Everything Life Sciences Grade 10

FACT

WATCH:Summary
of the workings of
the muscle:
See video:
SHORTCODEat
http://www.everythingscience.co.za

FACT
Osteoporosis is
derived from the
Greek words for
bone (ostoun), and
pore (poros). It is
common in older
people, especially
women.

FACT
Osteoporosis is
common in older
women whose
oestrogen levels
drop after
menopause.
Oestrogen usually
suppresses
osteoclast activity
(bone resorption).
When oestogen
levels drop, the
activity of
osteoclasts is no
longer inhibited and
bone breakdown
exceeds bone
formation. This
results in an overall
loss of bone mass.

Figure 7.22: Diagram showing a sarcomere made up up thick and thin filament that slide past each

other to enable muscle contraction.

7.7 Diseases DUMMY

As a result of wear-and-tear over time and due to lack of proper nutrition, individuals can

develop bone problems. Common bone problems include rickets, osteoporosis and arthritis.

Rickets

Rickets is a disease that is most commonly caused by a lack of vitamin D, however it can also

be caused by deficiencies in phosphorous or calcium. Deficiencies in these key nutrients

results in a softening of the bone tissue, leading to fractures and bone deformities in children.

Rickets is a widespread childhood disease in many developing countries.

Figure 7.23: The diagram shows the difference between a normal patient and a rickets patient.

Osteoporosis

Bones are constantly being broken down by osteoclasts and built up by osteoblasts. When

the process of breakdown and deposition are evenly matched bone mass is maintained.

However, when there is a shortage of calcium in the body or when a bone is inactive (e.g leg

in plaster or immobilised), calcium is withdrawn from the bone for use in other parts of the

body. This results in an increased breakdown of bone tissue without an increase in deposit

of new bone byosteoblasts. Excessive breakdown without new bone deposition results in

the development of holes/pores in the bone (hence the name of the disease). A decrease in

bone density makes the bone weak and prone to fractures. The most typical fractures are of

the spine, wrist and hip.

214 7.7. Diseases