Basic Structure of the respiratory system Flashcards
Describe the flow of air into the lungs
Air is taken into the nasal or oral cavity- then enters the pharynx
Joins larynx
Trachea (terminates at T4/5 sternal angle)
bronchi
lungs
Describe the nasal cavities
Nasal septum separates two halves, and largely made of cartilage, but lined by olfactory mucosa - very sensitive, with trigeminal nerve innervation
Olfactory bulb and tract present at top of cavity, with olfactory mucosa to allow sense of smell (olfactory nerves arise from the bulb)
Describe the innervation of the nasal cavity
Olfactory nerves.
Nasopalatine nerve (V2).
Medial internal nasal br of ant ethmoidal nerve (V1).
Describe the nose
Part of the upper respiratory tract superior to the hard palate
Consists of the external nose and nasal cavities
The main function of these structures are olfaction and breathing
The lateral wall consists of conchae which provide a large SA covered in a highly vascuarlised mucous membrane to warm and humidify inspired air
Why does the nasal cavity exist
The nasal cavity exists to warm the air before it goes down into the lungs as cold air is an irritant.
What are the paranasal cavities also lines by
olfactory mucosa
Where are the olfactory nerves found in the nasal cavity
At the top
Describe the characteristics of the olfactory mucosa
very sensitive
even light can make you sneeze
Describe the paranasal sinuses
Lateral wall of cavity is not smooth - three ridges (concha)
Frontal sinus present above the eyes (frontal bone)
Sphenoidal sinus found in sphenoid bone below pituitary gland
Ethmoid air cells found high in cavity on each side of septum
Maxillae have openings to sinus above upper teeth - opening high up inside maxillary sinus, so any infection/mucous cannot leave via the opening
What is found underneath each concha
A groove or meatus
The paranasal air sinuses (frontal, sphenoid, ethmoid and maxillary) drain into these meatuses via small Ostia, or openings
What are the concha covered in
Respiratory epithelium
Describe the respiratory epithelium
Pseudostratified ciliated columnar epithelium
Describe the structure of the paranasal air sinuses
There are 3 major ridges known as the choncha – the inferior, middle and superior.
The sphenoidal sinus sits just bellow the sella turcicia (pituitary gland bone).
In the maxilliary sinus, the meatus that exits from it is located at the superior aspect which makes drainage difficult so this makes it difficult for the body to clear infection.
The maxilliary sinus is also very close to the teeth meaning dentists have to be very careful.
What are the functions of the concha
increase surface area of nasal mucosa to condition air before reaching the lungs (bone protrusions covered in respiratory epithelium - inferior concha lower in cavity with middle concha near the top)
What are the functions of the sinuses
- Lightens the skull by increasing strength to weight ratio.
- Acts as an insulator by trapping warm air- double glazing
- Protective for the brain- forms a crumple zone- at front of skull
- Affects the resonant quality of voice- resonance of voice changes when clogged with mucous
Why is it important that the air is humidified
cold, dry air is an irritant for the lungs
Describe how respiratory infections can get into sinuses
Issue for maxillary sinuses
In the maxilliary sinus, the meatus that exits from it is located at the superior aspect which makes drainage difficult so this makes it difficult for the body to clear infection.
The maxilliary sinus is also very close to the teeth meaning dentists have to be very careful.
What is the role of the mucosa
Warm or cool air
Moisten it
Capture bacteria and viruses
What happens when we are cold
Nasal mucosa tries to take heat and moisture from the air going out- countercurrent mechanism
Why we see water vapour on a cold day
What else do the concha do
aka turbinates
Disrupt smooth flow of air and direct it to the top of the nasal cavity to allow us to smell
increases contact between infiltrating air and the nasal mucosa, allowing particles in the air to be trapped before entering other parts of the respiratory system (e.g. the lungs).
Describe the pharynx
from top of nasal cavity to opening of the larynx; can be divided to three areas: nasopharynx (nasal cavity to end of soft palate), oropharynx (soft palate to epiglottis) and laryngopharynx (epiglottis to opening of airway)
What are the anterior aspects of each of the compartments of the pharynx
Nasopharynx- situated above the soft palate and opens anteriorly into the nasal cavities at the choanae
Orophaynx- mouth
Laryngopharynx- larynx
During swallowing, the nasopharynx is cut off from the oropharynx by the soft palate
Describe the basic structure of the larynx
Continuous with the trachea at its inferior end
Attached to the U-shaped hyoid bone and lies below the epiglottis of the tongue
The larynx consists of a cartilaginous skeleton linked by a number of membranes
the cartilaginous skeleton comprises the epiglottis, thyroid, arytenoid and cricoid cartilage.
Describe the anatomy of the larynx
All cartilage hangs from the hyoid bone
Epiglottis is attached posteriorly to the hyoid bone
Gives rise to thyroid cartilage via (thyrohyoid membrane)
Cricoid cartilage arise from thyroid cartilage via cricothyroid ligaments
Corniculate and arytenoid (vocal ligaments move medially) cartillages found posteriorly
Learn from diagram!
What are the functions of the larynx
As an open valve, to allow air to pass through when breathing Protection of the trachea and bronchi during swallowing. The vocal folds close, the epiglottis is pushed back covering the opening to the larynx, and the larynx is pushed upwards and forwards beneath the lungs Speech production (phonation)
Describe phonation
vocal ligaments vibrate to cause sound generation, and form sphincter to stop anything other than air going to airways
sphincter open in inspiration
What are some key facts about the larynx
Note the Hyoid bone, the only actual bone here.
Tracheostomies are performed in the Cricothyroid ligament.
Volume and pitch is controlled by the vocal ligaments (vocal folds)
The trachea is made up of around 20 rings of cartilage in horseshoe shapes into which the oesophagus can expand during peristalsis.
Describe the structure of the trachea
horseshoes of cartilage embedded in walls, but are deficient posteriorly; lined by same respiratory epithelium, with trachealis muscle posteriorly to join horseshoe; oesophageal muscle lies at back of trachea
Where doe the trachea extend from
the larynx to its bifurcation at the carina
Describe the tracheobronchiolar tree
The primary bronchus go into the lungs and then secondary bronchi are located in each lobe.
Tertiary bronchus go into bronchopulmonary segments.
All of the bronchi are held open by cartilage to some degree, the bronchioles are supported by smooth muscle cells.
The Corina is the name for the located of the bifurcation of the trachea into the bronchi. This occurs at the 2nd CC or T4/T5.
The right lung is split into 3 lobes; the left is split into 2.
The bronchiolar and alveolar surfaces are reduced by surfactant.
Where will object obstructing the lungs most likely be found
inferior lobe of the right lung, as the right bronchi is more vertical
Describe the bronchi
Bronchi held open by cartilage horseshoes and plates
Bronchiolar and alveolar surface tension reduced by surfactant
bronchiole has no cartilage (less cartilage as you go down)- so can present problems in asthma and related conditions; much smaller in diameter so greater resistance
Describe what happens when the diaphragm moves down
The pericardium moved down
it flattens out
Describe the basic structure of the pleura
Parietal faces the chest wall
Visceral faces the lungs
No difference structurally between the visceral and parietal pleura- changes at the hilum
Potential space between them- with serous fluid to allow the two pleura to move over each other and the lungs to expand
What is meant by the costodiaphragmatic recess
space beneath lungs to expand downwards towards abdomen
as left lung inflates- it moves in front of the pericardium- it Does not move symmetrically downwards
What can be seen in the hilum
Bronchi beginning to divide Antero-inferiorly- veins Superiorly- arteries Can distinguish between bronchi and vessels due to cartillage nerves lymph nodes and lympahtic vessels pulmonary ligament
Why can we not see any differences in thickness of the pulmonary arteries and veins
Both are low pressure circuits
Describe the topography of the lungs
Right Lung (left side, 3 lobes):
o The grooves are for the azygous vein and oesophagus.
o In the hilum, the pulmonary arteries (blue) and veins (red) can be seen alongside the bronchi and lymph nodes.
Left Lung (right side, 2 lobes):
o The arch of the aorta groove and the associated common carotid and subclavian can be seen.
The right side image is of the bronchopulmonary segments, each with independent blood supply and bronchioles
Where does vocalisation take place
The oral cavity
What drives oxygen across the blood-air barrier
PO2 Air = 100 mm HG ➔ PO2 Blood = 40 mm HG
Diffusion takes place down considerable pressure gradient
Describe the morphological barrier between the capillary and alveolus
1 cell thick epithelium (alveolar) and 1 cell thick endothelium (capillary)
It is exceedingly thin (average thickness of alveolar- capillary membrane is 0.4mm) and has an area between 50 and 100 square metres- making it well suited to gas exchange
Describe the removal of inhaled particles in the alveoli
The alveoli have no cilia
Removed by macrophages
foreign material is removed from lungs via lymphatics or the blood flow
leukocytes also participate in the immune response
Describe the diaphragm
The white part must be a tendon otherwise when the diaphragm contracts, the IVC would be crushed and we would die.
T10 is the level at which the oesophagus pierces the diaphragm.
The phrenic nerve originates at C3, 4, 5 and provides innervation to the diaphragm; without it, we would die as we wouldn’t breathe.
The vagus nerve passes anteriorly to the heart, the phrenic nerve runs posteriorly to the heart.
Breathing is carried out like a bucket-handle motion with lateral expansion.
Describe the position of the diaphragm
Margin attached to costal margin (lower edge of rib cage)
Centre of dome bulges up because of pressure difference between pleural and abdominal cavities
Highest in expiration
Describe the stability of the alveoli
Because of the surface tension of the liquid lining the alveoli; relatively large forces develop that tend to collapse alveoli
Fortunately, some of the cells that line the alveoli secrete surfactant that lowers the surface tension of the alveolar lining layer, preventing collapse and increasing stability.
What are the external intercostals involved in
inspiration
move the ribs upwards and outwards
Why do ribs expand laterally
Middle parts lower than posterior and anterior
so they expand laterally
ribs 7,8,9 and 10
What is meant by a plural cavity
Thin film of fluid between parietal and visceral layer- reduces friction to allow the pleurae to spill over each other in breathing
normally, no cavity is present, although in disease, the pathological potential may expand
