Thoracic Cavity Organization 3 major spaces mediastinum right / left pulmonary cavities 2 apertures superior / inferior True Ribs Vertebrocostal (Ribs 1 - 7) Attach directly to the sternum via costal cartilages False Ribs Vertebrochondral (Ribs 8 - 10) Attach to the costal margin Floating Ribs (Ribs 11 & 12) Do not attach to the sternum Typical Ribs (Ribs 3 - 9) - Head (2 facets) - Neck - Tubercle - Body / Angle - Costal groove - Costal cartilage Superior Atypical Ribs (Ribs 1-2, 10-12) 1^st Rib: - grooves for subclavian BVs - 1 articular facet on head - tubercles for ant. / mid. scalene 2^nd Rib: - 1 articular facet - tubercle for posterior scalene Inferior Atypical Ribs (Ribs 1-2, 10-12) Rib 10: - 1 articular facet Ribs 11 & 12: - 1 articular facet - floaters - no necks / tubercles Which is the only atypical rib to have similar structure at the head as the typical ribs? Rib 2 (2 articular facets) Anatomical appearance of the breast - mainly subcutaneous fat - modified apocrine sweat gland - lobules drains into lactiferous ducts - supported by suspensory ligaments - 2/3 pec. major & 1/3 serratus ant. - retromam. space = movement - lateral region = axillary tail Anatomical levels of breast / nipples Breast: ribs 2-6 Nipple: 4^th intercostal space (males!) Arterial supply to the breast 1. Lateral thoracic a. (lateral mammary branches) 2. Internal thoracic a. (medail mammary branches) 3. Post. intercostals (2-4 intercostal spaces) Venous drainage to the breast 1. Axillary v. (via lat. mammary vv.) 2. Internal thoracic v. (via medial mammary vv.) Venous drainage can reach the azygous system via intercostal veins Innervation of the breast Ant. / Lat. cutaneous branches of 2^nd - 6^th intercostal nn. (sensory / smooth muscle signals) Innervation of the nipple 4^th intercostal n. Lymphatic drainage of the breast Subareolar lymphatic plexus 75% -> axillary nodes -> r. lymphatic / thoracic ducts (some in parasternal nodes) Lat. branches of post. intercostals -> azygous system -> thoracic duct some drainage into subdiaphragmatic nodes / liver Anterior muscles of forceful respiration Pec. major clavipectoral fascia Pec. minor Major contributors of respiration External intercostals - membranous anteriorly Internal intercostals - membranous posteriorly Innermost intercostals - membranous anteriorly & posteriorly Which intercostal muscles are continuous w/ abdominal muscles? External intercostals (external oblique) Internal intercostals (internal oblique) Arterial supply to thorax 2 main sources: posterior intercostal aa. - most arises from thoracic a. - upper 2 arise from superior thoracic a. (branch of costocervical trunk) anterior intercostal aa. (usually paired) - arises form internal thoracic aa. (subclavian aa.) What are the terminal branches of the internal thoracic aa. in the thorax? 1) superior epigastric aa. 2) musculophrenic aa. - supplies the lower spaces - anastamoses w/ post. intercostals) Venous drainage of thorax Parallels arterial supply except for azygos system Ultimately drains via 2 routes: 1) Internal thoracic vv. - drains into brachiocephalic vv. 2) Azygos system - drains into superior vena cava Innervation of thorax - intercostal n. (ant. rami T1-11) - subcostal n. (ant. rami T12) - intercostal branches carry sympathetic motor to smooth muscle (i.e. vasculature / erector pili / hair follicles) Intercostal Spaces: Boundaries & Contents lateral border = internal intercostal m. medial border = innermost intercostal m. Contents (superior to inferior) VAN + collateral branches Structures that pass thru diaphragm @ T8 Caval hiatus passes through central tendon: - IVC - R. Phrenic n. - Pericardiacophrenic a. Structures that pass thru diaphragm @ T10 Esophageal hiatus passes through muscular diaphragm: - Esophagus - Vagus n. Structures that pass thru diaphragm @ T12 Aortic hiatus passes posterior to diaphragm: - Thoracic aorta - Thoracic duct Innervation / Blood Supply to Diaphragm Blood supply - branches of abdominal aorta (major) - thoracic aorta / intercostals / pericardiacophrenic / musculophrenic (minor) Innervation - Phrenic n. (C3-C5) penetrate diaphragm and innervate it from underneath At what point do the parietal and visceral pleura become continuous? Hilum of the lung (T5-T7) pleura reflects back on itself extends inferiorly as pulmonary ligament Endothoracic fascia - loose CT layer - separates the parietal pleura from internal surface of thoracic wall Costodiaphragmatic Recess Below 6^th rib (MCL) Below 8^th rib (MAL) Lobes of the lungs Each lung has 10 bronchopulmonary segments Right Lung (3 lobes) - separated by horizontal / oblique fissures Left Lung (2 lobes) - separated by oblique fissure Right Lung - Mediastinal surface Anteriorly: - groove for SVC - cardiac impression - pulmonary a. - pulmonary v. Posteriorly: - groove for azygos arch - groove for esophagus - Bronchus Left Lung - Mediastinal surface Anteriorly: - large cardiac impression - groove for subclavian a. - pulmonary v. - lingula Posteriorly: - groove for aortic arch / descending aorta - pulmonary a. - bronchus - pulmonary v. Right bronchial tree Trachea -> R. main bronchus -> R. superior (eparterial) bronchus -> R. middle / inferior bronchi Arterial supply to lung Bronchial arteries (branches of descending aorta) Venous drainage of lung Bronchial veins (right into azygos v. / left into hemiazygos system) Why can't blood oxygenation reach 100%? Inside lungs, bronchial veins unite w/ pulmonary v. Delivers low oxygenated blood to right atrium Thoracic autonomics Parasympathetics - Vagus n. (constrict) Sympathetics - sympathetic trunks (dialate)