Human Anatomy Upper Limbs and Thoracic Wall

Anatomy of Thorax 1

• The lecture covers the anatomy of the thorax, including the thoracic wall, tracheobronchial tree, and thoracic cavity.
• The writer was Ali Alhakeem and Abdullah Alkhars.
• The reviewer was Abdulhameed Alabbadi.
• Learning objectives include: functions, surface features, skeleton, apertures, movements, muscles, fascia, vessels and nerves of thoracic wall; larynx, trachea, bronchi with differences between right and left; pleura and lungs with a focus on differences between right and left lung.

Learning Objectives

• Thoracic wall: structure, functions, surface features, movements of associated muscles, fascia, vessels, and nerves.
• Tracheobronchial tree: larynx, trachea, bronchi, differences between right and left bronchi.
• Thoracic cavity: pleura, lungs, focusing on differences between right and left lung.

Thoracic Wall Main Functions

• Protection: protects vital organs (heart, lungs, great vessels).
• Respiration: facilitates breathing by expanding and contracting during inhalation and exhalation.
• Structural Support: provides rigid framework for attachment of muscles and tissues.
• Movement: allows flexibility for upper limb and neck movements, and aids in rib cage movement during respiration.

Thoracic Wall Surface Features

• Clavicular Notch: located on the manubrium; articulates with the clavicle.
• Sternal Angle (Angle of Louis): junction between manubrium and body of sternum; important landmark for locating rib 2.
• Costal Cartilages: connect ribs to the sternum.
• Intercostal Spaces: gaps between ribs filled with muscles and neurovascular structures.
• Imaginary Lines: help identify structures within the thoracic cavity (e.g., anterior median line, midclavicular line).

Thoracic Skeleton

• Includes ribs (12 pairs), each with a bony vertebral end and a cartilaginous sternal end.
• Sternum (breastbone) made up of manubrium, body, and xiphoid process.
• 12 thoracic vertebrae provide posterior attachment for the ribs.

Ribs

• Classified by articulation into true (1-7), false (8-10, usually), and floating (11-12, sometimes 10).
• True ribs attach directly to the sternum.
• False ribs connect indirectly to the sternum through the cartilage of the rib above.
• Floating ribs do not connect to the sternum.

Thoracic Apertures

• Superior Thoracic Aperture: structures (trachea, esophagus, major blood vessels) pass through.
• Inferior Thoracic Aperture: bordered by the diaphragm.

Sternum

• Corresponds to the vertebral column posteriorly at the level of the intervertebral disc between vertebrae T4 & T5
• Contains the manubrium, body, and xiphoid process.
• Articulation of the 2nd rib and a landmark for internal structures like the end of the ascending aorta, beginning and end of the arch of aorta, and tracheal bifurcation.

Thoratic Vertebrae

• Heart shaped bodies
• Smaller vertebral foramen
• Long, strong transverse processes with facets
• Superior and inferior articular facets; facets laterally and posteriorly
• Long, sloping spinous processes that slant downwards

Ribs - Details

• Head, neck, tubercle, and shaft
• Subcostal groove
• The internal and external intercostal muscles are important players in inspiration and expiration.

Muscles of Thoracic Wall

• External Intercostals: Elevate ribs during inspiration.
• Internal Intercostals: Depress ribs during forced expiration.
• Innermost Intercostals: Assist with respiration.
• Diaphragm: Primary muscle of inspiration; separates the thoracic and abdominal cavities.
• Accessory Muscles: Scalene, sternocleidomastoid, and pectoralis help with deep breathing.

Vessels of Thoracic Wall

• Subclavian artery: supplies blood to upper limb and chest.
• Internal thoracic artery: branches off subclavian, supplies anterior chest wall.
• Aorta: Descending aorta supplies blood to thoracic viscera.
• Intercostal vessels: run in intercostal spaces, supplying muscles, skin, and pleura.

Nerves of Thoracic Wall

• Intercostal nerves: arise from spinal nerves T1-T11; supply motor innervation to intercostal muscles and sensory innervation to the skin and pleura.
• Subcostal nerve: anterior ramus of nerve T12.
• Phrenic nerve: originates from cervical spine C3-5; innervates the diaphragm.
• Vagus nerve: involved in autonomic control of thoracic organs (heart, lungs).

Pulmonary Vasculature

• Pulmonary arteries carry deoxygenated blood from the heart to the lungs.
• Pulmonary veins carry oxygenated blood back to the heart.
• Bronchial circulation delivers blood for nutrition to the supporting structures of the lungs.

Lymphatic Drainage of the Thoracic Wall

• Lymph from the parietal pleura drains to lymph nodes in the thoracic wall (intercostal, parasternal, mediastinal, and phrenic), and from the cervical parietal pleura to the axillary lymph nodes. Lymph from the lung itself drains to the bronchomediastinal trunk.

Pleura

• Serous membrane covering the lungs.
• Two layers: parietal (outer) and visceral (inner).
• Creates a pleural cavity containing fluid to facilitate smooth breathing movements between the lung and chest wall.

Respiratory Tract

• Nasal cavity -> pharynx -> larynx -> trachea -> primary bronchi -> lungs.

Tracheobronchial Tree

• Cartilagenous rings
• Starts at larynx, ends at primary bronchi

Main Bronchi (Right and Left)

• Right bronchus is shorter, wider, and more vertical than the left, leading to more frequent foreign body aspiration into the right lung.
• Left bronchus is longer, narrower, and more horizontal.

Lungs

• Right lung has three lobes.
• Left lung has two lobes.
• Each lung is divided in to lobes, and these lobes are further divided into segments called bronchopulmonary segments.
• There's a cardiac notch on the left lung where the heart is located.

Thoracic Wall Features

• The thoracic wall has features like the sternal notches, clavicle, ribs, and intercostal spaces, forming an area for the attachment of muscles involved in breathing.
• A horizontal surface line is also present on the right lung.