Gross Anatomy of Lungs Flashcards
Thorax definition
superior component of the trunk, connecting the neck with the abdomen
an irregular cylinder with an opening at each end
what are the openings of the thorax called + what communicates?
superior thoracic aperture- thoracic inlet formed by the first thoracic vertebra, the first pair of ribs and the superior surface of the manubrium of the sternum- neck and upper limb
inferior thoracic aperture- thoracic outlet- twelfth thoracic vertebra, eleventh and twelfth pair of ribs and the inferior costal cartilages
what separates the thorax and the abdomen?
muscular sheet of diaphragm
thoracic wall definition
the boundary of the thoracic cavity
what forms the thoracic wall?
bony skeletal part- rib cage- thoracic cage comprised of the sternum, thoracic vertebrae, ribs and costal cartilages
the rest- intercostal muscle, skin and fasciae
function or thoracic wall
protection of thoracic viscera
dynamic generator of change in intrathoracic pressure to drive ventilation
What two things must the thoracic wall be + how is this achieved?
rigid- bony components
mobile- various parts of articulation between the bones
How does the upper limb articulate with the thorax?
clavicle and scapula, which form the pectoral girdle, are closely associated with the thoracic wall
Three parts of the sternum + any important regions
manubrium, body of sternum and cartilaginous xiphoid process- level T9/10
suprasternal notch- jugular notch- level of T2
sternal angle- manubriosternal joint at level of lower T4 vertebrae- secondary cartilaginous joint- palpable landmark
sternal plane at T4/T5- level of bifurcation at carina
Origin of sternum
developmentally forms from a series of smaller bones called sternebrae, fusion of which creates the body of the sternum
more superior sternebrae form the manubrium
costal cartilage definition
bars of hyaline cartilage that serve to prolong the rib forward and contribute to the elasticity of the walls of the thorax
where is costal cartilage found?
only found at the anterior ends of the ribs, providing medial extension
Where do the first two pairs of costal cartilages articulate?
manubrium of the sternum
joint between the manubrium and the body of sternum
how many pairs of ribs?
12
What may also be the case with the number of ribs + significance?
extra or absent ribs in some individuals
clinically significant if there is a pair of cervical ribs at the superior thoracic aperture, which may compress neurovascular structures transversing the narrow space
joint name between sternum and costal cartilage
sternocostal joints
what are the posterior joints called?
costovertebral joints with the ribs articulating with the twelve thoracic vertebrae
Which rib articulates with which vertebrae?
head of rib articulates with the vertebral body at the same level and that of the vertebra above
first, eleventh and twelfth ribs articulate only with respective thoracic vertebra T1, T11 and T12
rib structure
anterior portion contain a piece of costal cartilage
curved body
angle
neck
tubercle- a small bump on the neck articulates with the vertebral transverse process at the same level
head with two articular facets
first rib is particularly flattened
What are the different ribs referred to as?
true ribs- upper seven, articulate directly via their costal cartilages with the sternum
false ribs- rib pair 8 -10 articulate with the costal cartilage of the ribs above
floating ribs- 11-12 have no anterior articulation
Diaphragm definition
domed musculotendinous sheet, being fibrous in its central part called the central tandon
diaphragm structure
both the left and right dome are associated with the lobe above it
muscular part is attached to the xiphoid process and the 11th and 12th rib, lower costal cartilages and the first to third lumbar vertebrae
veretbral attachments are via muscular slopes called crura
right crus originates from L1-L3 and left from L1-L2 vertebral bodies
costophrenic angle- peripheral edge of diaphragm with the thoracic wall
What happens to the costophrenic angle upon inspriration?
diaphragm flattens angle decreases
Where does innervation of the diaphragm originate?
sensory and motor innervation from right and left phrenic nerves originating from C3, C4 and C5
C3,4,5 keep the diaphragm alive
structures that transverse the diaphragm
inferior vena cava at T8- through opening on the right of central tendon
oesophagus and vagus nerves passes through fibres of the left crus at T10
Aorta and thoracic duct of the lymphatic system- pass between crura at the T1 level
Where do the sympathetic chains pass?
along the posterior thoracic wall and pass behind the diaphragm at a level similar to the aorta
Where do the phrenic nerves pass?
descend through the thorax on either side of the mediastinum to reach the diaphragm where they penetrate its substance to innervate it.
Other innervation of diaphragm
peripheral edge of diaphragm receives some sensory innervation from intercostal nerves
What is referred pain?
Pain perceived at a location other than the site of the painful stimulus.
It is a result of a network of interconnecting sensory nerves that supplies many different tissues
Where may the diaphragm pain be referred to?
right shoulder region or right hypochondrium, due to the distal origin of these diaphragmatic nerves C3,4,5
condition affecting the lung + cause
hemidiaphragmatic palsy
paralysis during neck surgery may damage C3,4,5 which prevents motor innervation, so one half of the diaphragm doesn’t move during inspiration
how many layers of intercostal muscle + names?
external and internal intercostal muscles- most developed and fill the spaces between the adjacent ribs
innermost intercostal muscles
Which are the most well developed muscles?
external and internal intercostal
what are the 3 layers continuous with ?
counterparts to the three layers that make up the anterolateral walls of the abdomen
what may the innermost intercostal muscles form?
some anatomically recognised muscle groups such as transversus thoracic and subcostales
Explain the fibres of the external intercostal muscles
rub forwards and downwards rom the tubercles of the ribs
become membranous close to the sternum
explain fibres of the internal intercostal muscles
thickest closest to the sternum
fibres run at right angles to those of the external intercostals and become membranous at the angles of the ribs
what achieves changes in thoracic volume?
diaphragm and intercostal muscles, latter driving the movement of the ribs
What drives ventilation at rest?
contraction and relaxation of the diaphragm
accessory muscles of breathing
sternocleidomastoid, scalenes and quadratus lumborum
What happens during inspiration?
- external intercostal muscles contract, pulling ribs outwards and upwards, which increases the transverse and anteroposterior diameters of the thorax
- diaphragm contracts, increasing the vertical dimension of the thoracic cage
How do the ribs differ + what this causes during inspiration?
different shape and dimension of different ribs results in a slightly different range of movements for each rib
sternal ends of the ribs are lower than their vertebral ends and elevation of the ribs at their costovertebral joints results in a lifting of the sternum upwards and outwards in a ‘pump handle’ movement
the most lateral part of the rib is inferior to its vertebral attachment, resulting in the rib also being moved outwards as it is elevated in a ‘bucket handle’ movement
Where is the pump handle movement most pronounced? + what it causes
second to sixth ribs
increases anteroposterior diameter of thorax
where is the bucket handle movement most pronounced? + what it causes
lower ribs
increases the transverse diameter of the thoracic cage
When are accessory muscles utilised?
during deep or forced inspiration
explain actions of accessory muscles
- neck muscles, sternocleidomastoid and the scalenes pull upon the first rib, lifting the sternum- further increasing the anteroposterior and vertical dimension
quadratus lumborum aids the contraction of the diaphragm by pulling upon the twelfth rib
explain expiration
predominantly passive process, driven by the relaxation of the diaphragm and external intercostal muscles and recoil of the elastic lung tissue itself
forced expiration depends upon the contraction of the inner intercostal and innermost intercostal muscles, which depress the ribs
accessory muscles that aid expiration + function
abdominal muscles- external oblique and rectus abdominis
further depress the thoracic cage while increasing intra abdominal pressure which pushes the diaphragm superiorly
what are the intercostal spaces?
eleven anatomical spaces present between the typically 12 pairs of ribs
contain the intercostal muscle, nerves, arteries and veins, along with the associated lymph vessels and nodes
organisation of the main neurovascular bundle
superior to inferior
vein - artery - nerve
What are the intercostal nerves?
ventral rami of the T2-T11 spinal nerves
ventral ramus of the first thoracic spinal nerve contributes to a large branch called the brachial plexus
a smaller branch passes into the first intercostal space as the first intercostal nerve
What is the ventral ramus of the 12th thoracic spinal nerve called?
subcostal nerve- innervates the lower part of the abdominal wall
function and structure of the intercostal nerves
innervate the intercostal muscles and provide branches to the parietal pleura and their respective dermatomes
lateral cutaneous branch pierces the intercostal muscle and provides sensation to the skin of the lateral thoracic wall
anterior cutaneous branch provides sensation to the anterior thorax and abdomen skin
how can the segmental innervation be viewed clinically?
shingles- reactivation or varicella zoster virus lying dormant in a dorsal root ganglion from an earlier chicken pox infection forms a rash following the dermatomes
Where is a chest drain inserted? + why?
lower part of of the intercostal space, to avoid damage to main neurovascular bundle
What are the main arteries in the lungs+ what do they form?
anterior and posterior intercostal arteries which form an anastomosis
Where are the intercostal arteries derived from?
anterior- segmental vessels from the internal thoracic branches of the subclavian arteries- which run deep to the thoracic wall 1cm lateral to the sternum
posterior- segmental branches of the descending thoracic aorta
most superior two posterior are usually branches of a superior intercostal artery, derived from the costocervical trunk o the subclavian arteries
What are the internal thoracic arteries usually used for?
coronary artery bypass graft- CABG
aortic coarctation definition
congenital condition whereby the aorta is narrow, usually in the area where the ductus arteriosus inserts
What can be used to visualise a coarctation?
cardiac magnetic resonance angiograph
main veins in lungs + where they drain
anterior and posterior intercostal veins
superior two veins drain into brachiocephalic veins
most others drain into the azygos venous system present on the posterior thoracic wall
intercostal veins on the right side join onto the azygos vein which drains into the superior vena cava
intercostal veins on the left are drained by accessory hemiazygos vein andlower hemiazygos vein
Where do the hemiazygos veins cross to join the azygos vein?
the midline
Where are the lymph nodes located?
alongside the internal thoracic arteries within the posterior intercostal spaces, where lymphatic vessels lie alongside the intercostal vessels
What are the lymph nodes in that position called?
Parasternal nodes
Important note in regards to breast tissue and drainage
lymphatic vessels from the medial portions of each breast drain to parasternal nodes
metastases from a breast tumour may drain to the contralateral thoracic wall and breast
Where do the lymph nodes drain?
thoracic duct carries lymph from all body regions except for the right side of the thorax, head, neck and right upper limb
What does the thoracic duct form and where?
thoracic duct forms within the abdomen as the cisterna chyli at the level of the first lumbar vertebra and ascends anterior to the thoracic vertebrae, inferior lying to the right side of the aorta
crosses to the left, where it receives lymphatic vessels from the left posterior intercostal spaces
reaches anterior to join and drain the venous angle between the left internal jugular and subclavian veins
the right lymphatic duct drains into the venous angle between the right internal jugular and subclavian veins
chylothorax definition
wall of thoracic duct is damaged, lymphatic fluid may leak into pleural cavitites
What is Horner’s syndrome?
compression of the sympathetic chains as they transverse the posterior thoracic wall, typically close to the superior thoracic aperture, by a tumour in the Apex of a Lung and causes drooping of the eyelid- partial ptosis, pupillary constriction- miosis and lack of sweating- anhydrosis
What is a tumour in the apex of the lung called?
Pancoast’s tumour
what type of epithelium are the pleura?
mesothelium
What does the mesothelium produce + function?
small amounts of pleural fluid that allows pleural layers to slide past each other without producing friction
two types of pleura
visceral- covers the lungs including fissures, which is continuous with parietal at hilum
parietal pleura - lines the walls of the pleural cavity- cervical, mediastinal, diaphragmatic and costal
explain innervation of pleura
phrenic nerves- innervate diaphragmatic mediastinal pleura
intercostal nerves- costal pleura
What causes the pleura to be kept close together?
normal surface tension, holds both layers close together to form a very small space called the pleural cavity
what may go wrong with the pleural cavity?
air- pneumothorax, fluid (blood- haemothorax)
excessive pleural fluid- pleural effusion/ lymph- chylothorax
all in pleural cavity may compress the lung and compromise respiratory function
4 parts of parietal pleura
cervical, costal, mediastinal and diaphragmatic
what is the costodiaphragmatic recess?
spaces formed by the parietal pleura between the thoracic wall and diaphragm
lung expands into this during deep inspiration
where may the recess extend below?
12TH RIB
what can cause a pneumothorax?
trauma or interventional procedures that may damage the parietal pleura which results in an ingress of air into the space
trauma- stab injury, rib fracture
underlying lung disease
spontaneous
tension pnemothorax definition
a progressive increase in air within the pleural cavity with each breath- the air being unable to escape upon expiration
leads to a rapid deterioration in respiratory function and is a medical emergency
can cause tachypnoea, tachycardia, hypotension
mediastinal shift, tracheal deviation- shift away from affected side
unilateral hyperinflation, hyperresonance and absent breath sounds on affected side
Trachea definition
Prominent midline structure, which is palpable in the neck where it lies anterior to the oesophagus
What structure is above the trachea + where does it change?
continuous with the larynx
the inferior border of which lies at the fifth/sixth cervical vertebrae
trachea structure + function
formed partly by approximately 15 incomplete hyaline cartilage rings which are deficient posteriorly permitting expansion of the oesophagus as swallowed food passes down its length
incomplete part of the C shaped rings of cartilage also provide a site of attachment for the trachealis muscle
trachealis muscle function
contract to narrows the airway during coughing to increase the velocity of airflow to help expel any objects irritating the tracheal lining
Where does the trachea birfurcate?
at the sternal plane- C5/C6 at the carina
where do the bronchi enter the lungs?
Enter the hilum approximately at the T5/T6 level
Structure of right bronchus
wider and more vertically orientated
divides into three secondary bronchi- correlating with the number of lobes in each lung
right primary bronchus is shorter, and divides before it enters the lung
structure of left bronchus
narrower and more horizontal
divides into two secondary bronchi
secondary bronchi then divide into tertiary/segmental bronchi which serves the bronchopulmonary segments of each lobe
How can the tracheobronchil tree be examined?
by bronchoscopy
Where are aspirated objects more likely to become lodged?
right bronchus, as wider and more vertical orientation
lung margins
apex, reaches the neck region above the clavicle- suprapleural fossa and is palpable here
apex separated from neurovascular structures passing through the neck by a sheet of connective tissue- suprapleural membrane
lateral surface of lung in contact with the thoracic wall is the costal surface
inferior diaphragmatic surface of each lung is called the base
medially each lung presents a surface in contact with the mediastinum, called the mediastinal surface
mediastinal surface has a root/hilum where the bronchi, blood vessels, nerves and lymphatic vessels enter and leave the lung
lung structure
left lung has two lobes
right lung has three lobes
both lungs divided into upper and lower lobes by the oblique fissure which passes through the entire depth
right lung has an additional horizontal fissure, separating the middle lobe from the upper lobe
upper lobe of left lung demonstrates a cardiac notch, inferior extension of which is called the lingula, which is a developmental homologue of the middle lobe of the right lung
what can each lobe be divided into?
bronchopulmonary segments, each associated with the terminal bronchi
How many segments in each lung?
10 in right
8-10 in left, as some segments duse
Explain structures of segments
each segment is separated by sheets of connective tissue
blood supply is segmental, with each segment receiving a branch from the pulmonary artery
clinical relevance of bronchopulmonary segments
knowledge of the anatomical arrangement is of importance in facilitating postural drainage of fluid or lung secretions
in supine patients the fluid will drain into the superior apical segments of the lower lobe
where do the bronchi lie relative to the arteries?
lie posterior to the pulmonary arteries of the right lung and inferior to the pulmonary arteries of the left lung at their entry point in the hilum
describe vasculature of hymen
Two pulmonary arteries- one right and one left
4 pulmonary veins- one superior and inferior leaving the hilum of each lung. Return oxygenated blood to the left atrium. Normally lie anterior and inferior to the pulmonary arteries and main bronchus
What is the pulmonary ligament and where does it lie?
fold of pleural membrane reflected at the junction between parietal and visceral pleura
Where do the lung tissue receive their blood supply from?
bronchial arteries originating from the aorta
small in comparison to pulmonary vessels and lie posterior to the main bronchi at the hilum
What is a pulmonary embolism?
venous thromboses can enter the lung circulation via a pulmonary artery and cause a blockage
explain lymphatic drainage of the lungs
lymphatic vessels surround the bronchial tree to form a deep lymphatic plexus
nodes surrounding the periphery of the lungs deep to the visceral pleura form the superficial lymphatic plexus
lymph from the superficial plexus drains into the bronchopulmonary lymph nodes situated at the hilum of the lung
lymph from the deep plexus drains first to pulmonary lymph nodes surrounding the secondary bronchi and then the bronchopulmonary nodes
bronchopulmonary nodes drain to tracheobronchial lymph nodes surrounding the tracheal birfucation at the carina
then drains to paratracheal nodes
lymphatic drainage from right lung is received by the right lymphatic trunk, as is lymphatic drainage from the lower lobe of the left lung
lymph from superior lobe of left lung drains to the thoracic duct at the left venous angle
Where is the apex located?
2cm above the medial clavicle
what is MAL?
Mid axillary line- found at the 4th costoclavicular cartilage
what is MCV?
mid clavicular line-
what is flail chest?
when a rib fracture results in a region of the rib cage becoming disconnected from the chest well.
the segment will then move with the lungs upon inspiration and expiration, not the ribcage
what is percussion of the chest?
an assessment technique which produces sounds by the examiner tapping on the patient’s chest wall
different sounds + what they mean
normal- no problem
dull- abnormal lung density, tumour pleural effusion
hyperresonant - too much air present in lung tissue, emphysema or pneumothorax
dullness due to?
heart/ liver
auscultation definition
listening to the internal sounds of the body, using a stethoscope
different areas of auscultation
heart, breathe sounds over trachea, lung fields
lung field definition
region of the body containing a lung
