human development and birth. the male reproductive system

Human Development and Birth

The Male Reproductive

System

Male Gonads =Testes

•It produces (male sex hormone)

•The is the sac that contains the testes.

•sperm formation happens in the seminiferous tubules of the testes

•Sperm are stored in the epididymis on top of the testes

Testosterone

Scrotum

• The semen nourishes & protects the sperm from the acidic environment of the woman's vagina

•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

• The sperm pass by glands that add fluids to form .

a) seminal vesicles: secretes a fluid high in protein.

b) prostate gland: neutralizes urethra

Urethra

semen

= Male reproduction organ•An adaptation for internal fertilization. Gets the sperm into the female's reproductive tract

•The is used by both the excretory & reproduction systems.

Urethra

Penis

The Tubes within the Male Reproductive System

Large intestine

Rectum

Seminal Vesicle

Prostate gland

Epididymis Testis

Scrotum

Penis

Urethra

Vas deferens

Pubic bone

Urinary bladder

Why would the uterine lining need to be thick???

Female Gonads =

• Produces many hormones: estrogen – thickens lining of uterus & progesterone – maintains thick uterine lining.

OVARY

OVIDUCT

•Contain immature (ova)

MENSTRUATION – A woman’s period

Ovaries

eggs

•After ovulation, the egg is transported through the

(a.k.a. Fallopian tubes) heading towards the uterus

Oviduct = Fallopian Tubes

• If any sperm are around, this is where the egg is fertilized.

OVIDUCT

Oviduct

•Thick walled, and muscular.

Uterus

•Lower end of the uterus is

•The is opening for baby (birth canal)

UTERUSOVARY

•Where the embryo implants & developsCervix

Vagina

Fallopian tube

Ovary

Urinary bladder

Pubic bone

Urethra

Vagina

Uterus

Cervix

Rectum Vagina

Fallopian tube

Ovary

The Female Reproductive System

•Each ovary contains about 200,000 tiny egg sacs called = .

The Egg

•When the follicle ruptures releasing the egg, it is called

•The egg is pulled into the

•Each follicle contains an immature

•If fertilized=Zygote, will embed into uterus

Follicles

egg

Ovulation

Oviduct

• begins at puberty and ends at menopause

The Menstrual Cycle

• usually lasts approximately 28 days

• can vary due to many factors. Like what?• there are 4 stages to the menstrual cycle

FSH (follicle-stimulating hormone), produced by the pituitary tells the egg to mature

Follicle stage

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

•the mature egg is released from the follicle around day 14

Ovulation

•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

if no zygote is implanted into the uterus, the uterine lining breaks down

Menstruation

the lining of the uterus pass out of the body through the vagina

~ days 26-28 of the cycle

•Specialized sex cells or gametes (Sperm & Egg)

•Cells created have only half the number of chromosomes

Remember Meiosis??

•The nuclei of the gametes fuse during Fertilization.

Fertilization: fusion of haploid sperm and haploid egg

Fish EggsExternal DevelopmentExternal Fertilization &

External Fertilization & External Development

Turtle Egg Sac

Internal Fertilization

External Development


Turtle Eggs

*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

*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.

Internal Fertilization & Internal Development

Day 7

Day 4

Day 3 Day 2

Fertilization and Implantation

Day 0

Day 1

Implantation of blastocyst

Fertilization

Egg released by ovary

Uterine wall

Blastocyst

MorulaZygote

Ovary

Fallopian tube

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

Human DevClip..\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

•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

•first 2 months are the most important! (cells become specialized—differentiation)

THIS CAN BE PREVENTED!

CHEMICALS IN YOUR BLOOD CAN ALSO GET INTO YOUR DEVELOPING CHILD'S

BLOOD

Pre- natal Development

EARLY STAGES OF EMBRYONIC DEVELOPMENT (Zygote undergoing mitosis)

A zygote

An eight-celled pre-

embryo

CHANGES IN THE ZYGOTE

The “Germ” Layers

Ectoderm:Forms the nervous system,Skin, lining of mouth, hair, nails

Mesoderm:Muscles and Red Blood Cells

Endoderm:Lines of the inside ofRespiratory tract, digestive tract, endocrine glands

First Week to Third Week The ovum (egg) is in the uterus. Inside this egg sac is the tiny embryoThe 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

Pregnancy

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.


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 first movements are observed

•Placenta- exchanges nutrients, gases, and wastes through diffusion across blood vessels


Seventh Month

•Eyelids are open

•The weight 3lbs

•The body is covered by fine hairs


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

*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- 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

If more than one egg is produced, you can have more than one embryo

*1 egg and 1 sperm

*1 egg gets fertilized

*zygote splits during cleavage

It’s Twins!!

FRATERNAL TWINS

*2 eggs and 2 sperm

*2 eggs get fertilized

IDENTICAL TWINS

human development and birth. the male reproductive system

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