1. Defining the pelvic region Flashcards
What is the articulated pelvis?
The four bones that together (including the ligaments) make the pelvis (os coxa)
What makes up the articulated pelvis?
- Two innominate bones: ilium, ischium and pubis
- Sacrum, formed by fusion of the 5 sacral vertebrae
- Coccyx, formed by the fusion of the 4 coccygeal vertebrae
What are some key features of the articulated pelvis?
L5 Sacrum Coccyx Posterior sacral foramina Sacrococcygeal joint intervertebral disc sacroiliac joint pubic symphysis (interpubic disc and ligaments)
What are the ligaments of the pelvis and which bones do they articulate?
Sacroiliac - between sacrum and ileum (has anterior and posterior components)
Sacrococcygeal - between the sacrum and coccyx
Sacrospinous - between the ischial spine and sacrum/coccyx
Sacrotuberous - posterior to sacrospinous, between lateral aspect of sacrum and coccyx onto medial margin of ischial tuberosity
What is the perineum?
The perineum is the space located at the pelvic outlet
inferior to the pelvic diaphragm (muscles of the pelvic floor)
Can be used to describe the narrow region between the thighs.
Diamond-shaped surface extending from the mons pubis (in females) to the medial surface of the thighs and posterior to the gluteal folds
How can the perineum be split and what is the perineal body?
The perineum can be split into two triangles by a transverse line joining the two ischial tuberosities
- urogenital triangle
- anal triangle
The perineal body is the midpoint of this line
The perineal body is where several sphincter and perineal pouch muscles converge
List key features of the pelvis when viewed from beneath
Pubic symphysis Inferior pubic ramus Obturator foramen Pubic arch Inferior pubic ligament Ischial tuberosity Perineal membrane
Describe the deep perineal pouch
The space enclosed in part by the perineum, superior to the perineal membrane
What are the contents of the deep perineal pouch?
Urethra
Vagina (in females)
Glands, such as bulbourethral (Cowper) glands in males
Perineal muscles that act as sphincters e.g. compressor urethrae or urethrovaginal sphincter in females
What is enclosed by the superficial perineal pouch?
Urethra
Vagina in females, root of penis in males
Glands such as Bartholin in females (equivalent to Cowper glands in males)
Perineal muscles that provide support to the external genitalia, such as the bulbospongiosus or ischiocavernosus muscles
Name two glands which are the equivalent of each other in either sex
Bulbourethral (Cowper) glands in males
Bartholin glands in females
Joints of the articulated pelvis
sacroiliac, sacrococcygeal, pubic symphysis
What forms the pelvic rim aka the pelvic inlet
Promontory and ala (wing) of sacram
Right and left linea terminalis made up of the arcuate lines and the pectineal lines
What are the borders of the true pelvic cavity?
Posterior - sacrum/coccyx Anterior - pubic symphysis Inferior - pelvic floor Superior - pelvic brim Lateral - obturator internus muscle
What are the contents of the true pelvic cavity?
Reproductive organs/tracts
Bladder
Rectum
List the pelvic musculature
Muscles lining the wall: - piriformis - obturator internus Muscles lining the floor: - coccygeus - levator ani (iliococcygeus, pubococcygeus and puborectalis)
Describe the pelvic wall
Formed by piriformis and obturator internus
Piriformis:
origin - anterior surface of sacrum, through the greater sciatic foramen (over ischial spine) into greater trochanter of femur (insertion)
Obturator internus:
origin - internal surface of the obturator membrane, through the lesser sciatic foramen (below ischiatic spine) inserts onto the greater trochanter of femur
What can you see from a superior view of the pelvic floor?
Tendinous arch Urethra Vagina puborectalis muscle (most medial) pubococcygeus muscle iliococcygeus muscle (most lateral) coccygeus muscle piriformis muscle (most posterior) Coccyx
What can you see from the inferior view of the pelvic floor that you can’t see from the superior view?
Sacrospinous ligament
Sacrotuberous ligament
Where does the coccygeal muscle go?
From the ischial spine to the inferior end of the sacrum & coccyx
Where does the iliococcygeus muscle go?
From the tendinous arch to the annococcygeal body
What is the tendinous arch?
Line extending from the ischial spine to the posterior aspect of the pubic bone
Where does the pubococcygeus muscle go?
From the posterior aspect of the pubic bone and inserting to the coccyx (lateral fibres) or merging with the contralateral medial fibres
Where does the puborectalis muscle go?
a continuous muscle originating from the posterior aspect of the pubic bone and slinging behind the rectum
What muscles make up the levator ani?
puborectalis, pubococcygeus, ileococcygeus
List and describe the pelvic arteries
Anterior division of the internal iliac which provides several branches e.g. uterine, vesical or internal pudendal
Gonadal, from abdominal aorta, supplying the gonads
List and describe the pelvic veins
Internal iliac to common iliac veins
Gonadal, to IVC or L renal vein
Describe the somatic plexuses of the pelvis
Somatic plexuses (L4-Co) subdivided into:
- lumbosacral (L4-S4 (joined by lumbar L4/5))
- Coccygeal (S4-Co)
Function as motor or sensory e.g. sciatic nerve, sup/inf gluteal, pudendal nerve
Describe the visceral plexuses of the pelvis
Paravertebral/prevertebral
Sympathetic/parasympathetic/visceral fibres
Erection/Ejavulation e.g. inferior hypogastric plexus
Lumbosacral trunk
superior gluteal
inferior gluteal
sciatic
pudendal
Visceral plexuses
Paraysympathetic flow: pelvic splanchnic nerves (S2-S4)
Sympathetic flow: sacral sympathetic trunk; superior and inferior hypogastric plexuses
Posterior pelvis nerves (gluteal)
sciatic nerve
pudendal nerve
gluteal vessels (superior and inferior)
Pudendal nerve
dorsal nerve of clitoris
deep perineal nerve
superficial perineal nerve
pudendal nerve (nearsacrotubular ligament)
