Biological Male Pelvis

Question 1

Boundaries of the perineum

Answer 1

Anatomical-
- Anterior – pubic symphysis.
- Posterior – tip of the coccyx.
- Laterally – inferior pubic rami and inferior ischial rami, and the sacrotuberous ligament.
- Roof – pelvic floor.
- Base – skin and fascia.

Surface-
- Anterior – mons pubis in females, base of the penis in males.
- Laterally – medial surfaces of the thighs.
- Posterior – superior end of the intergluteal cleft

Question 2

Contents of the perineum

Answer 2

The perineum can be subdivided by a theoretical line drawn transversely between the ischial tuberosities. This split forms the anterior urogenital and posterior anal triangles.

Anal Triangle- is the posterior half of the perineum. It is bounded by the coccyx, sacrotuberous ligaments, and a theoretical line between the ischial tuberosities.
- Anal aperture – the opening of the anus.
- External anal sphincter muscle – voluntary muscle responsible for opening and closing the anus.
- Ischioanal fossae (x2) – spaces located laterally to the anus.

Urogenital Triangle- is the anterior half of the perineum. It is bounded by the pubic symphysis, ischiopubic rami, and a theorectical line between the two ischial tuberosities. The triangle is associated with the structures of the urogenital system – the external genitalia and urethra. The layers of the urogenital triangle (deep to superficial):
- Deep perineal pouch – a potential space between the deep fascia of the pelvic floor (superiorly) and the perineal membrane (inferiorly). It contains part of the urethra, external urethral sphincter, and the vagina in the female. In males, it also contains the bulbourethral glands and the deep transverse perineal muscles.
- Perineal membrane – a layer of tough fascia, which is perforated by the urethra (and the vagina in the female). The role of the membrane is to provide attachment for the muscles of the external genitalia.
- Superficial perineal pouch – a potential space between the perineal membrane (superiorly) and the superficial 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. The pouch is bounded posteriorly to the perineal body.
- Perineal fascia – a continuity of the abdominal fascia that has two components:
- Deep fascia: covers the superficial perineal muscles and protruding structures (e.g. penis & clitoris).
- Superficial fascia is composed of a further two layers of fascia:
Superficial layer – continuous with Camper’s fascia of the anterior abdominal wall
Deep layer (Colles’ fascia) – continuous with Scarpa’s fascia of the anterior abdominal wall
- Skin – The urethral and vaginal orifices open out onto the skin.

Question 3

Anterior trunk of the internal iliac artery

Answer 3

• Obturator artery – Travels through the obturator canal with the obturator nerve and vein. It supplies the muscles of the thigh’s adductor region.
• Umbilical artery – Gives rise to the superior vesical artery, which supplies the superior aspect of the urinary bladder.
• Inferior vesical artery – Supplies the lower aspect of the bladder. In males, it also supplies the prostate gland and seminal vesicles.
• Middle rectal artery – Travels medially to supply the distal part of the rectum. It also forms anastomoses with the superior rectal artery (derived from the inferior mesenteric) and the inferior rectal artery (derived from the internal pudendal)
• Internal pudendal artery – Moves inferiorly to exit the pelvis via the greater sciatic foramen. Accompanied by the pudendal nerve, it then enters the perineum via the lesser sciatic foramen. It is the main artery responsible for the blood supply to the perineum.
• Inferior gluteal artery – The terminal branch of the anterior trunk. It leaves the pelvic cavity via the greater sciatic foramen, emerging inferiorly to the piriformis muscle in the gluteal region. It contributes to the blood supply of the gluteal muscles and hip joint.

Question 4

Posterior trunk of the internal iliac artery

Answer 4

• Iliolumbar artery – Ascends to exit the lesser pelvis, dividing into a lumbar and iliac branch. The lumbar branch supplies psoas major, quadratus lumborum and the posterior abdominal wall. The iliac branch supplies the muscles and bone around the iliac fossa.
• Lateral sacral arteries (superior and inferior) – Travel infero-medially along the posterior pelvic wall to supply structures in the sacral canal, and the skin and muscle posterior to the sacrum.
• Superior gluteal artery – The terminal branch of the posterior trunk. It exits the pelvic cavity via the greater sciatic foramen, entering the gluteal region superiorly to the piriformis muscle. It is the major blood supply to the muscles and skin of the gluteal region.

Question 5

Route of sperm

Answer 5

• produced in seminiferous tubules
• rete testis
• efferent ductules
• epididymis
• ductus (vas) deferens
• ejaculatory duct
• urethra

Question 6

Glans penis is made up from

Answer 6

Corpus spongiosum

Question 7

Which part of the penis runs along the ischial ramus?

Answer 7

The crus/crura

Question 8

Bulbospongiosus function

Answer 8

To empty the urethra of urine and semen

Question 9

Ischiocavernosus function

Answer 9

To assist in erection and ejaculation

Question 10

What is the name of the plexus of veins supplying the testis?

Answer 10

The pampiniform plexus – The right arises from the IVC, and the left from the left renal vein.

Question 11

Layers of tissue surrounding the testis, from superficial to deep.

Answer 11

Dartos muscle, external spermatic fascia, cremaster muscle, internal spermatic fascia, tunica vaginalis, tunica albuginea