Growth lecture 2

winniesmith2's version from 2017-10-20 17:34

Section 1

Question Answer
How many weeks is it from conception to birth + size changes38 weeks. 38 weeks a human infant grows from a single cell less than 100th of a millimetre in diameter at conception to a 50cm long 3.5kg infant capable of independent respiration, digestion, and movement. In next 18 yrs infant will grow to more than 3 times its length and over 20 times it weight. It will be able to communicate using a vocabulary of up to a million words, and be so sensitive to its environment that it will be able to distinguish by taste and smell over 1000 different odours, and have eyesight that can distinguish up to 10 million colours. Single cell to 35 trillion.
How do you determine the length of gestation280 days from LMP or 40 weeks (last menstrual period) or 266 days from fertilisation- 38 weeks.
When do you stop calling it an embryo and start calling it a foetus?when its recognisably human = about 12 weeks.
When do they start forced delivery of humannot until it is late 40 weeks, increase estimated fertilisation/length of gestation is incorrect.
Where do we get our empirical information on on foetal growth fromAborted material, still births and ultrasounds.
What is the issue of getting information from naturally aborted material and/or still births. If naturally aborted- probably problems with child for the body to have aborted it, not ‘normal’ growth. Still births- not sure exactly when the child stopped growing.
When did ultrasounds get put into practise1978/1979 ultrasound created/used, 1980's standard practice.
How can we use ultrasounds to measure growth Can measure different lengths and use this to predict fetal weight and head circumference. HC = head circumference , AC= abdominal circumference, FL= foetal length, HL= head length
What is one of the most important ultrasound measurements that can be made?Bi-parietal diameter (BPD). -Widest part of the head -Allows us to get the age of foetus accurately (And to predict weights) .
Describe growth rates from prenatal to adult. 20/30 LMP weeks – growth the fastest Then decelerate all the way into adult 2 interruptions – infant growth spurt and AGS Max growth in weight= Last 10 weeks of pregnancy always tired as child wants to put on weight so is growing like crazy .
Describe foetal growth - proportional changes 9 weeks, head= half length, legs 1/8, 38 weeks/birth = 25% body length, legs 1/3. Adult = head 7%, legs 1/2.
What is the average length at birth50cm.
Why does foetal growth in length decrease at the end of gestation due to the uterus putting physical constraint on size.
How early do we start to assemble what we will be like as an adultaround 2 years. When there is a child-adult correlation of 0.7 (0.7=strong correlation as squared =0.49, so you can say that half of factor B is caused by factor A). Shows good correlation from height at 2 years and adult height.
Describe parent/child correlations for height and weightTend too have a higher correlation with same sex parent for weight. Similar with height but correlation coefficient for same sex child-parent and different sex, overlap/similar from 13- 18 years.
Revisit Horse study pgs 30-35 lecture 2

Section 2

Question Answer
What is silver-russell syndrome also known asLow birthweight short stature.
What is the low birth weight cut off point2 1/2 kilos
What is the average birth weight3 1/2 kilos
What is considered a 'short stature'<3rd centile
what are the signs of silver-russell syndrome- Low birth weight <2.5kg - Short stature <3rd centile - Normal growth velocity - Thin: low Skinfolds, low fat - Asymmetrical -Characteristic facial features: small mandible, bossed forehead, low set ears, shark’s mouth, -Triangular shape; beaked nose
What is the cause of silver-russell syndrome-Genetic chromosomal abnormality. -Some patients have maternal uniparental disomy of chromosome 7, with the possibility of imprinting (e.g., inheriting 2 copies of maternal chromosome 7, with no paternal contribution).
Describe the height in those with silver-russell syndrome from 1-18 years. Normal growth rate and puberty etc, but start smaller and end up smaller.

Section 3

Question Answer
What evidence is there to suggest that growth is not a smooth processit suggest that growth actually occurs in periods of saltation and stasis. 30th October 1992 - A new model of human growth. --Michelle Lampl -Johan Veldhuis -Michael Johnson
What are the 2 hypotheses for saltatory growth 1. Cell cycle and genetic control. 2. Dual-effector model
What is the dual-effector modelgrowth hormone causes the differentiation of fibroblast cells into specific tissue types (bone, adipose, etc.); insulin-like growth factors cause the multiplication (clonal expansion) of the newly differentiated cells.
Describe the cell cycle model for explaining saltatory growthWithin the G1 phase (RNA and Protein synthesis) the cells go through a loop of non dividing resting cells (stasis) before continuing on with the rest of the cell cycle (saltation)
What are the stages of bone formation in the dual-effector model1. Proliferation by mitosis (hyperplasia). 2. Expansion of size (hypertrophy). -Proliferation may take place during stasis. -Expansion may take place during growth

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