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The anatomy of bird's respiratory system, showing the relationships of the trachea, primary and intra-pulmonary bronchi, the dorso- and ventro-bronchi, with the parabronchi running between the two. The posterior and anterior air sacs are also indicated, but not to scale. Inhalation–exhalation cycle in birds.
Cloaca. A cloaca (/ kloʊˈeɪkə / ⓘ kloh-AY-kə), pl.: cloacae (/ kloʊˈeɪsi / kloh-AY-see or / kloʊˈeɪki / kloh-AY-kee), is the rear orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, and a few mammals (monotremes ...
Birds are a group of warm-blooded vertebrates constituting the class Aves (/ ˈeɪviːz /), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.
Anatomy of a male budgerigar Wild budgerigars average 18 cm (7 in) long, [ 6 ] weigh 30–40 grams (1.1–1.4 oz), 30 cm (12 in) in wingspan, and display a light green body colour (abdomen and rumps), while their mantles (back and wing coverts) display pitch-black mantle markings (blackish in fledglings and immatures) edged in clear yellow ...
In birds, the bursa of Fabricius (Latin: bursa cloacalis or bursa Fabricii) is the site of hematopoiesis. It is a specialized organ that, as first demonstrated by Bruce Glick and later by Max Dale Cooper and Robert Good, is necessary for B cell (part of the immune system) development in birds. Mammals generally do not have an equivalent organ ...
The chorion is the outermost fetal membrane around the embryo in mammals, birds and reptiles . It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida (in mammals), known as the vitelline membrane in other animals. In insects, it is developed by the follicle cells while the egg is in the ovary. [1]
The oviduct in vertebrates is the passageway from an ovary. In human females, this is more usually known as the fallopian tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, or will degenerate in the body. Normally, these are paired structures, but in birds and some cartilaginous ...
Reproductive isolation between species appears, in certain cases, a long time after fertilization and the formation of the zygote, as happens – for example – in the twin species Drosophila pavani and D. gaucha. The hybrids between both species are not sterile, in the sense that they produce viable gametes, ovules and spermatozoa.