HUBS192 Lecture 15 - Respiratory System II: The Lower Respiratory Tract Flashcards
what is the respiratory membrane?
type 1 pneumocytes that can also be described as simple squamous epithelial cells attached via a fused basement membrane to the capillary endothelium
what are the 5 components of the LRT?
1) larynx
2) trachea
3) bronchi
4) bronchioles (tiny bronchi)
5) alveoli
what are the 4 functions of the LRT?
1) conducts air to/from site of gas exchange
2) completes cleaning, warming and humidifying (moistening) of air
3) provides a barrier between the air and blood
4) a large surface area for gas exchange
what is the beginning of the LRT?
the larynx
what is the larynx?
a passage for air only that is anterior to the oesophagus
where is the larynx located?
located from the hyoid bone down to the trachea
what is the structure used to keep the airway patent down the LRT?
cartilage protects and maintains open airways
what is the largest part of cartilage around the larynx?
thyroid cartilage
what is the enlarged area of cartilage that sticks out anteriorly of the larynx?
the laryngeal prominence
-also known as the Adams apple in males
what is the cricoid cartilage of the larynx ?
a complete ring of cartilage, completely encapsulates the whole of the larynx
what is the epiglottis?
piece of cartilage that is pushed back by the tongue to prevent food from being swallowed down the trachea by pushing it down the esophagus
what is the function of the epiglottis?
cartilaginous structure that prevents food from entering into the airway by flopping down and covering the larynx ensuring food only travels down to the oesophagus
what happens when you swallow?
the tongue pushes backwards onto the epiglottis and the larynx itself lifts upwards
what does the word glottis mean?
voice box
what is the glottis used for?
used to produce sound
what is the glottis composed of?
within the glottis, there are folds of tissue that are attached to cartilages that provide movement and vibrations (sound)
what are the 2 sets of folds in the glottis?
1) vocal folds
2) vestibular folds (above the vocal folds)
what are the vocal folds within the glottis?
‘true’ vocal cords (inferior to the vestibular folds)
how does testosterone affect the vocal folds (cords)?
testosterone affects cartilage and muscle, resulting in longer, thicker folds = deeper voice
what are the vestibular folds within the glottis?
-‘false’ vocal cords (superior to the vocal folds)
what is the trachea?
pathway down to the lungs that is anterior to the oesophagus
where is the trachea located?
between the larynx and the primary bronchi
what are the 2 functions of the trachea?
1) maintains patent airway
2) continues to clean, warm and moisten air by respiratory epithelium
what structures allow the trachea to maintain a patent airway?
by C-shaped cartilage rings where the ends are connected by bands of smooth muscle called trachealis
-many elastin fibres in lamina propria/submucosa layers
what structure is used to move mucus up the trachea against gravity?
the mucociliary escalator
what is the function of the mucociliary escalator?
removes debris to be swallowed and digested
why is the cartilage of the trachea C-shaped?
to provide protection by keeping the airway open, but allow room for the oesophagus (posterior) and the trachealis muscle to contract for coughing to clear obstructions
which structure prevents food from entering the larynx?
the epiglottis
how many lobes are in the right lung?
3 lobes
how many lobes are in the left lung?
2 lobes
why does the left lung have 1 one less lobe than the right lung?
because of the location of the heart
what is the hilum of the lung?
where the bronchi and blood vessels enter
what is the ‘apex’ of the lung?
superior region of the lung
what is the costal surface?
outer surface against the ribs
what is the ‘base’ of the lung?
inferior region of the lung that’s sits on the diaphragm
what does the bronchial tree consist of?
- trachea
- primary bronchi
- secondary (lobar) bronchi
- tertiary (segmental) bronchi
- bronchioles
- branching….
- branching….
- branching….
- terminal bronchioles
what is the relationship between branching of the bronchial tree and the diameter and number of branches?
diameter decreases as branching continues and the number of branches becomes more and more and more as branching continues
how many branches are there between the trachea and the end of bronchiole tree?
16 branchings
what do terminal bronchioles signify the end of?
signify the end of the conducting region of the respiratory system
what are the 3 components of the trachea?
1) respiratory epithelium
2) C-shaped cartilage rings
3) trachealis muscle at posterior
what are 2 the components of the primary bronchi?
1) respiratory epithelium
2) cartilage and smooth muscle rings
what are the 3 components of the secondary and tertiary bronchi?
1) respiratory epithelium
2) goblet cell numbers reduce
3) cartilage plates
what is the diameter of bronchioles?
<1mm
what are the 2 components of the bronchioles?
- cuboidal epithelium
- no cartilage but thick smooth muscle for bronchoconstriction and dilation (no goblet cells either)
what is the diameter of terminal bronchioles?
<0.5mm
what does each terminal bronchiole supply?
each terminal bronchioles supply a pulmonary lobule (now entering the respiratory region)
what is the relationship between decreasing diameter and cartilaginous support?
as the diameter decreases there is less cartilaginous support till there’s no cartilage
what changes occur to the cartilage along the LRT?
complete ring in the larynx (cricoid), c-shaped in the trachea, complete rings in primary bronchi, become plates, and then absent in the bronchioles
what changes occur to the epithelial tissue along the LRT?
respiratory mucosa that decreases in height by the secondary bronchi then becomes cuboidal in the bronchioles, with no goblet cells present
what are the pulmonary lobules made up of?
made up of many alveoli (air sacs) that are arranged like bunches of grapes
what are 2 features of alveoli?
1) make up most of the lung volume
2) enormous surface area
what is the structure of an alveoli?
very thin walls composed of simple squamous epithelium on a thin basement membrane
-type I pneumocytes form wall of alveoli type II pneumocytes secrete surfactant
what is the external surface of an alveoli covered in?
covered in a fine network of pulmonary capillaries
what are alveoli?
pocket-like cells open at one side (open for air) covered by a dense capillary network
what are pneumocytes?
lung epithelial cells
what are the 2 types of pneumocytes?
1) type I squamous pneumocytes
2) type II cuboidal pnuemocytes
what do type I squamous pneumocytes form and what are they involved in?
form the respiratory membrane/blood-air barrier with capillary wall and shared basement membrane
- forms the wall of the alveoli itself
- involved in gas exchange
where are type II cuboidal pneumocytes located and what do they secrete?
- scattered among type I
- secrete surfactant
what is surfactant and what is its function?
a complex lipoprotein (phospholipid) that reduces the surface tension of alveolar fluid
why is it important to release surface tension in the alveoli?
to ensure that the alveoli do not collapse, keeping the airway open
what is the function of roaming macrophages
remove debris that makes it to the alveoli
what is the gas exchange membrane/respiratory membrane/blood-brain barrier?
where the capillary meets the alveoli wall
what is the gas exchange membrane/respiratory membrane/blood-brain barrier composed of?
1) alveolar cell layer (type I pneumocytes, the wall of the alveoli)
2) fused basement membranes or alveolar epithelium
3) capillary endothelium (thin squamous endothelial cell)
how does the structure of the LRT vary along its length?
the structure of the larynx allows production of sound and ensures only air can pass. From the trachea to the bronchioles, the airway becomes narrower, with less cartilage support, more smooth muscle, and flattening of the epithelia
what are the 5 key structures of the lungs?
- left lung: 2 lobes
- right lung: 3 lobes
- hilum: where vessels/bronchi enter
- apex at top
- curved base to sit against diaphragm
what structures form the respiratory membrane?
alveolus wall, fused basement membrane and capillary wall
what creates sound waves?
passing air that causes vibrations
what are the ‘true’ vocal cords used for?
used for normal phonation
what is phonation?
the process of the vocal cords producing certain sounds through a certain type of vibrations
what are the 2 functions of the ‘false’ vocal cords?
1) prevent foreign object entry to the glottis
2) can produce very deep sounds (not commonly used)
what happen during coughing in terms of the C-shaped cartilage rings and the trachealis?
both the C-shaped cartilage rings and trachealis contract during coughing
how does the process of the mucociliary escalator work?
this occurs by mucus produced from goblet cells and mucous glands coating the surface of the epithelium resulting in debris becoming trapped. The trapped debris is then moved by the cilia up to the pharynx to the oesophagus to be removed through oral uptake (sputum) or to be ingested
what happens to the respiratory epithelium and goblet cells in the secondary and tertiary bronchi?
- respiratory epithelium starts to decrease in height
- goblet cell numbers reduce
