The reproductive system

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Human Biological Science2/ The Human Life Cycle





Have tiny tubules containing diploid cells called spermatogonium that mature to become sperm.

In spermatogesis, one round of meiosis gives rise of four spermatids, which in turn are metamorphosed into four sperms

Formation of haploid cells from an original diploid cell, called a primary oocyte, through meiosis.

In oogenesis, one round of meiosis gives rise to one ovum.


spermatogenesis is in male

spermatogenesis happens continuously

spermatogenesis makes 4 sperm per round of meiosis

Oogenesis is in female

Oogenesis is prompted by hormone cycles

Oogenesis produces one egg (the rest are polar bodies) per round of meiosis

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  1. The secondary sexual characteristics begin during puberty as a result of hormonal stimulation. The changes become obvious first in females and a little later in males. in male the appearance of pubic, and facial hair such as chest and armpits called axillary hair, increased muscle mass and strength and growth of the testicles and penis; sperm production. As the male sex organs grow in size, the larynx also enlarges. As a result, men generally have a deeper voice than women. Female secondary characteristics start with menstruation, widening of the hips wider than the shoulders. Breasts begin to enlarge fatty tissue in and around the breast also production of body hair in certain areas such as armpits and pubic hair.

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  1. Aging changes in the female reproductive system is due to hormone level changes and menstrual period stop permanently. This is called menopause. Menopause is a normal part of a women's aging process occurs between age ranges 45-55. With menopause the ovaries stop making the hormone oestrogen and progesterone and ovaries stop releasing ova this can cause anxiety, depression and sleep problems. After menopause a women cannot get pregnant. as hormone levels fall, other changes occur in the reproductive system include virginal walls become thinner dryer, less elastic, higher risk of virginal yeast infections, these changes can result in painful intercourse. Other changes include symptoms such as hot flashes, moodiness, headaches and short term memory. Breast tissues may decrease, Fibrous tissue in the breast is replaced with fat, this makes breast less firm and higher risk of bone loss leads to osteoporosis. furthermore urinary system changes such as urgency of urination and increased risk of urinary tract infection and muscle can lose tone resulting in vagina, uterus and bladder falling out of proportion condition called prolapse this can cause a feeling of pelvic pressure or fullness.

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Difference between spermatogenesis and oogenesis, 2014, (online), available at accessed on 26/05/2014

The Secondary sexual Characteristics, (online), available at accessed on 27/05/2014

Aging changes in the female reproductive system, 2014, (online), available at accessed on 27/05/2014


The duration of a menstrual cycle has four main stages.


First stage is menstrual stage which occurs between say 1-5. The uterus sheds inner lining of soft tissue and blood vessels which exits the body from the vagina in the form of menstrual fluid. During this stage woman’s experience abdominal cramps.

Phases of menstrual cycle, 2012, (online image), available at accessed on 27/05/2014

IllustrationThis stage is Follicular phase, day 1 to 13

The pituitary gland secretes Follicle-stimulating hormone that stimulates the egg cells in the ovaries to grow.

While the egg cell matures, its follicle secretes oestrogen that stimulates the uterus to develop a lining of blood vessels and soft tissue called endometrium. Ovulation occurs at increase in luteinising hormone that causes the egg release.

Phases of menstrual cycle, 2012, (online image), available at accessed on 27/05/2014


This is the ovulation stage. On the 14th day of the cycle, the pituitary gland secretes Luteinising hormone that causes the ovary to release the developed egg cell. The released egg cell is swept into the fallopian tube by the cilia of the fimbriae. The egg moves down the fallopian tube for few days and the lining of the uterus continues to grow.

Phases of menstrual cycle, 2012, (online image), available at accessed on 27/05/2014

Illustration This stage is luteal phase from day 15-28

The egg cell released during the ovulation stage stays in the fallopian tube for 24 hours. If a sperm cell does not impregnate the egg cell within that time; the egg cell disintegrates. The cells of the corpus luteum produce oestrogen and large amount of progesterone, with the latter hormone stimulating the uterine lining development in preparation for implanting fertilised egg. The progesterone hormone that causes the uterus to retain its endometrium gets used up by the end of the menstrual cycle. This causes the menstrual phase of the next cycle to begin.

Phases of menstrual cycle, 2012, (online image), available at accessed on 27/05/2014

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Phases of menstrual cycle, 2012, (online), available at accessed on 27/05/2014

Your cycle, 2014, (online) available at accessed on 27/05/2014


Human chorionic gonadotropin (HCG) is a hormone produced by the cells that from the placenta, which nourishes the egg after it has been fertilised and become attached to the uterine wall. The HCG levels will double every 72 hours and reach its peak in the first 8-11 weeks of pregnancy. The level can be detected by blood test and urine test from 7-9 days.

During the menstrual cycle, when an egg is released from theovaryatovulation, the remnants of the ovarian follicle (which enclosed the egg) form a new, temporary ovarian gland called thecorpus luteum, which produces the hormoneprogesterone. If, after two weeks, the ovulated egg remains unfertilised, thecorpus luteumstops producing progesterone. Through a feedback mechanism, this signals thepituitary glandto producefollicle stimulating hormone(and to a lesser extentluteinising hormone) to initiate the next menstrual cycle. However, in the event that the ovulated egg is fertilised by sperm and an embryo is conceived, it is vital that thecorpus luteumcontinues to produce progesterone until the placenta is established (the placenta then takes over progesterone production). Human chorionic gonadotrophin is the embryonic hormone which ensures thecorpus luteumcontinues to produce progesterone throughout the first trimester of pregnancy.

As well as maintaining progesterone production from the ovary, human chorionic gonadotrophin may also play a role in making sure the lining of the uterus (endometrium) is ready to receive the implanting embryo. Recent studies have indicated that human chorionic gonadotrophin may help to increase the blood supply to the uterus and be involved in re-shaping the lining of the uterus in preparation for the implanting embryo.