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 System Estrogen and Testosterone are steroid hormones Both act on cells and tissues to produce physical characteristics of males and females

The Reproductive System Female 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 System Puberty – 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 System Sperm Development Seminiferous Tubules – tiny tubes inside testes where sperm develop Epididymis – area where sperm mature and are stored Vas Deferens – some sperm are moved into this tube

The Male Reproductive System Vas 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 females The 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 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 Cycle includes: Luteal Phase – immediately after ovulation Progesterone (a hormone) is released Stimulates the growth and development of blood supply

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 & Development Gametes – sperm and egg Fertilization – 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

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

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

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

Second Trimester (month 4-6) 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

Third Trimester (month 7-9) 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 develop Premature Babies – born before 8th month

Childbirth Oxytocin – hormone released by posterior pituitary gland; affects a group of muscles in the uterine wall Labor – 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: Chorion Placenta fetus 2nd trimester 3rd trimester Oxytocin Umbilical Chord Gametes (sperm/egg) Fallopian Tube Zygote/embryo Granules Mitosis Blastocyst Implantation Gastrulation (ectoderm, mesoderm, endoderm Neurulation Mesodermal tissue Notochord Spinal chord Brain Amnion/amniotic fluid