Respirtory Lectures Flashcards
What does the trachea do?
Keep airways open
Why does the trachea have rings of cartilage
Supports the airway
Keeps it open
Where are the alveolar sacs in the lungs
Not near the trachea and bronchi
Near the periphery
Gas exchange occurs here
Small distances for gases to diffuse. Very important for good lung function.
No mucous glands or goblet cells lining the alveoli- has a different covering of surfactant
What are the alveolar sacs surrounded by
By blood vessels O2 moves in
Describe the muco-ciliary-escalator
- Trachea has C-shaped hyaline cargilage. Present in lrge airway surfaces only. On the anterior surface, they prevent collapse.
- goblet cells among epithelial cells - make mucous
- seromucous glands on the submucosa secrete mucous. Passes from the glands to the surface. Glands and goblet cells secretion serve for REMOVAL OF BACTERIA AND PARTICLES
- pseudostratified cilated columnar epithelium on bronchi and bronchioles. Removal of particles to the pharynx- mucociliary escalator.
Where are alveoli found?
In the periphery. Very edge of lungs in the respiratory zone
This is where gas exchange occurs
Bands of smooth muscle lining the terminal bronchiole. If the smooth muscle contracts. We get bronchiole constriction.
No cartilage and no cilia.
Capillary network. Mesh over each of the alveoli. Each alveolus. Increasessurfacearea of blood supply
Cartilage runs out in smaller airways
Diameter of airway decreases with each branching
Tell us about surface area and the lung :D
Surface area of a person is proportionally related to their height.
SA of a lung of a average 70kg person is estimated to be 75m2 (sa of a tennis court)
What are the two cells of the alveoli. Describe them
Type 1 cell.
Skinny. The alveolar cells where gas exchange occurs. Sits on basement membrane tiny bit of connective tissue
Type 2 cell (looks like a ball)
Produces surfactant- phospholipids. Covers inside of alveolus. Creates moist surface between air and cells. Reduces surface tension
Clearence of deposited particles
Name and describe the two mechanisms and where
Mucocillary escalator- mucus produced by 2 cell types- seromucus glands and goblet cells lining the airways.
Located in the larger airways and nasal cavity.
Foregin particles- stuck on mucous, cilia constantly moves mucous up to pharynx where we would then swallow it.
Larger particles get caught higher up(will get trapped) and smaller particles travel further down. Very small particles can travel to the alveolus.
Second mechanism
Alveolar macrophages. Roam over the alveolar surface. Engulf small particles they migrate to small airways and mucociliary escalator or leave the lung via lymphatics.
What damage do small particles do?
Small particles (less than 0.3um) become embedded in the alveolar membrane.
They can cause
1. inflammation in the alveolar wall
- which can cause fibrosis in the alveolar wall and therefore decrease the compliance of the lung.
- destruction of the alveolar wall and forming large air filled sacs (cigarette smoking) bullae?
Breaks down alveoli and get a big sac. Big sac vs alveoli. Big sac less surface area
- Carcinogenic inhalants cancers. (Cancers change dna in cells)
May start up in the alveoli wall, bronchioles, larger airways or upper tract. All areas of the respiratory tract are exposed to the carcinogens
Damage caused by smoking
- Destroys cilia lining the airways.
Mucous doesnt move properly. Just stays there. Bacteria pools. They just aggregate there. - Damages and destroys the walls between the alveoli causing their collapse. (Lil grapes become a big bag)
- Leads to cancers in cells lining the airways or in parenchyma (airway and bronchiole)
Basically cancer in the alveoli or in different points in the airways
Google the word parenchyma.
Describe gas trapping
Damage to alveolar walls. Instead of small air sacs or grapes you get big bullae sacs. They fill with air that cant get out. Just stuck there (gas trapping)
Bronchioles collapse early during exhalation. Lungs get bigger in volume but take in smaller amounts of air. Surface area gets smaller.
Bullae causes two problems.
- Gas exchange- diffusion distance is too great. Hypoxia.
- Causes gas trapping.
Describe bronchitis
Blockage of airways
Bronchitis narrows the airways and its harder to breathe. Decreased radius increased resistance
- Thickness of wall increased due to inflammation
- Mucus build up due to damage to mucociliary escalator
Characteristics of the nasal cavity and its function
Warms the air and humidifies it when we breathe in
Minute ventilation
Minute ventilation (litres/minute)
Amount of air breathed per minute
Increase tidal volume and increased frequency of breathing increases minute ventilation
Tidal volume amount of air flowing in and out- normal breathing- gets bigger during excercise. During excercise frequency of breathing also increases
FEV1
FEV1: how much air you can breathe out in the first second. Healthy airways should be able to breathe out more than 75% of the air you breathed in in the first second of exhalation.
Describe buckle handle movement
Chest moves out and upwards during inspiration. Volume of thorax increases
In order to inspire…
The respiratory centre in the medulla stimulates the diaphragm and inspiratory muscles. Diaphragm contracts and moves down. Inspiratory muscles - intercostal muscles contract and pull the rib-cage out
What happens to change the pressure differences required inorder for us to inspire?
- Diaphragm moves down. Rib cage moves out.
- All of that increases the volume of the chest. Which decreases the pressure in the chest compared to room temperature.
So we get air going in. Area of high pressure to lower pressure
Factors affecting pulmonary ventilation
Factors affecting how your lung inflates
- airway radius
- lung and chest compliance
Chest compliance- how easy it is for the lungs to push out and take air back in &to move out exhale air.
E.g if your lungs are all fibrosed- stiff- harder to move
Muscle disease, scoliosis, decrease compliance
-Surface tension of alveoli
(Surfactant)
How many generations are there approximately from the trachea and alveoli. ?
23
Cross-sectional area and airway radius.
Airway radius decreases as we move down the pulmonary tree.
Cross-section area increases substantially in respiratory zone.
Cross section of trachea. Little change to generation 10. But after generation 16 a rapid increase
Control of airway radius.
The four things that bronchomotor tone is maintained by.
- vagal efferent nerves - Ach = BRONCHOCONSTRICTION
- sympathetic nerve supply - NA = BRONCHODILTION
- circulating- CIRCULATING catecholamines- beta receptors = BRONCHODILATION
- inhaled stimuli e.g cigarettes, dust, cold air -> reflex BRONCHOCONSTRICTION
bronchoconstriction increases resistance to air flow
Lung compliance
- Inspiratory muscles must overcome the resistance of the chest wall, the lung tissue and the airways to inflate the lungs in order to inspire
- Ease of stretching the lungs depends on consistency of the lung parenchymal tissue - fibrosis in this area - harder to breath- emphysema- bullae
- The surface tension of the air-fluid interface lining the alveoli
Lung compliance -stretchiness of lungs.
On inhalTion what happens.
In fibrosis wht happens.
On inhalation:
- collagen fibrils in prenchyma stretch and the alveoli are pulled to expand
- they recoil on exhalation
In fibrosis:
1. More collagen fibrils = less compliance
So its harder to stretch the lungs
- More fibroblasts in interstitium. Fibroblasts- not stretchy- more fibroblasts- thickened area.
Makes it harder for lungs to be inflated
What is the relationship between surface tension and compliance of the lung?
It is easier to inflate saline filled lungs than air filled lungs. (Surfactant- saline filled analogy)
Only a small increase or decrease in pressure required in order to pull lungs out to the same volume.
Elastic forced account for 1/3 of lung compliance.
Surface tension accounts for the remaining 2/3 of lung compliance.
What is surfactant? What does it do to surface tension?
Surfactant- a mixture of phospholipids, proteins and Ca2+
It reduces surface tension by 7-40%
(As opposed to not having any surfactant there)
Surfactant production does not begin until the 6-7th month of gestation.
Secreted by type two alveolar cells - approx 100ml in adult lung.
Alveoli tend to collapse. Smaller ones tend to collapse more than larger ones.
Measuring pulmonary ventilation
What can you use spirometry to measure and estimate the effects on pulmonary ventilation of?
Spirometry can give us an estimate of:
- Airway radius: look at inspiratory and expiratory flow rates.
- Lung and chest compliance: look at vital capacity and total lung capacity.
- Surface tension of alveoli: not usually a problem
What spirometry parameter can you use that indicates obstructive disease?
FEV1/FVC %
If less than 75% got an obstructive disease. Which is an airways problem.
Patients with a restrictive disease. E.g pulmonary fibrosis have decreased compliancs of lungs- they would have okay normal airways.
Spirometry measure pulmonary ventilagion
What do you look at for obstructive and restrictive disease?
OBSTRUCTIVE DISEASE- Something wrong with airway radius.
FEV1/FVC%
RESTRICTIVE DISEASE: lung and chest compliance.
Look at FVC
What is the characteristic lung function parameter of a restrictive disease?
Vital capacity or forced vital capcity
VC or FVC
What is the characteristic lung function parameter of obstructive disease?
FEV1/FVC (%).
If below 75%
Got an airways problem.
Examples of restrictive diseases.
Fibrosis
NOT emphysema. Actually get increased compliance– floppy lungs
Five factors affecting diffusion of gases
Four are described by ficks law
All gases passively diffuse across the blood gas barrier:
- partial pressure of gases on either side of the membrane. (Partial pressure difference)
- Thickness of alveoli epithelium
- Area of lungs available for diffusion (50m2 -tennis court)
- Solubility of gases - defined by diffusion constant (characteristic of the gas)
- Matching of ventilation and perfusion (all of this in order to get efficient diffusion)
What happens to barometric pressure in high altitudes or when diving under water?
High altitudes have decreased barometric pressure and therefore decreased pressure gradient to drive the diffusion of oxygen.
Conversely, diving under water or sitting in a hyperbaric chamber will increase barometric pressure and the increased pressure gradient to drive the diffusion of oxygen.
What are the two things that Partial pressure of a gas PP(gas) depend on?
PP(gas) = % of gas x PP(total) [Daltons Law] it depends on two things: 1. The actual TOTAL BAROMETRIC PRESSURE 2. the % of the gas that is in the mixture.
What is the air made up of
A tiny teeny but if CO2 and CO
20% Oxygen
80% Nitrogen
What is Henry’s law?
The amount of gas dissolved depends on PP
Amount of gas in solution depends on atmospheric pressure(pressure above of solution)
Henrys law: number of molecules dissolved in a liquid is proportional to the pressure exerted by gas at the liquid surface.
Content of dissolved gas (y) = solubility of y x partial pressure of y
How can we measure diffusion?
Use an oximeter- easiest
Another way is by taking an arterial blood sample for gas analysis
For an arterial blood sample normal
PO2 ~ 100mmHg
PCO2 ~ 40mmHg
We can measure the ability of the lungs to transfer gas from air to blood by a TLCO - transfer if lung of CO or DLCO test. Diffusion of lung of CO.
To measure diffusion( how good the membrane is at diffusing gas) why do we use CO?
We use CO because:
1. Diffuses easily across alveolar surface (it is very soluble)
All carbon monoxide that crosses membrane is absorbed by the blood (hemoglobin)
2. It is not normally present in plasma
And so we can measure how much is transferred from inhaled air to plasma.
Test is called DLCO or TLCO
Patients breathe a small amount of CO from a small bag and the amount taken up is measured.
Perfusion and ventilation matching
Lungs have local mechanisms for matching plasma and ventilation
Blood vessels and bronchioles
Local factors determine alveolar capillary flow
Capillaries collapse if PO2 falls in alveolus and blood is diverted away to other areas of the lung where PO2 is higher.
Bronchiolar diameter is regulated by PCO2 Levels in exhaled air. Increase PCO2 leads to bronchiolar dilation.
Oxygen consumption
At rest how much oxygen do we need per minute to support cellular activifies
250ml if oxygen
Oxygen solubility in blood is 3ml/L
Namely running the Sodium potassium pump in all our cell membranes
Each litre of blood contains how much oxygen?
Each litre of blood contains the equivalent of 200ml of oxygen at atmospheric pressure.
What are the two ways which oxygen is transported?
- Dissolved in plasma and erythrocyte cytoplasm (the amount dissolved in these places depends on the partial pressure.)
- Reversibly bound to Haemoglobin (Hb)
Henrys law predicts the amount dissolved will be proportional to the PO2 - 3ml/100ml
The other 197ml of oxygen is transported bound to Hb
The bohr effect
What factors make the curve shift to the right?
- decreased pH
- increased PCO2
- increased temperature
- increased 2,3-DPG
