BMS100_Thoracic and AA Muscles Vessels and Nerves.docx

BMS100 – MSK3 THORACIC, ANTERIOR ABDOMINAL WALLS, BREAST - MUSCLES, VESSLES AND NERVES Intercostal muscles: 3 flat layers; external, internal and innermost intercostal muscles (clinically not relevant) Intercostal spaces: 11 intercostal spaces filled with the intercostal muscles and intercostal ner...

BMS100 – MSK3 THORACIC, ANTERIOR ABDOMINAL WALLS, BREAST - MUSCLES, VESSLES AND NERVES Intercostal muscles: 3 flat layers; external, internal and innermost intercostal muscles (clinically not relevant) Intercostal spaces: 11 intercostal spaces filled with the intercostal muscles and intercostal nerves, arteries and veins MUSCLE ORIGIN INSERTION ACTIONS NERVES External intercostal Inferior border of the rib above Superior border of the rib below Moves rib superiorly during inspiration (elevate) Intercostal nerves (T1-T11) Internal intercostal Superior border of the rib below Inferior border of the rib above Moves rib inferiorly during expiration (depress) *Contract during forceful exhalation* Intercostal nerves (T1-T11) Diaphragm: major muscle of respiration; large, dome-shaped muscle sealing off the inferior thoracic aperture Attachments xiphoid process, costal margin, end of ribs 11 and 12, lumbar vertebra (L1-L3) Central tendon: where muscle fibers converge from peripheral attachments of the muscle Action depresses domes (move inferior) = increases volume of thoracic cavity Increase volume = decrease pressure 75% of air in due to diaphragm; 25% due to external intercostal muscles Nerve supply right and left phrenic nerves (C3-C5) Foramina Three foramina in the diaphragm: Aortic hiatus (T12 level) – for aorta Esophageal hiatus (T10 level) – for esophagus Caval opening (T13 level) – for inferior vena cava Mammary glands: modified sweat glands in superficial fascia (subcutaneous layer) Areola: circular pigmented area of skin surrounding the nipple (T4) Borders – medial parasternal line, lateral mid-axillary line, superior rib 2, inferior rib 6 Lymphatic Drainage 75% into axillary nodes Rest in parasternal lymph Suspensory ligament: extension of deep pectoral fascia; holds the weight of the gland Clinically useful to examine for tumors – pull on ligament to pull on skin THORACIC WALL, PECTORAL REGION, AND ANTEROLATERAL ABDOMINAL WALL REGION ARTERIAL SUPPLY VENOUS DRAINAGE NERVE SUPPLY THORACIC WALL Posterior intercostal arteries Runs along inferior border of each rib Branches off the thoracic aorta (descending) – consists of segments = ascending aorta, aortic arch and descending thoracic aorta Anterior intercostal arteries Rub along superior border of each rib running in costal groove Branches off the internal thoracic artery (internal mammary artery) directly or indirectly Posterior intercostal veins Drain on right side azygos vein Drain on left side hemiazygos or accessory hemiazygos Anterior intercostal veins Drain (directly or indirectly) internal thoracic veins drain into right and left brachiocephalic veins Intercostal nerves (T1-T11): main source; anterior rami of upper thoracic spinal nerves Runs in costal groove along inferior border of rib Divides into two branches once it emerges from intervertebral foramina Supplies motor and sensory innervation to intercostal muscles, skin of chest wall and parietal pleura Lower intercostal – supply skin/muscles and parietal peritoneum of the abdominal wall Subcostal nerve (T12): anterior ramus of the spinal nerve T12 Runs below the 12th rib Supplies innervation to muscles and skin in subcostal region Phrenic nerves (C3, C4, C5): not primarily thoracic nerves but originate from C3-C5; travel through thorax and play crucial role in innervating diaphragm PECTORAL REGION Axillary artery Mainly lateral thoracic branch and internal thoracic artery 2nd to 4th intercostal arteries Axillary vein Internal thoracic vein Intercostal veins 2nd to 6th intercostal nerves Nipple – innervated by 4th intercostal nerve ANTEROLATERAL ABDOMINAL WALL Superior epigastric artery: direct continuation of the internal thoracic artery (originally from subclavian artery) Runs inferiorly along posterior surface of rectus abdominis supplies upper part of anterior abdominal wall Inferior epigastric artery (IEA): branch of external iliac artery Runs superiorly along medial side of the deep inguinal ring supplies lower part of anterior abdominal wall Superficial epigastric artery: branch of femoral artery Runs superiorly and medially along inguinal ligament supplies skin and subcutaneous tissue of lower abdomen Intercostal arteries Superior epigastric vein Inferior epigastric vein Superficial epigastric vein Peri-umbilical veins: network of veins situated in region of umbilicus; drains into axillary or femoral veins Thoracoabdominal nerves (T7-T11) Includes: anterior cutaneous branches and lateral cutaneous branches Run along costal margin and provide sensory information to skin and muscles (anterior side of wall) Iliohypogastric nerve (L1) Runs along iliac crest and provides sensory innervation to lower abdominal wall and pubic region Ilio-inguinal nerve (L1) Runs close to Iliohypogastric nerve and provides sensory and motor innervation to abdominal and inguinal regions Intercostal nerves Main role is to innervate the thoracic wall but provides innervation to muscles and skin of the upper abdominal wall