The Reproductive System

The Reproductive System• At first male and female human embryos are

nearly identical in appearance

The Reproductive System

• During the 7th week male pattern development is triggered by the production of testosterone in the gonads of the embryo

• Female development is triggered by the production of estrogen in the gonads

The Reproductive SystemEstrogen and Testosterone are steroid hormones• Both act on cells and tissues to produce physical

characteristics of males and females

The Reproductive SystemFemale Characteristics Produced by Sex

Hormones:• Breast Development• Widening Hips

Male Characteristics Produced by Sex Hormones:

• Facial Hair• Increase muscle development• Deepening of the voice

The Reproductive SystemPuberty – a period of rapid growth and sexual maturation during which the reproduction system becomes fully functional• Occurs between the ages 9 and 15• One year earlier for females

• Begins in the brain• Hypothalamus signals the pituitary to produce two

hormones that affect the gonads• Follicle-stimulating hormone (FSH)• Luteinizing Hormone (LH)

Male Reproductive System

Release of LH stimulates production of more

testosterone

Testosterone together with FSH stimulate

development of sperm

The Male Reproductive System• When puberty is complete, the reproductive

system is fully functional meaning that the male can produce and release active sperm

• Testes – primary male reproductive organ• Scrotum – external sac that

holds the testes

The Male Reproductive SystemSperm Development

Seminiferous Tubules – tiny tubes inside testes where sperm developEpididymis – area where sperm mature and are storedVas Deferens – some sperm are moved into this tube

The Male Reproductive SystemVas Deferens• Extends upward from the scrotum into the abdominal cavity• The Vas Deferens merges with the Urethra• This tube leads to the outside of the body

Glands lining the reproductive tract• Seminal Vesicles• The Prostate Gland• The Bulbourethral Gland• Produce a nutrient rich fluid called Seminal Fluid

Semen – the combination of sperm and seminal fluid

The Male Reproductive System

Sperm Structure

Sperm is a CELL• Nucleus• Mitochondria• Flagellum (tail)

Male Reproductive Organs

The Female Reproductive System

Ovaries – primary reproductive organ of femalesThe main function of the female reproductive

system is to produce egg cells• Ova (ovum) singular – egg cell

Female Reproductive System

Puberty begins when hypothalamus signals the pituitary gland to release FSH and LH

FSH stimulates increased production of estrogen

The Female Reproductive System

• At puberty each ovary contains as many as 400,000 primary follicles• Cluster of cells surrounding a single egg• Follicles help egg mature

• Females release only about 400 mature eggs in a lifetime

Female Reproductive System

The Menstrual Cycle• A regular sequence of events involving the ovaries,

the lining of the uterus, and the endocrine system• One ovary usually produces and releases one mature

ovum (egg) every 28 days or so……• Regulated by hormones made by the hypothalamus,

pituitary, and ovaries• During the Menstrual Cycle• An egg develops within a follicle• Then its released from an ovary• Uterus is prepared to receive a fertilized egg

The Menstrual Cycle• If the egg is not fertilized it is discharged• Along with the uterus lining

• If the egg is fertilized, embryonic development begins and menstrual cycle stops

The Menstrual Cycle

The menstrual Cycle includes:Follicular Phase – hormones cause follicles to mature• Usually more than one but can be more• Ovulation – the release of an egg from the ovary into one of the Fallopian Tubes.• follicle grows more estrogen is released

The Menstrual CycleThe menstrual Cycle includes:

Luteal Phase – immediately after ovulation • Progesterone (a hormone) is released• Stimulates the growth and development of

blood supply

The Menstrual Cycle

The menstrual Cycle includes:Menstruation – At the start of the new follicular phase, low estrogen levels cause lining of uterus to detach• Uterus lining, blood, and unfertilized egg are

discharges through the vagina• A new cycle begins on the first day of menstruation

Pregnancy

• Menstrual cycle ceases if pregnant• First two days of the Luteal Phase is the

greatest time where fertilizing an egg is greatest.

Day 2- Reproductive Cycle

Bellringer:R.A.F.T assignment

(yes this will be graded)

Imagine you are an egg cell. Describe your story of how you formed into a human fetus (a baby

inside a mothers womb) from meeting a sperm cell all the way till birth. Be as specific as you

can! (aka, step-by-step story line

Pregnancy• If sperm fertilizes an egg; the egg completes meiosis

and immediately undergoes mitosis• After several divisions, a ball of cells form and

implant itself in the lining of the uterus.• Uterus and embryo release hormones that keep

the corpus luteum functioning for several weeks• This helps nourish and protect the developing

embryo

Fertilization & DevelopmentGametes – sperm and eggFertilization – the fusion of a sperm and egg cell

Fertilization• Hundreds of millions of sperm are released

during ejaculation• If egg is in one of the Fallopian Tubes the

chances of fertilization are high

Fertilization• Egg is surrounded by a protective layer that

has binding sites• Sperm releases enzymes that break down eggs

protective layer

Fertilization• Once the 2 haploid (haploid =1/2 #

chromosomes) sperm and egg come together a nucleus is formed

Zygote – the fertilized egg• AKA - embryo

Fertilization• When sperm enters the egg; the egg releases

granules to the outside of the cell• This forms a barrier that prevents other sperm

from entering the egg.

Multiple Embryos

• If two eggs are released during the same menstrual cycle and each is fertilized• Result Fraternal Twins

• If a single zygote splits apart and produces two genetically identical embryos • Result Identical Twins

ImplantationBlastocyst – name of embryo after going through the process of mitosis• A hollow ball of cells are formed

ImplantationImplantation – 6 – 7 days after fertilization, Blastocyst attaches to the wall of the uterus• At this point blastocyst begin to specialize • This process is called Differentiation

Gastrulation• The formation of three cell layers called:• Ectoderm• Mesoderm• Endoderm

Production of key tissue layers and structures of the body

Neurulation• The first step in the development of the nervous

system• Shortly after gastrulation, a block of mesodermal

tissue begins to differentiate into the notochord• Ectoderm near the notochord thickens and

forms the neural plate• The raised edges of the neural plate form the

neural folds and the neural crest.• The neural folds move together and form the

neural tube which form the spinal cord and brain• Neural crest cells migrate and become nerve cells,

skin pigment cells, and other structures

Neurulation

Neurulation

Spina Bifida – Birth disorder in which neural tube does not close completely

• Some studies show that the vitamin supplement folic acid can prevent this

The Placenta• Specialized membranes that protect and

nourish the embryo• The embryo is surrounded by the Amnion• A sac filled with Amniotic Fluid• Cushions and protect the embryo

The PlacentaChorion – (another sac) makes direct contact with the tissues of the uterusChorionic Villi – finger-like projections that form during the 3rd week on the outer surface of the chorion and extend into the uterine lining

The PlacentaPlacenta – a vital organ formed by chorionic villi and uterine lining• This is the connection between the mother

and embryo• This is the embryo’s organ of respiration,

nourishment, and excretion• Blood barrier between mother and embryo diffuse

across the membrane• Blood does not mix

The PlacentaFetus – 8 weeks of development• Most major organs and tissues are formed• Begins to move• 8 cm and 28 grams

Later Development

Second Trimester (month 4-6)• Fetal heart becomes large enough to be heard with a

stethoscope• Bone replace cartilage• Hair grows over skin of fetus• Increases in size• Mother’s abdomen grows and she begins to feel it

Later Development

Third Trimester (month 7-9)• Organ systems mature• Fetus grows• Doubles in mass

• Lungs and other organs change and prepare for life outside• Fetus able to regulate body temperature

Later Development• 9 months is average length of time for a fetus

to developPremature Babies – born before 8th month

ChildbirthOxytocin – hormone released by posterior pituitary gland; affects a group of muscles in the uterine wallLabor – a series of rhythmic contractions caused by the muscles in the uterine wall• Contractions become more frequent and more

powerful• The opening of the cervix expands• Amniotic sac breaks – fluid rushes out of the vagina• Contractions force the baby out; usually head first

Childbirth• Once the baby is born he or she will cough or cry to

clear the lungs of fluid• Blood supply to placenta dries up• Umbilical cord is clamped and cut• Small piece stays on the baby• It dries and falls off

• Navel – scar left from umbilical cord

–AKA belly button

Childbirth• More contractions expel the placenta and

amniotic sac• Afterbirth

• Hormone prolactine (released by pituitary gland) stimulates the production of breast milk

FX Animation- from fertilization to birth

As we watch the video, we will stop and I will ask questions about what is happening. Be

prepared to use the information from today’s lecture to explain.

Take notes if you think it will help (there is an assignment following the video

Your Assignment

Revise your R.A.F.T write up using more specific details of an egg’s journey from fertilization to birth. You must include the following terms:

1. Gametes (sperm/egg)2. Fallopian Tube3. Zygote/embryo4. Granules5. Mitosis6. Blastocyst7. Implantation

8. Gastrulation (ectoderm, mesoderm, endoderm

9. Neurulation10. Mesodermal tissue11. Notochord12. Spinal chord13. Brain14. Amnion/amniotic fluid

15. Chorion16. Placenta17. fetus18. 2nd trimester19. 3rd trimester20. Oxytocin21. Umbilical Chord