Overview of Male and Female Reproductive Systems

Major male reproductive organs

Testes, epididymis, ductus deferens, seminal vesicles, prostate gland, bulbourethral glands, penis

Major female reproductive organs

Ovaries, uterine tubes, uterus, vagina, external genitalia, mammary glands

Function of the testes

Produce sperm and testosterone

What occurs in the seminiferous tubules

Spermatogenesis

Sertoli (sustentacular) cells

Support and nourish developing sperm; form blood-testis barrier

Leydig (interstitial) cells

Produce testosterone in response to LH

Pampiniform plexus

A venous network that helps cool arterial blood to maintain optimal testis temperature

Difference between ductus deferens and spermatic cord

Ductus deferens carries sperm; spermatic cord contains ductus, vessels, nerves, and cremaster muscle

Path of sperm from testis to oocyte

Seminiferous tubules → rete testis → epididymis → ductus deferens → ejaculatory duct → urethra → vagina → uterus → uterine tube

Components of semen

Sperm, seminal fluid, prostatic fluid, bulbourethral secretions

Structure of the penis

Three columns of erectile tissue: two corpora cavernosa and one corpus spongiosum

How an erection is produced

Parasympathetic stimulation increases blood flow into erectile tissue, compressing veins to maintain pressure

How sildenafil (Viagra) treats erectile dysfunction

Inhibits PDE5 enzyme, allowing cGMP to persist and promote vasodilation for erection

Y chromosome in sexual development

Contains SRY gene that initiates testis development and male differentiation

Hormones and enzymes in male development

Testosterone promotes internal male ducts; DHT shapes external genitalia

How female development occurs

In absence of Y chromosome and androgens, ovaries form and female structures develop

Causes of intersex conditions

Genetic mutations, hormone deficiencies, or exposure to androgens during fetal development

Meiosis

Cell division that reduces chromosome number by half, forming gametes (sperm or eggs)

Difference between meiosis and mitosis

Meiosis has two divisions, produces 4 haploid cells; mitosis produces 2 identical diploid cells

Diploid cell

A cell with 2 sets of chromosomes (46 in humans)

Haploid cell

A cell with 1 set of chromosomes (23 in humans), such as sperm or egg

Where spermatogenesis occurs

In the seminiferous tubules of the testes

Steps of spermatogenesis

Spermatogonia → primary spermatocyte → secondary spermatocyte → spermatid → spermatozoon

Where oogenesis occurs

In the ovaries

When oogenesis begins and ends

Begins before birth, continues at puberty, pauses at ovulation, completes upon fertilization

Folliculogenesis

The development of ovarian follicles from primordial to mature (Graafian) stages

What happens to the follicle after ovulation

It becomes the corpus luteum and secretes hormones

Hormones secreted by the corpus luteum

Progesterone and estrogen to maintain endometrial lining

Cells that secrete hormones in the testes

Leydig cells (testosterone)

Cells that secrete hormones in the ovaries

Granulosa and theca cells (estrogen); corpus luteum (progesterone)

GnRH and its function

Gonadotropin-releasing hormone from hypothalamus stimulates FSH and LH secretion

Role of FSH in males

Stimulates Sertoli cells and spermatogenesis

Role of LH in males

Stimulates Leydig cells to produce testosterone

Role of FSH in females

Stimulates follicle growth and estrogen production

Role of LH in females

Triggers ovulation and corpus luteum formation

What happens during the male reproductive cycle

GnRH → FSH & LH → spermatogenesis and testosterone production; negative feedback by testosterone

Phases of the female reproductive cycle

Follicular phase, ovulation, luteal phase

Hormones high in the follicular phase

FSH, estrogen

Hormone that surges to trigger ovulation

LH

What happens in the luteal phase

Corpus luteum