Exchange Flashcards
Why do amoebas not need specialised exchange surfaces?
all of the oxygen needed and all of the waste carbon dioxide can be exchanged by diffusion through the cell surface
the distance the substances have to travel are very small, the supply of O2 for large organisms is too far away
the amoebas metabolic activity is low, so O2 demands are low
the surface area to volume is very large
Why are gaseous exchange surfaces moist?
so oxygen dissolves in the water before diffusing into the body tissue
as a result, mammals have to minimise water evaporation
What are the features of the nasal cavity?
good blood supply to warm the air to body temperature
hairy lining which secretes musucs to trap dust and bacteria, protecting lung tissue from irratation and infection
moist surfaces increase the humidity of air which reduces evaporation from the exchange surfaces
What are the features of the trachea?
carrys clean, warm, moist air from the nose to the chest
wide tube supported by rings of flexible cartilage, which stop it from collapsing
the rings are incomplete so food can easily move down the oesophagus
contains goblet cells which secrete mucus to trap dust and bacteria
the ciliated epithelium cell beat and move the mucus away from the lungs to throat where it is swallowed and digested
cigerettes paryluse the cilliated epithelium
What is the bronchus?
the trachea divides into the left and right bronchus, leading to the lungs
they are similar to the trachea, with supporting rings of cartilidge but are smaller
What are the bronchioles? What are they made from?
the bronchi divide into many small bronchioles in the lungs
the smaller bronchioles have no cartlidge rings
the walls contain smooth muscle - constrict the bronchus and reduce diameter of airways
this allows the bronchies to contract and dilate
the changes the amount of air reaching the luings
the are lined with flattened epithelium so some gaseous exchange occurs
What are the alveoli? What is elastic recoil?
tiny air sacs which are the main gas exchange surface
unique to mammalian lungs
consists of a layer of flattened epithilal cells and collagen and elastic fibres
the elastic tissue allows the alveoli to stretch when air is drawn in
when they return to normal size they help squeeze air out
this is known as the elastic recoil of the lungs
What adaptations do the alveoli have?
they have a large combined surface area
thin layers - one epithelial cell thick
good blood supply - maintains steep concentration gradient
good ventilation -air moves out and in the alveoli which maintains a steep gradient
has a lung surfacant that makes it possible for the alveoli to remain inflated
Describe the porcess of inspiration?
the diaphragm at the base of thorax contracts and lower
the intercostal muscles contracts and move the ribs upwards and outward
the increases the volum of the thorax so pressure is reduced
it is now a lower pressure than atmospheric air so air is drawn into the lungs
What type of epithelium cells are in the walls of the air sacs?
squamous epithelium
What is the purpose of the elastic fibres in the alveoli?
prevent the alveoli from bursting
allow recoil to control the volume of air in the lungs
allow the alveoli to return to its original shape
Why is it not possible to expel all air from the lungs?
cartlidge presents the thorax from being completely flattened
held open by cartlidge and elastic fibres
How do the alveoli create a surface for efficient gaseous exchange?
squamous
small to give large SA:V
one cell thick - shorten diffusion distance
many alveoli - large total SA
elastic fibres allow them to return to original shape and expand
sufacant - remain expanded, maintain SA
