ANATOMY OF PERINEUM Flashcards
In general, what does the urogenital triangle and anal triangle contain?
Urogenital: male and female external genitalia
Anal: anal canal and anus and ischioanal fossa
What separates the 2 triangles?
A line connecting the ischial tuberosities
Perineal membrane:
- Stretches between?
- Extends anteriorly and posteriorly to?
- Separates the urogenital triangle into what 2 compartments?
- Stretches between the ischiopubic rami
- Extends anteriorly almost to pubic symphysis
- Extends posteriorly to ischial tuberosities
- Deep and superficial perineal spaces
Where do the cavernous bodies of the external genitalia attach?
Deep perineal membrane
What is the superficial perineal space/what are its boundaries?
Potential space bounded above by perineal membrane and below by the superficial perineal fascia
What does the superficial perineal space contain in females?
What does it contain in males?
Clitoris, vestibular bulb, greater vestibular glands
- In males: root of the penis and proximal portion of spongy urethra
What is the perineal body and it is formed by what muscles?
Irregular subcutaneous mass of fibromuscular tissue formed by converging fibers of the levator ani, deep transverse perineal and bulbospongiosus muscles and external anal sphincter
Where does the perineal body lie in females and males?
Females: between the rectum and vagina
Males: between the rectum and bulb of penis ;) mmmm <3
Function of the perineal body
Supports the pelvic diaphragm and pelvic viscera
Innervation of perineum muscles
Pudendal nerve (S2 – S4)
Blood supply to perineum
Perineal branches of the internal pudendal artery
Venous drainage of the perineum
Drains to internal pudendal vein and internal iliac vein
MALE UROGENITAL TRIANGLE: SCROTUM
What is it?
Extension of the anterior abdominal wall that encloses the testes and spermatic cord
MALE UROGENITAL TRIANGLE: PENIS
What are the 3 parts of the penis? (just names)
Root, body, glans penis (aka glans)
MALE UROGENITAL TRIANGLE: PENIS
Root: what is it attached to? Covered by? Composed of what 2 things?
Attached to perineal membrane, covered by muscles
Composed of:
1. Paired crura: attached to the ischiopubic rami and covered by the ischiocavernosus muscles
2. Bulb of penis: attached to the perineal membrane and covered by the bulbospongiosus muscles
MALE UROGENITAL TRIANGLE: PENIS
What do the unattached parts of the paired crura of the penis continue as?
Corpora cavernosa
MALE UROGENITAL TRIANGLE: PENIS
What does the unattached part of the bulb of penis continue as?
Corpus spongiosum
MALE UROGENITAL TRIANGLE: PENIS
What is the body made up of? Is it covered by muscle?
Not covered by muscle
Made up of 3 cylindrical bodies of erectile tissue
MALE UROGENITAL TRIANGLE: PENIS
What binds the 3 bodies together?
Deep penile fascia (Buck’s fascia)
MALE UROGENITAL TRIANGLE: PENIS
What are the 3 erectile bodies?
2 corpora cavernosa (continuations of the crura); lie side by side on the dorsum of the penis
1 corpus spongiosum (continuation of the bulb of the penis); lies ventral to the 2 corpora cavernosa and is transversed by the penile urethra
MALE UROGENITAL TRIANGLE: PENIS
Glans penis: what is it an extension of? Characterized by what 2 things?
Extension of the distal end of the corpus spongiosum
Characterized by:
Corona and external urethral orifice
MALE UROGENITAL TRIANGLE: PENIS
Skin and subcutaneous tissue of the penis:
Blood supply and venous drainage
Blood supply: external pudendal artery
Venous drainage: superficial dorsal veins → external pudendal veins
MALE UROGENITAL TRIANGLE: BULBOURETHRAL GLANDS
When are they active?
During sexual arousal
MALE UROGENITAL TRIANGLE: BULBOURETHRAL GLANDS
What do they secrete and where do their ducts open?
Secrete mucus; ducts open into the proximal part of the spongy urethra
MALE UROGENITAL TRIANGLE: BULBOURETHRAL GLANDS
Where are they located?
On either side of the urethra below the prostate surrounded by the urethral sphincter
ERECTION
Describe the changes seen in the arteries and muscles during erections?
- Normally constricted helicine arteries relax under parasympathetic innervation → cavernous spaces dilate and become engorged
- Pudendal nerve innervates contractions of the bulbocavernosus and ischiocavernosus muscles to impede venous outflow and maintain the erection
ERECTION
Describe the path of the urethra starting from the prostate
Traverses the prostate (prostatic urethra) and urogenital diaphragm (membranous urethra), pierces the dorsal surface (top) of the bulb of penis and courses within the corpus spongiosum (spongy urethra)
FEMALE UROGENITAL TRIANGLE
What is the mons pubis?
Fatty tissue that’s continuous with the superficial fatty layer of the abdominal wall; lies anterior to the pubic symphysis and is continuous with the labia majora
FEMALE UROGENITAL TRIANGLE
What is the labia majora?
Bilateral folds of fatty tissue; dark skin covered with hair; the inner surface is smooth and hairless
FEMALE UROGENITAL TRIANGLE
What is the labia minora?
Bilateral folds of hairless skin; flank the vestibule of the vagina → merge towards the anterior end of the clitoris
FEMALE UROGENITAL TRIANGLE
What is the vestibule of the vagina? What does it contain?
Space surrounded by 2 labia minora
Contains urethral and vaginal orifices and the openings of the ducts of the greater and lesser vestibular glands
FEMALE UROGENITAL TRIANGLE
What are vestibular bulbs?
Paired masses of erectile tissue that lie deep to the labia minora and are covered by the bulbospongiosus muscles
- Homologous to the bulb of the penis
- DO NOT form part of the clitoris
FEMALE UROGENITAL TRIANGLE
Function of the greater vestibular glands
Lubricate the vestibule during sexual arousal
FEMALE UROGENITAL TRIANGLE
What does it mean by cavernous tissue?
Highly vascularized; gets engorged during arousal
FEMALE UROGENITAL TRIANGLE
What 2 muscles cover erectile tissue?
Ischiocavernosus and bulbospongiosus
FEMALE UROGENITAL TRIANGLE
Where is the clitoris located?
Made up of how many erectile bodies?
At the anterior junction of the labia minora
2
FEMALE UROGENITAL TRIANGLE
What make up the erectile bodies?
Paired corpora cavernosa that make up the crura → join to form the body of the clitoris
ANAL TRIANGLE
What is the ischioanal fossa?
What are its superior and inferior boundaries?
Lateral and medial boundaries?
Fat-filled space that surrounds the anal canal
- Superior: pelvic diaphragm
- Inferior: anal region
- Lateral: obturator internus
- Medial: pelvic diaphragm and external anal sphincter
ANAL TRIANGLE
Where does it extend anteriorly?
Anteriorly into the urogenital triangle superior to the perineal membrane
ANAL TRIANGLE
How is the pudendal canal formed?
Splitting of the fascia of the obturator internus on the lateral wall of the ischioanal fossa
ANAL TRIANGLE
Pudendal bundle exits what foramen before entering the pudendal canal?
Lesser sciatic foramen
ANAL TRIANGLE
What bundle traverses the fossa?
Inferior rectal
ANAL TRIANGLE
Purpose/function of this fossa
Support the anal canal while also allowing it to enlarge during defecation
ANAL TRIANGLE
The inner surface of the anal canal is characterized by what 3 things?
Anal columns, anal valves, anal sinuses
ANAL TRIANGLE
How is the perineal flexure created? What is its function?
Puborectalis (part of levator ani) forms a sling around the anorectal junction, pulling it anteriorly and creating the flexure
- When the muscle relaxes = defecation
- Helps to maintain continence
ANAL TRIANGLE
What do the muscle fibers of the external anal sphincter merge with: anteriorly, superiorly, posteriorly?
Anteriorly: bulbospongiosus and perineal body
Posteriorly: anococcygeal ligament
Superiorly: levator ani
