Gas Exchange in Humans Flashcards
Breathing mechanism that causes air to fill in the lungs
- Diaphragm (muscle) contracts and external intercostal muscles contract
- Causing pressure to decrease
- Air moves down a pressure gradient
Process of gas exchange structures
Nose/ mouth -> Trachea -> bronchi -> broncioles -> alveoli
Alveoli adaptations
Large surface area = lots of them
Rich blood supply = maintains conc gradient
Short diffusion path = one cell thick
Moist = gases dissolve and diffuse quickly
Advantage of alveoli being moist
O2 dissolves
Easier for oxygen to diffuse into capillary and enter bloodstream
Advantage of rich blood supply
Maintains conc gradient
Capillaries have constant low conc of O2 so O2 can constantly be diffusing into capillary and binds to haemoglobin
Inspiration process
1) External intercostal muscles contract, internal intercostal muscles relax
2) Ribs move up and out, increasing volume of thorax
3) Diaphragm muscles contract, increasing volume of thorax
4) Pressure in thorax is reduced
5) Atmospheric pressure greater than pulmonary pressure, forcing air in lungs
Expiration process
1) Internal intercostal muscles contract, external intercostal muscles relax
2) Ribs move down and in, decreasing volume of thorax
3) Diaphragm muscles relax and pushed up (by contents of abdomen)
4) Reducing thorax volume, increasing thorax pressure
5) Pulmonary pressure greater than atmosphere, air forced out
Why is diffusion between alveoli and blood fast
Diffusion:
-Red blood cells slow as they pass through capillaries = more diffusion time
-Distance is short between alveoli air and red blood cells when blood cells flatten against capillary walls
-Walls of alveoli and capillaries are thin = short diffusion
- alveoli and capillaries have large SA
Maintains steep concentration gradient
- Breathing movements keep lungs ventilated constantly, heart constantly circulates blood around alveoli
- Blood flow through capillaries
What does the alveoli do
Exchanges oxygen and CO2 to and from capillaries in lungs
Process of exchange between CO2 and O2
Simple diffusion
from high to low concentration
How does simple diffusion occur
Alveoli has high O2 conc and low CO2 conc
Capillaries has high CO2 conc and low O2 conc
simple diffusion = high to low
So CO2 moves into alveoli and out of alveoli into capillary
Advantage of thin alveoli walls
Short diffusion distance to capillary network
Extensive capillary network advantage
Short diffusion distance
Constant flow, oxygenated blood constantly brought away from alveoli and deoxygenated blood brought to them
Maintaining conc gradient
What is ventilation definition
Mass flow of gases
What does ventilation do
continuous flow of blood in capillaries, ensuring always higher concentation of O2 in alveoli than in blood
What does the breathing movement allow
Air to change in alveoli
Supplying fresh O2 and removing CO2
What does exercise do to oxygen demand
Oxygen demand increases
so ventilation rate increases
How to calculate PVR
PVR = tidal volume x breathing rate
What is the cilitated epithelium
SPecialised tissue found along down of trachea
Each cell has ciliar which sweeps mucus, dust and bacteria upwards away from the lungs
What are goblet cells
Scattered throughout ciliated epithelium in trachea
Mucus producing cells that secrete viscious muucs which traps dust, bacteria and other microorganisms preventing them from reaching lungs
Mucus swept along cilia of ciliated epthelium upwards and is swallowed
Mucus and any other microorganisms destroyed by acid in stomach
WHat is the squamous epithelium
Forms structure of alveolar wall and is very thin and permeable for easy diffusion of gases
What does the smooth muscle do
Found throughout walls of bronchi and bronchioles
Helps regulate flow of air into lungs by dilating when more air is needed and constricting when less air is needed
Dissecting biological speciment practical
1) lab coat, gloves, and eye protection worn
2) Place specimen on dissecting board
3) Use tools to access desired structure (cut away with scalpel, scissors used for cutting tissue, scalpel enables finer more precise cuts)
4) Use pins to move other sections of specimen aside to leave desired structure exposed
Potometers uses
When used with a water reservoirs they allow for air bubble to be returned to start of ube allowing water to enter system
What is a respirometer
Three way tap used with a syringe to push coloured bead liquid back to start
How does the alveolar work
1) Oxygen and CO2 exchanged through simple diffusion
2) Air in alveoli contains high conc of oxygen, O2 diffuses from alveoli into blood capillaries (high to low conc)
3) Blood of capillaries has low conc of O2 and high conc of CO2 so CO2 diffuses from blood into alveoli
Features of the alveoli
1) Large number = increase SA
2) Thin walls = short diffusion distance
3) Large capillary network = short diffusion distacne and maintains conc gradient
How to calculate the PVR
PVR divided by (tidal volume x breathing rate)
Lung cancer describe
TUmour develops if mutation occurs in oncogenes or tumour suppressor genes of bronchial epithelial cells
Mass of cells in lumen airways develop
Tumour develops into blood supply so no programmed cell death occurs
Symptoms: coughing up blood, coughing mucus, back or shoulder pain
What is COPD
Chronic obstructive pulmonary disease
Symptoms of COPD
Shortness of breath, persistent cough, chest tightness
How do you get COPD
Goblet cells in ciliated epithelium become enlarged and produce more mucus
Destroys cilia in trachea preventing them to sweep mucus away from lungs
Mucus contains bacteriam dust and ohther microorganisms and can block narrow bronchioles causing coughing, scar tissue adn injection
Infection attracts phagocytes to lungs releasing elastase which damages elasticity of alveolar walls
Alveoli breaks down and bursts
What does smoking a cigarette contain
Tar = carcinogen
Nicotine = addictive and narrows blood vessels
Carbon monoxide = reduces oxygen-carrying capacity of blood
Cigarette smoking effects on air passages
Tar destroys cilia (which carries dust and microbes trapped by mucus away from lungs) causing build up of mucus
Could lead to bronchitis as lining of bronchi become irritated
Cigarette smoking effects on alveoli
Tar contributes to break down of walls of alveoli causing them to merge together
Creates insufficient SA:V = less gas exchange
Reduces efficiency of gas exchanging causing emphysema where less O2 is crried in blood
Tar can build up and form layer on top of alveolar cells which can increase diffusion distance for gas exchange
