BIOL 2020U Lecture Notes - Anorexia Nervosa, Menarche, Seminiferous Tubule

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29 Jan 2013
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Longitudinal Study
Measures same person at regular intervals over a long period of time
Accurate picture of individual growth (+)
Measurements taken at different times can be compared
Not suitable for an investigation (-)
People leaf study area/lose interest in being involved in investigation
Migration/death
Takes a long time to see a pattern/conclusion
Relatives rates of growth of tissues and organs from birth to
adulthood
[GRAPH] Different parts of the body grow at different rates
o Head and brain develop first → being ≈90% of its adult size by the age of 5
Before growth of bones and muscles in limbs
Thus, results in a change in body proportion
o Reproductive system develops latest → remains below ≈20% until puberty
o Lymphoid tissues (appendix, spleen, thymus gland) reach max size before puberty
→ size is
o reduced to its adult size after puberty → reduction in size caused by sex hormones
o Curve of the whole body is similar to an ABSOLUTE GROWTH GRAPH as
height is an
o indicator of general body size
Different growth rates result in changes in shape during embryological and post-natal
growth
Puberty
Physical And Endocrine Changes Associated With Puberty
Growth spurt occurs earlier in girls but is larger in boys
Sex hormones (testosterone; oestrogen + progesterone) cause
o Development of internal reproductive organs and 2° sexual characteristics
o Increase activity of sweat and sebaceous glands
Blocked sebaceous glands cause acne
Changes the relative amounts of protein and fat
o Total body mass : body fat ratio is lower in boys than in girls
Testosterone causes greater growth of muscles
Oestrogen causes an accumulation of fat in the body
o Menstrual cycle in females relates to the proportion of fat to muscle
Testosterone stimulates growth of cartilage in thorax, pectoral girdle → shoulders expand
Oestrogen stimulates growth of cartilage in pelvic → hips expand
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