thorax Flashcards
how many pairs of ribs do we have
12
what types of ribs do we have
7 pairs of true ribs (1-7)
3 pairs of false ribs (8-10)
2 pairs of floating ribs (11 + 12)
what do true ribs connect to
sternum via their own costal cartilage
how do false ribs attach to the sternum
by merging together and attaching to the costal cartilage of rib 7 (forms the costal margin)
so indirect connection with the costal cartilage
how do floating ribs connect to the sternum
DO NOT as they do not have costal cartilage
what do all ribs attach to
thoracic vertebrae of spine (in thoracic region of the spine) posteriorly
so what is the ribcage formed by
rib bone becoming costal cartilage (costal bc in region of the lungs) which then attaches to sternum itself
what is located between the rib and where it becomes costal cartilage
costo-chondral junction
what level does the
a) 1st rib
b) 2nd rib
attach
a) T1 vertebra = to manubrium portion of sternum
b) T12 vertebra
what is the space between each of the ribs called
intercostal space
what 3 parts make up the sternum from top to bottom
1) manubrium
2) body of the sternum
3) xiphoid process
what bone attaches to the scapular on the posterior aspect of the ribcage
clavicle
which 2 openings allow structures to enter and leave the rib cage
1) superior thoracic aperture = structures pass from h&n or upper limb into thoracic region
2) inferior thoracic aperture = pass from thoracic region to abdominal region
what 3 functions does the ribcage serve, explain these
1) protection = for vital organs (heart, lungs) + upper abdominal organs (liver sits high up on rhs and pushes up into the diaphragm) + spleen on lhs
2) support = all bones have muscles attached to them, ribcage provides stable point of attachment for lots of muscles in thoracic region + muscles that help control movement of upper limb (eg pecks, a few muscles in top of arms / shoulders)
3) respiratory movements = breathing in + out changes thoracic vol (essential for pressure change and air to be drawn in / forced out)
what is the diaphragm
high spongy sheet of thin, strong muscle that separates thorax from the abdominal region and covers the entire inferior thoracic outlet
how does the diaphragm sit
domes superiorly into rib cage when relaxed
higher on rhs bc of liver
what does the diaphragm do during
a) inspiration
b) expiration
a) contracts so muscle fibres pulled tight causing muscle to be pulled down flat (more space inside rib cage for lungs to expand and take in as much O2 as possible)
b) relaxes
what allows passage of structures through the between thorax and abdomen
apertures in its posterior
what level does the inferior vena cava pass through the diaphragm at
T8 (thoracic vertebra 8)
- remember - vena cava has 8 letters so T8!
what level does the inferior oesophagus pass through the diaphragm at
T10
- and oesophagus has 10 letters
what level does the inferior / descending aorta pass through the diaphragm at
T12
which nerves supply the diaphragm and what are they made up of
PHRENIC NERVES (r+l one)
made up of contributions from cervical spinal nerves 3, 4, 5
C3, C4, C5 keeps the diaphragm alive!
what are the 3 layers of intercostal muscle
external (also have an external intercostal membrane - lies medial to external muscle, v thin and see through)
internal (fibre directions lay perpendicular to external)
innermost
explain the innermost intercostal muscles
- v thin layer of muscle, follows same fibre direction as internal
- only used when forcing air out of lungs - accessory muscle of respiration
how do external intercostal muscles run and what does this mean when we breathe in
downward direction
from upper rib and latch onto rib below
external contract pulling inferior rib upwards
how do internal intercostal muscles run and what does this mean when we breathe out
upward direction
from lower rib and latch onto rib above
internal contract pulling ribs down to dec space in thoracic cavity so we’re forcing air out through lungs
which three vessels correspond to the intercostal spaces
what is there role
where are these found
intercostal vein (posterior intercostal veins drain into azygous vein - hemiazygous and accessory azygous veins)
intercostal artery (posterior intercostal artery arise from descending aorta)
intercostal nerve (sympathetic contributions from sympathetic chain)
supply intercostal muscle / take blood away
found under the costal groove (on lower portion of inner surface of each of rib) + protects the structures
what is the structure of the intercostal space
1) external intercostal muscle most superficial
2) then internal
3) then the neurovascular bundle (ALWAYS runs vein, artery, nerve top to bottom VAN)
4) deep to this is innermost
how do intercostal muscles help to move the position of the ribcage
- ribcage moved up + out of sternum when external intercostal in upper ribs pull to move ribs up in inspiration which increases anteroposterior diameter making more room for lungs to expand
- when external intercostal contract, lower ribs move up + out increasing diameter across entire ribcage (transverse diameter) in inspiration
what are the 2 divisions of the thoracic cavity
superior mediastinum inferior mediastinum (made up of anterior, middle + posterior portions)
mediastinum encloses / contains heart, major vessels + nerves, trachea (carrying air to lungs) + oesophagus
what happens to the trachea once in the thoracic region
divides into 2 primary bronchi
what is present either side of the mediastinum
pleural cavities consisting of 2 pleural sacs which cover the lungs
what is the name of the point where the manubrium meets the sternum and what does it allow us to do
STERNAL ANGLE
- know what separates superior mediastinum (run above it) from the inferior (below it)
- 2nd rib attaches at level of it
what level would the sternal angle cut through
T4/5 vertebral disc
so superior mediastinum above level of T4/5 and inferior below
what structures are contained in the superior mediastinum
thymus trachea oesophagus vagus nerves phrenic nerves left recurrent laryngeal branch of the vagus nerve thoracic duct great vessels (aorta, superior vena cava, pulmonary trunk - artery + vein)