Human Development and Birth Sexual Reproduction Human Development and Birth

The Male Reproductive System

Male Gonads =Testes It produces (male sex hormone) Testosterone sperm formation happens in the seminiferous tubules of the testes The is the sac that contains the testes. Scrotum Sperm are stored in the epididymis on top of the testes

This tube connects with the & leads out of the penis When it’s time the sperm travel through a duct/tube called the vas deferens This tube connects with the & leads out of the penis Urethra The sperm pass by glands that add fluids to form . semen The semen nourishes & protects the sperm from the acidic environment of the woman's vagina seminal vesicles: secretes a fluid high in protein. prostate gland: neutralizes urethra

= Male reproduction organ The is used by both the excretory & reproduction systems. Urethra = Male reproduction organ Penis An adaptation for internal fertilization. Gets the sperm into the female's reproductive tract

Male Reproductive System The Tubes within the Male Reproductive System

Urinary bladder Pubic bone Vas deferens Urethra Penis Seminal Vesicle Large intestine Prostate gland Rectum Scrotum Epididymis Testis

Why would the uterine lining need to be thick??? Ovaries OVARY OVIDUCT Female Gonads = Contain immature (ova) eggs Produces many hormones: estrogen – thickens lining of uterus & progesterone – maintains thick uterine lining. Why would the uterine lining need to be thick??? MENSTRUATION – A woman’s period

Oviduct = Fallopian Tubes After ovulation, the egg is transported through the (a.k.a. Fallopian tubes) heading towards the uterus Oviduct If any sperm are around, this is where the egg is fertilized. OVIDUCT

Uterus Thick walled, and muscular. OVARY Thick walled, and muscular. Where the embryo implants & develops Cervix Lower end of the uterus is The is opening for baby (birth canal) Vagina

The Female Reproductive System Fallopian tube Ovary Urinary bladder Pubic bone Urethra Vagina Uterus Cervix Rectum

The Egg Each ovary contains about 200,000 tiny egg sacs called = . Follicles Each follicle contains an immature egg When the follicle ruptures releasing the egg, it is called Ovulation Oviduct The egg is pulled into the If fertilized=Zygote, will embed into uterus

The Menstrual Cycle begins at puberty and ends at menopause usually lasts approximately 28 days can vary due to many factors. Like what? there are 4 stages to the menstrual cycle

What is this an example of??!! Follicle stage ·    FSH (follicle-stimulating hormone), produced by the pituitary tells the egg to mature ·    Estrogen is produced from the ovary to build up the uterine lining (blood vessels) in case the embryo implants & to stimulate ovulation ·      ~days 1-14 of the cycle What is this an example of??!! NEGATIVE FEEDBACK

The Menstrual Cycle

Ovulation the mature egg is released from the follicle around day 14 the high levels of luteinizing hormone stimulates the ruptured follicle to transform into the corpus luteum

Release of Egg from Follicle

Corpus luteum stage the corpus luteum secretes progesterone which maintains the uterine lining if fertilization/implantation ~days 14-26 of the cycle

Menstruation ·    if no zygote is implanted into the uterus, the uterine lining breaks down   ·    the lining of the uterus pass out of the body through the vagina ·      ~ days 26-28 of the cycle

Remember Meiosis?? Specialized sex cells or gametes (Sperm & Egg) Cells created have only half the number of chromosomes The nuclei of the gametes fuse during Fertilization.

Forms of Fertilization & Development Fert/dev Fertilization: fusion of haploid sperm and haploid egg

External Fertilization & External Development Fish Eggs

External Fertilization & External Development

Internal Fertilization External Development Turtle Egg Sac

External Development Turtle Eggs

External Development

External & Internal Fertilization Does not need water environment Male introduces sperm into the female body Only 1 egg needed Ex.) Sharks, lobsters, humans No “scattering” of gametes outside, fewer eggs used. Timing is key- fertilization can only occur 24 hrs after egg is released. Need a water environment Male will “fertilize after the female has laid eggs Large numbers of eggs and sperm needed Ex.) Salmon, Fish, Amphibians More offspring, Hormonally controlled behavior Eggs may eaten by other animals, may die from temperature, O2 content

Internal Fertilization & Internal Development

Fertilization and Implantation Day 0 Day 1 Implantation of blastocyst Fertilization Egg released by ovary Uterine wall Blastocyst Morula Zygote Ovary Fallopian tube Day 3 Day 2 Day 4 Day 7

The fertilized egg makes the journey through the Fallopian tube to the uterus, where it will implant.

Human Development and Birth Clip..\biomovies\humanembryonicdevelopment.mov Human Development and Birth

Fertilization in Humans after ovulation, fertilization usually occurs in the oviduct- formation of a zygote if not fertilized within ~24 hours, the egg deteriorates & can no longer be fertilized cleavage begins in the oviduct ~ 6-10 days later, the developing embryo (now a blastula) may be implanted in the lining of the uterus gastrulation & differentiation occur after the embryo has been implanted in the uterine walls

Pre- natal Development first 2 months are the most important! (cells become specialized—differentiation) leads to low birth weight (less than 5 pounds at birth), which is the leading cause of developmental disability--lots of problems possible cerebral palsy, seizure disorders, immature organs, non-developed immune system THIS CAN BE PREVENTED! CHEMICALS IN YOUR BLOOD CAN ALSO GET INTO YOUR DEVELOPING CHILD'S BLOOD

An eight-celled pre-embryo EARLY STAGES OF EMBRYONIC DEVELOPMENT (Zygote undergoing mitosis)                                                            A zygote                                                     An eight-celled pre-embryo

CHANGES IN THE ZYGOTE

The “Germ” Layers Ectoderm: Mesoderm: Endoderm: Forms the nervous system, Skin, lining of mouth, hair, nails Mesoderm: Muscles and Red Blood Cells Endoderm: Lines of the inside of Respiratory tract, digestive tract, endocrine glands

First Week to Third Week Pregnancy First Week to Third Week The ovum (egg) is in the uterus. Inside this egg sac is the tiny embryo The primary divisions of the brain are visible Fourth Week to Sixth Week The cerebrum begins to appear. The ends of the fingers & toes can be recognized. Seventh and Eighth Weeks The upper lip is completed, The eyelids are present

First Trimester: From Embryo to Fetus The embryo at six weeks

The fetus at 12 weeks Third Month.— eyelids meet and fuse, the limbs are well developed The external organs are differentiated that it is possible to distinguish the sex. The fetus at 12 weeks

Second Trimester: The Growing Fetus The hairs begin to make their appearance. There is an increase in size Umbilical cord- attaches embryo to the wall of the uterus The fetus at 14 weeks

The fetus at 20 weeks The first movements are observed Placenta- exchanges nutrients, gases, and wastes through diffusion across blood vessels The fetus at 20 weeks

Seventh Month Eyelids are open The weight 3lbs The body is covered by fine hairs The fetus at 24 weeks

Third Trimester: The Final Weeks Eighth Month The skin becomes pink The weight is between 4-6 lbs Ninth Month Fetus weighs from 6-10 lbs The fetus at 32 weeks

Birth What are the three stages of birth? 1. Dilation- mild contractions of the uterine muscles; oxytocin is released to stimulate contractions and dilation of cervix ; amniotic sac ruptures 2. Expulsion – contractions force baby through the cervix to the birth canal; mother assists by contracting and “pushing” 3. Placental stage- after birth of baby, placenta seperates from the uterine wall, umbilical cord is clamped Birth

Birth- the process by which a fetus is pushed out of the uterus and the mothers body Labor- the physiological and physical changes a female goes through to give birth

It’s Twins!! If more than one egg is produced, you can have more than one embryo FRATERNAL TWINS IDENTICAL TWINS *2 eggs and 2 sperm *2 eggs get fertilized *1 egg and 1 sperm *1 egg gets fertilized *zygote splits during cleavage