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Although the inguinal ligament can- not be seen buy discount midamor 45mg on-line hypertension young male, an oblique groove overlying the ligament is an ap- The surface features of the pelvic region are important primarily to parent surface feature buy 45mg midamor overnight delivery hypertension untreated. The Objective 12 Describe the location of the perineum and list surface features of this region are further discussed in chapters 20 the organs of the pelvic and perineal regions. The surface anatomy of the perineum of a female be- comes particularly important during parturition. The important bony structures of the pelvis include the crest of the ilium and the symphysis pubis, located anteriorly, and the is- Knowledge Check chium and coccyx, which are palpable posteriorly. What structures are located spine to the symphysis pubis and is clinically important because within the perineum? Surface and Regional © The McGraw−Hill Anatomy, Sixth Edition Anatomy Companies, 2001 Chapter 10 Surface and Regional Anatomy 319 SHOULDER AND UPPER EXTREMITY Supraclavicular The anatomy of the shoulder and upper extremity is of clinical im- fossa portance because of frequent trauma to these body regions. Objective 13 Identify various surface features of the Clavipectoral shoulder and upper extremity by observation or palpation. Objective 14 Discuss the clinical importance of the axilla, cubital fossa, and wrist. The scapula, clavicle, and proximal portion of the humerus are the bones of shoulder, and portions of each of them are impor- tant surface landmarks in this region. Posteriorly, the spine of the scapula and acromion are subcutaneous and easily located. The acromion and clavicle,as well as several large shoulder muscles,can be seen anteriorly (fig. The rounded curve of the shoulder is formed by the thick deltoid muscle that covers the greater tubercle of the humerus. The deltoid muscle frequently serves as a site for intramuscular injections. The large pectoralis major muscle is prominent as it crosses the shoulder joint and at- FIGURE 10. This depressed re- Several muscles are clearly visible in the brachium (figs. The axilla is clinically important because of the prominent when the elbow is flexed. While the arm is in this posi- subcutaneous position of vessels, nerves, and lymph nodes in tion,the deltoid muscle can be traced as it inserts on the humerus. Two muscles form the anterior and posterior bor- The triceps brachii muscle forms the bulk of the posterior surface ders (fig. A groove forms on the medial side of the pectoralis major muscle, and the posterior axillary fold consists brachium between the biceps brachii and triceps brachii muscles, primarily of the latissimus dorsi muscle as it extends from the where pulsations of the brachial artery may be felt as it carries lumbar vertebrae to the humerus. It is also the place to apply pressure in case mary gland, which is positioned on the pectoralis major mus- of severe arterial hemorrhage in the forearm or hand. The medial and lateral epicondyles are phatic drainage pathway is toward the axilla (see fig. When the elbow is extended, these promi- nences lie on the same transverse plane; when the elbow is flexed, they form a triangle. The ulnar nerve can be palpated in the ulnar sulcus (groove) posterior to the medial epicondyle (see fig. Surface and Regional © The McGraw−Hill Anatomy, Sixth Edition Anatomy Companies, 2001 320 Unit 4 Support and Movement Deltoid m. The cubital fossa is the depression on the anterior surface Antebrachium of the elbow region, where the median cubital vein links the Contained within the antebrachium (forearm) are two parallel cephalic and basilic veins. These veins are subcutaneous and be- bones (the ulna and radius) and the muscles that control the come more conspicuous when a proximal compression is applied. The muscles of the forearm taper dis- For this reason, they are an important location (particularly the tally over the wrist, where their tendons attach to various bones median cubital) for the removal of venous blood for analyses and of the hand. Several muscles of the forearm can be identified as transfusions or for intravenous therapy (fig. Surface and Regional © The McGraw−Hill Anatomy, Sixth Edition Anatomy Companies, 2001 Chapter 10 Surface and Regional Anatomy 321 Triceps brachii m. The ulna can be palpated along its entire length from Tendon of palmaris longus m. Nerves, tendons, and vessels are close to the surface at the Styloid process of ulna wrist, making cuts to this area potentially dangerous. Tendons Thenar eminence from four flexor muscles can be observed as surface features if Hypothenar eminence the anterior forearm muscles are strongly contracted while mak- ing a fist.

The the superior colliculi represents the tran- optic layer (A4) purchase midamor 45 mg with amex heart attack ekg, which in lower vertebrates sition from the midbrain to the dien- consists of fibers of the optical tract buy discount midamor 45mg 7th hypertension, is cephalon. Hence, the cross section already formed in humans by fibers from the lateral contains structures of the diencephalon: genicular body. The deeper layers of cells dorsally on each side lies the pulvinar (B22), and fibers are collectively known as stratum in the middle the epithalamic commissure lemnisci (A5). Here terminate the spinotec- (B23), and ventrally the mamillary bodies tal tract (p. The pretectal region extends dor- lateral lemnisci, and fiber bundles of the in- solaterally with the principalpretectalnucleus ferior colliculi. The latter is an important relay sta- The aqueduct is surrounded by the peri- tion for the pupillary reflex (p. It fibers of the optical tract and the fibers of contains a large number of peptidergic neu- the occipital cortical fields terminate here. The mesencephalic nucleus of the across the epithalamic commissure to the trigeminal nerve (A7) lies laterally to it, and Edinger–Westphal nucleus (accessory ventrallytoitliethenucleusoftheoculomotor oculomotor nucleus). Ventral to the aque- nerve (A8) and the Edinger-Westphal nucleus duct are the Darkshevich’s nucleus (B26) and (accessory oculomotor nucleus) (A9) the interstitial nucleus (of Cajal) (B27), the (p. Dorsally to both nuclei runs relay stations in the system of the medial the posterior longitudinal fasciculus longitudinal fascicle (p. The main nucleus of the teg- nucleus situated further orally are impor- mentum is the red nucleus (AB11) (p. The essential synapses for (among others, the dentatorubral fasciculus) the rotation of the body around its longi- (A12). At its medial margin descend fiber tudinal axis lie in the interstitial nucleus, bundles of the oculomotor nerve (A13) in those for raising the head and upper body in ventral direction. Superior Colliculi, Pretectal Region 135 222 111 444 555 333 161616 777 888 666 999 101010 202020 111111 171717 181818 222 444 444 141414 555 333 151515 999 161616 131313 202020 777 888 121212 191919 111111 141414 151515 121212 171717 A Cross section through the mid- 181818 brain at the level of the superior 131313 colliculi 191919 222222 212121 161616 232323 252525 Planes of sections 666 262626 272727 111111 232323 252525 202020 262626 272727 161616 242424 191919 282828 B Cross section though the mid- brain at the level of the pretectal region Kahle, Color Atlas of Human Anatomy, Vol. The tracts of the substantia nigra form reaches from the oral part of the pons (A2) only loose pathways of fine fibers rather to the pallidum (AB3) in the diencephalon. Both nuclei are important relay stations of the extrapyramidal system (p. Afferent connections terminating in the anterior part Red Nucleus (A, B)! Fibers of the caudate nucleus, strionigral The nucleus (AB4) appears reddish in a fasciculus (B12) fresh brain section (high iron content,! It consists of the parvocellular corticonigral fibers (B13) neorubrum and the magnocellular paleoru- Afferent connections terminating in the brum situated ventrocaudally. Fibers of the precentral cortex (areas 4 dentate nucleus (B6) of the cerebellum and 6) (B15) runs in the superior cerebellar peduncle Efferent connections and terminates in the contralateral red nucleus. The tectorubral tract (B7) of the superior compact part to the striatum colliculus terminates in the ipsilateral! Fibers of the reticular part, running to the and contralateral paleorubrum. The pallidorubral tract (B8) consists of The majority of efferent fibers ascend to the pallidotegmental bundles from the inner striatum, to which the substantia nigra is segment of the pallidum. In the axons of the dopaminer- tal and precentral cortex terminates in gic nigral neurons (compact part), dopamine the ipsilateral red nucleus. The rubroreticular and rubro-olivary substantia nigra and the striatum (caudate fibers (B10) run in the central tegmental nucleus and putamen); cranial and caudal tract (p. The rubrospinal tract (B11) (poorly cleus and putamen are under the control of developed in humans) crosses in Forel’s massive input from totally different neocor- tegmental decussation and terminates in tical zones (B17). The red nucleus is nigra is of special importance for the control a relay and control station for cerebellar, of involuntary coordinated movement and pallidal, and corticomotor impulses that are the rapid onset of movement (starter func- important for muscle tone, posture, and loco- tion). Injury to this nucleus causes passive tremor, and loss of coordinated movement tremor (shaking), changes in muscle tone, andfacialexpression(masklikeexpressionof and choreic-athetoid hyperactivity. Red Nucleus, Substantia Nigra 137 44 33 22 11 1717 A Positions of red nucleus and 1515 substantia nigra in the brain stem, lateral view 1818 1313 99 88 1212 33 77 1414 44 1616 11 55 66 1010 B Connecting tracts of red nucleus and substantia nigra 1111 C Melanin-containing pigment cells of the substantia nigra Kahle, Color Atlas of Human Anatomy, Vol. Laterally to the sella turcica, they penetrate the dura mater, run through the Nerves III, IV, and VI) roof and then through the lateral wall of the cavernous sinus, and enter the orbit Abducens Nerve (C, E) through the superior orbital fissure.

It can also be shown in experimental animals undergoes a magnetic resonance imaging (MRI) study that a destructive lesion of the lateral vestibular nucleus re- of the brain purchase midamor 45 mg free shipping arterial ulcer. The study demonstrates a large area of lieves the rigidity on that side midamor 45 mg with visa arrhythmia lasting hours. An area is said to have a mo- tract tor function if Rubrospinal Reticulospinal tract tract • Stimulation using very low current strengths elicits Medullary movements. Pontine Cervical • Destruction of the area results in a loss of motor func- tion. Some cortical areas fulfill all of these criteria and have exclusively motor functions. Other areas fulfill only some of the criteria yet are involved in movement, particularly volitional movement. Distinct Cortical Areas Participate Lumbar in Voluntary Movement The primary motor cortex (MI), Brodmann’s area 4, fulfills all three criteria for a motor area (Fig. The supple- mentary motor cortex (MII), which also fulfills all three cri- teria, is rostral and medial to MI in Brodmann’s area 6. Other areas that fulfill some of the criteria include the rest of Brodmann’s area 6; areas 1, 2, and 3 of the postcentral Medially Laterally descending descending system system FIGURE 5. The vestibu- lospinal and reticulospinal tracts influence mo- tor neurons that control axial and proximal limb muscles. The rubrospinal tract influences motor neurons controlling distal limb muscles. Somatosensory input provides information about the position and movement of one part of the body with re- spect to others. The vestibular system provides information about the position and movement of the head and neck with respect to the external world. Vision provides both types of information, as well as information about objects in the external world. Visual and vestibular reflexes interact to produce coordinated head and eye movements associ- ated with a shift in gaze. Vestibular reflexes and so- matosensory neck reflexes interact to produce reflex changes in limb muscle activity. The quickest of these compensations occurs at about twice the latency of the monosynaptic myotatic reflex. The extra time reflects the ac- tion of other neurons at different anatomic levels of the nervous system. Area 4 is the primary IN MOTOR CONTROL motor cortex (MI); area 6 is the premotor cortex and includes the supplementary motor area (MII) on the medial aspect of the The cerebral cortical areas concerned with motor function hemisphere; area 8 influences voluntary eye movements; areas 1, exert the highest level of motor control. It is difficult to for- 2, 3, 5, and 7 have sensory functions but also contribute axons to mulate an unequivocal definition of a cortical motor area, the corticospinal tract. CHAPTER 5 The Motor System 101 gyrus; and areas 5 and 7 of the parietal lobe. All of these ar- Neurons in MI encode the capability to control muscle eas contribute fibers to the corticospinal tract, the efferent force, muscle length, joint movement, and position. This cortical area corre- projects to MI via the red nucleus and ventrolateral thala- sponds to Brodmann’s area 4 in the precentral gyrus. Other afferent projections come from the nonspecific is structured in six well-defined layers (I to VI), with layer I nuclei of the thalamus, the contralateral motor cortex, and being closest to the pial surface. Thalamic afferent fibers terminate in two lay- between the precentral (motor) and postcentral (so- ers; those that carry somatosensory information end in matosensory) gyri and many connections to the visual cor- layer IV, and those from nonspecific nuclei end in layer I. Because of their connections with the so- Cerebellar afferents terminate in layer IV. Efferent axons matosensory cortex, the cortical motor neurons can also arise in layers V and VI to descend as the corticospinal respond to sensory stimulation. Body areas are represented in an orderly manner, as vating a particular muscle may respond to cutaneous stim- somatotopic maps, in the motor and sensory cortical areas uli originating in the area of skin that moves when that (Fig 5. Those parts of the body that perform fine muscle is active, and they may respond to proprioceptive movements, such as the digits and the facial muscles, are stimulation from the muscle to which they are related. Through these connections, the motor Low-level electrical stimulation of MI produces twitch- cortex can control the flow of somatosensory information like contraction of a few muscles or, less commonly, a sin- to motor control centers. Slightly stronger stimuli also produce responses The close coupling of sensory and motor functions may in adjacent muscles.

However discount 45 mg midamor otc blood pressure medication urination, it may be that every link in that cardiovascular control in exercise is complex and the chain taking oxygen from the atmosphere to the mito- unique buy midamor 45mg fast delivery heart attack zine. During strenuous exercise, sympathetic drive can begin to limit vasodilation in active muscle. When exer- Area mL/min % mL/min % cise is prolonged in the heat, increased skin blood flow and Splanchnic 1,400 24 300 1 sweating-induced reduction in plasma volume both con- Renal 1,100 19 900 4 tribute to the risk of hyperthermia and hypotension (heat ex- Brain 750 13 750 3 haustion). Although chronic exercise provides some heat ac- Coronary 250 4 1,000 4 climatization, even highly trained people are at risk for Skeletal muscle 1,200 21 22,000 86 hyperthermia and hypotension if work is prolonged and wa- Skin 500 9 600 2 ter is withheld in demanding environmental conditions. Muscle blood flow increases relative to the resting condition, as does cardiac output, but the higher mean intramuscular pressure limits these flow increases much more than when exercise is rhythmic. Initially, the blood flow increase is blunted inside a statically contract- motor cortex is activated: The total neural activity is ing muscle, the fruits of hard work with too little oxygen roughly proportional to the muscle mass and its work in- appear quickly: a shift to anaerobic metabolism, the pro- tensity. This neural activity communicates with the cardio- duction of lactic acid, a rise in the ADP/ATP ratio, and fa- vascular control centers, reducing vagal tone on the heart tigue. Maintaining just 50% of the MVC is agonizing after (which raises heart rate) and resetting the arterial barore- about 1 minute and usually cannot be continued after 2 ceptors to a higher level. A long-term sustainable level is only about 20% of lactic acid is formed in actively contracting muscles, which maximum. These percentages are much less than the equiv- stimulates muscle afferent nerves to send information to the alent for dynamic work, as defined in terms of maximal oxy- cardiovascular center that increases sympathetic outflow to gen uptake. Rhythmic exercise requiring 70% of the maxi- the heart and systemic resistance vessels. However, despite mal oxygen uptake can be maintained in healthy this muscle chemoreflex activity, within these same work- individuals for about an hour, while work at 50% of the ing muscles, low PO2, increased nitric oxide, vasodilator maximal oxygen uptake may be prolonged for several hours prostanoids, and associated local vasoactive factors dilate (see Fig. The reliance on anaerobic metabolism in isometric exer- Increased sympathetic drive does elevate heart rate and car- cise triggers muscle ischemic chemoreflex responses that diac contractility, resulting in increased cardiac output; lo- raise blood pressure more and cardiac output and heart rate cal factors in the coronary vessels mediate coronary va- sodilation. Increased sympathetic vasoconstrictor tone in the renal and splanchnic vascular beds, and in inactive mus- cle, reduces blood flow to these tissues. Blood flow to these 4 inactive regions can fall 75% if exercise is strenuous. In- creased vascular resistance and decreased blood volume in these tissues helps maintain blood pressure during dynamic exercise. In contrast to blood flow reductions in the viscera 3 and in inactive muscle, the brain autoregulates blood flow at constant levels independent of exercise. The skin re- mains vasoconstricted only if thermoregulatory demands are absent. Exhaustion is predictable on the basis of relative demand upon the maximal oxygen uptake. The Isometric importance of these factors is clear in patients with heart 140 transplants who lack extrinsic cardiac innervation. Stroke volume rises in cardiac transplant patients with increasing exercise intensity as a result of increased venous return that enhances cardiac preload. In addition, circulating epineph- 120 rine and norepinephrine from the adrenal medulla and nor- Dynamic epinephrine from sympathetic nerve spillover augment heart rate and contractility. Stroke volume, in con- 80 trast, reaches a plateau in moderate work and is unchanged as exercise reaches its maximum intensity (see Table 30. Rest 1 hand 1 arm 2 arms 1 leg 2 legs This plateau occurs in the face of ever-shortening filling Muscle mass time, testimony to the increasing effectiveness of the mech- anisms that enhance venous return and those that promote FIGURE 30. Sympathetic stimulation decreases pressures during dynamic exercise occur when an intermediate left ventricular volume and pressure at the onset of cardiac muscle mass is involved; pressure continues to rise in isometric relaxation (as a result of increased ejection fraction), lead- exercise as more muscle is added. Even in untrained individuals, the ejection fraction (stroke volume as a percentage of end-diastolic volume) reaches 80% in less than in dynamic work (Fig. This response results from the combination of a ocardial oxygen demands. These demands are met by a lin- small, dilated active muscle mass with powerful central ear increase in coronary blood flow during exercise that can sympathetic vasoconstrictor drive.

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