Lecture 2.1 - Thoracic Wall and Lungs Flashcards
Thorax?
- region of trunk between neck and abdomen
- thoracic wall: skin, fascia, nerves, vessels, muscle, bones, and breast
- thoracic cavity: heart, lungs, thymus, distal trachea, esophagus
Skeleton of Thoracic Wall?
- osteocartilaginous thoracic cage:
- - sternum, 12 pairs of ribs and costal cartilage, and 12 thoracic vertebrae and intervertebral discs
Superior thoracic aperture (thoracic inlet)?
- access for thoracic cavity to communicate with the neck; measures AP 5 cm and 11 cm transversely; slopes downward and forward
- bounded by T1, 1st rib and costal cartilage, and superior border of manubrium
What structures are passed through in the superior thoracic aperture?
trachea, esophagus, common carotid arteries, jugular veins, subclavian artery/veins, vagus and phrenic nerves, thoracic duct
Thoracic Outlet Syndrome (TOS)?
implies compression at the superior thoracic outlet, involving neuro-vascular bundle (brachial plexus and subclavian vessels) causing parasthesia, numbness, cyanosis, thrombosis in upper limb
Inferior thoracic aperture (thoracic outlet)?
- access for thoracic cavity to communicate with the abdomen
- closed by thoracic diaphragm
- slopes downward and backward
- bounded by T12, 12th rib and costal margins, xiphisternal joint
What are the parts of the Sternum?
- manubrium: jugular (suprasternal notch), clavicular notch, manubriosternal joint
- body: costal notches, xiphisternal jiont
- xiphoid process
Contents of Vertebrae in general?
- body supports body weight
- superior and inferior articular facets for articulation with other vertebrae; restricts movement
- transverse/spinous process for muscle attachments
Specific to Thoracic vertebrae?
- costal facets on bodies for articulation with head and ribs
- costal facets on transverse process for articulation with tubercles of ribs
- long, inferiorly-directed spinous processes
- inferior articular facets face anteriorly
How are the ribs divided?
- True ribs: 1-7, vertebrocostal ribs
- costal cartilage attaches directly to sternum
- False ribs: 8-10, vertebrochondral ribs
- costal cartilage attaches to costal cartilage of rib 7
- Floating ribs: 11-12, no attachment to sternum
Muscles of thoracic wall?
- 3 layers of intercostal space:
- external intercostal muscle (superficial layer)
- internal intercostal muscles (middle layer)
- innermost intercostal muscle (deepest layer) - only present laterally
- all innervated by intercostal nerves
What is found in each intercostal space?
- a posterior intercostal vein and artery, and an intercostal nerve is found in each intercostal space
- the vessels and nerve lies between the internal and innermost intercostal muscles
What is the thoracic cavity? What are its 3 compartments?
- space within thoracic walls
- 3 compartments:
- 2 lateral compartments: right and left pulmonary cavities
- one central compartment: mediastinum
What are the components of the pulmonary cavities?
- lungs and pleurae (lining membranes)
- lungs: essential organ of respiration
- pleurae: serous pleural sac consisting of 2 continous membranes
What are the 3 different types of Pleurae?
- parietal pleura (outer lining)
- lines the inner surface of the thoracic wall and the mediastinum
- 4 parts: costal, diaphragmatic, mediastinal, cervical (cupola)
- visceral pleura (inner lining)
- invests the lungs and cannot be dissected from lungs
- pleural cavity
- potential space between visceral and parietal pleura, filled with pleural fluid which acts as a lubricant
Where do the lungs attach? How is it divided and what’s the apex?
- attaches to pulmonary vessels and trachea
- apex: blunt superior end
- divided into lobes by horizontal and oblique fissures
Lobes of lungs?
- right lung: larger, heavier
- 3 lobes: superior, middle, inferior
- left lung
- 2 lobes: superior, inferior
Where does the trachea begin? What is it made of? And what does it divide into?
- begins at cricoid cartilage
- 16-20 incomplete hyaline cartilaginous rings
- divides into right and left primary bronchi and the level of sternal angle
- carina: division point; it is a keel like projection on the inside; most sensitive area of trachea; last line of defense before entering lungs; carcinomatous lymph nodes widen the carina
Trachea cross-section anteriorly, laterally, and posteriorly? What is the action of the trachealis muscle?
- anteriorly and laterally: cartilaginous structure
- posteriorly: trachealis muscle; action: constricts the trachea, allowing for higher velocity of air during coughin
How are the bronchi divided and how are they differentiated?
- R primary bronchus: wider, shorter, more vertical
- food and other foreign particles more often go into the right primary bronchus
- L primary bronchus:
- closer to pulmonary trunk and aorta
- each primary bronchus divides into secondary lobar bronchi and then into tertiar segmental bronchi
How does circulation occur into the bronchi?
- each segmental bronchus is accompanied by a segmental artery and vein for gas exchange
- thus, each bronchopulmonary segment operates independently, and can be surgically removed if diseased
What is the diaphragm? Shape? What does it separate?
- chief muscle of inspiration
- dome-shaped
- separates thoracic cavity from abdominal cavity
What are diaphragmatic apertures? Name them and their location.
- permits structures to pass between thorax and abdomen:
- Caval opening: inferior vena cava between T8-T9
- esophageal hiatus: esophagus at T10
- aortic hiatus: aorta, does not pierce diaphragm and passes posterior to median arcuate ligament and anterior to T12
Actions of diaphragm?
- contraction moves dome inferiorly
- pushes abdominal viscera inferiorly
- increase volume of thoracic cavity
- allows air to be taken into the lungs
- diaphragm also important in circulation of blood, in abdominal straining (as in micturition, defecation and parturition), and in weight-lifting
Muscles of inspiration?
- diaphragm, external/internal intercostal, sternocleidomastoid, scalenes, serratus posterior superior, levator costarum
What does the diaphragm do in inspiration? The ribs? Pleural cavities and lungs? Abdomen?
- diaphragm contracts
- dome pulls inferiorly
- vertical height of thorax increases
- intrathoracic pressure decreases
- ribs elevated
- passively during relaxed inspiration
- actively during forced inspiration
- pleural cavities and lungs enlarge
- air rushes passively into lungs (not pumped in)
- abdominal pressure increases due to decreased abdominal volume
Muscles of expiration?
normal: elastic recoil of lungs
forced:
- rectus abdominus, internal intercostals, external/internal abdominal oblique, transversus abdominus, serratus posterior inferior
What does the diaphragm do in expiration? Lungs? Ribs? Abdomen?
- diaphragm and intercostal muscles relax
- thoracic volume decreases
- intrathoracic pressure increases
- stretch elastic tissue of the lungs recoilds (like and inflated balloon releasing its air)
- air is expelled
- ribs are depressed
- abdominal pressure is decreased
What are the nerves of the diaphragm and where doe they arise from?
- motor supply is from the phrenic nerves
- arise from ventral rami C3-C5
- sensory supply primary from phrenic nerves (centrally)
- some from intercostal and subcostal nerves (peripherally)
What is the posterior intercostal artery a branch of? What do the posterior intercostal veins drain into?
- artery: direct branches of the descending aorta.
- vein: drain into hemiazygos vein (left) and azygos vein (right)
