Human Development

Human Growth Curves

A human growth curve shows the changes in a measurable characteristic (body mass, height) with age.

Typically four stages can be seen:

1. Rapid growth between birth and 1 year

2. A slower rate of growth between ages 3 and puberty

3. A rapid growth rate during puberty (which occurs between 10 and 14 years)

4. Continued slow growth following puberty and into early adulthood

Changes in proportion of body parts

At birth the proportions of the various body parts in humans are markedly different from those in an adult.

The changes take place over the course of approximately the first 16 years (i.e. adult proportions have been attained by the age of 16)

Question Study a diagram comparing the body shapes of a male over the first 16 years of life. State what changes take place and suggest reasons for each

"Homer: Old people don't need companionship. They need to be isolated and studied so it can be determined what nutrients they have that might be extracted for our personal use."

Effects of ageing on the skeletal system - osteoarthritis and osteoporosis

Osteoarthritis and osteoporosis are disorders of the skeletal system which are common in older age

Osteoarthritis

Bones which meet at joints have a layer of cartilage protecting the end of the bone from damage due to friction

Image from the Department of Health website Prodigy

With age this cartilage may degenerate and become susceptible to friction. The cartilage becomes worn away and eventually the underlying bone becomes exposed. This results in joint pain and reduced movement - the symptoms of osteoarthritis.

Osteoporosis

With age bones may also lose density

Osteoporotic bone - note the much larger spaces between the network of bone

These diagrams are taken from the website of a British osteoporosis charity; the National Osteoporosis Society

Bone is a dynamic tissue - it is constantly being broken down and reformed. Two types of cell are involved: osteoblasts (which form new bone) and osteoclasts (which break bone down)

With age the osteoblasts tend to function less well while the osteoclasts continue to destroy bone at the same rate as before with the net result that bone mass and density decrease

The result of osteoporosis is the bones have a greater tendency to fracture, an event commonly seen in the hip. There is often also curvature of the spine, back pain and weight loss.

Osteoporosis is most common in women because the hormones oestrogen and progesterone act to maintain the function of osteoblasts and the level of these hormones fall following the menopause. HRT (the replacement of these ovarian hormones) can prevent osteoporosis

Effects of ageing on the cardiovascular and reproductive systems - menopause and HRT

Atherosclerosis is a disorder of the blood vessels which is related to age.

Ingested fats collect in the arteries (sometimes called "furring of the arteries") and reduces the diameter of the lumen of the vessel. This reduces the flow of blood leading to the problems associated with the disorder.

The female reproductive capacity reduces later in life and, between 45 and 60 years, menstruation and ovulation cease; an event known as the menopause. With the end of ovulation the levels of the ovarian hormones, oestrogen and progesterone, also fall. By contrast the pituitary hormones are still produced and, with the removal of inhibition by the ovarian hormones, actually increase in level.

These changes cause a number of symptoms including hot flushes (a disturbance of temperature control) and mood swings.

The loss of oestrogen can lead to osteoporosis.

HRT, the replacement of oestrogen and progesterone, can prevent the onset of the menopause and can prevent osteoporosis

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