Anatomy 26 Flashcards
What are some functions of the bony pelvis?
Supporting the spine, torso and upper body
Locomotion
Housing and protecting the pelvic viscera
What 3 bones make up the bony pelvis?
Sacrum
Left and Right Hip (innominate) bones
What 3 bones is the hip bone composed of?
Ilium
Ischium
Pubis
How many articulations does the bony pelvis have?
5
What are the 5 articulations of the bony pelvis?
Hip joint
Sacroiliac joint
Pubic symphysis
Lumbosacral joint
Sacrococcygeal joint
What is the hip joint?
Between the head of the femur and the acetabulum (socket) of the pelvis
What bones fuse at the acetabulum?
Ilium, ischium and pubis of the hip bone
Where is the sacroiliac joint located?
Between the sacrum and the ilium of the hip bone
Where is the pubic symphysis located?
Between the 2 pubic bones
What movement occurs at the pubic symphysis?
Almost no movement
Where is the lumbosacral joint located?
Between the 5th lumbar vertebrae and the sacrum
What lies between the 5th lumbar vertebrae and the sacrum?
An intervertebral disc
Where is the sacrococcygeal joint?
Between the sacrum and coccyx
What does the intercristal line mark?
Level of the L4/L5 disc space
What is the clinical relevance of the intercristal line?
It’s the position where a lumbar puncture can be performed or an epidural injection given
What is the Anterior superior iliac spine (ASIS)?
Most anterior point of the ilium and is palpable in most people
What is the iliac tubercle?
The most lateral point of the ilium
What does the intertubercular line mark?
Marks the division of the lower third of the abdomen from the middle third, thereby delineating the suprapubic region from the umbilical, and the iliac fossae from the flanks
What is the pubic tubercle?
Most medial point of the pubic bone
Where is the inguinal ligament located?
Runs from the anterior superior iliac spine to the pubic tubercle
What is the mid-inguinal point?
The mid-point of a line drawn from the anterior superior iliac spine to the pubic symphysis
Which artery is palpable at the mid-inguinal point?
Femoral artery
What is McBurney’s point?
Marks the approximate location of the base of the appendix
What are features of a females pelvic inlet?
Wider
Circular
What are features of a males pelvic inlet?
Narrower
Heart shaped
What angle is formed by the inferior pubic rami in females?
Obtuse (>90˚) angle
What angle is formed by the inferior pubic rami in males?
Acute angle (<90˚)
What feature does the sacrum in females have?
Wider and shorter sacrum
What feature does the sacrum in males have?
Narrower, longer sacrum
What organs does the pelvis contain in females?
- Organs of the gastrointestinal and genitourinary systems, including the rectum and bladder
- The uterus, ovaries and vagina
What organs does the pelvis contain in males?
- Organs of the gastrointestinal and genitourinary systems, including the rectum and bladder
- The prostate and seminal vesicles
What arteries supply the pelvis?
Left and right internal iliac arteries
What do the internal iliac arteries give rise to?
Several branches in the pelvis that supply the pelvic viscera
What do some branches of the internal iliac arteries exit the pelvis to supply?
The perineum and gluteal region
What are some key branches of the internal iliac arteries?
Vesical arteries
Uterine and vaginal arteries
Middle rectal artery
Internal pudendal artery
Superior and inferior gluteal arteries
What do the vesical arteries supply?
Supply the bladder in both sexes, and the prostate and seminal vesicles in males
What does the middle rectal artery supply?
Rectum
What does the internal pudendal artery supply?
Exits the pelvis to supply the perineum
What do the superior and inferior gluteal arteries supply?
Exit the pelvis to supply the gluteal (buttock) region
What do the venous plexuses in the pelvis unite and drain into?
Internal iliac vein
What types of nerves supply the structures of the pelvis?
Somatic, parasympathetic and sympathetic nerves
What nerves arise from the sacral plexus?
Sciatic nerve
Pudendal nerve
Superior and inferior gluteal nerves
Pelvic splanchnic nerve
What is the sciatic nerve formed by?
Lower lumbar and sacral spinal nerves L4-S3
What does the sciatic nerve supply?
Lower limbs
What nerves is the pudendal nerve derived from?
Spinal nerves S2-S4
What region is the pudendal nerve a major nerve of?
Perineum
What does the superior and inferior gluteal nerves supply?
Exit the pelvis and innervate the gluteal region
What does the pelvic splanchnic nerve carry?
Parasympathetic fibres from the S2-S4 spinal cord segments to the pelvic viscera
Where are sympathetic fibres that innervate the pelvic viscera derived from?
Lumbar splanchnic nerve
What is the pelvic floor?
Collective name for several muscles that support the pelvic organs from below
What are the 3 primary functions of the pelvic floor?
- Prevent herniation of the pelvic organs inferiorly, out of the pelvis
- Control continence of urine and faeces by providing a sphincter action on the urethra and rectum respectively
- Aid in increasing intra-abdominal pressure
What 2 muscles make up the pelvic floor?
Levator ani and coccygeus
What 3 paired muscles make up the levator ani?
Puborectalis
Pubococcygeus
Iliococcygeus
What is the puborectalis?
U-shaped muscle attaches to the pubic bones anteriorly and forms a sling around the rectum
How does the puborectalis prevent defecation?
It pulls on the rectum so that a sharp angle is formed between the rectum and anal canal
What does the puborectalis contribute to?
Control of micturition
Which is the most anterior levator ani muscle?
Puborectalis
Where is the pubococcygeus located in relevance to the puborectalis?
Posterior and lateral to it
What is the pubococcygeus attached to?
Pubic bone anteriorly, and the coccyx and sacrum posteriorly
Where is the iliococcygeus located in relevance to the pubococcygeus?
Lateral to it
What does the iliococcygeus attach to?
Spines of the ischium
What is the levator ani innervated by?
Branch of the S4 nerve and by some branches of the pudendal nerve (from S2-S4)
What can pelvic floor weakness lead to?
- Incontinence of urine or faeces
- It can also lead to pelvic organ prolapse where the uterus prolapses into the vagina, or the rectum prolapses out of the anus, because they are no longer supported
What structure is found superficial and inferior to the pelvic floor?
Perineum
What is the perineum?
The superficial region between the pubic symphysis and the coccyx, and between the medial surfaces of the thighs
What can the perineum be split into?
2 triangles
Anal triangle (posteriorly)
Urogenital triangle (anteriorly)
What does the anal triangle contain?
Contains the opening of the anus and the external anal sphincter
What are the layers of the urogenital triangle?
Skin
Perineal fascia
Superficial perineal pouch
Perineal membrane
Deep perineal pouch
What is the skin in the urogenital triangle?
The urethra and vagina open out through the skin
What is the perineal fascia in the urogenital triangle?
A continuation of the fascia overlying the abdominal wall muscles
What is the superficial perineal pouch in the urogenital triangle?
A potential space that contains the erectile tissues of the penis or clitoris and also 3 muscles
What 3 muscles are found in the superficial perineal pouch?
Ischiocavernosus, bulbospongiosus and the superficial transverse perineal muscles
What is the perineal membrane?
A strong fibrous membrane that provides support for the attachment of ischiocavernosus and bulbospongiosus.
- It has specific holes in it for the urethra and vagina
What is the deep perineal pouch?
A potential space between the perineal membrane and the pelvic floor muscles
What does the deep perineal pouch contain?
Parts of the vagina, urethra and the external urethral sphincter
Where does the perineal body sit?
Between the two triangles of the perineum
What is the function of the perineal body?
Acts as an attachment for almost all the perineal and pelvic floor muscles, including levator ani, the external anal sphincter, the external urethral sphincter, the superficial and deep transverse perineal muscles and bulbospongiosus
What are the parts of the corpora cavernosa that are attached to the ischial ramus known as?
‘Crura’ (singular: crus), which means ‘legs’, so ‘crura of the clitoris’ and ‘crura of the penis’ refer to the parts of the corpora cavernosa that are attached to the ischial rami
What is the bulb of the penis?
Expanded part of the corpus spongiosum which rests on the perineal membrane
In females what does the corpus spongiosum split into?
2 parts that flank the vaginal opening and they also rest on the perineal membrane, either side of the vaginal opening, these are the bulb of the vestibule (or bulb of the clitoris)
What is the corpora cavernosa covered by?
Ischiocavernosus muscles
What is the corpus spongiosum covered by?
Bulbospongiosus muscle
What is the function of the ischiocavernosus?
Helps stabilise the erect penis and clitoris
What does the bulbospongiosus in males assist in?
Maintaining erection by compressing the veins that drain erectile tissues and it contracts to squeeze any
remaining urine or semen from the urethra
What does the bulbospongiosus in females assist it?
Helps maintain clitoral erection and constricts around the vaginal orifice which can help expression of fluid from the greater vestibular glands
What is the arterial supply to the perineum?
Via the internal pudendal artery
What is the internal pudendal artery a branch of?
The internal iliac artery
What is the main nerve that innervates muscles in the perineum and skin of the external genitalia?
Pudendal nerve (S2-S4)
How do the internal pudendal artery and pudendal nerve arise in the pelvis?
They travel through the greater and lesser sciatic foramina of the pelvis
What type of nerves innervate the perineal structures in addition to the pudendal nerve?
Autonomic nerves
What is a episiotomy?
Pre-emptive incision during labour made just lateral to the perineal body
What is the clinical importance of an episiotomy?
Avoids injury to the perineal body or an uncontrolled tear through the anal sphincter
