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320 fundamental growth and Development > AN SC 320Pre-Natal Growth and Development (lec 6-8) > Flashcards

AN SC 320Pre-Natal Growth and Development (lec 6-8) Flashcards

1
Q

lecture 6

A

Prenatal growth and development

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2
Q

Pre-natal growth

A
  • starts as son as egg divides
  • fertalization occures in fallopian tubes
  • fertalized ovum is considered an embryo after implants in uterus
  • embryo considered a fetus once there is full differentation of the tissues
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3
Q

Pre-natal growth Phases?

A

Oocyte
Blastocyst
Embryonic
Fetal

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4
Q

Oocyte

A
  • occures in fallopian tuve

- Oocyte cleavage, cytoplasim provides energy

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5
Q

Blastocyst

A

Morula changes to blastocyst

  • hyperplasic growth continues
  • blastocelic cavity forms
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6
Q

Embryonic

A

Blastocyst implanted in uterus and gasturlation and tubulation occurs

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7
Q

Fetal

A

Tissues differentiated

  • rapid differential growth
  • alot of alometric growth
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8
Q

other pre-natal growth

A
  • placental growth, grows from embryo

- uterine growth

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9
Q

Earily cell division

A

in oviduct-2-8 cells in 3 divisions
at uterus, 16 celll morula
-2 more divisions-morula change to blastocyst(64 cels)
-inner cell mass is at one cell of blastocyst from where the embryo is generated

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10
Q

formation of blastocyst

A

Morula (16 cells) → 36 cells → 64 cells → Blastocysyst

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11
Q

Blastocyst parts

A
  • Blastocele
  • Trophectoderm-(single layer of cells aroind outside)
  • Zona pellucida -around very outside, helps from implanting
  • Inner Cell Mass(at one side)
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12
Q

Shedding of the Zona pellucida

A
  • ruptures due to blastocyst growth or enzymes

- if it doesnt hatch blastocyst dies

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13
Q

ICM

A

inner cell mass

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14
Q

RL

A

Ruber’s Layer(trophectoderm cells over inner cell mass)

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15
Q

T

A

-trophecdoerms cells(shed around inner cell mass

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16
Q

H

A

-primitive endoderm

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17
Q

before and during elongation

A

before endoderm and mesoderm start to form
endoderm migrates along trophectoderm
-mesoderm grows between trophectoderm and endoderm
-mesoderm forms a cavity with half connected to trophectoderm forms chorion

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18
Q

Bovine conceptus day 14

A

Inner cell mass has now become a disc, can start to see differentiation of cells

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19
Q

Gastrulation

A
  • true differentiation occurs
  • morphogenesis
  • formation of separate endoderm, mesoderm and ectoderm
  • conceptus becomes embryo
  • placenta begins to form
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20
Q

Differentiation in 3 ares

A

Endoderm
mesoderm(sometimes)
ectoderm

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21
Q

Endoderm differentiation

A 
– Respiratory system
– Middle ear
– throat
– Esophagus
– Liver, pancreas
– Allantois
– Urinary bladder
– Primary sex cells (ova)
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22
Q

Mesoderm differentation

A 
– Head (skull, cranial and facial muscles, eye) – Skeleton
– Skeletal muscles
– Reproductive tract
– Heart
– Major blood and lymph vessels
– Kidneys
– Parietal cavity lining
– Tendons, ligaments, cartilage, adipose
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23
Q

Ectoderm differentation

A 
– Glands (mammary, sweat)
– Epithelium
– Anal canal
– Teeth enamel
– Mouth epithelium
– Nasal and olfactory nerves and epithelium – Lens of eye
– Inner ear mechanism
– Brain
– Central nervous system
– Hair, hooves, horns
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24
Q

Lecture 7

A

prenatal growth and development (2)

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25
Q

Four Stages of Implantation

A

Pre-attachment
Appostion
Adhesion(loosley attached
attachment (firmly attached)

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26
Q

Pre-attachment

A
  • Blastocyst
  • Zona pellucida is shed
  • Elongation occurs
  • IFNT is released - increase in endometrium lining
  • Conceptus lives off secretions from the endometrium
  • Endometrium produces glandular epithelium
  • Mucin in uterus prevents adhesion from occurring
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27
Q

Apposition

A
  • IFNT releases mucin making uterus better for conception
  • Positioning itself getting ready to adhere
  • Trophoblast = conceptus
  • Conceptus produecs papillae that go into GE where there is lots of nutrients
  • Conceptus increases surface so it can absorb more nutrients
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28
Q

Adheasion

A
  • Trophoblast cells change to more functional cells
  • Cells are binucleate (precursor to sincytial plaques) which are a gateway for fetus and maternal junctions
  • Increase in proteins (integrins) that connect cells together
  • Connection between conceptus cell wall on uterine cell at embryonic disc where inner cell mass was
  • Hormone change in mother
  • Increase in progesterone maintains pregnancy
  • Prevents ovulation
  • Comes from corpus luteum
  • Sustained progesterone down-regulates progesterone level
  • Loss of progesterone down regulates MUC2, down regulating mucin production
  • Implantation can occur
  • Integrins (glycolipids and glycoproteins) are a part of bonding between conceptus and endometrial lining
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29
Q

Attachment

A 
•	Early embryonic death significant because of low reproductive efficiency in farm animals
•	Embryonic death can be caused by:
o	High temperature
o	Disease
o	Poor nutrition
o	High production requirements
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30
Q

Embryo Growth

A

form somites(2nd step of differentiation, still capable of hyperplasic growth.

31
Q

The parts of somites

A
  • Scerotome
  • Dermatime
  • Myotome
32
Q

Sclerotome

A

Bone and cartilage of the vertebral column

33
Q

Dermatome

A

Under the ectoderm(epidermis) to form connective tissue dermis

34
Q

Myotome

A

forms muscles including tongue and eye muscles

-located close to neural cored

35
Q

dermomyotome

A

when myotome and dermatome differentiation isn’t clear

36
Q

Limb bud formation

A
  • Mesoderm signals ectoderm toc reate an apical ridge

* Mesoderm provides cells for muscle and bone

37
Q

limb muscle formation

A
  • Formation of muscle precursor cells in the lateral dermomyotome somite
  • Delamination and migration of precursor cells to limb bud
  • Activation of myogenic program
  • Proliferation of cells
  • Formation of dorsal and ventral muscle masses
  • Muscle differentiation
  • Muscle splitting
38
Q

Muscle regulatory Factors

A

o Transcription factors that induce differentiation of myoblasts
o Transcription factors are proteins that promote or repress the transcription of DNA to RNA
o Four main MRF’s
• Myogenic factor 5 (Myf5)
• MyoD (myogenic determination factor D)
• Muscle regulatory factor 4 (MRF4)
• Myogenin - promoter of final differentiation (occurs later to give muscle cells time to get to the limb bud)
o Bind to E-box on gene
o Myf5 annd MyoD - recruitment, migration and differentiation of pre-myoblasts
o Myogenin - produces terminal differentiation
o MRF4 - maintains terminal differentiation
• Suspension of MRF4 - stops working because it’s expecting a 2nd wave to come and it doesn’t want to differentiate too soon
• Goes beyond birth so it can maintain differentiation

39
Q

growth factors

A

Transformation growth factors

  • hepatic growth facrot(HGF) or scatter factor
  • Fibroblast growth Factor(FGF)
  • Myostatin(double muscling
  • Insulin-like Growth Factors
40
Q

Transformation growth factor

A
  • Inhibits muscle cell differentiation by slowing the proliferation of myoblasts and satellite cells
  • Inhibits MyoD and myogenin
41
Q

Hepatic growth factors

A
  • Induces formation of mesenchymal cells
  • Mediates migration of myogenic cells to limb buds
  • Hypertrophy and regeneration through satellite cells (stem cells that are reserved for injury, will only repair the number of fibres that are damaged)
  • Begins delamination and migration
42
Q

Fibroblast growth facrots

A

Inhibits differentiations and encourges proliferation

43
Q

Myostatin

A
  • Reduces cell proliferation and differentiation
  • Negative regulator of muscle mass
  • Stops proliferation (promotes differentiation)
  • Stops muscle growth and hyperplasia
44
Q

insuline-like growth factors

A
  • Proliferation (1) and differentiation (II) or myoblasts and satellite cells
  • Hypertrophy
  • Growth activator (important for hypertrophy)
45
Q

Fetal muscle growth

A 
myogenesis 
per-myoblasts
primary myofibre
secondary myofibre
epigenetic influences
46
Q

Myogenesis

A

myo=muscle gnesis=birth

47
Q

Pre-myoblasts

A

differentation into muscle cells

muscle cells are micronucleodes

48
Q

pre-myoblasts

A

mitotic stem cells -> myoblasts (post mitotic) -> (migration) myotubes -> myofibres

49
Q

Primary myofibre

A

(muscle cell) larger, originated from first wave

50
Q

secondary myofibre

A 
from 2nd migration of muscle stem cells
surround primaries  (limited by number of primary)
-more primary=larger animal
51
Q

epigenetic incluences

A

Tse(2005) found that uterine crowding reduced myogenin expression in crowded piglets

52
Q

myogenin

A

promotes myoblast differentiation

53
Q

Fetal growth

A

Crowding occures in highly prolific sows
selection for uterine capacity rather than prolificacy
-size at birth important

54
Q

post implantation

A 
Tortion
flexure
tissues and organs differentiate
differentation begins at head
waves of growth from head to extremities
55
Q

torsion

A

embryo is twisted to lie on its side

56
Q

flexure

A

bending of the embryo

-embryo flexes so ventrial profile concave: dorasl profile convex

57
Q

Types of Placenta

A

Diffues
Cotyledonary
Discoid
Zonary

58
Q

Diffuse

A

Placenta is attached to uterus all the way around (horse and pigs)

59
Q

Cotyledonary

A

Discrete large specially formed attachments to the uterus(ruminants)

60
Q

Discoid

A

one major attachment to the uterine membrane (primates, rodents)

61
Q

Zonary

A

Complex or incomplete band of attachment spots (dogs, cats, bears, elephants)

62
Q

Feto-maternal junction

A

Placentome- defines feto-maternal junction

-coytyldeon emerges from the placenta that is attached to cornuncle on mother

63
Q

placentia differentiation

A

Amnion
allantois
yolk sac
chorion

64
Q

Amnion

A
  • encloses fetus in fluid-filled cavity

- derived from inner cell mass

65
Q

allantois

A

derived from hind gut

-connects fetal and placental circulations

66
Q

yolk sac

A

derived from endoderm

soure of nutrients before fetal?placental circulation established

67
Q

Chorion

A

Trophoblastic capsule and surrounds fetus and other membranes
-fuses with allantois

68
Q

Placental and fetal growth

A

o Rapid growth for placenta initially, but tapers off as fetus grows.
o Placenta has to develop faster than the embryo
o Affected by similar things
• Maternal nutrition/maturity - important in animals that have litters
• Number of embryos/fetuses
• Steroid and growth hormone profiles
• Insulin-like Growth Factor (IGF 1) - crowded
o Placental growth positively correlated with that of the fetus

69
Q

uterine growth during pregnancy

A

o Stretch induced hyperplasia of smooth muscle fibres
o Last two thirds of pregnancy hypertrophy of smooth muscle fibres
o Hyperplasic growth only in liver, uterus, and mammary glands

70
Q

size at birth

A 
Determined by:
•	Maternal nutrition (late gestation - severe) (Has to be very severe restriction in cows)
•	Sex of offspring
•	Maternal age
•	Number of offspring
•	Maternal Size
71
Q

Maternal nutrition and calf growth

A

o Low nutrition during pregnancy depresses
• Birth weight
• Birth to weaning average daily gain
• Weaning weight
o Low birth weight calves can be high weaning weights if good maternal nutrition
o Calves light at weaning are light at slaughter as well - no time for them to catch up

72
Q

embryo exchange

A

fetal genotype interacts with maternal uterine environment

-growth appeared to be restricted by placent size and placentome weight

73
Q

regulation of mammalian fetal growth

A

o Production consequences of dam over-nutrition
• ‘Flushing’ in sheep
• Increasing energy intake prior to estrus to increase rate of ovulation rate
• Actually increases embryo/fetal mortality (early pregnancy) but increase muscle mass in embryos
• Embryos that survive have potential for improved muscle growth
• ‘Flushing’ recommended for ewes
• More embryos released, most robust survived, have best babies

74
Q

form and function at birth

A

o Becomes apparent late gestation
o Phylogeny - development of fetus to suit its birth environment
o Ruminants do not ruminate
o Herbivores are ambulatory - well developed legs
o Carnivores have fur and subcutaneous fat
o Marsupials (kangaroos) have over-developed front paws/claws to crawl to nipple in pouch
o Hair coat thickness ready for winter/summer
o Caused by daylength, indicates what kind of coat the calf should have

320 fundamental growth and Development (3 decks)

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