Negotiated Study One: Research: The Stages of Life

The First Year

At the moment of birth the baby's lungs and circulatory system must adapt to the new, airy environment, and the other body's systems must be brought into play to sustain life outside the womb

Milk secretion begins immediately after birth. For the first few days only a yellowish fluid, colostrum, is produced by the breasts. Colostrum is of great importance to the infant because it contains maternal antibodies which help to protect the baby against infection for about three months, until it's body can produce its own defense mechanisms.

Such a the antibody - forming thymus gland in the neck which rapidly enlarges after birth.

Other important systems within the infants body rapidly mature after birth.

Enzyme systems, for example, within the intestines and the liver are soon able to digest and utilize the mothers milk. The first year is a time of rapid growth.

The infant doubles its birth weight in six months and triples it within a year.

By the age of twenty eight weeks the baby begins to eat solids.

This is the age at which the first recognizable human speech sounds begin to be produced, by contrast to the gurgles and cooing of earlier weeks.

One to Three Years

During this period the brain shows rapid growth and maturation. The most significant development is that of speech and language.

By eighteen months the child may have as many as a dozen teeth. Vocab of up to 12 words.

The two year old has about sixteen teeth and can chew efficiently. 

Vocabulary of three hundred words

Early in the childs second year the nervous system matures sufficiently to allow him to become toilet trained.

Three to Seven

The pattern of growth continues - the brain grows more slowly and the limbs and body develop quickly.

At the age of five the girls ovaries have reached their adult size, but do not function until puberty.

The 1500 word of the 4 year olds vocabulary have become 2200 on average at 5 years old.

Puberty

In both sexes the physiological changes leading to puberty occur over a period of at least two years. 

Noticeable changes usually begin in girls sometime between the ages of ten and sixteen, about two years earlier than boys.

There is a general spurt in growth hormone

At the same time there is increased secretion of hormones by the adrenals, the thyroid and the ovaries or testes. Under the influence of these hormones, sexual development accelerates.

In girls, the clearest indication of imminent reproductive ability is of course the onset of menstruation.

In the first months the loss of blood may be variable and the ovaries may not in fact be releasing fertile ova.

In males there is a growth and development of the larynx which results in deepening or breaking of the voice.

Young Adult

The aging process has begun

Loss of hearing begins in adolescence

Height begins to decrease at the age of 25.

Muscle strength begins to diminish at thirty - the percentage of fatty tissue increases.

Early Middle Years

The weight of the brain and the number of nerve cells in it begin to decline during a persons twenties.

Conduction velocity along nerves fibres decline steadily from the age of twenty 

So do the basal metabolic rate the strength of the grip, the cardiac output, liver weight and in men, frequency of intercourse. 

Later Middle Years

Physiologically, again between the ages of forty five and sixty in such a slow process that it often seems to pass almost unnoticed to the people concerned.

Consequently, in many cases the slow but relentless effects of ageing are mitigated. Sudden again or abrupt changes in health during these years is usually the result of serious illness, bereavement or some other major psychological or physical shock.

Old Age

The physiological changes which occur in old age are largely an accelerated continuation of those of the preceding years. The senses, particularly sight and hearing, all decline in activity.

Motor activity becomes impaired so that walking becomes slow.

Handwriting becomes spidery and shaky because the harmony between hand, eye and brain has lost some of it's precision.

Also seen in old age is a marked impairment of memory.

Loss of weight and reduction of height

Lowered resistance to disease and reduced efficiency of the circulatory and respiratory system.