ANHB1102 Study Guide - Final Guide: Prostate Cancer, Hot Flash, Mutation
3 Jun 2018
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TOPIC TEN: Growth and Ageing
Growth:
There are three mechanisms of biological growth:
1. Hyperplasia, which is increasing in number of cells
2. Hypertrophy, which is increasing the size of cells
3. Extracellular matrix, which allows us to grow is formed through products
of hyperplasia and hypertrophy
Growth never finishes; individuals always go through periods of damage and
repair.
The earliest record of an individuals height was attained in the eighteenth
century, and from this a number of variations were observed. First of all,
seasonal differences were observed, specifically that growth was greater in
spring and summer. Diurnal variation was also noted, in that height was
different in the morning compared to the night. Finally, there were also velocity
changes found, specifically a postnatal decline in growth and a pubertal peak.
Linear Growth – Conception to Adulthood:
There are two small dips in growth
from conception to adulthood – one
occurring before birth and one
occurring after birth.
In the small dip before birth, the
foetus has actually outgrown its
environment, and its growth has
exceeded the placentas ability to
keep up.
In the small dip after birth, the child
is having to deal with postnatal
adaptations, having to absorb nutrients through their own GI tract and using
their own lungs.
In most cases, the transition from the small dips before and after birth are quite
successful, with a rapid catch up growth occurring.
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Weight Velocity:
Peak weight velocity occurs
slightly later in gestation
compared to height velocity,
occurring around 30 weeks.
There is a fall in weight
velocity after birth due to
the postnatal adaptations of
the infant, but more catch
up growth occurs during
early postnatal life.
Sexual Dimorphism in Height and Weight Velocity:
Sexual dimorphism in height and weight velocity occurs during the adolescent
growth spurt. The adolescent growth spurt is occurring earlier due to an earlier
start to puberty.
For height velocity, sexual dimorphism occurs earlier in females than males, but
the net effect for males are overall greater. Sexual dimorphism in weight velocity
matches what we see in height gain, with the peak velocity achieved during the
adolescent growth spurt. The gonadal sex steroids are the major effector in fat
distribution, with the level of gonadal hormones having considerable effects of
body shape and composition, with women having a broader, wider shape of the
pelvis compared to men.
Endocrinology of Growth:
The main hormone associated with growth is growth hormone, which is secreted
by the anterior pituitary under the influence of the hypothalamus. Growth
hormone serves as an anabolic hormone, promoting protein synthesis,
hyperplasia and hypertrophy. The key targets of growth hormone are muscle
and bone, and most effects are mediated via the insulin-like growth factors
(IGFs) in the liver.
During foetal growth, growth hormone is relatively unimportant, with insulin
and IGFs being the most critical. During this stage, thyroid hormone is most
crucial for bone and muscle growth.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
There are three mechanisms of biological growth: hyperplasia, which is increasing in number of cells, hypertrophy, which is increasing the size of cells, extracellular matrix, which allows us to grow is formed through products of hyperplasia and hypertrophy. Growth never finishes; individuals always go through periods of damage and repair. The earliest record of an individual(cid:495)s height was attained in the eighteenth century, and from this a number of variations were observed. First of all, seasonal differences were observed, specifically that growth was greater in spring and summer. Diurnal variation was also noted, in that height was different in the morning compared to the night. Finally, there were also velocity changes found, specifically a postnatal decline in growth and a pubertal peak. There are two small dips in growth from conception to adulthood one occurring before birth and one occurring after birth.
