Reproduction and Development

Chapter 38

The last unit!

Human Reproductive Systems

Male Anatomy

Testes

• Produce sperm and hormones

• Seminiferous tubules small, coiled tubes

• Meiosis 1 cell = 4 functional sperm

Epididymis

• Matures and stores sperm

• Located anterior to each testis

• 300 million mature sperm per day

Scrotum

• Outpocketing of body wall

• Contains testes and epididymises

• Temperature 3o C cooler than body temp.

Vas deferens

• Tubes connecting epididymises to the urethra

Urethra

• Tube exiting body

• Transport of urine and semen

Seminal vesicles

• Secrete a fluid high in fructose

• Energy for mobile sperm

Prostate gland

• Secretes a thinner fluid for mobility

• Closes off urinary bladder during ejaculation

Bulbourethral glands

• Cowper’s gland

• Secrete a clear alkaline fluid

• Protection of sperm against acidic female reproductive tract

Semen

• Mixture of sperm and secretions

Penis

• Specialized adaptation for sperm delivery

Puberty in males

Hypothalamus

• Controls pituitary secretions

• FSH sperm production

• LH testosterone production

Secondary sex characteristics

• Growth and maintenance of gonads

• Production of sperm

• Increased body hair growth

• Increased muscle mass

• Increased growth of long bones

• Deepening of voice

Human Female Anatomy

Ovaries

• Produce egg cells in follicles

• Production of hormones

• Meiosis 1 cell = 1 functional egg– 3 polar bodies that form the yolk

Oviducts

• Fallopian tubes

• Transport of egg to uterus

• Fertilization occurs here

Uterus

• Pear-shaped organ of smooth muscle

• Embryonic development occurs here

Cervix

• Narrow lower end of uterus

Vagina

• Birth canal

• Muscular passageway exiting body

Puberty in females

Hypothalamus

• Controls pituitary

• FSH development of mature follicle– Secretion of estrogen by ovary

• LH stimulates ovulation

Secondary sex characteristics

• Growth and maintenance of gonads

• Increased body hair growth

• Increased growth of long bones

• Broadening of hips

• Fat deposits: breasts, buttocks, thighs

• Onset of menses

Egg cell production

• Egg cells start development before birth• Arrested in prophase I– Primary oocytes 2 million– 40,000 left at puberty

• FSH stimulates meiosis• Ovulation mature egg ruptures

through ovary– 400 eggs over lifetime

Menstrual cycle

• Producing mature eggs and preparing uterus for implantation

Flow phase

• Days 1-5

• Shedding of endometrial lining

• Uterus contracts to expel

• Blood levels of FSH begin to rise

Follicular phase

• Days 6-14 (variable)• Follicle develops• Estrogen repair of uterine lining• LH blood level spikes just before

ovulation• Ovulation Day 14• Increased body temp., cervix produced

mucous

Luteal phase

• Days 15-28

• LH follicle fills with cells (corpus luteum)

• Corpus luteum secretes progesterone thickens uterine lining

• Progesterone inhibits FSH and LH

• Uterine lining begins to shed

Development before birth

Fertilization and implantation

• Egg cell 24 hours

• Sperm cells 48 hours

Fertilization

• n + n = 2n (zygote)

• Cap of sperm enzymes to penetrate egg

• Sperm nucleus enters egg

• Egg membrane changes only 1 sperm

• 2 nuclei fuse zygote

Zygote travels to uterus

• 6 days

• Cleavage repeated mitotic divisions

• Blastocyst hollow ball of cells

Implantation

• Embryo implants in thick uterine lining

• 7-8 days

Embryonic membranes and the placenta

Amnion

• Thin inner membrane filled with amniotic fluid

• Shock absorber

• Regulates embryonic body temperature

Allantois

• Outgrowth of digestive tract

• Umbilical cord forms from blood vessels

Chorion

• Outer membrane

• Chorionic villi become part of placenta

Placenta

• From chorion and uterine wall

• Exchange of nutrients and wastes

• Blood vessels from mother and embryo have no direct contact diffusion

Hormonal maintenance of pregnancy

• hCG (human chorionic gonadotropin) secreted by embryo

• Keeps corpus luteum from degenerating

• Steady supply of progesterone

• After 3 months, uterus takes over

Multiple embryos

• Fraternal twins 2 eggs, 2 sperm

• Identical twins 1 egg, 1 sperm– 1 zygote separates into 2 separate embryos

Fetal development

• Growth, development, and cellular differentiation

First trimester

• Organ systems form

• Sensitive to outside influences alcohol, tobacco, other drugs, malnutrition

• 8th week all are formed (fetus)

• Sex can be determined

Second trimester

• Growth

• Could survive outside uterus with assistance

• Cannot maintain constant body temp.

• Immature lungs no regular respiratory rate

Third trimester

• Rapid growth

• Mass of fetus more than triples

• 7th month fetus moves

• 8th month eyes open

• 9th month head in downward position

Gestation

• Length of pregnancy

• About 266 days

Birth, growth, and aging

Birth

Labor

• Oxytocin secreted from pituitary

• Cervix dilates, uterus contracts

• Up to or over 24 hours

Expulsion

• Uterine contractions force baby through birth canal

• 20 minutes to 1 hour

Placental stage

• Expelled 10-15 minutes after birth

• Uterus contracts prevents hemorrhaging

Growth

hGH

Infancy

• First 2 years

• Physical coordination

• Mental development

• Tremendous growth

• Learn to control limbs, walk, first words

Childhood

• Infancy to adolescence

• Steady growth

• Learn to reason and think critically

Adolescence

• Begins at puberty

• Reach maximum physical stature and mass

Adulthood

• No more growth

Aging

• Decreased metabolism and digestion

• Skin loses elasticity wrinkles

• Less pigment in hair follicles

• Bones thinner and more brittle

• Vision and hearing might diminish

Aging cont.

• Stature may shorten disks between vertebrae become compressed

• Genetic causes

• Rate varies interaction of genes and environment