Anatomy Of The Thorax And Abdomen Wsu

[Curtis Cassel]

Thethorax has two major openings: the superior thoracic aperture found superiorly and the inferior thoracic aperture located inferiorly. The superior thoracic aperture opens towards the neck. It is bounded by the bones of the upper thorax; manubrium of sternum, the first pair of ribs, and the body of the vertebra T1. The inferior thoracic aperture is almost completely covered by the diaphragm, separating it from the abdominal cavity.

Moving forward with the skeletal scaffold of the thorax, we have the thoracic skeleton. It is made up of the sternum, twelve pairs of ribs, twelve thoracic vertebrae, and interconnecting joints. The main thoracic joints include the intervertebral discs, costovertebral, sternocostal, sternoclavicular, costochondral, and interchondral joints.

Running between every two adjacent ribs are anatomical spaces called intercostal spaces. There are eleven in total, each one containing the intercostal muscles (external, internal, and innermost) together with the intercostal neurovascular bundle. This consists of the intercostal vein, artery, and nerve.

If you take a close look at the previous table and diagram, you will see that several major arteries and veins travel through the thorax. All the thoracic arteries originate from the aorta and the three largest ones are the brachiocephalic trunk, left common carotid artery, and left subclavian artery. Several visceral arteries also supply various thoracic organs including: bronchial, esophageal, pericardial, and several small mediastinal arteries. The thoracic aorta also gives off parietal branches for the thoracic muscles. These include the posterior intercostal, superior phrenic, and paired subcostal arteries.

In terms of venous drainage, the major veins of the thorax are the: superior vena cava, azygos venous system, accessory hemiazygos vein, pulmonary veins, esophageal veins, internal thoracic veins, cardiac veins, and superior intercostal veins. These vessels collect all the deoxygenated blood from the muscles and organs of the thorax, ultimately bringing them into the superior vena cava.

Since the thorax houses several organs, the main innervation is autonomic and appears in the form of visceral plexuses located close to each respective organ. These include the esophageal, cardiac, and thoracic aortic plexuses. These are formed by contributions from the sympathetic trunk, thoracic splanchnic nerves, recurrent laryngeal nerve, and the vagus nerve.

One of the most important organs situated in the thorax is the heart. It is the size of a clenched fist located in the middle mediastinum within the pericardial sac. This muscular pump receives direct blood via the coronary circulation and consists of four chambers: two atria and two ventricles. The right side of the heart handles deoxygenated blood while the left hand side deals with oxygenated blood. Several major blood vessels enter and leave the heart carrying blood to and from pulmonary and systemic circulations. They are the: superior and inferior vena cavae, pulmonary arteries, aorta, and pulmonary veins. Blood flow between the atria and ventricles is regulated by the heart valves (left atrioventricular (mitral), right atrioventricular (tricuspid), aortic, and pulmonary). In order for the heart to beat and complete its functions, it has an autonomic nervous control facilitated by the sinuatrial node, atrioventricular node, bundle of His, and Purkinje fibers.

The lungs are part of the respiratory system and they are the site of gas exchange and respiration. These bilateral structures occupy the pleural cavities and consist of lobes and bronchopulmonary segments separated by fissures. Air enters and leaves the lungs via a network of passageways consisting of the trachea, bronchi, bronchioles, and alveoli. Several structures enter each lung via a hilum: principal bronchus, pulmonary artery, two pulmonary veins, bronchial vessels, pulmonary autonomic plexus, lymph nodes and vessels, and connective tissue. Each lung is surrounded by two layers of pleura (parietal and visceral). The lung parenchyma is supplied by the bronchial arteries and veins, as well as the pulmonary nervous plexus.

The anatomical structure of the lung and air passageways can be quite complex, so we have provided you with additional resources below to help clear up any confusion. In addition, we have prepared a special custom quiz for you about the thorax anatomy, which will help you learn more about all the structures related to thorax!

In addition to the trachea, we have another tubular organ. The esophagus is a fibromuscular tube extending from the pharynx to the stomach. It is divided into three parts: cervical, thoracic, and abdominal. The esophagus is part of the digestive system and its role is to transport saliva, liquids, and solids all the way to the stomach using peristaltic contractions. Two sphincters (upper and lower) prevent the reflux of food particles or gastric acid. Arterial supply of the esophagus originates from the inferior thyroid artery, thoracic aorta, and left gastric artery. Deoxygenated blood is drained by several vessels: inferior thyroid veins, azygos and hemiazygos venous systems, intercostal veins, bronchial veins, and short gastric veins. Innervation is provided by the recurrent laryngeal nerve, sympathetic trunk, and esophageal nervous plexus.

The breasts are secondary sex characteristics in females and the most prominent features of the anterior thoracic wall. The primary function of the female breast is milk production following birth. This function is facilitated by the mammary glands which produce and squeeze the milk into the lactiferous ducts. The breast is attached to the skin of the thorax by suspensory ligaments (of Cooper) overlying two major muscles called pectoralis major and serratus anterior.

They are supplied by several arteries of the thoracic wall, namely branches of the internal thoracic, axillary, lateral thoracic, thoracoacromial, and posterior intercostal arteries. The axillary and internal thoracic veins are responsible for venous drainage, while nervous supply is carried out by branches from the intercostal nerves.

The thorax is the region between the abdomen inferiorly and the root of the neck superiorly.[1][2] The thorax forms from the thoracic wall, its superficial structures (breast, muscles, and skin), and the thoracic cavity.

A thorough comprehension of the anatomy and function of the thorax will help identify, differentiate, and treat the plethora of pathology that can occur within the thorax. This article will review the gross anatomy of the thorax while touching on some clinical implications.

The thoracic wall is formed by 12 ribs, 12 thoracic vertebrae, cartilage, sternum, and five muscles.[1] The thoracic wall functions in movement, respiration, and protection of the thoracic cavity.[3][4]

The thoracic vertebral bodies and intervertebral discs compose the posterior thoracic wall. [4] Each rib articulates with two concurrent vertebral bodies and curves laterally, anteriorly, and inferiorly. The first seven true ribs articulate with the sternum anteriorly. The false ribs 8 to 10 have cartilaginous extensions to communicate with the sternum, while floating ribs 11 and 12 do not communicate with the sternum. The twelve ribs form the bony framework of the thoracic wall, along with portions of the vertebral column.

From superficial to deep, the thoracic wall muscles are the external intercostal, internal intercostal, innermost intercostal, subcostal (posteriorly), and the transversus thoracic muscle (anteriorly).[5] These muscles function in respiration by moving the ribs, thereby changing the volume of the thoracic cavity. Notably, some muscles have attachments to and are superficial to or act as extensions of the thorax. These muscles function to move the shoulder girdle, spine, thorax, and pelvis and assist in respiration.

Breast tissue is present over the anterior thoracic wall superficial to the pectoralis major muscle.[6] Breast tissue is composed of mammary glands, fibrous tissue, fat, the areolar complex, and the nipple.

The thoracic cavity is found deep in the thoracic wall, superior to the diaphragm, and inferior to the root of the neck (thoracic aperture).[2] The thoracic cavity contains organs and tissues that function in the respiratory (lungs, bronchi, trachea, pleura), cardiovascular (heart, pericardium, great vessels, lymphatics), nervous (vagus nerve, sympathetic chain, phrenic nerve, recurrent laryngeal nerve), immune (thymus) and digestive (esophagus) systems.

The thoracic cavity can typically be divided into well-established compartments.[2] The pleural cavities and the mediastinum are the primary constituents. There are two pleural cavities which respectively contain the left and right lungs and the pleura. The mediastinum is central and found between the two bilateral pleural cavities. The mediastinum extends to the inner border of the sternum anteriorly, the inner border of the thoracic vertebral bodies posteriorly, and spans the full vertical length of the thoracic cavity.

The transverse thoracic plane passes through the angle of the sternum (formed by the junction of the manubrium and the body of the sternum). The transverse thoracic plane crosses the T4-T5 vertebral junction and thus divides the superior from the inferior mediastinum.[2] The inferior mediastinum further subdivides into anterior, middle, and posterior compartments by the anterior and posterior surfaces of the pericardium. The anterior mediastinum is anterior to the pericardial sac, the middle mediastinum contains the heart and pericardium, and the posterior mediastinum is posterior to the pericardial sac.

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