The Reproductive System. At first male and female human embryos are nearly identical in appearance.
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Transcript of The Reproductive System. At first male and female human embryos are nearly identical in appearance.
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