Male reproductive organs (Male reproductive system)

Abstract

The male reproductive system consists of the penis, testes, epididymis, ejaculatory ducts, prostate, and accessory glands. These organs function together to produce sperm and deliver semen from the testes via ejaculation. For more information on the embryological development of the male reproductive system, see development of the reproductive system.

Penis

Function

Urination and release of semen

Gross anatomy [1][2]

Primarily composed of erectile tissue, blood vessels, nerves, and connective tissue

Structure

Arteries[2][3][1]

Course Supplies
Internal pudendal artery
  • External genitalia

Bulbourethral artery

Deep artery of the penis
  • Erectile tissue
Dorsal artery of the penis
Urethral artery
  • Glans of the penis
External pudendal artery

Veins

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

Lymphatics

Structure Lymph nodes Course
Perineum, penis, and scrotum Superficial inguinal lymph nodes external iliac nodes → para-aortic nodes
Glans penis Deep inguinal lymph nodes → internal iliac nodes → common iliac nodes → para-aortic nodes
Corpora cavernosa Internal iliac nodes → common iliac nodes → para-aortic nodes

Innervation

Innervation Structures Function
Parasympathetic Pelvic splanchnic nerves (S2-S4) Erection (see below)
Sympathetic Hypogastric nerve (T11-L4) Emission (see below)
Sensory Dorsal nerve of the penis (a branch of the pudendal nerve) Innervates the skin, prepuce, and glans

Point and Shoot": Parasympathetic Points it up (erection), Sympathetic Shoots out the semen (ejaculation).

Microscopic anatomy [1][2]

Embryology [1]

Testes, scrotum, and spermatic cord

  • The testes are paired organs composed of seminiferous tubules, the site of spermatogenesis. They are also responsible for the secretion of male sex hormones.
  • The scrotum encases the testes and is connected to the abdominal wall via the spermatic cord.

Gross anatomy

Structure [1][2][4]

Remember the spermatic cord layers with “TIE turns into ICE”:
- Transversalis fascia Internal spermatic fascia
- Internal oblique → Cremasteric muscle and fascia
- External oblique → External spermatic fascia

Vasculature, lymphatics, and innervation of the testes and scrotum [4]

Testes Scrotum
Arteries
Veins
  • Scrotal veins drain to external pudendal vein

Lymphatics

Autonomic Innervation

  • Abdominal aortic plexus
  • T10 → testicular plexus
Motor innervation
  • None
  • Genital branch of the genitofemoral nerve → cremasteric muscle contraction
  • See cremasteric reflex
Sensory innervation
  • Genitofemoral nerve → genital branch (L2) → tunica vaginalis of the testes
  • Anterior scrotal nerves (genital branch of the genitofemoral nerve and ilioinguinal nerve)
  • Posterior scrotal nerves (perineal branch of the internal pudendal nerve and posterior femoral cutaneous nerve)

Microscopic anatomy

Microscopic anatomy [1][2]

Spermatogonia

  • Description: Undifferentiated germ cells lining the seminiferous tubules
    • Type A (dark): do not undergo mitosis
    • Type A (pale): form type B spermatogonia
    • Type B: undergo mitosis → mature into primary spermatocytes
  • Function: site of primary spermatocyte production

Sertoli cells

  • Description
    • Columnar epithelial cells lining seminiferous tubules (non-germ cells)
    • Homologous to granulosa cells in females
    • Connected to one another via tight junctions
      • Form the blood-testis barrier: separation of gametes in seminiferous tubules from the immune system
    • Sensitive to temperature: ↑ temperature (e.g., due to cryptorchidism) → inhibin B secretion and ↓ production of spermatozoa
  • Function

Leydig cells

Sperm

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

Spermatogenesis and spermiogenesis

Spermatogenesis and spermiogenesis [1][2]

Spermatogenesis

Spermiogenesis

GONIUM is GOING be sperm: speramtogonia → spermatid. ZOON ZOOMS to the egg: mature spermatozoon travel to the egg.

Embryology

Embryology [1]

Epididymis, ductus deferens, and accessory glands

Epididymis [1]

  • Gross anatomy: long, coiled duct along the posterior aspect of the testis → distal end is continuous with ductus deferens
  • Function
    • Storage and maturation of spermatozoa
    • Propulsion of spermatozoa into the ductus deferens
  • Embryology: derived from the mesonephric duct (differentiation requires testosterone)

Ductus deferens [1]

Ejaculatory ducts [1]

Accessory glands

Prostate (see below)

Seminal vesicles [2]

Bulbourethral gland (Cowper gland) [2]

Prostate gland

An accessory gland of reproduction located at the base of the bladder and composed primarily of glandular, fibrous, and smooth muscle tissue.

Function [2]

Secretion of:

Gross anatomy [1][2]

Structure

Vasculature, lymphatics, and innervation of the prostate gland [3][6]

Arteries
Veins
  • Prostatic venous plexus → internal iliac vein → internal vertebral plexus (Batson plexus)
    • Located between the true and false capsule
    • Covered by the anterior prostatic fascia and the endopelvic fascia

Lymphatics

Sympathetic innervation
Parasympathetic innervation
  • Pelvic splanchnic nerves (sacral levels S2–S4) → pelvic plexus → cavernous nerves (located within the lateral prostatic fascia)
    • Prostatic secretion
    • Pelvic plexus and cavernous nerves are at risk of damage during radical prostatectomy.

Because of the prostate's lymphatic drainage to the para-aortic lymph nodes, prostate cancer often metastasizes to the lumbar spine.

Microscopic anatomy [8][9]

Embryology [8]

References:[10][11]

Male sexual response

There are three parts of the male sexual response: erection, emission, and ejaculation.

Erection [12][2][13]

PDE-5 inhibitors (e.g., sildenafil) inhibit hydrolysis of cGMP → ↑ NO → vasodilation → prolonged erection

Ejaculation [12][2][15]

Emission

Expulsion

Remember the ejaculatory pathway of sperm with SEVEn UP: Seminiferous tubules → Epididymis → Vas (ductus) deferens → Ejaculatory duct → Urethra → Penis

Innervation of male sexual response: Point, Squeeze, and Shoot
1. Parasympathetic → Point (erection)
2. Sympathetic → Squeeze (ejaculation)
3. Somatic (pudendal nerve) → Shoot (emission)

Clinical significance

Penis

Testes and scrotum

Prostate

Other

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last updated 10/17/2019
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