The Perineum Flashcards
What is the perineum, and where is it located?
The perineum is a small space below the pelvic floor located between the upper parts of the thighs.
What is the shape of the perineum, and how is it divided?
The perineum is diamond-shaped and can be divided into two parts by an imaginary line between the ischial tuberosities:
Urogenital triangle
Anal triangle
What passes through the urogenital triangle?
The urethra (and vagina in females) passes through the urogenital triangle.
What fills in the urogenital triangle?
It is filled by sheets of fascia and muscle, forming the urogenital diaphragm.
What passes through the anal triangle?
The anal canal passes through the anal triangle.
How does the plane of the anal triangle differ from that of the urogenital triangle?
Due to the anterior tilt of the pelvis, the anal triangle is not in the same plane as the urogenital triangle.
What are the three layers of the urogenital diaphragm?
Superior fascia of the urogenital diaphragm
Deep perineal pouch
Perineal membrane (inferior fascia of the urogenital diaphragm)
What are the contents of the deep perineal pouch in males?
- Membranous urethra
- Bulbourethral glands
- Dorsal neurovasculature of the penis
- Deep transverse perineal muscle
- External urethral sphincter
What additional structures are in the deep perineal pouch in females?
Answer:
- Vagina
Compressor urethrae
- Urethrovaginal sphincter
- Dorsal neurovasculature of the clitoris
Name the muscles found in the deep perineal pouch.
- Deep transverse perineal muscle
- External urethral sphincter
- Compressor urethrae (females only)
- Urethrovaginal sphincter (females only)
What is unique about the external urethral sphincter in males?
The lower part forms a true sphincter around the urethra in males.
Where is the superficial perineal pouch located?
It is located inferior to the perineal membrane and superior to fascia and skin.
What structures are contained in the superficial perineal pouch?
- External genitalia
- Erectile tissue (penis in males, clitoris in females)
- Neurovasculature
Muscles:
- Ischiocavernosus
- Bulbospongiosus
- Superficial transverse perineal muscle
What are the main layers of the urogenital triangle from deep to superficial?
- Pelvic floor
- Urogenital diaphragm
- Deep perineal pouch
- Perineal membrane
- Superficial perineal pouch
- Skin and fascia
What is the perineal body, and where is it located?
The perineal body is the central point of the perineum, a collagenous and elastic mass where muscles of the perineum fuse and attach.
What are the functions of the perineal body?
Supports pelvic viscera
Serves as an attachment point for perineal muscles
Why is the perineal body important in childbirth?
It supports the pelvic floor, but can be damaged during childbirth due to stretching or tearing.
What is an episiotomy, and why is it performed?
An episiotomy is an incision made to enlarge the vaginal opening during childbirth, allowing the fetal head to pass more easily and facilitating better healing than a natural tear.
What are the two types of episiotomies, and how do they differ?
- Median episiotomy: Incision through the perineal body.
- Posterolateral episiotomy: Incision that avoids the perineal body.
What is the main structure that passes through the anal triangle?
Answer: The anal canal.
How is the anal triangle positioned relative to the urogenital triangle?
The anal triangle is not in the same plane as the urogenital triangle due to the anterior tilt of the pelvis
What is the ischioanal fossa, and where is it located?
The ischioanal fossa is a wedge-shaped space lateral to the anal canal and inferior to the pelvic floor, filled with fat and loose connective tissue.
Why is the ischioanal fossa clinically significant?
Infection in the ischioanal fossa can lead to abscesses or fistulas connecting to the anal canal.
What forms the medial boundary of the ischioanal fossa?
The external anal sphincter.
What forms the lateral boundary of the ischioanal fossa?
The obturator internus muscle
What forms the superior boundary of the ischioanal fossa?
The levator ani muscle.
What forms the inferior boundary of the ischioanal fossa?
Skin and fascia.
What is the pudendal (Alcock) canal, and what does it contain?
The pudendal (Alcock) canal is a passageway within the ischioanal fossa, containing:
- Internal pudendal vessels and branches
- Pudendal nerve and its branches
- Nerve to obturator internus
