Reproductive system

Asexual Reproduction

Involves a single cell replicating its DNA and dividing into two cloned, genetically identical offspring (mitosis/binary fission). Requires no mate and focuses energy on producing many offspring.

Sexual Reproduction

Involves the fusion of male and female haploid gametes to produce genetically diverse offspring. Requires a mate, produces fewer offspring, but provides a larger gene pool for environmental adaptation.

Testes

Paired male gonads held in the scrotum outside the body cavity for a cooler temperature (35°C) to successfully produce sperm.

Seminiferous Tubules

Coiled tubules inside the testes where spermatogenesis (meiosis producing sperm) occurs.

Sertoli Cells

Cells located in the seminiferous tubules that support, protect, and nourish developing sperm cells.

Interstitial Cells

Cells located between the seminiferous tubules that produce the male sex hormone testosterone.

Epididymis

A duct above the seminiferous tubules where sperm mature, grow flagella, and become motile over 4 days.

Ductus (Vas) Deferens

Muscular storage tubes that transport sperm from the epididymis to the ejaculatory duct/urethra.

Seminal Vesicles

Glands that produce a mucus-like fluid containing fructose sugar to provide energy for sperm motility.

Prostate Gland & Cowper's Glands

Glands that produce alkaline fluids to neutralize the acidic environment of the male urethra and female vagina.

Semen

The combination of sperm cells and the secretions from the seminal vesicles, prostate, and Cowper’s glands.

Urethra (Male)

Dual-purpose duct in males that carries both semen and urine outside the body through the penis.

Sperm Cell Anatomy - Head

Contains the nucleus with 23 chromosomes (22 autosomes + 1 sex chromosome).

Acrosome Cap

The covering on the sperm head containing digestive enzymes needed to break down the protective outer gel layer of the female egg.

Midpiece of Sperm

Packed with mitochondria to produce ATP energy for the tail's movement.

Flagellum (Tail)

Propels the sperm forward in a whip-lash motion.

FSH in Males

Released by the anterior pituitary; targets Sertoli cells in the seminiferous tubules to stimulate sperm production.

LH in Males

Released by the anterior pituitary; targets interstitial cells to produce testosterone.

Testosterone

Controls development and function of primary male sex organs and secondary sex characteristics.

Male Negative Feedback Loop

Sertoli cells release the hormone inhibin when FSH is high, slowing FSH release to maintain sperm production.

Andropause

Gradual decline in testosterone, fatigue, and sperm production in males around age 40.

Ovaries

Paired female gonads that produce eggs and female sex hormones (estrogen and progesterone).

Follicles

Structures inside the ovary containing single immature ova; matured from primary to secondary follicles by FSH.

Fimbriae

Finger-like projections that sweep the ovum into the fallopian tube upon ovulation.

Oviduct (Fallopian Tube)

Cilia-lined tube that sweeps the ovum toward the uterus; site of fertilization.

Ectopic Pregnancy

A dangerous condition where a fertilized egg implants in the oviduct instead of the uterus.

Uterus (Womb)

Muscular organ that houses and nourishes the developing fetus.

Endometrium

The inner lining of the uterus, where implantation occurs, and shed during menstruation if pregnancy does not happen.

Cervix

The narrow band at the base of the uterus that holds the fetus in place and dilates during birth.

Vagina

Connects the uterus to the outer environment; the site of intercourse and the birth canal.

Female Glands

Skene's glands secrete antimicrobial mucus, and Bartholin's glands secrete lubricating mucus.

Female Urethra

Strictly for passing urine and not part of the reproductive system.

Ovum (Egg Cell)

The largest cell in the female body; contains 23 chromosomes and large cytoplasm for nutrient supply.

Follicular Phase

Days 1-13 of the menstrual cycle; high FSH stimulates maturation of primary follicles into secondary follicles.

Ovulation

Day 14 of the menstrual cycle; a surge of LH triggers the release of the haploid egg.

Luteal Phase

Days 15-28 of the menstrual cycle; LH converts the ruptured follicle into corpus luteum that secretes progesterone.

Path if NOT Pregnant

Corpus luteum degenerates, causing hormone levels to fall and start menstruation.

Path if PREGNANT

Embryo implants and produces hCG, maintaining the corpus luteum and endometrium.

Menopause

End of fertility and menstrual cycles around age 50 due to a lack of follicles, leading to hormone drop.

Viral STIs (No Cure)

STIs such as HIV, Hepatitis B, Genital Herpes, and HPV with significant health impacts.

Bacterial STIs (Cureable)

Cureable STIs like Chlamydia, Gonorrhea, and Syphilis that can lead to severe complications if untreated.

Ovulation

Process where the ovum bursts from the follicle during the menstrual cycle.

Fertilization

The union of sperm and egg to create a zygote.

Cleavage

Rapid cell division of the zygote without enlargement of its cells.

Morula

A 16-cell zygote formed after the cleavage stage.

Blastocyst

An embryo that implants in the uterus, composed of the trophoblast and inner cell mass.

Implantation

The process when the blastocyst implants into the lining of the uterus.

Germ Layers

The ectoderm, endoderm, and mesoderm are collectively referred to as germ layers.

Ectoderm

The outer germ layer that forms skin, nails, hair, nervous tissue, and several organs.

Mesoderm

The middle germ layer that develops into muscle, heart, kidneys, and reproductive organs.

Endoderm

The inner germ layer that forms the tracts of organ systems, liver, and pancreas.

Blastula

A sphere of cells; during gastrulation, cells move in to produce a 3-layer embryo.

Morphogenesis

Events that form the structures of the developing fetus.

Neurulation

The formation of the neural tube, which develops into the brain and spinal cord.

Extra-embryonic membranes

Structures supporting the embryo, responsible for protection, nutrition, respiration, and excretion.

Allantois

An extra-embryonic membrane that forms the foundation of the umbilical cord.

Amnion

An extra-embryonic membrane containing amniotic fluid, protecting the embryo.

Chorion

An extra-embryonic membrane that produces hCG for the first 3 months of pregnancy.

Yolk sac

An extra-embryonic membrane developing the digestive tract and blood cells; not nutritive in humans.

hCG

A hormone that mimics LH and maintains the corpus luteum.

Placenta

After 3 months, this organ maintains the corpus luteum and transfers nutrients and waste.

Umbilical cord

Delivers nutrients and expels wastes from the fetus.

Embryonic period

The first 8 weeks of growth when organs begin to form.

Fetal period

Growth from week 9 to birth when organs begin to function.

First trimester

Weeks 1-12 of pregnancy, or months 1-3.

Month 1 (Pregnancy)

Spinal cord and nervous system form and the heart starts beating.

Month 2 (Pregnancy)

Bone growth begins, blood cells form, eyelids are shut, and nose is filled with mucus.

Month 3 (Pregnancy)

Eyes are well formed, sex is distinguishable, and nails form on fingers and toes.

Second trimester

Weeks 13-24 of pregnancy, or months 4-6.

Month 4 (Pregnancy)

Skin is pink, joints form, and the heartbeat can be heard.

Month 5 (Pregnancy)

Body covered with lanugo; mother can feel fetal movement.

Month 6 (Pregnancy)

Eyes open, eyelashes form, and skin is wrinkled, pink, and translucent.

Third trimester

Weeks 25-38 of pregnancy, or months 7-9.

Teratogen

A substance that causes harm to a fetus during pregnancy.

FASD

Disorders related to alcohol consumption during pregnancy.

Parturition

The birthing process, including labor and delivery.

Cervix

Uterine contractions are initiated by stretching this structure.

Oxytocin

A hormone that enhances uterine contractions and pushes the baby against the cervix.

Relaxin

A hormone produced by the placenta that loosens pelvic ligaments and softens the cervix.

Prolactin

A hormone that stimulates milk production in the mammary glands.

Dilation stage

The stage of parturition where contractions open the cervix and the amniotic sac breaks.

Expulsion stage

The stage where large contractions push the baby through the cervix.

Placental stage

The stage after birth where the placenta and umbilical cord are expelled.

Lactation

The process where milk is produced by prolactin and released by oxytocin.

Colostrum

A thin, protein-rich fluid secreted prior to milk, containing antibodies.

In vitro fertilization

A technique where a female egg is fertilized in a Petri dish.

Artificial insemination

A method where sperm is collected, concentrated, and inserted into a woman's vagina.

GIFT

A variation of IVF where egg and sperm are brought together in the oviduct.

Surrogate mother

A woman who carries a baby for an infertile couple.

Superovulation

The production of multiple eggs in a female.

Tubal ligation

The surgical cutting of oviducts for sterilization.

Vasectomy

The surgical cutting of the ductus deferens for sterilization.

Ultrasound

A monitoring technique providing information on the development of the baby through sound waves.

Amniocentesis

The removal of amniotic fluid to determine the karyotype of the baby.

Chorionic villi sampling

A procedure to obtain samples of the placental tissue for genetic testing.