| Bulboid corpuscle | |
|---|---|
 End-bulb of Krause. | |
| Details | |
| Identifiers | |
| Latin | corpuscula bulboideum |
| FMA | 83603 |
| Anatomical terminology | |
The bulboid corpuscles (end-bulbs of Krause) are cutaneous receptors in the human body.
The end-bulbs of Krause were named after the German anatomist Wilhelm Krause (1833–1910). [1] [2]
The end-bulbs of Krause were thought to be thermoreceptors, sensing cold temperatures, but their function remained unknown. [3] Recently optogenetic studies revealed their role in sexual stimulation and mating behavior in mice:
"Optogenetic activation of male Krause corpuscle afferent terminals evoked penile erection, while genetic ablation of Krause corpuscles impaired intromission and ejaculation of males as well as reduced sexual receptivity of females. Thus, Krause corpuscles, which are particularly dense in the clitoris, are vibrotactile sensors crucial for normal sexual behavior." [4]
They are minute cylindrical or oval bodies, consisting of a capsule formed by the expansion of the connective-tissue sheath of a medullated fiber, and containing a soft semifluid core in which the axis-cylinder terminates either in a bulbous extremity or in a coiled-up plexiform mass.
End-bulbs are found in the conjunctiva of the eye (where they are spheroidal in shape in humans, but cylindrical in most other animals), in the mucous membrane of the lips and tongue, and in the epineurium of nerve trunks.
They are also found in the penis and the clitoris and have received the name of genital corpuscles; [5] in these situations they have a mulberry-like appearance, being constricted by connective-tissue septa into from two to six knob-like masses.[ citation needed ]
In the synovial membranes of certain joints, e. g., those of the fingers, rounded or oval end-bulbs occur, and are designated articular end-bulbs.
The clitoris is a female sex organ present in mammals, ostriches, and a limited number of other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora, above the opening of the urethra. Unlike the penis, the male homologue (equivalent) to the clitoris, it usually does not contain the distal portion of the urethra and is therefore not used for urination. In most species, the clitoris lacks any reproductive function. While few animals urinate through the clitoris or use it reproductively, the spotted hyena, which has an especially large clitoris, urinates, mates, and gives birth via the organ. Some other mammals, such as lemurs and spider monkeys, also have a large clitoris.
In male human anatomy, the glans penis, 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 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 G-spot, also called the Gräfenberg spot, is characterized as an erogenous area of the vagina that, when stimulated, may lead to strong sexual arousal, powerful orgasms and potential female ejaculation. It is typically reported to be located 5–8 cm (2–3 in) up the front (anterior) vaginal wall between the vaginal opening and the urethra and is a sensitive area that may be part of the female prostate.
The nipple is a raised region of tissue on the surface of the breast from which, in females, milk leaves the breast through the lactiferous ducts to feed an infant. The milk can flow through the nipple passively or it can be ejected by smooth muscle contractions that occur along with the ductal system. Male mammals also have nipples but without the same level of function, and often surrounded by body hair.
In the female human body, the clitoral hood is a fold of skin that surrounds and protects the glans of the clitoris; it also covers the external clitoral shaft, develops as part of the labia minora and is homologous with the foreskin in the male reproductive system. The clitoral hood is composed of mucocutaneous tissues; these tissues are between the mucous membrane and the skin, and they may have immunological importance because they may be a point of entry of mucosal vaccines. The clitoral hood is also important in the protection of the clitoral glans.
An erogenous zone is an area of the human body that has heightened sensitivity, the stimulation of which may generate a sexual response, such as relaxation, sexual fantasies, sexual arousal and orgasm.
A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, are sent to the central nervous system.
The female reproductive system is made up of the internal and external sex organs that function in the reproduction of new offspring. In humans, the female reproductive system is immature at birth and develops to maturity at puberty to be able to produce gametes, and to carry a fetus to full term. The internal sex organs are the vagina, uterus, fallopian tubes, and ovaries. The female reproductive tract includes the vagina, uterus, and fallopian tubes and is prone to infections. The vagina allows for sexual intercourse and childbirth, and is connected to the uterus at the cervix. The uterus or womb accommodates the embryo which develops into the fetus. The uterus also produces secretions which help the transit of sperm to the fallopian tubes, where sperm fertilize ova produced by the ovaries. The external sex organs are also known as the genitals and these are the organs of the vulva including the labia, clitoris, and vaginal opening.
Tactile corpuscles or Meissner's corpuscles are a type of mechanoreceptor discovered by anatomist Georg Meissner (1829–1905) and Rudolf Wagner. This corpuscle is a type of nerve ending in the skin that is responsible for sensitivity to pressure. In particular, they have their highest sensitivity when sensing vibrations between 10 and 50 hertz. They are rapidly adaptive receptors. They are most concentrated in thick hairless skin, especially at the finger pads.
The Pacinian corpuscle, lamellar corpuscle or Vater-Pacini corpuscle is one of the four major types of mechanoreceptors found in mammalian skin. This type of mechanoreceptor is found in both hairy, and hairless skin, viscera, joints, and attached to periosteum of bone, primarily responsible for sensitivity to vibration. Few of them are also sensitive to quasi-static or low frequency pressure stimulus. Most of them respond only to sudden disturbances and are especially sensitive to vibration of few hundreds of Hz. The vibrational role may be used for detecting surface texture, e.g., rough vs. smooth. Most of the Pacinian corpuscles act as rapidly adapting mechanoreceptors. Groups of corpuscles respond to pressure changes, e.g. on grasping or releasing an object.
The clitoral crura are two erectile tissue structures, which together form a V-shape. Crus is a Latin word that means "leg". Each "leg" of the V converges on the clitoral body. At each divergent point is a corpus cavernosum of clitoris. The crura are attached to the pubic arch, and are adjacent to the vestibular bulbs. The crura flank the urethra, urethral sponge, and vagina and extend back toward the pubis. Each clitoral crus connects to the rami of the pubis and the ischium.
In female anatomy, the vestibular bulbs, bulbs of the vestibule or clitoral bulbs are two elongated masses of erectile tissue typically described as being situated on either side of the vaginal opening. They are united to each other in front by a narrow median band. Some research indicates that they do not surround the vaginal opening, and are more closely related to the clitoris than to the vestibule.
The corpus cavernosum of clitoris is one of a pair of sponge-like regions of erectile tissue of the clitoris. It is made of a sponge-like tissue that fills with blood during clitoral erection. This is homologous to the corpus cavernosum penis. The term corpora cavernosa literally means "cave-like bodies".
The perineal membrane is an anatomical term for a fibrous membrane in the perineum. The term "inferior fascia of urogenital diaphragm", used in older texts, is considered equivalent to the perineal membrane.
The development of the reproductive system is the part of embryonic growth that results in the sex organs and contributes to sexual differentiation. Due to its large overlap with development of the urinary system, the two systems are typically described together as the urogenital or genitourinary system.
In human male anatomy, the radix or root of the penis is the internal and most proximal portion of the human penis that lies in the perineum. Unlike the pendulous body of the penis which is suspended from the pubic symphysis, the root is attached to the pubic arch of the pelvis and is not visible externally. It is triradiate in form, consisting of three masses of erectile tissue; the two diverging crura, one on either side, and the median bulb of the penis or urethral bulb. Approximately one third to one half of the penis is embedded in the pelvis and can be felt through the scrotum and in the perineum.
Clitoral erection is a physiological phenomenon where the clitoris becomes enlarged and firm.
In humans, the vulva consists of the external female sex organs. The vulva includes the mons pubis, labia majora, labia minora, clitoris, vestibular bulbs, vulval vestibule, urinary meatus, the vaginal opening, hymen, and Bartholin's and Skene's vestibular glands. The urinary meatus is also included as it opens into the vulval vestibule. Other features of the vulva include the pudendal cleft, sebaceous glands, the urogenital triangle, and pubic hair. The vulva includes the entrance to the vagina, which leads to the uterus, and provides a double layer of protection for this by the folds of the outer and inner labia. Pelvic floor muscles support the structures of the vulva. Other muscles of the urogenital triangle also give support.
The suspensory ligament of the clitoris is a fibrous band at the deep fascial level that extends from the pubic symphysis to the deep fascia of the clitoris, anchoring the clitoris to the pubic symphysis. By virtue of this connection, the pubic symphysis supports the clitoris.
The clitoris is a female sex organ present in mammals, ostriches and a limited number of other animals.
This article incorporates text in the public domain from page 1060 of the 20th edition of Gray's Anatomy (1918)
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