The Respiratory System Flashcards
What are the upper respiratory tract structures
Nasal cavity
Pharynx
Nasopharynx
Oropharynx
Laryngopharynx
Larynx
What are the lower respiratory tract structures
Trachea
Bronchi
Bronchioles
Alveolar sacs
Alveoli
Describe the nasal cavities
Chambers internal nose through which air inhaled, warmed, humidified as moves further into the nasal cavities
Describe the scroll-shaped bones (nasal cavities)
Nasal conchae, protrude and form spaces through which air passes
Conchae swirl air around allowing time to humidify, warm and clean air before it enters lungs
Describe the epithelial cilia and mucous membrane line inside nasal cavities
Seromucous and other glands produce mucous that along with cilia traps unwanted large particles which we cough out and swallow
Describe the pharynx and oropharynx
Air and food have shared pathway so risk of choking
When breathing epiglottis stays up and air passes freely between laryngopharynx and larynx
Larynx connects lower part of pharynx, the laryngopharynx to the trachea
When eating glottis closes and epiglottis folds backward to cover the entrance larynx so food and liquid don’t enter trachea
Swallowing coordinated by neurons in brainstem
What are the functions of upper respiratory tract
Warming
Humidifying
Filtering particles
Smell
Speech
Describe the trachea
Fibro - cartilaginous tube
Extends from lower border of larynx to division into right and left main bronchi at the carina
C shaped cartilage
Posteriorly trachealis muscle
What is a bronchogram
When an X- ray or CT scan is completed after injection of a radio- opaque dye
Describe the right main bronchus
Wider
Shorter
More vertical than the left
Foreign body entering the trachea more likely to get stuck in the right main bronchus
Describe the pleura and pleural cavity
Pleura consists of a closed sac of serous membrane, one for each lung which contains a small amount of pleural fluid
Membrane of ballon is a single membrane, but when fist pushed ballon it is effectively coated in two membranes with water in between, so fist can slide around but not get wet and sac remains enclosed. So the lung can expand and recoil within the pleural sac lubricated by pleural fluid
Describe the pleural membrane
Although it’s described as two sheets, the visceral and the pleural membrane, the description refers to whether the layer is the outer or inner one : it is still all one membrane
The pericardium forms a similar arrangement around the heart allowing it to beat without friction
Describe how bronchi divides
Bronchioles
Terminal bronchioles
Respiratory bronchioles
Alveolar ducts
Alveoli
Describe the divisions of the lower respiratory tract
Air in the conducting zone = anatomical dead space
From nostril up to the start of the respiratory bronchioles
Volume of conducting airways = 150mls (approx 30% tidal volume)
No alveoli in this zone
So no gas exchange in this stretch
Describe alveoli
Vast surface area
Type I cells (squamous) cover 90% of surface area and permit gas exchange with capillaries
Type II cells (cuboidal) cover 10% of surface area and produce surfactant
Numerous macrophages line alveolar surface (phagocytose particles)
Describe the protection of lungs against infection
Epithelial lining of the respiratory tract
Pseudo stratified epithelium with cilia and goblet cells lines the airways from the nasal cavity to the largest bronchioles
Column shaped cells with cilia
Goblet cells between columnar cells
Further down respiratory tree there is less prevalent number of cilia and goblet cells
At alveolar level goblet cells or cilia could impede gas exchange so infection defence relies on antibodies, phagocytes and macrophages
Describe mucoiliary escalator
Mucous secreted by goblet cells and glands
Dust and other particles are deposited on the mucous layer
There is synchronous regular beating of cilia of the mucous membrane wafts mucous adhered particles up towards the pharynx mucous is then coughed up or swallowed
Describe intercostal muscles in respiration
11 pairs of intercostal muscles occupying the spaces between the 12 pairs of ribs, they are arranged in two layers, the external and internal intercostal muscles and are supplied by the intercostal nerves
Explain the external intercostal muscles in respiration
These extend downwards and forwards from the lower border of the rib above to the upper border of the rib below
They lift the rib cage upwards and outwards in inspiration
Explain internal intercostal muscles in respiration
These extend downwards and backwards from the lower border of the rib above to the upper border of the rib below, crossing the external intercostal muscle fibres at right angles
They are used when expiration becomes active as in exercise
Describe the diaphragm
Dome- shaped muscular structure supplied by the phrenic nerve and separating the thoracic and abdominal cavities
It forms the floor of the thoracic cavity and the roof of the abdominal cavity and consists of a central tendon from which muscle fibres radiate to be attached to the lower ribs and sternum and to the vertebral column by two crura
Describe accessory muscles of forced inspiration
Forced inspiration is assisted by the sternocleidomastoid muscles and the scalene muscles which link the cervical vertebrae to the 1st two ribs and increase rib cage expansion
When these muscles contract, they pull the ribcage upwards, supplementing the action of the external intercostal muscles
Describe accessory muscles of forced expiration
Quiet exhalation takes around 3 to 4 seconds
Recruiting accessory muscles of expiration shortens the expiration time, increases the speed and force of exhalation and allows respiratory rate to rise
Forced expiration is helped by contraction of the internal intercostal muscles which pull the ribcage downwards and inwards, compressing the lungs and aiding exhalation
Sometimes the rectum abdominis muscle is also used which compresses the abdominal organs increasing the upward pressure on the diaphragm and helps force air out the lungs
What is the average respiratory rate and 3 stages of each breath
12 - 15 bpm
Inspiration, expiration and pause
What occurs during inspiration
External intercostal muscles & diaphragm contract simultaneously, enlarging the thoracic cavity in all directions, the ribcage is anchored at the 1st rib which is fastened firmly to the sternum and the 1st thoracic vertebra, contraction of the external intercostal muscles lifts the ribcage as a unit upwards and outwards expanding the thorax
Diaphragm contracts muscles fibres shorten and central tendon pulled downward ps to level of 9th thoracic vertebrae lengthening the thoracic cavity
What occurs during inspiration ( continued)
Because the parietal pleura adheres to diaphragm and inside of the ribcage, pulled outwards along with them
Pulls visceral pleura outwards too, since the two pleura are held together by negative inter pleura pressure
As visceral pleura is firmly adherent to the lung, the lung tissue is pulled upwards & outwards with the ribs and downwards the diaphragm
This expands the lungs and pressure in alveoli & in air passages falls drawing air into the lungs
Process is active due to muscle contraction and lasts about 2 seconds
What occurs during expiration
Relaxation of the external intercostal muscles and the diaphragm results in downward and inward movement of the ribcage and elastic recoil of the lungs
This increases pressure inside the lungs and expels air from respiratory tract
At the end the lungs still contain some air and are prevented from complete collapse by the intact pleura
What occurs in the pause
Where everything is relaxed and the body pauses between the respiratory cycle
What are the physiological variables affecting breathing
Elasticity, compliance and airway resistance
What is elasticity
The amount of stretch in the lung itself and its ability to return to its normal shape
Diseases e.g. emphysema can cause scarring and a loss of elasticity meaning the lungs are not able to return to their normal shape and are slightly expanded
This increases resistance and makes it harder to breathe
What is compliance
How easy it is for the lung to stretch in the 1st place
Through disease or injury the lungs can become stiff and difficult to stretch and this means that it makes the work of breathing harder
What is airway resistance
Relates how easy it is for air to move through the airways
Resistance caused by inflammation, infection, scarring or foreign bodies can cause difficulty in breathing
What is the role of surfactant in respiration
Surfactant is produced by type II penumocytes in the lung
Helps reduce the friction and decreases surface tension within the alveoli and makes it easier for the alveoli to expand and contract
It has detergent properties and by reducing the surface tension within the alveoli it helps reduce work of breathing
Describe the mechanisms of respiration
Movement of the ribcage and the flattening of the diaphragm cause and increase in lung volume
Causes a drop in airway pressure
Air rushes to fill the vacuum
Causes the lungs to expand
Once the max amount of air has filled the lungs (lung volume)
Different ways to measure this
What is tidal volume
Amount of air that moves into the lung in one single respiratory cycle
What is functional residual capacity
Amount of air left in the lungs at the end of expiration ( stops alveoli from collapsing at end of expiration)
What occurs when diaphragm relaxes
The chest muscles relax and this causes the ribcage to begin to compress the lungs and decrease the space as you breathe out
Lungs return to their original shape due to elastic recoil
What is inspiratory reserve volume
Extra volume of air over and above normal TV that can be inhaled into the lungs during maximal inspiration
What is inspiratory capacity
Amount of air that can be inspired with max effort
It consists of tidal volume plus inspiratory reserve volume
What is expiratory reserve volume
Additional volume of air that can be expelled over and above normal TV during maximal expiration
What is peak expiratory flow
Measured with a peak flow meter and records the maximum speed of air flow during forced expiration
Measured in litres per minute and is only attained for a fraction of a second
Normal peak flow generally between 400 and 700 L/min
How is gas measured
Partial pressure within the human body
What is pCO2
Partial pressure of carbon dioxide
What is pO2
Partial pressure of oxygen
What is paCO2
Partial pressure of carbon dioxide in arterial blood
What is paO2
Partial pressure of oxygen in arterial blood
Describe the gas movement in alveoli
The amount of pO2 in the pCO2 in the blood stream and lungs are different and due to the difference in pressure, there is a pressure differential
Due to diffusion
The O2 and CO2 molecules swap places due to conc levels
Blood entering lung in pulmonary artery has low pO2 and high pCO2
Blood leaving lung in pulmonary veins has high pO2 and lower pCO2
What gases have to diffuse across
Alveolar fluid
Alveolar membrane
Alveolar basement membrane
Interstium ( connective tissue )
Capillary basement membrane
Endothelial membrane
Plasma
Red blood cell membrane
Describe gas diffusion
O2 enters plasma and dissolves in it
O2 enters RBC and binds to Hb
Process continues till Hb fully saturated ( binds to 4 O2 molecules)
98% oxygen delivered to tissue is delivered on haemoglobin
2% dissolved in plasma
Although only small amount oxygen dissolved in blood this determines how saturated Hb is
Describe gas movement in RBCs
Blood contains both dissolved and Hb bound oxygen
The pO2 reflects the amount of dissolved O2 in the blood
Dissolved O2 is available to diffuse into tissues down its partial pressure gradient
As dissolved O2 leaves the blood for tissues, it will be replaced by O2 bound to Hb unbinding for Hb and dissolving into the blood
This is how oxygen bound to Hb will be downloaded and diffuse into tissues
