Part 2 book “Clinically oriented anatomy” has contents: Gluteal and posterior thigh regions, pelvic girdle, neurovascular structures of pelvis, sectional imaging of pelvis and perineum, anterior and medial regions of thigh, cranial meninges, pterygopalatine fossa, vestibulocochlear nerve,… and other contents.
6 Pelvis and Perineum INTRODUCTION TO PELVIS AND PERINEUM PELVIC GIRDLE Bones and Features of Pelvic Girdle TABLE 6.1 Comparison of Male and Female Bony Pelves Orientation of Pelvic Girdle Pelvic Girdle Sexual Differences Joints and Ligaments of Pelvic Girdle CLINICAL BOX: Pelvic Girdle PELVIC CAVITY Walls and Floor of Pelvic Cavity TABLE 6.2 Muscles of Pelvic Walls and Floor Peritoneum and Peritoneal Cavity of Pelvis TABLE 6.3 Peritoneal Reflections in Pelvis Pelvic Fascia CLINICAL BOX: Pelvic Cavity NEUROVASCULAR STRUCTURES OF PELVIS Pelvic Arteries TABLE 6.4 Arteries of Pelvis Pelvic Veins Lymph Nodes of Pelvis Pelvic Nerves TABLE 6.5 Somatic Nerves of Pelvis CLINICAL BOX: Neurovascular Structures of Pelvis 1293 PELVIC VISCERA Urinary Organs Rectum TABLE 6.6 Parts of Male Urethra CLINICAL BOX: Urinary Organs and Rectum Male Internal Genital Organs CLINICAL BOX: Male Internal Genital Organs Female Internal Genital Organs CLINICAL BOX: Female Internal Genital Organs Lymphatic Drainage of Pelvic Viscera TABLE 6.7 Lymphatic Drainage of Structures of Pelvis and Perineum PERINEUM Fasciae and Pouches of Urogenital Triangle Features of Anal Triangle TABLE 6.8 Arteries of Perineum CLINICAL BOX: Perineum Male Urogenital Triangle TABLE 6.9 Muscles of Perineum CLINICAL BOX: Male Urogenital Triangle Female Urogenital Triangle TABLE 6.10 Nerves of Perineum CLINICAL BOX: Female Urogenital Triangle SECTIONAL IMAGING OF PELVIS AND PERINEUM Magnetic Resonance Imaging INTRODUCTION PERINEUM TO 1294 PELVIS AND In common usage, the pelvis (L basin) is the part of the body’s trunk that is inferoposterior to the abdomen and is the area of transition between the trunk and the lower limbs The pelvic cavity is the inferiormost part of the abdominopelvic cavity Anatomically, the pelvis is the part of the body surrounded by the pelvic girdle (bony pelvis), part of the appendicular skeleton of the lower limb (Fig 6.1) FIGURE 6.1 Pelvis and perineum A, B The pelvis (green) is the space within the pelvic girdle, overlapped externally by the abdominal and gluteal regions, perineum, and lower back Consequently, the pelvis has no external surface area The greater pelvis (light green) is pelvic by virtue of its bony boundaries but is abdominal in terms of its contents The lesser pelvis (dark green) provides the bony framework (skeleton) for the pelvic cavity and deep perineum The pelvis is subdivided into greater and lesser pelves The greater pelvis is surrounded by the superior pelvic girdle The greater pelvis is occupied by inferior abdominal viscera, affording them protection similar to the way the superior abdominal viscera are protected by the inferior thoracic cage The lesser pelvis is surrounded by the inferior pelvic girdle, which provides the skeletal framework for both the pelvic cavity and the perineum—compartments of the trunk separated by the musculofascial pelvic diaphragm Externally, the pelvis is covered or overlapped by the inferior anterolateral abdominal wall anteriorly, the gluteal region of the lower limb posterolaterally, and the perineum inferiorly 1295 The term perineum1 refers both to the area of the surface of the trunk between the thighs and the buttocks, extending from the coccyx to the pubis, and to the shallow compartment lying deep (superior) to this area but inferior to the pelvic diaphragm The perineum includes the anus and external genitalia: the penis and scrotum of the male and the vulva of the female 1The term perineum has been used in different ways, in different languages, and in different circumstances In its most restricted sense, and in obstetrics, it has been used to refer to the area superficial to the perineal body, between the vulva or scrotum and the anus or to the perineal body itself In an intermediate sense, it has included only the perineal region, a superficial (surface) area bounded by the thighs laterally, the mons pubis anteriorly, and the coccyx posteriorly In its widest sense, as used in Terminologia Anatomica (the international anatomical terminology), and in this book, it refers to the region of the body that includes all structures of the anal and urogenital triangles, superficial and deep, extending as far superiorly as the inferior fascia of the pelvic diaphragm PELVIC GIRDLE The pelvic girdle is a basin-shaped ring of bones that connects the vertebral column to the two femurs The primary functions of the pelvic girdle are to bear the weight of the upper body when sitting and standing transfer that weight from the axial to the lower appendicular skeleton for standing and walking provide attachment for the powerful muscles of locomotion and posture and those of the abdominal wall, withstanding the forces generated by their actions Consequently, the pelvic girdle is strong and rigid, especially compared to the pectoral (shoulder) girdle Other functions of the pelvic girdle are to contain and protect the pelvic viscera (inferior parts of the urinary tracts and the internal reproductive organs) and the inferior abdominal viscera (e.g., intestines), while permitting passage of their terminal parts (and, in females, a full-term fetus) via the perineum provide support for the abdominopelvic viscera and gravid (pregnant) uterus 1296 provide attachment for the erectile bodies of the external genitalia provide attachment for the muscles and membranes that assist the functions listed above by forming the pelvic floor and filling gaps that exist in or around it Bones and Features of Pelvic Girdle In mature people, the pelvic girdle is formed by three bones (Fig 6.2A): FIGURE 6.2 Pelvic girdle A, B Features of the pelvic girdle demonstrated anatomically (A) and radiographically (B) The pelvic girdle is formed by the two hip bones (of the inferior axial 1297 skeleton) anteriorly and laterally and the sacrum (of the axial skeleton) posteriorly C The hip bone is in the anatomical position when the anterior superior iliac spine (ASIS) and the anterior aspect of the pubis lie in the same vertical plane The preadolescent hip bone is composed of three bones—ilium, ischium, and pubis—that meet in the cup-shaped acetabulum Prior to their fusion, the bones are united by a triradiate cartilage along a Y-shaped line (blue) D An adult’s right hip bone in the anatomical position shows the bones when fused (B courtesy of Dr E L Lansdown, Professor of Medical Imaging, University of Toronto, Toronto, ON, Canada.) Right and left hip bones (coxal or pelvic bones): large, irregularly shaped bones, each of which develops from the fusion of three bones (ilium, ischium, and pubis) Sacrum: formed by the fusion of five, originally separate, sacral vertebrae The internal (medial or pelvic) aspects of the hip bones bound the pelvis, forming its lateral walls; these aspects of the bones are emphasized here Their external aspects, primarily involved in providing attachment for the lower limb muscles, are discussed in Chapter 7, Lower Limb As part of the vertebral column, the sacrum and coccyx are discussed in detail in Chapter 2, Back In infants and children, each hip bone consists of three separate bones united by a triradiate cartilage at the acetabulum, the cup-like depression in the lateral surface of the hip bone that articulates with the head of the femur (Fig 6.2B) After puberty, the ilium, ischium, and pubis fuse to form the hip bone The right and left hip bones are joined anteriorly at the pubic symphysis, a secondary cartilaginous joint The hip bones articulate posteriorly with the sacrum at the sacro-iliac joints to form the pelvic girdle The ilium is the superior, fan-shaped part of the hip bone (Fig 6.2B, C) The ala (wing) of the ilium represents the spread of the fan, and the body of the ilium, the handle of the fan On its external aspect, the body participates in formation of the acetabulum The iliac crest, the rim of the fan, has a curve that follows the contour of the ala between the anterior and posterior superior iliac spines The anteromedial concave surface of the ala forms the iliac fossa Posteriorly, the 1298 sacropelvic surface of the ilium features an auricular surface and an iliac tuberosity, for synovial and syndesmotic articulation with the sacrum, respectively The ischium has a body and ramus (L branch) The body of the ischium helps form the acetabulum and the ramus of the ischium forms part of the obturator foramen The large postero-inferior protuberance of the ischium is the ischial tuberosity The small pointed posteromedial projection near the junction of the ramus and body is the ischial spine The concavity between the ischial spine and the ischial tuberosity is the lesser sciatic notch The larger concavity, the greater sciatic notch, is superior to the ischial spine and is formed in part by the ilium The pubis is an angulated bone with a superior ramus, which helps form the acetabulum, and an inferior ramus, which contributes to the bony borders of the obturator foramen A thickening on the anterior part of the body of the pubis is the pubic crest, which ends laterally as a prominent swelling, the pubic tubercle The lateral part of the superior pubic ramus has an oblique ridge, the pecten pubis (pectineal line of the pubis) The pelvis is divided into greater (false) and lesser (true) pelves by the oblique plane of the pelvic inlet (superior pelvic aperture) (Figs 6.1A and 6.2A) The bony edge (rim) surrounding and defining the pelvic inlet is the pelvic brim, formed by the promontory and ala of the sacrum (superior surface of its lateral part, adjacent to the body of the sacrum) a right and left linea terminalis (terminal line) together form a continuous oblique ridge consisting of the: arcuate line on the inner surface of the ilium pecten pubis (pectineal line) and pubic crest, forming the superior border of the superior ramus and body of the pubis The pubic arch is formed by the right and left ischiopubic rami (conjoined inferior rami of the pubis and ischium; Fig 6.2A and C) These rami meet at the pubic symphysis, their inferior borders defining the subpubic angle (Fig 6.3) The width of the subpubic angle is determined by the distance between the right and the left ischial tuberosities This can be measured with the gloved fingers in the vagina during a pelvic examination 1299 FIGURE 6.3 Pelvic girdles of male and female Pubic arches or subpubic angles typical for each gender (male = red; female = green) can be approximated by spreading the index and middle finger (demonstrating narrow subpubic angle of male pelvis) or thumb and index finger (demonstrating wider subpubic angle of female pelvis) The pelvic outlet (inferior pelvic aperture) is bounded by the (Figs 6.1A and 6.2A) pubic arch anteriorly ischial tuberosities laterally inferior margin of the sacrotuberous ligament (running between the coccyx and the ischial tuberosity) posterolaterally tip of the coccyx posteriorly The greater pelvis (false pelvis) is the part of the pelvis (Fig 6.1) superior to the pelvic inlet 1300 bounded by the iliac alae posterolaterally and the anterosuperior aspect of the S1 vertebra posteriorly occupied by abdominal viscera (e.g., the ileum and sigmoid colon) The lesser pelvis (true pelvis) is the part of the pelvis between the pelvic inlet and pelvic outlet bounded by the pelvic surfaces of the hip bones, sacrum, and coccyx that includes the true pelvic cavity and the deep parts of the perineum (perineal compartment), specifically the ischio-anal fossae (Fig 6.1B) that is of major obstetrical and gynecological significance The concave superior surface of the musculofascial pelvic diaphragm forms the floor of the true pelvic cavity, which is thus deepest centrally The convex inferior surface of the pelvic diaphragm forms the roof of the perineum, which is therefore shallow centrally and deep peripherally Its lateral parts (ischio-anal fossae) extend well up into the lesser pelvis The terms pelvis, lesser pelvis, and pelvic cavity are commonly used incorrectly, as if they were synonymous terms Orientation of Pelvic Girdle When a person is in the anatomical position, the right and left anterior superior iliac spines (ASISs) and the anterior aspect of the pubic symphysis lie in the same vertical plane (Fig 6.2B, C) When a pelvic girdle in this position is viewed anteriorly (Fig 6.2A), the tip of the coccyx appears close to the center of the pelvic inlet, and the pubic bones and pubic symphysis constitute more of a weight-bearing floor than an anterior wall In the median view (Fig 6.1A), the sacral promontory is located directly superior to the center of the pelvic outlet (site of the perineal body) Consequently, the curved axis of the pelvis intersects the axis of the abdominal cavity at an oblique angle Pelvic Girdle Sexual Differences Distinction between male and female skeletons is most evident in the pelvic girdle The pelvic girdles of males and females differ in several respects (Fig 6.3; Table 6.1) These sexual differences are related mainly to the heavier build and larger muscles of most men and to the adaptation of the pelvis (particularly the lesser pelvis) in women for parturition (childbearing) Sexual differences 1301 appear during gestation regarding the pubic arch Greater dimensions of the girdle in male but greater volume of the pelvic cavity appear during infancy, with the greatest distinctions developing following puberty See the Clinical Box “Variations in Male and Female Pelves.” Changes in pelvic shape continue throughout life (see Huseynov et al., which provides animations of male and female lifetime changes) TABLE 6.1 COMPARISON OF MALE AND FEMALE BONY PELVES Joints and Ligaments of Pelvic Girdle The primary joints of the pelvic girdle are the sacro-iliac joints and the pubic symphysis (Fig 6.4A) The sacro-iliac joints link the axial skeleton (skeleton of the trunk, composed of the vertebral column at this level) and the inferior appendicular skeleton (skeleton of the lower limb) The lumbosacral and sacrococcygeal joints, although joints of the axial skeleton, are directly related to the pelvic girdle Strong ligaments support and strengthen these joints 1302 pulse taking puncture of right labial inferior superior laryngeal left of leg lingual deep dorsal lobar lower limb deep superficial mammary lateral medial marginal lateral left medial maxillary medial marginal median, of forearm meningeal, middle mesenteric 2773 inferior superior metatarsal, dorsal middle lobe nasal, external oblique, of left atrium obturator occipital ophthalmic inferior superior ovarian palatine palpebral inferior superior pancreatic pancreaticoduodenal parathyroid paratonsillar para-umbilical perforating pericardiacophrenic pharyngeal phrenic inferior superior plantar 2774 plantar digital popliteal portal prepyloric profunda brachii profunda femoris pudendal external internal pulmonary left left inferior left superior right right superior radial rectal inferior middle superior rectosigmoid renal entrapment syndrome left right retromandibular retroperitoneal right 2775 sacral lateral median saphenous accessory cutdown grafts great (long) injury to small (short) saphenous, great (long) segmental sigmoid small saphenous spinal anterior posterior splenic subclavian left puncture of right subcostal sublingual submental supra-orbital suprarenal left 2776 right suprascapular supratrochlear temporal deep middle superficial testicular left right thoracic internal lateral thoraco-acromial thoraco-epigastric thyroid inferior middle superior tibial anterior posterior ulnar umbilical postnatal patency of of upper limb uterine vaginal 2777 valves ventricular, left posterior vorticose Vein(s) (of regions or organs) of abdominal wall anterolateral posterior of anal canal of brain of cervical region, lateral of diaphragm of ductus deferens of duodenum of ejaculatory ducts of face of foot of forearm of hand of heart of kidneys of larynx of liver of lower limb deep superficial of lungs of neck of orbit 2778 of pancreas of pelvis of pericardium of pharynx of pleurae of popliteal fascia of prostate gland of rectum of root of neck of scalp of scrotum of seminal glands of small intestine of spinal cord of spinal nerve roots of stomach of suprarenal glands of teeth of thigh of thoracic wall of thyroid gland of tongue of upper limb of ureters of urethra female male of urinary bladder 2779 of vagina of vertebral column of vulva Vena cavae inferior caval opening groove for magnetic resonance imaging of obstruction of surgical exposure of superior computed tomography of groove for obstruction of radiographic appearance of surface anatomy of surgical exposure of Venous drainage, superficial Venous network dorsal plantar Venous plexuses Venous stasis Venous valves Ventricles of brain 1st 2nd 2780 3rd 4th lateral of heart left right laryngeal Ventricular fibrillation Ventricular septal defects Venules Vertebrae abnormal fusion of aging effects on anomalies of 1022 C7 cervical atypical C1 See (Atlas) C2 See (Axis) C3-C7 C7 characteristics of dislocation of features of typical characteristics of dislocations of fractures of 2781 function of laminae of lumbar abnormal fusion of body of L2 L5 ossification of stenosis of surface anatomy of ossification of pedicles of structure of T4 T5 T6 T8 thoracic facets of features of ossification of spinous processes of T1 superior costal facets of T3 T4 T5 T6 2782 T8 T10 T11 T12 costal facets of variations in vasculature of Vertebral column arteries of cervical curvatures of abnormal normal flexibility of flexion of hyperflexion injury of injuries of joints of ligaments of movements of nerves of regions of rotation of vasculature of veins of Vertebra prominens Vertex Vertigo 2783 Vesicles optic seminal Vessels deep lymphatic Vestibule aortic of bony labyrinth laryngeal of nose oral of vagina Vestibulocochlear View, anteroposterior Villi, intestinal Viscera abdominal innervation of parasympathetic innervation of physiology of sympathetic innervation of of neck alimentary layer endocrine layer respiratory layer pelvic urinary organs pleura 2784 nerves of surface anatomy of of thoracic cavity Visceral afferent fiber Visceral fibers Visceral motor fiber Visceral sensory fiber Viscerocranium Visual fields defects in Volkmann contracture Volvulus Vomer Vulva Vulvar trauma W Wall(s) abdominal See (Abdominal wall) of axilla of bladder capillary of heart of orbit of pelvic cavity of rectus sheath of thorax of vagina Wallerian degeneration 2785 Whiplash White matter White rami communicantes Window oval round Wing greater, of sphenoid of ilium lesser, of sphenoid Wounds palmar arch scalp sole of foot Wrist See also Joints (named), Wrist arteries of articulation of blood supply to bones of capsule of cross-section of fractures of innervation of ligaments of movements of muscles that move synovial cyst of X 2786 X-rays Y Yoke muscles Z Zone orbicular transitional, of lips Zygomatic bone 2787 ... pelvic cavity is the inferiormost part of the abdominopelvic cavity Anatomically, the pelvis is the part of the body surrounded by the pelvic girdle (bony pelvis), part of the appendicular skeleton... fan-shaped part of the hip bone (Fig 6.2B, C) The ala (wing) of the ilium represents the spread of the fan, and the body of the ilium, the handle of the fan On its external aspect, the body participates... cm or greater 1311 13 12 FIGURE B6 .2 In all pelvic girdles, the ischial spines extend toward each other, and the interspinous distance between them is normally the narrowest part of the pelvic canal