Male Reproductive System: Accessory Glands

Male Reproductive System: Accessory Glands

Introduction

• The lecture focuses on the accessory glands of the male reproductive system.
• These glands are crucial as they contribute most of the fluid in semen.
• Three accessory glands: seminal vesicles, prostate gland, and bulbourethral glands.
• The lecture will cover their structure and function.

Accessory Glands Overview

• Accessory glands provide most of the fluid found in semen.
• Semen is composed of sperm and fluids from the accessory glands.
• The three glands are seminal vesicles, prostate, and bulbourethral glands.

Seminal Vesicles

• There are two seminal vesicles, each about 5 cm long.
• They are active secretory glands that produce a significant amount of fluid.
• Contribution: Approximately 60\% of semen fluid comes from the seminal vesicles.
• The fluid is mucus-like and alkaline.

Alkaline Nature of Seminal Vesicle Fluid

• The alkalinity helps neutralize the acidic environment of the female reproductive tract (vagina, cervix).
• Protection: Neutralizing the acidity protects sperm from damage.
• Location: Seminal vesicles are situated on the posterior wall of the bladder.

Components of Seminal Vesicle Fluid

• Fructose:
  • Produced by cells lining the seminal vesicle gland.
  • Acts as an energy source for sperm motility.
• Prostaglandins:
  • Special proteins that bind to smooth muscles in the male and female reproductive systems.
  • Stimulate muscle contraction.
  • Contribute to sperm motility and viability.
• Fibrinogen:
  • A protein that coagulates semen, forming a solid mass or plug.
  • The coagulation helps protect sperm by bringing them together.
  • Protection lasts while the alkaline fluid neutralizes the acidic environment in the female reproductive tract.
• The fluids are released at ejaculation, a process also known as emission.

Prostate Gland

• The prostate gland is a singular, donut-shaped gland.
• The urethra passes through the hole in the middle of the prostate.
• Location: Situated immediately underneath the bladder.
• Urine from the bladder empties into the prostatic urethra, as does fluid from the seminal vesicles and ductus deferens.

Microscopic Appearance and Function

• Composed of 30 to 50 tiny glands that connect to form the prostate.
• Each gland has a duct that empties into the prostatic urethra.
• Fluid made in these glands exits into the prostatic urethra.
• That prostatic fluid mixes with fluids from the seminal vesicles and ductus deferens.
• Smooth Muscle: The prostate contains smooth muscle that contracts, helping to expel fluid at ejaculation, and prostaglandins can trigger the contraction.

Prostate Size and Growth

• Grows slowly until puberty.
• From puberty to age 30, rapid growth occurs, requiring a lot of fluid due to sperm production.
• Ages 30 to 45: Growth becomes gradual.
• After age 45 it may increase in size.
• That increase in size can be normal or may cause issues.
• Problems arise if it grows inward towards the prostatic urethra.
• Inward growth can block urine flow, and may be problematic.
• Prostate cancer can spread and impact urine flow.

Prostatic Fluid

• It's a thinner, milky fluid.
• The milky appearance contributes to the whitish color of semen.
• It is slightly acidic and makes up 25\% to 30\% of semen volume.

Components of Prostatic Fluid

• Citric Acid:
  • Energy source for sperm.
• Proteolytic Enzymes (Fibrinolysin):
  • Digest proteins and break down the coagulate formed after ejaculation.
  • Important for sperm to break free and swim into the cervix and uterus after the vaginal environment is neutralized.
• Prostate-Specific Antigen (PSA):
  • A protein used in blood tests to detect prostate enlargement.
  • High PSA levels may indicate the need for further examination.
• Seminal Plasmin:
  • An antibiotic that prevents bacterial infections in the male and female reproductive systems.
  • Minimizes bacterial growth which would otherwise break down sperm.

Bulbourethral Glands

• Two small glands (about 1 cm) at the base of the penis.
• Have tiny ducts that empty into the urethra in the penis.

Secretions

• Secrete a thick alkaline mucus.
• The mucus is released prior to ejaculation.

Function

• The release of mucus neutralizes any acid in the urethra due to prior urine passage.
• The thick mucus has lubricating properties.
• Aids the flow of ejaculate through the urethra.

Semen Composition

• Semen is a combination of sperm and fluid from the seminal vesicles and prostate.
• Bulbourethral glands contribute a smaller amount.

Composition Breakdown

• 4\% sperm
• Under 1\% bulbourethral gland secretion
• 65\% seminal vesicle fluid
• 30\% prostatic gland fluid

World Health Organization (WHO) Standards for Semen

• Volume: Approximately 2 ml or more per ejaculate.
• Concentration: 15,000,000 sperm per ml.
• Total Sperm Count: More than 39,000,000 sperm per ejaculate.
• Motility: Over half need to be forward motile.
• Morphology: More than 4\% of sperm should have normal appearance.

Implications of Abnormal Semen Analysis

• If the semen sample does not meet the WHO standards, the male may have reduced fertility or be infertile.
• Semen analysis tests are common when couples struggle to conceive.

Sperm Morphology

• Normal sperm have a defined head, acrosome, and tail.
• Abnormal sperm can have various defects like a small acrosome, massive/small head, two heads/tails, or excess cytoplasm.
• A normal semen sample should have at least 4\% of normal-looking sperm.

Video Demonstrations

• Video shows sperm under a microscope showing forward motility.
• Some sperm swim in circles, indicating poor forward progressive motility.