Detailed Notes on the Reproductive System

Reproductive System

Overview

• The reproductive system has male and female versions.
• Understanding the reproductive system is crucial for assessing patients, including knowing their name, age and sex.
• Sex-specific structures exist, with high emphasis on hormone knowledge.

Gonads

• Gonads (testes and ovaries) are both exocrine and endocrine.
• They produce sex hormones.
• Main male hormone: Testosterone (produced by the testes).
• Main female hormones: Estrogen and progesterone (produced by the ovaries).
• A normal male has two testes.
• A normal female has two ovaries (right and left).
• The 23rd pair is the sex chromosome pair (XX for female, XY for male).

Cell Replication

• Mitosis and meiosis occur in the gonads.
• Mitosis replicates cells until puberty, then meiosis begins.
• Review the products of mitosis and meiosis.
• Mitosis produces a diploid count (46 chromosomes).
• Meiosis produces a haploid count (23 chromosomes for fertilization).
• 23 chromosomes from the egg + 23 chromosomes from the sperm = 46 chromosomes.
• Meiosis offers genetic variability.
• Mitosis produces identical cells.

Clinical Relevance: Sex vs. Gender

• Establish a healthy rapport with patients through trust and safety.
• Sex is determined by physiology and anatomy (presence of ovaries/testes, etc.).
• Female: vaginal tract, two ovaries, fallopian tubes, uterus.
• Male: two testes, vas deferens, prostate gland, penile organ
• Gender is a social construct and a patient's identity.
• Medical decisions are based on anatomical presence.

Default Sex: Female

• The default sex is female, with the uterus initially developing the baby as female for the first five weeks of pregnancy.
• If the Y gene is present (specifically the SRY gene), development redirects to male parts.
• The SRY gene activates testosterone, converting ovaries into testes and fallopian tubes into the vas deferens.

Pregnancy and Technology

• Sex determination is possible via ultrasound at week 20.
• NIPT (Non-Invasive Prenatal Testing) screen can determine sex as early as week 10 via maternal blood draw.
• NIPT analyzes fetal cells for XX or XY chromosomes.

Homologous Structures

• Homologous structures have the same function but look different in males and females (e.g., ovaries and testes).
• AMAB: Assigned male at birth.
• Mesonephric (Wolffian) duct: Male.
• Paramesonephric (Mullerian) duct: Female.
• In healthy development, only one duct prevails.

SRY Gene Influence

• With the SRY gene, the paramesonephric duct degenerates, and the mesonephric duct becomes the vas deferens.
• Without the SRY gene, the paramesonephric duct develops into fallopian tubes.
• The mesonephric duct regresses in females because they do not need the vas deferens.

Reproductive Structures: Female vs. Male

• Female reproductive organs are inside the pelvic cavity, necessitating pelvic exams.
• Male organs are outside the pelvic cavity (testes in the scrotum, penile organ).

Urethra Differences

• The male urethra is longer.
• The three regions of the male urethra include the spongy (penile) urethra, which is the longest.
• Two bodily fluids pass through the male urethra: urine and sperm (semen).
• Only urine passes through the female urethra.

Scrotum

• The scrotum is a sac lined with skin and smooth muscle (cremaster muscle).
• The cremaster muscle regulates testes temperature for optimal sperm production by contracting and relaxing the scrotum to raise and lower the testes.
• Smooth muscle is involuntary.

Infertility Case Study

• High testes temperature is unsuitable for high quality sperm. A male patient spending four hours daily in a hot tub was advised to stop. The couple conceived in two months.
• Mitosis allows the capacity to eventually produce healthier sperm.
• Pelvic floor muscles exist in both males and females, Males can perform pelvic floor exercises.

Sperm Production

• Males produce sperm constantly with good testosterone levels (though quality may vary).

• Females have a five-day window around ovulation, releasing one egg.

• Couples are taught to recognize physical signs of fertility for strategic timing.

• High-quality sperm is correlated with sperm motility.

• Factors include the presence of an active tail, tail length, and sperm activity.

• Sperm must swim a long distance to reach the egg after deposition, they have to be worthy.

Male Accessory Glands

• Three accessory glands: seminal vesicles, prostate gland, bulbourethral glands.
• From superior to inferior: seminal vesicle, prostate, bulbourethral.
• Only the seminal vesicle and prostate glands are exclusive to males.
• Accessory glands produce substances to help sperm survive in the female reproductive system.

Seminal Vesicles

• The seminal vesicles (paired) contribute 60% of semen volume.

• Sperm: the gamete with 23 chromosomes (head, neck, tail).

• Semen: sperm + fluids for survival, it has MREs.

• Seminal vesicles secrete fructose (a carbohydrate) for sperm metabolism and activity.

Vaginal Tract

• The vaginal tract is acidic, presenting a challenge for conception.
• Sperm clump together upon deposition for strength in numbers.
• Some sperm die due to the acidic environment, while the surviving central sperm remain motile.

Prostate Gland

• The prostate gland contributes 30% of semen volume.

• Prostate fluid contains citric acid which supplies ATP for sperm motility.

• Enzymes from the prostate gland break down semen clots for sperm mobility.

• Prostate fluid is alkaline to neutralize vaginal acidity.

Testes and Sperm Production

• Testes contain coiled seminiferous tubules which is the only place where sperm is produced.

• Mature, high-quality sperm are stored in the epididymis.

• Sperm lasts for about 24 - 48 hours.

Vas Deferens and Ejaculation

• Stored sperm passes through the ductus deferens (vas deferens), which goes over and behind the urinary bladder.

• Vasectomy involves cutting the vas deferens.

• Sperm travels up the vas deferens and releases into the urethra.

• Semen is formed in the urethra.

• Sperm travels down the urethra and collects secretions from the seminal vesicle, prostate gland, and bulbourethral gland during ejaculation releasing semen into the vaginal tract.

• Moderate correlation between sperm quality and frequency of ejaculation; refraining from masturbation can impact sperm quality.

Bulbourethral Glands

• Bulbourethral glands lubricate the penis during intercourse and contribute 10% of fluid to semen.

• Vas deferens transports only sperm into the urethra.

• Semen passes only through the urethra.

Penile Structures

• The corpus cavernosum is responsible for the process of erection and fills with blood.
• The corpus spongiosum: semen and urine is released through the urethra.