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The perineum in humans is the space between the anus and scrotum in the male or between the anus and vulva in the female. The perineum is the region of the body between the pubic symphysis and the coccyx, including the perineal body and surrounding structures. The perineal raphe is visible and pronounced to varying degrees. The perineum is an erogenous zone. This area is also known as the taint or gooch in American slang.
The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis.
The coccyx, commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates since Nacholapithecus, the coccyx is the remnant of a vestigial tail. In animals with bony tails, it is known as tailhead or dock, in bird anatomy as tailfan. It comprises three to five separate or fused coccygeal vertebrae below the sacrum, attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between the sacrum and the coccyx.
The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of the eye and that raise the eyelid. The nerve also contains fibers that innervate the intrinsic eye muscles that enable pupillary constriction and accommodation. The oculomotor nerve is derived from the basal plate of the embryonic midbrain. Cranial nerves IV and VI also participate in control of eye movement.
The levator scapulae is a slender skeletal muscle situated at the back and side of the neck. It originates from the transverse processes of the four uppermost cervical vertebrae; it inserts onto the upper portion of the medial border of the scapula. It is innervated by the cervical nerves C3-C4, and frequently also by the dorsal scapular nerve. As the Latin name suggests, its main function is to lift the scapula.
The coccygeus muscle or ischiococcygeus is a muscle of the pelvic floor, located posterior to levator ani and anterior to the sacrospinous ligament.
The external anal sphincter is an oval tube of skeletal muscle fibers. Distally, it is adherent to the skin surrounding the margin of the anus. It exhibits a resting state of tonical contraction.
The levator veli palatini is a muscle of the soft palate and pharynx. It is innervated by the vagus nerve via its pharyngeal plexus. During swallowing, it contracts, elevating the soft palate to help prevent food from entering the nasopharynx.
Proctalgia fugax, a variant of levator ani syndrome, is a severe, episodic pain in the regions of the rectum and anus. It can be caused by cramping of the levator ani muscle, particularly in the pubococcygeal part.
The perineal nerve is a nerve of the pelvis. It arises from the pudendal nerve in the pudendal canal. It gives superficial branches to the skin, and a deep branch to muscles. It supplies the skin and muscles of the perineum. Its latency is tested with electrodes.
The obturator fascia, or fascia of the internal obturator muscle, covers the pelvic surface of that muscle and is attached around the margin of its origin.
Ptosis, also known as blepharoptosis, is a drooping or falling of the upper eyelid. This condition is sometimes called "lazy eye," but that term normally refers to the condition amblyopia. If severe enough and left untreated, the drooping eyelid can cause other conditions, such as amblyopia or astigmatism, so it is especially important to treat the disorder in children before it can interfere with vision development.
The coccygeal plexus is a small nervous plexus upon the pelvic (anterior) surface of the coccygeus muscle.
The anal triangle is the posterior part of the perineum. It contains the anal canal.
The facial muscles are a group of striated skeletal muscles supplied by the facial nerve that, among other things, control facial expression. These muscles are also called mimetic muscles. They are only found in mammals, although they derive from neural crest cells found in all vertebrates. They are the only muscles that attach to the dermis.
Marcus Gunn phenomenon is an autosomal dominant condition with incomplete penetrance, in which nursing infants will have rhythmic upward jerking of their upper eyelid. This condition is characterized as a synkinesis: when two or more muscles that are independently innervated have either simultaneous or coordinated movements.
The pelvic fasciae are the fascia of the pelvis and can be divided into:
Levator ani syndrome is a condition characterized by burning pain or tenesmus of the rectal or perineal area, caused by spasm of the levator ani muscle. The genesis of the syndrome is unknown; however, inflammation of the arcus tendon is a possible cause of levator ani syndrome.
The deep branch of the perineal nerve is a nerve of the perineum. It is a branch of the perineal nerve, from the pudendal nerve. It supplies the superficial transverse perineal muscle, bulbospongiosus muscle, ischiocavernosus muscle, the bulb of penis, levator ani, and the external anal sphincter.
The vaginal support structures are those muscles, bones, ligaments, tendons, membranes and fascia, of the pelvic floor that maintain the position of the vagina within the pelvic cavity and allow the normal functioning of the vagina and other reproductive structures in the female. Defects or injuries to these support structures in the pelvic floor leads to pelvic organ prolapse. Anatomical and congenital variations of vaginal support structures can predispose a woman to further dysfunction and prolapse later in life. The urethra is part of the anterior wall of the vagina and damage to the support structures there can lead to incontinence and urinary retention.
References
- ↑ Essential Clinical Anatomy. K.L. Moore & A.M. Agur. Lippincott, 2 ed. 2002. Page 217
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