Untitled Quiz

Thorax

• The thorax (or chest) is the region of the body between the neck and the abdomen.
• The bony framework of the thorax consists of the vertebral column, ribs, and their cartilages and the sternum.
• It communicates superiorly with the neck and inferiorly with the abdomen, separated by the diaphragm.
• The bony structure protects the lungs and heart and provides attachments for muscles.

Structure of the Thoracic Cage

• The thoracic cage is composed of the sternum, ribs, and thoracic vertebrae.
• The sternum is a flat bone in the middle of the anterior chest wall. It is made up of the manubrium, body, and xiphoid process.
• The ribs are curved, flat bones. Ribs 1-7 are true ribs, while ribs 8-10 are false ribs and ribs 11-12 are floating ribs. Costal cartilages attach the ribs to the sternum.
• The thoracic wall is formed by the thoracic part of the vertebral column posteriorly, the sternum and costal cartilages anteriorly, and the ribs and intercostal spaces laterally.

Thoracic Openings

• The thoracic cavity has two main openings, superior and inferior.
• The superior thoracic aperture (thoracic inlet) is bounded by the first thoracic vertebra, the first pair of ribs, and the superior border of the manubrium.
• The inferior thoracic aperture (thoracic outlet) is bounded by the 12th thoracic vertebra posteriorly and the xiphisternal joint anteriorly.

The Ribs

• Ribs are curved, flat bones that form the anterolateral part of the thoracic cage.
• Each rib has a spongy interior containing bone marrow that produces blood cells.
• There are three types of ribs: true, false, and floating ribs.
• True ribs (1-7) attach directly to the sternum.
• False ribs (8-10) attach indirectly to the sternum through the cartilage of the rib above.
• Floating ribs (11-12) do not attach to the sternum.

Structure of a Rib

• Typical ribs (3rd-9th) have a head, neck, tubercle, and body (shaft).
• The head has two facets, separated by the crest of the head for articulation with the vertebrae.
• The neck connects the head to the tubercle.
• The tubercle has an articular part for the transverse process of the vertebra and a rough non-articular part for the costotransverse ligament attachment.
• The body (shaft) is thin, flat, and curved. The inner surface has a costal groove. This protects intercostal nerve and vessels

Atypical Ribs

• Atypical ribs (1st, 2nd, 10th, and 12th) have variations in their structure and articulations.
• The first rib has two transverse grooves for the subclavian vessels and lacks a tubercle.
• The second rib has the rough area for the origin of serratus anterior muscle.
• The 10th and 12th ribs have a single facet on the head and do not have a neck or tubercle.

Intercostal Spaces

• Intercostal spaces are the spaces between the ribs.
• There are 11 intercostal spaces.
• The spaces contain intercostal muscles, membranes and two sets of blood vessels and nerves.
• The space below the 12th rib is called the subcostal space.

Intercostal Muscles

• Intercostal muscles help in respiratory movements.
• External intercostals elevate the ribs during inspiration.
• Internal intercostals depress the ribs during expiration.

Intercostal Nerves

• The intercostal nerves are branches of the thoracic spinal nerves.
• They run in the intercostal spaces between the parietal pleura and the posterior intercostal membrane.
• The first six intercostal nerves are mainly within the intercostal spaces though they supply the abdominal wall.
• The 7th to 9th intercostal nerves pass deep to the costal cartilages before entering the abdominal wall.
• The 10th and 11th nerves pass directly into the abdominal wall as the corresponding ribs are floating.

Respiratory Movements

• Quiet inspiration is primarily driven by the diaphragm.
• External intercostals are also involved in inspiration.
• Interosseous portions of the internal intercostals perform the action of expiration.

Thoracic Cavity

• It is the cavity bordered by the thoracic wall and diaphragm.
• It is divided into two primary compartments—the mediastinum and the lungs.

The Sternum

• The sternum is a flat bone located in the midline of the anterior chest wall, consisting of three parts: manubrium, body, and xiphoid process.
• It articulates with the first seven pairs of ribs (the true ribs) via costal cartilages.
• Landmarks include the jugular notch, sternal angle, and xiphisternal joint.

Mediastinum

• The mediastinum is a broad central compartment separating the two pleural cavities, extending from the superior thoracic aperture to the diaphragm.
• It is divided into the superior and inferior mediastinum.
• The inferior mediastinum is subdivided into the anterior, middle, and posterior mediastinum, which contains various structures including the heart, esophagus, trachea, major vessels, and lymphatic tissues.

The Lungs

• Lungs are paired organs, situated laterally to the mediastinum within the pleural cavities.
• Each lung is conical, covered with visceral pleura, and suspended freely.
• The right lung has three lobes (superior, middle, and inferior), while the left lung has two (superior and inferior). The left lung has a cardiac notch.

Bronchopulmonary Segments

• Functional, and surgical units of the lungs.
• The right lung has 10 segments, and the left has 8 to 9.
• Each segment is supplied by a segmental bronchus and associated blood vessels, lymph vessels and nerves.

Pericardium

• A fibroserous sac that encloses the heart and the roots of the great vessels.
• It restricts excessive heart movements and acts as a lubricated container for the heart's different parts during contraction.
• Lies within the middle mediastinum posterior to the body of the sternum and anterior to the 5th-8th thoracic vertebrae.
• Fibrous pericardium is the outer, tough layer attached to the diaphragm and great vessels and sternopericardial ligaments.
• Serous pericardium is the inner, thin layer with visceral (covering the heart) and parietal (covering the inner surface of the fibrous pericardium) parts.

The Trachea

• The trachea is a cartilaginous tube connecting the larynx to the bronchi.
• It is situated in the superior mediastinum.
• The trachea bifurcates into the right and left primary bronchi at the level of the sternal angle.

Blood Supply to Thoracic Wall

• The anterior intercostal arteries supply the upper parts (1-6). Musculophrenic artery supplies lower 7-11 intercostal spaces.
• Posterior intercostal arteries (from descending thoracic aorta) are the supply for intercostal spaces 3 to 11. Supreme thoracic artery from the costal cervical trunk supplies the thoracic wall.

Venous Drainage

• The anterior veins accompany their corresponding arteries.
• The lower 3 drain into the musculophrenic vein, and the upper 6 drain into the internal thoracic vein.
• The posterior veins (11 pairs) drain into the superior vena cava, azygos vein or hemi-azygos veins.

The Diaphragm

• The diaphragm is the primary muscle of inspiration.
• It is a dome-shaped muscle that separates the thoracic and abdominal cavities.
• It has crura, and muscular portions.
• It has openings for the esophagus and vena cava.

Diaphragmatic Hernia

• Congenital or acquired herniation results from incomplete diaphragm development or weak musculature around the esophageal opening.
• Sliding herniae involve the stomach sliding into the thoracic cavity. Paraesophageal hernia involves the stomach pushing into the mediastinum adjacent to the esophagus.

Surface Marking for Parietal Pleura

• Parietal pleura covers the inner surface of the thorax, diaphragm, and mediastinum, and is divided into costal, diaphragmatic, and mediastinal pleura.
• Surface markings define the boundaries of the pleura relative to the ribs, sternum, and vertebral column.

Thoracic Outlet

• The thoracic inlet (superior thoracic aperture) is where major structures enter and leave the thoracic cavity from the neck.
• The thoracic outlet (inferior thoracic aperture) is where structures enter and leave the thoracic cavity from the abdomen.

Clinical notes

• Air in the pleural cavity associated with serous fluid is called hydropneumothorax; with pus is called pyopneumothorax;. With blood, hemopneumothorax. Pus (without air) in the pleural cavity is called an empyema.

Clinical Notes

• Pleural effusion is the abnormal collection of fluid in the pleural space.
• This leads to diminished cough and breath sounds.
• This can be caused by many medical conditions

Heart

• The heart is a muscular pump located in the mediastinum, posterior to the body of the sternum and between the 2nd and 6th rib cartilages and anterior to 5th to 8th thoracic vertebrae.
• It has 4 chambers - left and right atria, and left and right ventricles.
• The heart is supplied by coronary arteries and drained by coronary veins.

Coronary Arteries

• Coronary arteries arise from the aorta and supply blood to the heart muscle.
• Important coronary arteries include: right coronary artery, left coronary artery, circumflex branch and anterior interventricular branch.

Surface Marking of Heart Valves

• Valves of the heart are in close proximity to the chest wall. Correct marking is essential for auscultation (listening to the heart) and other diagnostic procedures.

Auscultation

• Auscultation involves listening to the heart sounds with a stethoscope.
• The heart sounds (lub-dub) are generated by valve closure and contraction/relaxation of the heart muscles.
• Locations of different valves for auscultation are carefully laid out for improved diagnosis.

Lymphatic Drainage of Trachea

• Lymph from the trachea drains into pretracheal, paratracheal lymph nodes, and deep cervical nodes.