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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

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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
Four Stages of Implantation
Pre-attachment Appostion Adhesion(loosley attached attachment (firmly attached)
26
Pre-attachment
* 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
27
Apposition
* 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
28
Adheasion
* 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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Attachment
``` • 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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Embryo Growth
form somites(2nd step of differentiation, still capable of hyperplasic growth.
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The parts of somites
- Scerotome - Dermatime - Myotome
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Sclerotome
Bone and cartilage of the vertebral column
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Dermatome
Under the ectoderm(epidermis) to form connective tissue dermis
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Myotome
forms muscles including tongue and eye muscles | -located close to neural cored
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dermomyotome
when myotome and dermatome differentiation isn't clear
36
Limb bud formation
* Mesoderm signals ectoderm toc reate an apical ridge | * Mesoderm provides cells for muscle and bone
37
limb muscle formation
* 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
Muscle regulatory Factors
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
growth factors
Transformation growth factors - hepatic growth facrot(HGF) or scatter factor - Fibroblast growth Factor(FGF) - Myostatin(double muscling - Insulin-like Growth Factors
40
Transformation growth factor
* Inhibits muscle cell differentiation by slowing the proliferation of myoblasts and satellite cells * Inhibits MyoD and myogenin
41
Hepatic growth factors
* 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
Fibroblast growth facrots
Inhibits differentiations and encourges proliferation
43
Myostatin
* Reduces cell proliferation and differentiation * Negative regulator of muscle mass * Stops proliferation (promotes differentiation) * Stops muscle growth and hyperplasia
44
insuline-like growth factors
* Proliferation (1) and differentiation (II) or myoblasts and satellite cells * Hypertrophy * Growth activator (important for hypertrophy)
45
Fetal muscle growth
``` myogenesis per-myoblasts primary myofibre secondary myofibre epigenetic influences ```
46
Myogenesis
myo=muscle gnesis=birth
47
Pre-myoblasts
differentation into muscle cells | muscle cells are micronucleodes
48
pre-myoblasts
mitotic stem cells -> myoblasts (post mitotic) -> (migration) myotubes -> myofibres
49
Primary myofibre
(muscle cell) larger, originated from first wave
50
secondary myofibre
``` from 2nd migration of muscle stem cells surround primaries (limited by number of primary) -more primary=larger animal ```
51
epigenetic incluences
Tse(2005) found that uterine crowding reduced myogenin expression in crowded piglets
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myogenin
promotes myoblast differentiation
53
Fetal growth
Crowding occures in highly prolific sows selection for uterine capacity rather than prolificacy -size at birth important
54
post implantation
``` Tortion flexure tissues and organs differentiate differentation begins at head waves of growth from head to extremities ```
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torsion
embryo is twisted to lie on its side
56
flexure
bending of the embryo | -embryo flexes so ventrial profile concave: dorasl profile convex
57
Types of Placenta
Diffues Cotyledonary Discoid Zonary
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Diffuse
Placenta is attached to uterus all the way around (horse and pigs)
59
Cotyledonary
Discrete large specially formed attachments to the uterus(ruminants)
60
Discoid
one major attachment to the uterine membrane (primates, rodents)
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Zonary
Complex or incomplete band of attachment spots (dogs, cats, bears, elephants)
62
Feto-maternal junction
Placentome- defines feto-maternal junction | -coytyldeon emerges from the placenta that is attached to cornuncle on mother
63
placentia differentiation
Amnion allantois yolk sac chorion
64
Amnion
- encloses fetus in fluid-filled cavity | - derived from inner cell mass
65
allantois
derived from hind gut | -connects fetal and placental circulations
66
yolk sac
derived from endoderm | soure of nutrients before fetal?placental circulation established
67
Chorion
Trophoblastic capsule and surrounds fetus and other membranes -fuses with allantois
68
Placental and fetal growth
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
uterine growth during pregnancy
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
size at birth
``` 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 ```
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Maternal nutrition and calf growth
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
embryo exchange
fetal genotype interacts with maternal uterine environment | -growth appeared to be restricted by placent size and placentome weight
73
regulation of mammalian fetal growth
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
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form and function at birth
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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