6 - The pelvic viscera and perineum Flashcards
What is the perineum divided into?
Urogenital triangle
Anal triangle
Where is the perineum found?
Inferior to the pelvic floor
What are the borders of the urogenital triangle?
Anterior - pubic symphysis
Laterally - Inferior ramus of the pubis
Posterior - Line between the ischial tuberosities
What are the contents of the urogenital trangle?
Urethra Vagina Bulbourethral/Bartholin gland Superficial transverse perineal muscle Ischiocavernosus Bulbospongiosus Crus penis/clitoral crura Bulb of penis/vestibular bulb Urogenital diaphragm Muscular perineal body Deep and superficial pouches
What are the borders of the anal triangle?
vLine between ischial tuberosities anteriorly
Sacrotuberous ligament laterally
Coccyx posteriorly
What are the contents of the anal triangle?
Anal canal Ischioanal fossa Pudendal canal Sacrotuberous ligament Sacrospinous ligament Anococcygeal body Sphincter ani externus Gluteus maximus Obturator internus Levator ani Coccygeus
What is the blood supply to the perineum?
From the internal iliac artery-
Superior gluteal artery
Inferior gluteal artery
Internal pudendal artery
Exits through greater sciatic foramen, inferior to the piriformis muscle
Curves around the sacrospinous ligament
Enters perineum through lesser sciatic foramen
Travels through the pudendal canal with the internal pudendal veins and pudenal nerve
Branches to give inferior rectal, perineal, dorsal clitoris/penis arteries
What is the nerve supply to the perineum?
Pudendal nerve from S2,3,4
Leaves the pelvis through greater sciatic foramen
Enters perineum through lesser sciatic foramen
Branches to give the inferior rectal nerve, dorsal nerve of penis/clitoris and perineal nerve
What are the layers of the urogenital triangle?
Deep perineal pouch
Superficial perineal pouch
Separated by the perineal membrane
What is in the deep perineal pouch?
Between pelvic floor and perineal membrane
Contains external urinary sphincter and deep transverse perineal muscle
Bulbourethral gland found here in males but not in females
Membranous portion of urethra (males) and proximal urethra (females)
Vagina
What is in the superficial perineal pouch?
Space between perineal membrane and Colles’ fascia Contains the erectile tissue Crura of penis/clitoris Bulb of penis/vestibular bulbs Shape3 muscles Bulbosponiosus Ischiocavernosus Superficial transverse perineal Bartholin’s glands in females
What is the deep perineal fascia?
Fascia covering the superficial perineal muscles
Continuous with the fascia of the abdominal wall muscles
What are the two superficial perineal fascias?
Membranous layer (Colles’ fascia) – thin, strong layer that binds the muscles of the root of the penis Fatty layer (Camper’s fascia) – continuous with ischioanal fascia and the superficial fascia of the thigh
How many corpus cavernosas are there and where is it situated?
2
Dorsal
What is ventrally located in a cross section of the penis?
Corpus spongiosum
Contains spongey urethra
What innervates the penis?
Pudendal nerve
What is the bulb?
Attached at the urogenital diaphragm
Transversed by urethra
Continues forward – corpus spongiosum
What is the crura?
Attached to pubic arch
Lie at the dorsum of the penis – corpus cavernosum
What muscles are there around the penis and what do they do?
Ischiocavernosus – encloses the crura in the root and contract to force blood into the corpus cavernosa in order to maintain erection and ejaculation
Bulbospongiosus – encloses the bulb in the root and contracts to empty the urethra in urination and ejaculation
What happens during an erection?
Parasympathetic outflow to inferior hypogastric plexus
Non adrenergic or cholinergic
Nitric oxide release
Vasodilation and engorgement
Compressed veins against fascia
Pressure further accentuated by ischiocavernosus and bulbospongiosus
What happens during ejaculation?
Sexual excitement makes the external urethral orifice moist – by the bulbourethral (Cowper’s) glands
Sympathetic fibres to the smooth muscle of the epididymis, vas deferens, seminal vesicles and prostate
Rhythmic contractions of bulbospongiosus
Sphincter of bladder contracts involuntarily to prevent retrograde ejaculate flow
Secretion of fluid into ejaculatory ducts by seminal vesicles, prostate gland and bulbourethral glands
Explain the anatomy of the female external genitalia?
Glans of clitoris found within prepuce
External urethral orifice and vaginal orifice found within the vestibule of the vagina
Vestibule surrounded by labia minora
Labia majora around the outside
Opening of greater vestibular (Bartholin’s) glands either side of the vaginal orifice
What is the bulb of the vestibule?
Attached to urogenital diaphragm
Divided by the vagina
Homologous to the bulb of the penis
Superficially covered by bulbospongiosus
What is the crura of the clitoris?
Attached to pubic arch and connect to the rami of the pubis and ischium
Homologous to the crura of the penis
Superficially covered by ischiocavernosus
What is bartholin’s gland?
Found posterior to the vestibular bulbs
Secretes lubricating mucous at the vaginal orifice through small ducts that open out into the posterior vestibule
What is a bartholin’s cyst?
Infection or blockage of one of these ducts is not uncommon and produces an abscess at the side of the vestibule called a Bartholin’s cyst
What are the 3 muscles of female erectile tissue and where are they?
Bulbospongiosus – surrounds vaginal orifice (can reduce its size), covers vestibular bulbs and assists clitoral ejection
Ischiocavernosus – assists clitoral erection and tenses the vagina during orgasm
Superficial transverse perineal muscle
What is the perineal body?
Larger in females
Fibrous tissue where many of the perineal muscles insert
Levator ani
External anal sphincter
Bulbospongiosus
Superficial transverse perineal – fixes perineal body
Supports the vaginal wall