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.