Radiographic Anatomy of the Chest PDF

CHAPTER 2: CHEST BY: JACQUILINE M. GEALON, RRT  RADIOGRAPHIC ANATOMY Chest Chest radiographic examinations are the most common of all radiographic procedures The chest, or thorax, is the upper portion of the trunk between the neck and the abdomen. Radiographic...

CHAPTER 2: CHEST BY: JACQUILINE M. GEALON, RRT  RADIOGRAPHIC ANATOMY Chest Chest radiographic examinations are the most common of all radiographic procedures The chest, or thorax, is the upper portion of the trunk between the neck and the abdomen. Radiographic anatomy of the chest is divided into three sections: bony thorax, respiratory system proper, and mediastinum.  RADIOGRAPHIC ANATOMY BONY ThORAX The bony thorax is the part of the skeletal system that provides a protective framework for the parts of the chest involved with breathing and blood circulation. Thoracic viscera is the term used to describe these parts of the chest consisting of the lungs and the remaining thoracic organs contained in the mediastinum. Anteriorly, the bony thorax consists of the sternum (breast- bone), which has three divisions. ⚬ The superior portion is the manubrium ⚬ the large center portion is the body ⚬ the smaller inferior portion is the xiphoid process.  RADIOGRAPHIC ANATOMY BONY ThORAX Superiorly, the bony thorax consists of the 2 clavicles (collar-bones) that connect the sternum to the 2 scapulae (shoulder blades) the 12 pairs of ribs that circle the thorax, and the 12 thoracic vertebrae posteriorly.  Topographic Positioning Landmarks Accurate and consistent radiographic positioning requires certain landmarks, or reference points, that can be used to center the image receptor (IR) correctly to ensure that all essential anatomy is included on that specific projection. For chest positioning, two of these landmarks are the vertebra prominens and the jugular notch.  Topographic Positioning Landmarks Vertebra prominens (seventh cervical vertebra) It can be palpated readily on most patients by applying light pressure with the fingertips at the base of the neck. The vertebra prominens is the first prominent process felt as you gently but firmly palpate down the back of the neck with the head dropped forward.  Topographic Positioning Landmarks Jugular notch (manubrial or suprasternal notch) This is palpated easily as a deep notch or depression on the superior portion of the sternum below the thyroid cartilage.  Topographic Positioning Landmarks Xiphoid process (tip) The inferior tip of the sternum, the xiphoid process, which corresponds to the level of T9 or T10, can also be palpated The xiphoid process corresponds to the approximate level of the anterior portion of the diaphragm, which separates the chest cavity from the abdominal cavity.  Respiratory System Respiration is the exchange of gaseous substances between the air we breathe and the bloodstream. The respiratory system consists of the parts of the body through which air passes as it travels from the nose and mouth into the lungs. Four general divisions of the respiratory system, are the pharynx, trachea, bronchi, and lungs.  Respiratory System An important structure of the respiratory system is the dome- shaped diaphragm, which is the primary muscle of inspiration. Each half of the diaphragm is called a hemidiaphragm As the dome of the diaphragm moves downward, it increases the volume of the thoracic cavity. This increase in volume, along with certain other dimensional movements of the thorax decreases the intra-thoracic pressure, creating a “sucking” action or negative pressure effect, resulting in air being drawn into the lungs through the nose and mouth, pharynx, larynx, trachea, and bronchi. This causes the lungs to fill with air, which is known as inspiration.  Respiratory System Pharynx The pharynx (upper airway) is a structure or passageway that is important to the respiratory system because air must pass through it before entering the respiratory system, which begins with the larynx, or voice box. The pharynx, also referred to as the upper airway or the upper respiratory tract, is the posterior area between the nose and mouth above and the larynx and esophagus below. This area serves as a passageway for food and fluids as well as air, making it common to the digestive and respiratory systems.  Respiratory System Pharynx The pharynx has three divisions, nasopharynx , oropharynx, and laryngopharynx. The interior of the pharynx communicates posteriorly with certain cavities—the nose above (nasopharynx), the mouth (oropharynx), and the larynx below (laryngopharynx)—as well as the esophagus. The hard palate and the soft palate make up the roof of the oral cavity. The lower posterior aspect of the soft palate is called the uvula The laryngopharynx lies above and posterior to the larynx and extends from the upper border of the epiglottis  Respiratory System Pharynx The upper portion of the epiglottis projects upward behind the tongue and acts as a lid for the slanted opening of the larynx. During the act of swallowing, the epiglottis flips down and covers the laryngeal opening, Additional structures shown on this sectional lateral drawing are the hyoid bone, thyroid cartilage of the larynx (Adam’s apple), thyroid gland, and trachea  Respiratory System Esophagus The esophagus is the part of the digestive system that connects the pharynx with the stomach. It begins at the distal end of the laryngopharynx and continues downward to the stomach, posterior to the larynx and trachea.  Respiratory System Four Parts of the Respiratory System The four parts of the respiratory system proper that are important in chest radiography are as follows: 1.Larynx (voice box) 2.Trachea 3.Right and left bronchi 4.Lungs The larynx, trachea, and bronchi form a continuous, tubular structure through which air can pass from the nose and mouth into the lungs,  Respiratory System Larynx (voice box) The larynx, or voice box, is a cagelike, cartilaginous structure that is approximately 1 1/2 to 2 inches (4 to 5 cm) in length in an adult. The larynx is located in the anterior portion of the neck, suspended from a small bone called the hyoid The hyoid bone is found in the upper neck just below the tongue or floor of the mouth  Respiratory System Larynx (voice box) The larynx serves as the organ of voice. Sounds are made as air passes between the vocal cords located within the larynx The upper margin of the larynx is at the approximate level of C3. Its lower margin, where the larynx joins with the trachea, is at the level of C6. The framework of the larynx consists of cartilages that are connected by ligaments and moved by numerous muscles that assist in the complex sound-making or voice process. The largest and least mobile of these cartilages is the thyroid cartilage, which consists of two fused platelike structures that form the anterior wall of the larynx. The prominent anterior projection of the thyroid cartilage is palpated easily and is known as the laryngeal prominence, or Adam’s apple.  Respiratory System Larynx (voice box) This prominent structure is an important positioning landmark because it is easy to locate. The laryngeal prominence of the thyroid cartilage located at approximately the level of C5 is an excellent topographic reference The cricoid cartilage is a ring of cartilage that forms the inferior and posterior wall of the larynx. It is attached to the first ring of cartilage of the trachea. One of the cartilages that make up the larynx is the uniquely shaped epiglottis, which resembles a leaf with the narrow distal stem portion attached to a part of the thyroid cartilage. As is described on the preceding page, the epiglottis flips down and covers the trachea during the act of swallowing  Respiratory System Trachea Continuing from the larynx downward, the second division of the respiratory system proper is the trachea, or windpipe. It is a fibrous muscular tube about 34 inch (2 cm) in diameter and 412 inches (11 cm) long. Approximately 20 C-shaped rings of cartilage are embedded in its walls. The trachea, located just anterior to the esophagus, extends from its junction with the larynx at the level of C6 (sixth cervical vertebra) downward to the level of T4 or T5 (fourth or fifth thoracic vertebra), where it divides into right and left primary bronchi. Glands located near the respiratory system include the thyroid, parathyroid, and thymus glands.  Respiratory System Thyroid gland The thyroid gland is a vascular organ that is located anteriorly in the neck region just below the larynx, with its right and left lateral lobes lying on each side and distal to the proximal trachea In an adult, it weighs 25 to 30 g (≈1 oz) and has a rich blood supply. As with other such glandular organs, the thyroid gland is more radiosensitive than many other body structures or organs. One unique feature of the thyroid gland is its ability to store certain hormones and release them slowly to aid in the regulation of body metabolism. These hormones also help to regulate body growth and development and activity of the nervous system, especially in children.  Respiratory System Parathyroid glands Parathyroid glands are small, round glands that are embedded in the posterior surface of the lateral lobes of the thyroid gland. Usually, two parathyroids are attached to each lateral thyroid lobe They store and secrete certain hormones that aid in specific blood functions, including maintenance of blood calcium levels.  Respiratory System Thymus gland The thymus gland is located just inferior to the thyroid gland  Respiratory System Radiographs AP and lateral radiographs of the upper airway allow visualization of the air-filled trachea and larynx.  Respiratory System Axial Sectional Image of the Trachea CT image through the upper chest at the approximate level of T3.  Respiratory System Right and Left Bronchi The third part of the respiratory system consists of the right and left primary bronchi, also known as the right and left main stem bronchi. The right primary bronchus is wider and shorter than the left bronchus. The right primary bronchus is also more vertical; therefore, the angle of divergence from the distal trachea is less abrupt for the right bronchus than for the left. The right bronchus is about 2.5 cm long and 1.3 cm in diameter. The angle of divergence of the right bronchus is only about 25°. The left bronchus is smaller in diameter (1.1 cm) than the right bronchus but about twice as long (5 cm). The divergent angle of the left primary bronchus is approximately 37°, which is more horizontal than the right bronchus.  Respiratory System Right and Left Bronchi The carina is a specific prominence, or ridge, of the lowest tracheal cartilage, which is seen at the bottom and inside portion of the trachea, where it divides into right and left bronchi. The position of the carina, is at the lower level of the division into the right and left primary bronchi. This is at the approximate level of T5 and is used as a specific reference point or level for CT of the thorax  Respiratory System Secondary Bronchi, Lobes, and Alveoli In addition to differences in size and shape between the right and left bronchi, another important difference is that the right bronchus divides into three secondary bronchi, but the left divides into only two, with each entering individual lobes of the lungs. The right lung contains three lobes, and the left lung contains two lobes These secondary bronchi continue to subdivide into smaller branches, called bronchioles, that spread to all parts of each lobe. Each of these small terminal bronchioles terminates in very small air sacs called alveoli. The two lungs contain 500 million to 700 million alveoli.  Respiratory System Axial Sectional Image of Bronchi and Lungs  Respiratory System Lungs The fourth and last division of the respiratory system comprises the two large, spongy lungs, which are located on each side of the thoracic cavity. The lungs fill all of the space not occupied by other structures. The right lung is made up of three lobes—the superior (upper), middle, and inferior (lower) lobes—divided by two deep fissures. The inferior fissure, which separates the inferior and middle lobes, is called the oblique fissure. The horizontal fissure separates the superior and middle lobes. The left lung has only two lobes—the superior (upper) and inferior (lower)—separated by a single deep oblique fissure.  Respiratory System Lungs The lungs are composed of a light, spongy, highly elastic substance called parenchyma This substance allows for the breathing mechanism responsible for expansion and contraction of the lungs, which brings oxygen into and removes carbon dioxide from the blood through the thin walls of the alveoli. Each lung is contained in a delicate double-walled sac, or membrane, called the pleura ⚬ The outer layer of this pleural sac lines the inner surface of the chest wall and diaphragm and is called the parietal pleura. ⚬ The inner layer that covers the surface of the lungs, also dipping into the fissures between the lobes, is called the pulmonary or visceral pleura  Respiratory System Lungs The potential space between the double-walled pleura, called the pleural cavity, contains a lubricating fluid that allows movement of one or the other during breathing. When a lung collapses, or when air or fluid collects between these two layers, this space may be visualized radiographically.  Respiratory System Axial Sectional Image of Lungs and Heart The double-walled membrane, the pleura, which completely encloses the lungs, including around the heart, is clearly shown. The outer membrane, the parietal pleura, and the inner membrane, the pulmonary (or visceral) pleura, are clearly visible, as is the potential space between them, the pleural cavity. The double-walled pericardial sac, which surrounds the heart, is also identified.  Respiratory System CT Axial Sectional Image  Respiratory System PA Chest Radiograph An enormous amount of medical information can be obtained from a properly exposed and carefully positioned PA chest radiograph. The clavicles, scapulae, and ribs can be identified through careful study of the chest radiograph The sternum and thoracic vertebrae are superimposed along with mediastinal structures, such as the heart and great vessels; therefore, the sternum and vertebrae are not well visualized on a PA chest radiograph. The lungs and the trachea of the respiratory system are well shown, although usually the bronchi are not seen easily. The first portion of the respiratory system, the larynx, is usually located above the top border of the radiograph and cannot be seen. The heart, large blood vessels, and diaphragm also are well visualized.  Respiratory System Parts of Lungs The apex (B) of each lung is the rounded upper area above the level of the clavicles. The apices of the lungs extend up into the lower neck area to the level of T1 (first thoracic vertebra). This important part of the lungs must be included on chest radiographs. The carina (C) is shown as the point of bifurcation, the lowest margin of the separation of the trachea into the right and left bronchi. The base (D) of each lung is the lower concave area of each lung that rests on the diaphragm (E). The diaphragm is a muscular partition that separates the thoracic and abdominal cavities. The costophrenic angle (F) refers to the extreme outermost lower corner of each lung, where the diaphragm meets the ribs.  Respiratory System Parts of Lungs The hilum (hilus) (G), also known as the root region, is the central area of each lung, where the bronchi, blood vessels, lymph vessels, and nerves enter and leave the lungs.  Respiratory System Lateral Chest View This drawing depicts the left lung as seen from the medial aspect. Because this is the left lung, only two lobes are seen. Some of the lower lobe (D) extends above the level of the hilum (C) posteriorly, whereas some of the upper lobe (B) extends below the hilum anteriorly. The posterior portion of the diaphragm is the most inferior part of the diaphragm. The single deep oblique fissure that divides the two lobes of the left lung is shown again, as is the end-on view of a bronchus in the hilar region. The right lung is usually about 1 inch shorter than the left lung. The reason for this difference is the large space-occupying liver that is located in the right upper abdomen, which pushes up on the right hemidiaphragm.  Mediastinum The medial portion of the thoracic cavity between the lungs is called the mediastinum. The thymus gland is located within the mediastinum, inferior to the thyroid gland and anterior to the trachea and esophagus Four radiographically important structures located in the mediastinum are the (1) thymus gland, (2) heart and great vessels, (3) trachea, and (4) esophagus.  Mediastinum Thymus Gland The thymus gland, located behind the upper sternum, is said to be a temporary organ because it is very prominent in infancy and reaches its maximum size of about 40 g at puberty, then gradually decreases in size until it almost disappears in adulthood. At its maximum development, the thymus gland lies above and anterior to the heart and pericardium. The thymus gland functions primarily during childhood and puberty to aid with the functioning of certain body immune systems that help the body resist disease.  Mediastinum Heart and Great Vessels The heart and the roots of the great vessels are enclosed in a double-walled sac called the pericardial sac The heart is located posterior to the body of the sternum and anterior to T5 to T8. It lies obliquely in the mediastinal space, and approximately two-thirds of the heart lies to the left of the median plane. The great vessels in the mediastinum are the inferior vena cava and superior vena cava, aorta, and large pulmonary arteries and veins. The superior vena cava is a large vein that returns blood to the heart from the upper half of the body The inferior vena cava is a large vein that returns blood from the lower half of the body.  Mediastinum Heart and Great Vessels The aorta is the largest artery in the body (1 to 2 inches [2.5 to 5 cm] in diameter in an average adult). It carries blood to all parts of the body through its various branches. The aorta is divided into three parts: ascending aorta (coming up out of the heart); arch of the aorta; and descending aorta, which passes through the diaphragm into the abdomen, where it becomes the abdominal aorta. Various pulmonary arteries and veins present in the mediastinum. ⚬ These supply blood and return blood to and from all segments of the lungs. The capillary network surrounds the small air sacs, or alveoli, where oxygen and carbon dioxide are exchanged with the blood through the thin- walled air sacs.  Mediastinum Trachea and Esophagus The trachea, within the mediastinum, separates into the right and left primary and secondary bronchi The proximal esophagus is located posterior to the trachea and continues down through the mediastinum anterior to the descending aorta until it passes through the diaphragm into the stomach. The heart is located in the anterior aspect of the thoracic cavity, directly behind the sternum. Questions? Thank You