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