Many mammalian species have developed keratinized penile spines along the glans and/or shaft, which may be involved in sexual selection. These spines have been described as being simple, single-pointed structures (macaques) or complex with two or three points per spine (strepsirrhines). [1] Penile spine morphology may be related to mating system. [2] [3]
Felines, especially domestic cats, are well known for having penile spines. Upon withdrawal of a cat's penis, the spines rake the walls of the female's vagina, which may serve as a trigger for ovulation. [4] [5] Many other felid species have penile spines, but they are relatively small in jaguars and pumas, and do not occur in margays. [6]
Penile spines in chimpanzees and mice are small surface projections made by the piling up of keratinized cell layers in the outermost skin surface. [7] [8] They occur in wombats, [9] koalas, [10] spotted hyenas, [11] [12] fossas, [13] echidnas, [14] primates, [15] [16] [17] bats, [18] and several rodent species. [19]
Penile spines are often found in primate species that form copulatory plugs after mating. [20] In galagos, penile spines may form a "genital lock" during copulation. [21]
In contrast to chimpanzees, a common morphological variant found in humans called hirsuties coronae glandis, or pearly penile papules, are substantially larger, appear to be an outpocketing of both surface and underlying connective tissue layers, and lack the rich innervation seen in other animals. [22] [23] These are sometimes described as vestigial remnants of penile spines. [7] However, the relationship between the structures is still uncertain. [24]
When the hominin lineage split into the genera Homo and Pan, a regulatory DNA sequence associated with the formation of small keratinized penile spines was lost in the Homo lineage. This simplification of penis anatomy may be associated with the sexual habits of humans. [25] In some species which retain full expression, penile spines contribute to increased sexual sensation and quicker orgasms. [26] An hCONDEL (highly conserved region of DNA that contains deletions in humans) located near the locus of the androgen receptor gene may be responsible for the loss of penile spines in humans. [25]
The penises of some bird species feature spines and brush-like filaments. [27]
In male human anatomy, the glans penis or penile glans, commonly referred to as the glans, is the bulbous structure at the distal end of the human penis that is the human male's most sensitive erogenous zone and primary anatomical source of sexual pleasure. The glans penis is present in the male reproductive organs of humans and most other mammals where it may appear smooth, spiny, elongated or divided. It is externally lined with mucosal tissue, which creates a smooth texture and glossy appearance. In humans, the glans is located over the distal ends of the corpora cavernosa and is a continuation of the corpus spongiosum of the penis. At the summit appears the urinary meatus and at the base forms the corona glandis. An elastic band of tissue, known as the frenulum, runs on its ventral surface. In men who are not circumcised, it is completely or partially covered by a fold of skin called the foreskin. In adults, the foreskin can generally be retracted over and past the glans manually or sometimes automatically during an erection.
The bulbourethral glands or Cowper's glands are two small exocrine and accessory glands in the reproductive system of many male mammals. They are homologous to Bartholin's glands in females. The bulbourethral glands are responsible for producing a pre-ejaculate fluid called Cowper's fluid, which is secreted during sexual arousal, neutralizing the acidity of the urethra in preparation for the passage of sperm cells. The paired glands are found adjacent to the urethra just below the prostate, seen best by screening (medicine) MRI as a tool in preventative healthcare in males. Screening MRI may be performed when there is a positive prostate-specific antigen on basic laboratory tests. Prostate cancer is the second-most common cause of cancer-related mortality in males in the USA.
The baculum, also known as the penis bone, penile bone, os penis, os genitale, or os priapi, is a bone in the penis of many placental mammals. It is absent from the human penis, but present in the penises of some primates, such as the gorilla and the chimpanzee. The baculum arises from primordial cells in soft tissues of the penis, and its formation is largely influenced by androgens. The bone lies above the urethra, and it aids sexual reproduction by maintaining stiffness during sexual penetration. The homologue to the baculum in female mammals is the baubellum, a bone in the clitoris.
Animal sexual behaviour takes many different forms, including within the same species. Common mating or reproductively motivated systems include monogamy, polygyny, polyandry, polygamy and promiscuity. Other sexual behaviour may be reproductively motivated or non-reproductively motivated.
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. For internal fertilization to happen there needs to be a method for the male to introduce the sperm into the female's reproductive tract.
Pearly penile papules are benign, small bumps or spots on the human penis. They vary in size from 1–4 mm, are pearly or flesh-colored, smooth and dome-topped or filiform, and appear in one or, several rows around the corona, the ridge of the head of the penis and sometimes on the penile shaft. They are painless, non-cancerous and not harmful. The medical condition of having such papules is called hirsutoid papillomatosis or hirsuties papillaris coronae glandis.
A pseudo-penis is any structure found on an animal that, while superficially appearing to be a penis, is derived from a different developmental path.
The brown greater galago, also known as the large-eared greater galago or thick-tailed galago, is a nocturnal primate, the largest in the family of galagos. As opposed to smaller galago species it would climb, walk or run rather than leap.
The northern greater galago, also known as Garnett's greater galago, Garnett's galago, or the small-eared greater galago, is a nocturnal, arboreal primate endemic to Africa.
In human anatomy, the penis is an external male sex organ that additionally serves as the urinary duct. The main parts are the root, body, the epithelium of the penis including the shaft skin, and the foreskin covering the glans. The body of the penis is made up of three columns of tissue: two corpora cavernosa on the dorsal side and corpus spongiosum between them on the ventral side. The human male urethra passes through the prostate gland, where it is joined by the ejaculatory duct, and then through the penis. The urethra traverses the corpus spongiosum, and its opening, the meatus, lies on the tip of the glans. It is a passage both for urination and ejaculation of semen.
The corona of glans penis or penis crown refers to the rounded projecting border or flare that forms at the base of the glans in human males. The corona overhangs a mucosal surface, known as the neck of the penis, which separates the shaft and the glans. The deep retro-glandular coronal sulcus forms between the corona and the neck of the penis. The two sides of the corona merge on the ventral midline forming the septum glandis. The circumference of the corona is richly innervated and is described as a highly erogenous area of the glans.
In many animals, a penis is the main male sexual organ used to inseminate females during copulation. Such organs occur in both vertebrates and invertebrates, but males do not bear a penis in every animal species.
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring.
A mating plug, also known as a copulation plug, sperm plug, vaginal plug, or sphragis, is a gelatinous secretion used in the mating of some species. It is deposited by a male into a female genital tract, such as the vagina, and later hardens into a plug or glues the tract together. While females can expel the plugs afterwards, the male's sperm still gets a time advantage in getting to the egg, which is often the deciding factor in fertilization.
An intromittent organ is any external organ of a male organism that is specialized to deliver sperm during copulation. Intromittent organs are found most often in terrestrial species, as most non-mammalian aquatic species fertilize their eggs externally, although there are exceptions. For many species in the animal kingdom, the male intromittent organ is a hallmark characteristic of internal fertilization.
Most mammals are viviparous, giving birth to live young. However, the five species of monotreme, the platypuses and the echidnas, lay eggs. The monotremes have a sex determination system different from that of most other mammals. In particular, the sex chromosomes of a platypus are more like those of a chicken than those of a therian mammal.
Animal non-reproductive sexual behavior encompasses sexual activities that non-human animals participate in which do not lead to the reproduction of the species. Although procreation continues to be the primary explanation for sexual behavior in animals, recent observations on animal behavior have given alternative reasons for the engagement in sexual activities by animals. Animals have been observed to engage in sex for social interaction bonding, exchange for significant materials, affection, mentorship pairings, sexual enjoyment, or as demonstration of social rank. Observed non-procreative sexual activities include non-copulatory mounting, oral sex, genital stimulation, anal stimulation, interspecies mating, and acts of affection, although it is doubted that they have done this since the beginning of their existence. There have also been observations of sex with cub participants, same-sex sexual interaction, as well as sex with dead animals.
Sperm competition is a form of post-copulatory sexual selection whereby male sperm simultaneously physically compete to fertilize a single ovum. Sperm competition occurs between sperm from two or more rival males when they make an attempt to fertilize a female within a sufficiently short period of time. This results primarily as a consequence of polyandrous mating systems, or due to extra-pair copulations of females, which increases the chance of cuckoldry, in which the male mate raises a child that is not genetically related to him. Sperm competition among males has resulted in numerous physiological and psychological adaptations, including the relative size of testes, the size of the sperm midpiece, prudent sperm allocation, and behaviors relating to sexual coercion, however this is not without consequences: the production of large amounts of sperm is costly and therefore, researchers have predicted that males will produce larger amounts of semen when there is a perceived or known increase in sperm competition risk.
In zoology, copulation is animal sexual behavior in which a male introduces sperm into the female's body, especially directly into her reproductive tract. This is an aspect of mating. Many animals that live in water use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates occurs via cloacal copulation, known as cloacal kiss, while most mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.
The clitoris is a female sex organ present in mammals, ostriches and other amniotes.
spines.
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