Micturition: Detailed Anatomy Renal System > Anatomy > Anatomy

Total Page:16

File Type:pdf, Size:1020Kb

Micturition: Detailed Anatomy Renal System > Anatomy > Anatomy Micturition: Detailed Anatomy Renal System > Anatomy > Anatomy MICTURITION: DETAILED ANATOMY OVERVIEW KEY INNERVATION PATTERNS Parasympathetic ACTIVATION • Parasympathetic nervous system ACTIVATES urination via: - Detrusor muscle activation - Internal urethral sphincter inhibition. Sympathetic INHIBITION • Sympathetic nervous system INHIBITS urination via: - Detrusor muscle inhibition - Internal urethral sphincter activation Somatomotor INHIBITION • Somatomotor system INHIBITS urination via: - External urethral sphincter activation DETAILED ANATOMY & PHYSIOLOGY ANATOMICAL STRUCTURES The major functional structures of the lower urinary system are: 1 / 4 • The urinary bladder. • The urethra. • The bladder wall muscle: the detrusor muscle. • The internal urethral sphincter. • The external urethral sphincter. • The ureters, which empty into the bladder. SYMPATHETIC NERVOUS SYSTEM Origins • The sympathetic preganglionic system originates in the intermediolateral cell column from T12 – L2. • Along the descending aorta, lies the inferior mesenteric ganglion (the lowermost prevertebral ganglion). Innervation • There is supraspinal innervation of the intermediolateral cell column, from which excitatory sympathetic efferents project to the inferior mesenteric prevertebral ganglion. PARASYMPATHETIC NERVOUS SYSTEM Origins • The parasympathetic preganglionic system originates in the intermediolateral cell column of S2 – S4 and involves the parasympathetic vesical ganglia along the bladder wall. Innervation • There is supraspinal innervation of the intermediolateral cell column, from which excitatory parasympathetic efferents project to the parasympathetic vesical ganglia via the pelvic splanchnic nerve. SOMATOMOTOR EFFERENTS Origins • Within the S2 – S4 spinal cord slice, in the anterior horn of the spinal cord, lies Onuf 's nucleus (aka nucleus of Onufrowicz). Innervation • There is supraspinal innervation of Onuf's nucleus, and excitatory somatomotor fibers project from Onuf's nucleus to the external urethral sphincter within the pudendal nerve, which inhibits urination. 2 / 4 PARASYMPATHETIC ACTIONS • Postganglionic parasympathetic fibers excite the bladder wall, which contracts to expel urine. • Postganglionic parasympathetic fibers inhibit the internal urethral sphincter: - Inhibition of the sphincter allows urine to empty the bladder. SYMPATHETIC ACTIONS • Postganglionic sympathetic fibers inhibit the detrusor muscle: - Inhibition of the detrusor inhibits urination. • Postganglionic sympathetic fibers inhibit the parasympathetic vesical ganglia: - Inhibition of this ganglia inhibits urination. • Postganglionic sympathetic fibers excite the internal urethral sphincter: - Prevents bladder emptying. SUMMARY POINTS OF URINARY INNERVATION Primary Urination Regulators • The main regulators are the detrusor muscle, internal urethral sphincter, and external urethral sphincter. • Sympathetic fibers inhibit bladder wall contraction and excite internal urethral sphincter constriction, which inhibits urination. • Parasympathetic fibers excite bladder wall contraction and inhibit internal urethral sphincter constriction, which promotes urination. • Somatomotor efferents provide tonic activation of the external urethral sphincter, which inhibits urination. SUPRASPINAL CONTROL SUPRASPINAL CONTROL OF URINATION Overview • The pontine micturition (bladder emptying) and continence (bladder filling) command centers and innervate the preganglionic parasympathetic and sympathetic spinal cord regions and Onuf's nucleus. Anatomy 3 / 4 • The pontine micturition center lies in the medial (M) region of the dorsolateral pontine tegmentum and the pontine continence center lies ventro-lateral to it in the lateral (L) region. Afferent Innervation • These regions receive afferents from many brain regions, including the periaqueductal gray area, the hypothalamus, cerebellum, and certain limbic system regions. - Barrington first described the pontine micturition center, so it is often referred to as the Barrington nucleus. PERIPHERAL NERVE INNERVATION PERIPHERAL NERVE INNERVATION Now, let's conclude with the peripheral nerves that carry the aforementioned autonomic and somatic fibers. From proximal to distal, • Postganglionic thoracolumbar sympathetic fibers initially travel within the superior hypogastric plexus • And then emerge as the hypogastric nerve. It is the transition zone between the superior and inferior hypogastric plexuses. • Both the hypogastric and pelvic splanchnic nerves join within the inferior hypogastric plexus (aka the pelvic plexus), which provides both sympathetic and parasympathetic innervation to the bladder and urethra. • They then pass into the vesical plexus. Powered by TCPDF (www.tcpdf.org) 4 / 4.
Recommended publications
  • Variations of Thoracic Splanchnic Nerves and Its Clinical Implications
    Int. J. Morphol., 23(3):247-251, 2005. Variations of Thoracic Splanchnic Nerves and its Clinical Implications Variaciones de los Nervios Esplácnicos Torácicos y sus Implicancias Clínicas *Tony George Jacob; ** Surbhi Wadhwa; ***Shipra Paul & ****Srijit Das JACOB, G. T.; WADHWA, S.; PAUL, S. & DAS, S. Variations of thoracic splanchnic nerves and its clinical implications. Int. J. Morphol., 23(3):247-251, 2005. SUMMARY:The present study reports an anomalous branching pattern of the thoracic sympathetic chain. At the level of T3 ganglion, an anomalous branch i.e accessory sympathetic chain (ASC) descended anteromedial to the main sympathetic chain (MSC). The MSC and the ASC communicated with each other at the level of T9, T10 and T11 ganglion, indicating the absence of classical pattern of greater, lesser and least splanchnic nerves on the right side. However, on the left side, the sympathetic chain displayed normal branching pattern. We opine that the ASC may be representing a higher origin of greater splanchnic nerve at the level of T3 ganglion and the branches from MSC at T9, T10 and T11 ganglion may be the lesser and least splanchnic nerves, which further joined the ASC (i.e presumably the greater splanchnic nerve) to form a common trunk. This common trunk pierced the right crus of diaphragm to reach the right suprarenal plexus after giving few branches to the celiac plexus. Awareness and knowledge of such anatomical variants of thoracic sympathetic chain may be helpful to surgeons in avoiding any incomplete denervation or preventing any inadvertent injury during thoracic sympathectomy. KEY WORDS: Splanchnic nerves; Sympathetic chain; Trunk thoracic; Ganglion.
    [Show full text]
  • Anatomical Planes in Rectal Cancer Surgery
    DOI: 10.4274/tjcd.galenos.2019.2019-10-2 Turk J Colorectal Dis 2019;29:165-170 REVIEW Anatomical Planes in Rectal Cancer Surgery Rektum Kanser Cerrahisinde Anatomik Planlar Halil İbrahim Açar, Mehmet Ayhan Kuzu Ankara University Faculty of Medicine, Department of General Surgery, Ankara, Turkey ABSTRACT This review outlines important anatomical landmarks not only for rectal cancer surgery but also for pelvic exentration. Keywords: Anorectal anatomy, pelvic anatomy, surgical anatomy of rectum ÖZ Pelvis anatomisini derleme halinde özetleyen bu makale rektum kanser cerrahisi ve pelvik ezantrasyon için önemli topografik noktaları gözden geçirmektedir. Anahtar Kelimeler: Anorektal anatomi, pelvik anatomi, rektumun cerrahi anatomisi Introduction Surgical Anatomy of the Rectum The rectum extends from the promontory to the anal canal Pelvic Anatomy and is approximately 12-15 cm long. It fills the sacral It is essential to know the pelvic anatomy because of the concavity and ends with an anal canal 2-3 cm anteroinferior intestinal and urogenital complications that may develop to the tip of the coccyx. The rectum contains three folds in after the surgical procedures applied to the pelvic region. the coronal plane laterally. The upper and lower are convex The pelvis, encircled by bone tissue, is surrounded by the to the right, and the middle is convex to the left. The middle main vessels, ureters, and autonomic nerves. Success in the fold is aligned with the peritoneal reflection. Intraluminal surgical treatment of pelvic organs is only possible with a projections of the lower boundaries of these folds are known as Houston’s valves. Unlike the sigmoid colon, taenia, good knowledge of the embryological development of the epiploic appendices, and haustra are absent in the rectum.
    [Show full text]
  • The Diaphragm
    Thomas Jefferson University Jefferson Digital Commons Regional anatomy McClellan, George 1896 Vol. 1 Jefferson Medical Books and Notebooks November 2009 The Diaphragm Follow this and additional works at: https://jdc.jefferson.edu/regional_anatomy Part of the History of Science, Technology, and Medicine Commons Let us know how access to this document benefits ouy Recommended Citation "The Diaphragm" (2009). Regional anatomy McClellan, George 1896 Vol. 1. Paper 13. https://jdc.jefferson.edu/regional_anatomy/13 This Article is brought to you for free and open access by the Jefferson Digital Commons. The Jefferson Digital Commons is a service of Thomas Jefferson University's Center for Teaching and Learning (CTL). The Commons is a showcase for Jefferson books and journals, peer-reviewed scholarly publications, unique historical collections from the University archives, and teaching tools. The Jefferson Digital Commons allows researchers and interested readers anywhere in the world to learn about and keep up to date with Jefferson scholarship. This article has been accepted for inclusion in Regional anatomy McClellan, George 1896 Vol. 1 by an authorized administrator of the Jefferson Digital Commons. For more information, please contact: [email protected]. 320 THE DIAPHRAGJ1I. The nerves from the four upp e1' ganglia are quite small, and pass inward to join the cardiac and posterior pulmonary plexuses. The nerves from the six lower ganglia constitute the greater, the lesser, and the smaller splanchnic nerves. The great splanchnic nerue is composed of the most numerous filaments from the fifth, sixth, seventh, eighth, ninth, and tenth ganglia, which combine into a single trunk, and, passing through the crus of the diaphragm on the corresponding side, join the solar, renal, and supra-renal plexuses.
    [Show full text]
  • 35-40 Institute of Normal Anatomy
    35 Lymphology 28 (1995) 35-40 Institute of Normal Anatomy (PP,AT), Institute of Histology and General Embryology (CM), and Department of Human Pathology (RS), University of Pavia, Italy ABSTRACT light and electron microscopy (2,3). To clarify vesical lymph drainage, we now examined the After endoscopic transurethral biopsies of fine structure of small lymphatic vessels (SL V) normal human urinary bladder, an extensive and their distribution in the normal human network of small initial lymphatic vessels was urinary bladder. Particular attention was depicted by means of light and electron directed to the structure and composition of microscopy. Using light microscopy, lymphatic the connective matrix that surrounds the vessels were seen in the mucosa and lymphatic vessels in the different regions of submucosa and formed a complex network in the bladder wall. the detrusor muscular coat. These lymphatics were characterized by an irregular and MATERIALS AND METHODS attenuated wall and increased in number and size from the superficial to the deeper region of Ten male subjects (40 to 60 years of age) the bladder. Ultrastructurally, the lymphatic who had symptoms of bladder outlet wall was characterized by endothelial cells obstruction were utilized for this investigation. joined together end-to-end or by complicated Two endoscopic transurethral biopsies from interdigitations. Often intercellular channels the lateral wall of the normal urinary bladder and gaps between two contiguous endothelial were performed under a constant bladder cells were present. A broad network of elastic distention after introduction of physiological and collagen fibers joined the lymphatic saline at 50 cm H20 constant pressure. The endothelial wall to the neighboring connective biopsy trocar was regulated to obtain vesical tissue.
    [Show full text]
  • Detailed and Applied Anatomy for Improved Rectal Cancer Treatment
    REVIEW ARTICLE Annals of Gastroenterology (2019) 32, 1-10 Detailed and applied anatomy for improved rectal cancer treatment Τaxiarchis Κonstantinos Νikolouzakisa, Theodoros Mariolis-Sapsakosb, Chariklia Triantopoulouc, Eelco De Breed, Evaghelos Xynose, Emmanuel Chrysosf, John Tsiaoussisa Medical School of Heraklion, University of Crete; National and Kapodistrian University of Athens, Agioi Anargyroi General and Oncologic Hospital of Kifisia, Athens; Konstantopouleio General Hospital, Athens; Medical School of Crete University Hospital, Heraklion, Crete; Creta Interclinic, Heraklion, Crete; University Hospital of Heraklion, Crete, Greece Abstract Rectal anatomy is one of the most challenging concepts of visceral anatomy, even though currently there are more than 23,000 papers indexed in PubMed regarding this topic. Nonetheless, even though there is a plethora of information meant to assist clinicians to achieve a better practice, there is no universal understanding of its complexity. This in turn increases the morbidity rates due to iatrogenic causes, as mistakes that could be avoided are repeated. For this reason, this review attempts to gather current knowledge regarding the detailed anatomy of the rectum and to organize and present it in a manner that focuses on its clinical implications, not only for the colorectal surgeon, but most importantly for all colorectal cancer-related specialties. Keywords Anatomy, rectum, cancer, surgery Ann Gastroenterol 2019; 32 (5): 1-10 Introduction the anal verge [AV]) to a given landmark (e.g., the part from the sacral promontory) [1]. This study can be considered as Even though rectal anatomy is considered by most indicative of the current overall knowledge on rectal anatomy clinicians to be a well-known subject, it is still treated as a hot across CRC-related specialties.
    [Show full text]
  • A Narrative Review on the Impact of Nerve Sparing Surgery on Urinary Function in Pelvic Surgery for Endometriosis
    5 Review Article Page 1 of 5 A narrative review on the impact of nerve sparing surgery on urinary function in pelvic surgery for endometriosis Beth Leopold1, Jordan S. Klebanoff2, Sara Rahman3, Sofiane Bendifallah4,5,6, Jean Marc Ayoubi7, Gaby N. Moawad3 1Department of Obstetrics and Gynecology, Mount Sinai Medical Center, New York, NY, USA; 2Department of Obstetrics and Gynecology, Main Line Health, Wynewood, PA, USA; 3Department of Obstetrics and Gynecology, The George Washington University Hospital, Washington, DC, USA; 4Department of Gynaecology and Obstetrics, Tenon University Hospital, Assistance Publique des Hôpitaux de Paris (AP-HP), Sorbonne University, Paris, France; 5UMRS-938, Sorbonne University, Paris, France; 6Groupe de Recherche Clinique 6 (GRC6-Sorbonne Université): Centre Expert En Endométriose (C3E), France; 7Department of Obstetrics and Gyncology and Reproductive Medicine, Hopital Foch, Faculté de Médecine Paris Ouest (UVSQ), Suresnes, France Contributions: (I) Conception and design: B Leopold, JS Klebanoff, GN Moawad; (II) Administrative support: None; (III) Provision of study materials or patients: B Leopold, JS Klebanoff, S Rahman, GN Moawad; (IV) Collection and assembly of data: All authors; (V) Data analysis and interpretation: All authors; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors. Correspondence to: Gaby N. Moawad, MD. Department of Obstetrics & Gynecology, The George Washington University Hospital, 2150 Pennsylvania Ave NW, Washington, DC 20037, USA. Email: [email protected]. Abstract: Endometriosis is an all too common benign inflammatory condition that impacts the lives of countless women around the world. Not only is there typically a delay in diagnosis of this devastating condition, but women are often mismanaged until they reach a provider with expertise in the condition.
    [Show full text]
  • Clinical and Functional Anatomy of the Urethral Sphincter
    Review Article International Neurourology Journal Int Neurourol J 2012;16:102-106 http://dx.doi.org/10.5213/inj.2012.16.3.102 pISSN 2093-4777 · eISSN 2093-6931 INJ Clinical and Functional Anatomy of the Urethral Sphincter Junyang Jung, Hyo Kwang Ahn, Youngbuhm Huh Department of Anatomy, Kyung Hee University School of Medicine, Seoul, Korea Continence and micturition involve urethral closure. Especially, insufficient strength of the pelvic floor muscles including the urethral sphincter muscles causes urinary incontinence (UI). Thus, it is most important to understand the main mechanism causing UI and the relationship of UI with the urethral sphincter. Functionally and anatomically, the urethral sphincter is made up of the internal and the external sphincter. We highlight the basic and clinical anatomy of the internal and the external sphinc- ter and their clinical meaning. Understanding these relationships may provide a novel view in identifying the main mechanism causing UI and surgical techniques for UI. Keywords: Urethral sphincters; Pudendal nerve; Autonomic nervous system; Urinary incontinence; Urination INTRODUCTION tomical damage to the ligaments, facial support, and pelvic floor musculature, including the levator ani [8]. The pudendal nerve The urethral sphincter is crucial for the maintenance of urinary innervating the EUS is susceptible to injury during vaginal birth continence [1,2]. The urethral sphincter refers to one of the fol- because it travels between the sacrospinous and sacrotuberous lowing muscles [3]: 1) the internal urethral sphincter (IUS), ligaments [9]. In this article, we discuss the basic and clinical which consists of smooth muscle and is continuous with the anatomy of the urethral sphincter and the relationship between detrusor muscle and under involuntary control, and 2) the ex- the urethral sphincter and UI.
    [Show full text]
  • The Neuroanatomy of Female Pelvic Pain
    Chapter 2 The Neuroanatomy of Female Pelvic Pain Frank H. Willard and Mark D. Schuenke Introduction The female pelvis is innervated through primary afferent fi bers that course in nerves related to both the somatic and autonomic nervous systems. The somatic pelvis includes the bony pelvis, its ligaments, and its surrounding skeletal muscle of the urogenital and anal triangles, whereas the visceral pelvis includes the endopelvic fascial lining of the levator ani and the organ systems that it surrounds such as the rectum, reproductive organs, and urinary bladder. Uncovering the origin of pelvic pain patterns created by the convergence of these two separate primary afferent fi ber systems – somatic and visceral – on common neuronal circuitry in the sacral and thoracolumbar spinal cord can be a very dif fi cult process. Diagnosing these blended somatovisceral pelvic pain patterns in the female is further complicated by the strong descending signals from the cerebrum and brainstem to the dorsal horn neurons that can signi fi cantly modulate the perception of pain. These descending systems are themselves signi fi cantly in fl uenced by both the physiological (such as hormonal) and psychological (such as emotional) states of the individual further distorting the intensity, quality, and localization of pain from the pelvis. The interpretation of pelvic pain patterns requires a sound knowledge of the innervation of somatic and visceral pelvic structures coupled with an understand- ing of the interactions occurring in the dorsal horn of the lower spinal cord as well as in the brainstem and forebrain. This review will examine the somatic and vis- ceral innervation of the major structures and organ systems in and around the female pelvis.
    [Show full text]
  • Regulation of Bladder Storage and Voiding Involves Both Sympathetic
    Center for Advanced Gyn 5530 Wisconsin Ave Suite 914 Chevy Chase, MD 20815 301-652-1231 Regulation of bladder www.centerforadvancedgyn.com storage and voiding involves both sympathetic and parasympathetic control1 BLADDER STORAGE Storage, which makes up the majority of the micturition cycle, is primarily regulated by the sympathetic nervous system via the neurotransmitter, norepinephrine.2 • Norepinephrine, released from the sympathetic nerves, activates the adrenergic receptors (ARs), beta-ARs, and alpha-ARs in the bladder to relax the detrusor muscle and close the internal sphincter, respectively2 β-ARs Norepinephrine Ureter β-AR Norepinephrine binds to β-ARs on Sympathetic the detrusor muscle, resulting in nervous system bladder relaxation α-ARs Urothelium -AR α1 Detrusor muscle Internal sphincter Norepinephrine Urethra Norepinephrine binds to α1-ARs, resulting in the closing of the internal sphincter and increased storage of urine Three different types of b-ARs are expressed in the human bladder: b1-AR, b2-AR, and b3-AR. The b3-AR made up 97% of the total b-AR messenger RNA (mRNA) in bladder tissue samples in an experiment to determine b-AR subtype expression, making it predominantly responsible for detrusor muscle relaxation. The b1-AR and b2-AR subtypes made up 1.5% and 1.4% of the total b-AR mRNA, respectively.3 While b-ARs are expressed on the detrusor muscle, they are also found on the urothelium. These receptors contribute to the regulation of bladder function. During the storage phase, the urothelium stretches in tandem with the bladder wall when the bladder starts filling with urine.4,5 6 Both a1-ARs and a2-ARs are expressed in the lower urinary tract in humans.
    [Show full text]
  • Surgical Anatomy
    1 Surgical Anatomy AnatomiA ChirurgicA Yiannis P Panayiotopoulos, MD, PhD 2 3 systems of organisation 4 INTEGUMENT [sKIN AND sUBCUTANEOUs TISSUes] Surface area= >2m2 Cleavage [crease] lines of Langer Divisions Epidermis Dermis [chorion] [400-2500] thick Stratified epithelium [20-1400 thick] Functions protection sensation secrertion individual characteristics Fascial layers Superficial layer Deep investing fascia Superficial layer Deep layer perimysium Camper's fascia Gruvellier's fscia Scarpa's fascia Colle's fascia [perineum] epimysium [abdomen] [perineum] [abdomen] fascial planes 5 mUsCULOSKeLETAL SYSTem BONES 206 bones axial skeleton appendicular skeleton Functions Protection & support of internal organs Biomechanical levers to produce movement Reservoir for irons Ca, PO4,CO3 Source of platelets red cells, granulocytes Bone composition Osteocytes Collagenous matrix Mineral content [connective tissue cells] Osteoblasts Osteoclasts provides tensile strength provides shear & compressive strength 6 Bone fractures Degree of Compression of Skin torn Nutrient foramina displacement fragments involved comminution compound avascular necrosis displaced not displaced Types of bones Long Flat [squamus] 2 plates of collar bone Diaphysis [shaft] containing spongy diploe Sesamoid Thin, spongy trabecular bone within tendons, to reduce attrition Marrow cavity & increase the lever arm of muscle Thick collar bone [cortical] Metaphysis trabecular bony network Thin cortical bone Epiphysis epiphyseal line epiphyseal disk 7 Bone healing fibroblasts collar of collagen [callus] Calcification Bone resorption Unorganised tissue proliferation [6 weeks] Remodeling [3-6 months] CARTILAGE Dense, irregular connective tissue, almost avascular, with a few living cells. 1. Hyaline [hyaluronic acid, muccopolysaccharides]: anterior portions of ribs and the articular cartilage. 2. Fibrocartilage [muccopolysaccharides, collagen, high content of water]: most symphyses. 3. Elastic [muccopolysaccharides & elastic fibres]: ear, tip of nose ARTICULATIONS 1.
    [Show full text]
  • Name Kingsborough Community
    Name ______________________________ Kingsborough Community College of The City University of New York Biology Department Biology 11 Examination ANS Return to ANS Facts Multiple Choice: use your scantron and darken the space of the letter of the best answer to each question. 1. The autonomic nervous system (ANS) is the motor portion for a. somatic reflexes b. visceral reflexes c. all peripheral reflexes d. skeletal muscular reflexes 2. Autonomic nerve impulses can be in response to sensory input from a. stretch receptors in blood vessels monitoring blood pressure b. stretch receptors in the urinary bladder or large intestine relating to their contents c. any internal receptor monitoring conditions of the tissues and organs d. the eyes, ears or nose sensing a dangerous situation e. any one of the preceding 3. Cytons (cell bodies) of preganglionic sympathetic neurons are located in the a. dorsal horns of gray matter b. anterior horns of gray matter c. lateral horns of gray matter d. pons and medulla oblongata e. S2-S4 segments of the spinal cord 4. Paravertebral ganglia contain cytons of a. parasympathetic postganglionic neurons b. parasympathetic preganglionic neurons c. sympathetic preganglionic neurons d. sympathetic postganglionic neurons 5. The sympathetic chain ganglia are found a. from cervical to coccygeal regions on either side of the vertebral column b. alongside the thoracic region of the vertebral column c. alongside the cervical and sacral regions of the vertebral column d. alongside the lumbar area of the vertebral column e. both b and d 6. Mass activation is a property of the _______ branch of the ANS.
    [Show full text]
  • The Sacral Parasympathetic Innervation of the Colon
    THE SACRAL PARASYMPATHETIC INNERVATION OF THE COLON RUSSELL T. WOODBURNE Department of Anatomy, University of Michigan Hedical School, Ann Arbofi TWO FIGURES Autonomic nerves distribute by a variety of methods. They are recognized as components of all spinal and some cranial nerves, but they also have a strong tendency to exhibit a hitch-hiker relationship to arteries and to other nerves. The perivascular plexuses of the head and neck, and of the thorax and abdomen, are especially typical of peripheral sympa- thetic distribution. In the parasympathetic division, pre- ganglion& arising in the third, seventh, and ninth cranial nerves utilize the branches of the trigeminal nerve for pas- sage to the structure innervated. The vagus nerve is a main parasympathetic route to structures of the neck and chest and its terminal fibers end in the abdomen by mingling in the celiac plexus with sympathetic postganglionic fibers. In- testinal autonomies are perivascular for both sympathetic and parasympathetic divisions. St the brim of the pelvis the perivascular plexus of the aorta forms the hypogastric nerves which descend across the sacral promontory and dis- tribute to the pelvic viscera without following their blood vessels, With these predominantly sympathetic nerves, para- sympathetic fibers pass to the viscera of the pelvis and peri- neum, Anatomical description has recognized that the parasympa- thetic innervation of the descending and sigmoid portions of the large intestine is provided by components of the sacral parasympathetic roots from sacral nerves two, three, and four, which ascend from the pelvis to reach the colon. Implicit 67 68 RUSSELL T. WOODBURNE in most descriptions is an assumption that fibers of this char- acter ascend through the pelvic plexuses, mingle with the nerves of the abdominal portion of the hypogastric plexus, and distribute by means of the perivascular nerve plexuses along the inferior mesenteric artery and its branches.
    [Show full text]