Abdomen, Pelvis and Perineum 4 Flashcards
What is the perineum?
the anatomical region which is located inferior to the main pelvic cavity
What separates the perineum from the main pelvic cavity?
The pelvic diaphragm (levator anii and coccygeus)
Which processes does the perineum play a part in?
- defacation
- micturition
- intercourse
- partuition
How is the perineum best viewed and what is its shape from this angle?
Inferiorly with the thighs abducted
Diamond shaped
What two triangles can the perineum be divided into?
- anterior urogenital triangle
- posterior anal triangle
What structre lies in the centre of the perineum, between the urogenital and anal triangles?
The perineal body
Where is the perineal body located in men vs women?
- men = between the bulb of the penis and the anus
- women = between the vagina and anus
What is the perineal body?
- small fibromuscular structure
- site of attachment for the muscles and fascia of the perineum
- provides support and function
What does the urethra pass through in the perineum in women?
Deep perineal pouch > perineal membrane > superficial perineal pouch > vestibule in front of vagina
What does the urethra pass through in the perineum in men?
Deep perineal pouch > perineal membrane > superficial perineal pouch > penis > external urethral orifice in the glans
What do the ejaculatory ducts do?
drains sperm cells and ejaculatory fluid from the ductus deferens and seminal vesicles into the prostatic part of the urethra
What happens to the internal urethral sphincter during ejaculation?
Closes to prevent sperm moving into the bladder
What does the urogenital triangle contain?
The urethra and external genitalia
What are the boundaries of the urogenital triangle?
- pubic symphysis anteriorly
- ischiopubic rami laterally
- (imaginary) line between the ischial tuberosities posteriorly
What are the layers of the urogential triangle from deep to superficial?
- Pelvic diaphragm muscles (not in perineum)
- Deep perineal pouch
- Perineal membrane
- Superficial perineal pouch
- Perineal fascia (deep and superficial)
- Skin
What does the deep perineal pouch contain?
- deep transverse perineal muscles
- external urethral sphincter
- urethra
- vagina or bulbourethral glands
What is the function of the perineal membrane?
provides attachment sites for the roots of the external genitalia
What does the superficial perineal pouch contain?
- ischiocavernosus muscle
- bulbospongiosus muscle
- superficial transverse perineal muscle
- erectile tissue for penis or clitoris
- greater vestibular glands (women)
What are the urethral sphincter muscles in the deep perineal pouch?
- female = external urethral sphincter, sphincter urethrovaginalis, compressor urethrae
- male = external urethral sphincter
What are the muscles in the deep perineal pouch innervated by?
Pudendal nerve (S2-S4)
What are the bulbourethral glands?
Pea-sized glands that sit one either side of the urethra and secrete a mucous like substance to lubricate the urethra (male only)
What is the perineal membrane?
- a thickened fascia which separates the deep and superficial perineal pouches
What is the function of the perineal membrane?
- attachment point for the roots of the external genitalia and superficial perineal pouch muscles
- transmits urethra and vagina ro the superficial perineal pouch
- supports the pelvic floor muscles
What is the structure of the erectile tissues (penis and clitoris)?
Core of expandable tissue surrounded by a connective tissue capsule
What is the structure of the clitoris?
- two corpora cavernosa converge near the pubic symphysis to form the body of the clitoris
- two vestibular bulbs in the superficial perineal pouch converge to form the glans of the clitoris
How can the clitoris be observed?
- glans is the only visible part
- body can be palpated under the skin
What are the greater vestibular glands and where are they located?
- secrete mucous into the vestibule of the vulva and around the opening of the vagina
- located in the superficial perineal pouch
What is the structure of the penis?
- two corpora cavernosa forming the dorsal side
- corpus sponginosum which forms the ventral side and contains the penile urethra
- the CS also expands distally to form the glans of the penis
What are the two regions of the penis?
The root and the body
What does the root of the penis consist of?
The fixed ends of the copora cavernosa and the corpus sponginosum
What does the body of the penis consist of?
The free parts of the corpora cavernosa and corpus sponginosum covered by skin
What is the innervation of the erection of the clitoris and penis?
Parasympathetic fibres of the pelvic splanchnic nerve
Where does blood flow for erections arise from?
Internal pudendal artery
What is the action of the ischiocavernosus muscle?
Moves blood from the corpora cavernosa of the clitoris/penis into the body during erection
What is the action of the bulbosponginosus muscle?
- moves blood from the glans of the clitoris/penis
- assists with movement of residual urine or semen from the penile urethra
What is the action of the superficial transverse perineal muscle?
Stabilising the perineal body