Pelvis and Perinuem
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Functions of pelvis
- 1. transmit upper body weight to the lower limbs providing a base for lower lib function
- 2. Support and protect the pelvic viscera
- 3. Form part of the birth canal during delivery
Bony pelvis formed by
- formed by 2 hip bones anteriorly and laterally
- sacrum and coccyx posteriorly
Parts of hip bone
ilium, ischium and pubis
3 parts of hip bones fuse where?
at the acetabulum at about 16 years to form a single bone at about 16 years
- Formed by fusion of 5 sacral vertebral segments
- consists of base, apex, pelvic, dorsal, and lateral surfaces and a sacral canal
Base of sacrum
- upper surface of first sacral vertebra
- articulates with 5th lumbar vertebral body at lumbosacral joint
anterior projecting edge of the body
lateral mass or ala
wide upper part on each side of sacral promontory
four pairs of pelvic sacral foramina that transmit the ventral rami of S1-4
Dorsal surface of sacrum
- contains: median sacral crest, medial sacral crest, four pairs of dorsal sacral foramina, lateral sacral crest
median sacral crest
3 or 4 spinous tubercles. in the middle of the sacrum
Medial sacral crest
four small articular tubercles lateal to median sacral crest.
below the last median sacral spinous tubercles. bounded by the sacral cornua from the medial sacral crests on each side.
dorsal sacral foramina
transmit the dorsal rami of S1-4
Lateral surface of sacrum
- broad upper part with a mostly L-shaped auricular surface that articulates with the ilium at the sacroiliac joint.
- Narrow lower part curves medially to the 5th sacral vertebral body at the inferior lateral sacral angle
Apex of sacrum
narrow, articulates with the base of the coccyx at the sacrococcygeal joint
formed by the sacral vertebral foramina. Downward continuation of the vertebral canal. Four pairs of intervertebral foramina that are continuous with the pelvic and dorsal sacral foramina.
Where does the subarachnoid space end
level of the second sacral vertebra
What does that sacral canal contain?
Contains cauda equina, filum terminale and meninges
What passes through the sacral hiatus
filum terminale and S5 nerves
small triangular bone consisting of 4 fused vertebral segments. 2nds to 4th coccygeal vertebrae decrease in size and are fused bodies
Base of coccyx
upper surface of the 1st coccygeal vertebral body. Articulates with the apex of the sacrum.
project dorsolaterally from coccyx
project superolaterally from coccyx
plane bounded by the pelvic brim. Divided into the greater pelvis and the lesser pelvis
Pelvic brim (linea terminalis)
Extends along the promontory and ala of the sacrum, arcuate line of the ilium, pecten pubis, pubic crest and upper border of the symphysis pubis
located above the pelvic inlet between the iliac bones and is part of the abdominal cavity
sitated below the pelvic inlet and forms the pelvic cavity or simply the pelvis
diamond-shaped area extending from the symphysis pubis anteriorly tot eh coccyx posteriorly. Bound on each side by the ischiopubic ramus, ischiopubic ramus, ischial tuberosity and sacrotuberous ligament
Maximum diameter of inlet in female
transverse diameter is 13.5 cm
maximum diameter of outlet in female
anteroposterior or conjugate diameter of outlet ~11 cm
fetal head turns 90° during delivery. Face to side as i passes through the inlet and faces posteriorly through the outlet
Neutral position of the pelvis
anterior superior iliac spines and upper end of the symphysis pubis are in the same vertical plane
What does pelvic floor consist of
- 1. (upper/deepest) Pelvic diaphragm.
- 2. (middle) urogenital diaphragm - muscles of the deep perineal space
- 3. (lower) muscles of the superficial perineal space.
What muscles are in the pelvic diaphragm
levator ani, coccygeus
what is in the deep perineal space
- deep transverse perinei mm,
- sphnicter urethra mm,
- bulbourethral glands (male
- VAN's organs
what is in the superficial perineal space?
- superficial transverse perinei mm
- bulbospongiousus mm
- ischiocavernosus mm
- greater vestibular glands (female)
- erectile tissue, VAN's, organs
Functions of the pelvic floor
- 1. support the pelvic organs and contents
- 2. Withstand any increases in pressure in the abdominopelvic cavity
- 3. provide sphincter control of the perineal openings (urethra, vagina, and anus)
- diamond shaped area between the thighs.
- contrains the external genitalia and anal region.
- Separated from the pelvic cavity by the pelvic diaphram.
- = urogenital trianlge + anal triangle
anterior to the ischial tuberosities, contains the external urogenital organs
Posterior to ischial tuberosities, contains the end of the anal canal and anus
What innervates the anal triangle
anus and external anal sphincter both by the inferior rectal branch of pudendal nerve (S2-4)
- large wednged shaped space on each side of the ans filled with fat.
- pudendal nerve, artery, and vein are found here
External genitalia of the female
Mons pubis, labia majora, labia minora, vesitbule, bulbs of vestibule, clitoris, greater vestibular glands
What does labia minora form
the prepuce and frenulum of the clitoris
contains opening of the urethra and vagina
What are the bulbs of the vestibule
erectile tissue lying on each side of the vaginal opening
erectile tissue consisting of two crura and a body ending in the glans
greater vestibular (bartholin's) glands
secrete mucus for vaginal lubrication
External genitalia of the male
Penis erectile tissue
- paired dorsal corpora cavernosa
- unpaired venral corpus spongiosum
dorsal coporora cavernosa attachments
attaches along the ischiopubic ramus by its crus
ventral corpus spongiosum contains
- the urethra and ending in the enlarged glas
- bulb is attaches to the perineal membrane
fibromuscular sac of skin containing the testes and lower parts of the spermatic cords
layer of smooth muscles that wrinkle the skin of the scrotum
Muscles of the superficial perineal space
- lie between Colle's fascia (membranous layer of the superficial fascia) and the inferior fascia of the urogenital diaphragm (perineal membrane)
- - Bulbospongiosus (bulbocavernosus) muscles
- - ischiocavernosus muscles
covering the corpus spongiosum in the male and bulbs in the vestibule in the female
cover the crura of hte penis and clitoris
Action of the bulbospongiosus and ischiocavernosus
- Both - maintain erection by compressing veins
- Male - bulbospongiousus helps empty the urethra after bladder has emptied
- Female - sphincter of the vaginal opening
innervation of muscles of the superficial perineal space
pedendal nerve (S2-4) perineal branch
Muscles of the deep perineal space
- lie between the superior and inferior fascias of the urogential diaphragm. Muscles + their fascia = urogenital diaphragm.
- sphrincter urethrae
surrounds the membranous urethra and must be voluntarily relaxed during urination
Sphrincter urethrae / muscles of the deep perineal space innervation
pudendal nerve (S2-4) perineal branch
funnel-shaped musculofibrous sheet that closes off the pelvic outlet and forms the floor of the pelvic cavity
retroperitoneal with the exception of the uterus. Pass through the pelvic floor and are anchored to it.
Positions of organs in pelvic viscera
- rectum lies POST and passes through the anal region
- Urinary system lies anteriorly,
- Genital system takes an intermediate position
- both urinary and genital pass throught he urogenital region.
Location of kidneys
- lie of the POST abdominal wall embedded in perirenal fat.
- Right kidney lies slightly lower than the left
Urine flow sequence
renal pyramids -> minor calyces -> majora calyces -> renal pelvis -> ureters -> bladder.
smooth muscle sac lying behind the symphysis pubis and pubic bones
what anchors the bladder
nevck of bladder is anchored to the pubic bone by the pubovesical (female) and puboprostatic (male) ligaments
an equilateral triangle on the interior of the posterior wall. Angles are formed y the ureteric orifices above and the interal urethral orifice below
What makes up the walls of the bladder
Innervation of the bladder
- sympathetic fibers from lower thoracis and upper lumbar segments.
- Parasympathetic fibers - conveyed by pelvic splanchnic nerves from S2-4
Sympathetic innervation to bladder
maintain tonus of the bladder neck
parasympathetic innervation of the bladder
inhibits the bladder neck musculature and stimulate increased tonus of the detressor muscle of the bladder walls for urination
- female - 3-4 cm long. Pierces the ANT part of the urogenital diaphragm and opens in the vestibule.
- male - 18-20 cm long. Passes through the prostate (prostatic part), urogenital diaphragm (membranous part) and penis (spongy part)
Internal urethral sphincter
In neck of bladder. Made of smooth muscle innervated by excitatory sympathetic and inhibitory parasympathetic nerves
External Urethral Sphincter
Surrounds the membranous urethra and consists of skeletal muscle innervated by the pudendal nerve
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