Pelvis & perineum WB4 Flashcards
What bony landmarks create boundaries of the perineum
Name the orange and green triangle & name the bony porminance that separates each triangle
Orange= urogenital
Green = anal
Ischial tuberosities seperate each triangle
A thin sheet of deep fascia stretches between right and left sides of the pubic arch, below the pubic symphysis.
What is the name given to this fascia?
Perineal fascia
Function of the external anal sphincter & its innervation
Voluntary control of defacation: innervated by branches of the pudendal nerve
Function of the superficial transverse perineal muscle & its innervation
Flexes and stabiles perineal body; innervated by branches of the pudendal nerve (S2-S4)
Function of the deep transverse peirneal muscle & its innervation
Forms the urogenital diaphragm and anchors the perineal body, thus supporting the pelvic vescera
innervated by branches to the peuodendal nerve (S2-S4)
Function of the external urethral sphincter & its innervation
Compress the urethra to maintain urinary continence
Innervated by branches of the pudendal nerve (S2-S4)
Function of the bulbospongiosus muscle (male)
The muscle is relaxed during micturition but when contracted will stop the flow of urine.
- It aids in fully emptying the urethra after urination.
- It contracts rhythmically during ejaculation to create a series of wave-like contractions within the corpus spongiosum; this facilitates movement of ejaculate through the urethra.
- branches of pudendal nerve (S2-S4)
Function & innervation of the bulbospongiosus muscle in females
Compresses the vestibular bulb and expresses the secretions of the greater vestibular glands. Constricts the vaginal orifice and anterior fibers compress the deep dorsal vein of the clitoris, restricting venous return and allowing clitoral erection.
Branches of the pudendal nerve (S2-S4)
Function of the Ischiocavernosus (Male) and its innervation
Steady contraction of the muscle may help in impeding venous return from the corpora cavernosa of the penis, aiding in maintenance of erection.
- The muscle also undergoes rhythmic contraction in conjunction with bulbospongiosus during ejaculation.
- The contractions serve to help maintain the erection and possibly to aid in moving the ejaculate through the urethra.
innervated by branches of the pudendal nerve (S2-S4)
Function & innervation of the Ischiocavernosus (Female)
Compresses the corpus cavernosum, restricting venous return and allowing clitoral erection in the female.
Innervated by branches of the pudendal nerve (S2-S4)
What is the perineal body & name the muscles that converge at it
Perineal body= central point of perineum, site of convergence of bulbospongiosus, external anal sphincter, superficial & deep transverse perineal muscles and ischiocavenosus.
- Levator ani (part of the pelvic floor).
- Bulbospongiosus muscle.
- Superficial and deep transverse perineal muscles.
- External anal sphincter muscle.
- External urethral sphincter muscle fibres.
Label these mucles/structures
What is the urogenital triangle?
The urogenital triangle is the anterior half of the perineum. It is bounded by the pubic symphysis, ischiopubic rami, and a theorectical line between the two ischial tuberosities. The triangle is associated with the structures of the urogenital system – the external genitalia and urethra.
Structurally, the urogenital triangle is complex, with a number of fascial layers and pouches. Unlike the anal triangle, the urogenital triangle has an additional layer of strong deep fascia; the perineal membrane. This membrane has pouches on its superior and inferior surfaces.
Complete the diagram
What are the 3 parts of the make urethra
What is the narrowest and widest part of the male uerthra?
Which are the widest and narrowest parts of the male urethra and why?
Widest part: prostatic part; most dilatable
Narrowest part: membranous part; the least dilatable
What can put the male urethra at risk of becoming narrowed?
Enlargment of the prostate
Label
Name the two layers of fascia which make up the pelvic diaphragm and their function
Superficial and inferior fascia, make up the pelvic diaphram. These provide additional support for the pelvic organs within the perineum.
Where do the ducts of the bulbo-urethral glands open into?
The proximal part of the spongy urethra
The penis is made of three cylindrical cavernous bodies of erectile tissue, name these
2X corpus cavnosa
1X corpus spongiosum
Label
Where do we find the majority of erectile tissue in the penis
In the corpus cavernosum
Describe the sensory innervation of the penis
Through the dorsal nerve of the penis, a branch of the pudendal nerve
In females, where does the urethra open
The urethra is shorter in females, opening into the anterior aspect of the urogenital triangle, directly in front of the vagina
Where is the internal/vesical urethral sphincter located?
is it voluntary or involuntary?
What is its innervation?
Around the proximal end of the urethra, at the neck of the bladder
Involuntary
Sympathetic T11 - L2
Parasympathetic S2-S4
Where is the external urethral sphincter found in females?
Distally and inferior to the bladder neck, anterior to the vagina.
WHere is the external urethral sphincter found in males
is it voluntary or involuntary and what is its innervation
Just inferior to the prostate: at risk of compression due to prostatic enlargment
voluntary
innervated by perineal branches of the pudendal nerve S2-S4
What puts males and females at risk of incontinence
In males any form of prostatic surgery to overcome urinary retention can make urinary incontinence more likely
In the female childbirth can weaken the ligaments supporting the pelvic floor, and can increase the risk of incontinence.
What are the contents of the vulva and what is its collective nerve and arterial supply?
Mons pubis
labia majora
labia minora
vestibule
bartholins glands
clitoris
Collectivly supplied by the pudendal nerve and the internal pudendal artery
What is the vestibule?
The vestibule is the area enclosed by the labia minora. It contains the terminal aspects of the urethra and the vagina
What is the vulva
a collective term for several anatomical structures:
- Mons pubis – a subcutaneous fat pad located anterior to the pubic symphysis. It formed by the fusion of the labia majora.
-
Labia majora – two hair-bearing external skin folds.
- They extend from the mons pubis posteriorly to the posterior commissure (a depression overlying the perineal body).
- Embryologically derived from labioscrotal swellings
-
Labia minora – two hairless folds of skin, which lie within the labia majora.
- They fuse anteriorly to form the hood of the clitoris and extend posteriorly either side of the vaginal opening.
- They merge posteriorly, creating a fold of skin known as the fourchette.
- Embryologically derived from urethral folds
- Vestibule – the area enclosed by the labia minora. It contains the openings of the vagina (external vaginal orifice, vaginal introitus) and urethra.
- Bartholin’s glands – secrete lubricating mucus from small ducts during sexual arousal. They are located either side of the vaginal orifice.
-
Clitoris – located under the clitoral hood. It is formed of erectile corpora cavernosa tissue, which becomes engorged with blood during sexual stimulation.
- Embryologically derived from the genital tubercle
Name the two sphincters controling defaecation and their part to play (voluntary or involuntary)
Internal and external anal sphincter
internal = involuntary control
external = voluntary control
What is the ischio-anal (ischio-rectal) fossa?
Situated lateral to the anal canal and inferior to the pelvic floor- 2 fat containing fossa, called the ischio-anal (ischio-rectal) fossa
These allow the anal canal to expand during defaecation
Complete this diagram
Complete this diagram
What foramena does the neurovascular bundle enter the ischio-anal (rectal) fossae
Through the lesser sciatic foramena
Function of the superficial transverse perineal muscle
Action: fixes and stabilises perineal body
- innervation: branches of pudendal nerve (S2-S4)
- blood supply: perineal artery
- attachments: ischial tuberosity and perineal body
Function of the bulbospongiosus muscle in males
relaxed during micturition but when contracted will stop the flow of urine.
- It aids in fully emptying the urethra after urination.
- It contracts rhythmically during ejaculation to create a series of wave-like contractions within the corpus spongiosum; this facilitates movement of ejaculate through the urethra.
Function of bulbospongiosus muscle in females
Compresses the vestibular bulb and expresses the secretions of the greater vestibular glands. Constricts the vaginal orifice and anterior fibres compress the deep dorsal vein of the clitoris, restricting venous return and allowing clitoral erection.
Function of ischiocavernosus muscle in males
Maintenance of erection.
- The muscle also undergoes rhythmic contraction in conjunction with bulbospongiosus during ejaculation.
- The contractions serve to help maintain the erection and possibly to aid in moving the ejaculate through the urethra.
Function of ischiocavernosus muscle in females
Compresses the corpus cavernosum, restricting venous return and allowing clitoral erection in the female.
Function of the anococcygeal body
Contributes to maintaining the anatomical position of the anorectum in relation to the coccyx and the integrity of the pelvic floor muscles.
→ facilitating deification & maintaining continence and sexual function
Name 3 structures piercing through the pelvic diaphragm
Urethra, vagina & anus
What 2 fascias make up the pelvic diaphragm?
Superior and inferior pelvic fascia
Significance of the superior pelvic fascia
- covers the superior surface of the structures that make up the pelvic diaphragm (in both males and females)
- continuation of the transversalis fascia lining the abdominal wall; and helps separate the abdominal cavity from the perineum
- attached to the body of the pubis, then merges with obturator fascia and then attaches to spine of ischium
- makes up the tendinous arch of the pelvic ligament
- attachment point for the lateral ligament of the urinary bladder
Significance of the inferior pelvic fascia
- in both males and females
- covers the inferior surface of the structures that make up the pelvic diaphragm
- laterally continuous with the obturator fascia
- forms the superior boundary of the ischiorectal fossa
- also blends with the fascia of the external anal and urethral sphincter muscles
What fascia is corpus cavernous covered by?
→ tunica albuginea (vs. corpus spongiosum, which is not covered by this layer of fascia, only by Buck’s Fascia)
- contains the majority of the erectile tissue
Which part of the penis does the urethra run through?
Corpus spongiosum
Where is the bulb of the penis?
The expanded end of the corpus spongiosum, closest to the body
Erection is maintained by increasing the pressure in the bulb of the penis
What is bucks fascia
A layer of deep fascia covering the three erectile bodies of the penis
Note that corpus spongiosus is not covered by tunica albuginea, only by bucks fascia!
What tissue in males, does the erectile tissue in femnales correlate to
Corpus cavernous → clitoral erraction tissue
