Theme 1: Lecture 2 - The Superior Mediastinum Flashcards Preview

Module 103: The Heart, Lungs and Blood > Theme 1: Lecture 2 - The Superior Mediastinum > Flashcards

Flashcards in Theme 1: Lecture 2 - The Superior Mediastinum Deck (48)
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1
Q

Where is the mediastinum located?

A

Between the left and right pleural cavities

2
Q

What are the three names for the junction between the manubrium and sternal body?

A
  • Level T4/5
  • Sternal angle
  • Transverse thoracic plane
3
Q

What are the divisions of the mediastinum?

A

Superior and inferior

4
Q

What is the inferior mediastinum further divided into?

A

Anterior, middle and posterior

5
Q

What is the superior boundary of the superior mediastinum?

A

Superior thoracic aperture (manubrium, 1st rib and costal cartilage, T1 vertebra)

6
Q

What is the inferior boundary of the superior mediastinum?

A

Transverse thoracic plane or T4/5 or sternal angle

7
Q

What is the anterior boundary of the superior mediastinum?

A

Manubrium

8
Q

What is the posterior boundary of the superior mediastinum?

A

T1-T4/5 vertebral bodies

9
Q

What are the lateral boundaries of the superior mediastinum?

A

Mediastinal pleura`

10
Q

What is contained in the superior mediastinum?

A
  • Arteries (arch of aorta and branches)
  • Veins (brachiocephalic veins, superior vena cava)
  • Phrenic and Vagus nerves
  • Oesophagus
  • Trachea
  • Thoracic duct
  • Thymus gland (part)
11
Q

Where is the thymus gland located?

A

Immediately deep to the sternum and superficial to the heart. It is in both the superior and anterior mediastinum

12
Q

What is the thymus gland?

A
  • It’s a lymphoid organ
  • T and B cells are produced in the bone marrow, T cells mature in the thymus (once they’ve matured they migrate to lymph nodes throughout the body)
  • Lymph drains through the parasternal, brachiocephalic and tracheobronchial nodes
  • Atrophies after puberty and is replaces by fat
13
Q

Which arteries supply the thymus gland?

A

Internal thoracic arteries (these branch off the subclavian arteries and travel down either side of the sternum on the inside of the thoracic wall)

14
Q

What are the arteries in the superior mediastinum?

A

The arch of the aorta and its 3 branches:

  • Brachiocephalic trunk (this branches into the right common carotid and subclavian arteries)
  • Left common carotid artery
  • Left subclavian artery
15
Q

What arteries branch off the ascending aorta?

A

Left and right coronary arteries

16
Q

What arteries branch off the descending aorta?

A
  • Posterior intercostal arteries (anastomose with anterior intercostal arteries coming from the internal thoracic arteries)
  • Left bronchial arteries
  • Lumbar arteries
17
Q

What veins are contained in the superior mediastinum?

A
  • Superior vena cava

- brachiocephalic veins

18
Q

Which veins form the superior vena cava?

A

The union of the left and right brachiocephalic veins

19
Q

Which veins form the brachiocephalic veins?

A

The union of the internal jugular vein and subclavian vein

20
Q

What is the ligamentum arteriosum?

A
  • A ligamentous structure that connects the pulmonary trunk to the aorta
  • An embryological remnant of the Ductus Arteriosus
21
Q

What is the Ductus Arteriosus?

A
  • An open duct connecting the pulmonary trunk and the arch of aorta
  • Important in foetal circulation allowing blood to bypass the immature lungs
  • Closes at birth
22
Q

Describe the Trachea

A
  • Tube with C-shaped cartilage rings
  • Trachealis muscle runs posteriorly
  • Runs from larynx to bronchi
23
Q

Describe the oesophagus

A
  • Muscular tube

- Runs from pharynx to stomach

24
Q

Describe the thoracic duct

A
  • Transports lymph to the venous system
  • Starts beneath the diaphragm, travels all the way through the thorax between the vertebral bodies and oesophagus before draining into the venous system at the venous angle
  • Receives multiple branches throughout the thorax
  • Numerous branches associated with thoracic (descending) aorta
25
Q

Where do the phrenic nerves originate from?

A

Anterior rami of spinal nerves C3, C4 and C5

26
Q

Where do the phrenic nerves travel?

A
  • Enter mediastinum between brachiocephalic veins an subclavian arteries
  • Pass anterior to the main bronchi
27
Q

What do the phrenic nerves do?

A
  • Provide motor supply to the diaphragm

- Provide sensory supply to the diaphragm (central region) and parietal pleura (diaphragmatic and mediastinal)

28
Q

How many phrenic nerves are there?

A

2

29
Q

Where do the vagus nerve originate from?

A

The brainstem (AKA cranial nerves 10)

30
Q

Where do the vagus nerves travel?

A
  • They enter the mediastinum just medial to the phrenic nerves
  • They continue into the posterior mediastinum coursing posterior to the main bronchi
31
Q

What do the vagus nerve give rise to?

A

The recurrent laryngeal branch to supply the larynx

32
Q

What do the vagus nerves do?

A

Provide parasympathetic supply via the pulmonary, cardiac and oesophageal plexi

33
Q

What does the anterior mediastinum contain?

A
  • Thymus gland in children which atrophies in the adult and is replaced by fatty tissue
  • Pericardial-sternal ligaments
  • Lymph nodes (parasternal) and vessels
  • Internal thoracic artery
34
Q

What is the superior border of the anterior mediastinum?

A

Level T4/5

35
Q

What is the inferior border of the anterior mediastinum?

A

Diaphragm

36
Q

What is the anterior border of the anterior mediastinum?

A

Sternum

37
Q

What is the posterior border of the anterior mediastinum?

A

Pericardial sac

38
Q

How does the heart develop?

A
  • Angiogenic clusters develop in the mesoderm and these canalise (become hollow) to form early blood vessels
  • Two large blood vessels known as heart tubes form in the cardiogenic area
  • The paired heart tubes grow and fuse
39
Q

What day do the paired heart tubes grow and fuse?

A

21 (this is also when the heart starts to beat, this is important as the embryo can no longer satisfy its needs by diffusion alone)

40
Q

What are the regions that the newly formed heart tube are divided into?

A
  • Sinus venosus
  • Primordial atrium
  • Primordial ventricle
  • Truncus arteriosus
41
Q

What is the sinus venosus?

A

The primitive inflow vessels into the heart tube of an embryo

42
Q

What is the truncus arteriosus?

A

The primitive inflow vessels into the heart tube of the embryo

43
Q

On which day does the heart tube become too long for the pericardial cavity and start to fold?

A

Day 23

44
Q

What does folding of the heart result in for the heart’s orientation?

A
  • Ventricles and outflow tracks positioned anteriorly

- atria and veins posteriorly

45
Q

What are the two features of the foetal heart that allow blood to bypass the lungs?

A
  • Foramen ovale

- Ductus arteriosus

46
Q

What is the foramen ovale?

A

Opening between the left and right atria in the foetus and allows oxygenated blood to bypass the lungs

47
Q

What is the fossa ovalis?

A

The embryological remnants of the foramen ovale which closes after birth

48
Q

Why can blood travel from the right to left atrium through the foramen ovale?

A

Due to the higher pressure in the right than the left atrium

Decks in Module 103: The Heart, Lungs and Blood Class (51):