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22. Growth
N/A
72
Anatomy
Undergraduate 2
12/06/2012

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Term
What has happened to the market weight of steers over the past 50 years?
Definition
it has increased
Term
What has happened to feed efficiency over the past 50 years?
Definition
it has increased
Term
What has happened to the fat thickness over the past 50 years?
Definition
it has decreased so the meat is leaner
Term
What has happened to the time to market over the past 50 years?
Definition
it has decreased
Term
What does the typical growth curve look like?
Definition
like a logistical function
Term
What are the two phases shown in the typical growth curve?
Definition
the self-accelerating phase and the self-retarding phase
Term
What does the rate of growth curve look like?
Definition
a parabola
Term
What tissues are of the greatest importance in growth and development in meat animals?
Definition
bone, skeletal muscle, and adispose tissue
Term
What is the growth gradient for muscle like?
Definition
  1. start at the extremities (forelimbs and hindlimbs)
  2. move upward (chuck and round)
  3. progress forward from the rump and backwards from the withers
  4. meet at rib-loin junction
Term
With regards to postnatal growth of bone, muscle, and fat, list the order of content from lowest to highest just after birth.
Definition
fat, bone, muscle
Term
With regards to the postnatal growth of fat, muscle, and bone, list the order of content from lowest to highest at maturity.
Definition
bone, fat, muscle
Term
What is hypertrophy?
Definition
process by which cells increase in size
Term
What is hyperplasia?
Definition
growth due to increase in the number of cells
Term
What is accretion? Give examples.
Definition
growth due to the addition of material between cells; connective and scar tissue
Term
What hormone is essential for growth?
Definition
growth hormone
Term
What factors affect growth?
Definition
  • genetic determination
  • an adequate diet
  • freedom from chronic disease and stressful environmental conditions
  • normal concentrations of growth-influencing hormones
Term
What are the three main functions of growth hormone?
Definition
  • metabolic actions unrelated to growth
  • growth promoting actions on soft tissues
  • growth promoting actions on bones
Term
How does growth hormone affect metabolic functions unrelated to growth?
Definition
  • increases lipolysis (increased fatty acid in the blood)
  • conserve the glucose
Term
With regards to growth promoting actions on soft tissues, what does growth hormone do?
Definition
it causes hyperplasia and hypertrophy
Term
With regards to growth promoting factors on bones, what does growth hormone do?
Definition
  • stimulates proliferation of epiphyseal cartilage
  • stimulates osteoblast activity
  • at puberty, the epiphyseal plate is ossified (closed) by action of sex hormone
Term
How does bone grow?
Definition
it grows from the extremities, not from the middle
Term
What is the section of bone called that is on the outside of the epiphyseal plate?
Definition
epiphysis
Term
What is the section of bone called that is on te inside of the epiphyseal plate?
Definition
diaphysis
Term
What is on the very end of bones?
Definition
articular cartilage
Term
What is the epiphysis?
Definition
a rounded end of a long bone
Term
What is the epiphysis filled with?
Definition
red bone marrow, which produces erythrocytes
Term
What is the diaphysis?
Definition
the main or mid section (shaft) of a long bone
Term
What is the diaphysis made up of?
Definition
cortical bone and usually contains bone marrow and adispose tissue
Term
What is an osteoclast?
Definition
a type of bone cell that removes bone tissue by removing its mineralized matrix 
Term
What is the process that an osteoclast carries out?
Definition
bone resorption: the process of removing bone's mineralized matrix
Term
What is an osteoblast?
Definition
a mononucleate cell that is responsible for bone formation
Term
What are chondrocytes?
Definition
a connective tissue cell that occupies a lacuna withint the cartilage matrix
Term
Explain the steps that occur during bone growth.
Definition
  • within the epiphyseal plate, chondrocytes undergo cell division near the epiphyseal bone
  • older chondrocytes enlarge
  • the extracellular matrix calcifies
  • dead chondrocytes are cleared away by osteoclasts within the diaphysis
  • osteoblasts swarm up from the diaphysis and deposit bone over the persisting remnants of disintigrating cartilage 
Term
What allows long bones to grow in length?
Definition
increases in catilage cells (chondrocytes) on the outer edge of the epiphyseal plate followed by hypertrophy and calcification
Term
What causes ossification of the epiphyseal plate?
Definition
estrogen and testosterone
Term
What is growth in bone thickness from?
Definition
osteoblasts and calcification of bone on the outside of the bone in conjunction with loss of bone on the inside by osteoclasts leaving mre space for the bone marrow cavity
Term
22
Definition
Term
How does growth hormone exert its growth promoting effects?
Definition
indirectly by stimulating somatomedins (insulin like growth factors)
Term
What are the two main insulin like growth factors?
Definition
IGF-I and IGF-II
Term
Where is most og IGF-I from?
Definition
the liver
Term
How may local IGF-I act?
Definition
through paracrine action
Term
What does IGF-I production depend on?
Definition
adequate nutrition
Term
What other factors affect IGF-I production?
Definition
age related factors
Term
IGF-II is independent of ________.
Definition
growth hormone
Term
IGF-II plays an inportant role during ___________.
Definition
fetal development 
Term
IGF-II is maybe involved in _______.
Definition
muscle growth
Term
24
Definition
Term
What are the four types of fat?
Definition
  • visceral fat
  • subcutaneous fat
  • intermuscular fat
  • intramuscular fat
Term
What is visceral fat?
Definition
intra-abdominal fat
Term
What is subcutaneous fat?
Definition
fat beneath the skin
Term
What is intermuscular fat?
Definition
seam fat
Term
What is intramuscular fat?
Definition
marbling
Term
What are the four types of visceral fat?
Definition
  • mesenteric fat
  • caul fat
  • perirenal fat
  • leaf fat
Term
What is mesenteric fat?
Definition
fat deposited in a double layer of peritoneum 
Term
What is caul fat?
Definition
fatty membranes that surround internal organs
Term
What is perirenal fat?
Definition
kidney fat
Term
What is leaf fat?
Definition
the fat that lines the abdominal cavity and encloses the kidneys; used for lard production
Term
Do muscle fiber nuclei divide? Explain.
Definition
no, increases in DNA/fiber during muscle growth due to incorporation of satellite cells
Term
What are satellite cells?
Definition
cells between the myofibrils that aren't activated until the muscle is injured
Term
How does muscle fiber number affect efficiency of weight gain?
Definition
the more muscle fibers, the more efficient the animal is at gainging weight
Term
What does selection for growth affect wih regards to muscle? Explain.
Definition
muscle fiber type; more Type II B fibers 
Term
Why is more Type IIB fibers desirable?
Definition
  • larger size
  • lower protein turnover
  • greater growth efficiency
Term
What is the myoglobin content of Type II B fibers like?
Definition
low
Term
37
Definition
Term
What is another name for growth hormone?
Definition
somatotropin
Term
Where is growth hormone produced?
Definition
the anterior pituitary
Term
What is somatomedin?
Definition
a hormone produced by the liver (and other tissues) in response to GH that has a direct impact on growth at the cellular level 
Term
What is anothe rname for soamtomedin?
Definition
IGF
Term
Where is somatostatin produced?
Definition
the hypothalamus
Term
What does somatostatin inhibit?
Definition
GH
Term
Where else is somatostatin produced and what else does it do?
Definition
it is also produced by pancreatic delta cells and slows digestion
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