Male reproductive organs (Male reproductive system)

Overview

The male reproductive system consists of the testes, spermatic ducts, sex glands, penis, and scrotum. These organs function together to produce sperm and deliver semen from the testes and out of the body as part of the process of ejaculation. For more information on the embryological development of the male reproductive system, see development of the reproductive system.

Penis and genital ducts

Anatomy

Penis

The penis is the male genitourinary organ responsible for the transfer of sperm from the testis during sexual intercourse as well as the transfer of urine from the bladder. It is primarily composed of erectile tissue, blood vessels, nerves, and connective tissue.

Arteries, veins, and lymphatics

Arteries of the penis

Artery Anatomy
Internal pudendal artery
Perineal artery
  • Supplies superficial perineal muscles
  • Forms the transverse perineal branches and posterior scrotal branches

Bulbourethral artery

(artery of the bulb of the penis)

Urethral artery
Deep artery of the penis
Dorsal artery of the penis
External pudendal artery

Veins of the penis

Vein Anatomy
Deep dorsal vein of the penis
  • Single vein
  • Lies on the midline, in the dorsum of the penis
  • Travels deep to Buck fascia of the penis
  • Superficial to the tunica albuginea
  • Drains into the prostatic and pelvic venous plexuses
Superficial dorsal vein of the penis
  • Travels along the superficial and deep fascia
  • Forms external pudendal veins
  • Drains into the greater saphenous vein.

Lymphatics of the penis

Lymphatic Anatomy
Superficial inguinal lymph nodes
Deep inguinal lymph nodes
  • Drain pelvic organs
  • Drain into the internal iliac nodes, common iliac nodes, and the lumbar (paraaortic) nodes
Paraaortic lymph nodes (Left lumbar)

The testes and scrotum drain into different lymph nodes, which means that testicular tumors do not naturally disseminate to the scrotal lymph drainage. Therefore, it is important that testicular tumors are not biopsied to avoid seeding malignant cells into the scrotum.

Glands of the male reproductive tract

Seminal vesicles

Bulbourethral gland (Cowper gland)

Prostate gland

  • Composed of tubuloalveolar glands
  • Surrounded by smooth muscle, and a capsule (important for prostate cancer staging)
  • Central glands: submucosal glands
  • Peripheral glands: prostatic glands
  • Secretes citric acid, fibrinolysin, acid phosphatase, and other proteins, which make up 30% of semen

Prostate

Overview

The prostate gland is an accessory organ of reproduction composed of glandular, fibrous, and smooth muscle tissue. The prostate gland is located within the pelvis, posterior to the pubic symphysis, inferior to the bladder, anterior to the rectum, and superior to the perineal membrane. It is approximately 4 x 3 x 2 cm in size. The base of the prostate wraps around the neck of the urinary bladder, while the apex surrounds the proximal urethra. The part of the urethra that courses through the prostate gland is referred to as the prostatic urethra.

The prostate gland has two capsules:

  • External: false capsule; continuation of the pelvic fascia
  • Internal: true capsule

Gross anatomy

  • The prostate is divided into 5 lobes: the anterior, posterior, middle, right lateral, and left lateral lobes.
Lobe Characteristics
Anterior
Posterior

Middle

(median)

Lateral
  • Right and left lobes
  • Located on both sides of the urethra

The prostate gland can also be divided into functional zones:

Zone Characteristics
Transitional
  • Accounts for 10% of the prostate's tissue
  • Site of origin for 20% of prostate cancer
  • Location: proximal to the seminal colliculus (verumontanum)
  • Central part of the gland → enlarges in BPH
  • Contains 2 lateral lobes and a median lobe
  • Urethral crest → on the posterior midline
  • Surrounds the distal end of the preprostatic urethra
  • Prostatic ducts
    • Drain into the prostatic sinus, a groove on the sides of the urethral crest
  • Ejaculatory ducts (drain into the prostate)
Central
  • Accounts for 20–25% of the prostate's tissue
  • Site of origin for 1–5% of prostate cancer
  • Location: from the base of the prostate to the seminal colliculus (verumontanum)
  • Surrounds the ejaculatory ducts
Peripheral

Microscopic anatomy

Vasculature

Arteries

All arteries of the prostate are branches of the internal iliac artery.

Veins

  • Prostatic venous plexus
    • Located between the true and false capsule
    • Covered by the anterior prostatic fascia and the endopelvic fascia
  • Prostatic venous plexus → pudendal, vesical, and obturator plexus → internal iliac vein

Innervation

  • Sympathetic innervation → contraction of smooth muscle
    • Thoracolumbar levels L1–L2
  • Parasympathetic innervation → lead to prostatic secretion
    • Pelvic splanchnic nerves (sacral levels S2S4) → pelvic plexus → cavernous nerves (located within the lateral prostatic fascia)
    • At risk during radical prostatectomy

Lymphatics

Function

Testes and seminiferous tubules

Gross anatomy

Testes

  • Develop in the retroperitoneum, then descend into the scrotum
  • Located in the scrotum
  • Blood supply from the testicular artery
  • Venous drainage via the pampiniform plexus
  • Lymphatic drainage

Spermatogenesis and spermiogenesis

Sperm

Pathway of sperm during ejaculation: seminiferous tubules → epididymis → vas deferens → ejaculatory ducts → urethra penis

Spermatogenesis

  • Process by which spermatogenic stem cells become spermatids
  • Spermatogonia are located close to the basement membrane of seminiferous tubules.
  • Cells migrate from the basement membrane towards the luminal surface of seminiferous tubules.
  • Cells are arrested until puberty, when mitosis resumes.
  • Spermatogonia type A and B
    • Type A
      • Type A (dark): do not undergo mitosis
      • Type A (pale): forms type B spermatogonia
    • Type B
      • Undergoes mitosis
      • Matures into primary spermatocytes
  • Primary spermatocytes (4n, haploid) → secondary spermatocytes (2n, haploid) → spermatids (1n, haploid)

Spermiogenesis

  • Process by which spermatids become spermatozoa
    • Requires stimulation from testosterone
      • Formation of the acrosome
      • Condensation of genetic material
      • Spermatid elongation
      • Development of the flagellum

Sertoli cells

Leydig cells

Blood-testis barrier

  • Formed by tight junctions between Sertoli cells
  • Separates gametes in seminiferous tubules from the immune system
  • Divides seminiferous tubules into:
    • Basal compartment
      • Contains spermatogonia and immature primary spermatocytes
      • In contact with blood and lymph
    • Adluminal compartment
      • Contains mature spermatocytes and spermatids
      • Not in contact with blood and lymph

Histology

Testes

  • Covered by:
  • Interlobular septa divides the testis into testicular lobules
  • Each testicular lobule contains 1–4 seminiferous tubules
    • Seminiferous tubules connect to the rete testes (via tubuli recti)
    • Seminiferous tubules contain:

Male sexual response

Erection

Ejaculation

Emission

Expulsion

Pathologies

  • Gartner LP, Hiatt JL. Cell Biology and Histology. Lww; 2014.
  • Kaplan. USMLE Step 1 Anatomy Lecture Notes 2016. Kaplan Publishing; 2015.
last updated 11/24/2018
{{uncollapseSections(['a8cQOV0', 'b8cHOV0', 'v8cAoV0', 'jwc_ie0', 'Y8cnOV0', 'D8c1KV0', 'X8c9OV0'])}}