Anatomy: Thorax Flashcards
Abdominal breathing mechanism
Muscle fibres of diaphragm contract
Causes central tendon to move downwards (increases vertical diameter) - then movement arrested by the liver
This now acts as a fixed point - ebcomes the origing for muscle fibres to insert
Causing the elevation of the lower 6 ribs
Order of lung root structures (anterior to posterior)
Upper of the two pulmonary veins
pulmonary artery
bronchus
Where does the phrenic nerve travel in the middle mediastinum?
In between the fibrous pericardium and the mediastinal pleura
Three surfaces of the heart
Anterior - RA, RV, narrow strip of LV, auricle of LA
Posterior (base) - LV, LA + 4 pulmonary veins
Inferior (diaphragmatic) - LV + RV + inferior part of RA where IVC enters
Heart basics
Direction of apex and base
Free floting in pericardium - only attached to great vessels at base
Apex - downwards, forwards, left
Base - upwards, backwards, right
How to avoid pulmonary vasculature in development
Ductus arteriosus: RA - RV - PA - DA - aortic arch; becomes ligamentum arteriosus
Foramen ovale: RA - LA - LV - aortic arch; becomes fossa ovalis
Where is pleural pain referred to?
Parietal - eg. right lower lobe pneumonia via intercostal nerves to right lower abdomen mimicking appendicitis - goes to the corresponding thoraco-abdominal wall
Diaphragmatic pleura - via phrenic nerve to tip of the shoudler - C4 dermatome
Relations of the manubrium
Anterior boundary of superior mediastinum
Upper part = L brachiocephalic vein + artery; L common carotid artery; L subclavian
Lower part = aortic arch
Laterally = lungs and pleura
Nerve supply of pleura
Visceral - autonomic from vagus that supplies lung, sensitive only to stretching (no pain)
Parietal - somatic innervation from intercostal nerves (sensitive to pain)
Diaphragmatic pleura - phrenic nerve (sensitive to pain)
Composition of Trachea
Fibroelastic tissue
U shaped rings; open posteriorly; ends connected by trachealis muscle
Rings can get calcified on xray
What is the crista terminalis?
Muscular ridge separating the smooth walled posterior part of the RIGHT atrium (which is derived from the sinus venosus) from the rougher part derived from the true atrium (due to pectinate muscles)
Branches of the right coronary artery
Marginal branch along the lower border of the heart
Posterior interventricular branch - runs forward into the inferior interventricular groove - then anastamoses with the corresponding branch of the left coronary artery (also known as the posterior descending artery)
Location of AV node
Interatrial septum - above opening of coronary sinus
L bronchopulmonary segments
Upper lobe - apico-posterior (1,2), anterior (3), superior lingular (4), inferior lingular (5)
Lower lobe - superior (6), anteromedial basal (8), lateral basal (9), posterior basal (10)
How many pulmonary veins open into the LA?
4
Superior and inferior from each lung
4th costal cartilage significance in the pericardium relations
below 4th CC - pericardium in contact with the sternum
above 4th CC - lungs and pleura are in front
Venous drainage
Venae cordis minimae - tiny veins draining into the chambers
Anterior cardiac veins - small, open directly into the RA
Coronary sinus - main drainage, opens into the RA - below the AV node and left of the IVC opening, lies in the posterior AV groove; tributaries include - great cardiac vein, middle cardiac vein, small cardiac veins
Articulations of the Body of the Sternum
Number of parts of the body of the sternum
Most of the second costal cartilage
Third - Seventh costal cartilage
4 parts = stenebrae
Attachments and shape of the central tendon of the diaphragm
Shape - trefoil
Attachments - insertion of muscular fibres; above it fuses with the pericardium
Tributaries and routes of the coronary sinus
Great cardiac vein - anterior interventricular groove - follows the LAD
Middle cardiac vein - next to the posterior interventricular artery (drains the posterior and inferior surfaces of the heart)
Small cardiac vein - follows marginal artery, drains into the terminus of the coronary sinus
Distortion + widening of the carina
Lobar collapse
Pathology of the heart (LA enlargement)
enlargement of the tracheo-bronchial lymph nodes at the bifurcation due to carcinoma
Most common congenital abnormality of the heart
VSD
Small ones = ok
Large ones (esp in membranous septum below AV valves) = may require repair
Use of sternal puncture
Access bone marrow for the body of the sternum
Need to know the posterior relations of the sternum (brachiocephalic artery and vein / subclavian / common carotid / aortic arch)
Features of 11/12 rib
Short
No tubercles
One articular facet on head
11th shallow subcostal goove, 12th no subcostal groove
Tracheostomy
Incision style
Vertical (from cricoid cartilage passing between the anterior jugular veins)
or
transverse (cosmetic - halfway between cricoid cartilage and suprasternal notch)
Development of the diaphragm
4 parts
- Septum transversum (fibrous central tendon); (bare area of liver attaches here)
- mesentery of the foregut (area adjacent to the vetebral column becomes the crura + median part)
- Ingrowth from body wall
- Pleuroperitoneal membrane (R+L) - these close of the communications between the pleural and peritoneal cavities
Rib Fractures complications
Damage lung (contusion) or pneumothorax
Rupture spleen (L 9,10,11)
Rupture intercostal vessels = haemothorax
First Rib important structures
inner upper border - scalene tubercle where scalene anterior attaches
anterior to scalene tubercle - subclavian vein
posterior to scale tubercle (in the subclavian groove) - subclaviant artery and lowest trunk of brachial plexus below that
neck of first rib crossed by - M to L - sympathetic trunk, supreme intercostal vein, superior intercostal artery, t1 to brachial plexus
first digitation of serratus anterior attaches to outside edge
suprapleural membrane (sibson’s fascia) attached to inner border
Four borders of the heart
Right - RA + SVC + IVC
Left - LV + auricle of LA
Inferior - RV + apex of LV
Superior - RA + LA + great vessels
Use of no pleura at 4th 5th ICS
Needle goes staight into pericardium, useful for pericardiocentesis
What happen at angle of louis / sternal angle?
T4 plane
Sterno-manubrium
Bifurcation of trachea
Start and finish of aortic arch
Ligamentum arteriosum
Border of superior and inferior mediastinum
Azygos vein joins into the SVC
Thoracic duct runs from right to left
Rib
true
false
12 pairs
1-7 true - articulate with the sternum through costal cartilages
8-10 false articulate with costal cartilage, each with rib above
11-12 - no articulation, free anteriorly = floating
Muscles and directions of the intercostal muscles
External Intercostal muscles - downwards and forwards, replaced in the front by the anterior intercostal membrane
Internal intercostal muscles - downwards and backwards, replaced in the back by the posterior intercostal membrane
Innermost intercostal muscles - covers more than one intercostal space
Order of contraction for the AV bundle
Papillary muscle, then wall and septum from apex towards outflow tract
Damage to phrenic nerve complicaitons + clinical finidngs
Paralysis of diaphragm
Diaphragm elevated - dullness to percussion at base of lung + absent breath sounds
+ paradoxical movement on respiration
Route of the left coronary artery
Left posterior aortic sinus
Passses below then to the left of the pulmonary trunk
follows the left AV groove into the cover of the left auricle
then divides into two branches
Nerve supply of the heart
Sympathetic - cardio accelerator
Vagus - cardio inhibitor
L lung gross anatomy
Oblique fissue / 2 lobes - upper and lower
Cardiac notch on the anterior border
Middle lobe equivalent = lingula - lies between the cardiac notch and the oblique fissure
Structures seen when view the mediastinum from the right
Oesophagus
Trachea
Veins - SVC
Nerves - vagus, phrenic, sympathetic chain
What is the mediastinum?
What are the sections?
Space between the two pleural cavities
Superior
Middle
Anterior
Posterior
Purpose of Ductus venosus
Bypasses the liver
Cusps of tricuspid valve
Septal, anterior, posterior
Differences between R and L main bronchus
Size
Length
Route
Branches
R is wider, shorter and more vertical
R is 2.5cm; L is 5cm
Both pass downwards and laterally: R behind ascending aorta and SVC; L below aortic arch and in front of oesophagus and descending aorta
R gives of upper lobe branch before entering hilum; left does not give off any branches
R lung gross anatomy
Larger than L
3 lobes - upper (horizontal) middle (oblique) lower
Inspiration muscles used
Quiet
Forced
Abdominal + thoracic muscle combination
SCM, scalenes, serratus anterior, pec major, pec minor
Great vessels
6 pairs of arches
1 + 2 disappears
3 carotid
4 subclavian R; aortic arch L (giving L subclavian)
5 disappears
6 R+L pulmonary arteries connecting to dorsal aorta - R disappears; L connects to aortic arch via ductus arteriosus
Nerves related to the diaphragm
Phrenic nerve (C3,4,5) - main motor innervation of the diaphragm
Greater and lesser splanchnic nerves pierce through the crura
Route of the L pulmonary artery - where it divides in front of the left main bronchus
Connected at its origin to the aortic arch via the ligamentum arteriosum
Runs in front of the left main bronchus and descending aorta
Left recurrent laryngeal nerve loops below the ortic arch in contact with the ligamentum arteriosum
Cardiac referred pain
Cardiac sensation - T1-4; referred pain of these dermatomes - arm (route: cardiac plexus - sympathetic chain - DRG - spinothalamic tract)
for jaw: vagal - nucleus of tractus solitarius in the medulla - upper cervical spinothalamic
How to work out the horizontal fissure?
Horizontally and medially from the 4th CC of the oblique fissure
R main bronchus
Downwards and laterally
Behind ascending aorta and SVC; azygous vein arches over it from behind to enter SVC
Gives off upper lobe bronchi before entering hilum
Divides into bronchi for middle and lower lobes within lung
Pulmonary artery lies below then anterior to it
Cusps of mitral valve:
Cusps of aortic valve:
anterior / posterior
right posterior (NCC) / anterior (RCC) / left posterior (LCC)
Relations of the body of the sternum
R - right pleura, thin anterior border of the right lung (intervenes between it and the pericardium)
L - upper two parts - left pleura, left lung
L - lower two parts - pericardium
Dextrocardia vs Situs inversus
Just heart vs all viscera
What’s special about 10th rib?
Only one articular facet on head, rather than 2
Structures seen when viewing the mediastinum from the left
Heart
Arteries - left subclavian, left common carotid descending aorta
Nerves - phrenic, vagus, left recurrent laryngeal
Cervical Rib Complications
Artery: Post-stenotic dilation of subclavian artery - turbulene, thrombi, distal emboli, ischaemia, Raynaud’s, subclavian aneurysm
Vein: thrombosis
Nerve: Brachial plexus - C8/T1 - wasting of small muscles of the hand; sensory loss in C8/T1 distribution