Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
1
Circulation and gas exchange II (Chapter 42)
Keywords• Fish gill
– Filaments
– Lamellae
• Tracheal system
– Tracheoles
• Gastrovascularcavity
• Lung
• Tidal ventilation
• Ventilation in birds
Examples of gillsExamples of gills
Fish GillRather than being a solid
structure, the fish gill is finely subdivided to enhance gas
exchange area
2
filaments
Lamellaelamellae Countercurrent flow
CountercurrentAre gills effective in increasing
surface area?
1 kg
1 kg
0.06 m2
1.16 m2
Surface area
Lime jello cube
• 20 fold increase due to
gills
3
How do gill surface areas compare among different
fishes?
• Numbers correspond to arbitrary units
per gram body weight
Tracheal systems in insects
Tracheoles supply tissuesDiffusion distance from
tracheole to mitochondria is short
4
Tracheal system grasshopper
• Juvenile and adult
“femur”
• Adult femur volume
is primarily tracheal system
X-rays show that in beetles ranging over 1000X in size tracheal system
increasingly takes up more leg
space
Lungs
• Internal sacs
• Unlike insect tracheal system lungs do
not contact entire body
• Circulatory system draws oxygen from
lungs to tissues
• Found in snails, a few fishes, spiders, vertebrates
Structure of the mammalian lung
http://www.youtube.com/watch?v=vu_ONM3Bj9A
5
Tidal ventilation of mammalian lung• Negative pressure breathing
Tidal ventilation
• Tidal volume - volume inhaled and
exhaled (around 500 ml in humans)
• Tidal volume is much less than total
volume of lungs (several liters in humans)
• Thus residual volume remains after
exhaling
• This is inefficient
Birds have a more
“sophisticated” type of lung ventilation
• Birds have high metabolic rates
• Can be exposed to lower oxygen
concentrations in high altitude flight
• Ventilation is not tidal
• Air flows through the lungs
6
The avian respiratory system
7
Animation of avian lung
• http://www.youtube.com/watch?v=LbJU0o
cOKdo
The control of breathing
• Human brain monitors carbon dioxide level
(detected as a drop in blood pH)
• Hyperventilation in divers
• Diving mammals can tolerate high blood
carbon dioxide
Organismal respiration -- a simple view
CO2
CO2
O2
O2
mitochondriaCO2+H2O
O2
HCO3-+H+
4141
Adaptations for DivingAdaptations for Diving::•• Rapid breathing prior to dive Rapid breathing prior to dive --known as known as
apneustic breathingapneustic breathing
•• Lungs remove 90% of OLungs remove 90% of O2 2 from air (as from air (as opposed to 20% for humans)opposed to 20% for humans)
•• Elastic tissue in lungs helps them expand Elastic tissue in lungs helps them expand the lungs temporarily during apneustic the lungs temporarily during apneustic breathingbreathing
•• Marine mammals have more blood than Marine mammals have more blood than nonnon--diving mammals for their size (means diving mammals for their size (means more hemoglobin to carry oxygen)more hemoglobin to carry oxygen)
•• Muscles contain more myoglobin to hold Muscles contain more myoglobin to hold oxygen in tissuesoxygen in tissues
•• The heart rate slows dramatically during a The heart rate slows dramatically during a dive dive –– known as bradycardiaknown as bradycardia
•• Blood flow is reduced to extremities and Blood flow is reduced to extremities and digestive systemdigestive system
•• Muscles employ anaerobic respiration as Muscles employ anaerobic respiration as necessary (results in lactic acid buildnecessary (results in lactic acid build--up)up)
•• Marine mammals can tolerate more lactic Marine mammals can tolerate more lactic acid than other mammalsacid than other mammals
•• Rib cage and lungs collapse during dive to Rib cage and lungs collapse during dive to force air into tissues and prevent force air into tissues and prevent decompression sicknessdecompression sickness