Penis of mammals
The penis of mammals ( Indo-European. Root, Latin penis "tail", cf. Greek πέος) is one of the outer male sexual organs of mammals , next to the scrotum . Other names for it are zagel (outdated) and limb or - for the erect ("excavated") state - the phallus . A term used mainly for dogs is tail . In technical terms, the penis is also called Membrum virile (Latin for male member). The penis is the male reproductive organ and also serves to excrete urine .
From an evolutionary point of view , the penis and the female clitoris (clitoris) go back to the same system , the genital hump .
The largest penis in mammals and in the animal kingdom is the blue whale, over two meters in length . The anatomical structure varies between the individual groups of animals.
anatomy
The penis contains three cavernous bodies . The two cavernous bodies at the top are called the penile cavernous bodies ( Corpora cavernosa penis ). They grow together median and are only separated from each other by a septum penis . Another cavernosa, the Harnröhrenschwellkörper ( corpus spongiosum ), extending at the bottom and continues in the glans as Eichelschwellkörper ( corpus spongiosum glandis ) continues. The penile part of the urethra runs in the erectile tissue of the urethra . During sexual arousal, the erectile tissue fill with blood, which makes the penis bigger and harder, resulting in an erection ("straightening", "stiffening"). The erectile tissue of the penis is primarily responsible for the stiffening.
The area of origin is called the penis root ( radix penis ). It consists of the paired initial section of the erectile tissue of the penis - so-called "penis thighs" ( crura penis ) - and the distended initial section of the urethral erectile tissue ( bulbus penis ). It is attached to the pelvis by muscles and ligaments . The subsequent penis ( corpus penis ) goes into the front end of the glans ( glans penis over). In mammals, with the exception of primates, the penis shaft is hidden under the skin in the gap between the thighs. In pair-toed ungulates, it is s-shaped ( flexura sigmoidea ).
The glans is shaped differently from animal species and is surrounded by the penile foreskin ( Praeputium penis ). This has a fold of skin on the underside of the penis, the foreskin frenulum ( frenulum praeputii ). In most mammals, the glans represents the free part of the penis ( pars libera penis ). This means that only the glans area is excavated from the foreskin during an erection and inserted into the female's vagina. In cats , the glans has strongly keratinized papillae ("penis spines"). They exert a strong stimulus during copulation in cats, which is also responsible for the ovulation triggered by the sexual act .
The glans and the inner sheet of the foreskin secrete cells and sebum , which together with remnants of urine form the smegma . On the underside of the penis which extends up to the scrotum penis seam .
The muscles of the penis are the bulbospongiosus muscle , the ischiocavernosus muscle, and the retractor penis muscle . They anchor it to the bony pelvis, strengthen the erection by constricting the drainage veins and compressing the erectile tissue at their base - especially during the final rigid-erection phase - and support the ejaculation of the sperm through rhythmic contractions.
The blood supply takes place via the three branches of the arteria penis ( arteria dorsalis penis , arteria profunda penis and arteria bulbi penis ).
The sensory innervation of the glans occurs via the dorsal penis nerve , which is also known as the "lust nerve ". The penis skin and the foreskin are innervated via the genital branch of the genitofemoral nerve. The erectile tissue and blood vessels are controlled by the autonomic nervous system. Their parasympathetic parts originate in the cross section of the spinal cord and run over the pelvic plexus ( plexus pelvinus ). They trigger the erection and are therefore also known as nervous .
Penis types
In principle, there are two types of construction:
- cavernous penis type and
- fibroelastic penis type.
With the cavernous penis type (for example horses or the penis of humans ) there is abundant erectile tissue.
In the fibroelastic penis (for example cloven-hoofed animals ) the erectile tissue is only slightly developed and interspersed with plenty of connective tissue . With this type of penis, the penis is s-shaped when at rest ( flexura sigmoidea ) and when erect it is stretched by the influx of blood. This makes the penis longer, but it hardly gets any thicker.
In some mammals (primates other than humans, predators , insectivores , bats ) there is a penis bone ( os penis or baculum ) or a cartilage tube in the limb . It is an ossification of the penis cavernous body ( corpus cavernosum penis ). Urethral and glans cavernous bodies, on the other hand, are well developed, which is why these species can be assigned to an intermediate type with features of both basic forms.
literature
- Uwe Gille: Male sexual organs. In: F.-V. Salomon et al. (Ed.): Anatomy for veterinary medicine . Enke, Stuttgart 2004, ISBN 3-8304-1007-7 , pp. 389-403.
- Klaus-Dieter Budras , Sabine Röck: Atlas of the anatomy of the horse: textbook for veterinarians and students. Schlütersche, 2004, ISBN 3-89993-002-9 , p. 84.
Individual evidence
- ^ Gregory B. Auffenberg, Brian T. Hellfand, Kevin T. McVary: Normal Erectile Physiology. In: Kevin T. McVary: Contemporary Treatment of Erectile Dysfunction. A clinical guide. Springer Science & Business Media, 2010, ISBN 978-1-60327-536-1 , p. 15.
