Pelvis & Perineum Flashcards
What are the bones of the pelvis?
sacrum & coccyx
What is the false (greater) pelvis?
upper part of the pelvis located above the pelvic brim
What is the true (lesser) pelvis?
lower part of the pelvis located below the pelvic brim
What is the function of the false pelvis?
Supports the intestines (specifically, the ileum and sigmoid colon) and transmits part of their weight to the anterior wall of the abdomen
Which pelvis contains the pelvic inlet & outlet?
true
What is the pelvic inlet?
- Space between the greater and lesser pelvis
- Space where a baby’s head enters the pelvis during birth
Is the pelvic inlet or outlet bigger?
inlet
What is the pelvic outlet?
- Located at the end of the lesser pelvis
- Space where the baby’s head emerges from the pelvis
What are the borders of the pelvic outlet? (PITS)
- ant: pubic arch
- lat: ischial tuberosity & sacrotuberous lig.
What are the borders of the pelvic inlet? (PIS)
- ant: pubic symphysis
- lat: iliopectineal line
- post: sacral promontory
What is the pelvic inlet composed of?
- promontory
- ala
- iliopectineal line -> linea terminalis (arcuate line) & pectin pubis (pectineal line)
- symphysis pubis
What are the characteristics of the male pelvis?
- Android pelvis
- Longer sacrum
- Narrower pubic arch -> about 70 degrees
What are the characteristics of the female pelvis?
- Gynaecoid pelvis
- Greater pelvic outlet -> adapted to aid the process of childbirth
- Wider and broader
- Less prominent ischial spines
- higher arch -> about 90 degrees
What are the 2 primary joints of the pelvis?
sacro-iliac & pubic symphysis
What are the 4 articulations within the pelvis?
- 2 sacroiliac joints: between the ilium and the sacrum
- Sacrococcygeal symphysis: between the sacrum and the coccyx
- Pubic symphysis: between the pubis bodies of the two hip bones
What are the 3 ligaments of the pelvis?
- posterior sacroiliac ligament: supports the sacroiliac joint
- the sacrospinous ligament: spans the sacrum to the ischial spine
- the sacrotuberous ligament: spans the sacrum to the ischial tuberosity
How is the greater sciatic notch & foramen formed?
by the sacrospinous and sacrotuberous ligaments in the lateral wall of the pelvis
What are the structures passing through the greater sciatic foramen? (SNIP NIP)
- sciatic nerve, sup. gluteal v. & n.
- nerve to obturator internus
- inf. gluteal v. & n.
- piriformis muscle, post. cutaneous n. of thigh
- nerve to quadratus femoris
- int. pudendal art. & n.
- pudendal n.
What are the structures passing through the lesser sciatic foramen? (PINT)
- pudendal nerve
- internal pudendal artery & vein
- nerve to obturator internus muscle
- tendon of the obturator internus muscle
What are the 4 walls of the pelvis?
- anterior formed by Pubic bones, pubic rami, pubis symphysis
- 2 lateral formed by Obturator internus, piriformis muscles Sacrotuberous lig., sacrospinous lig, obturator membrane, pelvic surface of hip bone below the pelvic inlet
- posterior formed by Sacrum, coccyx, piriformis m.
What 2 muscles form the pelvic wall?
piriformis & obturator internus
What are the characteristics of the piriformis muscle?
- originates from the sacrum and passes through the greater sciatic foramen
- rotates the femur during hip extension and abducts the femur during hip flexion.
What are the characteristics of the obturator internus muscle?
- originates within the pelvis and continues as a flattened tendon through the lesser sciatic foramen
- provides hip mobility, external rotation of the hip
What are the major apertures in the pelvic wall?
- the obturator canal
- the greater sciatic foramen
- the lesser sciatic foramen
What does the pelvic floor divide into?
pelvic cavity & perineum
What are the functions of the pelvic floor?
- Urinary and fecal continence
- “floor” for the abdominopelvic viscera
What are the 2 gaps in the pelvic floor?
- Urogenital hiatus–> an anteriorly situated gap, allows passage of the urethra (and the vagina in females)
- Rectal hiatus (anal hiatus)–> a centrally positioned gap, allows passage of the anal canal
What are the 2 muscles of the pelvic diaphragm?
levator anni muscle & coccygeus muscle
What are the 3 parts of the levator anni muscle?
- puborectalis -> related to fecal continencesd
- pubococcygeus
- iliococcygeus
What is the main intermediate part of the levator anni that is usually torn?
pubococcygeus
What causes a prolapse in males?
- pressure of obesity
- chronic constipation
- constant coughing
Where do the somatic nerves of the pelvis arive from?
lumbosacral&coccygeal plexus
Where does the obturator nerve arise from?
lumbar plexus
Is the obturator nerve a pelvic nerve?
no
What nerve provides sensory information to theexternal genitaliaas well muscular branches toperinealmuscles?
pudendal
What type of nerves are responsible for parasympathetic, sympathetic, and somatic?
- parasympathetic -> pelvic nerve
- sympathetic -> hypogastric nerve
- somatic -> pudendal nerve
Which autonomic nerve is responsible for the inhibition of peristalsis & muscle contraction of genital organs during orgasm?
sympathetic
What is the major artery of the pelvis?
internal iliac
What are the branches of the posterior trunk of the pelvis?
- iliolumbar art.
- lateral sacral art.
- superior gluteal art.
What are the branches of the anterior trunk trunk of the pelvis?
- obturator art.
- umbilical art.
- superior vesical art.
- vaginal art.
- uterine art.
- middle rectal art.
- internal pudendal art.
- inferior gluteal art.
What are the functions of the perineum?
Micturition, defecation, intercourse, & vaginal delivery
What are the boundaries of the perineum?
- Pubic symphysis -> anteriorly
- ischiopubic rami -> anterolateral
- Sacrum and coccyx -> posteriorly
- Ischial tuberosities -> laterally
- sacrotuberous lig. -> posterolateral
- Pelvic diaphragm -> roof
- perineal skin -> the floor
What is the perineal membrane?
covers the anterior part of the pelvic outlet and is perforated by the urethra in both sexes and by the vagina of the female
What is the perineal body?
an irregular fibromuscular mass located in the median plane between the anal canal and the perineal membrane
What are the contents of the anal triangle?
- Analaperture: the opening of the anus
- External anal sphincter muscle: voluntary muscle responsible for opening and closing the anus
- Ischioanal fossae (x2): spaces located laterally to the anus, filled with fat tissue
What is the function of the anal canal within the anal triangle?
defecation& maintaining fecal continence
What happens to the anal canal during defecation?
the anal canal is collapsed by the internal and external anal sphincters to prevent the passage of fecal material
Which anal sphincter is involuntary & which is voluntary?
- Internal anal sphincter(involuntary)
- External anal sphincter (voluntary)
What is the blood supply above & below the pectinate line?
- above -> superior rectal art.
- below -> inferior rectal art.
What are the contents of the urogenital triangle in a female?
mons pubis, labia majora, labia minora, the clitoris, the vaginal and urethral orifices
What are the contents of the urogenital triangle in a male?
the bulb of the penis, the scrotum, serves as a point of attachment for the penis
What is the space between the perineal membrane & the levator anni?
deep perineal pouch
What are the contents in the deep perineal pouch?
- External urethral sphincter
- Urethra
- Deep transverse perineal muscles
- bulbourethral glands (in male)
- Vagina (in female)
What are the contents in the superficial perineal pouch?
- Erectile tissues that form the penis and clitoris
- Bulbospongiosus muscle
- Ischiocavernosus muscles
- Superficial transverse perineal muscle
What acts as a tear resistant body between the vagina & the external anal sphincter in females?
perineal body
Damage to what can lead to prolapse of uterus in the female?
perineal body
What is theterminal branch of the anterior division of theinternal iliac artery?
internal pudendal art.
What are the branches of the pudendal nerves?
- perineal -> superficial & deep perineal
- inferior rectal
- dorsal nerve of the clitoris (penis)
What is the pathway of the pudendal nerve?
exits from the greater sciatic foramen, travels around the ischial spine, and passes through the lesser sciatic foramen
What is a common cause of pudendal nerve entrapment?
prolonged cycling on an incorrectly positioned or improperly shaped bicycle seat (cyclist syndrome)
What is the purpose of the pudendal nerve block?
providing analgesia for the 2nd stage of labor & to provide anesthesia of the perineum
A tear in the pelvic diaphragm leads to paralysis of which muscles?
levator ani
