Male Reproductive System

What are the 2 main roles of the male reproductive system?

• Produce, maintain, & transport sperm

• Produce male s3x hormones (androgens - mostly testosterone)

What are the 4 components of the male reproductive system?

• Testes (gonads)

• Duct system

• Accessory glands

• External genetal!a

Label the following diagram

Where are the testes located, & what is the significance of this location?

• Testes located in scrotum (external to pelvis)

• Essential for temperature regulation & spermatogenesis

  • Needs to be 2-4 degrees cooler than core body temp

    • Issue if testes do not descend; can lead to infertility + cancer growth

What is the male reproductive system organised around?

Continuous duct pathway w/n the pelvis & perineum

For the testes, state:

• Where they are located & why this is significant

• What they are the site of

• What they are surrounded by

• Paired organs located in scrotum, positioned outside essential for sperm production

• Site of:

  • Spermatogenesis in seminiferous tubules

  • Testosterone production in Leydig cells

• Surrounded by tunica albuginea (tough fibrous capsule)

  • Maintains testicular structure so that sperm aren’t being squashed - there is a higher risk of damage from being positioned on the outside)

What is the tunica vaginalis?

Peritoneum which has been dragged from the gut, which produces fluid to allow for movement & reduce friction b/w scrotum & testes

What is a hydrocele?

A fluid-filled sac around the scrotum which contributes to scrotal swelling & hernias if not completely sealed off from the abdomen

• Forms if the ligamentous remnant of processus vaginalis is not completed sealed off once a child is born

• Can lead to hernias or fluid from gut leaking into tunica vaginalis of testis

Label the following diagram of the testes (ignore the lines on the right side of the diagram)

Describe the process of testicular descent

1. Testicles develop in posterior abdominal wall (posterior to the kidneys)

2. Testicles descend into scrotum with the epididymis during foetal development

3. Testes drag the spermatic cords & blood vessels with them as they travel through the inguinal canal & deep ring

What is a retractile teste?

When a teste retracts further upwards into the inguinal canal before descending again

• Possibility of getting stuck

• Different to if the teste just never descends

Are the testicles always even after birth? Describe what usually happens, & any clinical implications which may occur if something goes wrong

• Common for one testicle to be higher than another after birth

• Teste hasn’t descended after ~1 year → may require surgery

  • Surgery to tighten the deep ring; prevent the teste from retracting

Name the 2 muscles in the scrotum involved in thermoregulation

• Dartos muscles

• Cremaster muscles

Describe the dartos muscles, in terms of:

• Composition

• Innervation

• Appearance & the significance of this

• Smooth muscle

• Autonomic innervation

  • Cannot be controlled

• Gives scrotum wrinkled appearance

  • Can get smaller or larger depending on temperature (change surface area to alter rate of heat loss)

Describe the cremaster muscles, in terms of:

• Composition

• What it is a continuation of

• What happens when it contracts

• Skeletal muscle

• Continuation of internal oblique muscle (abdominal muscle)

• Contraction → pulls scrotum upwards to elevate the testes

  • Cremaster muscle wrapped all the way around the testes

Label the following diagram of the scrotum

Describe the epididymis in terms of its:

• Shape & location

• Functions

• Divisions

• C-shaped structure on posterior testis

• Functions:

  • Sperm maturation

    • Made in testes but matures in epididymis

  • Sperm storage

• Divisions:

  • Head

  • Body

  • Tail (continuous w/ vas deferens)

  • *Sperm transferred from testes → epididymis via head → body → tail

Label the following diagram of the testis (ignore the left lines on the diagram)

For the vas deferens, state:

• What it is

• Where it runs

• What it joins with & what it forms

• Function

• Thick-walled muscular tube transporting sperm

• Runs from epididymis → inguinal canal → pelvis

• Joins duct of seminal vesicle → ejaculatory duct

• Function: propels sperm during ejaculation via peristaltic contractions

What is a vasectomy?

A contraception method when the tube carrying sperm is cut

Label the following diagram

For the seminal vesicles, state:

• What type of structure they are

• Where they are located

• Role

• What they join with & what they form

• Paired glands

• Posterior to bladder & superior to prostate gland

• Secrete fructose-rich, alkaline fluid → support sperm energy & survival

• Join w/ vas deferens → ejaculatory ducts

For the prostate gland, state:

• Where it is located

• Its role

• The names of its 3 zones

• Inferior to bladder, anterior to rectum, & surrounding the proximal urethra

• Secretes alkaline fluid → support sperm function & motility + contributes to semen composition

• Anatomical zones:

  • Peripheral zone

  • Central zone

  • Transitional zone

Describe the 3 zones of the prostate gland & the clinical implications of each of these zones

• Peripheral zone: site of where most malignant prostate cancers arise

• Central zone: surrounds ejaculatory ducts & urethra

  • cancerous growth in this area would constrict the urethra

• Transitional zone: site of BPH

  • Benign prostatic hyperplasia: enlarged prostate but not asymmetrical i.e. not cancerous growth

What causes pain with prostate cancer?

The inability to urinate from a narrowing of the urethra, not from the growth of the cancer itself

Label the following diagram

For the bulbourethral glands, state:

• Where they are located

• What they open into

• What they secrete & their role

• Small paired glands in urogenital region, inferior to the prostate

  • Underneath levator ani i.e, NOT a pelvic structure b/c they are below the pelvic floor

• Open into proximal spongy urethra

• Secrete pre-ejaculate mucus → lubricate urethra + neutralise residual acidity (from urine)

Label the following diagram

Label the following diagram

State the ejaculatory pathway

• Testis → epididymis → vas deferens + joins w/ seminal vesicles → ejaculatory duct → prostate → prostatic urethra

  • Sperm produced in testes

  • Sperm matures in epididymis

  • Sperm transported via vas deferens

  • Sperm mixed w/ glandular secretions

  • Sperm emptied through urethra during ejaculation

What is the urethra?

Common pathway for urine & semen

What are the 3 regions of the urethra?

1. Prostatic urethra

2. Membranous urethra: underneath the prostate, within perineum (where the bulbourethral glands are located), shortest portion

3. Spongy urethra: longest portion

Label the following diagram

What is the urethra supported by?

Urethra passes through perineum, & is supported by the pelvic floor structures during urination & ejaculation

For the peni!s, state:

• What it is

• What it is composed of

• Its function

• External copulatory organ

• Composed of erectile tissue (not muscle):

  • Corpus cavernosa: paired, fills with blood during erection

    • Would compress & seal off the urethra if the corpus spongiosum was not there

  • Corpus spongiosum: surrounds the urethra, prevents corpus cavernosa from compressing urethra during erection

    • Keeps urethra open to allow sperm to pass through

• Functions in urination & sexu@l reproduction

Label the following diagram of the pen!s

Describe the spatial relationships of the following structures within the pelvis:

• Bladder

• Rectum

• Prostate

• Seminal vesicles

• Vas deference

• Peritoneum

• Bladder: anterior to r3ctum

• R3ctum: posterior to pelvic organs

• Prostate: inferior to bladder + anterior to r3ctum

• Seminal vesicles: posterior to bladder

• Vas deferens: ascending from scrotum into pelvis via inguinal canal

• Peritoneum: reflecting b/w bladder & rectum → rectovesical pouch (unique to males, lowest point where fluid could accumulate e.g. due to burst appendix)

Label the following diagram

Label the following diagram

Name the vascular supply of the testes, prostate & pen!s

• Testes: testicular arteries (branch of gonadal arteries of abdominal aorta)

  • Testicular arteries go out of the inguinal ring through the inguinal canal → testes; testicular torsion cuts off the blood supply of testicular arteries

• Prostate: branches of internal iliac artery

• Pen!s: branches of internal pudenal artery

Describe the venous drainage of the male reproductive system

Generally parallel w/ arterial supply;

• Right side → IVC

• Left side → L renal vein

  • L renal vein crosses over abdominal aorta @ T12/L1-2 → IVC