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Ninety-three hearts of birds
belonging to five species representing the Anseriformes were used in the study.
Morphological and imaging examination was conducted on the material using an X-ray apparatus (RTG). In most species each free margin of the cusp of the aortic valve had the nodules of the semilunar cusp. It can be assumed
that the structures mentioned above are the evidence of a specific adaptation
of birds to their lifestyle – diving. A lot of terms to describe the aortic valve
and its adjacent structures were suggested. Morphological and X-ray research
will contribute to a better understanding of the functioning of the aortic valve
of sea birds able to dive very well. The study will also let us relate basic
ecological examination with clinical sciences.
Ninety-three hearts of birds belonging to five species representing the Anseriformes were used in the study. Morphological and imaging examination was conducted on the material using an X-ray apparatus (RTG). In most species each free margin of the cusp of the aortic valve had the nodules of the semilunar cusp. It can be assumed that the structures mentioned above are the evidence of a specific adaptation of birds to their lifestyle – diving. A lot of terms to describe the aortic valve and its adjacent structures were suggested. Morphological and X-ray research will contribute to a better understanding of the functioning of the aortic valve of sea birds able to dive very well. The study will also let us relate basic ecological examination with clinical sciences.
Key words: .
Many scientists have been interested in the structure of hearts of birds for a long time (11). They were also interested in the adaptation of the cardio-vascular system of this group of vertebrates to particular lifestyles [10,19]. Writings concerning the relation of anatomical structure of this organ to adaptation to specific living conditions of birds (for example deep diving) are not found frequently. Morphology of hearts of penguins, for example, seemed to be related to diving efficiency of the birds . So far there have been only a few publications concerning varieties and types of particular heart structures such as the aortic valve, the pulmonary valve which can be related to various living conditions of the animals [2,3]. There are not also many clinical elaborations which in the future will allow a better diagnostics, for example the imaging one, of diseases of the cardio-vascular system in various species of sea birds both living in their natural environment, living in captivity and domestic ones [3,18,13]. There is a big demand for research of this type.
The aim of the research is to describe the aortic valve and its adjacent structures of selected species of sea birds (ducks). Some terms characterizing the aortic valve were suggested and there were also attempts to show the validity of using imaging connected with morphological examinations.
MATERIAL AND METHODS
The research was conducted on 93 hearts of birds of the following orders of Anseriformes: Long-tailed duck Clangula hyemalis – 18 hearts; Black scoter, Melanitta nigra – 19 hearts; Velvet scoter, Melanitta fusca – 23 hearts; Tufted duck, Aythya fuligula – 18 hearts; Greater scaup, Aythya marila – 15 hearts.
The research material is a part of a collection of preparations of exhibits from Department of Morphological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences – SGGW. The described organs were taken from adult individuals.
The material was kept in a 10% solution of formaldehyde and ethanol added to it. Each heart was irrigated in running water and dried using filtering paper and a mechanical aspirator. Such prepared hearts' cavities were injected through the right brachiocephalic trunk with a radiological contrast agent Ultravist 320® 76% . The imaging was conducted with the use of an X-ray apparatus GE prestige II (43 KV; 7.43 mAs 29.3 ms) in AP and lateral projections . The X-ray research (RTG) was conducted in X-ray Laboratory, Small Animal Clinic, Department of Clinical Science, Faculty of Veterinary Medicine, Warsaw University of Life Sciences – SGGW.
Such a prepared heart was cut from the left atrium to the apex of the heart along the left margin of the heart about 0.5 cm backwards which allowed to evaluate the aortic valve and its adjacent structures (the opening of the aorta, the openings of the coronary arteries).
The morphological structure of the aortic valve was described using a camera-linked (Ecleris HaloLux 150) surgical microscope (Sony HDR-SR 11E) (3).
RESULTS AND DISCUSSION
The conducted intra- species research of the aortic valve and its adjacent structures did not show any significant differences in a macroscopic structure as far as sexual dimorphism was concerned. Therefore, the achieved results were not divided for both sexes.
All examined sea birds' left opening of the aorta, similar to mammals, was situated in the left ventricular outflow tract – preceded by the reduced left arterial cone. It was blocked by three semilunar cusps which formed the aortic valve [1,4,9,14,15]. A lot of precise terms characterising the aortic valve and the structural elements located nearby had been introduced earlier as far as humans were concerned . The authors of the elaboration mentioned above distinguished, for example, fibrous structures connected with the fibrous ring – the proximal fibrous structures, locating it in the heart muscle as well as additional fibrous structures – surrounding structures attached to the aortic root.
In the studied material the skeleton of the aortic valve was similar to the shape of a crown. At the base of the aorta it had the fibrous ring in the wall of the root of the aorta – the aortic annulus fibrosus – Annulus fibrosus aortae (a suggested term concerning birds), which ran towards the commissures: left, right, anterior and formed a support for the valvular apparatus – the crown (the character of the structure will be examined histologically in the future.) (Fig. 1.). The structure was most developed in Long-tailed ducks, Greater scaups and Velvet scoters. The birds dive best of all the studied species of birds, for instance Long-tailed ducks can dive at the depth of 60 metres and stay underwater for about 3 minutes. Whereas diving depth of Greater scaups and Velvet scoters is about 6 metres and in some cases it can reach 30 metres . It can be the example of the adaptation to long-lasting diving . It is proved by an earlier suggestion that differences in the heart morphology of birds can be connected with the time and depth of diving .
|Fig. 1. Fragment of the aortic valve.
A – Long-tailed duck, B – Tufted duck (top view): 1 – right commissure (fragment of the crus of the fibrous ring of the aorta); 2 – posterior commissure (fragment of the crus of the fibrous ring of the aorta); 3 – left commissure (fragment of the crus of the fibrous ring of the aorta); 4 – left semilunar cusp; 5 – right ventral semilunar cusp; 6 – right dorsal semilunar cusp; 7 – left coronary artery; 8 – right coronary artery
All examined sea birds had the nodules of the semilunar cusps in the central part of the free margin of each cusp. Long-tailed ducks had the biggest nodules which were dome-like shaped. Other studied species of birds had smaller nodules. It can be assumed that all adult diving sea birds from the Anseriformes order have the nodule of the semilunar cusp, for which the following terms are suggested: the nodule of the left semilunar cusp nodulus valvulae semilunaris sinistri, the ventral nodule of the right semilunar cusp nodulus valvulae semilunaris dextri ventralis, the dorsal nodule of the right semilunar cusp nodulus valvulae semilunaris dextri dorsalis (Fig. 2). The structures mentioned above were also observed during our private research as far as birds of prey were concerned.
|Fig. 2. Fragment of the aortic valve.
A – Long-tailed duck (top view), B – Tufted duck (cut and half open – posterio- top view): 1 – right abdominal nodule of the semilunar cusp; 2 – right ventral semilunar cusp; 3 – right dorsal semilunar cusp; 4 – posterior commissure
Sea birds with no division into sexes presented two basic types of location of the openings of the coronary arteries: I type – at the level of the free margin of the cusp (4% of the studied hearts: Long-tailed duck – 0.5%, Black scoter – 0.5%, Velvet scoter – 1%, Tufted duck – 1%, Greater scaup – 1%); II type – the openings of the left coronary artery situated above the free margin of the cusp, openings of the right coronary artery located below the free margin of the cusp (96% of the examined hearts). Chickens have three types of the location of the openings of the coronary arteries: I type – at the level of the free margin of the cusp; II type: below the free margin of the cusp within the aortic sinus; III type – above the free margin of the cusp . The authors also stated that single openings of the coronary arteries of type II were found within the sinus of the right dorsal aorta in this species. Additional openings were not observed in the research in sea birds. A similar study concerning the location of the openings of the coronary arteries were also conducted in humans using morphological and imaging methods. Analyses showed that regular coronary vessels which had a separate outlet in the sinuses of the aorta were the most frequent. For that reason they do not have any negative influence on vascularisation of the heart [8,14,17].
Radiograms of the examined hearts clearly show the following basic structures: the right and left ventricle, the right atrioventricular valve, the aortic valve (Fig. 3). The research of this type with the use of an X-ray apparatus (RTG) and Computed Tomography (CT) had already been conducted on hearts of Long-tailed ducks . The research showed that the method will be very useful in the future clinical evaluation in various orders of birds living both in their natural environment and in captivity.
|Fig. 3. Black scoter's heart in an X-ray image (digital image – AP view): 1 – right ventricle; 2 – right atrioventricular valve; 3 – aortic valve; 4 – pulmonary trunk; 5 – left ventricle; 6 – apex of heart; 7 – interventricular septum|
The characteristic structure of the aortic valve of sea birds, including the existence of the nodules
of the semilunar cusp as well as the exceptional structure of the fibrous ring
of the aorta makes the valvular apparatus extremely tight. Such an anatomical
structure allows birds to occupy various ecological niches. Gaining food at various
depths and at various times of staying underwater may be connected with a specific
structure of the cardio-vascular system of the examined species of birds [5,16]. The conducted morphological and imaging research aims at getting more details of the essence and a specific character of the aortic valve of sea birds. In
the future it will allow to connect basic examinations with cardiology and ecology
of this group of birds.
The skeleton of the aortic valve of sea birds was crown-shaped.
In all the material there were the nodules of the semilunar cusps in the central part of the free margin of the cusp.
The studied population of birds had two basic types of location of the openings of the coronary arteries.
Imaging techniques (RTG) can be easily applied while analysing such basic structures of the hearts of birds as ventricles, atria and valves.
I would like to thank my tutor Prof. H. Kobryń for help and valuable
advice. I would also like to thank D. Krasuska, A. Nowicka, K. Urbańska and doctors:
M. Siedlicki, K. Siewruk, T. Narojek from Faculty of Veterinary Medicine, Warsaw
University of Life Sciences – SGGW for their patience, understanding and help
in RTG preparation.
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Accepted for print: 19.10.2009
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