Thorax Bony Structure

Thorax Bony Structure

• The rib cage, also known as the thoracic cage, encompasses a bony structure which shields vital organs inside the chest cavity, including the heart and lungs.
• Playing a vital role in respiration, is a crucial component of the thorax
• Twelve pairs of ribs are featured
  • True ribs (1-7) connect directly to the sternum (breastbone)
  • False ribs (8-10) connect indirectly to the sternum by way of the 7th rib's costal cartilage
  • Floating ribs (11-12) connect only to the vertebral column and do not connect to the sternum
• Flat, elongated bone located in the centre of the chest, known as the sternum, consists of three sections, which includes:
  • Manubrium: The uppermost sternum section
  • Body: The middle, also largest sternum section
  • Xiphoid process: The small, bony projection occurs at the bottom of the sternum
• Twelve thoracic vertebrae in the upper spine connects to the ribs at the back
• Costal cartilages are flexible cartilage which connect the ribs to the sternum

Bony Thorax Significance

• Offers vital organ protection from injury
• Expands and retracts during breathing motions aiding with respiration
• Furnishes muscle attachment sites, vital in breathing and posture

Superior Thoracic Aperture

• Also known as the thoracic inlet or thoracic outlet
• Crucial Anatomic Landmark
• It's the opening at the top of the thoracic cavity.
• It is a passageway for several vital structures connecting the neck and thorax

Superior Thoracic Aperture Boundaries

• Posteriorly: The first thoracic vertebra (T1)
• Laterally: The first pair of ribs and their costal cartilages
• Anteriorly: The superior border of the manubrium of the sternum

Superior Thoracic Aperture Structures Passing Through

• The windpipe which leads to the lungs known as the Trachea
• The food pipe connecting the throat to the stomach is known as the Oesophagus
• Primary blood vessels include: common carotid arteries, subclavian arteries and jugular veins
• Nerves: Vagus nerve, phrenic nerve and sympathetic trunks
• Lymphatic vessels: Thoracic duct and lymphatic trunks
• Lung apices: The uppermost portions of the lungs

Superior Thoracic Aperture Clinical Significance

• Thoracic outlet syndrome: Compression of nerves and blood vessels causes pain, numbness and arm/shoulder weakness
• Tumours in the lung apex expand though the superior thoracic aperture and compress surrounding structures, known as Lung cancer
• Abnormal mediastinum growths between the lungs can also compress other structures that are travelling through the superior thoracic aperture, known as Mediastinal masses

Inferior Thoracic Aperture

• The lower opening in the chest cavity, is often sealed by the diaphragm
• Plays a critical role in breathing, injuries and hernias.

Inferior Thoracic Aperture Borders

• Posteriorly: 12th thoracic vertebral body and its transverse processes
• Posterolaterally: 11th and 12th ribs
• Anterolaterally: Costal margins formed by the fused costal cartilages of the 7th to 10th ribs
• Anteriorly: Xiphisternal joint (junction of the xiphoid process and the body of the sternum).

Inferior Thoracic Aperture Key Structures

• Diaphragm forms the "floor" of the thorax and closes this aperture.
• Main breathing muscle
• Several diaphragm openings allow structures to pass between the thorax and abdomen, and includes:
  • Oesophageal hiatus: Allows the esophagus to pass through
  • Aortic hiatus: Allows the aorta to pass through
  • Caval foramen: Allows the inferior vena cava to pass through.
• Major structures including: vagus nerve, phrenic nerve, and splanchnic nerves with lymphatic vessels: Thoracic duct and lymphatic trunks, pass through the inferior thoracic aperture

Inferior Thoracic Aperture Clinical Signficance

• Breathing: Breathing is reliant on the movements of the diaphragm
• Hiatal Hernia may occur: When part of the stomach protrudes through the oesophageal hiatus
• Trauma: Affect structures passing through the aperture

Sternum key features

• Trapezoidal shape feature shown
• Articulates with the clavicles (collarbones)
• The first pair of ribs, feature the jugular notch depression that are important clavicle connection landmarks.
• Body is largest, middle and articulated with ribs 2-7
• Xiphoid process varies in shape and size often pointy. Serves as attachment point abdominal muscles

Sternal Articulations

• With the clavicles forming sternoclavicular joints
• With the costal cartilages of ribs 1-7

Sternal Clinical Significance

• Fractures happens secondary to trauma
• Sternal Puncture supports bone marrow biopsies from the sternum
• Surgical Access requires the sternum to be split
• Deformities support Pectus excavatum and carinatum features

Ribs features and function

• 12 curved rib pairs, forms the primary rib cage structure with categorization such as:
• True ribs 1-7, connects to sternum directly
• False ribs 8-10, connects to sternum indirectly
• Floating ribs 11-12, Only spinal connected
• Short, flat, wide and curved form 1st rib
• Single Facet means only one facet, which articulates with T1 alone
• The 1st Rib contain grooves for vessels (subclavian artery and vein) and lack of angle are typical features.
• Longer and flatter structure forms the 2nd rib with two facets and serratus anterior muscle attachments.
• Classic head, neck, tubercle, shaft and costal groove defines the 8th rib
• Important muscle attachment of 6th rib assists the head, neck and tubercle

Thoracic Wall Movements

• The upper ribs elevate expanding AP dimension, similar to a pump handle being pushed or pulled, for inspiration
• Middle lower ribs elevate widening the transverse expansion described as a bucket handle moving.
• Several combined movements lead to the forced inspiration improving overall chest volume.
• Muscle contraction improves chest height during the inspiration and the chest cavity expands.
• Both cavity size expansion and the movement of diaphragm supports forced inspiration and regular breathing

Thoracic Wall Disruption

• Dislocation displays the way rib moves from sternum
• Separation demostrates the area between the rib and costal cartilage that shifts out of place
• First thoracic vertebrae, first ribs and manutrium creates the thoracic inlet showing "doorway" between the chest and neck

Breast Overview

• Numerous sebaceous glands, particularly along the areola and aids in lubricating through oily substance
• These get larger during pregnancy hormones
• Important for lactation
• Milk will be excreted through lactiferous gland. Conical nipple projections that contain the openings, also support a good latch.
• Unlike other skin in the body, the area contains neither hair nor sweat glands and is surrounded by Montgomery glands.
• Smooth muscle constricted constricts the lactiferous ducts and a release response

Breast Key Glands

• Mammary glands are modified sweat glands and produce milk other than sweat, and in axilla
• Suspensory ligaments, help maintain shape position and extend deeply
• Retromammary space located in pectoral fascia and allow for motion in the breast area
• 15-20 lobules divide and each contain lobules
• Single lactiferous duct lies close in each lobule
• Release of milk is done individual through each duct

Blood pathways in the breast area

• Internal thoracic near the chest supplies the medial mammary part through medial mammary arteries
• Lateral mammary has branches that come from axillary artery and are present in there outer area
• Posterior supplies from throracic aorta to breast from 2-4 area
• Most veins drain to the axillary

Thoracic Walls

• Composed fascia bone and muscle enclosing cavity
• Visible diagram components ribs and costal cartilage beneath. anterior and posterior branches from intercostal nerves help protection and respire

Pectoral Fascia

• Connective tissue that covers and separates pectoralis from the skins while offering muscle support

Pectoralis Major

• Superficial display of muscle assisting arm motions and prominent fibers

Pectoralis Minor

• Triangular muscle under major that supports downward motions with ribs attached

Clavipectoral Fascia

• Support to tissue underneath the major and protects as passageway

Endothoracic Fascia

• Support to lungs and aids respire through protective layering

Muscles of Thoracic Wall

• Serratus posterior superior elevates C7 though T3 processes for properiotion and second to fitth intercoastal
• Serratus posterior inferior depresses, fits throacic spinal process T11 an 9-12 nerves
• Elevates ribs from spinal level for inspiration from transverse areas
• Incostal muscles elevate during the breathing to improve space in those are

Muscles of Intercostal Walls

• Superior borders of Intercostal help elevate through muscles
• Action support inspiration, force and expansion
• Contraction assist with pumping.

Muscles of Transversus, External and Subcostal

• Transversus thoracis: This muscle helps in depressing the ribs, which is important during expiration through intercostal nerves
• External Intercostal: Elevation is a result of assistance by the intercostal nerves through superior areas as part forced expansion
• Subcostal action has similar function for weak depression with proprioception and during the intervals of angles

Nerves

• Vessels run along the intercostal space connecting brain
• 4th area supports sensory motor and 4th intercostal movement

Blood Vessels

• Aorta and veins supports flow superiorly along each side

Muscles

• Several, including external, transverse and internal help support different areas

Surface Arteries

• Thoracic are derived aorta, subclavian and the axillary
• Subcostal are from throacic area
• Intercostal are from subclavian area

Vein Influence

• Azygos has the Intercoastal and runs vertebral side
• Brachiocephalic flows from the subclavian and Intercoastal which supplies the lymph and upper body

Breathing

• Respiratory relies on diaphragm as well as the pleural which separates the lung

Left and RIght

• Lungs features are separated between the lobes, function and structure
• Medial surface displays impressions of areas

Alveolar tree

• The series of tubes including:
  • the segmental and tertiary structures further branch as well as trachea
  • terminal bronchioles allow proper area to breathe.
• Key structures support breathing, blood vessels, and movement

Blood flows

• Vessels to lung enter through pulmonary veins
• Flows is carried from the heart
• Artery transports blood from other areas
• Proper pressure is vital while lactating