BIOLOGY SS2 WEEK 9: REPRODUCTIVE SYSTEM IN VERTEBRATES

 Learning Objectives

• 1. Structure and functions of male and female mammalian reproductive system.
• 2. difference between male and female repoductive organs 
• 3. Structures of the gametes (sperms and ovum). 
• 4. Fertilization of development of embryo and birth

    Structure and Functions of Male and Female Mammalian Reproductive Systems

    The reproductive systems of mammals are specialized to produce, store, and transport gametes  (sperm and egg), facilitate fertilization, and support the development of offspring.

• Male Reproductive System

  The male reproductive system is responsible for producing and delivering sperm for fertilization. It consists of the following structures:

  A. Primary Reproductive Organs (Gonads) – Testes

  • The testes are the site of spermatogenesis (sperm production).
  • Located in the scrotum, which keeps them at a temperature lower than body temperature, essential for sperm development.
  • Leydig cells in the testes produce the male hormone testosterone, responsible for male secondary sexual characteristics.

  B. Secondary Reproductive Structures

  1. Epididymis – A coiled tube where sperm mature and are stored before ejaculation.
  2. Vas deferens – A duct that transports sperm from the epididymis to the urethra.
  3. Seminal vesicles – Produce a fructose-rich fluid that nourishes sperm and makes up a large portion of semen.
  4. Prostate gland – Secretes an alkaline fluid that neutralizes vaginal acidity and improves sperm motility.
  5. Bulbourethral glands (Cowper’s glands) – Produce mucus that lubricates the urethra.
  6. Penis – The external organ that delivers sperm into the female reproductive tract during c copulation.
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  Female Reproductive System

  The female reproductive system is designed for egg production, fertilization, pregnancy, and childbirth. It consists of the following structures:

  A. Primary Reproductive Organs (Gonads) – Ovaries

  • Ovaries produce ova (eggs) and secrete female sex hormones (estrogen and progesterone).
  • Oogenesis (egg formation) occurs in the ovaries.

  B. Secondary Reproductive Structures

  1. Fallopian tubes (Oviducts) – Transport the egg from the ovary to the uterus; the site of fertilization.
  2. Uterus – A muscular organ where the fertilized egg implants and develops into an embryo.
  3. Cervix – The lower part of the uterus that connects to the vagina; it expands during childbirth.
  4. Vagina – A muscular canal that serves as the passage for sperm during copulation and as the birth canal.
  5. Mammary glands – Present in females for milk production to nourish offspring after birth

  2. Differences Between Male and Female Reproductive Organs

  Feature	Male Reproductive System	Female Reproductive System
  Gonads	Testes	Ovaries
  Gametes	Sperm (produced in large numbers)	Egg/Ovum (produced once per cycle)
  Hormones	Testosterone	Estrogen and Progesterone
  External Organs	Penis, Scrotum	Labia, Clitoris
  Function	Produces and delivers sperm	Produces eggs, supports pregnancy
  Reproductive Ducts	Vas deferens, Urethra, Epididymis	Fallopian tubes, Uterus, Vagina

Structures of the Gametes (Sperm and Ovum

Sperm (Male Gamete)

• • • Structure: Small, motile, and streamlined for movement.
    • Parts:
      • Head – Contains the nucleus (haploid genetic material) and the acrosome (enzymes to penetrate the egg).
      • Midpiece – Contains mitochondria that provide energy for movement.
      • Tail (Flagellum) – Propels the sperm toward the egg.
        
        
        

    Ovum (Female Gamete)

    Structure: Large, round, and non-motile.

    Parts: 

    v Nucleus – Contains haploid genetic material.

    v Cytoplasm – Contains nutrients to support early embryo development.

    v Zona Pellucida – A protective glycoprotein layer that prevents polyspermy (entry of multiple sperm).

    v Corona Radiata – A layer of cells that nourishes and protects the egg.

    • • 

         Fertilization

        l Occurs when a sperm cell fuses with an egg in the fallopian tube.

        l The sperm penetrates the egg using enzymes from its acrosome.

        l Once a single sperm enters, the egg’s membrane changes to prevent multiple sperm from entering (polyspermy prevention).

        l The genetic material from sperm and egg combine to form a zygote (diploid cell, 2n).

        B. Embryonic Development

        1. Cleavage – Rapid mitotic cell divisions of the zygote forming a ball of cells (morula).

        2. Blastocyst Formation – A hollow ball of cells that implants into the uterus lining.

        3. Gastrulation – Formation of three germ layers:

        Organogenesis – Formation of major organs and systems.

        C. Pregnancy and Birth

        4. Gestation Period – Varies among mammals; in humans, it lasts about 9 months.

        5. Placenta Formation – A temporary organ that facilitates nutrient, gas, and waste exchange between mother and fetus.

        6. Birth Process (Parturition) 

        Stage 1: Dilation – The cervix dilates due to contractions.

        Stage 2: Expulsion – The baby is pushed out through the birth canal.

        Stage 3: Placental Delivery – The placenta is expelled after the baby is born.