Organisms And Exchange 5

Question 1

Gas exchange system in mammals consists of…

Answer 1

TRACHEA (supported by cartilage to prevent it collapsing)
Trachea divide into BRONCHI that divide into smaller tubes, BRONCHIOLES
ALVEOLI at the end of bronchioles provide a large SA where gas exchange occurs

Question 2

Alveoli are adapted for gas exchange by…

Answer 2

Shape and large number produce large SA
Fluid lining allows gases to diffuse across
Only 2 cell layers separate blood&air (short diffusion pathway) - flattened epithelial cells (alveolar wall) & endothelial cells (capillary wall)
Large network of blood capillaries surrounding each alveolus provides large SA
Circulatory system maintains a high diffusion gradient
Ventilation mechanism maintains a high diffusion gradient

Question 3

Inspiration

Answer 3

EXTERNAL intercostal muscles CONTRACT 
INTERNAL intercostal muscles RELAX 
diaphragm CONTRACTS - flattens 
Increased volume of thorax
Pressure inside lungs decreases below atmospheric pressure and air enters lungs

Question 4

Expiration

Answer 4

INTERNAL intercostal muscles CONTRACT
EXTERNAL intercostal muscles RELAX
diaphragm RELAXES
Actions decrease the volume of thorax
Pressure inside lungs increases above atmospheric pressure and air is forced out of lungs
Elastic recoil of lung tissue helps to force air out of lungs

Question 5

Pulmonary ventilation

Answer 5

Total volume of air normally moved into the lungs in one minute
PULMONARY VENTILATION=TIDAL VOL X VENTILATION RATE
Tidal volume = amount of air taken in (dm3)
Ventilation rate = number of breaths per minute

Question 6

Gas exchange in insects

Answer 6

1 opening of tracheae through tiny holes on insects surface - SPIRACLES
2 spiracle leads to TRACHEAE
3 tracheae branch off to form finer tubes - TRACHEOLES
4 oxygen diffuses into cells through cell membrane of tracheole
5 carbon dioxide leaves through the reverse pathway

Question 7

Gills are adapted for gas exchange by..

Answer 7

Large SA provided by lots of Gill filaments which possess lamellae increasing the SA even more
Short diffusion pathway - 2 cell layers - epithelial later of lamellae and endothelial layer of blood capillaries
High diffusion gradient maintained by circulatory system, ventilation system, and the countercurrent system

Question 8

Gas exchange in plants

Answer 8

Gases diffuse in and out of leaves through stomata
Leaves are thin providing a short diffusion pathway
Respiration and photosynthesis maintain diffusion gradients
Mesophyll cells provide large SA
Gases diffuse down a conc gradient
Gases dissolve in moist cell walls
Gases diffuse across thin cell wall and cell membrane of mesophyll cells