Endocrinology Quiz: Hormones and Functions

Male Reproductive System

• Organs include the testes within the scrotum and the penis
• Ducts include the epididymis, ductus deferens, ejaculatory duct, and urethra
• Accessory glands include seminal glands, prostate gland, and bulbourethral glands

Male Reproductive Strategy

• Males produce millions of sperm cells to deliver to the female reproductive system.
• Sperm cells require less energy to produce than egg cells, so males can produce many.

Spermatogenesis

• Immature sperm cells are created in the testes, starting at puberty.
• Spermatogenesis is a specialized cell division process called meiosis.
• About 100 million sperm are created daily.
• Sperm travel from the seminiferous tubules to the epididymis for maturation.

Testis to Epididymis

• Immature sperm are made (spermatogenesis) in the testes.
• Sperm complete maturation in the epididymis.
• The seminiferous tubules are where sperm are made.

Mature Sperm Cell

• The tail propels the sperm.
• The midpiece contains mitochondria for energy to reach the egg.
• The head contains the father's chromosomes.
• The acrosome contains enzymes that assist with fertilization.

Male Accessory Glands

• Seminal glands are located on the posterior surface of the urinary bladder.
• Seminal glands contribute majority of seminal fluid during ejaculation and contain nutrients for sperm.
• Prostate gland is doughnut-shaped and encircles the origin of the urethra.
• Prostate gland fluid activates sperm and counteracts acidity of the female reproductive tract.
• Bulbourethral glands are pea-sized, located below the prostate.
• Bulbourethral glands ducts empty into the urethra.
• Fluids from these glands, plus the sperm, make up semen.

Penis

• Functionally serves a dual purpose: reproduction (delivers sperm to the female reproductive tract and for urine elimination).
• Contains erectile tissue (corpus spongiosum and corpora cavernosa).
• The urethra passes through the erectile tissue and is the duct through which semen and urine travel.
• Erectile tissue fills with blood during arousal leading to an erection.

Pathway for Sperm

• During ejaculation, semen is propelled through ducts by smooth muscle contractions.
• Sperm travels from the epididymis through the duct system (ejaculatory duct, ductus (vas) deferens, urethra).
• Fluids are also ejected into the duct system from seminal glands, and fluids from the prostate gland.

Hypothalamus-Pituitary-Gonadal (HPG) Axis

• Gonadotropin releasing hormone (GnRH) from the hypothalamus stimulates the anterior pituitary to release Luteinizing hormone (LH) and Follicle-Stimulating hormone (FSH).
• LH and FSH affect the activity of gamete and sex hormone production in the gonads (testes).

Testosterone Level Regulation

• Testosterone stimulates spermatogenesis.
• Elevated testosterone levels inhibit LH and GnRH.
• This is an example of a negative feedback homeostatic mechanism.

Sperm Production

• FSH and testosterone together stimulate spermatogenesis in the testes.
• Elevated sperm count triggers the release of inhibin from secretory cells.
• Inhibin inhibits GnRH and FSH release from the hypothalamus and anterior pituitary, respectively.

Recall: Testosterone

• A steroid hormone that increases at puberty.
• Stimulates spermatogenesis in the testes, causes reproductive duct, glands and penis growth..
• Causes development of secondary sex characteristics.
• Includes pubic, axillary, and facial hair, increased hair on chest, enlarged larynx (voice drop).
• Increased bone size and density, and skeletal muscle mass.
• Increases metabolic rate and is responsible for sex drive.
• Also found in females at a lower level.

Female Reproductive Strategy

• The reproductive strategy of females is to produce a few nutrient rich eggs in their lifetime. (approx 500).
• Egg cells are the largest.
• Sperm cells are the smallest.

Functions of the Female Reproductive System

• Produce eggs.
• Produce sex hormones (estrogen and progesterone).
• Nurture the developing zygote into an embryo, then fetus in the uterus.
• Nurture the newborn postpartum.

Female Reproductive Tract

• Uterine tubes deliver a mature egg to the uterus.
• Uterus provides a place for fertilization and development of a developing fetus.
• Vagina serves as a birth canal and a site for sperm deposition.

Ovaries

• Paired, located on either side of the uterus.
• Produce and release eggs.
• Produce and release female sex hormones (estrogen and progesterone).

Oviducts and Uterus

• The oviduct is the passageway for an ovulated egg to travel to the uterus, also the common site of fertilization.
• Uterus is where implantation of an embryo occurs.
• Smooth muscle in the uterine wall contracts (with oxytocin) during labor and delivery.
• The endometrium is the inner blood-rich layer for implantation.

Vagina

• A thin-walled tube connecting the uterus to the outside of the body.
• Located between the bladder and rectum.
• Functions include a pathway for menstrual flow and childbirth, as well as a site for sperm deposition.

External Genitalia (Vulva)

• The opening of the vagina may be covered by a partial membrane called the hymen.
• The clitoris is erectile tissue sensitive to touch, homologous to the penis in males.
• Labia minora and labia majora are the skin folds that surround the vaginal opening.

Monthly Cycle

• Female monthly cycles are typically 28 days.
• Ovulation typically occurs around day 14.
• Menstruation is the shedding of the lining of the uterus if fertilization has not occurred.
• Extremely variable between women concerning time, amount of blood loss, cramps, and clots.

Recall: Estrogen

• A steroid hormone analogous to testosterone in males.
• Increases at puberty and has several effects on the female body, including:
• Promotes embryonic female sexual development
• At puberty, estrogen causes maturation of the female reproductive tract.
• This includes the start of the menstrual cycle, growth spurt, breast development,
• Increased adipose tissue in hips and breasts, and widening of the pelvis.
• Maintains ideal blood cholesterol levels.
• Facilitates calcium uptake.

Progesterone

• Levels rise after ovulation and are maintained throughout pregnancy.
• If pregnancy does not occur, progesterone levels drop at the end of the monthly cycle.
• Enrichs and maintains the lining of the uterus (endometrium), and acts as a major component of the placenta.
• Increases thickness of cervical mucus.
• Inhibits egg development and ovulation by blocking the release of GnRH, LH and FSH.
• Inhibits uterine muscle contractions.

Premenstrual Syndrome (PMS)

• Emotional and physical changes during the 1-2 weeks before a period that typically resolve after the period starts.
• Possible emotional experiences include being more sensitive to things, mood swings, less motivation, feeling hopeless, anxious and overwhelmed, irritability and difficulty concentrating.
• Possible physical symptoms might include breast tenderness or swelling, achy muscles and joints, headaches, feeling bloated and difficulty sleeping.
• Symptoms differ between women, but they are usually similar from one woman to another though some women may be more sensitive to these fluctuations than others.

Premenstrual Dysphoric Disorder (PMDD)

• Symptoms of PMDD are severe enough that they prevent one from performing daily activities at school, work, or home.
• Recent studies suggest that women with PMDD likely have increased sensitivity to progesterone which increases activity in the limbic system of their brains.

What to do if you have PMS or PMDD

• Track your cycle to predict symptoms.
• Focus on emotional well-being through activities such as nature time, meditation, or yoga.

Oral Contraceptives

• Birth control pills supplement the body with progesterone, sometimes in combination with estrogen.
• The hormones present in pills (1-21 days) inhibit egg development and ovulation by blocking GnRH release.
• 22-28 days (placebo pills), help to cause menstruation.

Test your knowledge on the roles of inhibin and testosterone in hormone regulation and reproductive functions. This quiz covers important effects on GnRH and FSH release, as well as functions of testosterone. Dive into the intricate world of endocrinology!