Thoracic cage and intercostal space

Question 1

Bony thoracic cage

Answer 1

12 thoracic vertebrae at back
sternum at front
12 pairs of ribs in between

Question 2

articulation of upper pairs of ribs through costal cartilage

Answer 2

upper 7 pairs articulate anteriorly w/ sternum directly, through costal cartilages

Question 3

articulation of middle pairs of ribs through costal cartilage

Answer 3

costal cartilages of rib pairs 8, 9 and 10 articulate w/ ribs above them

Question 4

lower costal margin

Answer 4

rib pairs 8, 9 and 10 w/ xiphisternum form lower costal margin

Question 5

lowermost point of thoracic cage

Answer 5

10th costal cartilage

Question 6

intercostal space

Answer 6

space between two adjacent ribs. 11 on each side

Question 7

sternal angle and landmark

Answer 7

junction between manubrium and body of sternum. level of lower border of T4 vertebra

Question 8

articulation of 7th costal cartilage

Answer 8

anteriorly articulates at junction between body of sternum and xiphisternum

Question 9

floating ribs

Answer 9

11th and 12th. no connection to bone or cartilage in front

Question 10

surface anatomy

Answer 10

sternal angle is palpable as transverse ridge - used to palpate 2nd costal cartilage and 2nd rib
1st rib under clavicle - not palpable
ribs 11 and 12 are at back, covered by muscles - not palpable

Question 11

intercostal space contents

Answer 11

contains external and internal intercostal, and innermost intercostal muscles arranged in 3 layers
neurovascular bundle: intercostal nerve and vessels. lies between internal and innermost intercostals

Question 12

external intercostal muscle fibres

Answer 12

downwards and forwards. anteriorly, muscle fibres replaced by membrane

Question 13

internal intercostal muscle fibres

Answer 13

upwards and backwards.

Question 14

intercostal nerves and their supply

Answer 14

anterior rami of first 11 thoracic nerves - supply intercostal muscles, skin of chest wall and parietal pleura

Question 15

lower intercostal nerves and their supply

Answer 15

7th downwards. also supply anterior abdominal wall

Question 16

internal thoracic artery - origin and branches

Answer 16

anterior aspect of chest wall. branch of subclavian artery. descends vertically downwards.
in 6th intercostal space it divides into its 2 terminal branches - musculophrenic and superior epigastric arteries (enters anterior abdominal wall through diaphragm).

Question 17

anterior thoracic arteries - origins

Answer 17

branches of internal thoracic arteries or its musculophrenic branch
most posterior intercostal arteries derive from descending aorta