Respiratory System Flashcards
What are the organs of respiratory?
- Nose
- Nasal Cavity
- Larynx
- Pharynx
- Trachea
- Right Pulmonary Bronchus
- Lungs
What are Pleural Layers?
A serous membrane
* Parietal pleura - lines thoracic cavity
* Visceral Pleura - Covers the lungs
What is a Pleural Cavity?
- Membranes secrete pleural fluid
- Lubricates the gap between both layers - reduce friction and heat during breathing
- Has negative pressure to atmosphere, pulling the lung onto the thoracic wall.
What is Pneumothorax?
Penetrating trauma to thoracic wall will draw air into the pleural space causing the thoracic pressure to become positive
Air will be drawn into the caivty during every expiration - restricts lung expansion
* Rupture in lung or chest wall allows air into pleural cavity
* Respiratory distress
* Tachyponea
* Rapid drop in sats
* Rapid drop in BP
* Tachycardia
Airway Structures
No respiration occurs in airway structures ‘dead space’
Important for gas to move in and out of the RS
What is the upper airway?
Extends from the nasopharynx to the larynx
Two openings :
* nares - natural, allows to smell danger and breathe when feeding
* mouth - occurs during exercise
What is the nasal cavity?
Hairs and turbinates in nasal cavities filter and humidify inspired air
10000 litres of air passes through per day
1 litre of moisture added to this air
Approx. 10-14cm long from nares to nasopharynx
What is the larynx made up of?
- Vallecula
- Epiglottis
- True vocal cords
- False vocal cords/vestibular fold
- Corniculate cartilage
- Glottis
What is the Mucociliary apparatus in trachea?
Allows impacted particles to be removed from the terminal bronchioles to the trachea by the ciliary beats of epithelial cells in the mucus of bronchi
Optimal humidity maintains the mucociliary transport system and consistency of secretions
What are alveoli?
Bronchioles continue to divide into terminal bronchiles
Terminate at the alveoli
300 million in lungs
Surface area of 70m^2
Allows a large surface area for gas exchange
Pulmonary capillaries wrap around the alveoli to enable gas exchange - extremely dense to maximise gas exchange
What is ventilation?
Movement of air in and out of the lungd involves pressure changes between thoracic cavity and the atmosphere
Changes in pressure is accomplished by contraction and relaxation of respiratory muscles
What are respiratory muscles?
- Intercostal muscles
- Diaphragm
- Accessory muscles during heavy breathing
What are the muscles of inhalation?
- Sternocleidomastoid
- Scalenes
- External intercostals
- Diaphragm
What are the muscles of exhalation?
- Internal intercostals
- External oblique
- Transervus abdominis
- Rectus abdominis
What does Boyles Law state?
The pressure of gas in a closed container is inversely proportional to the volume of the container
What happens during inspiration?
- Intercostal muscles contract, pulling the thorax up and out
- Diaphragm contracts, moving down towards abdominal cavity
- Increases the size of the thoracic cavity causing a -ve pressure to atmospheric
What happens during expiration?
Reverse
* Intercostals and diaphrah=gm relax, reducing the size of thorax
* Pressure increases in thorax
* Air is expelled
What is breathing quality evaluated in?
Volume
* Tidal volume (Tv) - 6mls/kg weight
* Minute volume (MV)
* Rate (RR) - not a volume
MV=Exp Tv x RR
Why is evaluation important?
- MV will dictate CO2 elimination
- Lower MV will result in increased CO2
- Higher MV will decrease CO2
- Reduction in Tv or RR can result in elevation in the other to compensate
How is homeostasis maintained?
Chemoreceptors will detect a change in CO2 levels and send impulses to respiratory centre
Increased CO2 - quicker deeper breathing
Reduced CO2 - slower breathing
How to assess ventilation?
- Looking
- Listening
- Spirometry
- Peak flow
- Chest auscultation
What are chest auscultation noises?
- Normal - quiet woosh
- Fluid in the alveoli - crackle
- Narrowed airways - wheeze
- Inflamed pleura - ‘rub’
What is gas exchange?
Divided into 2:
* External respiration
* Internal respiration
What is external respiration?
Pulmonary gas exchange
* O2 is taken up by blood and CO2 is released
* Occurs via diffusion due to pressure differences
* O2 and CO2 ‘exchange’ independently of each other
Surface area of respiratory membrane
Surface area is approx. 70m^2
* Oxygen must diffuse across this membrane into pulmonary capillaries
* Alveoli are arranged with septa separating each alveoli but with occasional openings (pores of Kohn) to allow collateral ventilation
What is Emphysema?
Reduction of respiratory membrane where alveolar sepra are destroyed by loss of elastic tissue
Pores of Kohn are more pronounced - deleterious effect on surface area
Side effects of ephysema
- Pink pallor
- Hystory of external dysphoea
- Tend to lose weight due to poor calorific intake
- Cant maintain satisfactory saturations due to increased RR
- Prone to infective exacerbations
What is Surfactant?
Fluid and air interface produces a tension
Surfactant lowers surface tension maintaining structure and enables expansion - prevents alveoli from collapsing suring expiration
* Normal water surface tension - 72 dynes/cm
* Alveolar fluid (no surfactant) - 50 dynes/cm
* Alveoli with surfactant - 5-30 dynes/cm
Made up of 4 proteins
* SP-A
* SP-B
* SP-C
* SP-D
Role of SP-A and SP-D
Protective role
* Inhibiting bacterial growth
* Activating macrophages
* Increasing macrophage membrane receptors
* Antioxidant properties to counter free radicals
Gas pressure and alveolar recruitment?
Pressure of alveolar gas ‘pushes’ against the alveolar walls keeping them recruited
Nitrogen plays a vital part - flushing out can lead to alveolar collapse as the oxygen will diffuse into circulation reducing the intra-alveolar pressure
Atelectasis
What is Henry’s law?
Partial pressure (p) is the measurement of the pressure a gas exerts within a container of fluid
Dictated by the kinetic energy its molecules display
P in soluation also dictated by its solubility coefficient
Affinity to water, greater affinity more dissolved exerting less p
What is Daltons Law?
Each gas in a micture exerts its own pressure
Atmosphereic pressure:
pO2 + pCo2 + pN2 + pH2O
159 + 0.3 + 597 + 3.7 = 760 mmHg
Atmospheric pressure at sea level is the accumulation of atmospheric gas partial pressures
O2 in external respiration
Blood returning from the right heart to the pulmonary circulation has an O2 partial pressure (pO2) of 40mmHg
Alveolar air has a pO2 of 105mmHg - 65mmHg difference
This difference cause O2 from the alveoli to diffuse into the pulmonary capillaries
What is Fick’s Law?
The rate of diffusion of gas across a membrane is relative to the partial pressure difference and surface area of the membrane.
Inversely proportional to the membrane thickness
What are pulmonary capillaries?
- Exchange occurs at a rapid rate
- Large surface area of the pulmonary capillaries enables this
- These capillaries are also very narrowing meaning RBCs touch the capillary wall as they squeeze through
- Capillaries closely arranged to the alveolar wall and the RBCs squeezing through ensures close proximity minimising diffusion distance
Oxygen carriage in blood
Thye diffused 02 then attaches to haemoglobin (Hb) molecules within the RBCs
4 02 molecules attach to 1 Hb molecule
Haemoglobin and altitude
- Ability to rapidly ascend leads to atitude sickness
- Insufficient time for acclimatisation
- Ventilation rate is inversely proportional to pO2 until acclimatisation is achieved
- Erythropoetin levels increase within hours of exposure leading to increase Hb
- Left shift O2 curve, so good Hb saturation with poor offloading
Oxygen carriage in pulmonary capillaries
- pO2 is important in determining the amount of O2 that binds to haemoglobin
- Higher the pO2 the more O2 binds to Hb
- So the SaO2 readings indicate the percentage of available Hb is saturated with a gas
CO2 in internal respiration
- O2 used by the tissues to make ATP produces CO2 as waste
- Transfer of C02 from the tissue to the blood is via a pressure gradient
- Tissue pCO2 is 46mmHg while tissue capillary pCO2 is 45mmHg
- A 1mmHg difference is enough to esnure exchange
What is cellular respiration?
Development of an oxygen rich atmosphere on earth gave rise to evolution of some anaerobic organisms into aerobic organisms
This adaptation enabled these organisms to take advantage of the greater energy production potention of aerobic cellular respiration
Occurs in 2 phases
* Glycolysis - the breakdown of glucose to pyruvic acid
* The complete oxidation of pyruvic acid to carbon dioxide and water
= energy (ATP)
What is energy?
Capacity to do work, chaange or move
ATP (Adenosine TriPhosphate) energy carrying molecule
Carbohydrate metabolism and ATP
Metabolism of carbohydrates results in the production of ATP
Produces via glycolysis and the Krebs cycle within mitochondria
ATP used as an energy source in muscle contraction, cell memberane transport, cell division and everything else
Aerobic and anaerobic metabolism
ATP can be produced in both presence sand absence of oxygen
* Aerobic - oxygen driven reaction produced high yield of ATP
* Glucose - Pyruvic acid - C02 + H20 + 38 ATP
* Anaerobic - oxygen absent, lower yield of ATP
* Glucose - Pyruvic acid - Lactic acid + 2 ATP
What is the significance of ATP?
Deleterious effect of hypoxia on ATP production
* Nerve conduction
* Muscle contraction
* Cell transport
* Cognitive function/LOC
Onset of hypoxia is rapid due to inability to store oxygen
Carriage of CO2
CO2 is carried in 3 different ways within the blood
1. Dissolved in plasma (7%)
2. Attached to Hb to form carboxyhaemoglobin (23%)
3. As bicarbonate ions (HCO3-) reacts with water in RBSs to form carbonic acid, this dissociated to for H+ and bicarbonate (70%)
CO2 + H2O - H2CO3 - H+ + HCO3-
This bicarbonate then moves out of the RBC down a concentration gradient into the plasma
When it reaches the pulmonary capillaries the reaction reverses forming CO2 and H2O
H+ + HCO3- - H2CO3 - CO2 + H20
Exchange of CO2
pCO2 in pulmonary capillaries is 45mmHg
pCO2 in alveoli is 40mmHg
5mmHg difference
This concentration gradient meant CO2 will diffuse across the respiratory membrane into the alveoli
Neuroanatomy of the respiratory system
Broken down to 3 distince parts
* Sensors - include a variety of mechano and chemo receptors that feed-back to the central command
* Control center - brain
* Effectors - resp. muscles
What are chemoreceptors?
Sense chemical changes in blood
Two broad types
* Central chemoreceptors - located in the medulla
* Peripheral chemoreceptors - located in aortic arch and carotid bodies
What are central chemoreceptors?
Highly sensitive to changes in pCO2
85% of ventilatory response
What are peripheral chemoreceptors?
Tend to respond to changes in PO2, PCO2 and H+
Made up of type I cells which synapse with plossopharyngeal nerve
High blood supply thus detect changes rapidly
What are the control factors?
Breathing rate and pattern can be voluntarily controlled
Protective measure to prevent unwanted substances from entering the lungs
What is sympathetic response?
Epinephrine and norepinephrine cause multiple changes
Emotional timulus will also release these sympathetic neurotransmitters
