L3 Growth Changes in Humans Flashcards
What are the different processes that occur to convert the fertilized oocyte to multicellular human ? ( 6 )
- Cell division
- Cell migration
- Cell differentiation
- Cell rearrangement
- Growth
- Apoptosis
What is the effect of birth on the development ?
Birth is merely a dramatic event during development resulting in change in the environment.
From intra to extra-uterine
When most of the developmental changes are completed?
Most developmental changes are complete by the age of 25.
What are the post-natal growth periods ? (5 )
- Infancy ( first year )
- Childhood ( 2 - 12/13 years )
- Puberty (12-15 women / +1 men )
- Adolescents ( 11-19 )
- Adulthood (19 and above )
What does the First 4 weeks ( month ) of Infancy is called ?
Neonatal or new born period
What are the main features of infancy period ?
- Body grows as whole
* length increase by 1.5X
* weight increase by 3X - At the end of 1 year, 6-8 primary (deciduous) teeth will be erupted
What are the main features of childhood ?
- Primary (deciduous) teeth continue to appear
- Secondary (permanent) teeth start to replace the primary
- Active bone formation + ossification
- Prepubertal growth spurt
What are the main features of puberty?
- Development of sex characteristics.
2. Capability of sexual reproduction
When the puberty period ends in males and females ?
In females :Puberty ends by first menstrual flow.
In males : puberty ends when mature sperms are produced.
What are the main characteristics of adolescents period ?
- Ability to reproduce is fully attained.
- Rapid physical and sexual maturation.
- Extend from pubertal development until attainment of physical, mental and emotional maturity.
- General growth rate decreases at the end of this period, EXCEPT Growth of male genitalia, female breast which continue to grow
What are the main features of adulthood?
- Ossification & growth are virtually completed during early adulthood (21-25)
- Developmental changes are slow after early adulthood
What is the cause of Cellular Hyperplasia (Multiplicative growth) ?
Protein and DNA synthesis leading to increase in cell number by mitotic division
Give example of hyperplacia ?
Type- I alveolar cells during childhood
What are the determinate tissue and indeterminate tissue ? ( all of these are examples of hyperplacia )
Determinate :
- Kidney
- Neurons
- Skeletal muscles
- Cardiac muscle
- Alveoli
- Intestinal villi
Indeterminate :
- Liver acinus
- Ovarian follicles
- Thyroid follicles
- Endocrine
- Exocrine
- RBC
What is the cause of hypertrophy ( auxetic growth ) ?
Synthesis of protein and cellular materials leading to increase in cell size and growth of the tissue but without mitotic cell division.
Give example of hypertrophy ?
Neurons hypertrophy in postnatal development
What is ( what is the cause of ) Accretionary growth ?
Growth due to increase in intercellular material like the growth of bone and cartilage
What is Appositional growth ? What is an example ?
It is the addition of both ( new cells + ECM ) on the tissue by a layer of dividing cells
Example :
- the growth of bone by the external periosteum layer
What is Interstitial growth ?
increase in size by hyperplasia or hypertrophy within the tissue. Tissue grows as a whole by expanding from within.
This means that cells will proliferate and divide to inside, increasing both
- number of cells
- ECM
Give example of interstitial growth
Growth of the cartilage
What is Meristematic growth? Give examples
Growth from a tip or margins of organs which contain populations of dividing cells
Examples :
- Growth of limb buds
- Growth of fingers or nails
What is Compensatory growth ? Give examples
Regenerative growth of tissue after injury or growth to compensate the lost cells/ part of the organ
Eg.
- Regeneration of liver after injury
- Compensatory growth of kidney on the opposite side when there is an injury to one of the kidneys.
What are the different patterns of growth?
- Isometric = isogonic = Progressive proportional increase of all organs and systems with time5
- Allometric = heterogonic = It describes differences in relative rates of growth between two parts/organs of the body.
Give an example of allometric growth of the body
Growth of head, limbs, and body which have different rates
At complete maturation, head is 1/8 the body size which was 1/2 body size at beginning
How can Growth rate represented ?
by two graphic representations
- Growth curve ( for either hight or weight )
- Velocity curve
What are the types of growth curve ? and what do they mean ?
- Growth curve- Longitudinal study
- Data collected from same individual at different ages - Growth Curve- Cross-sectional study
- Data collected from different individuals as a series of averages for each month or year
What is Velocity Curve ?
It is the plot of increments ( how much increase ) in height or weight from one age to next age
How long the pre-pubertal growth spurt lasts ?
2 to 2.5 years
It start before puberty in childhood
What will happen to the hight during the spurt for both males and females ? When the hight will peak ?
- Girls gain about 16 cm in height (Peak velocity at 12 year)
- Boys gain about 20 cm in height (Peak velocity at 14 year.)
After the spurt, hight growth will decrease
Why there is a Long quiescent interval between (rapid growth immediately after birth ) and ( adolescent growth spurt) ?
It allows brain to mature before individual pass through puberty and become sexually active
What are the standard growth chart ?
Chart indicating the mean height or weight attained with age (indicated as 50th Centile )
What are the uses Standard Growth Charts ?
- to determine whether the child is growing appropriately or not.
- to predict the expected adult height and weight of a child because, in general, children maintain a fairly constant growth curve.
Which factors we must take into account when we talk about standard growth chart ?
- ethnicity
- nutritional history
- Family history
What are the structures which follow and don’t follow the growth curve?
Follow :
- bone
- muscle
- liver
- kidney
- spleen
Not follow :
- brain and head ( skull )
- lymphoid
- reproductive organs
- subcutaneous fat
What are the functions of GH in children ?
- Important for normal growth
- For muscle and bone strength
- For body fat distribution
- Control body glucose and lipids
What will happen in case of GH deficiency ?
A malfunctioning pituitary gland may not produce enough hormones for normal growth
Without enough GH, a child is likely to grow slowly and be much shorter than other children of the same age and gender.
What will happen if hypothalamus produce GHRH ?
- Pituitary will release GH
- GH will affect the liver to produce IGF-1 ( insulin like growth factor )
- IGF-1 will promote proper growth and will send -ve feedback
What are the different factors that can tightly regulate ( GHRH / somatostatin / GH / IGF-1 ) ?
- Sleep
- Exercise
- Stress
- Food intake
- Glucose level
What are the growth effects of IGF-1 ?
Directly:
- cartilage growth
Indirectly :
- bone growth
- increase blood glucose ( sugar )
What will happen in case of IGF-1 gene deletion ?
Less growth so :
- shorter
- microcephaly
- micrognathia
- mental retardation
The growth curve will be below 10th centile in the chart
What will happen in case of Increase growth hormone ?
Pituitary tumor may increase GH
if it occurs in :
- Children > gigantism
- Adults > acromegaly
What is the cause of acromegaly ?
Usually the excess GH comes from benign, or noncancerous, tumors (adenomas)on the pituitary.
Why increase GH in childhood will increase the length?
As the growth plates are not fused yet
Prolonged exposure to excess GH before the growth plates fuse causes increased growth of the long bones and thus increased height.
What are the causes of GH deficiency?
- Congenital : at birth
- Acquired : after birth due to
- brain injury
- radiation to the head
- tumor
What are the Signs of growth hormone deficiency ?
- Slowed growth in height in infants, children, or adolescents
- A young-looking face compared with other children of the same age
- A chubby body, small hands and feet, and poorly developed muscles
- Low blood glucose levels
- A very small penis (in male newborns with severe GHD)
- Delayed puberty
What is the relationship between hypothyroidism and growth ?
Thyroid hormone is very important for bone growth
Hypothyroidism is a well known cause of growth retardation
What are the effects of hypothyroidism on growth ?
- Growth retardation
- Bone age retardation
- Muscle pseudohypertrophy
- Sexual disorders
- Delayed puberty
- Precocious puberty
