Gas Exchange in Humans

Question 1

Breathing mechanism that causes air to fill in the lungs

Answer 1

• Diaphragm (muscle) contracts and external intercostal muscles contract
• Causing pressure to decrease
• Air moves down a pressure gradient

Question 2

Process of gas exchange structures

Answer 2

Nose/ mouth -> Trachea -> bronchi -> broncioles -> alveoli

Question 3

Alveoli adaptations

Answer 3

Large surface area = lots of them
Rich blood supply = maintains conc gradient
Short diffusion path = one cell thick
Moist = gases dissolve and diffuse quickly

Question 4

Advantage of alveoli being moist

Answer 4

O2 dissolves
Easier for oxygen to diffuse into capillary and enter bloodstream

Question 5

Advantage of rich blood supply

Answer 5

Maintains conc gradient
Capillaries have constant low conc of O2 so O2 can constantly be diffusing into capillary and binds to haemoglobin

Question 6

Inspiration process

Answer 6

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

Question 7

Expiration process

Answer 7

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

Question 8

Why is diffusion between alveoli and blood fast

Answer 8

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

Question 9

What does the alveoli do

Answer 9

Exchanges oxygen and CO2 to and from capillaries in lungs

Question 10

Process of exchange between CO2 and O2

Answer 10

Simple diffusion
from high to low concentration

Question 11

How does simple diffusion occur

Answer 11

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

Question 12

Advantage of thin alveoli walls

Answer 12

Short diffusion distance to capillary network

Question 13

Extensive capillary network advantage

Answer 13

Short diffusion distance
Constant flow, oxygenated blood constantly brought away from alveoli and deoxygenated blood brought to them
Maintaining conc gradient

Question 14

What is ventilation definition

Answer 14

Mass flow of gases

Question 15

What does ventilation do

Answer 15

continuous flow of blood in capillaries, ensuring always higher concentation of O2 in alveoli than in blood

Question 16

What does the breathing movement allow

Answer 16

Air to change in alveoli
Supplying fresh O2 and removing CO2

Question 17

What does exercise do to oxygen demand

Answer 17

Oxygen demand increases
so ventilation rate increases

Question 18

How to calculate PVR

Answer 18

PVR = tidal volume x breathing rate

Question 19

What is the cilitated epithelium

Answer 19

SPecialised tissue found along down of trachea
Each cell has ciliar which sweeps mucus, dust and bacteria upwards away from the lungs

Question 20

What are goblet cells

Answer 20

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

Question 21

WHat is the squamous epithelium

Answer 21

Forms structure of alveolar wall and is very thin and permeable for easy diffusion of gases

Question 22

What does the smooth muscle do

Answer 22

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

Question 23

Dissecting biological speciment practical

Answer 23

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

Question 24

Potometers uses

Answer 24

When used with a water reservoirs they allow for air bubble to be returned to start of ube allowing water to enter system

Question 25

What is a respirometer

Answer 25

Three way tap used with a syringe to push coloured bead liquid back to start

Question 26

How does the alveolar work

Answer 26

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

Question 27

Features of the alveoli

Answer 27

1) Large number = increase SA
2) Thin walls = short diffusion distance
3) Large capillary network = short diffusion distacne and maintains conc gradient

Question 28

How to calculate the PVR

Answer 28

PVR divided by (tidal volume x breathing rate)

Question 29

Lung cancer describe

Answer 29

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

Question 30

What is COPD

Answer 30

Chronic obstructive pulmonary disease

Question 31

Symptoms of COPD

Answer 31

Shortness of breath, persistent cough, chest tightness

Question 32

How do you get COPD

Answer 32

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

Question 33

What does smoking a cigarette contain

Answer 33

Tar = carcinogen
Nicotine = addictive and narrows blood vessels
Carbon monoxide = reduces oxygen-carrying capacity of blood

Question 34

Cigarette smoking effects on air passages

Answer 34

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

Question 35

Cigarette smoking effects on alveoli

Answer 35

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