The Reproductive System and Its Physiology

 
Reproduction in humans
Reproduction is the method by which humans provide survival of our species. It
involves the fusion of 2 gametes, spermatozoan and egg. In human, these gametes are numerous
and specific for the male and female (Mueller, Hassel, & Grealy, 2015, p. 3). Reproduction in
humans is performed by male and female reproductive systems (Shaw, Luesley, & Monga,
2011, p116). The main organs of the male genital system are testicle and gonads. The female
genital system includes vagina, ovaries, and uterus. Main events in human reproduction are the
production of sperms and egg, copulation, and fertilization (Kidder, 2016, p.24).
Sperms appear in seminiferous tubules present in male sex organ testis. This method is
known as spermatogenesis. The precursors of the sperm cell the diploid spermatogonium divide
mitotically to supply various spermatogonia and differentiate into spermatocytes (Kidder, 2016,
p.29). Spermatocytes endure cell division biological process to provide four haploid spermatids.
Spermatids differentiate and change into sperm cell (Granata et al., 2011, p.73). Sperms are
single-celled male gametes with a head and a tail (Kidder, 2016, p.30). Ovum, sex cell is made
within the ovaries of the female system. This method is thought as gametogenesis. The
development of ovary start typically and soon regress due to the absence of oocytes (Watson,
2015, p.10). Diploid oogonia and first oocytes made in the fetus and by the time they are born,
females have concerning 1–2 million oocytes. In oocytes, the primary cell division (meiosis I)
can be initiated then stopped (Schroeder, 2017, p.8). No more development happens until the
woman becomes sexually mature. The stage of parturition starts before labor pains begin
(Kidder, 2016, p.27). Development may be influenced by the status of chromosomes in different
ways from the endocrine system and gonads (Shaw, Luesley, & Monga, 2011, p.116).
REPRODUCTIVE SYSTEM 3
The Role of Hormones in Reproduction
Reproductive hormones play an essential role in all aspects of sexual development and
differentiation. I will look at two significant chemical types of hormones: 1) steroids, which include
testosterone and oestradiol; 2) peptides, which include prolactin and gonadotrophins. The posterior
pituitary releases vasopressin, also known as antidiuretic hormone and Oxytocin (Kelly, 2006,
p.20). Oxytocin cause milk production in suckling women. It helps in the contraction of uterine
walls during birth. According to Widmaier et al., (pg.381), Oxytocin is the key factor in affiliative
behavior. Adrenal cortex and the gonads produce sex steroids. Apart from the reproduction role,
they have a wide variety of metabolic effects. Sexual differentiation is fostered by androgen.
Together with oestrogens, they are responsible for the development of secondary sexual behavior at
puberty. Progestogens and oestrogens are responsible for the maintenance and establishment of
pregnancy and lactation in women while androgen is crucial for spermatogenesis in men. Both
oestogens and androgens are responsible for sexual arousability or sexual desire and response. In
most cases, as the level of progesterone and possibly oestrogen rises, there is a dramatic switch
from a negative to positive feedback triggered when persistently increasing estradiol concentrations
reach a critical point. This explains why LH proceeds ovulation in the menstrual cycle (Hall, &
Guyton, 2011, p.1039).
Oestrogens are produced by the adrenal cortex in both women and men for postmenopausal women, peripheral aromatization, mostly in adipose tissue of androstenedione is an
important source of oestradiol. Progesterone is produced in the corpus luteum of the ovary. It
also occurs as an intermediate stage in the production of other hormones in the adrenal cortex
and gonads (Hall, & Guyton, 2011, p.1040). In female androstenedione can be converted into
destradiol in the tissue. This is an important source of dihydrotestosterone. Approximately fifty
percent of female androstenedione comes from the ovary and the rest from the adrenal cortex. 
REPRODUCTIVE SYSTEM 4
The testis produces hormones that are responsible for the development of the fetus as male.
Without normal testis, the fetus would develop as female (Widmaier et al., 2011, p.382). It
explains why maleness require more active intervention, while femaleness is just a default
position. Sexual determination and development of sexual identity are explained in various
stages, e.g., chromosomal, gonads, hormones, sexual organs, gender identity and gender
assigned at birth (Hall, & Guyton, 2011, p.1042). In a fascinating process, these stages lead on
the next.
In the male fetus, the testis produces steroids like testosterone as early as the 8th week
set off. Later steroidogenesis is reduced, but testis continues to grow. It is a very important stage
for differentiation of male external and internal genital organ