The Thoracic Anatomy

The thoracic cavity houses the heart and lungs, two essential thoracic organs that are shielded by the muscles of the chest wall and the bony thorax.

Boundaries

Its boundaries are as follows: anteriorly by the sternum and costal cartilages; laterally by the spine and the ribs plus intercostal muscles; inferiorly by the diaphragm and superiorly by the suprapleural membrane. 

Sternum

The Sternum is a flat bone that is separated into three pieces and is located in the midline of the anterior chest wall. The sternum is divided into three parts: the xiphoid process, the body of the sternum, and the manubrium sternum. Manubrium articulates with the clavicle, first and second costal cartilage. 

In addition, it creates the maniburosternal joint by articulating with the sternum's body. The sternal angle or Louis angle and the maniburosternal joint match. In the anterior region of the chest wall, the maniburosternal joint is felt as a transverse ridge.

Angle Of Louis (Sternal Angle)

Situated between T4 and T5, it is in opposition to the intervertebral disc and corresponds to the second costal cartilage. The trachea splits into the left and right major bronchus at this point. It is the location where the pulmonary trunk splits into the left and right pulmonary arteries. 

The aortic arch begins and finishes at the angle of Louis, and the ascending aorta reaches the end angle of Louis. The angle of Louis is also where the descending thoracic aorta begins. Louis's perspective is also where the rib count begins. The thoracic duct is located on the right side of the chest and curves toward the angle of Louis at the level of T4/T5, which corresponds to the angle of Louis. 

Also Read: Surgical Anatomy and Evaluation of Patient for Thoracic Surgery

RIBS

The ribs are arranged in 12 pairs. There are two types of ribs: usual ribs and atypical ribs. Typical ribs are those from the second to the tenth rib.
The head, neck, tubercle shaft, and Louis angle are characteristics of typical ribs. The head articulates with two vertebrae through its two facets.  One articulates with the vertebrae that match it, while the other articulates with the vertebra above it. 

First, 11th, and 12th ribs are atypical. There is only one facet on the first rib, which is also the shortest and broadest rib. The presentation of the 11th and 12th ribs is atypical, and they do not articulate anteriorly with the sternum or costal cartilages. People refer to them as floating ribs. 

There are two types of ribs: Genuine and Fake.

Since the first seven ribs articulate with the sternum and the eighth through tenth ribs articulate with the costal cartilage of the upper rib, these ribs are sometimes known as vertebrosternal ribs, or vertebrochondral ribs. The coastal margin is formed by the 8th and 10th ribs articulating to the higher rib's coastal cartilage.  The ribs on the 11th and 12th are free or floating.  The eighth through twelfth ribs are regarded as fake ribs. 

Also Read: Anatomy Of The Lungs

Muscles

There are two types of muscles: extrinsic and intrinsic. The levator costarum, as well as the internal, external, and transverse intercostal muscles, are examples of intrinsic muscles. 

There are two types of extrinsic muscles: anterior and superficial muscles.  The major and minor pectoralises. They can be superficial and posterior, such as the Latissimus Dorsi and Trapezium. Deep muscles: Levator, Rhomboid major, Rhomboid minor, and Serratus anterior and posterior.  A vital function is breathing. 

The diaphragm and intercostal muscles are the main breathing muscles.
They cause the thorax's anteroposterior and transverse diameters to grow. The diaphragm expands the chest's vertical diameter.
Tertiary muscles, which comprise the pectoralis, deltoid, and latissimus, provide in ventilatory support in respiratory distress. Secondary muscles are the sternocleidomastoid, serratus anterior, and serratus posterior. 

Also Read: Pleura And Mediastinum 

Tracheobronchial Tree

Trachea measures roughly 11 to 12 centimeters in length.
Cartilage-based rings comprise the trachea. Due to the cartilage only being present in the anterior, these cartilaginous rings are incomplete C-shaped rings. 

The trachea is membrane-covered posteriorly.
• The only fully developed cartilage is the cricoid cartilage.
• There are roughly 18 to 20 incomplete cartilage rings in the trachea.
• The trachea is not firmly attached to the nearby structures.
• There may be some vertical movement.
• The area of the left main bronchus where the aortic sling archetype is most fixed. 

Relationships: When transitioning from a left inferolateral to a right anterolateral posture, the trachea crosses the innominate artery anteriorly.  Azygous arch above the major bronchus on the left.
The trachea and esophagus have a highly crucial relationship; the esophagus lies posterior to the trachea, and the tracheoesophageal groove contains the recurrent laryngeal nerve.

Also Read: Rapid Acquisition Of Key Concepts- Cardiothoracic And Vascular Surgery

Blood Supply

Trachea receive blood supply mostly from the lateral aspect, from the branches of the superior intercostal artery, bronchial artery, and inferior thyroid artery. It is a lateral segmental supply. The significance of surgery  Lateral dissection should not be performed while operating on the trachea. Circumferential dissection shouldn't be greater than two or three centimeters. Since tracheal devascularization, necrosis, anastomosis dehiscence, and necrosis can result after dissection greater than one to two centimeters. 

 The trachea splits into the left and right major bronchus. The right major bronchus is broader, more vertical, and measures about 2.5 cm in length, with the trachea running through it in a straight line.  The left major bronchus is longer, narrower, and oblique.  Several million terminal bronchioles result from the dichotomous division of bronchi.

Between the trachea and the terminal alveoli, there are 23 generations of bronchi.  Traches split into the bronchus of the left and right upper lobes.  The right upper lobe bronchus, also known as the epitherial bronchus, originates above, cranially, or proximal to the pulmonary artery.  The left upper lobe bronchus, also known as the hyparterial bronchus, arises distal to the pulmonary artery. 

An auxiliary bronchus may exist, and it may be located either proximally or distally to the upper lobe bronchus. Pre-eparterial bronchus is the term for the accessory bronchus that arises on the right side, proximal to the right upper lobe bronchus.  Hypearterial bronchus is the term for the accessory bronchus that arises on the left side proximal to the right upper lobe bronchus.  Post-eparterial bronchus is the term for the accessory bronchus on the right side that arises distal to the upper lobe bronchus. Pre-eparterial bronchus is the term for the accessory bronchus on the left side that arises distal to the upper lobe bronchus.

Also Read: Knowing Venous Diseases and How to Treat Them

Hope you found this blog helpful for your Cardiothoracic and Vascular Surgery preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.