Human reproduction and development



Human reproduction & Development notes

Reproduction is the formation of new ___individuals________ -- important for the ___survival________ of the _____species____, but not necessary for the ___individual________ organism.

The reproductive system ___produces______, ____stores_____ and ____releases______ specialized __sex_____ cells (____gametes______) that have ___half__ the information needed to make a new organism.

Sexual development

Male sex cells are called __sperm_______, female sex cells are called ____ovum_____ or ____eggs____. Gametes are made during ___meiosis_________.

Union of a sperm and egg cell forms a __zygote_______ -- which contains _all_____ the ____genetic_____ information to make a new individual!

For the first __6_____ weeks of development, both male and female ___embryos___ are ____identical_____! During the 7th week, the primary ___reproductive_____ organs start to form -- __testes______ in males and ___ovaries____ in females.

The ___pituitary______ gland releases hormones that __stimulate____ the testes and ovaries.

The two main hormones are FSH (follicle ___stimulating___ hormone) and LH (___leutenizing____ hormone).

FSH and LH cause the __testes_______ in males to produce ____testosterone_______. Testosterone will start to produce ___male_____ characteristics in __puberty_______.

FSH and LH cause the ___ovaries_______ in females to produce __estrogen________.

Estrogen will produce __female_______ characteristics in puberty.

|The male reproductive system |[pic] |

|Main function of the male reproductive system is to __produce______ and | |

|_____deliver____ sperm. | |

|Shortly before birth, the __testes________ descend into the ___scrotum_______ --| |

|an ____external_______ sac. | |

|This keeps the testes ___2-4°C___ cooler than body temperature, which is | |

|___essential_______ for proper sperm ___development_________. | |

Glands lining the reproductive tract produce ___nutrient______-rich fluid called ___seminal____ fluid – it ___nourishes_______ and ___protects_______ the sperm from the ___acidity______ in the female reproductive tract.

During sexual ___arousal_______, blood vessels in the penis ___fill_____ with blood, preparing to deliver ___sperm_____. Sperm are __ejected______ from the penis by contractions of ___smooth_______ muscle lining the reproductive tract – called ___ejaculation__________.

The female reproductive system

Primary organs are the __ovaries_______, which release __eggs_____ and also ___prepare_______ a woman’s body to ____nourish______ a developing ____embryo_______.

|[pic] |Males produce __millions_______ of sperm, but females produce only |

| |__one_____ egg per __month_______! |

| |Each ovary contains __400,000_______ primary ____follicles_____, which|

| |are clusters of cells surrounding a single __egg_____. |

| |Follicles help egg cells ___mature______. |

Females are born with __all___ the ____immature__________eggs that she will ever produce, but only about __400_____ are released within her lifetime. Every 28 days, a follicle __enlarges_____ and completes ___meiosis______, making one ___egg____ and three __polar bodies______.

When the follicle is mature, it __ruptures_______ and releases the ____egg___, which travels down the _____fallopian______ tube to the ___uterus_______. The trip usually takes ____2-3___ days

The menstrual cycle

Egg maturation is part of it, but the ___uterus_____ must also be ____prepared_____ to receive an embryo.

Interaction between the hormones ___estrogen______ and ____progesterone______ are responsible for the female menstrual cycle.

Follicular Phase

Estrogen levels are ___low_____, so the ___pituitary_____ releases FSH and LH to cause a follicle to ___mature______. The follicle produces ___estrogen______, which causes the lining of the __uterus_________ to ___thicken_______ to prepare for receiving a ____fertilized egg______.

This part of the process takes about __10_____ days.

Ovulation

Occurs __midway_____ through the cycle -- lasts ___3-4_____ days. The ___hypothalamus_____ and pituitary release large amounts of __FSH and LH_______ that cause the follicle to __rupture_________ and release the ____egg_____. The egg starts to travel down the ____fallopian_______ tube.

Luteal Phase

After releasing the egg, the follicle turns ___yellow_____ and becomes the _________corpus luteum_______. The corpus luteum continues to make ___estrogen______. But also makes ____progesterone______ -- stimulates the growth of the ___blood______ supply for the surrounding tissue.

Chances of ___fertilization____ are greatest in the first ___2___ days of the luteal phase.

If an egg is fertilized, it will ___implant_____ in the wall of the ____uterus___ and the corpus luteum will continue to make hormones to keep the ____lining___ of the uterus intact.

If fertilization does not occur, the __egg_____ will pass through the uterus without ___implanting____ and the corpus luteum will ___break down_______.

**This decreases the levels of both ___estrogen_______ and ____progesterone________.

Menstruation

Once the level of estrogen falls below a certain point, the __lining______ of the uterus begins to __detach_______. The tissue, along with ___blood______ and the unfertilized ___egg_____, are discharged through the ____vagina______.

This phase usually lasts ___3-7___ days, and a new cycle begins with the __first______ day of menstruation.

Human development

Development begins at ___fertilization______ -- the union of ___sperm_____ and ___egg___.

___Millions________ of sperm are released into the ____vagina______ -- right below the ___cervix_____. Sperm must ___swim_____ up the fallopian tube to find the egg. Once located, __enzymes_______ in the head of the sperm ___dissolve______ the protective layer around the ___egg______ and the sperm can ___enter______ the egg.

|While still in the fallopian tube, the zygote begins __mitosis_______ -- called | |

|____cleavage____ -- the number of cells starts to __double_______. | |

| | |

|After 4 days, the zygote is a _hollow_______ ball of cells called a ____morula______. As | |

|the morula develops, a ___cavity______ forms in the ____center______ and it becomes a | |

|__blastula_______. This ___hollow_____ ball of cells is what ___implants______ into the | |

|wall of the uterus. | |

| | |

|The blastula begins to __differentiate______ or ___specialize_____ into different tissues | |

|as a result of the activity of __genes________. | |

|The inner mass of the blastula then forms __3__ layers – called ____germ____ cell layers in| |

|a process called __gastrulation________. | |

|Ectoderm: becomes the ___skin______ and ___nervous_______ system | |

|Endoderm: becomes the lining of the ___digestive_______ tract and digestive ___organs_____ | |

|Mesoderm: becomes ___muscle_____, ____bone_____, ____connective________ tissue, | |

|___blood_____ and ___reproductive________ organs | |

After gastrulation, a ___neural______ tube forms that will become the ___brain_____ and _____spinal cord__________.

Membranes form to ____protect______ the embryo:

|___Amnion________ forms a fluid-filled sac to ___cushion________ the embryo | |

|___Yolk sac__________ serves as ____nourishment_________ until the ___placenta____ is established | |

|____Chorion______ extends into the _____uterus___ and forms the ___placenta________. | |

| | |

|Placenta supplies ___O2_____ and ____nutrients_____ and removes __CO2_____ and ___waste_______. | |

| | |

|Maternal and fetal blood ____DO NOT______ mix!!!! | |

| | |

|All transfer happens by ____diffusion_______!!! | |

Fetal development

|[pic] |After the ___8th __ week, the embryo is called a ___fetus_______. |

| |By the end of _3__ months, most of the major __organs_____ and ___tissues____ are|

| |fully formed. |

During this time, the ___umbilical cord _________ forms -- contains 2 ___arteries___ and one ___vein____ and connects the fetus to the ____placenta______.

|During the 4th, 5th and 6th months of development, the tissues of the fetus |[pic] |

|become more ___complex______ and ____specialized_______. The ___heart_____ | |

|is large enough to be heard with a stethoscope -- ____bone_____ replaces | |

|____cartilage_____ in the early skeleton. | |

|[pic] |During the last 3 months, the organ systems __mature________ , the fetus |

| |grows in __size____ and ___doubles_______ its mass. The ___lungs______ and |

| |____nervous_______ system complete their development and prepare for life |

| |outside the uterus! |

|After 9 months, the fetus is ready for ___birth_______. The mother’s |[pic] |

|__pituitary___________ gland releases ____oxytocin______, which causes | |

|contractions in the walls of the __uterus_______. | |

Rhythmic __contractions_______ (called labor) push the baby through the

_______birth canal____-- usually ___head_____-first!

The umbilical cord is __cut_______ and ____tied______ -- will eventually become your

____belly button__________.

Multiple Births

Identical twins: a zygote ___splits______ after ____fertilization______ to become two ___separate_________ fetuses. Have ___identical DNA__________!

Fraternal twins: two ___eggs____ are released, fertilized by different ___sperm______ but develop in the same uterus. Share the same amount of DNA as regular ___siblings_______.

Alternate Reproduction

Organisms that live in or near ___water_______ tend to lay ____thousands________ of eggs in the water and wait for males to release ___sperm_______ to fertilize them.

Since fertilization occurs ___outside_______ the mother’s body, this is called _external_________ fertilization. Development also occurs outside the mother’s body, so this leads to ___external_____ development.

Disadvantages: ___many______ offspring produced, but ___few___ survive.

There is ___little____ to no parental involvement, since most of the energy is put into ___production_____ of offspring.

Reptiles and birds have _____internal____ fertilization, but most lay ___eggs____, which develop outside the mother’s body. ____Fewer____ eggs produced, but there is more parental __care____ and ____protection_____. ____Internal_____ fertilization with ___external_____ development usually happens on __land______.

Internal/Internal:

Finally, humans and other __mammals______ have ____internal_____ fertilization and ___internal______ development. Relatively __few____ offspring are produced, but embryos are usually well-__protected_____ by one or both ___parents______.

Water needed!!!!

The key thing needed for __ANY____ type of fertilization is ___water_______!!!

There must be __liquid______ in order for the ___sperm______ to swim to the ___egg____!

Alternate development

Some organisms go through ___changes________ during their life cycles where their __adult_____ form is different from their ____juvenile______ form.

|Incomplete Metamorphosis: | |

| | |

|When the egg hatches, the juvenile looks like a ___mini______ form of the adult (called a | |

|___nymph_______). | |

| | |

|Nymphs and adults live in the ____same_____ environment. | |

Complete Metamorphosis:

Hatched young are called ___larvae______ and look very __different_______ from the adult form.

Larvae: __eat_______ and ____grow_______

Will become a ___pupa_______ when big enough, then form a ___cocoon________.

Emerges from the cocoon as the ___adult_____ form.

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urethra

testis

scrotum

vas deferens

penis

bladder

Fallopian tube

vagina

cervix

ovary

uterus

Ectoderm

Endoderm

Mesoderm

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