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Thorax

Thorax. The Muscles of the Thorax: - consist of muscles w/ varying characteristics: a. connect adjoining ribs ( intercostales - externi , interni & intimi ) b. span several ribs ( subcostales ) c. connect ribs to sternum ( transversus thoracis )

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Thorax

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  1. Thorax

  2. The Muscles of the Thorax: - consist of muscles w/ varying characteristics: a. connect adjoining ribs (intercostales - externi, interni & intimi) b. span several ribs (subcostales) c. connect ribs to sternum (transversusthoracis) d. connect ribs to vertebrae (levatorescostarum, serratus post sup. & inferior) e. diaphragm

  3. Intercostales: - thin superimposed layers of muscle & tendinous fibers occupying the intercostal spaces External intercostal Internal Intercostal Innermost intercostal

  4. Intercostalesexterni: - 11 in number on each side - extend from tubercle of rib to cartilage of rib in front - muscle passes from lower border of 1 rib to upper border of rib below - fibers directed obliquely downwards & laterally

  5. Intercostalesinterni: • - 11 in number on each side • starts at sternum & extends backwards to • post. costal angles • - origin - costal groove • - inserts - upper border • of rib below • - fibers are directed • obliquely & at • right angles to • external intercostals • - actions: • - elevators of ribs • during respiration

  6. Intercostalesintimi(inner most intercostal): • merely as internal laminae of int. intercostalmuscle • Separated from it only by neurovascular bundle • - attached to internal aspects of 2 adjoining ribs • - insignificant & sometimes absent • - actions: • - act in conjunction • w/ internal • intercostalmuscle

  7. Subcostals: - consist of muscular & aponeuroticfasciculi - usually well developed only in lower part of thorax - descends from inner surface of 1 rib to internal surface of 2nd or 3rd rib below - action: - depresses ribs

  8. Transversus thoracis: - on internal surface of anterior wall of thorax - origin: - lower 3rd of post surfaces of body of sternum - xiphoid process - costal cart of lower 3 or 4 true ribs near sternal ends - insertion: - lower borders & inner surf of costal cart of 2nd, 3rd, 4th, 5th & 6th ribs - action: - draws down costal cartilage

  9. Levatorescostarum: - 12 on each side - origin - ends of transverse processes of C7 & T1 to T11 - pass obliquely downwards & laterally - insertion - upper edge & external surface of rib below vertebra - nerve supply: - lat branches of dorsal rami of corresponding thoracic nerves - action: - elevate ribs

  10. Serratus posterior superior: - thin, quadrilateral muscle, external to upper & posterior part of thorax - origin: - lower part of ligamentumnuchae - spines of C7 & upper 2 TV - supraspinous ligaments - insertion: - upper bord & ext surf of 2nd, 3rd, 4th & 5th ribs - nerve supply: - 2nd, 3rd, 4th & 5th intercostal nerves - action: - elevate ribs

  11. Serratus posterior inferior: • thin, irregular quadrilateral muscle at the junction of Thoracic Vertebrae & Lumbar Vertebrae • - origin: • - spines of lower 2 TV & upper 2-3 LV • - supraspinous ligament • - insertion: • - inf borders & surfaces of lower 4 ribs • - nerve supply: • - ventral rami of 9th to 12th thoracic spinal nerves • - action: • - draws lower ribs downwards & backwards

  12. Diaphragm: - a dome-shaped, musculofibrous sheet - separates thoracic fr. abdominal cavity - periphery is made up of muscle fibers attached to circumference of thoracic outlet - muscle fibers converge into a central tendon

  13. - muscle fibers may be grouped into 3 parts: a. sternal part - arises from back of xiphoid b. costal part - from interior surface of cartilage of lower 6 ribs c. lumbar part - arises from 2 aponeurotic arches (medial & lateral arcuate ligaments) & LV by 2 pillars - Central Tendon: - thin but strong apon. of closely interwoven fibers near center of dome

  14. The Diaphragmatic Apertures: a. Aortic aperture - lowest & most posterior - level = T12 - Aorta, Thoracic duct, azygos & hemiaztgos veins b. Esophageal aperture - level = T10 - Esophagus, vago-sympathetic gastric nerves, L gastric vessels c. VanaCaval aperture - level = T8 - IVC & br of R phrenic nerve d. 2 lesser apertures - greater splanchnic nerve - lesser splanchnic nerve

  15. - nerve supply: - motor fibers - phrenic nerves - sensory fibers - lower 6 or 7 intercostalnerves to the periphery - actions: - essential muscle of inspiration - give additional power to all expulsive acts - fibers of right crus exert a sphincteric action on lower end of esophagus

  16. Thank You!

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