Anatomy: Pelvis 2024 PDF

ANATOMY. PELVIC GIRDLE Dr Viktoriia Yerokhina, Lecturer in Medical Sciences [email protected]  LEARNING OUTCOMES ANAT.28 - Pelvis/Walls ANAT.28.01 - Name the bones of the pelvis girdle. ANAT.28.02 - Review the comp...

ANATOMY. PELVIC GIRDLE Dr Viktoriia Yerokhina, Lecturer in Medical Sciences [email protected]  LEARNING OUTCOMES ANAT.28 - Pelvis/Walls ANAT.28.01 - Name the bones of the pelvis girdle. ANAT.28.02 - Review the components of the hip (innominate) bone. ANAT.28.03 - Identify the bony landmarks of the pelvis which can be palpated on the body surface or palpates per vagina or per rectum. ANAT.28.04 - Summarize the main features of the sacrum. ANAT.28.05 - Describe the sacroiliac joints and their ligamentous support. ANAT.28.06 - Explain the importance of the sacrospinous and sacrotuberous ligaments in preventing rotation of the sacrum at the sacroiliac joints. ANAT.28.07 - Review the openings in the bony pelvis, major structures passing through these openings, with which spaces these openings communicate. ANAT.28.08 - Compare and contrast the major differences between the male and female bony pelvis. ANAT.28.09 - Describe the following dimensions of the birth canal: pelvis inlet, conjugate (antero-posterior) diameter, interspinous distance and pelvis outlet. ANAT.28.10 - Define the boundaries of the "true" and "false" pelvis. ANAT.28.11 - Describe the general attachments, innervations and actions of the muscles of the pelvic wall. ANAT.28.12 - Name the muscles that make up the pelvic diaphragm. ANAT.28.13 - Discuss the attachments, innervations, blood supply and general function of the levator ani muscle. ANAT.28.14 - Describe the puborectalis muscle and explain how fecal incotinence could result from injury of the muscle. ANAT.28.15 - Describe the urogenital hiatus in the pelvic floor and compare the major structures passing through the hiatus in males and females. ANAT.28.16 - Summarize the peritoneal reflections from the abdominal wall down to the pelvic cavity and the pouches of the peritoneal cavity in the male and female pelvis. ANAT.28.17 - Explain how bleeding in the upper abdomen (such as from the liver or spleen lacerations) can reach the pelvic peritoneal pouches. ANAT.28.18 - Identify, in radiological images, the major parts of the bony pelvis. ANAT.31.04 - List the ventral rami contributing to the sacral plexus and describe the relationship of this plexus to the piriformis muscle. ANAT.31.05 - Name terminal branches of the sacral plexus.  OVERVIEW OF THE PELVIS Pelvis (pelvic girdle) consists of the left and right hip bones and the sacrum, and coccyx. These bones are firmly connected by the pubic symphysis anteriorly and the sacrococcygeal and sacroiliac joints posteriorly. Sacrum and coccyx are part of the axial skeleton and are actually variably fused vertebrae. In female, the pelvis accommodates the birth canal and therefore is larger and wider than in male individuals. Bony pelvis: 1. Right hip bone (os coxae dextrum) 2. Left hip bone (os coxae sinistrum) 3. Sacrum 4 4. Coccyx  FUNCTIONS OF THE PELVIC GIRDLE Transmits body weight from the axial skeleton to the lower extremities Provides attachment to a large number of muscles; Contains and protects the abdominopelvic and pelvic viscera.  OVERVIEW OF THE PELVIS Linea terminalis forms the pelvic inlet, divides pelvis into: greater pelvis, which contains the small and large intestine, lesser pelvis, which contains the urinary bladder, the male and female internal genital organs and the rectum.  OVERVIEW OF THE PELVIS Greater pelvis (false pelvis) – located superiorly. Provides support of the lower abdominal viscera (such as the ileum and sigmoid colon). Has little obstetric relevance. Lesser pelvis (true pelvis) – located inferiorly. Within the lesser pelvis reside the pelvic cavity and pelvic viscera. Pelvic cavity is the space within the pelvic girdle; it contains abdominal and pelvic organs, protected by the pelvic girdle. OVERVIEW OF THE PELVIS  PELVIC INLET Definition: plane that separates the abdominal and pelvic cavities Location: superior rim of the pelvic cavity (upper pelvic aperture) Borders of the pelvic inlet: Posterior – sacral promontory (superior portion of the sacrum) and sacral wings (ala). Lateral – arcuate line on the inner surface of the ilium, and the pectineal line on the superior pubic ramus. Anterior – pubic symphysis. Iliopectineal line = combined arcuate and pectineal lines.  PELVIC INLET Diameters: transverse, oblique, conjugate (anteroposterior), anatomical conjugate, diagonal, straight, median Structures passing through: ureter, spermatic cord, round ligament of the uterus, suspensory ligament of the ovary, median sacral vessels, gonadal vessels, iliolumbar vessels, lumbosacral trunk, sympathetic trunk, obturator nerve.  HIP BONE – OS COXAE Hip bone consists of 3 fused bones: ilium, ischium and pubis. 3 bones are fused together (synostosis) at a cup-shaped hollow on the outer aspect of the bone called acetabulum. Hip bone is a large irregular bone which articulates in front with the corresponding bone of the opposite side. Posteriorly, two hip bones articulate with the sacrum. 1. Ilium (os ilium) 2. Ischium (os ichii) 3. Pubis (os pubis)  In ancient dining, an acetabulum (Greek: ὀξίς, ὀξύβαφον, ὀξυβάφιον) was a vinegar-cup, which, from the fondness of the Greeks and Romans for vinegar, was probably always placed on the table at meals to dip the food in before eating it. HIP BONE – OS COXAE  HIP BONE – OS COXAE Unlike many bones that gain their names because of perceived similarities to common objects. Os coxae resembles no common objects and thus has earned the informal name innominate – the ‘bone with no name’. Os coxae differs in males and females – demands of locomotion and birthing.  ILIUM (OS ILIUM) Ilium is the most superior component of the hip bone. It consists of two main parts: Body, Ala (wing). 1. Body is the smaller, inferior part of the bone that contributes to the formation of the acetabulum, 2. Ala is the superior expanded part and presents four borders and three surfaces.  ILIUM (OS ILIUM) Components of the ala of the ilium: 3. Iliac fossa (fossa iliaca) – ventromedial concave fossa, the origin of the iliacus 4. Sacropelvic surface (facies sacropelvica) – medial surface behind and below the iliac fossa 4.1 Auricular surface (facies auricularis) – articulates with the sacrum 4.2 Iliac tuberosity (tuberositas iliaca) – attachment of the posterior interosseous sacro-iliac ligament  ILIUM (OS ILIUM) 5. Gluteal surface (facies glutea) – dorsolateral surface, the origin of the gluteal muscles 5.1 Posterior gluteal line (linea glutea posterior) – border between origins of the gluteus maximus and medius 5.2 Anterior gluteal line (linea glutea anterior) – border between the origins of the gluteus medius and minimus 5.3 Inferior gluteal line (linea glutea inferior) – caudal borderline of the origin of the gluteus minimus.  ILIUM (OS ILIUM) 6. Iliac crest (crista iliaca) – has three lips (lines) for attachment of the abdominal wall muscles – outer lip (labium externum), – intermediate zone (linea intermedia), – inner lip (labium internum)  ILIUM (OS ILIUM) 6.1 Tuberculum of iliac crest (tuberculum iliacum) - bony projection formed by the origin of the gluteus medius 6.2 Anterior superior iliac spine (spina iliaca anterior superior) 6.3 Anterior inferior iliac spine (spina iliaca anterior inferior) 6.4 Posterior superior iliac spine (spina iliaca posterior superior) 6.5 Posterior inferior iliac spine (spina iliaca posterior inferior) 7. Arcuate line (linea arcuata) – part of linea terminalis. Medial aspect of the right hip bone  Dimples of Venus The dimples of Venus exemplified in a painting by Gustave Courbet → → → The Latin name is fossae lumbales laterales (“lateral lumbar indentations”). These indentations are created by a short ligament stretching between the posterior superior iliac spine and the skin. They are ligament stretching ought to be genetic.  Contains: PUBIS - OS PUBIS Small body located anteromedially Two rami, superior pubic ramus and inferior pubic ramus, extending posterollatery from the body. Rami look like the letter ‘K’ from an anterior view.  PUBIS - OS PUBIS 1. Body (corpus ossis pubis) – connects to the pubic symphysis 1.1 Pubic tubercle (tuberculum pubicum) – attachment of the inguinal ligament and superior pubic ligament 1.2 Pubic crest (crista pubica) – insertion of rectus abdominis; origin of pyramidalis 1.3 Symphysial surface (facies symphysialis) – medial surface articulates at the pubic symphysis  PUBIS - OS PUBIS 2. Superior pubic ramus (ramus superior) – forms the ventral 1/3 of the acetabulum 2.1 Obturator crest (crista obturatoria) – located between the pubic tubercle and acetabular notch 2.2 Pecten pubis – forms part of the linea terminalis.  PUBIS - OS PUBIS 3. Inferior pubic ramus (ramus inferior) – forms the ischiopubic ramus with the ramus of the ischium 3.1 Phallic crest (crista phallica) – origin of the erectile bodies of the penis and clitoris.  BONY PELVIS Medial and lateral view on the bony pelvis and its important bony structures  ISCHIUM (OS OSCHII) Posteroinferior part of the hip bone Forms the posterior boundary of the obturator foramen. It consists of two parts: 1. Body (corpus) – thicker dorsal part that forms the dorsal third of the acetabulum 2. Ramus – runs ventrally from the body – forms the ischiopubic ramus with the inferior pubic ramus  ISCHIUM (OS OSCHII) 2.1 Ischial tuberosity (tuber ischiadicum) – palpable when the thigh is flexed at the hip joint 2.2 Lesser sciatic notch (incisura ischiadica minor) – forms the lesser sciatic foramen with the sacrospinous and sacrotuberous ligaments 2.3 Ischial spine (spina ischiadica) – border between the greater and lesser sciatic notches.  COMMON FEATURES OF THE HIP BONE 1. Acetabulum – articular fossa of the hip joint composed of all 3 hip bones. 2. Obturator foramen (foramen obturatum) – surrounded by the ischium and pubis 3. Greater sciatic notch (incisura ischiadica major) – together with the sacrospinous and sacrotuberous ligaments forms the greater sciatic foramen 4. Ischiopubic ramus (ramus ischiopubicus) – caudal border of the obturator foramen formed by the ramus of the ischium and the inferior pubic ramus 5. Iliopubic ramus (eminentia iliopubica) – insertion of the psoas minor – transition of the arcuate line into the pecten pubis. HIP BONE  STRUCTURE OF ACETABULUM 1.1 Acetabular margin (limbus acetabuli) – elevated ridge around the acetabulum 1.2 Acetabular notch (incisure) – caudal notch on the acetabular margin 1.3 Lunate surface (facies lunata) - articular surface of the acetabulum – ends caudally at the acetabular notch 1.4 Acetabular fossa (fossa acetabuli) – filled with a fat pad.  Sacrum and coccyx For information on the sacrum and coccyx, please revise 1st Year lecture “Back. Vertebral column.”  SACRO-ILIAC JOINT – ARTICULATIO SACROILIACA Amphiarthrosis (joint that has limited mobility) between the sacrum and ilium that allows only very limited movements. Function: establishes the angle of inclination of the pelvis and transmits force between the pelvis and vertebral column.  SARO-ILIAC JOINT ARTICULATIO SACROILIACA 1. Type: simple 2. Shape: plane 3. Articular surfaces: 3.1 Auricular surface of sacrum 3.2 Auricular surface of ilium 4. Capsule: short and firm 5. Ligaments: 5.1 Anterior, posterior and interosseous sacro-iliac ligament (l. sacroiliacum anterius, posterius et interosseum) 6. Movements: limited translational movements.  SYNARTHROSES OF THE PELVIC GIRDLE Pubic symphysis (symphisis pubica) - cartilaginous joint uniting the two pubic bones in the midline. Hormonal changes occurring during pregnancy loosen the cartilage, preparing the pelvis for parturition.  SYNDESMOSES OF THE PELVIC GIRDLE 2. Obturator membrane (memebrana obturatioria) – covers the obturator foramen; contains a small opening, obturator canal, for the obturator vessels and nerve Content: 1.1 Obturator nerve 1.2 Obturatory artery and veins  SYNDESMOSES OF THE PELVIC GIRDLE 3. Sacrospinous ligament (l. sacrospinale) – runs from the ischial spine to the sacrum and coccyx – closes the greater sciatic notch forming greater sciatic foramen 4. Sacrotuberous ligament (l. sacrotuberale) – runs from the ischial tuberosity to the sacrum and coccyx – closes the lesser sciatic notch forming lesser sciatic foramen SYNDESMOSES OF THE PELVIC GIRDLE DIFFERENCES BETWEEN THE MALE AND FEMALE PELVIS DIFFERENCES BETWEEN THE MALE AND FEMALE PELVIS Differences seen on X-ray between the female (a) and male (b) pelvis: 1. Female inlet is more circular, male more heart-shaped 2. Female subpubic angle is wide (90–120 degrees), male is narrower (60–90 degrees) 3. Female sacrum is wider and flatter 4. Female ischial spines are further apart (not shown). DIFFERENCES BETWEEN THE MALE AND FEMALE PELVIS DIFFERENCES BETWEEN THE MALE AND FEMALE PELVIS SEX DIFFERENCES IN THE GREATER SCIATIC NOTCH # 1 – typical female morphology, # 5 – typical male DIFFERENCES BETWEEN THE MALE AND FEMALE PELVIS  CLINICAL CORRELATION Traumatic pelvic fractures are complex injuries with many bone fragments. Injury of the pelvic organs and vascular plexuses leads to large blood loss (3–4 liters) and hypovoalemic shock. X-RAY PELVIS (AP VIEW) The right hemipelvis is displaced superiorly, compatible with disruption of the sacroiliac joint (indicated by dashed lines and double-headed arrow). Bilateral pubic ramus fractures are also present (indicated by arrowheads).  PELVIC FORM Gynecoid (most common female form): transverse oval inlet, wide sacrum, wide sacrosciatic notch, straight side walls, wide subpubic angle Android (most common male form): triangular inlet, converging side walls, narrow sacrosciatic notch, narrow subpubic angle Anthropoid (common in male individuals): long anterior-posterior diameters, short transverse diameters, wide sacrosciatic notch, narrow subpubic angle Plateylpelloid (flat variation of gynecoid type): short anterior-posterior diameters, long transverse diameters, narrow sacrosciatic notch, wide subpubic angle.  INNERVATION OF LOWER LIMB Lower limb is innervated by branches of the lumbosacral plexus. Lumbosacral plexus: network of nerves composed of two distinct plexuses Lumbar plexus: formed by the subcostal nerve (T12) and first four lumbar nerves (L1–L4) Sacral plexus: formed by the last two lumbar nerves (L4–L5) and the first four sacral nerves (S1–S4) Lumbosacral trunk Formed by the fusion of lumbar nerves L4 and L5 Contributes to the sacral plexus.  SACRAL PLEXUS - PLEXUS SACRALIS (L4–S4) Sacral plexus arises from the spinal nerves of S1 to S4 and receives contributing branches from L4 and L5 via the lumbosacral trunk (truncus lumbosacralis). Located on the pelvic surface of the sacral bone. Along with the lumbar plexus it provides somatomotor and somatosensory innervation for the lower limb.  SACRAL PLEXUS - PLEXUS SACRALIS (L4–S4) Nerves of the sacral plexus: 1. Superior gluteal nerve (n. gluteus superior) 2. Inferior gluteal nerve (n. gluteus inferior) 3. Posterior cutaneous nerve of thigh (n. cutaneus femoris posterior) 4. Pudendal nerve (n. pudendus) 5. Sciatic nerve (n. ischiadicus) Piriformis divides the greater sciatic foramen into the suprapiriform foramen and the infrapiriform foramen  SACRAL PLEXUS - PLEXUS SACRALIS (L4–S4) 1. Superior gluteal nerve (n. gluteus superior) – L4–S1 – runs through the suprapiriform foramen with superior gluteal artery and veins – innervates gluteus medius, gluteus minimus and tensor fasciae latae 2. Inferior gluteal nerve (n. gluteus inferior) – L5–S2 – runs through the infrapiriform foramen with the inferior gluteal artery and veins – innervates gluteus maximus.  CLINICAL CORRELATION Disorders of the superior gluteal nerve lead to an impairment in abduction of the hip joint. Walking and standing on one foot become difficult and patients develop a duck-like gait. Trendelenburg sign is positive. It is demonstrated by asking the patient to stand on the affected leg; the unsupported side of the pelvis will drop lower than the side the patient is standing on.  CLINICAL CORRELATION Paresis of the inferior gluteal nerve results in impaired function of the gluteus maximus, limiting extension of the hip joint → difficulties in walking upstairs.  SACRAL PLEXUS - PLEXUS SACRALIS (L4–S4) 3. Posterior cutaneous nerve of thigh / posterior femoral cutaneous nerve (n. cutaneus femoris posterior) – S1–S3 – runs through the infrapiriform foramen – provides somatosensory innervation to the dorsal thigh, – distally travels with the cranial extension of the small saphenous vein 3.1 Inferior clunial nerve (nervi clunium inferiores) – provides somatosensory innervation to the distal part of the gluteal region 3.2 Perineal branches (rami perineales) – provide somatosensory innervation to the perineal skin.  SACRAL PLEXUS - PLEXUS SACRALIS (L4–S4) 4. Pudendal nerve (nervus pudendus) – S2–S4 will be mentioned in the lecture ‘Perineum’ 5. Sciatic nerve (nervus ischiadicus) – L5–S2 with contributions from L4 and S3. It will be mentioned in the lecture ‘Thigh’. REFERENCES