Male and Female Reproductive Systems

Vasectomy

• Historically involved blocking the vas deferens.
• Modern procedures involve plugging or blocking the vas deferens to prevent sperm travel.
• Autoimmune response to sperm released into the body cavity can complicate reversal.
• Typically doesn't affect sex life or virility, as only sperm are removed from semen.
• Surgical procedure involves a small incision and plugging of the vas deferens.

Penis Structure and Function

• Key structures:
  • Corpora cavernosa: Main tissue of the penis.
  • Corpus spongiosum: Delicate, highly vascularized tissue within the corpora cavernosa.
  • Urethra: Exit for semen.
  • Glans penis: Contains the urethral opening.
• Erection mechanism:
  • Increased arterial flow.
  • Decreased venous outflow.
  • Blood engorgement of the corpora cavernosa.
• Testosterone is not essential for erections but may influence nocturnal erections.
• During erection, the corpora cavernosa becomes engorged with blood, putting pressure on veins and restricting outflow.

Baculum (Penis Bone)

• Humans lack a penis bone, but it is present in many other mammals.
• Different shapes of bacula can provide information about the species' evolution and structure.
• Baculum provides support during intercourse.
• Damage to the corpora cavernosa can be devastating due to its delicate nature and difficulty in repair.

Orgasm

• Brain imaging (MRI) shows pleasure centers activated during male ejaculation.
• Similar tests with females did not yield the same pleasure result.

Erectile Dysfunction (ED)

• Common condition affecting men of various ages and lifestyles.
• Often has a biological basis, such as obstruction of blood flow to the corpora cavernosa.
• Sildenafil (Viagra) treats symptoms temporarily but is not a cure.
• Cardiovascular disease is a common underlying cause.
• Statins and hypertensives treat the cardiovascular disease, while Viagra addresses the symptom.

Historical Treatments for ED

• Prostaglandin injections: Direct injection into the penis to produce an erection.
• Topical creams: Some success but less effective than other methods.
• Viagra: Relaxes smooth muscle and enhances blood flow to the corpus cavernosum.

Nitric Oxide and Erectile Function

• Nitric oxide is a stimulant for muscles, particularly in the cardiovascular system.
• It is the active ingredient in nitroglycerin.
• Nitric oxide is crucial for vasodilation and increased blood flow during erection.
• Cyclic guanine monophosphate (CGMP) is an intermediate signal in the nitric oxide pathway.
• Phosphodiesterase 5 (PDE5) is an enzyme in penis tissue that breaks down CGMP, causing the erection to subside.
• Viagra acts as a competitive binding agent for PDE5, inhibiting its action and prolonging the erection.

Viagra Efficacy and Side Effects

• Efficacy increases with dosage.
• Side effects include visual disturbances (e.g., altered color perception) due to the effect on other phosphodiesterases (PDE6) in the body.

Factors Affecting Male Reproduction

• Environmental factors: Endocrine disruptors can affect hormone balance.
• Genetic defects: Can impair testes function.
• Disturbed Sertoli cell function: Impairs sperm production.
• Testicular cancers.
• Leiden cell dysfunction: Leads to androgen insufficiency.
• Testicular maldescent: Testes do not descend during puberty.
• Hypospadias: Urethra is not straight, often corrected surgically.

Testicular Self-Examination

• Regular self-checks are important for detecting abnormalities.

Key Points on Male Reproductive System

• Review questions are good practice for exams.

Comparison of Male and Female Reproduction

• Learning objectives are guide for the main message.

Female Reproductive Anatomy

• Uterus, ovaries, oviducts (Fallopian tubes), vagina.
• Endometrium and myometrium in the uterus.
• Cervix: Sphincter between the vagina and uterus.
• Fimbriae: Fluffy structures around the oviduct opening.
• Early tissue development is the same in both sexes.

Clitoris and G-Spot

• Females have corpus cavernosum similar to males.
• The clitoris is homologous to the penis in terms of tissues.
• Existence of the G-spot is debated but may involve phosphodiesterases in vaginal tissue.

Oocyte Count

• Conventional wisdom: Females are born with all the eggs they will ever produce.
• Germ cells or number of follicles in utero at three, six, and nine months old.
• Mitotic proliferation of germ cells forming primary oocytes and then producing a primary oocyte.

Egg Development

• Foetal germ cells enter meiosis 1.
• Primary Oocytes go through a series of meiotic division phases. The one with a little zero next to it, it's shorthand for primary.
• Primary oocytes arrest development for up to 50 years.
• Meiosis produces one egg and three polar bodies.
• There are two stasis phases in oogenesis: before birth and after puberty.
• Final meiotic division occurs upon fertilization.

Oogenesis

• DNA replication occurs before birth.
• Meiosis 1 is completed after puberty.
• Final division occurs with fertilization.

Male vs. Female

• Primary oocytes are formed at birth, unlike spermatids.
• One oocyte is produced per meiosis, compared to four sperm.
• Oocytes are as old as the female, whereas sperm are only a month or two old.

Oocyte Count Research

• 1950s research suggested limited egg numbers.
• 2004 mice studies showed more eggs were found.
• Stem cell research by Professor Tilley aimed to generate new eggs from stem cells.
• Controversial, with replication issues.
• Protect eggs by avoiding too many x-rays and other health concerns that may damage oocytes.

Oocytes

• Follicle: Structure in the ovary where the oocyte grows.
  • Analogy to hair follicle.
• Initial growth of the egg in the follicle is triggered by follicle stimulating hormone.
• Graphene: Mature follicle, ready to go.
• Key Structures that matter
  • Oocyte (egg).
  • Zona pellucida: Outer layer interacting with sperm.
  • Granulosa cells: Important for follicle function.
• During ovulation, the graafian follicle expels the egg together with the zona pellucida and the granulosa cells.
• Ovary is compartmentalized to support tissues and follicles.
• At puberty, follicles are reactivated.
• Granulosa cells signal for estrogen production.
• Have some diagrams from slides that will be used later on.

Ovulation

• Primordial Follicles is the immature follicle.
• Primary follicle is the developed primordial follicle.
• Secondary follicle is the growing mature follicle.
• Graphene follicle is the oocyte.
• Estrogen sends signals to the hypothalamus and pituitary in order to induce a hormonal surge to trigger ovulation.