thoracic wall

Question 1

how many layers of muscles are present in the intercostal muscles, and how are they organised

Answer 1

3, like plywood

Question 2

what are the 3 layers of the intercostal muscles (superficial to deep) and direction

Answer 2

external intercostals (infromedially), internal intercostals (supromedially), innermost intercostals (supromedially)

Question 3

external intercostals movement

Answer 3

downward and laterally from lower border of rib above to rib below

Question 4

what are external intercostals replaced by when they move, and where does this happen

Answer 4

anterior intercostal membrane at costo-chondral (rib-cartilage) junction

Question 5

where do internal intercostals attachments begin

Answer 5

anteriorly at sternum

Question 6

internal intercostals movement

Answer 6

from lower border of rib above to rib below

Question 7

how are the fibres directed in internal intercostals

Answer 7

at right angles to external intercostals (hence plywood organisation)

Question 8

what are internal intercostals replaced by

Answer 8

membrane posteriorly

Question 9

what passes close together through internal intercostal near bottom of each rib (superior to inferior)

Answer 9

neurovascular bundle of intercostal vein (run posteriorly and anteriorly), intercostal artery (run posteriorly and anteriorly), intercostal nerve (runs from posterior to anterior)

Question 10

how many pairs of intercostal nerves are there and what are they

Answer 10

11; T1-T11 (+ 1 subcostal T12)

Question 11

what type of nerve are the intercostal nerves

Answer 11

mixed, so motor (efferent at front of roots) and sensory (afferent at back of roots); anterior ramus supplies front, posterior ramus supplies errector spinal muscles and skin

Question 12

where do the intercostal nerves originate from and what do they supply

Answer 12

originate from spinal cord (posterior) and pass through intercostal spaces as they travel towards the anterior, where they innovate muscle and skin

Question 13

what axis does the lateral cutaneous branch innovate

Answer 13

anterior and posterior

Question 14

what axis does the anterior cutaneous branch innovate

Answer 14

medial and lateral

Question 15

border area for inserting a chest drain safely to avoid intercostal vessels and nerve, and avoid important structures

Answer 15

anterior border of latissimus dorsi, lateral border of pectoralis major muscle, line superior to horizontal level of nipple, apex below axilla (armpit); 5th intercostal space anterior to mid axillary line

Question 16

what does each intercostal artery join (anastomose) with

Answer 16

major artery at each end of the intercostal space

Question 17

what are the major internal thoracic arteries

Answer 17

subclavian, which then branch to form internal thoracic, anterior intercostal, maculophrenic, superior epigastric, inferior epigastric and external iliac arteries and veins on anterior chest wall