Thorax Flashcards
Thorax
Between neck and abdomen
Contains major organs of circulation and respiration
In the cavity of the thorax are two lungs occupying the lateral areas.
Between the lungs is a thick mobile partition called the mediastinum. All other structures in the thoracic cavity are in the mediastinum, e.g., the trachea, the heart and the great vessels, the esophagus, the sympathetic trunk, the vagus and phrenic nerves, and the thoracic duct.
Functions
Breathing
Protection
Conduit
Ribs
Costal cartilages of 1-7 articulate with sternum
Costal cartilages of 8-10 articulate with superior costal cartilage
11 and 12 are floating ribs. They do not attach anteriorly.
Boundaries of Thorax
Anterior: The sternum and the anterior ends of ribs and costal cartilages
Posterior: 12 thoracic vertebrae, posterior parts of the ribs
Lateral: The ribs
Superior:
The body of the 1st thoracic vertebra, the 1st ribs and costal cartilages and the upper border of the sternum. These bones form the boundary of the thoracic inlet. The thoracic inlet is continuous superiorly with the root of the neck.
Inferior:
The diaphragm. This has apertures through which structures communicate between the thorax and the abdomen. (thoracic outlet)
Sternal Angle
Landmark for: Second rib Disc between T4 and T5 Separates superior from inferior mediastinum Superior limit of pericardium Beginning and end of arch of aorta Trachea bifurcates Superior limit of pulmonary trunk Arch of azygos vein empties into SVC Where thoracic duct crosses from right to left of midline
Costal Groove
contains the intercostal neurovascular bundle and is important when doing plural taps.
Important Relationships with Neck
1) Brachial plexus outflow (in interscalene triangle)
2) Subclavian vein (anterior to the anterior scalene along with the phrenic nerve)
3) Scalene (Anterior) muscle (attaches to the first rib and the anterior tubercle of the of the transverse processes of C3-C6)
4) Pleural dome (dome of lungs) sits in neck and can be punctured, causing a collapsed lung
Central Venous Line
Catheter is then threaded down the right brachiocephalic vein and into the superior vena cava
to monitor central venous pressure and for rapid infusion of IV fluids
Error could puncture pleural dome and cause PNEUMOTHORAX
Cervical Rib
1) Compression of subclavian
artery
2) Compression of brachial
plexus
causing cold hands or tingling pain
Blood Supply to Body Wall
Posterior intercostals are branches of aorta
Anterior Intercostals are branches of internal thoracic a
Most of the blood supply to the thoracic area comes off in the POSTERIOR MEDIASTINUM that are called intercostal a. and are PAIRED At every intercostal space a branch comes off
the anterior and posterior intercostal run around and anastomosose somewhere near the mid axillary line
The neuromuscular bundle runs between the internal intercostal muscle and the innermost intercostal muscle
NOTE some muscles run across 1,2,3 intercostal spaces and attach to the sternum –they are called TRANSVERSUS THORACICUS and they play a role in depressing the space between the ribs (expiration)
Intercostal Muscles
External
Internal: runs at a right angle to external
Innermost: deepest layer and runs in same direction as internal
Thoracic Cavity
Contains:
1) Pleural cavities- and lungs
2) Mediastinum- 4 parts
middle mediastinum- contains the heart
Pleura Cavity
Pleura cavity is a very small space with the lungs inflated and contains a small amount of serous fluid
Visceral Pleura-
covers the lungs
Parietal Pleura- cover the ribs (costal cartilages) mediastinum
diaphragm cupula- root of neck; wall of pleural cavity
Pleural Recesses-
parts of the pleura cavity not occupied by lungs except by deep inspiration
Pleural Reflections-
where parietal pleura “reflects” back at a sharp angle
lung ends at 6th rib but pleura goes down to 8th rib.
Lungs are surrounded by (not inside) the pleural cavities
Pleural cavities do not communicate with each other
Extend above level of rib 1
Potential space
Contain only thin layer of serous fluid
Diaphragm
Muscle fibers arise from margins of inferior thoracic aperture
Balloons into domes
Right dome reaches to rib 5
Aorta passes behind: T 12
Esophagus pierces at T 10
Vena Cava pierces at T 8
Function—-Respiration
higher in the front than in the back and its dome shapes higher on the right and lower on the left
Respiration
Since thorax is sealed (ie. Closed system) anything that expands the thorax will aid respiration (inspiration)
diaphragm drops way down to T12, the pleura ends about T12, kungs drop to T10
Muscles of inspiration
External intercostals, part of internal intercostals
Elevate ribs and are innervated by intercostal nerves
(function energetic breathing)
Diaphragm
Dome descends, elevates lower ribs
Innervated by phrenic nerves (C3,4,5)
(function in quiet sleeping breathing)
Anterior Middle Posterior Scalene elevate ribs
Sternocleidomastoid- elevates sternum
Pectoralis muscle- can aid
forced inspiration so can serratus anterior if scapula is fixed in place
**ANYTHING THAT DEPRESSES RIB CAGE = EXPIRATION (Abdominal Muscles, Internal intercostal but not chondral portion
Lungs
Right: Left:
3 lobes 2 lobes
larger cardiac notch
heavier oblique fissure only
shorter
wider
fissures:
oblique
horizontal
Lung Hilus
only place where things enter and exit between lungs
large triangular depressed area on the lung that is located just superior to the center of the mediastinal surface and behind the cardiac impression of each lung, and is found nearer to the back border than to the front.
The rib cage is separated from the lung by a two-layered membranous coating called the pleura. The hilus is where the connection between the parietal pleura (covering the rib cage) and the visceral pleura (covering the lung) connect, which denotes the meeting point between the mediastinum and the pleural cavities.
