Human Physiology - 6.4 Gas Exchange Flashcards
processes involved in physiological respiration
- Ventilation
- Gas Exchange
- Cell Respiration
Ventilation
maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing flowing in adjacent capillaries
The exchange of air between the atmosphere and the lungs – achieved by the physical act of breathing
Gas Exchange
The exchange of oxygen and carbon dioxide between the alveoli and bloodstream (via passive diffusion)
process of swapping carbon dioxide for oxygen
occurs in the alveoli of the lungs but the process of diffusion down concentration gradients between to blood and the air
Cell Respiration
The release of energy (ATP) from organic molecules – it is enhanced by the presence of oxygen (aerobic)
oxygen is used and carbon dioxide is produced
Physiological respiration involves
the transport of oxygen to cells within the tissues, where energy production occurs
It is comprised of three distinct processes and is not to be confused with cellular respiration (a single component of the activity)
Purpose of Ventilation
Because gas exchange is a passive process, a ventilation system is needed to maintain a concentration gradient in alveoli
the exchange of air between the atmosphere and the lungs (ie the physical act of breathing)
to maintain the concentration gradients the air must…
be refreshed frequently
Function of the lungs
it is a ventilation system by continually cycling fresh air into the alveoli from the atmosphere - O2 levels stay in the alveoli (and diffuse INTO the blood) and CO2 levels stay low (and diffuse FROM the blood)
why do you need a concentration gradient
so oxygen and carbon dioxide and flow down the concentration gradient without the use of energy - if used energy = taking away from other things (eg managing body tempreture)
benefits to the lungs
The lungs are also structured to have a very large surface area, so as to increase the overall rate of gas exchange
Lung structure
Air enters the respirator system through the NOSE or MOUTH and passes through the PHARYNX to the TRACHEA. The air travels down the trachea until it divides into two BRONCHI
The right lung is composed of three lobes, while the left lung is only comprised of two (smaller due to position of heart)
Inside each lung, the bronchi divide into many smaller airways called BRONCHIOLES (increasing in surface area). each bronchiole terminates with a closer of air sacs called ALVEOLI where gas exchange with the bloodstream occours
Alveoli
= give the long a huge area for gas exchange (the longs contains about 700 millions of them) –> the wall of the alveoli consists of a singular layer of very thin cells so the gases only have to diffuse a short distense
it is covered by a dense network of BLOOD CAPILLARIES with low oxygen and high CO2 concentrations –> they diffuse out down the concentration gradients
cells in the alveolus…
secrete a flud which keeps the inner surface of the alveolus moist allowing gases to dissolve
purpose of concentration gradients
ventilation maintains concentration gradients of oxygen and CO2 between air in alveoli and blood flowing in adjacent capillaries
How does ventilation work (2)
1) muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them
2) different muscles are required for inspiration and expiration because the muscles only do work when they contract
examples of antagonistic muscle action
external and internal intercostal muscles, and diaphragm and abdominal muscles as examples of antagonistic muscle action
Inhaling - info.
1) external intercostals muscles contract, ribcage moves up and out
2) diaphragm contacts, flattens, moves down
3) volume of thorax increases
4) pressure inside thorax drops below atmospheric pressure
5) Air flows into the lungs until pressure evens out
Exhaling - info.
1) Interal intercostals muscles contract, ribcage moves down and in
2) abdominal muscles contract, pushes diaphragm uo
3) volume of thorax decreases
4) pressure inside thorax rises above atmospheric pressure
5) air flow out of the lungs until pressure evens out
Alveolar cell types =
consist of an epithelial layer and extracellular matrix surrounded by capillaries
the alveoli contain some elastic fibres –> allow the alveoli to stretch as they are filled with air during inhalation –> spring back during exhalation in order to expel the CO2 rich air
Alveolar cell types =
consist of an epithelial layer and extracellular matrix surrounded by capillaries
the alveoli contain some elastic fibres –> allow the alveoli to stretch as they are filled with air during inhalation –> spring back during exhalation in order to expel the CO2 rich air
Type 1 pneumocytes
extremely thin epidermal cells that make up the all of the laveolus
Type 2 pneumocytes
Secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension
Alveolar Macrophages (dust cells)
are wandering macrophages that destroy bacteria and remove particulate matter (dust)
Structure of an Alveolus
Alveoli function as the site of gas exchange, and hence have specialised structural features to help fulfil this role:
1) They have a very thin epithelial layer (one cell thick) to minimise diffusion distances for respiratory gases
2) They are surrounded by a rich capillary network to increase the capacity for gas exchange with the blood
3) They are roughly spherical in shape, in order to maximise the available surface area for gas exchange
4) Their internal surface is covered with a layer of fluid, as dissolved gases are better able to diffuse into the bloodstream
Two types of alveolar cells –
type I pneumocytes and type II pneumocyteS
Type I pneumocytes (BIONINJA)
Type I pneumocytes are involved in the process of gas exchange between the alveoli and the capillaries
They are squamous (flattened) in shape and extremely thin (~ 0.15µm) – minimising diffusion distance for respiratory gases
Type I pneumocytes are connected by occluding junctions, which prevents the leakage of tissue fluid into the alveolar air space
Type I pneumocytes are amitotic and unable to replicate, however type II cells can differentiate into type I cells if required
Type II pneumocytes (BIONINJA)
Type II pneumocytes are responsible for the secretion of pulmonary surfactant, which reduces surface tension in the alveoli
They are cuboidal in shape and possess many granules (for storing surfactant components)
Type II pneumocytes only comprise a fraction of the alveolar surface (~5%) but are relatively numerous (~60% of total cells)
Type II pneumocytes secrete a liquid known as pulmonary surfactant which reduces the surface tension in alveoli
As an alveoli expands with gas intake, the surfactant becomes more spread out across the moist alveolar lining
This increases surface tension and slows the rate of expansion, ensuring all alveoli inflate at roughly the same rate
MORE ON THE MECHS OF BREATHING - MAINLY MOVEMENT — DONT BE LASY ACTUALLY WATCH THE VIDEO AT THE END
https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/64-gas-exchange/mechanism-of-breathing.html
BREATHING - MOVEMENT
When the pressure in the chest is less than the atmospheric pressure, air will move into the lungs (inspiration)
When the pressure in the chest is greater than the atmospheric pressure, air will move out of the lungs (expiration)
Chronic Obstructive Pulmonary Disease (COPD)
–> it is characterized by progressive airflow limitation
–> it can be classified as: mild, moderate or severe (based on measurement of Forced Expiratory Volume
Forced Expiratory Volume
= the max volume of air that can be exhaled in 1 second
Emphysema
Emphysema is a lung condition whereby the walls of the alveoli lose their elasticity due to damage to the alveolar walls
The loss of elasticity results in the abnormal enlargement of the alveoli, leading to a lower total surface area for gas exchange
The degradation of the alveolar walls can cause holes to develop and alveoli to merge into huge air spaces (pulmonary bullae)
The major cause of emphysema is smoking, as the chemical irritants in cigarette smoke damage the alveolar walls
The damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase
This elastase, released as part of an inflammatory response, breaks down the elastic fibres in the alveolar wall
Elastase activity can be blocked by an enzyme inhibitor (α-1-antitrypsin), but not when elastase concentrations are increased
A small proportion of emphysema cases are due to a hereditary deficiency in this enzyme inhibitor due to a gene mutation
Common symptoms of emphysema
include shortness of breath, phlegm production, expansion of the ribcage, cyanosis and an increased susceptibility to chest infections
Asthma - causes
Airborne allergens, such as pollen, dust mites, mold spores, pet dander or particles of cockroach waste
Respiratory infections, such as the common cold
Physical activity
Cold air
Air pollutants and irritants, such as smoke
Certain medications, including beta blockers, aspirin, and nonsteroidal anti-inflammatory drugs, such as ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve)
Strong emotions and stress
Sulfites and preservatives added to some types of foods and beverages, including shrimp, dried fruit, processed potatoes, beer and wine
Gastroesophageal reflux disease (GERD), a condition in which stomach acids back up into your throat
Asthma - consequences (symptoms)
SYMPTOMS:
1) Shortness of breath
2) Chest tightness or pain
3) Wheezing when exhaling, which is a common sign of asthma in children
4) Trouble sleeping caused by shortness of breath, coughing or wheezing
5) Coughing or wheezing attacks that are worsened by a respiratory virus, such as a cold or the flu
EXTREME CONCEQUENCES:
- A permanent narrowing of the tubes that carry air to and from your lungs (bronchial tubes), which affects how well you can breathe
Chronic Obstructive Pulmonary Disease (COPD) - causes
Main cause = smoking
Minor causes = exposure to industrial dusts or genetics
Chronic Obstructive Pulmonary Disease (COPD) - Consequences
Respiratory infections. People with COPD are more likely to catch colds, the flu and pneumonia. …
Heart problems. …
Lung cancer. …
High blood pressure in lung arteries. …
Depression.
Lung cancer - what is cancer
cancer is cause by a series of mutations in genes that control gell growth (oncogenes) and repair damaged DNA (tumour suppressor genes)
==> cells become abnormal by growing out of control and thus forming TUMOURS
cancer cells do not die, and no longer to the purpose of the original cell.
blood vessels grow around the tumours to supply food for cell growth
cancer cells detach and spread to other parts of the body
Oncogenes =
genes that control cell growth
Tumour =
large mass of cells that are growing out of control
Apoptosis
when normal cells commit cell suicide because they are no longer needed
cells that no longer do their job become =
undifferentiated
angiogensis =
blood vessels growing around tumours to supply food for cell growth
Metastasis =
when cancer cells detach and spread to other parts of the body
benign tumours =
remain in one place
malignant tumors =
spread to other parts of the body:
either via:
1) the bloodstream
or
2) the lymphatic system
tumours in the lungs
as tumors become larger and more numerous they undermine the lung’s ability to provide the bloodstream with oxygen
cancer represents 13% of all
global deaths
consequences of lung cancer
- just bullet points - for info refer to pg 24 of bio booklet
1) shortness of breath
2) coughing up blood
3) pain
4) fluid in the chest (pleural effusion)
5) cancer that spread to other parts of the body (metastasis)
6) shortened lifespan
causes of lung cancer (3)
1) carcinogens
2) genetic predispositions (develops from exposure from certain environmental factors + genetic mutations)
3) spontaneous mutations
causes of lung cancer - carcinogens
- they damage DNA
- when our bodies are exposed to carcinogens, free radicals have formed that try to steal electrons from other molecules in the body. These free radicals damage cells and affect their ability to function ad divide normally.
eg. tobaccos, asbestos, etc
Spirometry
https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/64-gas-exchange/spirometry.html
