Week 6 Flashcards
The ___ contains all thoracic structures except pleural cavities.
Mediastinum
The central mediastinum is divided interior superior and inferior parts by a line from the ___ junction to the the T___/___ disc.
Line from manubriosternal junctional anteriorly to the T4/5 IVD
The heart and roots of great vessels are in the middle of the ___ mediastinum.
Inferior
Under the manubrium, from superficial to deep are the great ___ -> the aortic arch associated with the ___ and ___ nerves -> trachea, ___, thoracic duct and left ___ ___ nerve.
Great veins ->
Aortic arch associated with the vagus and phrenic nerves ->
Trachea, oesophagus, thoracic duct and left recurrent laryngeal nerve
The ___ ___ vein drains the head and neck, and the ___ vein drains the upper limb. These arteries join behind the ___ joint to form ___ veins (1 for each side) that join to form the SVC behind the ___ ___ costal cartilage.
Internal jugular vein (1 for each side) Subclavian vein (1 for each side) Sternoclavicular joint Brachiocephalic veins SVC behind the first right costal cartilage
Why is the JVP ideally measured on the right side?
The right brachiocephalic vein has a shorter and more vertical course compared to left (longer and more horizontal course) - pressure column directly from RA
The brachiocephalic veins join to form thje SVC behind the ___ ___ costal cartilage.
The azygous vein comes up the posterior thoracic wall and arches forwards over the lung roots into the back of the SVC behind the ___ ___ costal cartilage.
The SVC enters the right atrum behind the ___ ___ costal cartilage
First right
Second right
Third right
The ascending aorta changes to the arch of the aorta at the ___ ___.
Manubriosternal junction
___ ___ is a fibrous ligament between the bifurcation of the pulmonary trunk and the underside of the arch of the aorta. This was a duct in the embyological circulation to bypass pulmonary circulation if blood did not pass through ___ ___ in the septum. In the embryo, the duct is called ___ ___.
Ligamentum arteriosum
It is a backup if blood did not pass through foramen ovale in the septum
Ductus arteriosus
What are the first 3 branches of the arch of the aorta?
1st - brachiocephalic trunk - divides right common carotid and right subclavian arteries behind the right sternoclavicular joint
2nd - left common carotid artery
3rd - left subclavian artery
In a retroesophageal right subclavian vein variation, the order of branches of aortic arch is right common carotid, left common carotid, left subclavian and THEN right subclavian. To supply the right limb, the right subclavian must pass behind the ___ to get to the right upper limb.
Oesophagus
These patients may present with difficulty swallowing
The ___ nerve is formed by the ___ rami of nerves C3/4/5.
Phrenic nerve
Ventral/anterior rami
What is the course of the phrenic nerves?
Through neck, down on scalenus anterior and between subclavian vein and artery on each side into mediastinum
It is ALWAYS anterior to the lung root structures and ALWAYS the MOST lateral structure in the mediastinum
Right goes through caval orifice at T8
Left pierces diaphragm where apex of heart contacts left dome of diaphragm
The phrenic nerve pierces the ___ and supplies it from its underside.
Diaphragm
The ___ phrenic nerve is lateral to venous structures, and the ___ phrenic nerve is lateral to arterial structures.
Right - lateral to venous
Left - lateral to arterial
The phrenic nerve is a ___ nerve. The phrenic nerve supplies ___ supply to the diaphragm. It supplies sensory supply to the mediastinal and diaphragmatic ___ and ___.
Mixed
Motor
Pleura and pericardium (i.e. all structures it passes)
The ___ nerve is a cranial nerve that moves down the mediastinum - it tries to stay in the midline.
Vagus
What is the course of the vagus nerves?
Down neck with common carotid and IJV -> right tucks against trachea, but aortic arch is in way of left, so left passes lateral to aortic arch, BEHIND the lung roots -> left and right ramify on oesophagus to form oesophageal plexus -> through muscular diaphragm with oesophagus at T10 (left of midline)
The trachea bifurcates at a plane between the ___ junction and T___/___ (i.e. same as division of superior and inferior mediastinum).
Manubriosternal junction
T4/5
Where are the 4 NORMAL sites of narrowing of the oesophagus?
1 at the start of the tube where oesophagus starts as continuation of pharynx (superior narrowing)
1 where it passes through the diaphragm (inferior narrowing)
1 where the aorta arches up/back/left (aortic narrowing of oesophagus)
1 where left main bronchus crosses to LHS from bifurcation of trachea
A lymphatic collection sac called ___ ___ collects ALL lymph from below the ___ (lower limbs, pelvis and abdomen). From here, the thoracic duct starts (at the level of T___, between the crura), at the back of the oesophagus and ascends. After it ascends, it descends and collects lymph from the LHS of the head/neck thorax and the left ___ limb. It then drains into the junction of the left ___ ___ vein and left ___ vein.
Cisterna chyli
All lymph from below the diaphragm
Thoracic duct starts at T12
LHS of head/neck/thorax and left upper limb
Drains into junction of left internal jugular vein and left subclavian vein
What are the 5 structures in the posterior mediastinum (space behind heart and under the plane b/w manubriosternal junction and T4/5 IVD)?
Descending thoracic aorta and its branches - intercostal (posterior), bronchial, pericardial, oesophageal arteries
Oesophagus and oesophageal plexus (from vagus)
Azygous system
Thoracic duct
Sympathetic trunks
Note - trachea is NOT in the posterior mediastinum as it bifurcates AT the plane, does not extend below the plane
___ antimicrobials are used mostly in immunocompromised patients, but in patients with functioning immune system, ___ antimicrobials are often used.
Bactericidal - if immunocompromised
Bacteriostatic - if functioning immune system
Penicillin G is non-___ (except if a patient is allergic). But it is acid ___ so most is destroyed in the stomach. Therefore it is injected.
Non-toxic
Acid labile
Penicillin V is a modified version of penicillin G by the addition of a ___ group. Penicillin V is acid ___ so can be administered orally.
Benzyl
Stable
Glycopeptide drugs like vancomycin are used to treat ___ (abbrev., basically resistant to all beta lactams). They bind to terminal D-Ala-___-___ residues directly. Why does vancomycin not act on G-ve bacteria?
MRSA
D-Ala-D-Ala directly
G-ve bacteria have outer membranes that are impermeable to large macromolecules and highly charged molecules - vancomycin is large and highly charged
Enterococci are Gram ___ cocci. They increasingly show resistance to vancomycin - this is achieved by replacing the D-Ala-D-Ala with D-Ala-D-___.
Positive
Lac
VRSA (S. aureus) are rare because the mechanism for resistance appears to cause increased cell stress so the bacteria die out. But vancomycin intermediate SA (VISA) are more common - what is their mechanism of resistance?
They produce extra cell wall material (i.e. peptidoglycan) to mop up vancomycin
You can’t just increase the dose because vancomycin is assoc. with toxicity
Transpeptidases or ___-binding proteins are the enzymes involved in cross-linking of building blocks of peptidoglycan.
Penicillin-binding proteins
Penicillin is a suicide inhibitor - it mimics D-Ala-D-Ala bond and binds to transpeptidases or ___-binding proteins. It cannot be hydrolysed so the enzyme is inactivated and synthesis of PTG stops. When PTG synthesis stops, bacteria activate cell wall destroying enzymes that break down their own cell walls resulting in cell death. Therefore, penicillin is a ___ antimicrobial.
Penicillin-binding proteins
Bactericidal
