Reproductive System Overview and Functions

Reproductive System Overview

• The reproductive system has four key functions: producing gametes (sex cells), fertilization, development and nourishment of a new individual, and production of reproductive hormones.
• Learning objectives include describing male and female reproductive system structures and functions; stating the functions of male and female reproductive hormones; explaining the process of ovulation and the menstrual cycle.

Major Reproductive Organs

• Diagrams show the male and female reproductive organs
• Note the locations of the testes, epididymis, ductus deferens, seminal vesicles, prostate gland, bulbourethral glands, penis, mammary glands, uterine tubes, ovaries, uterus, and vagina.

Formation of Gametes

• Gametes, or sex cells, include sperm in males and oocytes (eggs) in females.
• Meiosis is a specialized cell division process that leads to the formation of the sex cells (gametes).
• Each sperm cell and oocyte contains 23 chromosomes.

From Fertilization to Fetus

• Fertilization is the union of sperm and oocyte.
• A zygote is produced after fertilization.
• The zygote develops into an embryo within 3 to 14 days of fertilization.
• Embryonic development continues from 14 to 56 days after fertilization.
• From 56 days onward, the developing organism is termed a fetus

Male Reproductive System

• The male reproductive system includes the scrotum, testes, epididymis, ductus deferens, urethra, and penis.

Male Reproductive Structures

• Diagrams show the male reproductive structures within the body.
• Key structures labeled in the diagram include the urinary bladder, urethra, penis, glans penis, prepuce, ductus deferens, epididymis, testes, scrotum, ureter, seminal vesicle, ejaculatory duct, rectum, prostate gland, and bulbourethral gland.

Male Reproductive Organs

• The scrotum houses the testes.
• Sperm development occurs at a lower temperature than the body's core temperature.
• Testes are the primary male reproductive organs that produce sperm and are located within the scrotum.
• Testes contain seminiferous tubules where sperm is produced.
• Interstitial cells within the testes, secrete testosterone.
• Germ cells are cells from which sperm arises
• Sustentacular cells provide support to sperm production

Epididymis

• The epididymis is a thread-like structure next to the testes.
• It is where sperm from seminiferous tubules mature and develop the ability to swim.

Ductus Deferens

• The ductus deferens (vas deferens) extends from the epididymis and joins the seminal vesicle.
• It is cut during a vasectomy.

Urethra

• The urethra extends from the urinary bladder to the end of the penis.
• It is a passageway for both urine and male reproductive fluids.

Penis

• The penis transfers sperm from the male to the female and excretes urine.

Male Reproductive System Glands

• Seminal vesicles are next to the ductus deferens, and help form the ejaculatory ducts.
• The prostate gland surrounds the urethra. (Size of a walnut)
• The bulbourethral glands secrete mucus near the base of the urethra.

Semen

• Semen is mixed sperm and secretions from glands.
• Semen provides a transportation medium and nutrients for sperm.
• Semen protects and activates sperm.
• Sixty percent of seminal fluid is from the seminal vesicles.
• Thirty percent from the prostate gland.
• Five percent is from the bulbourethral gland.

Seminal Vesicles

• Seminal vesicles provide fructose in seminal fluid.
• Seminal vesicles contain prostaglandins that decrease mucus thickness around the cervix.
• Prostaglandins help sperm move through the female reproductive tract.

Prostate Gland

• The prostate gland contains enzymes that liquefy semen after it enters the female.
• Enzymes neutralize the acidity of the female vagina.

Bulbourethral Glands

• The bulbourethral glands neutralize the acidity of the male urethra and female vagina.

Testicular Secretions

• Testicular secretions include sperm and a small amount of fluid.
• Two to five milliliters of semen are ejaculated each time.
• One milliliter of semen contains 100 million sperm.
• Sperm can live up to 72 hours once inside the female.

Path of Sperm

• Sperm develop in the seminiferous tubules of the testes.
• Sperm mature in the epididymis.
• Sperm travels through the ductus deferens.
• Sperm receives secretions from the seminal vesicles, prostate gland, and bulbourethral glands.
• Then through the urethra.

Sperm Cell Structure

• The sperm head contains a nucleus and DNA.
• The midpiece contains mitochondria.
• The tail is a flagellum for movement.

Male Sex Hormones

• Gonadotropin-releasing hormone (GnRH) stimulates LH and FSH secretion.

• Luteinizing hormone (LH) stimulates testosterone secretion.

• Follicle-stimulating hormone (FSH) prompts spermatogenesis.

• Testosterone helps develop and maintain the reproductive organs.

• Inhibin is secreted by Sertoli cells, slowing spermatogenesis when sperm count is too high.

Male Puberty

• Male puberty is the sequence of events where boys begin producing male hormones and sperm cells.
• It begins around 12-14 years and ends roughly at 18.
• Testosterone plays a major role.
• Boys develop secondary sexual characteristics such as skin changes, fat distribution, hair growth, and skeletal muscle growth.

Female Reproductive System

• The female reproductive system includes the ovaries, uterine tubes, uterus, and vagina.

Female Pelvis

• This diagram shows the internal female reproductive organs.
• Many labels are provided, including the uterine tubes, ovaries, uterus, urinary bladder, pubic symphysis, mons pubis, urethra, clitoris, urethral orifice, vaginal orifice, labia minora, and labia majora.

Ovaries

• Ovaries are the primary female reproductive organs located on either side of the uterus.
• Ovaries produce oocytes and sex hormones.

Structure of Ovary and Ovarian Follicles

• Ovarian follicles contain oocytes.
• Diagrams show various stages of ovarian follicle development.

Uterine (Fallopian) Tubes

• Uterine (Fallopian) tubes are parts of the uterus that extend toward the ovaries.
• They receive oocytes.
• Fimbriae are fringe-like structures that help sweep oocytes into uterine tubes for potential fertilization.
• Tubal ligation is a sterilization procedure for females.

Uterus

• The pear-shaped uterus is located in the pelvic cavity.
• It receives, retains, and nourishes the fertilized oocyte (zygote) to become a fetus.
• The uterus develops the embryo and fetus in its body.
• The cervix is the narrow region that leads to the vagina.

Uterus wall layers

• Perimetrium: outermost layer
• Myometrium: middle layer - composed of smooth muscle
• Endometrium: innermost layer that is affected by hormone changes during the menstrual cycle.

Vagina

• The vagina extends from the uterus to the exterior of the body.
• It is an organ for female copulation that receives the penis during intercourse.
• The vagina also allows menstrual flow.
• The vagina is involved in childbirth.

External Female Genitalia

• Vulva: external female sex organs that include the mons pubis, labia majora, labia minora, clitoris, and vestibule.
• Vestibule: space that holds the vagina and urethra.
• Labia minora: thin, inner folds of skin.
• Clitoris: equivalent to the male penis (small erectile tissue).
• Prepuce: where the labia unite over the clitoris.
• Labia majora: larger, outer folds of skin, similar to the male scrotum.

Ovulation, Menstrual Cycle & Menopause

• Ovulation is the release of an oocyte from the ovary.
• It is triggered by luteinizing hormone (LH).
• The corpus luteum is the mature follicle produced after ovulation.
• It degenerates if the egg is not fertilized.

Oogenesis and Fertilization

• Females are born with all their oogonia.
• Unlike males, who only start producing sperm at puberty, females have their full complement of eggs at birth.
• At puberty, about 300,000 to 400,000 primary oocytes remain.
• Secondary oocyte is swept into a uterine tube by fimbriae.
• If sperm is present, the secondary oocyte could be fertilized, and then the zygote implants in the uterus.

Female Puberty

• Female puberty begins between 11 and 13 and is completed by 16.
• Menarche is the first menstrual bleeding during puberty.
• The vagina, uterus, uterine tubes, and external genitalia enlarge, and fat is deposited in the breasts and hips.
• Estrogen and progesterone are secreted by the ovaries.

Mammary Glands

• The mammary glands produce milk.
• Female breasts enlarge during puberty.
• Lobes, ducts, and lobules make up the structure of the glands.
• The lobules are altered during lactation.

Female Sex Hormones

• Gonadotropin-releasing hormone (GnRH) stimulates secretion of LH and FSH.
• Luteinizing hormone (LH) causes ovulation.
• Follicle-stimulating hormone (FSH) prompts follicles in the ovaries to begin the process of oocyte development.
• Estrogen stimulates endometrial cell proliferation, mammary gland development, and controls LH & FSH secretion.
• Progesterone maintains pregnancy, develops mammary glands, and controls estrogen, FSH, and LH secretion.

Menstrual Cycle

• A series of changes occur in sexually mature, non-pregnant females.
• Menses is the time period when the endometrium is shed.
• The average menstrual cycle is 28 days.
• The cycle results from cyclical changes in the endometrium.

Stages of Menstrual Cycle

• Days 1-5 (Menses): endometrium sheds, estrogen and progesterone are low.
• Days 6-13 (Proliferative): endometrium rebuilds, estrogen levels increase, and progesterone remains low.
• Day 14 (Ovulation): oocyte is released due to LH, estrogen is high, and progesterone is increasing.
• Days 15-28 (Secretory): endometrium prepares for implantation, estrogen levels decrease, and progesterone levels are high.

Menopause

• Menopause is when the ovaries secrete less hormones and the number of follicles within the ovaries is lower.
• The menstrual cycle and ovulation are less regular.
• Symptoms such as fatigue and irritability may occur.
• Estrogen replacement therapy may be used to decrease side effects.

Explore the essential functions of the reproductive system, focusing on both male and female structures and their respective roles. Understand the processes of gamete formation, ovulation, and the menstrual cycle through detailed diagrams and explanations.