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Cloaca of a red-tailed hawk. A cloaca (/ k l oʊ ˈ eɪ k ə / ⓘ kloh-AY-kə), pl.: cloacae (/ k l oʊ ˈ eɪ s i / kloh-AY-see or / k l oʊ ˈ eɪ k i / kloh-AY-kee), or vent, is the rear orifice that serves as the only opening for the digestive (), reproductive, and urinary tracts (if present) of many vertebrate animals.
In order for birds to produce sound, they use an organ located above the lungs called the syrinx, which is composed of tracheal rings, syringeal muscles, Tympaniform membrane, and internal bony structures that contribute to the production of sound. Air then passes through this organ, resulting in the vocalization of birds.
Alternatively, for the vast majority of birds—a group comprising nearly 10,000 species [26] —sperm transfer occurs by cloacal contact between the male and female, in a maneuver known as the "cloacal kiss". [25] Birds are one of the only groups which reproduce through internal fertilization but have repeatedly lost the intromittent organ. [27]
Caruncles in birds include those found on the face, wattles, dewlaps, snoods, and earlobes. Wattles are generally paired structures but may occur as a single structure when it is sometimes known as a dewlap. Wattles are frequently organs of sexual dimorphism. In some birds, caruncles are erectile tissue and may or may not have a feather covering.
Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. [1]
Most mammals possess a vomeronasal organ that is involved in pheromone detection, including sex pheromones. [19] Despite the fact that humans do not possess this organ, adult humans appear to be sensitive to certain mammalian pheromones that putative pheromone receptor proteins in the olfactory epithelium are capable of detecting.
A penis (/ ˈ p iː n ɪ s /; pl.: penises or penes) is a male sex organ that is used to inseminate female or hermaphrodite animals during copulation. [1] [2] Such organs occur in both vertebrates and invertebrates, including humans, but not in all male animals. The term penis applies to many intromittent organs, but not to all.
The hemipenis is the intromittent organ of Squamata, [4] which is the second largest order of vertebrates with over 9,000 species distributed around the world. They differ from the intromittent organs of most other amniotes such as mammals, archosaurs and turtles that have a single genital tubercle, as squamates have the paired genitalia remaining separate. [5]