Lung Structure Biography
(Source google.com)
The avian respiratory system
delivers oxygen from the air to the tissues and also removes carbon dioxide. In
addition, the respiratory system plays an important role in hermoregulation
(maintaining normal body temperature). The avian respiratory system is
different from that of other vertebrates, with birds having relatively small
lungs plus nine air sacs that play an important role in respiration (but are
not directly involved in the exchange of gases). Pulmonary air-sac system of a
Common Teal (Anas crecca). a. Latex injection (blue) highlighting the location
of air sacs. b, Main components of the avian flow-through system. Abd,
abdominal aire sac; Cdth, caudal thoracic air sac; Cl, clavicular air sac;
Crth, cranial thoracic air sac; Cv, cervical air sac; Fu, furcula; Hu, humerus;
Lu, lung; Lvd, lateral vertebral diverticula; Pv, pelvis; and Tr, trachea (From: O'Connor
and Claessens 2005).
The air sacs permit a
unidirectional flow of air through the lungs. Unidirectional flow means that
air moving through bird lungs is largely 'fresh' air & has a higher oxygen
content. In contrast, air flow is 'bidirectional' in mammals, moving back and
forth into and out of the lungs. As a result, air coming into a mammal's lungs is mixed with 'old' air (air that has
been in the lungs for a while) & this 'mixed air' has less oxygen. So, in
bird lungs, more oxygen is available to diffuse into the blood (avian
respiratory system). The air sacs permit a
unidirectional flow of air through the lungs. Unidirectional flow means that
air moving through bird lungs is largely 'fresh' air & has a higher oxygen
content. In contrast, air flow is 'bidirectional' in mammals, moving back and
forth into and out of the lungs. As a result, air coming into a mammal's lungs is mixed with 'old' air (air that has
been in the lungs for a while) & this 'mixed air' has less oxygen. So, in
bird lungs, more oxygen is available to diffuse into the blood (avian
respiratory system). Bird-like respiratory systems in
dinosaurs -- A recent analysis showing the presence of a very bird-like
pulmonary, or lung, system in predatory dinosaurs provides more evidence of an
evolutionary link between dinosaurs and birds. First proposed in the late 19th
century, theories about the animals' relatedness enjoyed brief support but soon
fell out of favor. Evidence gathered over the past 30 years has breathed new
life into the hypothesis. O'Connor and Claessens (2005) make clear the unique
pulmonary system of birds, which has fixed lungs and air sacs that penetrate
the skeleton, has an older history than previously realized. It also dispels
the theory that predatory dinosaurs had lungs similar to living reptiles, like
crocodiles.
The avian pulmonary system uses
"flow-through ventilation," relying on a set of nine flexible air
sacs that act like bellows to move air through the almost completely rigid
lungs. Air sacs do not take part in the actual oxygen exchange, but do greatly
enhance its efficiency and allow for the high metabolic rates found in birds.
This system also keeps the volume of air in the lung nearly constant. O'Connor
says the presence of an extensive pulmonary air sac system with flow-through
ventilation of the lung suggests this group of dinosaurs could have maintained
a stable and high metabolism, putting them much closer to a warm-blooded
existence. "More and more characteristics that once defined
birds--feathers, for example--are now known to have been present in dinosaurs,
so, many avian features may really be dinosaurian," said O'Connor. A portion
of the air sac actually integrates with the skeleton, forming air pockets in
otherwise dense bone. The exact function of this skeletal modification is not
completely understood, but one explanation theorizes the skeletal air pockets
evolved to lighten the bone structure, allowing dinosaurs to walk upright and
birds to fly.
Lung Structure Lungs Diagram of a Smoker after Smoking Cancer Anatomy And Heart Drawing Images AFter Smoking Wee of a Weed Smoker
Lung Structure Lungs Diagram of a Smoker after Smoking Cancer Anatomy And Heart Drawing Images AFter Smoking Wee of a Weed Smoker
Lung Structure Lungs Diagram of a Smoker after Smoking Cancer Anatomy And Heart Drawing Images AFter Smoking Wee of a Weed Smoker
Lung Structure Lungs Diagram of a Smoker after Smoking Cancer Anatomy And Heart Drawing Images AFter Smoking Wee of a Weed Smoker
No comments:
Post a Comment