StructureFunction/ThoraxLecture1

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Current revision as of 00:11, 16 September 2006

Background on the Thorax

• Thorax comes from "breast plate"

 * 1. chest: the part of the body between the neck and the thoracic diaphragm, encased by the ribs. 2. cavitas thoracis.

   * 		§ amazon thorax, a chest with only one mammary gland, or breast.
   * 		§ barrel-shaped thorax, barrel chest.
   * 		§ Peyrot's thorax, a chest that is obliquely oval; seen in large pleural effusions.
   * 		§ pyriform thorax, a pear-shaped thorax, large above, small below.

• Showed CT slice, color slide

• We become more oval in shape as we age, wrt chest wall

• Story of tractor running over farmer; got hemmoraging of the eye because increased pressure of venous blood as tractor compressed contents of thorax and abdomen

   *   ○ BUT HE SURVIVED!
   *   ○ Chest wall constituents: bone, cartilage, joints, muscles

• Midline = median plane • Paramedian Plane: anywhere to the right or left of the median plane

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• Think of all the structures pass through as put a needle into the chest wall ○ Skin ○ Superficial Tissue ○ Pectoralis Major ○ Pectoralis Minor ○ Intercostal Muscles § External Intercostal Muscles § Internal Intercostal Muscles § Innermost Intercostal Muscles • Know which muscles would have to pass through "if thin man trying to get out of fat man", lol ○ Innermost --> internal --> external --> pectoralis minor --> pectoralis major

• Right lung has 3 lobes!

• Diaphragm: strong sheet of muscle inbetween thorax and abdomen

Diaphragma: pl. diaphrag1mata [Gr. "a partition-wall, barrier"] [TA] 1. diaphragm: the musculomembranous partition separating the abdominal and thoracic cavities, and serving as a major thoracic muscle. Called also phren, midriff, diaphragmatic muscle, and thoracic or respiratory diaphragm. 2. a term used in anatomical nomenclature to denote a separating structure. § diaphpelvic diaphragm: the portion of the floor of the pelvis formed by the coccygei and levatores ani muscles and their fasciae. § sellar diaphragm: a ring-shaped fold of dura mater covering the sella turcica and containing an aperture for passage of the infundibulum of the hypophysis.

• Ribs are a.k.a. costal elements • have intercostal elements, or muscles, of which there are 3: § External § Internal § Innermost • Pectoralis § Minor § Major

• Be able to recognize different ribs from which number they are • ○

• §

• ○ "Typical" 6th and 8th ribs and "Atypical" 1st and 2nd, 11th and 12th ribs

• §

Supplementary Notes on Ribs From Anatomy & Physiology-Kaplan Medical.pdf

Sternum The manubrium articulates with the clavicle and the first rib. It meets the body of the sternum at the sternal angle, an important clinical landmark. The body articulates directly with ribs 2-7; it articulates inferiorly with the xiphoid process at the xiphisternal junction. The xiphoid process is cartilaginous at birth and usually ossifies and unites with the body of the sternum around age 40.

Ribs and Costal Cartilages There are 12 pairs of ribs, which are attached posteriorly to thoracic vertebrae.

• Ribs 1-7 are termed "true ribs" and attach directly to the sternum by costal cartilages. 
• Ribs 8-10 are termed "false ribs" and attach to the costal cartilage of the rib above. 
• Ribs 11 and 12 have no anterior attachments, and are therefore classified as both "floating ribs" and false ribs. 

○ The costal groove is located along the inferior border of each rib and provides protection for the intercostal nerve, artery, and vein.

Muscles 1. External Intercostal Muscles a. There are 11 pairs of external intercostal muscles. Their fibers run anteriorly and inferiorly in the intercostal spaces from the rib above to the rib below. b. These muscles fill the intercostal spaces from the tubercles of ribs posteriorly to the costochondral junctions anteriorly; external intercostal membranes replace them anteriorly. 2. Internal Intercostal Muscles a. There are 11 pairs of internal intercostal muscles. Their fibers run posteriorly and inferiorly in the intercostal spaces deep to the external layer. b. These muscles fill the intercostal spaces anteriorly from the sternum to the angles of the ribs posteriorly; internal intercostal membranes replace them posteriorly. 3. Innermost Intercostal Muscles a. The deep layers of the internal intercostal muscles are the innermost intercostal muscles. b. These muscles are separated from the internal intercostal muscles by intercostal nerves and vessels. i. HOW MANY PAIRS OF INNERMOST INTERCOSTAL MUSCLES ARE THERE?

Intercostal Structures 1. Intercostal Nerves a. There are 12 pairs of thoracic nerves, 11 intercostal pairs, and 1 subcostal pair. b. Intercostal nerves are the ventral primary rami of thoracic spinal nerves. These nerves supply the skin and musculature of the thoracic and abdominal walls and the parietal pleura and parietal peritoneum. c. intercostal nerves: branches of the first eleven thoracic spinal nerves, situated between the ribs. The first three send branches to the brachial plexus as well as to the thoracic wall; the fourth, fifth, and sixth supply only the thoracic wall; and the seventh through eleventh are thoracoabdominal in distribution. Called also anterior branches of thoracic nerves, rami anteriores nervorum thoracicum [TA alternative], ventral branches of thoracic nerves, and rami ventrales nervorum thoracicorum [TA alternative]. The primary anterior division of the twelfth thoracic nerve is subcostal rather than intercostal in position and is known as the subcostal nerve (see nervus subcostalis). It differs in course and relationship from the other anterior branches and so is classified separately. 2. Intercostal Arteries a. There are 12 pairs of posterior and anterior arteries, 11 intercostal pairs, and 1 subcostal pair. 3. Anterior Intercostal Arteries a. Pairs 1-6 are derived from the internal thoracic arteries. b. Pairs 7-9 are derived from the musculophrenic arteries. c. NB: There are no anterior intercostal arteries in the last two spaces; branches of the posterior intercostal arteries supply these spaces. 4. Posterior Intercostal Arteries a. The first two pairs arise from the superior intercostal artery, a branch of the costocervical trunk of the subclavian artery. b. Nine pairs of intercostal and one pair of subcostal arteries arise from the thoracic aorta. 5. Intercostal Veins a. Anterior branches of the intercostal veins drain to the internal thoracic and musculophrenic veins. b. Posterior branches drain to the azygos system of veins. 6. Lymphatic Drainage of Intercostal Spaces a. Anterior drainage is to the internal thoracic (parasternal) nodes. b. Posterior drainage is to the para-aortic nodes of the posterior mediastinum.

Mnemonics relating to the ribs

• Cephalic vein has no equivalent artery, an exception

○ cephalic vein: the superficial vein that arises from the radial side of the dorsal rete of the hand, and winds anteriorly to pass along the anterior border of the brachioradialis muscle; above the elbow it ascends along the lateral border of the biceps muscle and the pectoral border of the deltoid muscle, and opens into the axillary vein.

Rete: a general term used in anatomical nomenclature to designate a network, especially of arteries or veins. See also net, network, and plexus. § Accessory cephalic vein: a vein arising from the dorsal rete of the hand, passing up the forearm to join the cephalic vein just above the elbow. § Median cephalic vein: a vein sometimes present as the lateral branch, ending in the cephalic vein, formed by bifurcation of the median antebrachial vein; called also v. mediana cephalica.

• Identify the following structures (Double click on the arrowhead on the left for the answer key): • ○

Imaginary slice across the lung (taylor slide)

1520 TJ

main bronchi

• Identify the following structures (Double click on the arrowhead on the left for the answer key)

• Upper part of chest sometimes called by some thoracic inlet, but also by others thoracic outlet; in this course, will be using thoracic outlet to refer to upper part of thoracic aperture ○ Usually upper part of chest referred to as thoracic outlet ○ Inferior Thoracic Aperture; inferior aperture of thorax: the irregular opening at the inferior part of the thorax bounded by the twelfth thoracic vertebra, the twelfth ribs, and the curving edge of the costal cartilages as they meet the sternum; called also thoracic outlet and inferior thoracic aperture or opening. ○ Thoracic outlet syndrome --> (c sl) symptoms and signs of this problem caused by problems originating in the thoracic outlet) THORACIC OUTLET SYNDROME: § any of a variety of neurovascular syndromes resulting from: □ compression of the subclavian artery, ¨ Arterial compression leads to ischemia, paresthesias, numbness, and weakness of the affected arm, sometimes with Raynaud's phenomenon of the arm. § the brachial plexus nerve trunks, ¨ Nerve compression causes atrophy and weakness of the muscles of the hand and, in advanced cases, of the forearm, with pain and sensory disturbances in the arm. § or less often the axillary vein or subclavian vein, ¨ Venous obstruction usually takes the form of the Paget-Schroetter syndrome. Paget-Schroetter syndrome, Paget-von Schroetter syndrome, a thoracic outlet syndrome in which a thrombus forms in the axillary vein after strenuous exercise; symptoms include pain, edema, and skin discoloration in the shoulder and upper arm. Called also effort thrombosis. § by thoracic outlet abnormalities such as: □ a drooping shoulder girdle, □ a cervical rib or fibrous band, □ an abnormal first rib, □ or occasionally compression of the edge of the scalenus anterior muscle. □ Continual hyperabduction of the arm may cause another variety (hyperabduction s.). § Other types include the cervical rib s., costoclavicular s., and scalenus anticus s.

• Upper chest is an important junctional area ○ What are the structures passing through here?

• SVC blockage is an indicator of lung cancer superior vena cava syndrome, a complex of symptoms caused by compression of the superior vena cava, such as by a bronchial tumor or by metastatic mediastinal lymph nodes in lung cancer; characteristics include suffusion and brawny edema of the face, neck, or upper arms; central nervous system disturbances; cyanosis; conjunctival edema; and edema of the trachea and esophagus leading to dyspnea and dysphagia.