Middle Mediastinum Flashcards
What are the boundaries of the middle mediastinum? Anterior Posterior Lateral Inferior Superior
Anterior – anterior pericardium
Posterior – posterior pericardium
Lateral – mediastinal pleura
Inferior - diaphragm
Superior - transverse thoracic plane
What is the broadest part of the interpleural space?
Middle mediastinum
What 5 structures make up the middle mediastinum?
Heart & pericardium Ascending aorta Pulmonary trunk & arteries Pulmonary veins Nerves
Where does oxygenated and deoxygenated blood flow though the heart?
Deoxygenated blood flows through right atrium and right ventricle
Oxygenated blood flows through left atrium and left ventricle
Complete the diagram of the external aspects of the heart
What are the 4 parts of the aorta and which part of the mediastinum do they travel through?
- Ascending (middle mediastinum)
- Arch (superior mediastinum)
- Descending thoracic (posterior mediastinum)
- Descending abdominal
Complete the diagram
Where does deoxygenated blood leave the heart via?
Pulmonary trunk
What does the pulmonary trunk branch into?
Left and right pulmonary arteries
Complete the diagram
How many pulmonary veins come from each side when entering the heart and what are they called?
Two veins from each side
Inferior and Superior
Complete the diagram
Where does the right atrium recieve deoxygenated blood from?
Superior and inferior vena cava
Complete the diagram of the right atrium
What are the 2 regions of the right atrium?
- Sinus venarum (smooth walled)
- Pectinate muscle
Complete the diagram of the left atrium
Complete the diagram of the right and left ventricles
Complete the diagram of the heart valves
What are the 2 semilunar valves?
- Pulmonary valve
- Aortic valve
What are the 2 atrioventricular valves?
- Tricuspid valve
- Bicuspid (mitral) valve
Label the valve leaflets on the atrioventricular valves
What are the cusps that make up the bicuspid and tricuspid valves?
Left
Bicuspid valve
- Anterior cusp
- Posterior cusp
Right
Tricuspid valve
- Anterior cusp
- Posterior cusp
- Septal cusp
Label the valve leaflets on the bicuspid and tricuspid valves
A - anterior
P - posterior
S - septal
What cusps make up the pulmonary and aortic valves?
Pulmonary valve cusps:
- Left
- Right
- Anterior
Aortic valve cusps:
- Left
- Right
- Posterior
Complete the diagram of the semilunar valve cusps
Which cusps do the left and right coronary arteries arise from?
Right coronary artery from right cusp
Left coronary artery from left cusp
Label the valve cusps and the coronary arteries
R- right
P - posterior
L - left
Right coronary artery from right cusp
Left coronary artery from left cusp
How many layers is the pericardium?
3
What is the pericardium attached to superiorly and inferiorly?
What structures influence the movement of the pericardium?
Attached to the great vessels superiorly and diaphragm inferiorly
Influenced by movement of the great vessels, sternum & diaphragm
Which nerve travels over the pericardium?
Phrenic
What are the functions of the pericardium?
- Protects heart from overfilling (cardiac distension)
- Retains heart in position (pericardio-sternal ligaments)
Complete the diagram of the pericardium
What are the 3 layers of epicardium and what order do they go in?
- Serous pericardium (internal)
a. Parietal layer
b. Visceral layer (or Epicardium) - Fibrous pericardium (external)
What does the pericardial cavity contain and why?
A small amount of serous fluid to allow for uninhibited movement
Complete the diagram of the 2 pericardial sinuses
What is a pericardial sinus?
Where is the transverse sinus and how can it be used in surgery?
Located between outflow vessels of the heart (AA + PT) and inflow vessels (SVC + PV) - can be used in surgery to clamp the outflow of blood from the heart
Where is the oblique sinus?
Located between pulmonary veins
What is the anatomical definition of a sinus?
A sinus is a sac or cavity in any organ or tissue
Where are coronary vessels located?
In the atrioventricular and interventricular grooves
Complete the diagram of the coronary arteries
What does this diagram show?
Functional (potential) anastomoses exist between the branches of anterior interventricular artery and posterior interventricular artery
When can functional anastomoses not maintain substantial collateral circulation?
If a major branch occluded suddenly
Is this diagram left or right dominant?
Left dominant
Is it more common for people to be left-dominant or right-dominant?
Right-dominant
67% individuals - RCA dominant
15% individuals - LCA dominant
Where does the posterior interventricular artery arise from in left-dominant hearts?
Circumflex artery
Name 2 examples of common variation in coronary circulation
- 4% individuals have an accessory coronary artery.
- 40% population - the SA nodal branch comes off the circumflex
Complete the diagram of coronary veins
Where is the sinoatrial node located?
Close to crista terminalis at junction between SVC and right atrium
Where is the atrioventricular node located?
Interatrial septum close to coronary sinus opening
What is the role of the sinoatrial node?
The SA node initiates contraction, impulses spread through atrial wall to AV node via internodal tracts
What is the role of the atrioventricular node?
AV node continues into AV bundle (of His) and divides in the interventricular septum to travel to left and right ventricles to conduct the impulse to the left and right Purkinje fibres.
What is the role of the fibrous skeleton?
- Framework of 4 fibrous rings of dense connective tissue
- Forms an electrical insulator between the atria and ventricles
Where does the fibrous skeleton provide attachement for?
•Provides attachment for Atrioventricular and Semi-lunar valves
Complete the diagram
Which nervous system regulates innervation of the myocardium?
Where do these nerves destined for the heart enter?
Autonomic nervous system
Cardiac plexus
Where does the sympathetic and parasympathetic innervation of the heart originate from and travel to?
Parasympathetic fibres from the Vagus nerve enter the cardiac plexus and then travel to the SA node
Sympathetic fibers from Sympathetic Trunk levels T1-5 enter the cardiac plexus and then travel to the SA node
Complete the diagram
