Sem 2 RA week 1 Flashcards
pouches in females?
formed by?
what else is formed?
Vesicouterine pouch - between uterus + bladder
rectouterine pouch “pouch of Douglas” - between uterus and rectum
pouches formed by parietal peritoneum as it covers pelvic organs
Peritoneum forms broad ligament as it passes over the uterus
pouches in males?
rectum + bladder = vesicorectal pouch
What covers bladder?
Internal surface of bladder?
Parietal peritoneum covers superior surface of bladder + hold sit against public bones (can make difficult to identify during dissection)
Internal surface = transitional epithelium + rugae
As bladder fills?
Where is apex found?
Help in place by?
What is this?
As bladder fills it rises into suprapubic region (i.e. above pubic bones)
Apex of bladder found posterior to pubic symphysis - it is held by a small piece of connective tissue called the urachus
Urachus = embryological remnant of structure that drained foetal bladder + joined umbilical cord
What is found at base of bladder?
What happens here?
Muscular wall of bladder?
Base of bladder is triangular - small smooth area of mucous membrane called the the trigone
urethra exits + ureters enter at the trigone
Muscular coat of smooth muscle called detrusor muscle
Detrusor muscle of bladder forms?
Control?
How are we able to control when we urinate?
Detrusor muscle forms incomplete sphincter at neck of bladder - sphincter vesicae
controlled by ANS - not voluntary
There is an external voluntary sphincter of micturition in urogenital diaphragm
Neck of bladder held in place by?
Males = puboprostatic ligament
Females = pubovesical ligaments
(pass from pubic bones)
Urethra pathway?
pelvic diaphragm?
urethra leaves bladder and passes through urogenital diaphragm in both sexes
pelvic diaphragm = levator ani muscles etc
blood supply bladder?
Superior vesical arteries
- from umbilical branch of anterior division of internal iliac artery
Inferior vesicle arteries
- from anterior division of internal iliac artery
- females = vaginal artery (also branch of ant. division)
Venous drainage bladder?
Nerve supply?
Venous drainage = vesical plexus → internal iliac veins
Nerve supply = ANS inferior hypogastric plexus
lymph drainage bladder?
most = internal iliac nodes clustered around internal iliac arteries
some drainage can pass to other nodes e.g. sacral nodes
Pelvic organ other than bladder which is common to both males and females?
Peritoneum?
where does it extend to?
Rectum
Upper ⅓ covered by visceral peritoneum
Middle ⅓ peritoneum covers anterior surface
Lower ⅓ = infraperitoneal
Extends from 3rd sacral verterba (previously sigmoid colon) to tip of coccyx where it pierces pelvis floor as the anal canal
Internal surface of rectum divided into?
Between these?
Why?
Supported by?
Function?
Internal surface of rectum is thrown into 3 transverse folds
between folds = rectal ampulla
shape helps storage of faeces
rectum supported by levator ani muscles - specifically puborectalis which passes around rectum and contracts to bend wall of rectum
maintains continence
Rectum blood supply?
Superior rectal artery (inf. mesenteric)
Middle rectal artery (internal iliac)
Inferior rectal (internal pudendal)
There is only 1 superior rectal artery
middle + inferior are bilateral
venous drainage rectum?
site of portal systemic anastamosis
Superior rectal vein (inf. mesenteric - portal)
middle rectal vein (int. iliac - systemic)
Inferior (int. pudendal - systemic)
Lymph drainage rectum?
Nerve supply?
split drainage
superior rectum = pre-aortic nodes at L3 (inf. mesenteric)
inferior rectum = pararectal nodes → internal iliac nodes (around int. iliac arteries)
Nerve supply = inferior hypogastric plexus
…
Uterus?
Hollow, muscular organ that sits in middle of pelvic cavity - covered by broad ligament
Broad ligament?
Function?
Divisions?
Fold of peritoneum that overlies the uterus and uterine tubes
Provides small amount of support to uterus (main support is from ligaments at cervix) + carries neurovascular structures of the uterus
Broad ligament dividd into 3 areas
- Mesovarium - holds ovaries to posterior surface of broad ligament
- Mesosalpinx - supports uterine tubes
- Mesometrium - main part of broad ligament associated with body of uterus
Most superior part of uterus?
Main part?
Lining of uterus?
Most superior part = fundus, rises above entrance of uterine tubes
main part = body which narrows to form cervix inferiorly
cervix opens into muscular tube called vagina
Walls of the uterus are muscular (myometrium) but lined by endometrium which is shed during each menstrual cycle
Fornices?
Os?
Internal wall sof uterus form small narrowed area superior to cervix = internal os
At the cervix = external os
as cervix bulges into vagina there are small spaces each size of the cervix = lateral fornices
blood supply uterus?
anastamose?
Relationship?
Uterine arteries = from anterior division of int. iliac artery
uterien artery anastamoses with ovarian artery which supplies ovaries, fundus of uterus + uterine tubes
Relationship between ureters and uterine arteries is important during hysterectomy procedures
Uterine arteries must be tied but close relationship between uterine artery ureter (‘bridge over water’) means that ureter can be accidentally tied at the same time – causing pain and renal complications
Uterine tube areas?
Possible comp?
Istmus = narrowed section as they pierce wall of uterus
Ampulla = expanded area where fertilisation occurs
Infindibulum = finger-like fimbrae which gather ovum released by ovary and direct it into uterine tube
fertilised ovum may implant into wall of uterine tube - ectopic pregnancy (can rupture uterine tube)
main support to uterus?
allows?
ligaments associated with cervix?
main support = ligaments attached to cervix
allows uterus to expand and rise into abdomen during pregnancy but still maintain its relationship with vagina and pelvic floor
ligaments = tranverse cervical (cardinal) ligaments, pubocervical, uterosacral
normal position of uterus?
allows?
Anteverted + anteflexed
Anteverted = long axis of uterus bend forward on long axis of vagina
Antflexed = long axis of uterus bent forward at internal os with long axis of vagina
allows uterus to flop forwards over empty bladder for support
Pelvic floor muscles uterus?
Specifically?
Pelvic floor muscles support uterus to prevent prolapse through pelvic floor
Pubococcygeus - forms sling around vagina (called pubovaginalis)
Puboprostaticus in males
ovary attachments?
Function?
Arterial supply?
Ovaries = attached to posterior surface of broad ligament by mesovarium
Function = ova and hormone production
arterial supply = ovarian artery (direct branch from abdominal aorta @L2)
Venous drainage ovaries?
Nerve supply?
Right - ovarian vein drains to IVC
Left - ovarian vein drains to left renal vein
Nerve supply = aortic plexus
Ligaments supporting ovaries?
function?
ligament of ovary passes between uterus + ovary
carries ovarian artery + vein
vaginal artery supplies?
Branch?
Internal pudendal artery?
Vaginal artery = supplies distal uterus and vagina
Branch of either uterine artery OR direct branch of anterior division of int. iliac artery (equivalent to inferior vesical artery in male)
internal pudendal artery = supplies distal vagina and perineum
Lymphatic drainage ovaries, uterine tubes, uterus + vagina?
Notice how broad + round ligaments act as conduits to carry lymph away from uterus
Although there is also the more standard “lymph following arterial supply” pattern seen in other areas
Vas deferens?
spermatic cord found?
pathway?
vas deferens joins?
also receives secretions from?
vas deferens = smooth muscle tube that transports sperm from testis to ejaculatory duct and then into urethra
Spermatic cord found in inguinal canal
passes in spermatic cord through superficial inguinal ring, along the inguinal canal and through deep inguinal ring into pelvis, crosses lateral wall of pelvis to descend towards seminal vesicles at posterior surface of bladder
joins with duct of seminal vesicles and receives fluid from ejaculatory duct within the prostate gland
will also receive secretions from bulbourethral glands in deep perineal pouch
2 smooth muscle tubes that pass towards bladder in male?
How to distinguish?
ureter + vas deferens
They are similar in size and can be mistaken for each other
Ureter passes into pelvis from abdomen and corsses bifurcation of common iliac vessels before descending towards base of the bladder
vas deferens crosses the lateral wall of pelvis over external iliac vessels to descend towards seminal vesicles
Seminal vesicles?
Function?
Highly coiled tubes that lie posterior to the bladder in males
They appear to be small, lumpy structures from an but are actually a small bundle of a long tube similar to vas deferens but coiled around itself and wrapped in connective tissue.
Function = secrete fluid to increase the liquid component of semen and also support the sperm – release fructose which acts as a source of energy for the sperm
Vas deferens blood supply?
What do these also supply?
Distal end of vas deferens + seminal vesicles = supplies by branches of anterior division of int. iliac artery i.e. inferior vesical + prostatic arteries
(prostatic artery is branch of the inferior vesical artery)
Inf. vesical arteries also supply bladder + distal part of ureters in a male
The vas deferens (and arterial supply) can be seen passing towards the seminal vesicle. The pale pink structure anterior to the seminal vesicle is the prostate gland.
Prostate gland found?
Function?
What passes through?
Formed from?
Inferior to bladder
Function = secretes proteolytic enzymes + acid phosphatase which supports sperm (fluid is alkaline which helps neutralise acidic environment of vagina)
Recieves ejaculatory ducts + has urethra passing through it
usually described as being formed from 5 incompletely divided lobes
Arterial supply prostate?
Venous drainage?
implication?
Arterial supply = internal pudendal, middle rectal + inferior vesical arteries
prostatic venous plexus = receives blood from deep dorsal vein of penis → then drains into internal iliac
prostatic venous plexus has many communications with the vertebral veins - permitting metastasis of prostatic carcinoma to the lower vertebral column
prostate gland supported by?
Supported by puboprostatic ligament + muscles of pelvic floor
Pubococcygeus (part of levator ani) forms muscular support for prostate gland called puboprostaticus or levatore prostatae
Prostatic enlargement?
Affects?
Ax?
Consequence
Benign enlargement of the prostate land is common in males >50
May affect all or part of prostatic lobes
May be benign or malignant Ax
Any enlargement of the prostate may affect the urethra and passage of urine from the bladder
Pic shows enlargement of the median lobe of the prostate gland that has disrupted the smooth muscle sphincter at the base of the bladder -causes leakage of urine and desire to urinate
If lobes increase in size urethra may be compressed causing difficulty releasing urine
This can form small pouches in the bladder, in which urine sits – increasing the chances of urinary infections
Lymph drainage male pelvic organs?
lower parts of the bladder, seminal vesicles, prostate gland and erectile tissues of the penis = internal iliac nodes
More distal parts of the penis = deep inguinal nodes
It is important to remember that lymph from the testis follows its arterial supply back to aortic nodes clustered around the root of the testicular artery (L2)
Anal triangle?
Significance?
Spaces either side of rectum?
Imaginary line between:
ischial tuberosities (base)
and coccyx (apex)
Rectum becomes anal canal as it pierces pelvic floor in anal triangle
Spaces either side of rectum called ischiorectal (ishioanal) fossae
Ischioanal fossa boundaries?
Contents?
Walls = ischial tuberosity, rectum/anal canal
Roof = levator ani (pelvic diaphragm)
Floor = skin
Contents = branches of pudendal nerve, artery, vein + adipose tissue
Anal canal surrounded by?
Supplied by?
Walls of rectum and anal canal supplied by?
Main component of ischioanal space?
Anal canal surrounded by external anal sphincter
Supplied by branch of pudendal nerve - the inferior rectal nerve
walls of rectum + anal canal also supplied by inferior rectal artery (branch of int. pudendal)
Main component of space is fat - supports neurovascular structures and allows anal canal to expand during defecation
This slide shows the perineal nerve (branch of the pudendal nerve) passing close to ischial tuberosity accompanied by internal pudendal artery.
The inferior rectal vessels and nerves cross the ischioanal fossa towards the external anal sphincter
This slide shows the ischioanal fossa in a formalin embalmed cadaver.
The fat has been removed to reveal the muscular pelvic diaphragm (levator ani, and more posterior coccygeus) and the internal pudendal vessels and pudendal nerve
Anal canal?
Feature?
What do walls form?
Voluntary control?
Anal canal = final part of digestive tract
Has small internal folds called anal columns that contain tiny branches of superior rectal vessles
Wall of the canal forms involuntary internal anal sphincter
Voluntary control of defaecation from skeletal muscle that surrounds opening of anal canal - the external anal sphincter
External anal sphincter made from?
Attachments?
What is this?
Function?
Aided by?
Nerve supply?
Skeletal muscle
attachments = from perineal body to anococcygeal ligament
perineal body = small, dense structure composed of connective tissue that lies at the edge of the urogenital diaphragm
Function of EAS = closes anus (voluntary)
Aided by puborectalis (part of pelvic floor muscles)
EAS innervation = pudendal nerve (S2, S3, S4) inferior rectal branch
Lines anal canal?
What are these?
Pectinate + white lines
Pectinate line - important landmark for end of visceral (internal) part of digestive tract and start of parietal (body wall) structures
White (anocutaneous) line = transition to true skin
(Levator ani on this slide represents puborectalis as it blends with the wall of the rectum to help control continence)
Arterial supply anal canal?
Superior rectal artery (from inf. mesenteric)
Middle rectal (from int. iliac)
Inferior rectal (from int. pudendal)
NB: ends of superior rectal arteries lie within anal columns on the internal surface of the canal
…
Urogenital triangle found?
Boundaries?
What is found here? Passes through?
sits anterior to anal triangle
Base = imaginary line between ischial tuberosities
Apex = pubic symphysis
Urogenital diaphragm found in urogenital triangle + structures such as urethra must pass through this diaphragm in both sexes
Fascia of pelvis?
Types?
Attached to?
Fascia of abdominal wall continues into pelvis
Fatty (Camper’s) + membranous (Scarpa’s = Colles’)
Camper’s continuous with ischiorectal fossa + thigh
In males, Camper’s is replaced with dartos smooth muscle in the scrotum
Membranous = Scarpa’s fascia called Colles’ fascia as it passes into labia (females) or scrotum (males), attached to posterior border of urogenital diaphragm at perineal body
Urogenital diaphragm functions?
Layers?
2 functions:
- Closes off space between pubic bones - prevents structures prolapsing
- Provides area of attachment for structures of superficial perineal pouch
3 layers
- superior layer - fascia (deep, blends with perineal body and membrane)
- Middle layer - sphincter urethrae (voluntary) and deep transverse perineal muscles (this layer also described as having an anatomical space called the deep perineal pouch)
- inferior layer - fascia (superficial, the perineal membrane - structures that lie between this membrane + the skin are described as being in the superficial perineal pouch)
Fusion of urogenital diaphragm layers?
Space between layers of urogenital membrane?
Layers fuse anteriorly + posteriorly - anteriorly there is small gap left near pubic symphysis where vessels to clitoris + penis pass through
posteriorly the layers fuse with the perineal body - this helps to connect the fascia of the urogenital diaphragm to rest of fascia in pelvis - thought to be involved in transmission of stress across pelvic floor
“Space” between layers of urogenital membrane = deep perineal pouch
Deep perineal pouch found?
What is found in pouch in both sexes?
Males?
Females?
Between fascial layers of urogenital diaphragm
both sexes = urethra, sphincter urethrae, deep transverse perineal muscles, internal pudendal vessels + branches, pudendal (perineal) nerve
Males = membranous urethra, dorsal nerves of penis, bulbourethral glands, penile arteries
Females = vagina, dorsal nerves of clitoris
(small glands associated with vagina lie in superfical perineal pouch)
Superficial perineal pouch?
Contains?
Superficial perineal pouch lies between the perineal membrane and skin
Contains:
- Muscles = ischiocavernosus, bulbospongiosus, superficial ransverse perineal
- Urethra, vagina, clitoris, penis
- Erectile tissue = crura, bulb of vestibule (female), bulb of penis (male)
- Nerves and vessels
Important thing to remember muscles of superficial perineal pouch?
Nerve supply to muscles of superficial perineal pouch?
Function of muscles?
Don’t get names of muscles of superficial pouch confused with the names of the erectile tissues
supplied by perineal branch of the pudendal nerve
overlie erectile tissues of the perineum in both sexes - help maintain erection of the tissues by contracting to impede venous return → retains blood inside erectile tissue
Ischiocavernosus muscles found?
Bulbospongiosus?
Arrangement in sexes?
Superficial transverse perineal muscles function?
ischiocavernosus = overlie crura
bulbospongiosus = overlie bulb of penis in males + bulb of vestibule in females
In females, the bulb of the vestibule is in 2 parts (one on either side) so bulbospongiosus also on either side of vaginal opening
In males, bulbospongiosus muscles meet in the midline + surround the bulb of the penis
STP muscles shown by blue block arrows - support the edge of the urogenital diaphragm in both sexes (equivalent deep TP muscles in deep pouch)
Perineal body?
Where is it found?
What does it provide attachment for?
small fibrous structure
Found at posterior margin of urogenital diaphragm
Provides attachment for: external anal sphincter + muscles of superficial perineal pouch (bulbospongiosus, superficial TP muscles)
Erectile tissue males vs females?
What are they? Females vs males?
Much smaller in females
Crura (crus) = lie next to ischiopubic rami
- Females = form body of clitoris
- Males = continue into penis as corpus cavernosa
Bulb of the penis - continues as corpus spongiosum of the penis which will also form the glans penis
Bulb of the vestibule - surrounds the opening of the vagina and forms the glans of the clitoris
Erectile tissue penis?
Urethra?
Erectile tissue surrounded by?
3 blocks of erectile tissue:
2 x corpus cavernosum
1x corpus spongiosum
urethra lies within corpus spongiosum so is called spongy or penile urethra
rectile tissue surrounded by connective tissue that contains vessels and nerves that supply erectile tissue + skin
Blood supply penis?
Nerve supply?
Branches of internal pudendal artery
sensory branches of pudendal nerve
Depper arteries to penis?
Deeper arteries to bulb of penis and erectile tissues also branch from the internal pudendal artery
Male urethra?
4 distinct parts
- Pre-prostatic = between trigone + prostate gland
- Prostatic = passes through prostate and joined by ejaculatory ducts
- Membranous urethra = passes through urogenital diaphragm
- Penile/spongy = passes through corpus spongiosum to open at glans of penis
Slide shows the branches of the pudendal nerve that supply sensory innervation to the penis and scrotum.
Perineal branches of the pudendal nerve also contain motor fibres to the small muscles in the superficial perineal pouch
Note how pudendal nerve passes through greater sciatic notch, around the ischial spine and through the lesser sciatic notch to send branches to the structures of the anal and urogenital triangles
Equivalent structure to penis in females?
Therefore…
Clitoris
Erectile tissue of clitoris (like penis) is supplied by ANS and its blood supply is from branches of int. pudendal artery + sensory nerve supply from branches of pudendal nerve
Nerve supply to female perineum?
The peritoneum passes from the inner surface of the anterior abdominal wall and over the bladder. In a female it will then pass over both sides of the uterus and the over the anterior surface of the bladder to reach the posterior abdominal wall. This forms the vesico-uterine and rectouterine pouches (shown in photograph A). In a male, there is a vesico-rectal pouch between the bladder and the rectum.
The pelvis is a bowl shape so it is easier to see some structures of the lateral walls if the pelvis is hemisected. Some structures are in the midline or cross the midline, so they are easier to see if the pelvis is left intact. So that both views can be seen in the DR, all of the even numbered tables will leave the pelvis intact and all of the odd numbered tables will section the pelvis of their cadaver. Photograph B shows the midline cut – the soft tissues should be carefully sectioned first with a scalpel/scissors then the bone should be cut as close to the midline as possible.
The pelvis should be detached from the rest of the trunk on ALL tables to allow the pelvis and lower limb to be examined more easily.
The bladder lies immediately posterior to the pubic bone. It is a muscular bag that expands above the pubic bones as it fills with urine. Photograph A shows a hemisectionof a male pelvis with the bladder pulled away from the pubic bone. Photograph B shows the internal surface of the bladder – rugae are folds of the internal wall that become less pronounced as the bladder fills. Photograph C shows a bladder inside an intact pelvis. The wall of the bladder has been opened to show the trigone – the 2 ureters are highlighted by red plastic strips and the steel pointer shows the urethra.
The bladder is of a slightly different size and shape in different individuals. In some male cadavers the bladder wall may stretch due to issues with release of urine from the bladder caused by prostatic enlargement. Other pathological changes of the bladder wall may occur in both sexes.
The photograph shows the superior and inferior vesical arteries that supply the bladder. They are branches from the anterior division of the internal iliac artery and will be discussed further in a later presentation.
Photograph A shows the rectum as it descends towards the pelvic floor in a female pelvis. The transverse shelves formed by the internal rectal wall are not easy to identify in a Thielcadaver. However the change from the rectum to the anal canal can be observed as the rectum passes through the pelvic floor (photograph B) and the change to skin at the opening of the anal canal can also be seen (photograph C). You can observe these structures more easily in a hemisected pelvis (as shown in photographs B and C) but can observe the distal parts of the anal canal during dissection of the anal triangle in an intact pelvis.
The uterus lies between the bladder and the rectum in a female pelvic cavity. It sits enclosed within the two layers of the broad ligament. Photograph A shows the uterus and uterine tubes and the mesometriumthat forms the main part of the broad ligament. It also shows a fibroid on the fundus of the uterus – a small mass of tissue that is commonly seen in cadavers in the the DR. In photograph B the mesometriumhas been dissected to reveal the uterine artery as it crosses towards the uterus over the ureter – the ‘bridge over water’ relationship between the two structures.
Photograph A shows a uterine tube as it passes from the uterus towards the ovary. The piece of broad ligament associated with the uterine tube is called the mesosalpinx. The uterine tube does not directly attach to the ovary but instead forms fimbraethat sit close to the surface of the ovary. The round ligament of the uterus passes from the uterus near the entrance of the uterine tube, through the deep inguinal ring, along the inguinal canal to attach to the tissue of the labia majora. The round ligament can be seen in photographs A and B.
Photograph A shows the ovary and supporting piece of the broad ligament – the mesovarium. Photograph B shows the ovarian artery and vein that lie within the suspensory ligament of the ovary (the artery is the superior structure in the photograph). The ovarian artery is a direct branch of the abdominal aorta and the ovarian veins drain directly into the inferior vena cava on the right and into the renal vein on the left. Photograph C shows the ligament of the ovary that passes between the uterus and the ovary to provide support to the ovary.
The slide shows a hemisectionthrough a male pelvis. The bladder can been seen, reflected away from the pubic bone. The prostate gland lies immediately inferior to the bladder and the urethra exits the trigone area of the bladder and passes though the prostate gland. The urethra then passes through the urogenital diaphragm to exit the pelvis and enter the superficial perineal pouch. The prostate gland shown in the photograph appears of a normal, healthy size and shape but it is common to find pathological or benign changes in the prostate in the DR due to the age of the donors (50+ years).
Photograph A shows the bladder and prostate gland, the area surrounded by the white dotted line contains the seminal vesicle of that side of the body. The duct from the seminal vesicle is joined by the vas deferens to form the ejaculatory duct inside the prostate gland. The vas deferens carries sperm from the testis, through the inguinal canal and into the pelvic cavity. It can be observed in photograph B crossing the pubic ramus as it exits the deep inguinal ring and descends into the pelvis.
Photograph C shows the vas deferens (and accompanying artery) as it passes towards the seminal vesicle. The vas deferens carries sperm and the prostate gland and seminal vesicles contribute to the liquid component of semen. These elements mix together in the prostatic urethra – remember the urethra is part of the urinary and reproductive tracts in a male.
The male urethra passes from the prostate gland, through the deep perineal pouch (where it is called the membranous urethra) and into the penis. Photograph A shows the dorsal surface of the penis with the skin reflected to reveal the superficial sensory nerves lying in the superficial fascia of the penis. These nerves are dorsal branches of the pudendal nerve. Photograph B shows a deeper dissection that reveals the deep dorsal artery of the penis – a branch of the internal pudendal artery. The main components of the penis are blocks of erectile tissue called corpora (corpus is the singular form), this means body. Sitting superiorly are two corpus cavernosa (cavernosum is the singular form) and inferiorly is the corpus spongiosum. The corpora cavernosa are extensions from the crura and the corpus spongiosum is an extension of the bulb of the penis (shown in photograph C). The penile or spongy urethra runs through the corpus spongiosum, photograph D shows the urethra opened to reveal it is a smooth muscular tube that runs the length of the penis and exits at the glans.
Photograph A shows the gluteal region and posterior surface of the thigh in a hemisected pelvis. The area of the anal triangle is shown by the black dotted circle. The boundaries of the anal triangle are the ischial tuberosities, the coccyx and an imaginary line crossing through the centre of the perineum. Photograph B shows the same area with the skin dissected away to reveal the main content of the ischioanalfossa – fat and connective tissue. Photograph C shows the same area but with some of the fat removed to reveal the inferior rectal nerves and vessels and the external anal sphincter that surrounds the opening of the anal canal.
Further dissection of the ischioanalfossa (shown in photograph A) reveals the muscular roof of the fossa – levatorani muscle. This forms part of the pelvic diaphragm that prevents prolapse of the pelvic viscera through the pelvic floor. The puborectalis part of levatorani blends with part of the wall of the rectum to help maintain faecal continence. The main control of faecal continence is the external anal sphincter. The skeletal muscle fibres that form the sphincter are shown in photograph B. They are under voluntary control via inferior rectal branches of the pudendal nerve.
This photograph shows the inferior rectal nerve, it supplies the external anal sphincter and also levatorani. The inferior rectal artery is a branch of the internal pudendal artery.
Photograph A shows the perineal region of a female cadaver. The skin of the labia majora is still intact. More medial to the labia majora are the smaller labia minora that sit either side of the opening of the vagina. Photograph C shows the labia majora when the skin and connective tissue has been removed to reveal bulbospongiosus– one of the the small skeletal muscles present in the superficial perineal pouch of the urogenital triangle. The urogenital triangle is the area between the two pubic rami and it contains the urogenital diaphragm that protects the pelvic contents from prolapse and also creates two anatomical spaces called the deep and superficial perineal pouches. The deep pouch lies between the fascial layers of the diaphragm and is therefore more difficult to visualise; but the superficial perineal pouch lies between the inferior layer of fascia (the perineal membrane) and the skin so is easier to identify during dissection.
The superficial pouch contains erectile tissue, muscle, nerves and vessels. The bulbospongiosusmuscles covers the superior surface of the bulb of the vestibule erectile tissue blocks that sit either side of the opening of the vagina. They are innervated by perineal branches of the pudendal nerve.
The bulb of the penis is a single piece of erectile tissue that extends from the root of the penis to form corpus spongiosum of the penis (shown in photograph A). Bulbospongiosusmuscle covers the bulb of the penis (shown by the red plastic marker in photograph B). The bulbospongiosusmuscles act to compress the erectile tissue of the bulb of the vestibule and bulb of the penis to reduce venous return and therefore help to maintain erection.
The crura are also erectile tissue blocks present in both males and females. The crura extend to form the corpora cavernosa in males, in females they contribute to the formation of the clitoris. The crura lie against the inferior pubic rami and are covered by ischiocavernosus muscles. Photograph A shows ischiocavernosus in a female and photograph B shows ischiocavernosus muscle in a male.
The deep pouch is harder to visualise during dissection as it is an area inside the two fascial layers of the urogenital diaphragm filled with the deep transverse perineal and sphincter urethrae muscles. Structures such as the urethra and vagina also pass through the deep pouch. Photograph A shows the most inferior layer of fascia of the urogenital diaphragm called the perineal membrane. It has been partially reflected to reveal the muscle inside the deep perineal pouch.
Photograph B shows other structures found in the superficial perineal pouch – perineal branches of the pudendal nerve and branches of the internal pudendal vessels.
