A&P II Module 10: The Reproductive System

Module 10: The Reproductive System

Learning Outcomes

• Anatomy and Physiology of Male Reproductive System

• Anatomy and Physiology of Female Reproductive System

Overview of the Reproductive System

• Common Functions of Male and Female Reproductive Organs:

  • Produce specialized cells for sexual reproduction (gametes)

    • Sperm: Male gametes

    • Ova (eggs): Female gametes

  • Facilitate the joining of male and female gametes via sexual intercourse (copulation)

  • Genetic material from gametes combines during fertilization, forming a Zygote - first cell of a new individual from which all body cells arise.

The Male Reproductive System

• Purpose: Produces sperm and transfers sperm to female reproductive tract.

• Key Components:

  • Testes

  • Scrotum

  • Epididymis

  • Penis

  • Ducts and glands (seminal vesicles, prostate gland, bulbourethral glands)

Male Reproductive System: Scrotum

• Definition: Skin-covered muscular sac containing the testes

• Anatomical Features:

  • Extends from the body behind the penis

  • Scrotal septum divides scrotum into 2 compartments

  • Cremaster Muscles: Cover each testis for thermoregulation

  • Raphe: Medial thickening on the exterior surface

Male Reproductive System: Testes

• Function: Male gonads that produce sperm and androgens (e.g., testosterone)

• Structure: Each testis surrounded by two tunics:

  • Tunica Vaginalis: Outer layer

  • Tunica Albuginea: Inner layer, forming septa that divide into ~250 lobules each containing seminiferous tubules

• Spermatogenesis: Occurs within seminiferous tubules where sperm cells develop.

Male Reproductive System: Spermatogenesis

• Definition: Process of sperm production, begins at puberty and continues throughout a man's life.

• Duration: A cycle takes about 64 days; new cycles every 16 days

• Decline: Sperm counts may decline after age 35

In-Class Activity #1

Compare and contrast Mitosis and Meiosis in terms of the number of cells produced, if the cells produced are haploid or diploid and if the cells produced are identical or nonidentical.

Mitosis = 2 cells (Diploid / identical)

Meiosis = 4 cells (Haploid / non-identical )

Stages of Spermatogenesis

1. Mitosis of Spermatogonia:

   • One daughter cell remains a spermatogonial stem cell

   • The other becomes a Primary Spermatocyte

2. Meiosis I: Primary spermatocyte becomes a Secondary Spermatocyte

3. Meiosis II: Secondary spermatocytes become Spermatids

4. Spermiogenesis: Transforms spermatids into Spermatozoa (sperm)

In-Class Activity #2

Describe the process of spermatogenesis.

Basically, the stages above!

Structure of Spermatozoa

• Components:

  • Head: Contains genetic material (DNA)

  • Mid-piece: Contains mitochondria for ATP production

  • Tail: Provides motility

Male Reproductive System: Epididymis

• Function: Coiled tube attached to testis where sperm mature.

• Storage: Sperm are stored in the tail of the epididymis until ejaculation.

Male Reproductive System: Duct System

• Process During Ejaculation:

  • Sperm exit epididymis, move to ductus deferens (vas deferens)

  • Ductus Deferens: Thick muscular tube, aligned with connective tissue, blood vessels. Cut during vasectomy for sterilization.

  • From vas deferens, sperm enters ejaculatory duct to combine with seminal fluid.

Male Reproductive System: Semen

• Composition: Thick, milky fluid expelled during ejaculation.

  • Only 5% of semen is sperm; seminal vesicles, prostate, and bulbourethral glands contribute to this fluid.

  • Passage: Sperm moves from ejaculatory duct to the urethra and then exits the penis.

In-Class Activity #3

The vas deferens (ductus deferens) is cut and sealed during a vasectomy as a means of birth control. Explain how this would result in surgical sterilization.

Blocks the path sperm takes to exit the male reproductive system.

Male Reproductive System: Penis

• Definition: Male copulatory organ.

• Anatomical Structures:

  • Root and shaft that ends in glans penis (with prepuce/foreskin) covering glans.

  • Internal structure consists of spongy urethra and three cylindrical bodies of erectile tissue:

    • Corpus Spongiosum: Surrounds urethra, forms glans and bulb of penis

    • Corpora Cavernosa: Paired dorsal erectile bodies

Male Reproductive System: Testosterone

• Production: Testosterone produced by Leydig cells in testes.

• Effects of Testosterone:

  • Increase during puberty; essential for muscle development and spermatogenesis.

  • Induces male secondary sex characteristics, such as body and facial hair, deep voice, increased muscle mass.

Male Reproductive System: Testosterone Regulation

1. Hypothalamus releases GnRH to stimulate anterior pituitary.

2. FSH and LH are released:

   • LH stimulates Leydig cells for testosterone release.

   • FSH stimulates Sertoli cells for androgen-binding protein (ABP) release, which concentrates testosterone.

3. Feedback Mechanism:

   • Inhibin from Sertoli cells negatively feeds back to inhibit FSH release.

   • Testosterone negatively feeds back to inhibit GnRH, FSH, and LH.

In-Class Activity #4

Draw a diagram/flow chart to explain the roles of the hypothalamus, the anterior pituitary, Sertoli cells, Leydig cells, GnRH, FSH, LH, testosterone, ABP and inhibin in testosterone regulation

In-Class Activities

1. Compare and Contrast: Mitosis vs. Meiosis: in number of cells produced, haploid/diploid status, and identical/nonidentical qualities.

2. Describe Spermatogenesis: Explain the entire process and stages involved.

3. Diagram Flow Chart: Illustrate roles of hypothalamus, anterior pituitary, Sertoli cells, Leydig cells, GnRH, FSH, LH, testosterone, ABP, and inhibin in testosterone regulation.