Thoracic Wall Anatomy (Bones, Muscles, Vessels & Nerves) - PDF

Thoracic wall: Prepared by / Prof/ Said Zaghloul ------------------------------------------- 1- Thoracic cage 2- Contents of intercostal space 3- Intercostal muscles 4- Intercostal nerves (typical & atypical) 5- Intercostal arteries (anterior & posterior) 6- Intercostal veins (anterior & posterior)...

Thoracic wall: Prepared by / Prof/ Said Zaghloul ------------------------------------------- 1- Thoracic cage 2- Contents of intercostal space 3- Intercostal muscles 4- Intercostal nerves (typical & atypical) 5- Intercostal arteries (anterior & posterior) 6- Intercostal veins (anterior & posterior) Types of joints in the thoracic cage? Chondrosternal junction Secondary cartilaginous joints (synovial joints) Costochondral junction (primary Cartilaginous joints) Intervertebral joints (between vertebral bodies) are secondary cartilagenous joints Classification of the ribs according to attachment with the sternum (true, false, and floating) Ribs are classified into: 1- True ribs (1st – 7th) 2- False ribs (8th – 10th) 3- Floating ribs (11th & 12th) Thoracic cage (skeleton of the thorax ) It is formed : 1- Posterior: by vertebral column (12 thoracic vertebrae) 2- On each side: by ribs (12 ribs which enclose 11 intercostal spaces) 3- Anterior: by sternum & costal cartilages - It has a narrow upper opening (thoracic inlet) may be called by the clinicians thoracic outlet as it transmits great vessels from thorax to the neck - Boundaries of thoracic inlet are (Enumerate ?): 1- Posterior: by 1st thoracic vertebra 2- On each side: by inner borders of 1st rib & its costal cartilage 3- Anterior: by upper border of manubrium sterni - This opening contains: trachea, esophagus, vessels, nerves & the apices of the pleurae & lungs (as the opening is oblique) - Thoracic cage has a lower wide opening (thoracic outlet) which is closed by the diaphragm, it is bounded by: 1- Posterior: by 12th thoracic vertebra 2- Lateral: last 2 ribs & the costal margin (on each side) 3- Anterior: by xiphisternal joint & xiphoid process NB: The costal margin is the fused 7th,8th,9th & 10th costal cartilages  Vertebral levels of sternal parts ?: 1- Upper border of manubrium sterni at the level of the intervertebral disc between T2 & T3 vertebrae (= at lower border of T2 vertebra) 2- Sternal angle at the lower border of T4 Body of sternum 3- Xiphisternal joint at the body of T9  First & second ribs From 3rd to 10th ribs 11th & 12th ribs -1st rib: is atypical Has an upper & lower surfaces No twist in the shaft Head contains single rounded facet - 2nd rib: is atypical No twist in the shaft It has oblique surfaces Typical ribs: (from 3rd to 10th ) 11th & 12th ribs: No neck, no tubercle Head: contains single rounded facet To differentiate : 11th rib is longer than 12th rib & may contain subcostal groove  Posterior end (vertebral end) shows Upper border Head, neck & tubercle (thick & rounded) Superior demifacet for articulation With body of vertebra above Inferior demifacet for articulation With body of corresponding vertebra number Lower border (thin & sharp) Anterior end (sternal end) concave Costal groove Typical rib: (3rd – 10th ): Features are: typical rib has: 1- Upper border: is thick & rounded, 2- Lower border: thin, sharp & contains costal groove (for intercostal VAN) 3- Outer surface: is convex, & inner surface: is concave, 4- Anterior end (sternal end): is concave for costal cartilage , 5- Posterior end (vertebral end): contains head, neck, & tubercle the head contains 2 facets, the tubercle contains single facet (synovial joints) 6- The shaft : is twisted  Anterior end (concave) Groove for subclavian artery & lower trunk Of Brachial plexus Posterior end contains Head, neck & tubercle The head carries single rounded facet - First rib: (it has upper & lower surfaces, it has outer & inner borders) 1- Posterior end: is formed of head (contains single rounded facet), neck, & tubercle 2- Anterior end: is concave, 3- There is no twist in the shaft 4- Outer convex border & inner concave border (contains scalene tubercle) 5- Smooth lower surface (opposite the surfaces of the clavicle) 6- Upper surface: is rough & it contains groove for subclavian vein (in front of scalene tubercle) & groove (behind scalene tubercle) for subclavian artery & lower trunk of brachial plexus Typical thoracic vertebra (superior & lateral views): from 2nd to 8th 7 processes arise from neural arch (vertebral arch): 1. Single spinous process (spine) 2. Two transverse processes 3. Two superior articular processes. 4. Two inferior articular processes. Typical thoracic vertebra (2nd – 8th ): superior view features are: 1- Body : is heart shaped, it contains costal facets (2 demifacets) for the heads of ribs 2- Spine: is long & tapering, 3- Transverse process is long & tapering & contains costal facet for the tubercle of rib Vertebral foramen facet facet Process & facet Facet on transverse Process for tubercle of corresponding rib Superior view of thoracic vertebra  facet facet facet process Process & facet facet Lateral view of typical thoracic vertebra Typical thoracic vertebra (2nd – 8th ): lateral view features are: 1- Body carries 2 facets (demifacets) for corresponding rib & for rib below 2- Transverse process contains facet for tubercle of corresponding rib 3- Spine is long & tapering, superior articular facets are directed backward, & the inferior articular facets are directed forward Costovertebral joints (synovial) ? Intervertebral disc 2ry cartilagenous joint? Synovial joints ? Each typical rib articulates with corresponding vertebra (same number) & vertebra above Each typical vertebra articulates with corresponding rib (same number) & rib below costo-vertebral joints (synovial joints) ? Costotransverse joint (synovial) Costovertebral joint (synovial joint) Note that: The 5th rib articulates with 5th vertebra & vertebra above (4th ) The weakest point of the rib is just in front of the angle (site of twist)? Costochondral junction It is the commonest site of fracture rib? Structures related to the costal groove are intercostal VAN ? It is present along the inferior border of the rib The intercostal space contains (Enumerate ?) : 1- External intercostal muscle (outer layer) = 1st layer 2- Internal intercostal muscle (middle layer) = 2nd layer 3- Innermost intercostal muscle ( inner layer) = 3rd layer 4- Intercostal vessels & nerve (VAN) run between 2nd & 3rd layers of muscles 4- 3- 2- 1-  External intercostal muscle: The fibers are directed downward & forward Origin: from lower border of the rib above inserted into the upper border of the rib below It begins posterior at the tubercle of External intercostal the rib (anterior) membrane External intercostal At costochondral junction, it is muscle replaced by anterior (external) intercostal membrane  Internal intercostal muscle: The fibers are directed downward & backward Origin: from lower border of the rib above inserted into upper border of the rib below It begins anterior at the lateral margin of the sternum At the angle of the ribs it is replaced by the posterior (internal) intercostal membrane Internal intercostal muscle  Innermost intercostal muscle: 1- The fibers are directed downward & backward (the same direction of internal intercostal muscle) 2- It forms an incomplete layer (it is present only in the lateral part of thoracic wall it is absent in the anterior & posterior parts) 3- The intercostal nerve & vessels are superficial to it Innermost Intercostal It may be considered as a part of internal muscle intercostal muscle (separated from it by intercostal nerve & vessels) Intercostal muscles: 1- External intercostal muscle 2- Internal intercostal muscle 3- Innermost intercostal muscle Transversus thoracis muscle (sternocostalis): Origin: from lower ½ of posterior surface of the sternum & xiphoid process Insertion: into the posterior surfaces of the costal cartilages from 2nd to 6th. it has a weak expiratory action Subclavian artery Internal thoracic artery Transversus thoracis (sternocostalis) Musculophrenic artery Diaphragm Superior epigastric artery Subcostal muscle Collateral branches of intercostal VAN Subcostal muscles are bands of fibres present in the inner surface of posterior part (near ribs angles) of lower part of thoracic wall, each one crossing (bridge) 2 intercostal spaces , they blend with innermost intercostal muscles NERVE SUPPLY: of intercostal muscles by the intercostal nerves - Actions: of intercostal muscles are muscles of respiration 1- Inspiration: the 1st rib is fixed by contraction of neck muscles (scalene muscles), the other ribs are raised up toward the 1st rib by contraction of the external intercostal muscles leads to increase the transverse & anteroposterior diameters of thoracic cavity ? NB: contraction of diaphragm (descent) increases the vertical diameter of thoracic cavity ? 2- Forced expiration: the last rib is fixed by contraction of the abdominal muscles (quadratus lumborum), the other ribs are lowered (pulled down) toward the last rib by contraction of internal intercostal muscles decrease in the transverse & anteroposterior diameters of thoracic cavity forcing air out from the lungs ? - This is helped by contraction of muscles of the anterior abdominal wall which fix the diaphragm up Actions of intercostal muscles: 1- The 1st rib is fixed by neck muscles 2- The other ribs are elevated with the Sternum toward 1st rib by contraction Of external intercostal muscles 3- These lead to the increase of both Anteroposterior & transverse diameters Of thoracic cavity ? Movement of sternum upward & forward increase anteroposterior diameter of thoracic cavity (Like pump handle movement) ? Elevation of shafts of the ribs leads to increase transverse diameter of the thoracic Cavity (Like Bucket handle movement) ?  Inspiratory action ? Expiratory action acts in forced expiration ? Are present in the lower posterior part of thoracic wall (near rib angles) cross 2 spaces it blends with Subcostal muscles innermost intercostal Transversus thoracis action: depress ribs it has a weak expiratory action Intercostal nerves (from 1st to 11th) - Are ventral rami of thoracic spinal nerves (T1 – T11) - The nerve runs in the costal groove of the rib above (between 2nd & 3rd layers of intercostal muscles) - Each nerve gives lateral & anterior cutaneous branches - The typical intercostal nerves are from 3rd to 6th - The 7th – 11th intercostal nerves enter the anterior abdominal wall to supply muscles & skin The ventral ramus of T12 nerve is called subcostal nerve  Typical intercostal nerve (from 3rd – 6th ) Origin of intercostal nerve: is the ventral ramus of thoracic spinal nerve ? Intercostal nerves (11 pairs): - Are the ventral rami of thoracic spinal nerves (from 1st to 11th) - Typical intercostal nerve (from 3rd to 6th): - Origin: it is the anterior (ventral) ramus of thoracic spinal nerve - Course: it runs anteriorly between internal & innermost intercostal muscles it ends anterior as anterior cutaneous branch - Branches: (Enumerate ?) 1- Branches to sympathetic trunk (communicating branches) 2- Collateral branch runs along the upper border of rib below 3- Lateral cutaneous branch divides into anterior & posterior branches 4- Anterior cutaneous branch divides into medial & lateral branches 5- Muscular branches to supply intercostal muscles 6- Sensory branches to supply parietal pleura ----------------------------------------------------------------------------------------------- - Atypical intercostal nerves: - 1st intercostal nerve : is very small (as most of the fibers of T1 share in brachial plexus), it has no lateral & anterior cutaneous branches - 2nd intercostal nerve: its lateral branch does not divide into anterior and posterior branches it forms intercostobrachial nerve supplies skin over floor of axilla & medial side of arm - Intercostal nerves (7th to 11th ) enter the anterior abdominal wall supplying its muscles, skin, & peritoneum Typical intercostal Nerve Intercostal arteries Anastomosis between anterior & posterior intercostal arteries Subclavian Back of the artery anterior part of thoracic wall Internal thoracic artery Internal thoracic artery Musculophrenic artery (supplies diaphragm) Artery ends in the 6th intercostal space by division Superior epigastric artery supplies anterior abdominal wall) Give the origin & branches internal thoracic artery ? Internal thoracic artery is a branch of subclavian artery, its branches are ? 1- Anterior intercostal arteries (1st to 6th), 2- Perforating branches to breast 3- Pericardiacophrenic artery, 4- Branches to thymus gland, 5- Mediastinal branches to mediastinum 6- Superior epigastric artery,& 7- Musculophrenic artery  Anterior Intercostal Arteries : 1- Upper 6 spaces: the arteries arise from internal Internal thoracic A thoracic artery 2- Lower 5 spaces: the arteries arise from musculophrenic artery Posterior Intercostal Arteries: 1- Upper 2 arteries from superior intercostal artery (from subclavian artery) 2- Lower 9 (from 3rd to 11th ) arteries from descending thoracic aorta Note the anastomoses between the anterior & posterior intercostal arteries Descending Thoracic aorta Give the origin of anterior intercostal arteries ? Give the origin of posterior intercostal arteries ? Superior Musculophrenic artery Epigastric A  Anterior Intercostal Veins drain into internal thoracic vein Internal Azygos vein Internal thoracic vein is formed at 3rd intercostal Thoracic vein space (by union of vena commitants) it ends in the brachiocephalic vein ? Posterior intercostal veins: - 1st RT posterior intercostal vein ends in the RT brachiocephalic vein ? - Also, 1st LT posterior intercostal vein ends in the LT brachiocephalic vein? - RT superior intercostal vein (drains the 2nd & 3rd RT posterior intercostal veins) ends in azygos vein ? - LT superior intercostal vein (drains the 2nd & 3rd LT posterior intercostal veins) ends in the LT brachiocephalic vein ? - RT posterior intercostal veins (from 4th to 11th ) IVC end in azygos vein ? - In the left side end the hemiazygos veins ? Superior Musculophrenic vein Epigastric vein  Superior vena cava (SVC) Inferior vena cava (IVC) Internal thoracic vein: ------------------- 1- It is formed at the 3rd intercostal space 2- It ends in the brachiocephalic vein? 3- It receives anterior intercostal veins Right superior intercostal vein (drains the 2nd & left superior intercostal vein (drains the 2nd & 3rd RT posterior intercostal veins) & ends in the 3rd Lt posterior intercostal veins) & ends in azygos vein ? the left brachiocephalic vein ? Superior vena cava (SVC) It drains LT posterior intercostal veins Azygos vein: (from 4th to 8th ) ------------ 1- It begins from IVC in the abdomen 2- It ends in the SVC in the thorax 3- It receives hemiazygos veins from Left side 4- It receives RT posterior intercostal veins from the Right side (from 4th to 11th ) 5- It also receives RT subcostal & RT It drains LT posterior intercostal veins superior intercostal veins. (from 9th to 11th ) & LT subcostal vein. Lymphatic drainage of the thoracic wall: A) Superficial lymphatics : end in the axillary lymph nodes. 1- From anterior wall into pectoral (anterior) group of axillary lymph nodes ? 2- From posterior wall into subscapular (posterior) group of axillary lymph nodes ? B) Deep lymphatics : 1- From anterior parts into internal thoracic (parasternal) lymph nodes (present along internal thoracic vessels) ? 2- From posterior parts into intercostal lymph nodes (present along the posterior intercostal vessels) ?  (Internal thoracic lymph nodes) along internal thoracic Along posterior artery intercostal arteries Lymphatic drainage the deep parts of thoracic wall ?