rectum and anal canal Flashcards
what forms the pelvic bone?
two hip bone
what is posterior to the pelvic bone?
sacrum
Separates the 2 hip bones posteriorly
what is anterior the pelvic bone?
symphysis pubis
what are joints that form the pelvic bone ?
Sacroiliac joint
Symphysis pubis
what type of joint is sacroiliac joint ?
synovial plane joint
transmit weight from the spine to lower limbs
what type of joint is symphysis pubis ?
secondary cartilaginous joint
Provide slight movement and shock absorption during activities like walking and childbirth
what is false pelvis?
part of the abdominal cavity
located above the pelvic inlet
includes structures as ILIAC FOSSA , ILIAC CREST —> parts of abdominal cavity
CECUM and SIGMOID COLON are present here
what is true pelvis?
below the pelvic inlet
Obstetric term —-> crucial for childbirth
when the something passes the the arcuate line it is considered in the true pelvic
what marks engagement in devliery?
baby head pass below the ARCUATE LINE
what is pelvic inlet?
boundary that separates the false pelvis ( Above ) and true pelvis ( BELOW )
what is the extension of pelvic inlet?
extend from the sacrum at the back
to
outer edge of pubic symphysis at the front
what is a key land mark of pelvic inlet?
arcuate line
what is the pelvic cavity?
continuous with the abdominal cavity
theres no physical object separating them like the diaphragm separating the thoracoabdominal cavities
what is the other name of pelvic inlet?
pelvic brim
what is the other name of false pelvis?
greater pelvis
part of the abdominal cavity
what is the other name of true pelvis ?
lesser pelvis
what does the true/lesser pelvis has?
inlet —> it is at the brim/ pelvic inlet
outlet
False only has outlet which is the pelvic inlet
what is located at the true/lesser pelvis outlet?
it is closed by PELVIC DIAPHRAGM
what is pelvic diaphragm?
muscular floor of the pelvis ( True pelvis )
Group of muscles that form muscular floor closing off the true pelvis from below
what does the pelvic diaphragm separate?
Pelvis ( true/lesser )
from
Perineum
what is the function of pelvic diaphragm?
Support pelvic organs and maintain pressure regulation withing abdomen
Contract —> increase intra-abdominal pressure which assists in actions like childbirth, defecation and urination
describe the pelvic inlet?
line passing from :
Upper border of symphysis pubic
to
Sacral promontory
describe pelvic outlet?
line passing from the :
Lower border of symphysis pubis
to
Tip of coccyx
what lines the bony pelvis laterally , posteriorly and inferiorly ?
Muscles and fascia
what is the inferior muscle?
pelvic diaphragm
separates the content of pelvis from perineum
what muscles form the pelvic diaphragm ?
Levator ani
coccygeus muscles
Superior and inferior fascia
what are other muscles found in the pelvic inlet?
These muscles form the lateral wall
OBTURATOR internus : inner surface of the obutrator membrane and obturator foraman
Lateral rotators of the thigh
Piriformis : Small lateral rotators of the thigh , important for gluteal region because it serves as landmark + sciatic nerve and other neurovascular structures pass above or below it
what could happen if levator ani is damaged?
fecal incontinence and urine
what is origin of coccygeus ?
tip of ischial spine
what is the insertion of coccygeus?
Side of last piece of sacrum
First piece of coccyx
What is the nerve supply of coccygeus ?
Lower sacral nerve
what is the action of coccygeus ?
no action in man
in animals = moves the tail
what is the origin of levator ani muscle ?
1- Posterior surface of the body of the pubis
2- white line, which is the upper thickened part of obturator fascia ( arcus tendineus )
3- Ischial spine
what is the insertion of levator ani muscle?
Perineal body —> anterior one ( anterior to anal canal )
Side wall of anal canal
Anococcygeal body—> ( posterior to anal canal )
Tip of coccyx
these structures are from anterior to posterior
what is puborectalis ?
U shaped sling
what is the extension of puborectalis ?
bodies of pubic bone
urogenital hiatus
around anal canal ( around the rectum )
what is urogenital hiatus ?
opening in the pelvic diaphragm through which urethra and vagina pass
what is the function of puborectalis?
maintain fecal continence during defecation
during defecation this muscle relax
what is pubococcygeus?
fibers of levator ani divide and loop around the:
prostate in males —> levator prostate
vagina in females —–> pubovaginalis
attach to perineal body
originate from posterior surface of pubic body
Insertion is in perineal body, anococcygeal body , coccyx
what is the function of pubococcygeus ?
Support pelvic organs
Aid continence
stabilizes prostate / vagina by wrapping around them
help urine continuation by supporting prostate and vagina
when does iliococcygeus start and end ?
start at :
anteriorly at ischial spines
posterior aspects of the tendinous arch
Attach at :
posteriorly to the coccyx
anococcygeal ligament
what is the function of iliococcygeus ?
elevates pelvic floor
maintains continence
supports pelvic organs
what is the nerve supply of levator ani?
Pelvic surface : lower sacral and coccygeal nerves (S3 + S4 )
Perineal surface : Inferior rectal nerve, branch of pudendal nerve
which nerve allow for involuntary contraction ?
Pelvic surface innervation ( coccygeal nerve S3-S4)
cuz it is anatomic reflex control
Cough, sneezing , defecations
which nerve allow for voluntary contraction?
Perineal surface ( Inferior rectal nerve from pudendal nerve ) )
Conscious contraction and relaxations for defecations and urination
what is the action of levator ani?
Raising the intra abdominal pressure in forced expiration and expulsive acts like, defecation, cough , vomiting
Anterior fibers ( levator prostate , pubovaginalis or sphincter vagina ) —–> sling around prostate/vagina —> act as sphincter for vagina
Puborectalis : closes the rectal anal junction and reinforces the external anal sphincter
Assists childbirth –> guide the babys head through birth canal and support perineum during labor
what are the pelvic organs?
most anteriorly : symphysis pubic
urinary bladder + urethra
Uterus / vagina in females
Rectum + anal canal
most posteriorly : sacrum
what are the male pelvic organs ?
Urinary bladder
Rectum
Prostate
Urethra
describe the peritoneum in pelvic ?
Greater sac of peritoneum will line the anterior wall of the abdomen
Reflects to cover the superior surface of the urinary bladder
behind the bladder it will form a pouch called rectovesical pouch ( it will be in front of the rectum )
Passes over anterior surface of the rectum
what is rectovesical pouch?
Lowest part of peritoneal cavity in males pelvis
fluid can collect in certain pathological conditions
describe the peritoneum and urinary bladder?
the bladder is covered by peritoneum on the superior and upper posterior surfaces
describe the rectum and peritoneum ?
Upper 1/3 of rectum is covered on the frontal and lateral surfaces
Middle 1/3 covered only on the anterior surface
Lower 1/3 is not covered by peritoneum
which organs are not covered by peritoneum ?
Prostate —> it is surrounded by fascia
Urethra : passes through pelvic and perineal regions so it is not covered by peritoneum
describe the peritoneum in female pelvic organs?
peritoneum cover the anterior abdominal wall
describe the urinary bladder and peritoneum in females?
peritoneum covers the superior surface of urinary bladder
EXCEPT THE SMALL POSTERIOR AREA
what is uterovesical pouch ?
pouch formed by peritoneum
anterior to the uterus and above the bladder
describe the uterus and peritoneum ?
the peritoneum will cover :
Anterior body of uterus
Posterior body of uterus
Fundus of uterus
POSTERIOR SUPRAVAGINAL PORTION of the cervix
describe the vagina and peritoneum ?
the peritoneum covers :
POSTERIOR Upper part of vagina ONLY ( others are not )
describe the peritoneum and rectum in females?
similar to males
Upper 1/3 is covered frontal and lateral surface
middle 1/3 is covered anteriorly
Lower 1/3 is not covered
what is rectovaginal pouch ?
a pouch behind the uterus and in front of the rectum
formed by peritoneum
describe the peritoneum coverage of fallopian tube and ovaries?
they are covered by peritoneum but SMALL PARTS ARE NOT
where does the rectum begin?
3rd sacral piece S3
continuation of pelvic ( sigmoid colon )
what happens to sigmoid canal when it becomes rectum?
loses mesentery
become fixed in position
Retroperitoneal
where does the rectum end ?
1 inch in front and below the tip of COCCYX
become continuous with anal canal
what is sacral curvature ?
it is a curved following the concavity of sacrum and coccyx
what are lateral curvatures?
upper part of the rectum forms three lateral flexures
what are the 3 lateral flexures?
Upper flexure —> concave left
Middle flexure —–> concave right
Lower flexure ——> concave left
2 left and 1 right ( middle )
what is the function of the three lateral flexures?
storage of feces
help in defecation control
describe the lower part of the rectum?
Dilated to form rectal ampulla
what is rectal ampulla ?
dilation of the lower part of rectum
Temporarily stores feces before they are eliminated through anal canal
what is perineal curvature ?
at the junction of rectum and anal canal
the rectum is directed forward toward the perineum to accommodate the passage of stool
what is the importance of perineal curvature ?
fecal continence
maintain closure of anal canal until defecation is initiated
what are some features absent in rectum and present in other parts of large intestine ?
appendices epiploicae
tenia coli
sacculations
what is the relation between peritoneal and rectum?
Upper 1/3 of rectum is covered by peritoneum from the front and sides
Middle 1/3 : covered front only
Lower 1/3 no peritoneal covering
what are the anterior relations of rectum in female ?
Above : Rectouterine pouch
Below : posterior wall of vagina
what are the anterior relations of the rectum in MALES?
Above : Rectovesical pouch
Below :
base of the bladder
seminal vesicles
ampulla of vas
Terminal parts of ureter and prostate
what are the posterior relations of rectum?
Sacrum and coccyx
Piriformis and coccygeus and levator ani muscles
median sacral vessels
branches of superior rectal vessels
sympathetic trunk , lower sacral and coccgeal nerves
ganglion impare
what are the side relations of the rectum?
Pararectal fossa
what are the arteries supplying the rectum?
Superior rectal artery —> Supply upper part
Middle rectal artery —> supply middle part
inferior rectal artery—> Supply lower part
what is the origin of superior rectal artery?
Inferior mesenteric artery comes from abdominal aorta at L3
descend and gives raise to :
Left colic artery
sigmoid artery
then continue as SUPERIOR RECTAL ARTERY
when does the inferior mesenteric artery becomes superior rectal artery?
as it crosses the LEFT COMMON ILIAC ARTERY
what is the origin of middle rectal artery?
branch of anterior division of internal iliac artery
what is the origin of inferior rectal artery?
branch of internal pudendal artery
what is the veins drainage of rectum ?
corresponds to the arteries ( superior rectal vein, inferior rectal vein, middle rectal vein )
begin from the RECTAL VENOUX PLEXUS—> drain into inferior vena cava and portal circulation
what is the lymphatic drainage of the rectum?
Pararectal lymph nodes
Inferior mesenteric nodes
Internal iliac lymph nodes
where does pararectal lymph nodes get lymph from?
Superior rectal vessels ( Artery and vein )
where does inferior mesenteric nodes get lymph from ?
sigmoid colon ( hindgut )
sigmoid is derivate of hindgut so it drains into inferior mesenteric nodes
where does internal iliac lymph nodes get lymph from?
middle rectal vessels
where does anal canal begin at ?
1 inch below and in front of the tip of coccyx
continuation of the rectum
passes downward and backwards for 1.5 inches
where does the anal canal end ?
anal orifice
what is the anterior relation of anal canal?
Perineal body
what does the perineal body do?
separate the anal canal from the :
membranous urethra and bulb of the penis in males ( bulb is not soo much affected )
lower end of vagina
what is the posterior relation of anal canal?
Anococcygeal body
what does the anococcygeal do?
separate the anal canal from the tip of coccyx
what is the lateral relation of anal canal?
Upper part : Levator ani
Lower part : Ischiorectal fossa
describe the external anal sphincter?
voluntary striated muscle fibers
what does the external anal sphincter surround ?
Lower 2/3 of the canal
overlap the internal sphincter in the middle third of the canal
what does the external anal sphincter consist of ?
Subcutaneous : no bony attachment
Superficial : between perineal and anoccocygeal body and tip of coccyx
Deep part : around the middle 1/3 of anal canal
what is the nerve supply of external anal sphincter ?
inferior rectal nerve
perineal branch of 4th sacral nerve
what is the main action of external anal sphincter?
continence - voluntary close of anal canal
describe internal anal sphincter?
smooth muscle fibers
acting involuntary
Thickening of smooth circular muscle layer of the gut
surrounds upper 2/3 of the canal ( lower 2/3 was external and they overlap at middle 1/3)
what is the nerve supply of internal anal sphincter?
sympathetic fibers via :
superior hypogastric plexus
Inferior hypogastric plexus
what is anal column ?
longitudinal folds
in the mucosa of anal canal
what is anal valves?
semilunar valves connecting the lower end of the anal columns together
what is white line of hilton ?
line along the anal valves
represent the junction between the upper ectodermal parts and lower ectodermal parts
what dos the white line of hilton do?
during fetal life the line gives attachment to anal membrane
Separate the upper endodermal part from lower ectodermal part
describe the upper part above the line of hilton?
sympathetic innervation ( remember internal sphincter )
no pain
Columnar epithelium
describe the lower part below line of hilton ?
Somatic innervation ( remember external sphincter )
pain sensitive
stratified squamous
describe internal hemorrhoids ?
prolapse of rectal cushions —> Rectal mucosa containing the internal rectal venous plexus
Result from breakdown of muscularis mucosa
occur in the upper part of the anal canal ( above line )
Bleeding from hemorrhoids characteristically bright red cuz of the abundance of arteriovenous anastomosis
Receive visceral sensation and ARE NOT PAINFUL
PAINLESS AND RED ABOVE THE LINE
Describe external hemorrhoids ?
thrombosis in the veins of external rectal venous plexus
Covered by skin and receives somatic sensation and are PAINFUL
PAIN DUE TO SOMATIC INNERVATION ( BELOW THE LINE )
HARD BLUISH SWELLING
Describe anal fissure ?
Painful tear in the epithelial lining of anal canal
due to poor blood supply it the healing delayed and devlope into fissure
Usually located in the posterior midline inferior to pectinate line
Painful because the region is supplied by sensory somatic fibers ( BELOW THE LINE)
Accompanied by SPASM of EXTERNAL ANAL SPHINCTER :
because inferior rectal nerve supplies both the lining of the anal canal below the pectinate line and the muscles
what happens to the internal anal sphincter in cases of fissures?
the internal anal sphincter is the main one involved in anal fissures
It is supplied by involuntary autonomic fibers
When fissure happens and pain is there
the internal anal sphincter goes to spasm to try and protect BUT IT WORSENS THE PROBLEM AND CAUSE MORE PAIN
After this the external anal sphincter goes to spasm
Inferior rectal nerve —> supplies somatic nerves innervations to anal canal and external anal sphincter
fissure occur —> pain —> internal sphincter spams —> more pain —> external anal sphincter also goes to spams- —> pain
what are the boundaries of pelvic inlet?
Anteriorly —-> pubic symphysis
posteriorly —> sacral promontory and ala of sacrum
Laterally —> arcuate line of the ilium and pectineal line
what are the boundaries of pelvic outlet?
Anteriorly —> inferior margin of pubic symphysis
posteriorly —> tip of coccyx
lateral —–> ischial tuberosities
anterolaterally —> ischiopubic rami
Posterolaterally —-> Sacrotuberous ligaments
