Part 3 - Anatomy of the Thorax PDF

- List the muscles of the thorax - Describe the proximal attachment and distal attachment of each muscle of the thorax - Describe the relationship between the muscles and the bones - Understand the function of the diaphragm  PECTORALIS MAJOR Proximal attachment : Sternum, clavic...

- List the muscles of the thorax - Describe the proximal attachment and distal attachment of each muscle of the thorax - Describe the relationship between the muscles and the bones - Understand the function of the diaphragm  PECTORALIS MAJOR Proximal attachment : Sternum, clavicle and costal margins of ribs Distal attachment : lateral intertubercular groove of the humerus Action : Flexion, adduction and medial rotation of the humerus Innervation : Medial pectoral nerves C8-T1 and lateral pectoral nerves C5-C7  PECTORALIS MINOR Proximal attachment : Rib 3 - 5 anteriorly Distal attachment : Coracoid process of the scapula superiorly Action : Protraction and Stabilization of the scapula against the thoracic wall Innervation : Medial pectoral nerves C8-T1 SUBCLAVIUS MUSCLE Proximal attachment : Rib 1 Distal attachment : Clavicle Action : Stabilize the clavicle Innervation : Nerve to sublavius C5-C6  SERRATUS ANTERIOR Proximal attachment : Lateral border of rib 1 - 8 Distal attachment : Medial margin of scapula posteriorly Action : Protractor and stabilizer of the scapula against the thoracic wall Innervation : Long thoracic nerve C5-C7 INTERCOSTAL MUSCLES ◦ Eleven intercostal spaces in each we have 3 overlapping layers of tissues : 1. EXTERNAL INTERC. 2. INTERNAL INTERC. 3. INNERMOST INTERC. ◦ Nerves and vessels coursing between the 2nd and 3rd layer ◦ They are muscles of respiration  EXTERNAL INTERC. ⁃ first and most superficial layer ⁃ course in an oblique fashion from superior to inferior ⁃ posteriorly from the tubercles of the ribs to the costochondral joint anteriorly ⁃ from the costochondral joint to the sternum as the external intercostal membrane ⁃ move the ribs superiorly ⁃ are most active during inspiration. INTERNAL INTERC. INNERMOST INTERC. - Middle muscle layer - Second layer in the intercostal space ⁃ Deep muscle layer - Positioned at a right angle to the ⁃ Small, thin muscles forming external intercostal muscles the third and deepest layer in - Fills each intercostal space : the intercostal spaces - Anteriorly from the sternum ⁃ Likely aids in depressing the - Posteriorly to the angle of the ribs ribs - Continues as the internal intercostal ⁃ Facilitates expiration membrane from the angle of the ribs to the vertebral column - Function: - Moves ribs inferiorly - Most active during expiration Superficial back muscles TRAPEZIUS LEVATOR SCAPULAE RHOMBOID MAJOR RHOMBOID MINOR LATISSIMUS DORSI INTERMEDIATE MUSCLES SERRATUS POSTERIOR SUPERIOR Origin: Nuchal ligament, spinous processes of vertebrae C7-T3 Insertion: Superior borders of ribs 2-5 Innervation: 2nd-5th Intercostal nerves Function: Elevates ribs SERRATUS POSTERIOR INFERIOR Origin: Spinous processes of vertebrae T11-L2 Insertion: Inferior borders of ribs 9-12 Innervation: Anterior rami of spinal nerves T9-T12 (a.k.a. 9th-11th Intercostal nerves + subcostal nerve) Function: Depresses ribs/ Draws ribs inferoposteriorly  DEEP MUSCLES OF THE BACK ILIOCOSTALIS LONGISSIMUS SPINALIS  DIAPHRAGM Diaphragm muscle: Divides thoracic and abdominal cavities Principal muscle for inspiration and expiration Structure: Composed of: ◦ Peripheral muscular portion ◦ Central tendon Dome-shaped Contraction causes it to descend (flatten) Dome characteristics: Right dome is higher (rests on liver) Left dome is lower (rests on the stomach fundus) Muscular portion regions of origin: Lumbar origin: ◦ Two crura: ▪ Left crus: from the bodies of the upper two lumbar vertebrae ▪ Right crus: from the bodies of the upper three lumbar vertebrae Costal origin: ◦ Muscle fibers arise from the inner surfaces of the lower six ribs Sternal origin: ◦ Muscle fibers arise from the inner surface of the xiphoid process Insertion: Muscle fibers extend centrally to insert into the central tendon  Innervation of the diaphragm: Right and left phrenic nerves provide sensory and motor innervation. Sensory innervation: Pericardium Mediastinal and diaphragmatic pleurae Diaphragmatic peritoneum Motor innervation: Through the phrenic nerve Phrenic nerve arises from spinal roots C3, C4, and C5 Phrenic nerve pathway: Courses along the anterior surface of the anterior scalene muscle on each side Descends into the thoracic cavity between the subclavian vein and artery Accompanied by pericardiacophrenic vessels Travels anterior to the root of each lung between the mediastinal pleura and pericardium on its way to the diaphragm  OPENINGS OF THE DIAPHRAGM Apertures in the diaphragm: Permit passage of structures between the thorax and abdomen Main apertures: Caval, esophageal, and aortic openings Small openings provided by left and right crura Caval opening: Located at the T8 vertebral level, within the central tendon, just right of the midline Allows passage for: ◦ Inferior vena cava ◦ Branches of the right phrenic nerve ◦ Branches of the left phrenic nerve pass through the diaphragm by piercing the central tendon on the left side Esophageal opening: Located to the left of the midline at the T10 vertebral level Splits muscle fibers of the right crus Allows passage for: ◦ Esophagus ◦ Left and right vagus nerves ◦ Esophageal branches of the left gastric artery ◦ Esophageal tributaries of the left gastric vein Aortic opening: Located at the T12 vertebral level, behind the two crura Technically not an opening through the diaphragm but a large gap between the crura Left and right crura form the borders of the opening Allows passage for: ◦ Aorta ◦ Azygos vein ◦ Thoracic lymphatic duct Right and left crura: Greater and lesser splanchnic nerves pass from the thoracic cavity, deep to the crura Left crus allows passage for the hemiazygos vein FUNCTIONS OF THE DIAPHRAGM Functions of the diaphragm: Respiration: ◦ Principal muscle for inspiration ◦ Contracts and flattens to increase the vertical dimensions of the thoracic cavity Venous return: ◦ Contraction and relaxation cause pressure changes in the thoracic and abdominopelvic cavities ◦ Facilitates venous blood return to the heart Valsalva maneuver: ◦ Deep breath and forced contraction of the diaphragm downward on the abdominal viscera ◦ Increases intra-abdominal pressure to: ▪ Aid in expelling vomit, feces, and urine ▪ Prevent gastric reflux by exerting pressure on the esophagus at the esophageal hiatus