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Pigeon Cardiovascular and Respiratory Systems: Photos and Information

posted Oct 24, 2010, 9:10 AM by Nicole Wierzbinski   [ updated Dec 17, 2010, 6:45 AM ]
This page illustrates the dissection of two adult pigeons. The organs and structures within the cardiovascular and respiratory systems were the main focus of our examination. Photos we took during the dissection, as well as descriptions of these different organs and structures, are explained below. These birds were injected with dye to better reveal their arteries and arterioles (dyed red) & veins and venules (dyed blue), prior to purchasing the specimens. Also, at the bottom of the page you have the option to view an 8-minute dissection tutorial geared toward high school students.
All photos taken were posted to Picasa, an online photo-sharing website (no log-in required):
Photos were formatted in Photosynth to create a "3D" image compilation:
(Above is all 248 photos synthed together, highlights included) 
(Above is the second pigeon dissected, 92% synthy)
(Below are the trachea, heart, and lungs only) 
   Photos were also added to and structures were labeled 
   using Flickr, another photo-sharing website compatible
   for use with Macs (click on the photo on the right to
   be transferred to the site):
Avian Cardiovascular System:

The cardiovas
cular system is composed of the heart and vessels within the circulatory system. Pigeons have very efficient cardiovascular systems that allow them to meet the high metabolic demands of flight. This system carries oxygen to, and carbon dioxide away from the tissues, carries nutrients and hormones, removes metabolic wastes, and is also necessary for the regulation of body temperature in these animals.
Pigeon Circulatory System:

Heart: Pigeons have a four chamber heart consisting of a Right and Left Atrium and a Right and Left Ventricle.  Pigeons have bigger hearts than humans relative to their size.  It function much like human hearts, it receives blood from the body via veins that enters the right atrium, passes to the right ventricle which pushes it into the lungs were it gets oxidized.  From the lungs it travels to the left atrium and then leaves the heart and travels through the arteries to the body from the left ventricle.

- Arteries carry blood away from the heart and toward the body tissues
- Arterioles direct blood where it is needed within the body; more blood is sent to active tissues and
    organs, and less blood is sent to less active tissues and organs. This is accomplished
    through vasodilation and vasoconstriction.
- Veins carry blood back to the heart from the body tissues
- Venules are small veins that also conduct blood back to the heart from the body tissues
- Capillaries are responsible for the exchange of nutrients, gases, and waste products between the
    blood and body cells
Major Arteries:
- Carotids: conducts blood to the head and brain
- Brachials: carry blood to the wings
- Pectorals: carry blood to the pectoralis, or flight, muscles 
Systemic arch: also known as the aorta; conducts blood to all areas of the body except the lungs
- Pulmonary arteries: deliver blood to the lungs
- Coeliac: a major branch of the aorta; delivers blood to organs and tissues in the upper
    abdominal region
- Renal arteries: conduct blood to the kidneys and renal system 
- Femoral arteries: deliver blood to the legs
- Caudal: carries blood to the tail
Posterior mesenteric: brings blood to organs and tissues in the lower abdominal area       
                                        Arteries                                                                    Veins
Major Veins:
- Jugular anastomosis: allows blood to flow from the right to left sides of the body when the head is
    turned to one side due to constriction of jugular veins
- Jugulars: carry blood away from the head and neck 
- Brachials: carry blood away from the wings
- Pectorals: drain the pectoral muscles and anterior thorax
- Superior vena cava (precava): carry blood from the anterior regions of the body
- Inferior vena cava (postcava): take blood away from the posterior region of the bird
- Hepatic vein empties blood from the liver
- Hepatic portal: takes blood away from the digestive system
- Coccygeomesenteric: empties the posterior digestive system and the hepatic portal vein
- Femorals: carry blood away from the legs
- Sciatic veins: drain the thigh area of blood 
- Renal and renal portal veins: take blood away from the kidneys

Avian Respiratory System:

Trachea:  Air gets inhaled through the mouth or nares, travels through the pharynx, and into the trachea.  Since a pigeon’s trachea is larger than that of mammals (thus, more trachea dead-space), it needs to compensate by ventilating at a slower rate and increased depth. 

Syrinx:  Also known as the “voicebox”, the syrinx is where the trachea forks into two primary bronchi.  Unlike mammals, the syrinx produces sound by vibrating the syrinx walls.

Bronchi:  The bronchus splits into two mesobronchi (primary) at the syrinx.  The primary bronchi lead into the lungs and splits off into smaller tubes called ventrobronchi (secondary).  The ventrobronchi bring air into the abdominal air sacs and some channel air to the anterior air sacs.  The ventrobronchi lead into a network of smaller parabronchi (tertiary).  Parabronchi contain hundreds of tiny branching air capillaries that are responsible for gas exchange between the ventilation system and the blood that brings delivers oxygen to the body cells for respiration.

Lungs: There is no mixture

of oxygen rich and oxygen poor air like mammalian lungs.  Partial pressure within the lungs is the same as the environment.  Air flows through the lungs during inhalation and exhalation where it passes through parabronchi into atria.  Within the atria are capillaries where oxygen and carbondioxide are exchanged through diffusion.
Air sacs: Instead of a diaphragm pigeons have 6 air sacs: the Cervical, Interclavicular, Anterior Thoracic, Posterior Thoracic, Abdominal, and Humeral Sac.  The air sacs extend into the bone structure making respiratory infections able to spread to the bones.  When the heart pushes out it puts pressure on the sternum, this causes a negative pressure in the air sacs causing air to enter the respiratory system.    Each lung has several air sacs attached to it. No actual gas exchange occurs in the air sacs. Instead they draw larger amounts of air through the lungs than the lungs could unaided and allow a greater amount of gas exchange to occur.
(Diagram on the right: http://www.smithlifescience.com/ ComparativeAnatomy.htm)

A Human Comparison: A bird’s respiratory system is more efficient than human’s part of the reason is because while humans only have one pulmonary vein while birds have four.  This makes birds more vulnerable to pollutions in the air which is why Teflon fumes in the air is toxic to birds but the same concentrations are harmless to humans.

Interesting Facts:
  • Lack diaphragm, instead use air sacs within body cavity as a bellow
  • Uni-directional flow is still maintained even though air passes through parabronchi during inhalation and exhalation
  • Avian hearts are typically larger relative to body size than mammals due to high metabolic requirements of flight, generating a relatively greater amount of blood flow
  •  Bar-headed Geese have adapted for long duration, high altitude flights. Due to hypoxic environment they evolved higher density capillaries in muscle fibers as well as having mitochondria closer to the sarcolemma, adjacent to the capillaries, for greater amount of O2 exchange to combat the hypoxia of high altitude
  1. Ritchison, G. Avian Circulatory System. Department of Ornithology, Eastern Kentucky Univerity. http://people.eku.edu/ritchisong/birdcirculatory.html
  2. Ritchison, G. Avian Respiration. Department of Ornithology, Eastern Kentucky Univerity. http://people.eku.edu/ritchisong/birdrespiration.html
  3. Sherwood, D. (2000) An Illustrated Dissection Guide to the Pigeon. RANACO: Tucson, AZ