EAC Respiratory System Flashcards
respiratory systems four specific functions
Extract oxygen from the atmosphere and transfer it to the blood stream
excrete water vapour and Co2
Maintain acid base status of the blood
Ventilate the lungs
components of inspired air
O2 = 20% Nitrogen = 79% Inert gasses = 1% Carbon dioxide = 0.04% Water vapour (variable)
components of expired air
O2 = 16% Nitrogen = 79% Inert gases = 1% Carbon dioxide = 4% Water vapour (to saturation)
structure and function of:
Nasal cavity
The nasal cavity is a hollow space within the nose and skull that is lined with hairs and mucus membrane. The function of the nasal cavity is to warm, moisturize, and filter air entering the body before it reaches the lungs.
structure of:
Pharynx
The area of the respiratory tract behind the nasal and oral cavity extending down as far as the cricoid cartilage of the larynx. Its lined with mucous membrane and is composed of skeletal muscle.
functions of:
Pharynx
act as a passageway for air, food and water.
Is a resonating chamber for speech sounds.
Houses the tonsils.
three parts of the pharynx are:
nasopharynx - behind nasal cavity superior to the soft palate
oropharynx - extends from level of soft palate to level of hyoid bone
laryngopharynx - starts at the level of the hyoid bone leading to the oesophagus and the larynx
structure of:
Larynx
connects laryngopharynx with the trachea
lies in mid line of neck anterior to 4th - 6th cervical vertebrae (C4,5,6)
consists of Hyoid bone, thyroid cartilage and cricoid cartilage
there are 3 single cartilages (thyroid, epiglottis and cricoid)
there are also 3 paired cartilages (arytenoid, cuneiform and corniculate)
functions of:
Larynx
Production of sound
Speech
Protection of the lower respiratory tract during swallowing
Provide passageway for air from the pharynx to the trachea
Continues the process of humidifying, filtering and warming inspired air
in swallowing as the larynx rises the free edge of the epiglottis descends shutting of the respiratory tract preventing food, drink, secretions etc. from entering. Directing them down the gastrointestinal tract. should they pass into the larynx this stimulates the cough reflex which expels them from the respiratory tract.
structure and function of:
Epiglottis
Large piece of elastic cartilage attached to anterior rim of thyroid
It is leaf shaped
The leaf like portion is unattached and moves up and down like a trap door
structure and function of :
Thyroid
Forms anterior wall of the larynx and gives it its prominence
Connected to the hyoid bone by the thyrohyoid membrane
Structure of:
Trachea
Composed of 16-20 incomplete C shaped rings of cartilage that lie on top of each other. Providing semi-rigid support to trachea wall so that with changes of air pressure it does not collapse.
Incomplete part of C faces oesophagus
Extends from Larynx to the level of 5th thoracic vertebrae (T5)
Approx. 12cm long and 2.5cm diameter
Inner layer lined with ciliated columnar epithelium containing goblet cells
terminates at the Carina, formed by the last C shaped ring at the level of T5, dividing into left and right primary bronchus.
Function of:
Trachea
Support and Patency
Mucociliary escalator
Cough reflex
Warming, humidifying and filtering air
structure of:
Bronchus/Bronchi and Bronchioles
The right primary bronchus is more vertical, shorter and wider then the left. An aspirated object is therefore more liable to enter the right primary bronchus.
Primary bronchi divide to form smaller secondary (lobar) bronchi
Secondary bronchi branch off forming smaller tertiary bronchi
tertiary bronchi divide into bronchioles
bronchioles branch repeatedly until they’re minute, termed ‘Terminal bronchioles’
this branching from the trachea is commonly referred to as ‘the bronchial tree’
structure changes as The Bronchial Tree extends
epithelium changes from pseudo-stratified ciliated columnar epithelium in bronchi to non ciliated simple cuboidal epithelium in terminal bronchioles
incomplete rings of cartilage in primary bronchi are gradually replaced by plates of cartilage that finally disappear
as the amount of cartilage decreases the amount of smooth muscle increases
smooth muscle encircles the bronchioles in spiral bands
dilation of this muscle will increase bronchiolar diameter
function and structure of: Alveolar ducts and Alveoli
Terminal bronchioles - respiratory bronchioles - alveolar ducts
alveolar ducts end in the air sacs/Alveoli
gas exchange can only take place in the Alveoli and walls of alveolar ducts
Structure of:
Lungs
the lungs are 2 coney shaped, spongy organs situated either side of the mediastinum within the thoracic cavity
the right has 3 lobes and the left 2 lobes
has an apex, base, costal surface and medial surface
All structures enter the lung at the hilum on the medial surface
the lungs and the interior of thoracic cavity are lined by serous membrane (the pleura/pleural membrane)
thoracic cage firmly attached to and lined by parietal pleura
lungs enclosed and protected by visceral pleura
the two layers are in close contact during normal health separated by a thin film of serous fluid
between the two layers is the pleural cavity, filled with serous fluid to reduce friction allowing them to slide easily over one and other during breathing
blood supply to the lungs
the blood supply to the lungs is a double circulation:
pulmonary circulation
Systemic circulation
define:
Pulmonary circulation
that which takes part in respiration. the pulmonary trunk (from RV) splits into left and right pulmonary arteries containing de-oxygenated blood. Gaseous exchange takes place and oxygenated blood goes through the venous side of the pulmonary circulation
define:
Systemic circulation
That which provides blood to the lung as an organ. Particularly the bronchi and bronchioles. This circulation returns either to the superior vena through its own venous network or by connections between bronchial and pulmonary arteries
mechanics of Ventilation
the process of gases being exchanged between the atmosphere and alveoli
the pressure inside the alveoli with respect to atmosphere is changed by changes in the size of the lungs
during inspiration air pressure is less than atmospheric and air is drawn into lungs
during expiration pressure within lung rises to above atmosphere and air is expelled from the lungs
mechanics of Ventilation:
Diaphragm
the diaphragm in its relaxed form is dome shaped. when it contracts is flattens which increases the size of thoracic cavity causing pressure to fall.
inspiration is initiated by the phrenic nerve originating from the cervical spine at c3, c4, c5 (c3,4 and 5 keep the diaphragm alive)
mechanics of Ventilation:
Inspiration
muscles in ribs contract and pull cage upwards and outwards. altering the shape of the rib cage.
diaphragm pulls downwards and flattens out. Increasing the size of the thoracic cavity.
atmospheric pressure rises to above Intrathoracic pressure and air is drawn into the lungs from the atmosphere.
inspiration is initiated by the phrenic nerve originating from the cervical spine at c3, c4, c5 (c3,4 and 5 keep the diaphragm alive)
mechanics of Ventilation:
expiration
diaphragm relaxes and reverts to dome shape reducing size of thoracic cavity.
intercostal muscles relax bringing the rib cage downwards and inwards reducing size of thoracic cavity.
Intrathoracic pressure then rises to above atmospheric and air is expelled from lungs into atmosphere.
define:
Anatomical Dead Space
in normal quiet breathing the lungs and air passages are never empty. Gaseous exchange can only take place in the Alveolar ducts and the alveoli. The remaining capacity of the respiratory passages, where gaseous exchange cannot take place, is termed the anatomical dead space (about 150mL)
define:
Tidal Volume
This is the amount of air passing into and out of the lungs during each cycle of normal quiet breathing (about 500mL at rest)
define:
Minute Volume
Minute volume = tidal volume X breathing rate per minute
define:
diffusion
the movement of molecules from and area of high concentration to an area of low concentration, down the concentration gradient, until all areas are of equal concentration
define:
Internal Respiration
the exchange of gases (as oxygen and carbon dioxide) between the cells of the body and the blood by diffusion
define:
External Respiration
the exchange of gases between the external environment and the blood
by diffusion in the lungs between the alveoli and the blood
due to changes between atmospheric pressure and the pressure in the thoracic cavity
Describe how respiration is controlled:
voluntary control
exerted during speaking, singing, holding breath. the centre for this control is in the cerebral cortex (outer layer of the brain)
it can be overridden by a rising level of paCo2 and acidity causing involuntary respiration
Describe how respiration is controlled:
involuntary control - inspiration
the respiratory centre is in the Medulla Oblongata.
It is concerned with inspiration.
nerve impulses pass vie the phrenic nerve to the diaphragm and via intercostal nerves to the intercostal muscles. Resulting in contraction of these muscles and therefore inspiration
Describe how respiration is controlled:
involuntary control - expiration
the Pneumotaxic Centre is in the Pons Varolli receives impulse from nerve endings in the lungs sensitive to stretch, stimulated when the lungs are inflated. causing expiration to occur.
define:
acid base balance
the regulation of hydrogen ions (H+) in body fluid and the maintenance of balance between acid and alkaline.
the number of H+ in a solution is a measure of its acidity. unit of measurement is pH (the power of hydrogen)
Respiration Rates
0-12months 30-40BreathsPM
1-2yrs 25-35BPM
2-5yrs 25-30BPM
5-11yrs 20-25BPM
Adult 12-20BPM
define:
Dyspnea
difficult or laboured breathing.
define:
Apnea
cessation of respiration
define:
Hypoxia
deficiency in the amount of oxygen reaching the tissues
define:
Hypercarbia
More than the normal level of carbon dioxide in the blood
Describe how respiration is controlled:
involuntary control
Chemo Receptors - in the respiratory centre (central chemo receptors) and in arterial walls (peripheral chemo receptors)
central chemo receptors respond to PCO2 rises increasing ventilation and reducing PCO2.
peripheral chemo receptors found in the arch of aorta and in the bifurcation of common carotids on each side. They respond to changes in blood CO2 and O2 levels. Even a slight CO2 level rise activates these receptors by impulses sent to respiratory centre via Glossopharyngeal and Vagus nerves. This stimulates an immediate rise in rate and depth of respiration. An increase in blood acidity also stimulates them resulting in increased ventilation, increasing CO2 excretion and increasing blood ph. They also help regulate blood pressure
lung volumes:
Inspiratory Reserve Volume IRV
the extra volume of that can be inhaled into the lungs during maximal inspiration
lung volumes:
Inspiratory Capacity IC
this is the amount of air that can be inspired with maximum effort. it consists of TV (500ml) plus the IRV
lung volumes:
Functional Residual Capacity FRC
This is the amount of air remaining in the air passages and alveoli at the end of quiet expiration. Tidal air mixes with this air, causing relatively small changes in the composition of alveolar air. as blood flows continuously through the pulmonary capillaries, this means exchange of gasses is not interrupted between breaths, preventing moment to moment changes in blood gases. The functional residual volume also prevents collapse of the alveoli on expiration.
lung volumes:
Expiratory Reserve Volume ERV
This is the largest volume of air that can be expelled form the lungs during maximal expiration.
lung volumes:
Residual volume RV
this cannot be directly measured but is the volume of air remaining in the lungs after forced expiration
lung volumes:
Vital Capacity VC
this is the maximum volume of air that can be moved into and out of the lungs.
VC = TV + IRV + ERV
lung volumes:
Total Lung Capacity TLC
This is the maximum volume of air the lungs can hold. In an adult of average build, it is normally around 6 litres
