The Pelvic Floor

Question 1

What is the pelvic floor and the perineal body?

Answer 1

The pelvic floor is also known as the pelvic diaphragm. It is a muscular and fibrous tissue diaphragm that fills the lower part of the pelvic canal. It closes the abdominal cavity and defines the upper border of the perineum. The pelvic floor supports the pelvic organs and is pierced by the urethral and vagina termed the urogenital hiatus and rectum – the rectal hiatus. Between these two hiatuses lies a fibrous node known as the perineal body which joins the pelvic floor to the perineum.

Question 2

What are the boundaries of the pelvic cavity?

Answer 2

The pelvic cavity is limited inferiorly by the pelvic floor and the remainder of the walls are formed by
• Anteroinferior pelvic wall – Rami of the pubic bone and pubic symphysis
• Lateral pelvic walls – obturator internus muscle (and the obturator membrane)
• Posterior wall – Sacrum, coccyx (and associated ligament of sacroiliac joint, e.g. sacrococcygeal ligament), and the piriformis muscle

Question 3

How do structures layer over the obturator foramen to form the pelvic floor?

Answer 3

Structures layer over the obturator foramen on the medial side in a certain order: Obturator membrane, Obturator internus with a layer of fascia which is where the levator ani attaches to, Levator ani, Perineal body and perineal muscles. Overlying this are the organs - Rectum, uterus, bladder.

Question 4

What is the levator ani muscle?

Answer 4

The levator ani muscle forms a broad muscular sheath and forms the main part of the pelvic floor; it is formed by the puborectalis, pubococcygeus, and iliococcygeus muscle. It attaches to the pubic bone anteriorly, ischial spines, and the tendinous arch of levator ani laterally and the ischial spines posteriorly. It is innervated by the nerve roots S2, 3 and 4.

Question 5

Describe the 3 parts of the levator ani muscle?

Answer 5

• Puborectalis loops around the anal canal to provide for both faecal and urinary continence and must relax to allow for micturition or defecation.
• Pubococcygeus this is the main constituent of the levator ani and some of its fibres loops down around the prostate and vagina (levator prostate and pubovaginalis)
• Iliococcygeus thin muscle fibres comes from the ischial spine and attach posteriorly at the coccyx

Question 6

Describe the coccygeus muscle?

Answer 6

The coccygeus muscle arises from the ischial spine and runs to the inferior sacrum and coccyx; their fleshy fibres lie on and attach to the sacrospinous ligament.

Question 7

What are the main functions of the pelvic floor?

Answer 7

• Support the abdominopelvic viscera
• Resistance to increases in intra-pelvic/abdominal pressure
• Urinary and faecal continence.

Question 8

What affects does child birth have on the pelvic floor?

Answer 8

The levator ani are involved in supporting the foetal head during cervix dilation in childbirth.

1. Stretch of pudendal nerve – neuropraxia and muscle weakness
2. Stretch and damage of pelvic floor and perineal muscles – muscle weakness especially pubococcygeus and puborectalis
3. Stretch/rupture of ligaments supports of muscles – ineffective muscle action

Question 9

How can we protect again prolapse and incontinence in childbirth?

Answer 9

When the pelvic floor gets damaged you can end up with prolapse and Incontinence. Mediolateral Episiotomy protects the anal sphincter muscles from becoming teared.

Question 10

What factors increase the risk of prolapse?

Answer 10

• Age
• Multiples vaginal deliveries
• Menopause – Atrophy of tissues after oestrogen withdrawal as oestrogen maintains connective tissue
• Obesity
• Chronic cough
• Intrinsic connective tissue diseases
• Smoking

Question 11

What are the statistics regarding urinary incontinence in females over 40?

Answer 11

50% of women over 40 will have urinary incontinence problems
Surgery for prolapse is a common procedure in gynaecology
Recurrence of prolapse occurs in 10-15% of women

Question 12

How can we treat prolpase?

Answer 12

Pelvic floor muscle exercise – Easy, safe and effective – Cure of incontinence in 50-75% patients – Will prevent or delay worsening of prolapse
Surgery – Continence procedures – Prolapse procedures

Question 13

What procedures are there regarding prolapse and continence ?

Answer 13

Increase support to sphincter mechanism and prevent descent of bladder neck – Colposuspension – Tension-free vaginal tape
Effective – Cure rate 85%-90%

Remove prolapsed organs
Restore connective tissue supports

Question 14

What are the side effects of prolapse procedures?

Answer 14

Recurrence, new incontinence and dyspareunia. Side effect – Voiding difficulty/retention – Overactive bladder disease (obstruction)

Question 15

What are the anatomical borders of the perineum

Answer 15

• Anterior – Pubic symphysis
• Posterior– The tip of the coccyx
• Laterally – Inferior pubic rami and inferior ischial rami, and the sacrotuberous ligament
• Roof – The pelvic floor
• Base – Skin and fascia

Question 16

What are the surface borders of the perineum?

Answer 16

These boundaries are best shown when the lower limbs are abducted, and a diamond shape is depicted. The skin boundaries of the perineum are:
• Anteriorly: Mons pubis in females, base of the penis in males.
• Laterally: Medial surfaces of the thighs.
• Posteriorly: Superior end of the intergluteal cleft.

Question 17

What is the anal triangle?

Answer 17

The anal triangle is the posterior half of the perineum. It is bounded by the coccyx, sacrotuberous ligaments and an imaginary line between the ischial tuberosities.

Question 18

What are the components of the anal triangle what does the fossae contain and what is their role?

Answer 18

The components of the anal triangle are:
• Anal aperture – the opening of the anus.
• External anal sphincter muscle – voluntary muscle responsible for opening and closing the anus.
• Two ischioanal/ischiorectal fossae – these are spaces located laterally to the anus.

These fossae contain fat and connective tissue, which aid expansion of the anal canal during defecation.

Question 19

What is the urogenital triangle?

Answer 19

The urogenital triangle comprises of the anterior half of the perineum. It is bounded by the pubic symphysis, ischiopubic rami, and an imaginary line between the two ischial tuberosities. The triangle is associated with the structures of the urogenital system – the external genitalia and urethra.

Question 20

How is the structure of the urogenital triangle different to that of the anal triangle?

Answer 20

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, known as the perineal membrane. This membrane has pouches on its superior and inferior surfaces.

Question 21

Describe the 6 layers of the urogenital triangle?

Answer 21

1. Deep perineal pouch – A potential space between the pelvic floor superiorly, and the perineal membrane inferiorly. It contains part of the urethra and the external urethral sphincter. In males, it also contains the bulbourethral glands and the deep transverse perineal muscles.
2. Perineal membrane – A layer of tough fascia, which is perforated by the urethra and vagina. The role of the membrane is to provide attachment for the muscles of the superficial external genitalia, and to help support the pelvic viscera.
3. Superficial perineal pouch – A potential space between the perineal membrane superiorly, and the perineal fascia inferiorly. It contains the erectile tissues that form the penis and clitoris, and three muscles – the ischiocavernosus, bulbospongiosus and superficial transverse perineal muscles. The greater vestibular glands (Bartholin’s glands) are also located in the superficial perineal pouch.
4. Deep perineal fascia – Fascia covering the superficial perineal muscles.
5. Superficial perineal fascia – It is continuous with the superficial fascia of the abdominal wall. The superficial fascia itself can be divided into superficial and deep layers. The superficial layer is fatty in structure, forming the labia majora and mons pubis in women.
6. This is followed by skin

Question 22

What is the perineal body?

Answer 22

The perineal body is an irregular and fibromuscular mass. It is located at the junction of the urogenital and anal triangles – the central point of the perineum. This structure contains skeletal muscle, smooth muscle and collagenous and elastic fibres.

Question 23

Where does the perineal body lie anatomically and what is its function?

Answer 23

Anatomically, the perineal body lies just deep to the skin. It functions as a point of attachment for muscle fibres from the pelvic floor and the perineum itself:
• Levator ani (part of the pelvic floor).
• Bulbospongiosus muscle.
• Superficial and deep transverse perineal muscles.
• External anal sphincter muscle.
• External urethral sphincter muscle fibres.

Question 24

What is the extra function of the perineal body in women?

Answer 24

In women, it acts as a tear resistant body between the vagina and the external anal sphincter, supporting the posterior part of the vaginal wall against prolapse. In men it lies between the bulb of penis and the anus.

Question 25

What is the innervation to the perineum?

Answer 25

Perineum is innervated by the pudental nerve and internal pudental artery.

Question 26

At what point in the pelvis does the aorta bifurcate?

Answer 26

Aorta bifurcates at the sacral promontory.