Introduction to the respiratory system Flashcards
what are the functions of the respiratory system
- Gaseous Exchange
- Acid-Base Balance (in metabolic)
- Phonation
- Warming, humidification, filtration of gas
- Defence against airborne pathogens
describe the upper respiratory tract
Oro-pharynx & larynx.
Non-respiratory
describe the lower respiratory tract
Conducting airways- trachea and large bronchi.
Non-respiratory
what does non respiratory mean
this means that they do not exchange gases
what are the respiratory regions
Respiratory regions (alveoli and terminal bronchioles) Respiratory component of lungs.
what is the structure of the lungs
- top of the lung is apex
- bottom of the lung is base
on right hand side - 3 lobes - superior middle - inferior
- 2 fissures - oblique and horizontal
on the left hand side
- 2 lobes, superior and inferior
- 1 fissure - horizontal fissure
how many divisions are in the airway three
23 times
what divisions make up the conducting airways
The first 16 divisions make up the conducting airways
what divisions make up the respiratory zone
The last 7 make up the respiratory zone
how many alveolar ducts are in each lung
there are about 2^23 which is approx. 8 million alveolar ducts in each lung
- each duct divided into many terminal alveolar sacs each contain many alveoli
where does gas exchange take place
Gas exchange takes place in alveolar sacs and alveolar ducts, and to a lesser extent in respiratory bronchioles
what is the volume increase during alveoli
there is only about 20% volume increase in alveoli during normal inspiration
what happens to the alveoli during normal breathing
- they do not go from fully collapsed to fully inflated
- they stay partially inflated even at full expiration
what do alveoli do
- increase the surface area as the total surface of the alveoli is greater than 70m2
as the total cross sectional area of the airways increases…
the inward velocity of the gas during inspiration decreases
This low velocity together with the small increase in alveolar volume means that gaseous diffusion becomes an important component of gas exchange in the alveoli, at least during restful breathing.
what is a critical factors in gas exchange
Diffusion into and out of the alveoli and diffusion across the membranes surrounding the alveoli are critical factors in gas exchange in the lungs.
describe the function of the elastic fibres in the alveoli
- during normal expiration the elastic fibres around the alveoli produce passive elastic recoil which shrinks the alveolar volume
- alveoli does not collapse completely
what is the microanatomy of the conducting airways
- Ciliated pseudo-stratified columnar (or simple columnar) epithelium (varies with level)
- Cartilage / Smooth muscle (varies with level)
- Glands (sero-mucous, sub-mucosal)
what is the volume of air in the tidal volume approximately
500ml
what is the volume of air that stays in the conducting airways
150-200ml
what is the volume of air that goes to the alveoli
300-350ml
what is dead space gas
When you exhale, you have to breathe out the volume of the conducting airways first before you exhale alveolar gas. This is sometimes called dead space gas
what can increase dead space gas
- this can increase if the some of the alveoli does not have gas exchange
what epithelium is present in the upper airways
in upper airways there is thicker (more resistant to wear and tear) pseudostratified columnar epithelium
what epithelium is present in the lower airways
in lower airways simple epithelium
what epithelium is in the alveoli
In alveoli very thin epithelium to enable gas exchange
what is epithelium covered by
The epithelium everywhere except in the alveoli is covered with a layer of mucus
what does mucus do and what does cilia do
- mucus traps dust and bacteria, it is secreted by goblet cells
- Cilia moves the mucus upwards to the throat where it is swallowed and then it goes into the stomach where the acidity kills the bacteria
where are C shaped rings of cartilage present in
- present in the trachea
- present in the main bronchi
- these can stiffen the airways and prevent them collapsing
what is the movement of mucus by cilia called
MUCOCILIARY ELEVATOR
what are the two cells lining the alveoli
Type I pneumocytes (squamous, 90% of area)
Type II pneumocytes (cuboidal, 10% of area)
what other cells are present in alveoli
Macrophages, lymphocytes, granulocytes, Mast cells –these get rid of pathogens in the alveoli
alveoli are not..
lined with mucus as this impedes gas exchange, instead that contain immune system cells such as macrophages and lymphocytes to combat inhaled pathogens
- these cells move around the inside of the alveolus
what are the holes in the alveolar walls called
pores of Kohn
what are the pores of Kohn
These are pores between adjacent alveoli
what is the function of the pores of Kohn
they normalise pressure between alveoli thus allowing for collateral ventilation
what cells in the alveolus produces the surfactant
type II pneumocytes
what runs around the margins of the alveoli
capillaries
- type II pneymocytesf are found in the septa between the alveoli
what is a surfactant and what is the function of a surfactant
This is a phospholipoprotein dissolved in a watery secretion that lines the alveolar sac.
It reduces the surface tension in the alveoli and stops the alveoli collapsing during expiration.
what would happen if there was no surfactant
the alveoli would collapse
how do you work out the partial pressure of gas
Partial pressure of gas (A) = total pressure in gas mixture x fractional concentration of (A)
what is the unit of partial pressure of gas
mmHg
what do you do with the partial pressure of water vapour
- the air first inhaled is dry inspired air
- water vapour is added to the inspired air as it moves through the mouth or nasopharynx
therefore in order to estimate the partial pressure of oxygen in tracheal air you have to remove the parital pressure of water which is 47mmHg
what is the partial pressure of water
47 mmHg
what is the partial pressure of oxygen in the alveoli
100 mmHg
what is the partial pressure of carbon dioxide in the alveoli
40 mmHg
how does carbon and oxygen tensions vary between systemic and pulmonary ciruclation
Carbon and oxygen tensions vary between systemic and pulmonary circulation. Partial pressure of oxygen (PO2) is highest leaving the lungs, and that of carbon dioxide (PCO2) is highest entering the lungs.
what happens as you move up altitude
as you move up
- percentage of gas remains the same (oxygen fraction) but the total gas pressure is less therefore oxygen partial pressure does
- this means that the respiratory rate and depth must be increased at altitude - this means you will have to use oxygen supplementation at very high altitudes
what is the impact of respiratory disease
- single main cause of emergency admissions during a 4 year study period
- in London 8.3% of all deaths are due to respiratory disease mainly pneumonia, bocirhitis and emphysema
what are the respiratory diseases
Asthma
COPD (chronic bronchitis and emphysema, etc.).
Tumours (Carcinoma of the lung, mesothelioma, etc.).
Pulmonary fibrosis (including fibrosing alveolitis).
Occupational lung disease (silicosis, pneumoconiousis, asbestosis).
Disorders of chest wall, pleura and diaphragm (eg pneumothorax)
what are notable infections respiratory disease
Common cold (acute coryza) Influenza Pneumonia (viral, bacterial and fungal) Pulmonary tuberculosis (Poliomyelitis)
respiratory statistics
Respiratory disease accounted for 13% of all deaths in 2005 in those aged 65-74 years and 17% of all deaths in those aged 75 years and over.
In men aged 65 + chronic obstructive pulmonary disease (COPD) was the main cause of respiratory death, closely followed by pneumonia;
In women aged 65 + pneumonia was the most common cause, followed by COPD
GP registers for COPD suggest that the prevalence of diagnosed COPD in older people is 7.5%
During 2005/06 59 Westminster residents aged 65 years and over were identified as having been admitted to hospital as an emergency average 2.7 admissions.
common respiratory viruses
Rhinovirus Coronavirus Respiratory syncytial virus (RSV) Parainfluenza virus Adenovirus
what are the social, enivronmental, and occupational factors
social factors
Poor housing, nutrition and income (eg TB)
Smoking (COPD and CA-lung)
Travel (TB, etc.)
STDs and iv drug abuse (HIV, TB/pneumonia, etc.)
environmental factors
Air pollution, especially particulates and SO2 (COPD/asthma)
House dust mites (asthma)
occupational factors
Dust and chemical exposure, and allergies (asbestosis, mesothelioma, silicosis, pneumonconiosis, pulmonary fibrosis, fibrosing alveolitis, etc.)
