exchange between the respiratory and circulatory systems.





The Lungs:
The lungs are located in the chest on either side of the heart in the rib cage. They are conical in shape with a narrow rounded apex at the top and a broad base that rests on the diaphragm. The apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib. The lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm.The left lung shares space with the heart, with an impression in its medial surface called the cardiac impression.[2] The front and outer sides of the lung face the ribs, which make light indendations on their surfaces. The bottom of the lungs is smooth and rests on the diaphragm, matching its concavity. The medial surface of the lungs faces towards the centre of the chest, and lies against the heart, great vessels, and the carina where the two main bronchi branch off from the base of the trachea.
Both lungs have a central recession called the hilum at the root of the lung, where the blood vessels and airways pass into the lungs.There are also bronchopulmonary lymph nodes on the hilum.
The lungs are surrounded by the pulmonary pleurae. The pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs. Between the pleurae is a potential space called the pleural cavity containing pleural fluid. Each lung is divided into lobes by the invaginations of the pleura as fissures. The fissures are double folds of pleura that section the lungs and help in their expansion.
The lobes of the lungs are further divided into bronchopulmonary segments based on the locations of bronchioles. Segments for the left and right lung are shown in the table. The segmental anatomy is useful clinically for localising disease processes in the lungs.

Right lung:
The right lung has both more lobes and segments than the left. It is divided into three lobes, an upper, middle, and a lower, by two fissures, one oblique and one horizontal. The upper, horizontal fissure, separates the upper from the middle lobe. It begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced backward to the hilum.
The lower, oblique fissure, separates the lower from the middle and upper lobes, and is closely aligned with the oblique fissure in the left lung.
The mediastinal surface of the right lung is indented by a number of nearby structures. The heart sits in an impression called the cardiac impression. Above the hilum of the lung is an arched groove for the azygos vein, and above this is a wide groove for the superior vena cava and right innominate vein; behind this, and close to the top of the lung is a groove for the innominate artery. There is a groove for the esophagus behind the hilum and the pulmonary ligament, and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart.
Left lung:
The left lung is divided into two lobes, an upper and a lower, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum. The left lung, unlike the right, does not have middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the “lingula”. Its name means “little tongue”. The lingula on the left serves as an anatomic parallel to the right middle lobe, with both areas being predisposed to similar infections and anatomic complications.There are two bronchopulmonary segments of the lingula: superior and inferior.
The mediastinal surface of the left lung has a large cardiac impression where the heart sits. This is deeper and larger than that on the right lung, at which level the heart projects to the left.
On the same surface, immediately above the hilum, is a well-marked curved groove for the aortic arch, and a groove below it for the descending aorta. The left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung. A shallower groove in front of the artery and near the edge of the lung, lodges the left innominate vein. The esophagus may sit in a wider shallow impression at the base of the lung.


Lobes and bronchopulmonary segments
Right lung Left lung
Upper
• Apical
• Anterior
• Posterior
Middle
• Medial
• Lateral
Lower
• Superior
• Anterior
• Posterior
• Medial
• Lateral Upper
• Anterior
• Apicoposterior
Lower
• Superior
• Anterior
• Posterior
• Medial
• Lateral
Lingula
• Superior
• Inferior