Lecture 17 - The anatomy of breathing Flashcards
The lungs: where are they located?
Located in the thorax, separated by the heart and the mediastinum, which extends from its apex just above the clavicle, explains why severe neck lacerations may cause lung tissue damage, to the diaphragm
The diaphragm: what does it separate?
The abdominal and thoracic cavities
The lungs: what is their structure?
Conical shape with a soft spongy texture, with a diaphragmatic base (sitting on the diaphragm)
Costal surface - distal to the centre of the body, lying adjacent to the ribs
Mediastinal surface - proximal to the centre, facing the mediastinum
Structure of the right lung
Shorter and wider than the left lung (due to the presence of the liver)
Three lobes: superior, middle, and inferior
Two fissures: oblique (separating inferior from superior and middle) and horizontal (separating the superior and middle)
Structure of the left lung
Longer and thinner than the right lung (due to the presence of the heart) with a cardiac notch
Two lobes: superior and inferior
One fissure: oblique (separating inferior and superior lobes)
Hilum of the lung
On the mediastinal surface of the lung
This is the area where bronchi, pulmonary vessels, lymphatics, and nerves enter/exit the lung
Physical properties of the lungs
DIstensibility and elasticity
Distensibility: what is it and what affects it?
The ability of the lungs to expand
This is affected by connective tissue structure, level of surfactant, and the mobility of the thorax
Distensibility: what is it and what affects it?
The ability of the lungs to expand
This is affected by connective tissue structure, level of surfactant, and the mobility of the thorax
Also called compliance
Elasticity: what is it and what affects it?
The ability of the lungs to be stretched out and then return back to their original size
This is affected by elastic tissue surrounding the lungs which allow expansion and recoil
The pleura: what is it, where is it located, and what does it do?
A double-layered serous (producing serum fluid) membrane that is attached to the lungs
The visceral pleura adheres to the lung and the parietal pleura attaches to the thoracic wall and the diaphragm, and the space between the visceral and parietal pleura is known as the pleural cavity and this is where a thin layer of serous fluid is
The pleura helps the movement of the lungs and reduces friction during breathing by acting as a lubricant, it also creates a pressure gradient which assists in ventilation and reduces the spread of infection by compartmentalising each lung
Pneumothorax
Bony thorax: what does it do and what is it made of?
Protects the contents of the thorax (lungs, heart etc), facilitates movement of skeletal muscle, and aids with the structure of the thorax
The sternum, 12 pairs of ribs, and 12 thoracic vertebrae
The sternum: what is it made of?
A suprasternal/jugular notch is at the apex and there is one clavicle notch on each side of the sternum and then 1-6 clavicle notches are situated along the sternum
The three main bodies of the sternum are the sternal manubrium (superior), the sternal body (middle), and the xiphisternum process (inferior)
The sternal manubrium and sternal body are separated by the sternal angle and the sternal body and the xiphoid process are separated by the xiphisternal junction
The ribs: what are they?
Attached by the head and tubule to the thoracic vertebrae
Slope downwards and forwards
Ribs 1-10 are attached to the sternum by costal cartilage
Ribs are called true if they are connected to the sternum so 7 are true, 3 are false, and 2 are floating
Thoracic vertebrae
Head of rib articulates with the body of the thoracic vertebra
Tubercle of rib articulates with the transverse process of the thoracic vertebra
Intercostal muscles
Span the spaces between the ribs (intercostal spaces)
External intercostal muscles - superficial layer, run downwards and forwards
Internal intercostal muscles – middle layer
Innermost intercostal muscles – deep layer, run downwards and backwards
Intercostal vessels and nerves
They are present in the intercostal spaces between the internal intercostal and innermost intercostal muscles and they supply the muscles, adjacent skin and pleura
Diaphragm: what is it and what is it attached to?
Dome-shaped skeletal muscle with a central tendon that separates the abdomen and thorax
Attached to the xiphisternum, costal margin, 11th and 12th ribs, and the lumbar vertebrae
Contains openings for the inferior vena cava, oesophagus, and aorta
Inspiration: what is it, how does it occur, and what muscles make it occur?
Breathing in
Occurs as the lungs expand, causing the pressure in them to be lower than atmospheric pressure, drawing air in
Diaphragm contracts, moving downwards and increases the thoracic capacity by ~75%
Intercostal muscles contract, elevating the ribs and increasing the thoracic capacity by ~25%
Expiration: what is it, how does it occur, and what muscles make it occur?
Breathing out
Occurs as the lungs contract, causing the pressure in them to be higher than atmospheric pressure, pushing air out
Diaphragm relaxes, moving upwards and reducing thoracic capacity
Vertical diameter
Contraction of the diaphragm increases the thoracic capacity by around 75%
AP and transverse diameters
Anterior-posterior diameter - diagonal diameter
Transverse diameter - horizontal diameter
Contraction of the external intercostal pushes the sternum forward and the ribs out which increases the AP and transverse diameter
The two types of breathing
Quiet inspiration and expiration (occurring at rest)
Forced inspiration and expiration (during exercise / pulmonary illnesses)
Quiet inspiration
Contracting diaphragm flattens, increasing thoracic area by increasing the vertical diameter of the lungs
Contracting external intercostal muscles elevate ribs and increase the thoracic area by increasing AP and transverse diameter of the lungs
Forced inspiration
Pectoralis minor, scalenes, serratus, and sternocleidomastoid muscles are also used to increase the speed and amount of inspiration that occurs
Quiet expiration
Passive process - as the external intercostal muscles and diaphragm relax, expiration occurs due to the AP, transverse, and vertical diameter decrease
Forced expiration
Internal and innermost intercostal muscles depress the ribs, and abdominal muscles compress the abdomen and push the diaphragm upwards
