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Human Development (biology)

 
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Human development (biology)
 
 
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Human development is the process of growing
Growing

Growing may refer to:* Growth* Growing , a noise band from Olympia, Washington* Growing , a 2007 album by the instrumental rock band Sleeping People...
 to maturity. In biological terms, this entails growth from a one-celled zygote
Zygote

A zygote is a cell that is the result of fertilization. That is, two ploidy cells—usually an ovum from a female and a sperm cell from a male—merge into a single ploidy cell called the zygote ....
 to an adult human being.

lopment begins with fertilization, the process by which the male gamete
Gamete

A gamete is a Cell that fuses with another gamete during fertilization in organisms that sexual reproduction. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete?called an ovum ?and a male produces th...
, the sperm cell
Spermatozoon

A sperm, from the ancient Greek word sp???a and and more commonly known as a sperm cell, is the ploidy cell that is the male gamete. It Fertilization an ovum to form a zygote....
, and the female gamete, the oocyte
Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in biological reproduction. In other words, it is an immature ovum, or ovum cell....
, fuse to give rise to a diploid cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
, the zygote.






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Human development is the process of growing
Growing

Growing may refer to:* Growth* Growing , a noise band from Olympia, Washington* Growing , a 2007 album by the instrumental rock band Sleeping People...
 to maturity. In biological terms, this entails growth from a one-celled zygote
Zygote

A zygote is a cell that is the result of fertilization. That is, two ploidy cells—usually an ovum from a female and a sperm cell from a male—merge into a single ploidy cell called the zygote ....
 to an adult human being.

Biological development

Sperm Egg
Development begins with fertilization, the process by which the male gamete
Gamete

A gamete is a Cell that fuses with another gamete during fertilization in organisms that sexual reproduction. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete?called an ovum ?and a male produces th...
, the sperm cell
Spermatozoon

A sperm, from the ancient Greek word sp???a and and more commonly known as a sperm cell, is the ploidy cell that is the male gamete. It Fertilization an ovum to form a zygote....
, and the female gamete, the oocyte
Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in biological reproduction. In other words, it is an immature ovum, or ovum cell....
, fuse to give rise to a diploid cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
, the zygote. In pregnancy the 3 stages are commonly referred to as ZEF - meaning Zygote, Embryo, Fetus.

In medicine, the beginning of pregnancy is the instant a spermatozoon enters an ovum and forms a viable zygote. Recently, in western medicine, pregnancy is defined as beginning when a fertilized zygote
Zygote

A zygote is a cell that is the result of fertilization. That is, two ploidy cells—usually an ovum from a female and a sperm cell from a male—merge into a single ploidy cell called the zygote ....
 becomes implanted
Implantation

Implantation is an event that occurs early in pregnancy in which the embryo adheres to the wall of uterus. At this stage of prenatal development, the embryo is a blastocyst....
 in a woman's uterus
Uterus

The uterus is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation....
. This occurs when the zygote then becomes embedded into the endometrium
Endometrium

The endometrium is the inner membrane of the mammalian uterus....
 (lining of the uterus) where it forms a placenta
Placenta

The placenta or afterbirth is a highly vascularized ephemeral organ present in Placentalia vertebrates that connects the developing fetal tissues to the uterine wall....
, for the purpose of receiving essential nutrients through the uterus
Uterus

The uterus is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation....
 wall. The umbilical cord
Umbilical cord

In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta. During prenatal development, the umbilical cord comes from the same zygote as the fetus and normally contains two arteries and one vein , buried within Wharton's jelly....
 in a newborn child signifies the remnants of implantation. The definition of pregnancy is controversial as the impact of the definition is significant when discussing abortion, stem cell research and fertility treatments.

The zygote undergoes rapid mitotic
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
 division
Cell division

Cell division is a process by which a cell , called the parent cell, divides into two or more cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle....
s with no significant growth (a process known as cleavage
Cleavage (embryo)

In embryology, cleavage is the division of cell s in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, producing a cluster of cells the same size as the original zygote....
) and cellular differentiation
Cellular differentiation

In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a single zygote to a complex system of Tissue and cell types....
, leading to development of an embryo
Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
.

Childbirth
Childbirth

Childbirth is the culmination of a human pregnancy or gestation period with the delivery of one or more newborn infants from a woman's uterus. The process of normal human childbirth is categorized in three stages of labour: the shortening and dilation of the cervix, descent and delivery of the infant, and delivery of the placenta.....
 is the process in which the baby is born. Age is defined relative to this event in most cultures.

Physical stages of human life


Terms for stages of age-related physical development include, with their approximate age ranges:

  • Prenatal (fertilization - birth)
    • Embryo
      Human embryogenesis

      Human Embryology is the study of the development of an individual before birth.Every individual spends the first nine months of life within the uterus of the mother.Human embryogenesis is the process of cell division and cellular differentiation of the human embryo that occurs during early stages of this development.To be exact, it spa...
       - (fertilization - 8 weeks of gestational phase)
      • Zygote
        Zygote

        A zygote is a cell that is the result of fertilization. That is, two ploidy cells—usually an ovum from a female and a sperm cell from a male—merge into a single ploidy cell called the zygote ....
        , the point of conception, fertilization
      • blastocyst
        Blastocyst

        The blastocyst is the structure formed in early embryogenesis, after the formation of the blastocoel, but before implantation.It possesses an inner cell mass, or inner cell mass which subsequently forms the embryo proper, and an outer layer of cells, or trophoblast which later forms the placenta....
         the period between conception and embryonic stages
      • Embryo
        Embryo

        An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
        ; the embryonic period starts at three weeks and continues until the end of the 8th week of pregnancy
    • Fetus
      Fetus

      A fetus is a developing mammal or other viviparous vertebrate, after the embryonic stage and before childbirth. The plural is fetuses, or sometimes feti....
       (8 weeks of gestational phase - birth)
  • Child
    Child

    A child is a human being between the stages of birth and puberty. The legal definition of "child" generally refers to a minor , otherwise known as a person younger than the age of majority....
     (birth
    Childbirth

    Childbirth is the culmination of a human pregnancy or gestation period with the delivery of one or more newborn infants from a woman's uterus. The process of normal human childbirth is categorized in three stages of labour: the shortening and dilation of the cervix, descent and delivery of the infant, and delivery of the placenta.....
     - age of majority)
    • Neonate (newborn) (0-30 days)
    • Infant
      Infant

      An infant or baby is the term used to refer to the young offspring of humans....
       (baby) (1 month-1 year)
    • Toddler
      Toddler

      Toddler is a common term for a young child who is learning to walk. The toddling stage is generally considered to be the stage of development between infant and childhood....
       (1-4)
    • Play age (3 - 6 years)
    • Primary school age (also called prepubescence) (4-12)
      • Elementary school
        Elementary school

        An elementary school is an institution where children receive the first stage of compulsory education known as Primary education. Elementary school is the preferred term in many countries, especially in North America....
         age (also called middle childhood) (4-8)
      • Preadolescence (preteen, or late childhood. The child in this and the previous phase are called schoolchild (schoolboy or schoolgirl), when still of primary school age.) (10-12)
  • Adolescence
    Adolescence

    Adolescence is a transitional stage of physical and mental Human development that occurs between childhood and adulthood. This transition involves biological , social, and psychological changes, though the biological or physiological ones are the easiest to measure objectively....
     and puberty
    Puberty

    Puberty refers to the process of physical changes by which a child's body becomes an adult body capable of reproduction. Puberty is initiated by hormone signals from the brain to the gonads ....
     (teenage) (13-19)
  • Adult
    Adult

    The term adult has at least three distinct meanings. It can indicate a biologically grown or mature person. It may also mean a plant, animal, or person who has reached full growth or alternatively is capable of reproduction, or a person who has attained the legally fixed age of majority; as opposed to a minor....
     (20-death)
    • Young adult
      Young adult (psychology)

      According to Erik Erikson's stages of human development, first enumerated in Childhood and Society a young adult is generally a person between the ages of 20 and 39, whereas an adolescent is a person between the ages of 13 and 19, although definitions and opinions can vary....
       (20-25)
    • Early adulthood (20-39)
    • Middle adulthood (40-59)
    • Advanced adult/Senior citizen
      Senior citizen

      Senior citizen is a general designation for persons who have reached a certain age, which may vary by different standards. It is often used for legal or policy-related reasons in determining who is eligible for certain benefits available to the age group....
       (60+)
  • Death
    Death

    Death is the permanent termination of the biological functions that define a life organism. It refers to both a particular event and to the condition that results thereby....
     (occurs at various ages, depending on person)
    • Decomposition
      Decomposition

      Decomposition refers to the process by which tissues of dead organisms break down into simpler forms of matter. Such a breakdown of dead organisms is essential for new growth and development of living organisms because it recycles the finite chemical constituents and frees up the limited physical space in the biome....
       (breakdown of the body after death)


Also sometimes used are terms that specify one's age in numbers, such as:
  • Child (0-12)
  • Teenager (13-19)
  • Twentysomething (20-29)
  • Thirtysomething (30-39)
  • Fortysomething
    Fortysomething (term)

    A fortysomething is a person aged between 40 and 49 years. This is generally accepted as the start of middle age. The term quadragenarian has also been used, but rarely used more recently, since around 1980....
     (40-49) (formerly also Quadragenarian, rarely used since 1980)
  • Quinquagenarian
    Fiftysomething (term)

    A fiftysomething is a person aged between 50 and 59 years. This is generally accepted as late middle age. The current crop of fiftysomethings are people born from , to ....
     (50-59)
  • Sexagenarian
    Sixtysomething (term)

    A sixtysomething is a person aged between 60 and 69 years. This is generally accepted as early old age. The current crop of sixtysomethings are people born from , to ....
     (60-69)
  • Septuagenarian (70-79)
  • Octogenarian (80-89)
  • Nonagenarian (90-99)
  • Centenarian
    Centenarian

    A centenarian is a person who has attained the senescence of 100 years or more. Because current average life expectancy across the world are less than 100, the term is invariably associated with longevity....
     (100-109)
  • Supercentenarian
    Supercentenarian

    A supercentenarian is someone who has reached the senescence of 110 years, something achieved by only one in a thousand centenarians . Furthermore, only 1 in 50 supercentenarians live to be 115 and only 1 in 70,000 centenarians lives to be 120....
     (110+)


Comparison table

   years
Child
Child

A child is a human being between the stages of birth and puberty. The legal definition of "child" generally refers to a minor , otherwise known as a person younger than the age of majority....
 prenatal >0
infancy 0 - walking
toddlerhood walking - 3
play age 3-6
preadolescence 10 - 12
adolescence
Adolescence

Adolescence is a transitional stage of physical and mental Human development that occurs between childhood and adulthood. This transition involves biological , social, and psychological changes, though the biological or physiological ones are the easiest to measure objectively....
 13 - 19
Young adult
Young adult (psychology)

According to Erik Erikson's stages of human development, first enumerated in Childhood and Society a young adult is generally a person between the ages of 20 and 39, whereas an adolescent is a person between the ages of 13 and 19, although definitions and opinions can vary....
 twentysomething
Twentysomething

Twenty something or twentysomething may refer to:*Twentysomething , a person in the age group of 20 to 29*Twentysomething , by Jamie Cullum...
 20-29
thirtysomething
Thirtysomething

thirtysomething is an United States television drama about a group of baby boomers in their thirties. It was created by Marshall Herskovitz and Edward Zwick for United Artists Television and premiered on American Broadcasting Company on September 29, 1987....
 30-39
Middle age
Middle age

Middle age is the period of life beyond Young adult hood but before the onset of old age. Various attempts have been made to define this age, which is around the third quarter of the average life span of human beings....
 fortysomething
Fortysomething (term)

A fortysomething is a person aged between 40 and 49 years. This is generally accepted as the start of middle age. The term quadragenarian has also been used, but rarely used more recently, since around 1980....
 40-49
quinquagenarian 50-59
Advanced adult sexagenarian 60-69
septuagenarian 70-79
octogenarian 80-89
nonagenarian 90-99
centenarian 100-109
supercentenarian 110
   


Physical development milestones


  • Ability to lift and control the orientation of the head
  • Crawling begins
  • Walking
    Walking

    Walking is the main form of animal locomotion on Earth, distinguished from running and crawling . When carried out in shallow waters, it is usually described as wading and when performed over a steeply rising object or an obstacle it becomes scrambling or climbing....
     begins
  • Speech begins
  • Voice
    Human voice

    The human voice consists of sound Voice production by a human being using the vocal folds for Speech communication, singing, Laughter, crying, screaming, etc....
     lowers in pitch (especially noticeable in boys)
  • Pubic hair
    Pubic hair

    Although fine Vellus is present in the area in childhood, the term pubic hair is generally restricted to the heavier, longer and coarser hair that develops with puberty as an effect of rising levels of androgens....
     appears
  • Genitals and reproductive organs mature
  • Menses begin (females)
  • Body hair and facial hair
    Facial hair

    Facial hair is a secondary sex characteristic in human males. Many men start developing facial hair in the later years of puberty, approximately between 18-20 years old and most men don't finish developing a fully adult beard until their early 20s or even later....
     appears


Note: the Tanner stages can be used to approximately judge a child's age based on physical development.

See also

  • Child development
    Child development

    Child development stages describe theoretical milestones of child development. Many stage models of development have been proposed, used as working concepts and in some cases asserted as nativism theories....
  • Developmental biology
    Developmental biology

    Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, cellular differentiation and "morphogenesis," which is the process that gives rise to biological tissues, organ s and anatomy....
  • Auxology
    Auxology

    Auxology, sometimes called Auxanology , is a meta-term covering the study of all aspects of human physical human development ; though it is also a fundamental of biology, generally....
  • Embryogenesis
    Embryogenesis

    Embryogenesis is the process by which the embryo is formed and develops. It starts with the fertilization of the ovum, egg, which, after fertilization, is then called a zygote....
  • Mammalian embryogenesis
    Mammalian embryogenesis

    Mammalian embryogenesis is the process of cell division and cellular differentiation during early prenatal development which leads to the development of a mammal embryo....
  • Life-history theory


Footnotes