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By F. Dimitar. Sweet Briar College.

Two important muscle layers for Somatic motor systems are included insofar as pharyngeal motility in the lower esophagus and small and large intes- phases of swallowing and pelvic floor involvement in defe- tine are the longitudinal and circular layers (Fig purchase 15mg slimex with amex weight loss pills trial offers. The of smooth muscles buy discount slimex 15 mg weight loss pills target, as it relates to enteric neural control of stomach has an additional obliquely oriented muscle layer. Psy- chological and psychiatric aspects of gastrointestinal disor- The Structure and Function of Circular ders are significant components of the neurogastroentero- logical domain, especially in relation to projections of and Longitudinal Muscles Differ discomfort and pain to the digestive tract. The circular muscle layer is thicker than the longitudinal Gastrointestinal (GI) motility refers to wall movement layer and more powerful in exerting contractile forces on or lack thereof in the digestive tract. The long axis of the muscle tion of multiple tissues and types of cells is necessary for fibers of circular muscle is oriented in the circumferential generation of the various patterns of motility found in the direction. Consequently, contraction reduces the diameter organs of the digestive tract. Digestive motor movements of the lumen of an intestinal segment and increases its involve the application of forces of muscle contraction to length. Because the long axis of the muscle fibers is oriented material that may be present in the mouth, pharynx, esoph- in the longitudinal direction, contraction of the longitudi- agus, stomach, gallbladder, or small and large intestines. Specialized pacemaker cells, called in- terstitial cells of Cajal, are associated with the smooth mus- culature. The nervous system, with its different kinds of Longitudinal neurons and glial cells, organizes muscular activity into muscle functional patterns of wall behavior. Functions of the nerv- Myenteric ganglion ous system are influenced by chemical signals released from enterochromaffin cells, enteroendocrine cells, and cells as- Interganglionic fiber tract sociated with the enteric immune system (e. Esophageal motility, for example, differs from gas- tric motility, and gastric motility differs from small intes- tinal motility. The motility in the different organs reflects coordinated contractions and relaxations of the smooth muscle. Contractions are organized to produce the propul- 200 µm sive forces that move the contents along the tract, triturate large particles to smaller particles, mix ingested foodstuff Submucosal Mucosa ganglion with digestive enzymes, and bring nutrients into contact with the mucosa for efficient absorption. The enteric plexus between the longitudinal and the circular muscle layer and nervous system (ENS), together with its input from the form the submucosal plexus between the mucosa and circular CNS, organizes motility into patterns of efficient behavior muscle layer. CHAPTER 26 Neurogastroenterology and Gastrointestinal Motility 451 Both longitudinal and circular muscle layers are innervated transmit electrical current from muscle fiber to muscle by motor neurons of the ENS. Ionic connectivity, without cytoplasmic continuity is innervated mainly by excitatory motor neurons; the circu- from fiber to fiber, accounts for the electrical syncytial lar muscle layer by both excitatory and inhibitory motor neu- properties of smooth muscle, which confers electrical be- rons. Nonneural pacemaker cells and excitatory motor neu- havior analogous to that of cardiac muscle (see Chapter rons activate contraction of the circular muscle, and 13). Electrical activity and associated contractions spread excitatory motor neurons are the main triggers for contrac- from a point of initiation (e. More gap junctions between three dimensions throughout the bulk of the muscle. The adjacent muscle fibers are found in the circular layer than in distance and the direction of electrical activity spread are the longitudinal muscle layer. A failure of nervous control can lead muscle cells is important for excitation-contraction coupling to disordered motility that includes spasm and associated in longitudinal muscle fibers. Slow Waves and Action Potentials Are Forms of Electrical Activity in GI Muscles Smooth Muscles Are Classified as Unitary Electrical slow waves are omnipresent and responsible for or Multiunit Types triggering action potentials in some regions, whereas in Smooth muscles are classified based on their behavioral other regions (e. These muscles contract sponta- testine where they decrease in frequency along a gradient neously in the absence of neural or endocrine influence and from the duodenum to the ileum. There are no structured terms slow wave and action potential are used interchangeably neuromuscular junctions, and neurotransmitters travel over for the same electrical event. When action potentials are as- extended diffusion distances to influence relatively large sociated with electrical slow waves, they occur during the numbers of muscle fibers. The smooth muscle of the esoph- plateau phase of the slow wave (see Fig. These Action potentials in GI smooth muscle are mediated by muscles do not contract spontaneously in the absence of changes in calcium and potassium conductances. The opening of potassium channels as the calcium channels are closing at or near the peak of the action potential ac- Electromechanical and Pharmacomechanical counts for the repolarization phase.

The barrier may result in a complete The capillary wall consists of endothelialcells blockade or in a delay of penetration generic 10 mg slimex overnight delivery weight loss kickstart. The capillary is enclosed by the basallamina (BE3) and the astrocyte covering (BE4) buy discount slimex 10mg on-line weight loss pills best rated. The sealing of the brain tissue from the rest of the body manifests itself in the blood– brain barrier, a selective barrier for numer- ous substances that are prevented from penetrating from the bloodstream through the capillary wall into the brain tissue. If the dye is injected intravenously into experi- mental animals (Goldmann’s first experiment) (C), almost all organs stain blue, but the brain and spinal cord remain unstained. Minor blue staining is only found in the gray tubercle (C5), the postremal area, and the spinal ganglia. The choroid plexus (C6) and the dura (C7) show a distinct blue staining. The same pattern is observed in cases of jaundice in humans; the bile pigment stains all organs yellow, only the CNS remains un- stained. If the dye is injected into the space Kahle, Color Atlas of Human Anatomy, Vol. Perivascular Glial Feet, Blood–Brain Barrier, Blood–CSF Barrier 45 1 5 6 5 7 A Blood vessel surrounded by astrocytes, silver impregnation 4 2 3 C Goldmann’s first experiment 1 7 B Blood vessel with perivascular glial feet (diagram according to Wolff) 3 2 8 4 D Goldmann’s second experiment E Brain capillary (left) and kidney capillary C–D Blood-brain barrier in the rab- (right), diagram based on electron- bit (according to Spatz) microscopic findings Kahle, Color Atlas of Human Anatomy, Vol. Spinal Cord and Spinal Nerves Overview 48 The Spinal Cord 50 Peripheral Nerves 70 Cervical Plexus 72 Posterior Branches 72 Brachial Plexus 74 Nerves of the Trunk 84 Lumbosacral Plexus 86 Sacral Plexus 90 Kahle, Color Atlas of Human Anatomy, Vol. It has two spindle- emerges from the foramen lying at its own shaped swellings: one in the neck region, level. During development, however, the the cervical enlargement (C1), and one in the vertebral column increases much more in lumbar region, the lumbar enlargement (C2). As a result, At the lower end, the spinal cord tapers into the lower end of the spinal cord moves the medullary cone (BC3) and ends as a thin further up in relation to the surrounding thread, the terminal filament (C4). In the newborn, the lower end of riormedianfissure at the ventral side and the the spinal cord lies at the level of the third posterior median sulcus (BC5) at the dorsal lumbar vertebra, and in the adult, at the side mark the boundaries between the two level of the first lumbar or twelfth thoracic symmetrical halves of the spinal cord. Thus, the spinal nerves no longer fibers enter dorsolaterally and emerge ven- emerge at their levels of origin; instead, trolaterally at both sides of the spinal cord their roots run down a certain distance and unite to form the dorsal roots, posterior within the vertebral canal to their foramen roots, and the ventral roots, anteriorroots. The more caudally the roots join to form short nerve trunks of 1cm roots originate from the spinal cord, the in length, the spinal nerves. Only the are therefore no longer identical with the posterior roots of the first cervical spinal corresponding levels of the spinal cord. From the medullary cone (BC3) onward, the vertebral canal contains only a dense mass Inhumans,thereare31pairsofspinalnerves of descending spinal roots, known as the which emerge through the intervertebral cauda equina (tail of a horse) (B7). The impression of segmentation is created by the bundling of nerve fibers emerging from the foramina (p. The spinal nerves are subdivided into cervi- calnerves, thoracicnerves, lumbarnerves, sacral nerves, and coccygeal nerves (A). Spinal Cord and Spinal Nerves 49 1 2 C 1 C 2 3 4 1 5 6 C 7 7 C 8 T 1 T 1 8 1 2 5 6 3 4 5 6 7 8 9 10 5 11 2 12 T 12 1 L 1 L 1 3 2 3 4 4 7 L 5 C Spinal cord S 1 S 1 5 1 Coccyx 2 Sacral 3 nerves 4 5 Coccygeal nerves A Lateral view of the spinal nerves B Dorsal view of the spinal ganglia Kahle, Color Atlas of Human Anatomy, Vol. The relay may also take place in the medulla ob- Structure (A, B) longata. However, the afferent fibers may also run to the anterior horn cells and trans- The gray matter, substantia grisea (nerve mit the signal directly to these cells. The re- cells), appears in transverse section of the sulting muscle reaction is called reflex, the spinal cord as a butterfly configuration sur- underlying neuronal circuit is called reflex rounded by the white matter, substantia alba arc (D). Wedistinguishoneithersidea run directly to the motor neuron (mono- dorsal horn (posterior horn) (AB1) and a ven- synaptic reflex arc) but via interneurons that tral horn (anterior horn) (AB2). Between them lies the cen- reflex)and the multisynaptic extrinsic reflex tral intermediate substance (A3) with the (withdrawal reflex) are of clinical impor- obliterated central canal (A4). In the stretch reflex (F), the muscle is thoracicspinalcord,thelateralhorn(AB5)is briefly stretched by a tap on its tendon. The lateral posterior sulcus (A6) is results in a momentary contraction of the the site where the posterior root fibers muscle as a counter reaction. The anterior root fibers (AB8) volves only a few neurons at any level of the leave the anterior side of the spinal cord as spinal cord.

These individuals have a 46 XY chromosome con- (about 60%) is produced by the seminal vesicles cheap 10 mg slimex otc weight loss 360, and the rest stitution and male gonads cheap slimex 10 mg without a prescription weight loss group names, but the genitalia are intersexual and (about 40%) is contributed by the prostate. There are usually between 60 and 150 million sperm cells per milliliter of ejaculate. Male Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 Chapter 20 Male Reproductive System 715 The treatment of hermaphroditism varies, depending on the extent of ambiguity of the reproductive organs. Although people with this condition are sterile, they may engage in normal Pelvic sexual relations following hormonal therapy and plastic surgery. The two most 3 Symphysis frequent chromosomal anomalies cause Turner’s syndrome and pubis Klinefelter’s syndrome. About 97% of embryos lacking an X chromosome die; the remaining 3% survive and appear to be Penis females, but their gonads, if present, are rudimentary and do not Scrotum mature at puberty. A person with Klinefelter’s syndrome has an XXY chromosome constitution, develops breasts and male geni- (a) Creek talia, but has underdeveloped seminiferous tubules and is gener- ally mentally retarded. A more common developmental problem than genetic ab- normalities, and fortunately less serious, is cryptorchidism. A cryptorchid testis is usually located along the path of descent but can be anywhere in the pelvic cavity 1 (fig. It occurs in about 3% of male infants and should be treated before the infant has reached the age of 5 to reduce the likelihood of infertility or other complications. The causes of impotence may be physical, involving, for example, ab- normalities of the penis, vascular irregularities, neurological dis- Pelvic cavity orders, or certain diseases. Occasionally, the cause of impotence 1 is psychological, and the patient requires skilled counseling by a sex therapist. The most common 3 cause of male infertility is inadequate production of viable sperm. This may be due to alcoholism, dietary deficiencies, local injury, Penis variococele, excessive heat, hormonal imbalance, or excessive exposure to radiation. Many of the causes of infertility can be Scrotum treated through proper nutrition, gonadotropic hormone treat- (c) ment, or microsurgery. If these treatments are not successful, it may be possible to concentrate the spermatozoa obtained FIGURE 20. Turner, American endocrinologist, pelvic wall, (2) at the root of the penis, or (3) in the perineum, in the 1892–1970 thigh alongside the femoral vessels. Male Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 Developmental Exposition Externally, by the sixth week a swelling called the genital The Reproductive System tubercle is apparent anterior to the small embryonic tail (future coccyx). The mesonephric and paramesonephric ducts open to the outside through the genital tubercle. The genital tubercle EXPLANATION consists of a glans, a urethral groove, paired urethral folds, and paired labioscrotal swellings (see exhibit II). As the glans portion Sex Determination of the genital tubercle enlarges, it becomes known as the phallus. Early in fetal development (tenth through twelfth week), sexual Sexual identity is initiated at the moment of conception, when distinction of the external genitalia becomes apparent. The male, the phallus enlarges and develops into the glans of the ovum is fertilized by a spermatozoon containing either an X or a Y penis. The urethral folds fuse around the urethra to form the body sex chromosome. The urethra opens at the end of the glans as the ure- it will pair with the X chromosome of the ovum and a female thral orifice. The labioscrotal swellings fuse to form the scrotum, child will develop. A spermatozoon carrying a Y chromosome re- into which the testes will descend. In the female, the phallus sults in an XY combination, and a male child will develop. The urethral groove is retained as a longitudinal cleft sex hormones during late embryonic and early fetal development known as the vestibule. Descent of the Testes Embryonic Development The descent of the testes from the site of development begins be- The male and female reproductive systems follow a similar pattern of tween the sixth and tenth week. Descent into the scrotal sac, development, with sexual distinction resulting from the influence of however, does not occur until about week 28, when paired in- hormones. A significant fact of embryonic development is that the guinal canals form in the abdominal wall to provide openings sexual organs for both male and female are derived from the same from the pelvic cavity to the scrotal sac.

If coughing and Training that helps individuals increase swallowing ability is insufficient 10 mg slimex for sale weight loss jump start, aspira- posture control and the use of braces and tion of food or fluids may place individ- splints can retard the development of uals at risk of respiratory infections or degenerative joint disease and scoliosis buy slimex 15 mg on-line weight loss pills pregnancy. Training to help individuals develop Although not necessarily a complica- improved breathing patterns, coughing, tion, fatigue secondary to manifestations and lung expansion can decrease the of cerebral palsy can also interfere with chances of aspiration and consequently individuals’ ability to function efficiently. Because they may experience difficulty with Adequate rest at night as well as estab- motor control and coordination, more lishment of rest periods throughout the energy may be expended to carry out even day can decrease fatigue. Involuntary viduals’ total energy output and adjusting movement or spasticity may also increase their tasks and schedules to fit their needs the amount of energy expended. As a can help preserve energy and prevent result, individuals with cerebral palsy excessive fatigue. Complications of Cerebral Palsy Psychosocial Issues in Cerebral Palsy Because of the manifestations of cere- Although data regarding the psychoso- bral palsy, a variety of complications that cial adjustment of adults with cerebral pal- are secondary to the condition itself can sy are limited, cerebral palsy as a develop- Conditions Affecting the Brain 59 mental disability poses many of the same For adolescents with cerebral palsy, problems as other developmental disabil- opportunities to participate in social activ- ities. Misunderstanding of the condition ities, information related to sexuality, and by parents, teachers, or others with whom opportunities to participate in sexual individuals with cerebral palsy come in exploration and relationships may have contact can perpetuate a sick and depend- been limited. In addition, adolescents ency status rather than one of empower- with cerebral palsy may have a distorted ment. How individuals with cerebral palsy body image and a low self-concept, which were treated in childhood can influence can affect their social competence, dating, their self-perception and functioning in and sexual behavior. With any type of developmen- als with cerebral palsy, as adolescents as tal disability there is the risk of overpro- well as adults, experience normal desires, tectiveness by parents and others, which they may lack the skills necessary to ful- can impede the individual’s emotional fill those needs. In addition to barriers of development by restricting access to expe- inadequate information, skill, or opportu- riences that are vital to the development nity for appropriate sexual expression, of adequate coping strategies. As a result, they may also experience physical barri- children may learn, at an early age, to use ers because of their disability that make maladaptive behavior to achieve goals. Individu- overly dependent on parents, have been als with communication problems as the given little responsibility for home chores, result of cerebral palsy may have grown up have not been confronted with the typi- in an environment in which family, cal consequences of behavior, or have not friends, and others became accustomed to learned acceptable means of expressing their adaptive communication methods. For often been the focus of a wide variety of instance, those unfamiliar with the indi- services and activities from an early age vidual or with cerebral palsy itself may may continue these expectations into misinterpret problems with hearing or adulthood, demonstrating a sense of ego- unintelligible speech as lack of cognitive centricity that may limit positive social ability. In other instances, because the interactions and lead to further social iso- individual may be difficult to understand, lation. If these behaviors persist into adult- acquaintances may begin to avoid inter- hood, they may become more of an actions with the individual who then impediment to social integration than the becomes socially isolated. At the severity and type of cerebral palsy, times brain damage associated with cere- decreased mobility, problems with eating, bral palsy may also create behavior deficits or problems with personal hygiene may that can interfere with the development further restrict the individual’s social and maintenance of social relationships. Consequently, follow-up through- out the individual’s life may be necessary. Epilepsy As individuals age with their disability, additional limitations may develop. For Epilepsy is a chronic disorder of the instance, fatigue is a consideration for nervous system. It is not a disease, but individuals with cerebral palsy, regardless rather a symptom of an underlying neuro- of age. However, as individuals become logical condition in which neurons in the older, endurance for the same activities brain create abnormal electrical discharges once performed may be decreased. The degree to which individu- no single cause of epilepsy, and it can als are able to achieve their goals in a spec- affect anyone at any age. It can be caused ified occupation will be dependent on by a number of conditions in which func- their physical, psychosocial, and lan- tion of the brain has been affected, such guage abilities, as well as on their motiva- as head injury or stroke. Specific skills and however, no clear-cut cause can be iden- abilities may be enhanced with compen- tified. In this case, epilepsy is considered satory measures and/or with practice. Since the functional limitations associated Although the essential feature of epilep- with cerebral palsy are individual, specif- sy is recurrent seizures, not all seizures are ic vocational limitations will be depend- due to epilepsy. Seizures can occur as a ent on the symptoms each individual result of a temporary dysfunction of the experiences. In some instances, verbal brain brought on by certain conditions, communication is severely impaired, and even though there are no permanent in other cases it may be totally unaffect- changes in brain function. Some individuals may have limited tions such as meningitis (infection of the mobility or ambulation problems; others covering of the central nervous system), may have significant difficulty with mobil- diabetic coma, hypoxia (too little oxygen ity or ambulation.