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Flashcards in Middle mediastinum Deck (29):
1

Anterior boundary of the middle mediastinum

Anterior pericardium

2

Posterior boundary of the middle mediastinum

Posterior pericardium

3

Lateral boundary of the middle mediastinum

Mediastinal pleura

4

Inferior boundary of the middle mediastinum

Diaphragm

5

Contents of the middle mediastinum

Heart and pericardium
Ascending aorta
Pulmonary trunk and arteries
Pulmonary veins
Nerves
Lymph nodes

6

Heart chambers

2 receiving atria
2 discharging ventricles

7

3 layers of each heart chamber

Endocardium
Myocardium
Epicardium

8

Fibrous skeleton

Framework of 4 fibrous rings of dense connective tissue

Provides attachment for AV and semi lunar valves

Dorms and electrical insulator between the atria and ventricles

9

Pericardium

3 layered sac which heart is suspended in by the great vessels

Protects heart from overfilling

Influenced by movement of the great vessels, sternum and diaphragm

10

Layers of the pericardium

Fibrous pericardium (external)

Serous pericardium (internal)
- parietal layer
- visceral layer (or epicardium)

11

Transverse sinus

Space between outflow and inflow vessels

12

Coronary circulation

Coronary arteries and veins in atrioventricular groove and interventricular groove

Two main coronary arteries arise from ascending aorta

13

RCA

Gives rise to branches
- sinu-atrial nodal
- right marginal
- posterior interventricular

14

LCA

Gives rise to
- anterior interventricular
- diagonal
- circumflex
- left marginal

15

Anastomoses

Exist between small coronary branches of RCA and LCA

Don't maintain substantial collateral circulation of major branch occluded suddenly

16

Coronary artery dominance

Coronary artery which gives risk to the posterior IV artery

RCA dominant in 67% individuals

LCA dominant in 15 % individuals (posterior IV branches from circumflex)

17

Coronary artery variation

4% individuals have an accessory CA

40% population the SA nodal branch comes off the circumflex

18

Venous drainage of the heart

Coronary sinus drains into right atrium via its own opening

Receives 4 major cardiac veins:
- great
- middle
- small
-posterior

19

Coronary sinus

Largest coronary vein

20

Conduction of nerve impulses

1. Impulse commences at SA node
2. Excitation signals cause atrial muscle to contract
3. Impulses spread through atrial wall to AV node via internodal tracts
4. AV node located in interatrial septum close to coronary sinus opening
5. AV node continues directly into AV bundle of His penetrating the fibrous skeleton
6. AV bundle divides in muscular interventricular septum and continues into the walls of the ventricles to the purkinje fibres

21

SA node

Collection of specialised cells at junction of SVC and right atrium

22

Regulation of conducting system

Innervation of the myocardium regulated by ANS

Nerves from ANS destined for the heart enter the cardiac plexus

23

Preganglionic parasympathetic fibres

Vagus nerve

Enter and synapse in ganglia of cardiac plexus

24

Postganglionic parasympathetic fibres

Exit plexus for SA node

25

Postganglionic sympathetic fibres

T1-5 paravertebral ganglia Enter and exit the cardiac plexus for the SA node

26

Aorta

Ascending (middle mediastinum)
Arch (superior mediastinum)
Descending thoracic (posterior mediastinum)
Descending abdominal

27

Pulmonary trunk

Deoxygenated blood leaves heart via pulmonary trunk

Branches into left and right pulmonary arteries

Enter hilum/ root of the lung

28

Pulmonary veins

Oxygenated blood from lungs to left atrium

Two veins from each side inferior and superior

29

Vena cava

Blood enters the heart via right atrium

Receives deoxygenated blood from superior and inferior vena cava