L8 Diaphragm and Nerves of Thorax

Question 1

Diaphragm

Answer 1

Muscular base of thorax
Left and Right Crux = crua
=own nerve supply
Left dome (lower due to heart) Right dome (higher due to liver)
Allows for pressure and volume change
-Contracts= descends inferiorly = increased volume, decreased pressure, inhale
= less space in abdomen, higher pressure, aids venous return with IVC

Question 2

Diaphragm Ligaments

Answer 2

Posterior attachment of the diaphragm
Centre: MediAN Arcuate Ligament/Aortic Hiatus
Middle: MediAL arcuate ligaments
Outer: LATERAL arcuate ligaments

Question 3

Structures passing through diaphragm

Answer 3

IVC= T8
Oesophagus= T10
Aorta= T12

Question 4

Diaphragm nerve supply

Answer 4

Phrenic Nerve

• somatic nerve from neck
• runs anteriorly re hilum

Question 5

Crus

Answer 5

Right Crus Extend further + comes across onto Left side

Left Crus contained on Left side

Question 6

Central Tendon

Answer 6

Tendonous region in the centre where 2x pleura meet

1) IVC T8 comes through
- tendon doesnt have alot of contractility, doesnt move, therefore IVC wont get compressed/blood continues to flow, as diaphragm contracts and descends
2) Right Phrenic nerve (Same opening as IVC)
- spreads out in radial fashion, supply Right side of diapraghm

Question 7

Phrenic Nerve

Answer 7

C3-5 (cervical). somatic nerve, can control diaphragm moving (hold breath). Anterior to Hila of Lung

• some fibres off to pericardium
• supplies diaphragm from under surface
  1) Right Phrenic nerve come through same opening in central tendon as IVC
• spreads out in radial fashion
• supplies right side of diaphragm
  2) Left Phrenic nerves enters via Left crus. pierces and spreads out across undersurfaces

Question 8

Oesophagus

Answer 8

T10
comes through Right Crus of diaphragm, forming Sling around
-Sphincter for oesophagus (no true anatomical sphincter)
-closes the muscular tube for the majority of the time so stomach contents arent regurgitated back up
+ vagus nerve
-surround oesophagus in plexus (hard to tease off), then continues to abdomen

Question 9

Vagus nerves

Answer 9

T10, with the Oesophagus, comes through Right Crus of diaphragm

• Parasymp supply to thorax and abdomen
• Cranial nerves, neck + thorax
• surround oesophagus in plexus (hard to tease off), then continues to abdomen
• Anterior and Posterior Vagal Trunks come from Left and Right vagus nerves

Question 10

Aorta

Answer 10

T12
Midline, behind MediAN arcuate ligament
-can be compresses as doesnt come through muscular part of diaphragm = blood can flow freely

Question 11

Thoracic Duct

Answer 11

Carrier majority of Lymphatic fluid back into venous system

• drains all lower limbs of abdomen
• cysterna kily continuation

Question 12

Lower Limb muscle under MediAL arcuate ligament

Answer 12

Psoas major

-posterior abdominal wall

Question 13

Lower limb muscle under the Lateral arcuate ligament

Answer 13

Quadratus Lumborum

Question 14

Overriding Autonomic control re Breathing

Answer 14

Phrenic somatic control

• can consciously stop diaphragm from moving and hold your breath
• autonomic control return of breathing once pass out after holding breath long enough

Question 15

Phrenic nerve Dermatome

Answer 15

C3-5 = chest + shoulder
Irritation of phrenic nerve = shoulder pain
-Intraabdominal nerve pain
1) inflamed gallbladder
2) pancreatitis
-irritation in intra-abdominal space = pain signal via Shoulder Tip pain

Question 16

Classes of Nerves

Answer 16

1. Somatic (Peripheral nerves)
   (Intercostal nerves, Phrenic nerve)
   -e.g. brachial plexus
   -pain, motor, sensory
   -controllable
2. Autonomic (visceral)
   -make a plexus altogether
   -regulates visceral functions
   a) PARAsymp (Vagus)
   -1. Brainstem cranial nerves III, VII, IX, X
   -Vagus/wandering nerves
   -2. Sacral spinal nerves (S2-S4) (from cauda equina). pelvic control.
   b) Sympathetic (sympathetic chain) (T1-L2 spinal nerves)
   - T1-T5 (supply to Cardiac + Pulmonary plexuses)
   - T6-L2 (supply to splanchnic nerves)

Question 17

What are the 4x nerves of the thorax?

Answer 17

1. Intercostal Nerve (somatic)
2. Phrenic nerve (somatic)
3. Vagus (Para)
4. Sympathetic chain (Symp)

Question 18

Sympathetic chain

Answer 18

Only sympathetic supply (head - pelvis)
Lateral to vertebral column
Symp. branches come from each spinal level, and form chains w. ganglia at each level
-any interruption to these nerve in thorax can give signs that are much further afeild (face = tumour in thorax)

Question 19

Autonomic Sympathetic nerves

Answer 19

Fight or Flight

• relaxes bronchioles
• increased HR heart rate
• increased CO

Question 20

Parasympathetic nerves

Answer 20

• bronchiole constriction (less air in)
• decreased HR heart rate
• decreased CO

Question 21

Sternal wires

Answer 21

on chest x-ray
chest has previously been opened up (e.g. for cardiac bypass)
-major

Question 22

Lopsided diaphragm

Answer 22

markedly different
damaged phrenic nerve
Nerve= contraction = descent/downwards diaphragm
Nerve damage= diaphraghm doesnt move/doesnt descent remains high

Question 23

Horner’s Syndrome

Answer 23

relatively common
weird face
-all on same side
1. PTosis- eyelid droops/ lost control/eye half closed
2. Meiosis - pupil constricts (not reactive to light) (pin point pupil)
3. Anhydrosis - lack of sweating dry half face) (hydro=water)
All controlled by sympathetic chain from chest. Hints tumour/lesion in chest compressing sympathetic chain info flow into head and neck