Reproductive System: Overview

Tasks of the Reproductive System

The reproductive system is responsible for the creation and support of new life. Its main tasks include:

• Formation of gametes: Production of ova (egg cells) in females and sperm in males.

• Bringing gametes together: Sexual intercourse facilitates the meeting of male and female gametes.

• Fertilization: Fusion of gamete DNA forms a zygote.

• Support of new life: Gestation (pregnancy) and parturition (birth).

Common Male & Female Features

Homologues and Primary Reproductive Organs

Both sexes have homologous structures and primary reproductive organs called gonads (testes in males, ovaries in females). Accessory reproductive organs assist in gamete transport and support.

• Reproductive hormone secretion: Controlled by the hypothalamic-pituitary-gonadal axis, which regulates puberty and gamete production.

Meiosis and Chromosome Concepts

Meiosis is the process by which gametes are formed, reducing chromosome number by half.

• Chromosomes: Structures containing DNA; each has sister chromatids joined at a centromere.

• Diploid (2n): Cells with two sets of chromosomes (homologous pairs).

• Haploid (n): Gametes with one set of chromosomes.

• Autosomes: Non-sex chromosomes; sex chromosomes determine gender (XX = female, XY = male).

• Mitosis vs. Meiosis: Mitosis produces identical cells; meiosis produces gametes with genetic variation.

• Meiosis I: Reduction division; homologous chromosomes form tetrads, undergo synapsis and crossing over.

• Meiosis II: Equational division; separates sister chromatids.

Example: Meiosis creates four genetically unique gametes from one diploid cell.

Anatomy of the Male Reproductive System

External Genitalia

• Scrotum: Contains testes; septum divides, cremasteric and dartos muscles regulate temperature.

• Penis: Root, body, glans penis, foreskin (prepuce).

Testes

• Endocrine function: Produces testosterone.

• Exocrine function: Produces sperm and fluid.

• Tunica vaginalis: Protective covering.

• Tunica albuginea: Forms septa and lobules.

• Seminiferous tubules: Site of spermatogenesis.

Spermatic Cord and Ducts

• Spermatic cord: Contains vas deferens, blood vessels (testicular artery, pampiniform plexus), nerves, lymphatics.

• Epididymis: Sperm maturation and storage; sperm are nonmotile until ejaculation.

• Ductus (vas) deferens: Transports sperm via peristalsis.

• Ejaculatory duct: Connects vas deferens to urethra.

• Urethra: Prostatic, membranous, and spongy regions.

Accessory Glands

• Seminal glands (vesicles): Produce 60% of semen; yellow, viscous, alkaline, contains fructose.

• Prostate: Produces 30% of semen; milky, acidic, contracts during ejaculation.

• Bulbourethral glands: Secrete clear mucus for lubrication.

Penis Structure

• Corpora cavernosa: Responsible for erection.

• Corpus spongiosum: Keeps urethra open during erection.

• Arteries: Deep and dorsal arteries supply blood.

• Perineum: Area between pubic symphysis and coccyx.

Anatomy of the Female Reproductive System

Ovaries

• Ligaments: Ovarian, suspensory, mesovarium.

• Blood supply: Ovarian and uterine arteries.

• Tunica albuginea: Protective layer.

• Cortex: Contains follicles; medulla: contains blood vessels.

Uterine Tubes (Fallopian Tubes)

• Infundibulum: With fimbriae to capture ovulated oocyte.

• Ampulla: Site of fertilization.

• Isthmus: Narrow region.

• Wall: Epithelium, smooth muscle, mesosalpinx (peritoneum).

Uterus

• Body, fundus, isthmus: Main regions.

• Cervix: Internal and external os; PAP smear screens for cancer.

• Support: Cardinal, uterosacral, round ligaments; broad ligament (mesometrium, mesosalpinx, mesovarium).

• Wall: Endometrium (functional and basal layers), myometrium, perimetrium.

• Blood supply: Uterine arteries → arcuate → straight & spiral arteries.

Vagina

• Fornices: Recesses around cervix.

• Hymen: Membrane partially covering vaginal opening.

• Wall: Adventitia, muscularis, mucosa.

External Genitalia (Vulva)

• Mons pubis: Fatty area over pubic bone.

• Labia majora and minora: Folds protecting vestibule.

• Vestibule: Contains clitoris, urethra, vagina, hymen, greater vestibular glands.

• Perineum: Area between vulva and anus; pelvic floor muscles support organs.

Breast (Mammary Glands)

• Modified sweat glands: Produce milk.

• Areola and nipple: Central structures.

• Lobes: Suspensory ligaments support.

• Glandular alveoli: Make milk, which travels through lactiferous ducts to sinuses.

• Breast cancer: Malignant growth in breast tissue.

Genetics and Patterns of Inheritance

Vocabulary of Genetics

• Diploid: 22 pairs of homologous chromosomes and 1 pair of sex chromosomes.

• Sex determination: XX = female, XY = male; SRY gene on Y chromosome triggers male development.

• Karyotype: Chromosomes arranged by size during metaphase.

• Gene: DNA segment coding for a protein (trait).

• Locus: Location of a gene on a chromosome.

• Alleles: Different forms of the same gene; homozygous (same), heterozygous (different).

• Dominant allele: Suppresses partner; recessive allele: can be suppressed.

• Genotype: Genetic makeup; phenotype: outward expression.

Example: Tt genotype results in T phenotype if T is dominant.

Genetic Variation

• Independent assortment: Random distribution of chromosomes during meiosis.

• Crossing over: Exchange of genetic material between homologous chromosomes.

• Random fertilization: Any sperm can fertilize any egg.

Patterns of Inheritance

• Dominant-recessive inheritance: One allele masks the other.

• Codominance: Both alleles are expressed (e.g., blood type AB).

• Sex-linked: Traits carried on sex chromosomes.

• Polygenic traits: Controlled by multiple genes (e.g., skin color, height).

• Other factors: Environmental influences can affect traits.

Embryological Development of the Reproductive System

Developmental Timeline

• 5th week: Gonadal ridges form; primordial germ cells migrate.

• 6th week: Mesonephric and paramesonephric ducts develop.

• 7th week: XY embryos produce testosterone; mesonephric duct forms male structures.

• 8th week: XX embryos lack testosterone; paramesonephric duct forms female structures.

• 7th month: Gonads descend; gubernaculum guides descent.

Male Reproductive Physiology

Male Sexual Response

• Erection: Blood fills corpora cavernosa.

• Ejaculation: Expulsion of semen.

• Resolution: Return to non-aroused state.

Spermatogenesis

Spermatogenesis is the process of sperm production in the seminiferous tubules.

• Diploid (2n) to haploid (n): Meiosis reduces chromosome number.

• Reduction division: Synapsis, tetrads, crossover.

• Equational division: Separates chromatids.

• Interstitial endocrine cells: Produce testosterone.

• Sustentocytes (Sertoli cells): Support developing sperm; form blood-testis barrier.

• Spermatogonium: Stem cell; primary and secondary spermatocytes, spermatids, spermatozoa.

• Sperm structure: Tail (flagella), midpiece (mitochondria), head (nucleus, acrosome).

Hormone Regulation

• GnRH: Gonadotropin-releasing hormone from hypothalamus.

• LH: Luteinizing hormone; stimulates testosterone production.

• FSH: Follicle-stimulating hormone; stimulates spermatogenesis.

• Inhibin: Inhibits FSH.

• Testosterone: Promotes male secondary sex characteristics.

Puberty

• Testosterone effects: Growth of muscle, bone, facial hair, deepening of voice.

Female Reproductive Physiology

Oogenesis

Oogenesis is the process of ovum (egg) formation in the ovaries.

• Before birth: Primordial germ cells migrate to ovary; form oogonia.

• Mitosis: Produces primary oocytes; arrest in prophase I.

• Each month: One primary oocyte completes meiosis I → secondary oocyte + first polar body (arrests in metaphase II).

• Fertilization: Sperm penetration completes meiosis II; DNA merges to form zygote.

Stages of Follicle Development

• Primordial follicle → primary follicle → secondary follicle: Granulosa and theca folliculi develop.

• Vesicular (Graafian) follicle: Contains antrum, corona radiata, zona pellucida.

Ovarian Cycle

• Follicular phase: Follicle growth.

• Ovulation: Release of oocyte.

• Luteal phase: Corpus luteum forms; if no pregnancy, becomes corpus albicans.

Hormonal Regulation of Female Cycle

• Hypothalamus: Releases GnRH.

• Pituitary: Releases LH and FSH.

• Ovary: Produces estrogen and progesterone.

• Estrogen: Promotes endometrial and follicle growth.

• Progesterone: Prepares endometrium and breasts for pregnancy.

• Uterus: Menstrual, proliferative, and secretory phases; functional and basal layers.

Female Sexual Response and Development

• PSNS and SNS: Parasympathetic and sympathetic nervous systems regulate arousal and orgasm.

• Childhood: Low hormone levels.

• Puberty: Increased GnRH, estrogen, progesterone; menarche (first menstruation).

• Menopause: Decreased estrogen; symptoms include vaginal dryness, hot flashes, decreased bone mass.

Patterns of Inheritance: Table

Key Equations and Concepts

Chromosome Number in Gametes

Gametes are produced by meiosis, reducing chromosome number:

Genotype and Phenotype

Relationship between genotype and phenotype:

(if T is dominant)

Genetic Variation

Number of possible gamete combinations due to independent assortment:

(where n = number of chromosome pairs)

For humans: possible combinations

Summary Table: Male vs. Female Reproductive Anatomy

Additional info:

• Some details about embryological development and hormone regulation were inferred for completeness.

• Tables were recreated to clarify inheritance patterns and anatomical comparisons.