Reproduction in Humans Notes

Structure and Function of the Male Reproductive System

  • Testes:

    • Primary sex glands (2 in number).
    • Composed of 1000 seminiferous tubules for sperm production.
    • Functions:
    • Sperm production.
    • Secretes testosterone.

  • Epididymis:

    • Coiled tube (about 6 meters).
    • Transports sperm to the vas deferens.
    • Function:
    • Temporary storage of sperm until maturation or ejaculation.

  • Vas deferens (Sperm duct):

    • 2 tubes extending from the epididymis to the urethra.
    • Function:
    • Conducts sperm to the urethra through peristalsis.

  • Urethra:

    • About 20 cm long, S-shaped, divided into 3 parts.
    • Function:
    • Conveys both sperm and urine.

  • Prostate and Seminal Vesicles:

    • Prostatic secretion forms a major portion of semen.
    • Seminal fluid from 2 seminal vesicles.
    • Functions:
    • Lubrication of sperm.
    • Provides a nutritive medium for sperm.

  • External Genitalia:

    • Penis: Contains erectile tissue; functions in copulation and urination.
    • Scrotum:
    • Maintains testes at approximately 2°C below body temperature, essential for sperm production.

Structure and Function of the Female Reproductive System

  • Ovaries:

    • 2 oval-shaped structures, approx. 3 cm long, located in the lower abdomen.
    • Functions:
    • Release of ova at ovulation.
    • Secretion of female sex hormones.

  • Oviduct (Fallopian Tube):

    • 2 long, narrow tubes with funnel-shaped ends that receive released ova.
    • Functions:
    • Conducts ova to the uterus.
    • Site of fertilization.

  • Uterus:

    • Thick, muscular, hollow organ.
    • Functions:
    • Site of implantation and development of the embryo.

  • Cervix:

    • Muscular ring at the base of the uterus, continuous with the vagina.
    • Functions:
    • Allows passage of sperm during copulation.
    • Facilitates exit of the baby or uterine secretions.

  • Vagina:

    • Tube approximately 10 cm long, opens at the vulva.
    • Functions:
    • Site of penis insertion during copulation.
    • Serves as the passageway for the baby and menstrual fluid.

Puberty

  • Marks the age of sexual maturity (12-14 for females, 14-16 for males).
  • Key changes:
    • Release of ova in females
    • Formation and secretion of sperm in males.
Secondary Sexual Characteristics

  • Females:

    • Hair in pubic area and armpits.
    • Menstruation follows development of breast size.

  • Males:

    • Hair growth in pubic region, armpits, chest, and face.
    • Deepening voice, enlargement of penis and testes.
Emotional and Physical Changes
  • Sudden emotional changes and attraction to the opposite sex.

Gametes

  • Female Gamete (Ovum):

    • Size: Large (0.1 mm in diameter).
    • Number: Released monthly after puberty.
    • Structure: Jelly coat and energy store in the cytoplasm.

  • Male Gamete (Sperm):

    • Size: Smaller (0.05 mm in length).
    • Number: Produced continually from puberty.
    • Structure: Flagellum (tail), enzymes in the acrosome, mitochondria for movement.

Female Sexual Cycles

  • Two cycles every month, each lasting 4 weeks: Ovarian cycle and Menstrual cycle.
Ovarian Cycle
  • Pituitary gland secretes FSH and LH.
  • FSH stimulates follicle development; mature follicle secretes estrogen.
  • Ovulation occurs when the Graafian follicle ruptures due to LH.
  • If pregnant, the corpus luteum secretes progesterone for 3 months.
Menstrual Cycle
  • Changes occur in the uterine lining over approximately 28 days.
  • Menstruation (shedding of the uterus lining) begins on day 1 of the cycle.
  • Regulated by hormones:
    • FSH promotes follicle growth.
    • Estrogen promotes uterine lining growth and LH release.
    • LH triggers ovulation.
    • Progesterone maintains the uterine lining.

Fertilization and Implantation

  • Fertilization:
    • Fusion of male and female gametes, forming a zygote.
    • Occurs in the outer part of the oviduct during ovulation.
Mechanism:
  • Sperm swim to the ovum; one sperm enters, dissolving the ovum's protective layers.
  • Formation of the fertilization membrane prevents additional sperm from entering.
  • Zygote formation:
    ext{Sperm} + ext{Ovum}
    ightarrow ext{Zygote} (23 ext{ Chromosomes} + 23 ext{ Chromosomes} = 46 ext{ Chromosomes})
  • Implantation:
    • The embryo sinks into the endometrium of the uterus.
    • Series of cell divisions occurs post-fertilization.

Care During Pregnancy

  • Antenatal Care:
    • Balanced diet rich in proteins, vitamins, iron, calcium, and folic acid.
    • Avoidance of alcohol and smoking to prevent low birth weight.
    • Precaution against infections; vaccination for rubella is advised.

Feeding a Baby

  • Breastfeeding Advantages:
    • Nutritionally balanced, easily digestible, and contains maternal antibodies.
    • Convenient and free.
  • Bottle Feeding Disadvantages:
    • Lacks essential nutrients, harder to digest, no antibodies.

Infertility

  • Definition: Inability to conceive offspring.
    • Causes in Males:
    • Low sperm production, motility issues, abnormal sperm forms, blockages in ducts.
    • Causes in Females:
    • Lack of ovulation, blockages in oviducts.
  • Treatment Options:
    • Fertility drugs stimulating ovulation, surgical interventions for blocked ducts, in vitro fertilization (IVF).
  • Social Aspects of Fertility Treatments:
    • Benefits of family growth vs. risks of multiple pregnancies and societal acceptance of donor usage.