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ISCM > DEVELOPMENT > Flashcards

DEVELOPMENT Flashcards

1
Q

what is gastrulation ?

A

It is a process by which the embryo changes from being a single layer of cells to a multilayer of cells.

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2
Q

What events happen after fertilization ?

A

The fertilised egg starts to divide (cleavage) and creates a
hollow ball of cells which undergoes the process of gastrulation. Organs begin to form (organogenesis) and then will continue to grow and refine after hatching (fetal period in humans). Metamorphosis, the process of becoming sexually
mature can be thought of as being equivalent to puberty. When mature,gametes are produced to allow the cycle to begin again

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3
Q

what is the full term in pregnancy in weeks ?

A

38 weeks counted from the last menstrual period

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4
Q

when is development counted from ?

A

from fertilization

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5
Q

What cells are affected by mutations occurring later on ? give an example

A

Somatic cells and will have no effect on subsequent generations and evolution eg DMD, brain tumour

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6
Q

what cells are affected by mutations occurring early on ? give an example

A

affects both somatic and germ cell lines and therefore the mutation can be passed on eg haemophilia

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7
Q

why are the pituitary glands called the adenohypophysis(anterior) and the neurohypophysis (posterior) ?

A 
Because the adenohypophysis
(anterior pituitary) and neurohypophysis
originate from different embryonic
structures. This explains how the
structure and function differ in the two
regions of the pituitary gland. the anterior is fromed from the mouth area and the posterior from the developing brain tissue
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8
Q

how long is pre-organogenesis and what happens

A

12-24 hours between cleavages and is the formation of 2 layers, bilaminar germ disc

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9
Q

what is the bilaminar germ disc ?

A

formed when the inner cell mass forms two layers seperated by an extracellular basement membrane. The outer one is called the epiblast and the inner one is called hypoblast go on to form the embryo

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10
Q

when are these two layers distinct in embryos

A

from day 8

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11
Q

what is a conceptus ?

A

a hollow ball of cells within an embryonic pole

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12
Q

what is an embryo ?

A

called an embryo when organ structures are present

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13
Q

what happens during gastrulation and when does it happen ?

A

organogenisis and when the embryo is 15 days. Get the basic body plan

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14
Q

what is the fetus

A

period of rapid growth and refinement eg going from a hand plate to fully formed fingers as well as cellular function.

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15
Q

define oocyte

A

sex cell that has not finished undergoing meiosis

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16
Q

define ovum

A

mature sex cell. completes meiosis on fertilization

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17
Q

define zygote

A

fertilized ovum with male and female nuclei. Two sets of information in the nucleus

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18
Q

define morula

A

ball of cells. no cell growth. hyperplasia only ( enlargement of a tissue without increasing in size )

19
Q

define compaction

A

process of creating a tight ball of cells

20
Q

define blastomere

A

individual cell that makes up the morula

21
Q

define balastocyst

A

hollow ball of cells with a thickening at one end when viewed as a cross section

22
Q

define blastocoel

A

the fluid filled hollow withing the blastocyst

23
Q

what triggers the formation of an ovum

A

triggered by fertilization and forms an ovum and a polar body

24
Q

what is the purpose of the polar body

A

damaged set of chromosomes sent to the polar body. the polar body has little cytoplasm and will apoptose (programmed cell death )

25
Q

which part of the uterine tube does fertilization take place ?

A

ampulla

26
Q

what is the zona pellucisa and till when is it present

A

it is the thick extracellular coat around the zygote and is present till it reaches the uterus

27
Q

does cell division increase the size of the cell

A

no it increases only the number of cells

28
Q

where does implantation take place and what is implanted

A

the blastocyst is implanted in the upper quadrant of the uterus

29
Q

what is the inner cell mass and when is it identifiable

A

group of cells that contribute to the embryo. It is identifiable at 4-6 days of human gestation

30
Q

what is the epiblast

A

outer layer of cells that go on to form embryonic tissue. surrounded by the amniotic cavity

31
Q

what is the hypoblast

A

primitive endoderm ( inner layer). Gives rise to extraembryonic tissue and faces the yolk sac

32
Q

functions of extraembryonic tissues

A

nourishment, protection, waste disposal

33
Q

types of extraembryonic tissue and their functions

A

amnion- protective, allows the embryo to float. prevents drying out and provides protection from mechanical damage

allantois- waste disposal/collection

chorion- blood vessels for exchange with external environment

placenta- organ with maternal and fetal blood vessels

34
Q

what are the critical periods for development and why

A

pre-organogenesis- week 2, death can occur

embryonic period- week 3-8, major malformations may occur

fetal period- week 9-38, functional defect and minor malformations

35
Q

what are the critical periods for organ system developments

A

neural- embryonic period

heart

36
Q

when does gastrulation take place

A

12-15 days

37
Q

what are the three layers in the gastrula and where they are found

A

ectoderm(outer)- skin and nervous system

mesoderm(middle)-internal organs

endoderm(inner)- internal linings eg blood vessels,gut lining

38
Q

what is the primative streak and what is its function

A

primative streak-it is a structure that forms during early stages and is like a groove. cells move through the streak to form the mesoderm and endoderm

39
Q

what happens to the cells during gastrulation

A

the epiblast cells converge on the primative streak
the individual poliferating cells move through the primative streak and displace the hypoblast to create the endoderm
later cells move through to create the mesoderm

40
Q

what is hypertrophy

A

cellular growth which creates thickened tissues as the cells grow in size

41
Q

what is hyperplasia

A

cell division which increases cell number

42
Q

how do cells know whether they are outside or inside

A

cells outside the blastocyst have contacts on 2 sides whereas cells in the inner cell mass have more contacts

43
Q

what happens during long range signalling

A

long range signals often creates gradients where cells will behave differently based on where they are on the gradient. this type of signal is a morphogen.

44
Q

what happens during short range signalling

A

cells can react to their own signals (autoregulation) or to signals from neighbouring cells. this local signalling can be inhibitory or inducing

ISCM (19 decks)

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