ZOO 2090 Lecture Notes - Lecture 16: Lungless Salamander, Tiger Salamander, Skull
1 May 2018
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ZOO2090 – Respiration and Circulation in Tetrapods
Tetrapod Respiration
Primitive amniote
• Dermatocranium
• Neurocranium
• Palate
• Temporal muscle connects to lower jaw
Therapsid
• + temporal fenestrae
• +zygomatic arch
Mammal
• circular palate
Cutaneous Respiration in Amphibians
• low keratinization of the skin is required for efficient gas exchange, but low
keratinization results in water loss in air
• water or moisture is needed to maintain integument
• also need blood capillaries close to surface with increased SA
• Amphibians can increase their SA in different ways (e.g. with fingerlike papillae)
o Low-High Cutaneous Respiration:
▪ Tiger salamander
▪ Mudpuppy
▪ Bullfrog (larva)
▪ Bullfrog (adult)
▪ Hellbender
▪ Lungless Salamander
Tetrapod Lungs
• Generally, are paired with high surface-volume ratio; joining gut by trachea
• Trend towards increased compartmentalization associated with increased body size and
metabolic rate:
o Reptiles contain central bronchus, alveolar sac and secondary bronchus not
present in amphibians
The Buccal Pump of Amphibians (and some fish)
• Air is taken in through the nares by depression of the throat
• Glottis is opened and deoxygenated air in the lungs is rapidly expelled (thorax
compression), mixing little with air in buccal cavity
• Nares close and throat flow is brought up, pushing air into lungs against pressure
• Glottis close to keep air into the lungs and repeated pumping flushes into buccal cavity
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Document Summary
Primitive amniote: dermatocranium, neurocranium, palate, temporal muscle connects to lower jaw. Tetrapod lungs: generally, are paired with high surface-volume ratio; joining gut by trachea, trend towards increased compartmentalization associated with increased body size and metabolic rate, reptiles contain central bronchus, alveolar sac and secondary bronchus not present in amphibians. Inhalation diaphragm moves down while rib cage expands: exhalation small change in buccal cavity. Special adaptations in birds: unidirectional air flow, cross-current exchange, large exchange surface (10x more than mammals/volume, two cycle of inspiration and expiration to move air mass through system. *see phylogenetic pattern of lung ventilation among tetrapods. Blood vessels: there is a conservative pattern of arterial vessels, veins, amphibians: In salamanders, a new vessel (=postcava) drains most of blood from kidneys (body wall still drained by posterior cardinal) Response to special needs of organs: thermoregulation: keep blood to brain at appropriate temperature nasal rete, reduce heat loss from limbs.
