Growth and Development

what is growth

expanison of tissues

how is growth expressed

as per unit of measure over time

what type of growth in occurs postnatally

hypertrophic

what is hyperplasia

increase in number of cells

what is the result of hyperplasia

near exponential growth of cells

what is the main component of prenatal growth

hyperplasia

what happens during hypertrophy

cells increase in size from anabolic activity

what does hypertrophy result in

linear like whole body growth

what is a major component of postnatal growth

hypertrophy

what happens during positive growth

growth is greater than break down (anabolism>catabolism)

what is true growth

increase in structure tissues

what is another name for true growth

fat free growth

what is fat accumulation

aggregate increase of adipose tissue that rapidly increases during postnatal phase 4

what is development

continual progression toward higher tissue complexity

what is reversible growth

postitive growth followed by negative growth

what type of growth would we see during pregnancy/lactation

reversible growth

what type of growth would we see during dieting

reversible growth

what type of growth would we see during sickness/illness/injury

reversible growth

where does reversible growth occur

in adipose tissue

what is irreversible growth

tissues that can’t function with negative growth

what is negative growth

situations in which catabolism is greater than anabolism

what type of growth would we see during weaning

negative growth

what type of growth would we see during reducing plane of nutrition

negative growth

what type of growth would we see during lactation

negative growth

what type of growth would we see during breeding season

negative growth

what is lag phase critical to

determining absolute amount of growth

what causes lag phases

stressors

what is compensatory growth

rebound growth after a lag phase

what is the most ideal type of compensatory growth

recovering weight for age

what is the most typical type of compensatory growth

extending growing period

what is growth stunting a result of

nutrient restricting and critical time combination

why is growth stunting after weaning so bad

that is the critical time for tissue development

what changes first of the skeletal and body areas

the head

what changes second of the skeletal and body areas

distal limbs

what changes third of the skeletal and body areas

shoulder

what changes fourth of the skeletal and body areas

hind quarter

what changes fifth of the skeletal and body areas

rib and loin

what tissue develops first

nervous tissue

what tissue develops second

vital organs

what tissue develops third

bone

what tissue develops fourth

muscle

what tissue develops fifth

fat

what are carcass components

bone muscle fat

what are non carcass components

nervous tissue, most organs

what grows faster: muscle or bone

muscle

when does the muscle to bone ratio increase

as animals become older and heavier during primary growth phase

when does the rate of fat deposition increase

it become rapid past the inflection point on animals growth curve

what are the correlation between mature size and

daily gain, time to reach mature size weights at immature ages

what is different about larger animals growth rate

it is faster but takes longer to approach mature wight

what is chronological age

actual number of age

what is physiological. age

stage of development based on physical or chemical development such as height weight composition puberty etc

when does 15% of total growth occur

phase 1

when does nerual tissue have a faster rate of growth

phase 1

when does 75% of. total growth occur

by end of phase 2

when do organs and skeletal bone growth near completion

by the end of phase 2

when does muscle growth begin to ramp up

by the end of phase 2

when does puberty occur

by the end of phase 2

when does 80-90% of total growth occur

by the end of phase 3

when does adipose tissue production begin to ramp up

by the end of phase 3

why does stunting occur

nutritional deficiencies cause animals to break down vital cells for growth to sustain life and the break down of these cells can not be undone

what type of fat develops first

internal

what type of fat develops second

intermusclar

what type of fat develops third

subcutaneous

what type of fat develops last

intramuscular

what is physical composition

relative porportion of muscle fat and bone resulting from form change of differential growth

what makes up chemical composition

water crude fat protein ash

why is shape, apperance and composition not static

it changes from day to day

what carcass component grows at high rates

fat

what is the composition of lean muscle

70-75% water, 20-25% protein, 1-12/14% fat

what is the composition of subcut fat

10-40% water, <12% protein, 40-60/75% fat

what is chemical maturity

when a fat free body protein/ash concentration plateaus

when does protein acceleration plateau

maturity or mature body size

what is body composition influenced by

rate of gain

why to old cows have a lower dressing percentage

metabolic changes, expanded GI tract, adipose and skeletal muscle may be depleted

what is k is Huxleys unequal growth equation

growth ratio or growth coefficient

what does k>1 mean

tissue is growing faster than whole, but later developing

what does k=1 mean

growing at same rate as whole

what does k<1 mean

growing slower than whole, but earlier developing

what is a totipotent stem cell

it can develop into any type of cell including placenta and germ cell layer

what is a pluripotent stem cell

embryonic can develop into most cells

what is a multipotent stem cells

can development into secialized cells; exist in embryonic and adult phases

what part of the germ embryonic layers is the area of muscle development

the mesoderm

when does the process of cellular differentiation occur

when multipotent stem cells give rise to muscle precursor cells

what are somite patterning

dorsal portion of somite differentates into dermomytome

what do somites eventually become

skeleton, muscles

what happens with out pax 3

there is no limb development

what do multipotent stem cells differentiate into

MPC’s in the somite via transcription factors

what does the MPC’s expression of Pax3/Pax 7 lead to

proliferation or differentiation

what plays a role in attracting MPC’s to the limb bud

hepatocyte growth factor and C-Met receptor

what happens after the MPC migrates to the limb bud

Pax 3 expression decreases and myogenic regulatory factors expression increase

What are the MRFs needed for functional muscle

MyoD, MyF5, Mrf4, myogenin

what does the expression of MyoD and MyF5 play a key role in

conversion of MPCs to committed myoblasts

what do myoD and myf5 aid in

myoblasts being able to be synthesize mysoin and actin

what does the expression of myogenin do

fusing and formation of myotubes

what are myogenin and mrf4 necessary for

to cause cascade of event/protein synthesis for fusion and development myotube

what can a defect in myogenin cause

myoblasts being present but no final development of skeletal muscle

what does myogenin expression allow

myoblasts to form into primary and secondary myotubes

after myogenin expression what is a myotube

mutlinucleated, can mature into a muscle fiber, sythesize additional myofibrillar proteins into myofibril assembley, no divison occur

what is double muscling

when there is a struggle to regulate myoblasts resulting in more individual muscle cells

what signals somite patterning

the notocord through broad signalling pathways