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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
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Bony pelvis formed by
- formed by 2 hip bones anteriorly and laterally
- sacrum and coccyx posteriorly
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Parts of hip bone
ilium, ischium and pubis
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3 parts of hip bones fuse where?
at the acetabulum at about 16 years to form a single bone at about 16 years
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Sacrum
- Formed by fusion of 5 sacral vertebral segments
- consists of base, apex, pelvic, dorsal, and lateral surfaces and a sacral canal
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Base of sacrum
- upper surface of first sacral vertebra
- articulates with 5th lumbar vertebral body at lumbosacral joint
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sacral promontory
anterior projecting edge of the body
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lateral mass or ala
wide upper part on each side of sacral promontory
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Pelvic surface
four pairs of pelvic sacral foramina that transmit the ventral rami of S1-4
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Dorsal surface of sacrum
- convex
- contains: median sacral crest, medial sacral crest, four pairs of dorsal sacral foramina, lateral sacral crest
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median sacral crest
3 or 4 spinous tubercles. in the middle of the sacrum
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Medial sacral crest
four small articular tubercles lateal to median sacral crest.
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Sacral hiatus
below the last median sacral spinous tubercles. bounded by the sacral cornua from the medial sacral crests on each side.
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dorsal sacral foramina
transmit the dorsal rami of S1-4
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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
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Apex of sacrum
narrow, articulates with the base of the coccyx at the sacrococcygeal joint
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Sacral canal
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.
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Where does the subarachnoid space end
level of the second sacral vertebra
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What does that sacral canal contain?
Contains cauda equina, filum terminale and meninges
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What passes through the sacral hiatus
filum terminale and S5 nerves
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Coccyx
small triangular bone consisting of 4 fused vertebral segments. 2nds to 4th coccygeal vertebrae decrease in size and are fused bodies
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Base of coccyx
upper surface of the 1st coccygeal vertebral body. Articulates with the apex of the sacrum.
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Coccygeal cornua
project dorsolaterally from coccyx
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Transverse processes
project superolaterally from coccyx
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Pelvic inlet
plane bounded by the pelvic brim. Divided into the greater pelvis and the lesser pelvis
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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
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greater pelvis
located above the pelvic inlet between the iliac bones and is part of the abdominal cavity
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lesser pelvis
sitated below the pelvic inlet and forms the pelvic cavity or simply the pelvis
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Pelvic outlet
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
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Maximum diameter of inlet in female
transverse diameter is 13.5 cm
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maximum diameter of outlet in female
anteroposterior or conjugate diameter of outlet ~11 cm
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Baby delivery
fetal head turns 90° during delivery. Face to side as i passes through the inlet and faces posteriorly through the outlet
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Neutral position of the pelvis
anterior superior iliac spines and upper end of the symphysis pubis are in the same vertical plane
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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.
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What muscles are in the pelvic diaphragm
levator ani, coccygeus
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what is in the deep perineal space
- deep transverse perinei mm,
- sphnicter urethra mm,
- bulbourethral glands (male
- VAN's organs
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what is in the superficial perineal space?
- superficial transverse perinei mm
- bulbospongiousus mm
- ischiocavernosus mm
- greater vestibular glands (female)
- erectile tissue, VAN's, organs
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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)
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Perineum
- 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
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Urogenital triangle
anterior to the ischial tuberosities, contains the external urogenital organs
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Anal triangle
Posterior to ischial tuberosities, contains the end of the anal canal and anus
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What innervates the anal triangle
anus and external anal sphincter both by the inferior rectal branch of pudendal nerve (S2-4)
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Ischioanal fossa
- large wednged shaped space on each side of the ans filled with fat.
- pudendal nerve, artery, and vein are found here
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External genitalia of the female
Mons pubis, labia majora, labia minora, vesitbule, bulbs of vestibule, clitoris, greater vestibular glands
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What does labia minora form
the prepuce and frenulum of the clitoris
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Vestibule has?
contains opening of the urethra and vagina
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What are the bulbs of the vestibule
erectile tissue lying on each side of the vaginal opening
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clitoris
erectile tissue consisting of two crura and a body ending in the glans
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greater vestibular (bartholin's) glands
secrete mucus for vaginal lubrication
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External genitalia of the male
penis, scrotume
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Penis erectile tissue
- paired dorsal corpora cavernosa
- unpaired venral corpus spongiosum
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dorsal coporora cavernosa attachments
attaches along the ischiopubic ramus by its crus
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ventral corpus spongiosum contains
- the urethra and ending in the enlarged glas
- bulb is attaches to the perineal membrane
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Scrotum
fibromuscular sac of skin containing the testes and lower parts of the spermatic cords
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Dartos muscle
layer of smooth muscles that wrinkle the skin of the scrotum
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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
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Bulbospongiosus muscles
covering the corpus spongiosum in the male and bulbs in the vestibule in the female
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ischocavernosus muscles
cover the crura of hte penis and clitoris
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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
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innervation of muscles of the superficial perineal space
pedendal nerve (S2-4) perineal branch
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Muscles of the deep perineal space
- lie between the superior and inferior fascias of the urogential diaphragm. Muscles + their fascia = urogenital diaphragm.
- sphrincter urethrae
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sphincter urethrae
surrounds the membranous urethra and must be voluntarily relaxed during urination
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Sphrincter urethrae / muscles of the deep perineal space innervation
pudendal nerve (S2-4) perineal branch
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Pelvic diaphragm
funnel-shaped musculofibrous sheet that closes off the pelvic outlet and forms the floor of the pelvic cavity
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pelvic viscera
retroperitoneal with the exception of the uterus. Pass through the pelvic floor and are anchored to it.
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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.
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Location of kidneys
- lie of the POST abdominal wall embedded in perirenal fat.
- Right kidney lies slightly lower than the left
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Urine flow sequence
renal pyramids -> minor calyces -> majora calyces -> renal pelvis -> ureters -> bladder.
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urinary bladder
smooth muscle sac lying behind the symphysis pubis and pubic bones
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what anchors the bladder
nevck of bladder is anchored to the pubic bone by the pubovesical (female) and puboprostatic (male) ligaments
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Trigone
an equilateral triangle on the interior of the posterior wall. Angles are formed y the ureteric orifices above and the interal urethral orifice below
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What makes up the walls of the bladder
detrussor muscle
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Innervation of the bladder
- sympathetic fibers from lower thoracis and upper lumbar segments.
- Parasympathetic fibers - conveyed by pelvic splanchnic nerves from S2-4
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Sympathetic innervation to bladder
maintain tonus of the bladder neck
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parasympathetic innervation of the bladder
inhibits the bladder neck musculature and stimulate increased tonus of the detressor muscle of the bladder walls for urination
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Urethra
- 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)
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Internal urethral sphincter
In neck of bladder. Made of smooth muscle innervated by excitatory sympathetic and inhibitory parasympathetic nerves
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External Urethral Sphincter
Surrounds the membranous urethra and consists of skeletal muscle innervated by the pudendal nerve
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