Gamete Formation

• Male

– Haploid gametes produced by meiosis are called spermatozoa

– Spermatogenesis begins at puberty and continues throughout one’s life

– Under hormone and environmental control

• Female

– Haploid gamete produced by meiosis is called an oocyte

– Cell divisions at the end of meiosis one and two are uneven so one cell gets most of the cytoplasm (the EGG) and the other three are called polar bodies (don’t participate in reproduction)

– IMPORTANT!• Female gametes are stuck in Prophase 1 until

puberty• Complete Meiosis 1 every month and the

secondary is released from ovary• Female gametes only reach and complete

meiosis 2 if they are fertilized

Mitosis vs. MeiosisMitosis– Results in the production of two genetically

identical DIPLOID cells– Daughter cells have sets of chromosomes

identical to each other and to parent cell– MITOSIS allows body to grow and replace

other cells– Asexual reproduction

Meiosis– Results in four genetically different HAPLOID

cells– MEIOSIS is how sexually reproducing

organisms make gametes

Embryology and Reproduction

Embryology

• Zygote– When male gamete fertilizes female gamete– Gametes fuse, making one new cell with

chromosomes from both parents– Zygote will divide into 2 new cells…each of those

into 4 and so on…– Cleavage division of embryonic cells to form two

new cells• Genetic material is copied before each cleavage

• Blastula– Hollow ball of cells

• Gastrula – When blastula implants itself on the uterine wall (to

get nourishment from mother)– Ball of cells composed of three layers “GERM

LAYERS” (undifferentiated)– Differentiation begins…

Zygote formation

Cleavage

4 cells

Morula

Blastocyst

Stages of Embryo Development1. Male gamete fertilizes female gamete2. Formation of Zygote– Zygote cells divide into…

3. Morula– Dense ball of 64 cells

4. Blastula/blastocyst– Hollow ball made up of a single layer of

cells– Implants onto the female organ called the

UTERUS

5. Gastrula– When 3 germ layers begin to differentiate

6. Fetus1. Organogenesis has occurred

Stages of Early Development1. Implantation

– When blastocyst secretes enzymes that digest the soft tissue of the ENDOMETRIUM, the lining of the uterus and implants on the uterine wall of the mother

– After implantation, DIFFERENTIATION can occur

2. Gastrulation– When the 3 germ layers form in the

embryo– Cells in blastocyst begin to

differentiate into 3 germ layers– Blastocyst now becomes a GASTRULA

3. Neuralation • Development of the nervous

system– Mesoderm tissue develops into the

NOTOCHORD which becomes SPINAL CORD with an enlarged end that eventually becomes the BRAIN

Embryo becomes a Fetus when…• When the structures of the

developing embryo have become distinguished

• Cells have differentiated into their permanent role in that organism

• This occurs during first trimester

Gastrula • Germ layers– Differentiation the

process by which a cell develops in different ways to perform different functions…begins with the forming of three germ layers

– Ectoderm• Outer layer• Forms skin, nerves and sense

organs

– Mesoderm• Middle layer• Forms bones, muscles and

connective tissue

– Endoderm• Inner layer• Forms digestive system and

lungs

Stages of Fetal Development1st trimester 0-3 months 2nd trimester 3-6 months 3rd Trimester 6-9 months

•Implantation on uterus wall•Gastrula forms•Organogenesis occurs•Body structures become distinguishable•Embryo is now called a FETUS

•Fetus is very active (feel movement)•Fetus increases in size•Heart beat can be heard•Fully developed eyes•Lungs begin to develop

•Lungs become fully developed•Central Nervous System Develops•Brain is actively growing the most•Fetus can begin to regulate body temperature (maintain homeostasis)•Layer of hair forms on head

Important Glands that Regulate The Release of Gametes

Male • Pituitary gland

and the testes regulate the release of hormones that stimulate the production of TESTOSTERONE

Female• Pituitary

gland and the ovary regulate the release of hormones that stimulates the production of ESTROGEN

The hormones that regulate both male and female gamete formation are:

1. LH- luteinizing hormone 2. FSH- follicle stimulating hormone

Reproduction Part 2

Things to know about the Reproductive Systems

Male• Function and

location of:– Testes– Seminal

Vesicle– Prostate gland– Vas Deferenes– Urethra– Epididymis

Female• Function and

location of:–Ovaries–Oviduct–Uterus–Cervix

• Testes• Organs that produce and store millions of male

gametes(spermatocytes) after puberty, when testosterone is produced

• Contain hundreds of tiny coiled tubes called SEMINIFEROUS TUBULES ( production of gametes)

• Epididymis• Structure that sits on top of testes• Spermatocytes produced in SEMINIFEROUS TUBULES

leave and travel here to MATURE• Vas Deferenes

• Mature spermatocytes leave EPIDIDYMIS and move into these tubes that extend upward from the scrotum to the abdomen

• These tubes eventually merge with the URETHRA• Seminal Vesicle and Prostate Glands

• GLANDS that line the reproductive tract• Glands that produce liquid (seminal fluid) that carries

male gametes out of the body• seminal fluid-nutrient rich fluid that nourishes and

protects male gametes from the acidity of the female reproductive tract

• Seminal Vesicles are attached to the Vas Deferns, the tube that the spermatocytes travel through

• Urethra• Tube that carries MATURE gametes out of the body

through the penis (always responsible for carrying urine out of the body)

Seminal Fluid + Sperm = Semen

Path of Male Gametes

• Testes contain seminiferous tubules (gametes produced)

• Epididymis (gametes Mature and are STORED)

• Vas deferens (gametes travel)

• Urethra (gametes travel)

• Out of the body

Female Reproductive System• Ovaries (produce, store and release EGGS)

• Female gonads that produce ova (oocytes)and estrogen

• Contains about 400,000 primary oocytes, contained in protective cluster of cells called FOLLICLES

• Only 400 eggs will be released• Every 28 days one follicle moves to edge of

ovary, follicle breaks open and egg is released into oviduct (FT)

• Oviduct/Fallopian Tube (FT)• Where fertilization occurs if male gamete is here• Cilia move egg along• Development of embryo (morula and blastula

occur)• Dumps egg into cavity called UTERUS

• Uterus• Site of attachment of the fertilized egg

(implantation)• Provided nourishment to embryo• End of uterus is the opening called the CERVIX

• Cervix• Opens up to canal (VAGINA) that carries

unfertilized oocyte OR completely developed FETUS out of the body

The End