Human Reproduction & DevelopmentHuman Reproduction & Development

Textbook Chapter 36Textbook Chapter 36

Review Book Topic 4Review Book Topic 4

ReproductionReproduction

Necessary process to ensure the continuation of a species

Involves the union of an egg cell and a sperm cell, development of a fetus, and the birth of an infant

Involves organs, glands and hormones of both male and female reproductive systems

Sex Cell DevelopmentSex Cell Development

Males

– Occurs in testes

– Spermatocytes mature into

sperm cells

Occurs daily from puberty to death

Females

– Occurs in the ovary

– Born with all of the immature eggs a female will use monthly from puberty to menopause

– All eggs are stored in 1st meiotic division in the ovary until it receives hormone signals to develop

Male Reproductive SystemMale Reproductive System

Reproductive organ ~ Testes

– Located outside of the body cavityin a pouch called the scrotum

– Sperm develop-ment requires a temperature lower than 37ºC

Reproductive cells ~ Sperm

– Produced in testes at the seminiferous tubules

100-200 million are produced each day

– Travel to epididymis

On top of each testes

Sperm mature and are stored there

– When released from the body, sperm travel through the vans deferens into urethra

Urethra - tube which carries semen and urine out of the body through the penis

– Sperm require a nourishing fluid to survive long enough to fertilize the egg

Semen – fluid containing sperm,

nourishment, and other fluids from male reproductive glands

Seminal vesicles (ejaculatory ducts) secrete fluids plus sugar into the semen (provides energy, proteins, and enzymes for sperm)

Prostate gland and bulbourethral glands secretes an alkaline solution to the semen to neutralize acidic conditions the sperm could encounter (ex. urethra, female system, etc.)

TRY LABELING THIS!!TRY LABELING THIS!!

Answers   1.  TESTIS 2.  EPIDIDYMIS 3.  VAS DEFERENS 4.  URETHRA 5.  BULBOURETHRAL GLAND6.  SEMINAL VESICLE / EJACULATORY DUCT7.  BLADDER 8.  PROSTATE 9.  PENIS 10. URETHRA

Male HormonesMale Hormones

Testosterone ~ hormone necessary for the production of sperm

– Made in the testes

– Influences male secondary sex characteristics

Facial & body hair

Broad shoulders

Increased muscle development

Deeper voice

Receding hairline & baldness (older)

Puberty ~ period of growth when sexual maturity is reached

– Three hormones are released from the hypothalamus that influence puberty

Gonadotropin-releasing hormone (GnRH)

Follicle-stimulating hormone (FSH)

– Promotes sperm production

Luteinizing hormone (LH)

– Promotes production and secretion of testosterone

Female Reproductive SystemFemale Reproductive System

Specialized to produce eggs cells, receive sperm and to provide the perfect environment for fertilization and development of a fetus

Reproductive organ ~ ovaries

– Two

– About the size of an almond

Reproductive cell ~ egg (ovum)

– Oocytes ~ immature eggs

– Every 28 days, oocyte development is stimulated and becomes an egg

– Surrounded by follicle cellsProtectionNourishment

– Ovulation ~ mature egg ruptures out of ovary wall

After egg is released from ovary

– Absorbed by fimbriae (finger-like hair structure)

– Travels to oviduct (fallopian tube) which connects to the uterus

– Uterus (womb) is where the baby develops before birth

Roughly the size of your fist

– Cervix is the narrow opening into the vagina from the uterus

Female HormonesFemale Hormones

Reproductive hormones ~ estrogen & progesterone

Released by ovaries

Anterior pituitary gland releases LH & FSH

During puberty, increases in estrogen cause breasts to develop, hips to widen, and fat tissue to increase

– Also will experience first menstrual cycle

Occurs each month to help prepare the female body for pregnancy

Reproductive System BrainPopReproductive System BrainPop

Menstrual CycleMenstrual Cycle

Length varies from 23 to 35 days

– Typically last 28 days

Three phases

– Flow phase

– Follicular phase

– Luteal phase

Flow phase

– Day 1 ~ menstrual flow begins

Shedding of blood, tissue fluid, mucus and epithelial cells from endometrium (uterine tissue lining)

Bleeding occurs because outer layers of endometrium tear away, rupturing blood vessels

– Day 5 ~ repair of endometrial lining

Becomes thicker as cycle continues

Follicular phase

– Estrogen level is low

– Anterior pituitary releases FSH & LH to stimulate the egg to mature in the ovary

1 week

– Egg maturation releases estrogen causing FSH & LH levels to drop (negative feedback)

– Day 12 ~ high levels

of estrogen cause

the release of a

surge of LH

Causes follicle to

rupture, releasing

egg

Ovulation occurs

Luteal phase

– After ovulation, follicle changes into the corpus luteum

Produces high amounts of progesterone

Breaks down at end of cycle, production of estrogen and progesterone stops

– Signals release of endometrium lining

– New flow phase begins

If egg is fertilized, development will occur and menstrual cycle does not begin

– Progesterone levels will remain high

– Increased flow of blood to endometrium

– Corpus luteum does not break down

– Endometrium accumulates lipidsand secretes fluid rich in nutrientsfor developing embryo

                                         

      

Menstrual Cycle BrainPopMenstrual Cycle BrainPop

FertilizationFertilizationFertilization ~ process where sperm and egg combine, forming a diploid cell

– Occurs in upper portion of the oviduct near the ovary

Sperm is deposited in the vagina through ejaculation (release of semen from the penis)

– Sperm can survive for 48 hours inside the female

– Unfertilized egg can only survive for 24 hours

– Out of the 300 million sperm deposited, only a couple hundred will reach the egg

– A single sperm cannotpenetrate the plasma membrane of the egg

One sperm will fertilizethe egg but many are needed for the processto occur

– Tip of each sperm contains lysosomes which contain enzymes used to digest the eggs membrane

When weak enough, one sperm penetrates, fertilizing the egg

Immediately the egg forms a barrier to prevent any other sperm from penetrating the fertilized egg

                                     

      

Embryo DevelopmentEmbryo DevelopmentFertilized egg is known as a zygote

– Travels through oviduct by smooth muscle contractions and by cilia lining the oviduct

– 30 hrs after fertilization, zygote undergoes first mitosis and cell division

– After 3 days, zygote leaves oviduct and enters uterus

Now referred to as a morula (solid ball of cells)

– Day 5, morula has developed into a blastocyst (hallow ball of cells)

Attaches to uterine lining on day 6 and is fully implanted by day 10

Blastocyst stage is where identical twins can result if cells are split into two

Embryonic Development StructuresEmbryonic Development Structures

Amnion – thin sac which forms around the embryo and is filled with amniotic fluid to cushion and insulate the egg.

Chorion, the allantois, and yolk form the placenta two weeks after fertilization

– Chorion and allantois help form the placenta

– Yolk serves as the first red blood cell formation for the embryo

Placenta – organ that provides food and oxygen as well as removes wastes from the baby (grows into the wall of the uterus)

Umbilical chord contains blood vessels which serves as the connection between mother and child (no blood ever mixes, just very close so diffusion occurs)

6 Weeks6 Weeks

12 Weeks12 Weeks

14 Weeks14 Weeks

16 Weeks16 Weeks

16/20/24 Weeks16/20/24 Weeks

28/32 Weeks28/32 Weeks

30 Weeks30 Weeks

Fetal Development BrainPopFetal Development BrainPop