HUMAN DEVELOPMENT

Human development is of growing to maturity, starting from one single celled zygote
to an adult human being. The main hormones concerned with growth are thyroid hormone,
pituitary growth hormone, pituitary gland gonadotrophic and the sex hormone testosterone
and oestrogen. The human female reproductive system prior to birth is designed to facilitate
growth and development of a child (Waters, 2008). Each individual component of the female
reproductive system has a particular set of functions associated with child bearing.
The ovaries are small, oval in shape located on either side of the uterus. They are the
female gonads which produce eggs and are supposedly to be two in the female body. The
ovaries have two main reproductive functions; they produce reproductive hormones;
progesterone and oestrogen, and produce the oocytes for fertilisation. According to Waters
2008, ovaries functions are controlled by gonadotropin releasing hormone release by the
nerve cells in the hypothalamus sending its messages to the pituitary gland to produce follicle
stimulating hormone and luteinising hormone which are carried in the bloodstream to control
menstrual cycle.
The oviduct is the tube linking the ovary and the uterus and provides the necessary
fertilisation environment for initial development of conceptus. It provides regulated
checkpoints for unfertilised eggs and its mucosal walls produce oviduct secretions that are
integral for; supporting spermatozoa in the oviduct, supporting unfertilised oocyte and
development of the early embryo (Crandell, Crandell, & Vander Zanden, 2011). The oviduct
is lined with cilia that are tiny hairs on the cells. In every month, an oocytes develops,
matures and it is released from an ovary. The cilia at this point waft the egg along the inside
of the fallopian tube (oviduct) in to the uterus.

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The uterus (womb) found in the female reproductive system is a pear shaped, hollow
muscular organ responsible for embryo and foetus development during pregnancy. The
fertilised ovum is implanted in the endometrium and fro blood vessels it derives nourishment.
The fertilized ovum develops to an embryo, becomes a foetus and continues developing till
child birth. It provides support and structural integrity to the bowel, bladder, organs and
pelvic bone, separating the bladder and the bowel. The network of nerves and blood vessels
in the organ direct blood flow to the pelvis and external genitalia including; labia, vagina,
ovaries and clitoris for sexual response and it is needed for the occurrence of uterine orgasm
(Waters, 2008).
The cervix is the lowest part of the uterus with strong muscles and narrow opening. Its
function is allowing menstrual blood flow from uterus in to the vagina and directing sperms
into the uterus during coitus. It also protects the upper reproductive tract, uterus and
developing fetus from pathogens, promotes fertility and play a role in women sexual
pleasure. The vagina receives penis during sexual intercourse and serves as a conduit for
menstrual flow from the uterus. During childbirth, the babies pass through the vagina (birth
canal).
The prenatal development is the process of baby development inside the mother’s
womb, taking about 38weeks to complete. During the time, a single cell becomes a full-term
baby with the process divided in to three primary stages; germinal period, embryonic period
and fetal period. Germinal period occurs two weeks after conception, the union of the egg
cells and sperms forms a zygote which moves along the fallopian tube to the uterus (Crandell,
Crandell, & Vander Zanden, 2011). On reaching the uterus, the zygote becomes a blastocyst
and begins to implant on the uterus walls. The period ends when the blastocyst is fully
implanted in the uterine tissue.

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The embryonic stage lasts from germinal stage end to two months after conception;
the cells at this stage are called an embryo with the formation of major organs taking place.
At this stage, the embryo is fragile with biggest dangers including; teratogens which can
cause deformities of the embryo and at the end of this stage the embryo is an inch long. Fetal
period is the last prenatal lasting from two months after conception until birth and in a month
after the stage, fetal sex organs begin to develop. The fetus grows quickly as muscles and
bones develop, organ system later develops and begins to function. In the last three months,
the brain increases rapidly, formation of insulating fat layer under the skin and digestive and
respiratory system start working dependently.
Genotype and phenotype are terms used to differentiate between an organism genetic
makeup and the way it expresses itself (Crandell, Crandell, & Vander Zanden, 2011). A
genotype refers to the actual gene set of an organism. In contrast, a phenotype refers to the
character observable expressions and their traits as coded by those genes. A genotype
depends on hereditary information given by parents to an individual while a phenotype
depends on genotype and the environmental influence. Genotypes are partly inherited by
offspring’s from one of the two alles during reproduction but phenotypes aren’t inherited.
According to Malcolm & Goodship, 2001, genotype can be determined by using a biological
assay like PCR to find the genes on an allele while phenotype is determined through
observing an individual.
Human bodies are composed with millions of cells with every cell nucleus having a
complete person’s genetic makeup coding (Sadava, 2008). Genetic blueprints of individuals
are located in the genes cells. Each gene is a unique slice of genetic data, made of DNA
strands and on the chromosome; each gene has its unique job. The genes contains information
on how we look; our height, eye and hair colour, curl in our toes and our ears shape. Human

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beings have 46 chromosomes with 23pairs on every cell nuclear with one pair contributed by
the mother while the other by the father. Chromosomes are strings of beads that are genes.
The chromosomes and therefore the genes are composed of a chemical substance
called DeoxyreboNucleic Acid (DNA). The DNA that makes the genes on the chromosomes
string is called coding DNA as it is responsible for all genetically characteristics passed from
one generation to another (Sadava, 2008). On the chromosome strings between the genes,
there is a DNA referred to non-coding DNA. This DNA is useful in defining biological
relationships and it obtains solid evidence during forensic laboratory evaluations

References

Crandell, T., Crandell, C., & Vander Zanden, j. (2011). Human Develoment (10th ed., p.
476). New York: Mc Graw-Hill.
Malcolm, S. & Goodship, J. (2001). Genotype to phenotype. Oxford: BIOS Scientific
Publishers.
Sadava, D. (2008). Understanding genetics. Chantilly, Va: Teaching Co.
Waters, S. (2008). The female reproductive system. New York: Rosen Central.