Characteristics of development across the lifespan, including the process of fertilisation and stages of prenatal development, and the physical, social, and emotional development of children, adolescents, adults and older adults.
The process of fertilisation and prenatal stage of the lifespan
Reproductive systems – the primary function of the reproductive systems of the male and female is to produce sex cells called gametes. The gametes are called ova in the female and spermatozoa (sperm) in the male. The sex organs that produce the gametes are called gonads. In males the gonads are the testicles and in the female the gonads are the ovaries.
The following is to be reviewed in conjunction with the reproductive systems handout –
The Male Reproductive system
- The testicles - 1. Production of sperm
- 2. Production of sex hormone, testosterone
- The scrotum – regulates the temperature of the testes
- Epididymis – Maturation and storage of sperm
- Vas deferens and semen producing glands – tube in which sperm travel and mixed with seminal fluid
- Penis and Urethra – Penis is the male organ used for sexual intercourse or for passing urine from the bladder. Urethra – tube through penis which sperm and urine pass through.
The Female Reproductive system
- The ovaries – 1. Store a females ova (approximately 300 – 400 immature ova)
-2. Produce sex hormones oestrogen and progesterone
- Fallopian tubes – ducts to the ovaries that lead to uterus. Fertilisation normally takes place here.
- Uterus – 1. It provides the location and necessary conditions for implantation of the zygote
-2. It increases in size and alters shape to adapt to the rapidly growing baby
-3. It contracts during the birth process, helping to deliver the baby.
- Cervix – muscular ring (3cm wide), which projects into the upper end of the vagina. Can contract to 10-12cm during birth.
- Vagina – 1. provides a passage from the uterus to the outside of the body.
-2. Sperm are deposited during sexual intercourse
-3. It serves as the passage through which a baby emerges to the outside world.
Process of fertilisation
If an ovum is present in the upper part of the fallopian tube it will be surrounded by sperm. This occurs approximately 24 hours after ovulation. Each sperm releases enzymes which start to digest the outer coating of the ovum. Although only one sperm will fertilise the ovum, as after entering the membrane will close behind it. The successful sperm will lose its tail and the nucleus of the sperm and ova will fuse together. Once this has occurred fertilisation is said to have taken place. The usual site for this to occur is in the fallopian tubes. The new cell will contain 46 chromosomes, 23 coming from the sperm, and 23 from the ova.
Stage of Prenatal Development
Gestation (pregnancy) can be divided into 3 stages
- The Germinal Stage
- The Embryonic Stage
- The Foetal Stage
The Germinal Stage
This stage begins at fertilisation and ends at implantation (approximately 10 days). The Zygote (the initial cells that result from fertilisation, contains all genetic material from both parents) is swept towards toward the uterus by muscular contractions and tiny hairs in the fallopian tube.
The single cell zygote divides many times by mitosis. Approximately 1 and a half days after fertilisation - 2 cells, end of 2 days - 4 cells, end of 3 days – 16 cells.
After approximately 4 days a solid mass of uniform cells exist which are called a Morula.
By about seven days the cells begin specialising/differentiating according to directions given by genes. The morula has now transformed to a Blastocyst. The Blastocyst attaches to the lining of the uterus (Endometrium). This is called implantation and marks the end of the germinal stage.
The Embryonic Stage
Starts when implantation is complete (middle of week four) and continues until week 10. Growth and development of the embryo results in the formation of the basic structure of body organs and systems.
Describe the amniotic sac, umbilical cord and placenta.
The Foetal Stage
Starts with the beginning of the 11th week and ends at birth (around week 40). During this stage the foetus builds upon the basic body systems and features already formed, resulting in a rapid increase in size and complexity of the body.