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Human Reproduction

Meiosis and Gametogenesis

Meiosis

  • Meiosis is a special type of cell division that produces haploid cells and compensates for the doubling of chromosome number that occurs at fertilization.
  • Meiosis in humans produces sperm cells and ova which each contain 23 chromosomes.
  • When fertilization occurs, the diploid condition 2n=16 is restored in the zygote.
  • Maternal set and other partneral set is for complete set of 23 chromosome.
  • Gametes are the only cells in the human body that are not produced by mitosis.
  • Gametes are produced in the ovaries or testes by the process of meiosis.

Fertilization

Fertilization

  • Millions of sperm swim inside the uterus to find the egg.
  • Sperm comes in contact with the egg in the fallopian tube.
  • the sperm penetrates the egg.
  • the egg is fertilized and continues it's path to the uterus as a zygote.
  • This all takes place in an organ within the mothers abdomen called the uterus.

Male Gametes (sperm)

Male

Gametes

(sperm)

  • sperm is produced in the testes of males,
  • sperm travels through epidydymis (where its stored).
  • The scrotum contains testes which produce sperm.
  • Sperm travels through vas deferens and creates semen and gets mixed with fluid, then gets released from the urethra.

Female Gametes (egg)

Female

Gametes

(egg)

  • Eggs are formed in the ovaries.
  • One egg is discharged into fallopian tube (oviducts) and makes it's way to uterus.
  • Ovaries contain fluid filled cavities called follicles.
  • The uterus gets ready for the egg by building up a wall called the endometrium.

Hormones

Male Hormones

  • The specific hormone involved in the production of sperm is FSH and testosterone.
  • When FSH reaches the testicles it helps start production of sperm in the sperm- producing tubes.
  • The second hormone that helps produce sperm is testosterone - it is produced in the testes.
  • testosterone helps with secondary sexual characteristics.

Hormones

Female Hormones

  • The specific hormones involved in the production of eggs are FSH and Testosterone.
  • When FSH gets to the ovaries it helps release eggs, most of the time only one egg gets to leave every month.
  • FSH also makes the ovaries produce estrogen. Estrogen is a reproductive hormone, it also makes changes in the female body like, fat in breasts and hips, and growth of arm-pit and pubic hair.

Zygote (SINGLE CELL)

Zygote

  • A single cell that is produced when an egg is fertilized, the first cell in human history.
  • A diploid cell that results from the union of 2 haploid gametes.
  • A zygote contains the maternal and paternal haploid sets of chromosomes from the gametes and is diploid (2n).
  • The zygote divides rapidly through the process of mitosis and becomes an embryo within 6-10 days of fertilization.
  • Later the cell divisions begin to specialize and cells are able to do different tasks.
  • The egg attaches to the nutrient rich wall called the endomitrium.
  • Around three days after the egg is fertilized, it becomes a blastocyst which is when the cells are dividing rapidly.
  • As humans develop from a zygote to sexually mature adults, the zygote genetic info is passed with precision to all somatic cells by mitosis.

Interphase

  • DNA replication occurs during interphase.
  • Chromatin (long strands of DNA that will be tightly packaged into smaller volume to fit in the cell) replicate and make up chromatids (one half of a replicated chromosome).
  • The replicated chromatin coils up to form diffuse double strandred chromosomes which are eventually joined in the middle by a centromere.

Mitosis

Mitosis: Cell division that results in 2 daughter cells each with the same chromosomes, after cells period of interphase, there are 4 major phases to mitosis that take place in following order:

1) Prophase

2)Metaphase

3)Anaphase

4)Telophase

Mitosis

Prophase

  • The chromatin, diffuse in interphase, condenses into chromosomes.
  • Each chromosome has duplicated and now consists of 2 sister chromatids.
  • At the end of prophase, the nuclear envelope breaks down, and spindle fibres begin to form from centrioles.

Metaphase

  • The chromosomes align at the equitorial plate, are held in place by spindle fibres attached to centromere.
  • The cell's chromosomes condense, move toward one another, and align in the middle of the dividing cell as the nucleus dissolves.

Anaphase

  • The spindle fibres contract and shorten pulling the centromere apart.
  • Sister chromatids (one of each of the replicated strands) seperate and move toward the corresponding poles.
  • The cell elongates.

Anaphase

Telophase

  • Daughter chromosomes arrive at the poles and the spindle fibres disapear.
  • The chromosomes decondense to chromatin and the nuclear envelope reapears.
  • The cytoplasm divides, the cell membrane pinches inward ultimately producing 2 daughter cells (cytokinesis)

Cytokinesis

  • Now there are 2 seperate nuclei, but they are in the same cell.
  • The cell now needs to be split in half.
  • Cytokinesis begins in anaphase and continues on through telophase.
  • The first visible sign of cytokinesis is when the cell begins to pucker in, a process called furrowing.
  • The 2 cells will continue the cell cycle and begin their interphase again.

Blastocyst

Blastocyst

A blastocyst is formed when the zygote is rapidly dividing and creating cells for different things, after dividing cells, the cells of the inner group will become an embryo. The hormones involved are estrogen and progesterone.

Embryo

  • 6-10 days after fertilization the zygote is an embryo.
  • The embryo starts to develop it's spine and limbs.
  • If an embryo develops and attaches to the lining of the uterus.
  • the hormone that keeps the uterine lining in place stopping menstrual flow is estrogen.

Fetus

  • 4 weeks after fertilization the head of the embryo is partly formed and the heart starts to beat.
  • After 8 weeks bone cells begin to develop, it is now a fetus.
  • Starts building up a body structure for the next 7-8 months.
  • It lives inside the mothers uterus until time to give birth.
  • Once the fetus is born, it's then called a baby.

Child Birth

Child Birth

  • After 9 months of carrying the fetus the mother gives birth by pushing the baby out of her uterus.
  • another way if labour doesn't work is c-section.
  • The first hormone involved in the process of child birth is oxytocin, it's role is to stimulate the uterusto contract and open the birth canal.
  • the second hormone is progesterone, it maintains the pregnancy and a some of it causes muscles of the uterus to contract.

Toddler

A toddlers will show more independence, identify themselves in mirrors or photos, and copy the actions of others, particularly parents and older siblings. A toddler will learn to speak, crawl, and walk.

Child

A child will learn to climb and run. enjoys playing with other kids, has trouble sharing. cries often, but feelings and emotions change quickly. A child learns and grows most of the time by playing.

Teenager

teenager

A teenager may gain many inches in a few months, then have fairly slow development for a while before experiencing another growth spurt. also have changes with puberty.

Young Adult

A young adult is most likely able to produce his or her gametes (sperm or egg) therefore likely able to reproduce by combining their gametes with opposite sex.

young adult

Hormones

What are hormones?

Hormones are chemical messengers made by your body's endocrine system. They travel in your bloodstream to tissues or organs. They affect many different processes, including: growth and development, metabolism, how your body gets energy from the foods you eat, sexual function, mood, and reproduction. Hormones have three categories:

1) Lust 2) Attraction 3) Attacment.

How do we get hormones?

Endocrine glands, which are special groups of cells, which make hormones. The major endocrine glands are: pitruitary, pinial, thyroid, thymus, adrenal, and pancreas.

Lust

Lust

Driven by desire for sexual gratification. The need to reproduce stems from an evolutionary basis as a way to pass on genes and perpetuate species. Hypothalamus of the brain stimulates production of sex hormones testosterone and estrogen in testis and ovaries.

Attraction

Dopamine and norepinephrine are released during attraction, produced by the hypothalamus of the brain, the primary "rewards" centers of the brain triggered, Reduction in serotonin which underlies overpowering infatuation.

Attachment

Predominant factor in long-term relationships. The primary hormones include oxytocin and vasopressin, are important for bonding, both hormones are released by hypothalamus.

Attachment

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