True or false: The term thorax refers to the upper part of the torso.
How can the thorax be subdivided? What encloses the subdivision?
The throax can be subdivided into a thoracic cavity enclosed by a thoracic wall.
How is the thoracic cavity subdivided?
Into 3 parts: mediastinum, left and right pleural cavities. pleural cavities are where the lungs lie
What are the functions of the thoracic cavity?
1. breathing: the thorax contains the lungs, ribs, diaphragm, and thoracic wall musculature, all of which play a role in breathing
2. protection of vital organs
3. a conduit for structures passing from one region of the body to another (e.g. the aorta, esophagus)
The _____ divides the thoracic cavity from the abdominal cavity. What kind of muscle (smooth, skeletal, cardiac) is this muscle composed of? What nerve is it innervated by? What types of fibers (GSE, GSA, GVE, GVA)?
2. skeletal (have voluntary control over breathing)
3. innervated by the phrenic nerve (which also innervates the pericardial sac of the heart). note that the vagus nerve passes through the diaphragm but does not innervate it.
4. provides GSE innervation.
The thoracic wall is composed of skeletal elements and muscles. What are these skeletal elements and what boundaries of the thoracic wall do they form?
12 thoracic vertebrae posteriorly
The thorax is continuous with the neck via the _____ ______ ______. Structures of the thorax may enter the abdomen by piercing or passing posterior to the diaphragm which closes the _____ _____ ______.
1. superior thoracic aperture
2. inferior thoracic aperture
The mediastinum is a thick midline partition that extends in an anterior-posterior direction from the ____ to the _____ ____ and in a superior-inferior direction from the ____ ____ ____ to the _____.
anterior to posterior: sternum to thoracic vertebrae
superior to inferior: superior thoracic aperture to the diaphragm
What are the skeletal elements that form the boundaries of the superior thoracic aperture?
body of T1 posteriorly
medial margin of the 1st rib laterally on either side
manubrium of the sternum anteriorly
The margins of the thoracic aperture are formed by bone, cartilage, and ligaments. The aperture is closed by _____. What skeletal structures form the boundaries of the inferior thoracic aperture?
The inferior thoracic aperture is closed by the diaphragm.
Skeletal structures of the inferior thoracic aperture:
body of T12 vertebrae posteriorly
11th and 12th rib posterolaterally (floating ribs)
cartilaginous ends (costal cartilages) of ribs 7-10 anteriolaterally
xiphoid process anteriorly
Which hemidiaphragm (left or right) is more elevated and why?
right hemidiaphragm is more elevated bc of the liver.
How do ribs 1-7 connect to the sternum? Ribs 8-10? 11-12?
Ribs 1-7 connect directly to the sternum through their costal cartilages. Ribs 8-10 connect to the sternum through the costal cartilage of rib 7. Ribs 11 and 12 do not connect to the sternum-floating ribs. sit posteriorly
The pectoral region is ______ to the thoracic wall and consists of superificial and deep compartments. What is contained in those compartments? What arteries supply the breast?
2. superficial: skin, fascia, breasts
deep: muscles and associated structures
3. the breast is supplied by branches of the axillary (lateral thoracic artery), internal thoracic, and intercostal arteries
75% of the lymph from breast tissue drains into axillary lymph nodes. Where else may the lymph go to?
Parasternal lymph nodes that lie all along the sternum
What arteries supply the pecs?
Pectoral branch of thoracoacromial trunk. Also intercostal arteries.
Where do the intercostal vessels and nerves course within the intercostal space? What are 2 artery branches? How many nerve branches are there?
The intercostal arteries, veins, and nerve are located at the inferior border of the superior rib in the costal groove. Note that there are anterior and posterior intercostal arteries and veins but there is only one intercostal nerve in btwn each rib (ventral rami of thoracic spinal nerves).
note: collateral branches are small and will not need to identify in lab.
Any muscles that attach to ribs can aid in respiration. What are some accessory respiratory muscles (other than intercostals)?
scalenes (attach to 1st and 2nd rib, can hypertrophy in ppl with respiratory disease), pectoral muscles
What is the most important fxn of the intercostal muscles as a group?
To maintain tone in the intercostal space (supports the intercostal space).
What is the attachment and fxn of the external intercostal muscles? Where on the chest wall are they best viewed?During what phase of breathing (expiration or inspiration) are they most active?
- most superificial of intercostal muscles
- extend from the tubercle of the rib to the costal cartilage
- do not attach to sternum. are replaced by a CT aponeurosis called the external intercostal membrane that spans btwn the sternum and costal cartilage
- most active during inspiration as they raise the ribs
- best viewed on the anterior-lateral aspect of the chest wall
What is the attachment and fxn of the internal intercostal muscles? Where on the chest wall are they best viewed?During what phase of breathing (expiration or inspiration) are they most active?
- intermediate layer of intercostal muscles
- extend from parasternal region only to the angle of the ribs posteriorly
- replaced by the internal intercostal membrane, which courses medially toward the vertebral column
- most active during expiration as they move the ribs inferiorly
- best viewed on the anterior chest wall btwn the costal cartilage and sternum
What is the attachment and fxn of the innermost intercostal muscles? Where on the chest wall are they best viewed?During what phase of breathing (expiration or inspiration) are they most active?
- least distinct and deepest of intercostal muscles
- most active during expiration as they lower the ribs
- best viewed on the internal aspect of the posterior thoracic wall
The intercostal vein, artery, and nerve bundles course btwn what muscles?
The internal and innermost intercostal muscles.
Describe the arterial supply and innervation to the thoracic wall. (attached pic has nothing to do with question)
There are anterior and posterior intercostal arteries (and veins) and intercostal nerves. The intercostal nerves are ventral rami of thoracic nerves that course in btwn ribs with the arteries and veins. The posterior intercostal arteries are branches of the thoracic aorta. The anterior intercostal arteries are branches of the internal thoracic artery. The internal thoracic arteries are branches of the subclavian artery (see slide 26 of notes). The anteriror and posterior intercostal arteries are the main blood supply to the thoracic wall.
What are two lower branches of the internal thoracic arteries?
musculophrenic and superior epigastric arteries
Describe the venous drainage of the anterior and posterior intercostal veins.
The anterior intercostal veins drain into the internal thoracic veins. The posterior intercostal veins drain into the azygous system of veins.
Identify the layers of the thoracic wall.
What is thoracocentesis and where is it done?
Drainage of pleural space in presence of pleural effusion. Needle is attempted to be stuck btwn intercostal vein, artery, and nerve bundle and collateral branches. less likely to damage smaller collateral branches if stick needle lower.
When the anterior chest wall has been removed, the first structure that is encountered is the _____ pleura of the lungs.
True or false: The phrenic nerve courses anterior to the anterior scalene, anterior to the root of the lung, and are adherent to the pericardial sac. They innervate the pericardial sac as well as the diaphragm.