By N. Stan. State University of New York College at New Paltz.
His the dissections were performed by elegantly robed anatomists many contributions included developing techniques for examin- who were also splendid orators buy vardenafil 20 mg visa. The subjects were usually exe- ing tissues and describing blood cells purchase vardenafil 10mg with mastercard, skeletal muscle generic 10mg vardenafil visa, and cuted prisoners vardenafil 10 mg for sale, and the performances were scheduled during the lens of the eye 10 mg vardenafil free shipping. Although he was the first to accurately de- cold weather because of the perishable nature of the cadavers. History of Anatomy © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 16 Unit 1 Historical Perspective salivary glands and lymph nodes within the neck and facial re- gions. In 1664, Thomas Willis published a summary of what was then known about the nervous system. A number of anatomical structures throughout the body are named in honor of the early anatomists. Thus we have graafian follicles, Stensen’s and Wharton’s ducts, fallopian tubes, Bartholin’s glands, the circle of Willis, and many others. Because these terms have no descriptive basis, they are not particularly useful to a student of anatomy. Nineteenth Century The major scientific contribution of the nineteenth century was the formulation of the cell theory. It could be argued that this theory was the most important breakthrough in the history of bi- ology and medicine because all of the body’s functions were eventually interpreted as the effects of cellular function. The term cell was coined in 1665 by an English physician, Robert Hooke, as he examined the structure of cork under his mi- croscope in an attempt to explain its buoyancy. What Hooke actu- ally observed were the rigid walls that surrounded the empty cavities of the dead cells. The significance of cellular structure did not be- come apparent until approximately 150 years after Hooke’s work. Rather, he thought that a spermatozoan contained a teen years later, René H. Dutrochet described the differences be- miniature human being called a homunculus. The development of the microscope added an entirely new Two German scientists, Matthias Schleiden and Theodor dimension to anatomy and eventually led to explanations of Schwann, are credited with the biological principle referred to as basic body functions. Schleiden, a botanist, suggested in 1838 that each invaluable for understanding the etiologies of many diseases, and plant cell leads a double life—that is, in some respects it behaves thus for discovering cures for many of them. Although Leeuwen- as an independent organism, but at the same time it cooperates hoek improved the microscope, credit for its invention is usually with the other cells that form the whole plant. The first Schwann, a zoologist, concluded that all organisms are composed scientific investigation using a microscope was performed by of cells that are essentially alike. Nineteen years later, the addi- Francisco Stelluti in 1625 on the structure of a bee. In 1858, the German pathologist Rudolf Malpighi and Others Virchow wrote a book entitled Cell Pathology in which he pro- Marcello Malpighi (mal-pe′ge) (1628–94), an Italian anatomist, posed that cells can arise only from preexisting cells. He discovered nism of cellular replication, however, was not understood for the capillary blood vessels that Harvey had postulated and de- several more decades. In 1672, the Dutch teaching career, science was sufficiently undeveloped to allow anatomist Regnier de Graaf described the ovaries of the female him to handle numerous disciplines at once. By the time of his reproductive system, and in 1775 Lazzaro Spallanzani showed death, however, knowledge had grown so dramatically that sev- that both ovum and sperm cell were necessary for conception. Francis Glisson (1597–1677) described the liver, stomach, and intestines, and suggested that nerve impulses cause the emptying of the gallbladder. Thomas Wharton (1614–73) and Niels Twentieth Century Stensen (1638–86) separately contributed to knowledge of the Contributions to the science of anatomy during the twentieth century have not been as astounding as they were when little was homunculus: L. History of Anatomy © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 1 History of Anatomy 17 (a) (b) (c) FIGURE 1. Because of the proliferation of scientific literature niques of such cognate disciplines as chemistry, physics, electron- toward the end of the nineteenth century, over 30,000 terms for ics, mathematics, and computer science have been incorporated structures in the human body were on record, many of which into research efforts. In 1895, in an attempt to reduce the confusion, There are several well-established divisions of human the German Anatomical Society compiled a list of approxi- anatomy.
Not all fiber systems that pass the masticatory and deglutitory muscles through the epithalamic commissure (B15) (olfactory stimuli leading to secretion of are known buy vardenafil 10mg visa. The habenulo-inter- From the various pretectal nuclei that send peduncular tract proven vardenafil 10mg, Meynert’s bundle (A11) buy 20 mg vardenafil, ter- fibers through the commissure generic vardenafil 20 mg with mastercard, the intersti- minates in the interpeduncular nucleus tial nucleus of Cajal and Darkshevich’s nu- (A12) (p cheap vardenafil 20 mg free shipping. Itscells,thepinealocytes,aregrouped into lobules by connective tissue septa. Habenula and Epiphysis 177 7 2 1 3 4 5 11 13 17 9 8 16 18 12 6 10 20 A Fiber connections of 14 the habenula 19 15 B Pineal gland C Pinealocytes, silver impregnation D Histological appearance of the pineal gland, (according to Hortega) silver impregnation (according to Hortega) Kahle, Color Atlas of Human Anatomy, Vol. Their medial surfaces form clei are subdivided into the following nu- the wall of the third ventricle, while their clear groups (or complexes): lateral surfaces border on the internal cap-! The medial nuclear group, medial thalamic rigeminal plate of the midbrain. The lateral nuclear group, ventrolateral most sensory pathways, almost all of which thalamic nuclei (blue) (CD7); this group is terminate in the contralateral thalamus. The thalamus (A1) is connected to the cere- The nuclear groups are separated by layers bral cortex by the corona radiata, or of fibers: the internal medullary lamina (D12) thalamic radiation (A2–4). The fibers run (between the medial nuclear group and the obliquely through the internal capsule lateral and anterior nuclear groups) and the toward the cerebral cortex. The more prom- externalmedullarylamina (D13) (between the inent bundles are the anterior thalamic radia- lateral nuclear group and the reticular nu- tion (A2) (to the frontal lobe), the superior cleus which encloses the lateral surface of thalamic radiation (A3) (to the parietal lobe), the thalamus). The cates the central function of the thalamus, most anterior nuclear groups are the ante- which is directly or indirectly integrated rior nuclei (B5) to which the medial nuclei into most systems. In the lateral complex, uniform structure but a highly organized we distinguish between a nuclear group lo- complex consisting of diversely structured cated dorsally (the lateral nuclei, lateral dor- nuclear groups. Nuclei (the ventral nuclei, ventral anterior nucleus with fiber connections to the cerebral cor- [C17], ventral lateral nucleus [C18], and ven- tex are collectively called specific thalamic tral posterior nucleus [C19]). Thalamic Radiation, Specific Thalamic Nuclei 179 2626 33 11 44 22 2121 A Thalamic radiation, fiber preparation 2020 (according to Ludwig and Klingler) 55 66 1010 B, C Diagrammatic reconstruction of the thalamic complexes 1414 2121 55 2020 99 1515 1616 88 B Median view 1717 1010 1818 2222 1919 77 1313 99 55 2525 88 2323 2424 1212 1111 77 66 C Lateral view D Frontal section showing nuclear organization Kahle, Color Atlas of Human Anatomy, Vol. Their neurons are not nuclei project to their cortical fields and, in injured by removal of the entire cerebral turn, the cortical fields project to the re- cortex; they are cortex-independent. Thus,thereexistsa groups of nuclei are distinguished: neuronal circuit with a thalamocortical! The median nuclei (nuclei of the central limb and a corticothalamic limb. The neu- thalamic gray matter) (B20), which are rons of the specific thalamic nuclei transmit small cell clusters located along the wall impulses to the cerebral cortex and are, in of the third ventricle turn, influenced by the respective cortical! Hence, the function of a cortical field embedded into the internal medullary cannot be examined without the thalamic lamina; the largest of them is the cen- nucleus belonging to it; likewise, the func- tromedian nucleus (B22) tion of a thalamic nucleus cannot be ex- amined without the cortical field belonging Electrical stimulation of these nuclei does to it. Hence, they are clei become separated from their axon ter- called nonspecific nuclei. The pathways minals, they respond by retrograde through which cortical activity is influenced degeneration. The ascending pathways of cumscribed cortical fields results in neu- the reticular formation (ascending activat- ronal death in the respective thalamic nu- ing system, p. The anterior nuclei (A1) are connected with the cortex of the cingulate gyrus (A2) Alternative Nuclear Subdivision (C) and the medial nuclei (A3) with the cortex of The subdivision of the thalamus according to the frontal lobe (A4). The lateral nuclei (A5) Hassler differs from the traditional arrange- project to the dorsal and medial cortex of ment mainly with respect to the subdivision the parietal lobe (A6), with the lateral dorsal of the lateral nuclear complex. The nucleus nucleus partly supplying the retrosplenial located most orally is called the lateropolar part of the cingulate gyrus. Then follows the division into tral nuclei, the ventral anterior nucleus (A7) is dorsal, ventral, and central zones. These connected with the premotor cortex (A8), three zones are further divided into oral, in- the ventrallateralnucleus (A9) with the motor termediate, and caudal segments. This re- precentral area (A10), and the ventral poste- sults in the following nuclei: dorsally lie the rior nucleus (A11) with the sensory postcen- dorso-oral nucleus (C24), the dorsointerme- tral area (A12). The pulvinar (A13) projects to diate nucleus (C25), and the dorsocaudal nu- the cortical parts of the parietal and tem- cleus (C26), and ventrally lie the ventro-oral poral lobes (A14) and to the cuneus (A15).
The nucleus projects to dial segment of the nucleus purchase 10mg vardenafil amex, the ventralpost- the premotor cortex (A7) but depends only eromedial nucleus (VPM) (B17) quality vardenafil 20 mg. They transmit partially on the cortex because only half of sensory information from the head and oral its neurons die after injury to the cortical re- cavity order vardenafil 20 mg line, thus completing the homunculus of gion vardenafil 20mg without prescription. The ventral anterior nucleus is inte- the contralateral half of the body cheap vardenafil 20mg online. The ter- grated into the ascending activation system; minus of the secondary gustatory pathway stimulation within the nuclear zone causes (p. The trigeminal pain fibers, are thought to termi- most important afferent system of the nu- nate bilaterally in the basal areas of the nu- cleus are the fibers of the crossed superior cleus. In the anterior (A18) extend to the sensory postcentral area segment of the ventral lateral nucleus there (p. The efferent of the ventral posterior nucleus and its pro- fibers (A11) extend to the cortex of the pre- jection to the cerebral cortex. The somatotopic or- ganization of the ventral lateral nucleus is obvious in this system (AB8); the lateral part of the nucleus is connected to the leg region of the precentral cortex, the adjacent parts to the trunk and arm regions, and the medial part to the head region. Thus, thalamic nucleus and cortical area show a corresponding topical subdivision. Informa- tion from the cerebellum (body posture, coordination, muscle tone) reaches the motor cortex via the ventral lateral nucleus; the cerebellum influences voluntary move- Kahle, Color Atlas of Human Anatomy, Vol. Lateral and Ventral Nuclear Groups 185 7 3 11 12 1 2 18 4 8 14 6 5 10 15 A Fiber connections of the lateral complex (lateroventral thalamic nuclei) 9 4 8 13 17 16 B Somatotopic organization of the ventral nuclei, horizontal section (according to Hassler) Kahle, Color Atlas of Human Anatomy, Vol. Knowledge of the functional organization makes it possible to stop severe pain Medial Geniculate Body (D) through stereotactic destruction within the ventral posterior nucleus without affecting This nucleus (D3) is the diencephalic relay tactile sensation. Itappearsas the ventral lateral nucleus, motor distur- an externally visible eminence medially to bances (hyperkinesis) can be eliminated the lateral geniculate body. Some fiber bundles of the auditory representation of various body regions. As pathway come from the nucleus of the trape- shown in the stimulation diagram (red sym- zoid body and the ipsilateral cochlear nuclei; bols) (A), the representation of the body however, most fibers originate from the runs obliquely from dorsolateral (leg region, contralateral cochlear nuclei. The efferent | ; arm region, –) to mediobasal (head re- fibers of the medial geniculate nucleus ex- gion, (! Controlled stimulation of the tend to the auditory cortex (D5), which lies ventral lateral nucleus (orange symbols) (B) in the transverse temporal gyri, or Heschl’s con- results also in involuntary sound produc- volutions (p. Sinceitdoesnotre- Lateral Geniculate Body (C) ceive any extrathalamic input, it must be This nucleus (C1) lies somewhat isolated at viewed as an integration nucleus. Afferent theventrocaudalaspectofthethalamusand fibers from the lateral geniculate nucleus is a relatively independent structure. It (collaterals of the optic fibers) and probably shows stratification into six cell layers also fibers from the medial geniculate nu- which are separated by the afferent fiber cleus enter the pulvinar. Crossed and un- There are reciprocal fiber connections be- crossed optic fibers terminate in a regular tween the pulvinar and the cortex of the arrangement (p. In the left lateral genicu- Hence, the pulvinar is not only integrated late body, the temporal half of the retina of into the optic and acoustic systems but is thelefteyeandthenasalhalfoftheretinaof also connected with the cortical areas im- the right eye are represented; in the right portant for language and symbolic thinking lateral geniculate body, the temporal half of (p. The fibers from the macula, which tion) of the pulvinar causes speech disorder in is the region of greatest visual acuity, termi- humans. The neurons of the lateral geniculate nu- cleus send their axons to the visual cortex, Kahle, Color Atlas of Human Anatomy, Vol. Ventral Nuclei, Lateral and Medial Geniculate Bodies 187 B Responses of speech and sound following stimulation of the ven- tral lateral nucleus (according to Schaltenbrand, Spuler, Wahren and A Motor responses following stimu- Rümler) lation of the ventral lateral nu- cleus (according to Schaltenbrand, Spuler, Wahren and Rümler) 2 1 C Fiber connections of the lateral geniculate body 5 3 D Fiber connections of the medial 4 geniculate body Kahle, Color Atlas of Human Anatomy, Vol. During tinuously compensate for changes from the circular ciliary light to dark and from near to far. The meridional aperture and lens system must continu- muscle fibers pull the origins of the long ously adapt to the prevailing conditions. This relaxes both the requires a change in the curva- zonular fibers (), and the lens capsule, ture of the lens (), a change thus causing the lens to round off (). During The fiber tracts of the (adjustment for long dis- are less well known.
Electrical slow waves trigger action potentials buy vardenafil 20mg, and action potentials trigger con- tractions order 20mg vardenafil free shipping. Level 5 includes higher brain centers that provide in- Autonomic Parasympathetic Neurons Project to put for integrative functions at levels 3 and 4 generic 10 mg vardenafil amex. Projections to the digestive tract from tramural control networks that make up the intrinsic these regions of the CNS are preganglionic efferents discount vardenafil 20 mg with amex. The parasympa- thetic and sympathetic subdivisions are identified by the positions of the ganglia containing the cell bodies of the postganglionic neurons and by the point of outflow from 5 the CNS 20 mg vardenafil fast delivery. Comprehensive autonomic innervation of the di- Higher brain centers 4 3 Central parasympathetic Central sympathetic centers centers ICC network 2 Prevertebral sympathetic ganglia 1 GI muscle Enteric nervous system FIGURE 26. Gastrointestinal, esophageal, and biliary tract Electrical slow waves originate in the networks of ICCs. ICCs are musculature and mucosa the generators (pacemaker sites) of the slow waves. Signals from parasympathetic centers in the CNS are trans- mitted to the enteric nervous system by the vagus and pelvic Vago-Vagal Reflex Circuits Consist of Sensory nerves. These signals may result in contraction ( ) or relaxation ( ) of the digestive tract musculature. Afferents, Second-Order Interneurons, and Efferent Neurons A reflex circuit known as the vago-vagal reflex underlies moment-to-moment adjustments required for optimal di- ronal cell bodies in the dorsal motor nucleus in the medulla gestive function in the upper digestive tract (see Clinical oblongata project in the vagus nerves, and those in the Focus Box 26. The afferent side of the reflex arc consists sacral region of the spinal cord project in the pelvic nerves of vagal afferent neurons connected with a variety of sen- to the large intestine. Efferent fibers in the pelvic nerves sory receptors specialized for the detection and signaling of make synaptic contact with neurons in ganglia located on mechanical parameters, such as muscle tension and mucosal the serosal surface of the colon and in ganglia of the ENS brushing, or luminal chemical parameters, including glu- deeper within the large intestinal wall. Cell bodies of the synapse with neurons of the ENS in the esophagus, stom- vagal afferents are in the nodose ganglia. The afferent neu- ach, small intestine, and colon, as well as in the gallbladder rons are synaptically connected with neurons in the dorsal and pancreas. The nucleus of the tractus solitarius, which lies vation of the GI musculature to control digestive processes directly above the dorsal motor nucleus of the vagus (see both in anticipation of food intake and following a meal. A synaptic meshwork ior in the stomach as a result of activation of the enteric cir- formed by processes from neurons in both nuclei tightly cuits that control excitatory or inhibitory motor neurons, re- links the two into an integrative center. Parasympathetic efferents to the small and large neurons are second- or third-order neurons representing intestinal musculature are predominantly stimulatory as a re- the efferent arm of the reflex circuit. They are the final sult of their input to the enteric microcircuits that control the common pathways out of the brain to the enteric circuits activity of excitatory motor neurons. The dorsal vagal complex consists of the dorsal motor Efferent vagal fibers form synapses with neurons in the nucleus of the vagus, nucleus tractus solitarius, area ENS to activate circuits that ultimately drive the outflow of postrema, and nucleus ambiguus; it is the central vagal in- signals in motor neurons to the effector systems. This center in the brain is more effector system is the musculature, its innervation consists directly involved in the control of the specialized digestive of both inhibitory and excitatory motor neurons that par- functions of the esophagus, stomach, and the functional ticipate in reciprocal control. If the effector systems are cluster of duodenum, gallbladder, and pancreas than the gastric glands or digestive glands, the secretomotor neu- distal small intestine and large intestine. The circuits in the rons are excitatory and stimulate secretory behavior. The generalized Abdominal Early satiety symptoms of both disorders overlap (Fig. Surgical Heartburn Pallor vagotomy results in a rapid emptying of liquids and a de- Anorexia Rapid pulse layed emptying of solids. As mentioned earlier, vagotomy Weight loss Perspiration impairs adaptive relaxation and results in increased con- Syncope tractile tone in the reservoir (see Fig. Increased pressure in the gastric reservoir more forcefully presses liquids into the antral pump. Paralysis with a loss of Delayed Rapid propulsive motility in the antrum occurs after a vagotomy. A Symptoms of disordered gastric empty- layed emptying of solids after a vagotomy. Some of the symptoms of delayed vagotomy is performed as a treatment for peptic ulcer dis- and rapid gastric emptying overlap. Delayed gastric emptying with no demonstrable un- absence of inhibitory motor neurons and the failure of derlying condition is common.
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