Puborectalis :
41-405: 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. It is attached to the inner surface of each side of the lesser pelvis , and these unite to form the greater part of the pelvic floor . The coccygeus muscle completes the pelvic floor, which is also called
82-406: A median fibrous ridge called the anococcygeal body or raphe, which extends between the coccyx and the margin of the anus . The middle fibers are inserted into the side of the rectum , blending with the fibers of the sphincter muscles; lastly in the male, the anterior fibers descend upon the side of the prostate to unite beneath it with the muscle of the opposite side, joining with the fibers of
123-454: A rhythmic fashion for the whole life of the organism. Hence it has special features. There are three types of muscle tissue in invertebrates that are based on their pattern of striation : transversely striated, obliquely striated, and smooth muscle. In arthropods there is no smooth muscle. The transversely striated type is the most similar to the skeletal muscle in vertebrates. Obturator fascia The obturator fascia , or fascia of
164-413: A series of voluntary contractions of all the perineal muscles . Such movement is done in an effort to strengthen all the striated muscles in the perineum's area. They are often referred to simply as "kegels", named after their founder, Dr. Arnold Kegel . These exercises also serve to contract, among others, the ischiocavernosus , bulbospongiosus , and cremaster muscle in men, as voluntary contraction of
205-523: Is about 1.06 kg/liter. This can be contrasted with the density of adipose tissue (fat), which is 0.9196 kg/liter. This makes muscle tissue approximately 15% denser than fat tissue. Skeletal muscle is a highly oxygen-consuming tissue, and oxidative DNA damage that is induced by reactive oxygen species tends to accumulate with age . The oxidative DNA damage 8-OHdG accumulates in heart and skeletal muscle of both mouse and rat with age. Also, DNA double-strand breaks accumulate with age in
246-436: Is arranged in regular, parallel bundles of myofibrils , which contain many contractile units known as sarcomeres , which give the tissue its striated (striped) appearance. Skeletal muscle is voluntary muscle, anchored by tendons or sometimes by aponeuroses to bones , and is used to effect skeletal movement such as locomotion and to maintain posture . Postural control is generally maintained as an unconscious reflex, but
287-456: Is divided along the embryo 's length into somites , corresponding to the segmentation of the body (most obviously seen in the vertebral column . Each somite has three divisions, sclerotome (which forms vertebrae ), dermatome (which forms skin), and myotome (which forms muscle). The myotome is divided into two sections, the epimere and hypomere, which form epaxial and hypaxial muscles , respectively. The only epaxial muscles in humans are
328-408: Is found within the walls of blood vessels (such smooth muscle specifically being termed vascular smooth muscle ) such as in the tunica media layer of the large ( aorta ) and small arteries , arterioles and veins . Smooth muscle is also found in lymphatic vessels, the urinary bladder , uterus (termed uterine smooth muscle ), male and female reproductive tracts , the gastrointestinal tract ,
369-403: Is involuntary, striated muscle that is found in the walls and the histological foundation of the heart , specifically the myocardium. The cardiac muscle cells , (also called cardiomyocytes or myocardiocytes), predominantly contain only one nucleus, although populations with two to four nuclei do exist. The myocardium is the muscle tissue of the heart and forms a thick middle layer between
410-409: Is no smooth muscle. The transversely striated type is the most similar to the skeletal muscle in vertebrates. Vertebrate skeletal muscle tissue is an elongated, striated muscle tissue, with the fibres ranging from 3-8 micrometers in width and from 18 to 200 micrometers in breadth. In the uterine wall, during pregnancy, they enlarge in length from 70 to 500 micrometers. Skeletal striated muscle tissue
451-454: Is non-striated and involuntary. Smooth muscle is found within the walls of organs and structures such as the esophagus , stomach , intestines , bronchi , uterus , urethra , bladder , blood vessels , and the arrector pili in the skin that control the erection of body hair. Skeletal muscle is broadly classified into two fiber types: type I (slow-twitch) and type II (fast-twitch). The density of mammalian skeletal muscle tissue
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#1732801712297492-399: The erector spinae and small intervertebral muscles, and are innervated by the dorsal rami of the spinal nerves . All other muscles, including those of the limbs are hypaxial, and innervated by the ventral rami of the spinal nerves. During development, myoblasts (muscle progenitor cells) either remain in the somite to form muscles associated with the vertebral column or migrate out into
533-418: The external anal sphincter and transverse perineal muscles , at the central tendinous point of the perineum . The anterior portion is occasionally separated from the rest of the muscle by connective tissue. From this circumstance, as well as from its peculiar relation with the prostate , which it supports as in a sling, it has been described as a distinct muscle, under the name of levator prostatæ . In
574-405: The hip bone ) and from the posterior part of the tendinous arch of the obturator fascia , and is attached to the coccyx and anococcygeal body ; it is usually thin, and may be absent, or be largely replaced by fibrous tissue. An accessory slip at its posterior part is sometimes named the iliosacralis . The pubococcygeus muscle has medial fibres forming the pubovaginalis in the female, and
615-402: The internal obturator muscle , covers the pelvic surface of that muscle and is attached around the margin of its origin. Above, it is loosely connected to the back part of the arcuate line , and here it is continuous with the iliac fascia . In front of this, as it follows the line of origin of the internal obturator , it gradually separates from the iliac fascia and the continuity between
656-440: The neurotransmitter acetylcholine . Smooth muscle is found in almost all organ systems such as hollow organs including the stomach , and bladder ; in tubular structures such as blood and lymph vessels , and bile ducts ; in sphincters such as in the uterus, and the eye. In addition, it plays an important role in the ducts of exocrine glands. It fulfills various tasks such as sealing orifices (e.g. pylorus, uterine os) or
697-405: The pelvic diaphragm . It supports the viscera in the pelvic cavity , and surrounds the various structures that pass through it. The levator ani is the main pelvic floor muscle and contracts rhythmically during female orgasm , and painfully during vaginismus . The levator ani is made up of 3 parts: The iliococcygeus arises from the inner side of the ischium (the lower and back part of
738-406: The puboprostaticus in the male. The levator ani arises, in front, from the posterior surface of the superior pubic ramus lateral to the symphysis ; behind, from the inner surface of the spine of the ischium ; and between these two points, from the obturator fascia . Posteriorly, this fascial origin corresponds, more or less closely, with the tendinous arch of the pelvic fascia, but in front,
779-434: The respiratory tract , the arrector pili of skin , the ciliary muscle , and the iris of the eye . The structure and function is basically the same in smooth muscle cells in different organs, but the inducing stimuli differ substantially, in order to perform individual actions in the body at individual times. In addition, the glomeruli of the kidneys contain smooth muscle-like cells called mesangial cells . Cardiac muscle
820-420: The urogenital diaphragm . Behind, it is prolonged into the gluteal region. The internal pudendal vessels and pudendal nerve cross the pelvic surface of the internal obturator and are enclosed in a special canal— Alcock's canal —formed by the obturator fascia. The iliococcygeus portion of the levator ani attaches to the lateral walls of the pelvis via the obturator fascia through the tendinous arch of
861-596: The appearance of the flexed biceps resembles the back of a mouse. The same phenomenon occurred in Greek , in which μῦς, mȳs , means both "mouse" and "muscle". There are three types of muscle tissue in vertebrates: skeletal , cardiac , and smooth . Skeletal and cardiac muscle are types of striated muscle tissue . Smooth muscle is non-striated. There are three types of muscle tissue in invertebrates that are based on their pattern of striation: transversely striated, obliquely striated, and smooth muscle. In arthropods there
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#1732801712297902-469: The body to form all other muscles. Myoblast migration is preceded by the formation of connective tissue frameworks, usually formed from the somatic lateral plate mesoderm . Myoblasts follow chemical signals to the appropriate locations, where they fuse into elongate skeletal muscle cells. The primary function of muscle tissue is contraction . The three types of muscle tissue (skeletal, cardiac and smooth) have significant differences. However, all three use
943-402: The body. In vertebrates , the three types are: Skeletal muscle tissue consists of elongated, multinucleate muscle cells called muscle fibers , and is responsible for movements of the body. Other tissues in skeletal muscle include tendons and perimysium . Smooth and cardiac muscle contract involuntarily, without conscious intervention. These muscle types may be activated both through
984-564: The contraction has occurred. The different muscle types vary in their response to neurotransmitters and hormones such as acetylcholine , noradrenaline , adrenaline , and nitric oxide depending on muscle type and the exact location of the muscle. Sub-categorization of muscle tissue is also possible, depending on among other things the content of myoglobin , mitochondria , and myosin ATPase etc. The word muscle comes from Latin musculus , diminutive of mus meaning mouse , because
1025-421: The female, the anterior fibers of the levator ani descend upon the side of the vagina . The levator ani muscles are mostly innervated by the pudendal nerve , perineal nerve and acting together. In addition, sacral spinal nerves ( S3 , S4 ) innervate the muscles directly as well (in ~70% of people). Sometimes (in ~40% of people) the inferior rectal nerve innervates the levator ani muscles independently of
1066-464: The four basic types of animal tissue . Muscle tissue gives skeletal muscles the ability to contract . Muscle is formed during embryonic development , in a process known as myogenesis . Muscle tissue contains special contractile proteins called actin and myosin which interact to cause movement. Among many other muscle proteins, present are two regulatory proteins , troponin and tropomyosin . Muscle tissue varies with function and location in
1107-401: The human, as tail-wagging is more demanding than the support function that the muscles serve in humans. Levator ani syndrome is episodic rectal pain caused by spasm of the levator ani muscle. [REDACTED] This article incorporates text in the public domain from page 422 of the 20th edition of Gray's Anatomy (1918) Muscle Muscle is a soft tissue , one of
1148-449: The interaction of the central nervous system as well as by receiving innervation from peripheral plexus or endocrine (hormonal) activation. Striated or skeletal muscle only contracts voluntarily, upon the influence of the central nervous system. Reflexes are a form of non-conscious activation of skeletal muscles, but nonetheless arise through activation of the central nervous system, albeit not engaging cortical structures until after
1189-451: The lower part of the pubic symphysis , and from the superior fascia of the urogenital diaphragm . The origin of the puborectalis fibers is at the posterior surface of the pubis while their insertion is at the midline sling posterior to the rectum. The muscle band is innervated by perineal branches of the S3 and S4 nerve roots. They meet with the corresponding fibers of the opposite side around
1230-447: The lower part of the rectum, and form for it a strong sling. Relaxation increases the angle between rectum and anus, allowing defecation in conjunction with relaxation of the internal and external anal sphincters . Levator ani relaxation and rectal emptying is facilitated by anorectal straightening during squatting. The levator ani muscles are responsible for "wagging" the tail in tailed quadrupeds . These muscles are not as strong in
1271-430: The movement of actin against myosin to create contraction. In skeletal muscle, contraction is stimulated by electrical impulses transmitted by the motor nerves . Cardiac and smooth muscle contractions are stimulated by internal pacemaker cells which regularly contract, and propagate contractions to other muscle cells they are in contact with. All skeletal muscle and many smooth muscle contractions are facilitated by
Levator ani - Misplaced Pages Continue
1312-410: The muscle arises from the fascia at a varying distance above the arch, in some cases reaching nearly as high as the canal for the obturator vessels and nerve. The fibers pass downward and backward to the middle line of the floor of the pelvis; the most posterior are inserted into the side of the last two segments of the coccyx ; those placed more anteriorly unite with the muscle of the opposite side, in
1353-660: The outer epicardium layer and the inner endocardium layer. Coordinated contractions of cardiac muscle cells in the heart propel blood out of the atria and ventricles to the blood vessels of the left/body/systemic and right/lungs/pulmonary circulatory systems . This complex mechanism illustrates systole of the heart. Cardiac muscle cells, unlike most other tissues in the body, rely on an available blood and electrical supply to deliver oxygen and nutrients and to remove waste products such as carbon dioxide . The coronary arteries help fulfill this function. All muscles are derived from paraxial mesoderm . The paraxial mesoderm
1394-445: The pubococcygeus muscle also engages the cremasteric reflex , which lifts the testicles up, although this does not occur in all men. Kegel exercises have been prescribed to ameliorate erectile dysfunction due to venous leakage and to help men control premature ejaculation and to treat urinary incontinence in both sexes. The fibers that form a sling looping around the rectum are named puborectalis (puboanalis). They arise from
1435-411: The pudendal nerve. The pubococcygeus muscle or PC muscle is a hammock-like muscle, found in both sexes, that stretches from the pubic bone to the coccyx (tail bone) forming the floor of the pelvic cavity and supporting the pelvic organs. The pubococcygeus arises from the back of the pubis and from the anterior part of the obturator fascia , and is directed backward almost horizontally along
1476-640: The responsible muscles can also react to conscious control. The body mass of an average adult man is made up of 42% of skeletal muscle, and an average adult woman is made up of 36%. Cardiac muscle tissue is found only in the walls of the heart as myocardium , and it is an involuntary muscle controlled by the autonomic nervous system . Cardiac muscle tissue is striated like skeletal muscle, containing sarcomeres in highly regular arrangements of bundles. While skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles known as intercalated discs . Smooth muscle tissue
1517-458: The sacrum. This insertion into the vertebral column is, however, not accepted by all observers. The pubococcygeus muscle controls urine flow and contracts during orgasm as well as assisting in male ejaculation . It also aids in childbirth as well as core stability. A strong pubococcygeus muscle has also been linked to a reduction in urinary incontinence and proper positioning of the baby's head during childbirth. The Kegel exercises are
1558-419: The side of the anal canal toward the coccyx and sacrum , to which it finds attachment. Between the termination of the vertebral column and the anus, the two pubococcygeus muscles come together and form a thick, fibromuscular layer lying on the raphe (ridge) or ( anococcygeal body ) formed by the iliococcygei. The greater part of this muscle is inserted into the coccyx and into the last one or two pieces of
1599-524: The skeletal muscle of mice. Smooth muscle is involuntary and non-striated. It is divided into two subgroups: the single-unit (unitary) and multiunit smooth muscle . Within single-unit cells, the whole bundle or sheet contracts as a syncytium (i.e. a multinucleate mass of cytoplasm that is not separated into cells). Multiunit smooth muscle tissues innervate individual cells; as such, they allow for fine control and gradual responses, much like motor unit recruitment in skeletal muscle. Smooth muscle
1640-426: The transport of the chyme through wavelike contractions of the intestinal tube. Smooth muscle cells contract more slowly than skeletal muscle cells, but they are stronger, more sustained and require less energy. Smooth muscle is also involuntary, unlike skeletal muscle, which requires a stimulus. Cardiac muscle is the muscle of the heart. It is self-contracting, autonomically regulated and must continue to contract in
1681-414: The two is retained only through the periosteum . It arches beneath the obturator vessels and nerve, completing the obturator canal , and at the front of the pelvis is attached to the back of the superior ramus of the pubis . Below, the obturator fascia is attached to the falciform process of the sacrotuberous ligament and to the pubic arch , where it becomes continuous with the superior fascia of