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Thoracic Osteology Learning Outcomes •Thoracic osteology: structure and location. •Intercostal muscle attachments, function and innervation •Anatomy of typical intercostal space •Describe the mechanics of breathing •Map of thoracic dermatomes and relevanceOsteology Thoracic Cage Osteocartilaginous cage formed by: •Sternum •12 pairs of ribs •12 thoracic Vertebrae •Thoracic intervertebral discs Encloses: •Heart and great vessels •Lungs and trachea Functions of the Thoracic Cage: •Protect vital thoracic and abdominal organs •Resist the negative internal pressures generated by the elastic recoil of the lungs and inspiratory movements •Provides attachment for the upper limb and supports the weight of the upper limbs •Provides origins for many of the muscles that move and maintain the position of the upper limbs as well as providing the attachments for muscles of the abdomen, neck, back, and respiratory muscles. Ribs Twelve pairs (24 altogether) •True: 1-7 attach directly to sternum through their own CC •False: 8, 9 and usually 10 - their connection to the sternum is indirect th th th •Floating: 11 and 12 (sometimes 10 )- do not connect to sternum, end in posterior abdominal musculatureTypical Rib Atypical Ribs • Rib 1- shorter and wider, only one facet. Superior surface marked by two grooves which make way for the subclavian vessels • Rib 2- longer and thinner than rib 1. Tuberosity for serratus anterior • Rib 10- only has one facet for articulation with its numerically corresponding vertebra • Ribs 11 and 12- have no neck, and only contain one facetQ.Howmanyribs attachdirectlytothe sternum? A) 10 B) 12 C) 7 D) 14 Thoracic Vertebrae •Twelve thoracic vertebrae separated by IV discs •Body •Vertebral foramen •Laminae •Articular processes Atypical Vertebrae •T1- superior facet is not a demifacet as this is the only vertebrae that articulates with the first rib •T10- Single pair of whole facets present which articulate with the 10 rib •T11 and T12- Each have a single pair of entire costal facets which are located on the pedicles Sternum 3 parts: •Manubrium •Body •Xiphoid process In adolescents and young adults, the three cartilaginous joints (synchondroses) that ossify during middle to late adulthood•Manubrium- Widest and thickest of the three part of the sternum Body and Xiphoid process Body •Long, narrow and thinner than manubrium •Extends from T5-T9 vertebrae •Lateral surfaces marked by costal notches Xiphoid process •Inferior end at level T10 •Cartilaginous in the young but ossifies around age 40 •May fuse with sternal body in the elderlyJoints of the Thorax Costovertebral Joints •Joints of heads of ribs- Between the head of the rib, superior costal facet of the corresponding vertebra, and the inferior costal facet of the vertebra above •Costotransverse Joint- Between the tubercle of the rib, and the transverse costal facet of the corresponding vertebra •Both synovial plane jointsJoint of Head of RibCostotransverse Joint Joints between the Vertebrae •Intervertebral Joint- secondary cartilaginous (symphysis) •Zygapophyseal joint (facet joints)- synovial plane joint •Movement- small degree of rotation Intervertebral Disc •Anulus fibrosus- bulging fibrous ring consisting of concentric lamellae of fibrocartilage forming the circumference of the IV disc •Nucleus pulposus is the gelatinous core of the IV disc •Provide strong attachments between vertebral bodies •Permit movement between adjacent vertebrae •Act as shock absorbers Herniated Disc •Nucleus pulposus will herniate out of the anulus fibrosus •the spinal cord or the nerve roots of the cauda equina •Cauda Equina Syndrome- compression of the sciatica, weakness and numbness in legs, numbness around genitals and anus. •Important to ask about bladder control and bowel incontinence Sternocostal Joints st •1 costal cartilage articulates with sternum as a primary cartilaginous joint •2 -7 pairs of costal cartilages articulate with the sternum as synovial plane joints with fibrocartilaginous articular surfaces •The weak joint capsules are thickened anteriorly and posteriorly to form radiate sternocostal ligaments Costochondral Joints •cartilaginous jointsIntercostal Spaces Neurovascular Bundle •Found between internal intercostal and innermost intercostal muscle layers •Found in the costal groove in the inferior surface of each rib VAN •Intercostal vein •Intercostal artery •Intercostal nerve •Neurovascular BundleQ.ApatientcomesintotheEDwithmultipleribfracturesfollowinga RTC.Theyareinagreatdealofpain.Youdecidetogivethemanalgesia viaanintercostalnerveblock.Wheredoyouplacetheneedle? A) Superior border of rib B) Inferior border of ribThoracocentesis through an intercostal space into the pleural cavity to obtain a sample of fluid or remove blood or pus. To avoid damage to the intercostal nerve and vessels, the needle is inserted superior to the rib (usually high enough to avoid damage to collateral branches).Muscles of the Thorax Pectoralis Major •Attachments: • Clavicular head – originates from the anterior surface of the medial clavicle. • Sternocostal head – originates from the anterior surface of the sternum, the superior six costal cartilages and the aponeurosis of the external oblique muscle. • The distal attachment of both heads is onto the intertubercular sulcus of the humerus. •Function: Adducts and medially rotates the upper limb and draws the scapula anteroinferiorly. The clavicular head also acts individually to flex the upper limb. •Innervation: Lateral and medial pectoral nerves. Pectoralis Minor •Attachments: Originates from the 3rd-5th ribs and inserts into the coracoid process of the scapula. •Function: Stabilises the scapula by drawing it anteroinferiorly against the thoracic wall. •Innervation: Medial pectoral nerve. Serratus Anterior •strips, which originate from the lateral aspects of ribs 1-8. They attach to the costal (rib facing) surface of the medial border of the scapula. •Function: Rotates the scapula, allowing the arm to be raised over 90 degrees. It also holds the scapula against the ribcage. •Innervation: Long thoracic nerve. External Intercostals •Attachments: Originate at the lower border of the rib, inserting into the superior border of the rib below. •Actions: Elevates the ribs, increasing the thoracic volume. •Innervation: Intercostal nerves (T1-T11). Internal Intercostals Internal Intercostals •groove and inserts into the superior surface of the rib below. •Actions: The interosseous part reduces the thoracic volume by ribs.ssing the ribcage, and the interchondral part elevates the •Innervation: Intercostal nerves (T1-T11). Innermost Intercostals •Attachments: Originates from the medial edge of the costal groove and inserts into the superior surface of the rib below. •Actions: The interosseous part reduces the thoracic volume by depressing the ribcage, and the interchondral part elevates the ribs. •Innervation: Intercostal nerves (T1-T11) T ransversus Thoracis •Attachments: From the posterior surface of the inferior sternum to the internal surface of costal cartilages 2-6. •Actions: Weakly depress the ribs. •Innervation: Intercostal nerves (T2-T6). Subcostals •Attachments: These originate from the inferior surface of the lower ribs, near the angle of the rib. They then attach to the superior border of the rib 2 or 3 below. •Actions: Share the action of the internal intercostals •Innervation: Intercostal nervesDiaphragmQ. Diaphragm paralysis is caused by damage to what nerve? A) Vagus nerve B) Phrenic nerve C) Internal thoracic nerve D) Diaphragmatic nerveMechanics of Breathing Quiet Breathing Breathing in: •Diaphragm contracts- domes lower •External intercostals- raises ribsMechanics of Breathing Forceful Breathing Exhalation: •Internal intercostals •Innermost intercostals •Abdominal muscles Inhalation •Accessory muscles- sternocleidomastoid, scalene muscles, trapeziusThoracic DermatomesA dermatome is an area of skin in which sensory nerves derive from a single spinal nerve root.Q.Whatspinalnerveiscommonlyassociatedwith referredarmpainduringamyocardialinfarction? A) T2 B) T3 C) T4 D) T5 Herpes Zoster Infection of Spinal Ganglia •Herpes zoster causes a classic dermatomally distributed skin lesion- shingles •Herpes zoster is primarily a viral disease of spinal ganglia, usually a reactivation of VZV (chickenpox) •After invading a ganglion, the virus produces a sharp burning pain in the dermatome supplied by the involved nerve. •The affected skin area becomes red and vesicular eruptions appear.Clinical Thoracic CasesRib Fractures Rib 1- rare due to structure and location muscle-4- protected by scapula and pectoralis Ribs 7-10- most commonly fractured. Weakest part of the rib is just anterior to it’s angle. Symptoms: Pain, particularly during movement Management: Typically, self limiting, resolution within 6 weeks Flail Chest Multiple rib fractures allow a sizeable segment of the anterior and/or lateral thoracic wall to move freely and paradoxically •Inwards during inspiration •Outwards during expiration Extremely painful and impairs ventilation and oxygenation- medical emergency The loose segment may be internally fixated with plates or wires Cervical Rib •A cervical rib is an extra rib that forms above the first rib, growing from the base of the neck just above the collarbone. •You can have a cervical rib on the right, left, or on both sides. It may be a fully formed bony rib or just a thin strand of tissue fibres. •A cervical rib is an abnormality that's present from birth. It's not usually a problem, but if it presses on nearby nerves and blood vessels, it can cause neck pain, numbness in the arm and other symptoms. This is known as thoracic outlet syndrome.Thank You!