embryology

Question 1

what is morphogenesis?

Answer 1

shape formation of tissues, organs and organisms

Question 2

what processes determine shape?

Answer 2

growth
differentiation
motility
induction- interaction between cells apoptosis

Question 3

what are one of the two states that cellls exist in during the early embryo stage

Answer 3

-epithelial cells: tightly connected in sheets or tubes
-mesenchymal cells: unconnected and operate as independent units

Question 4

what is induction? how is it achieved? what is it often dependent on?

Answer 4

-the influence of once cell or tissue (inducer) on the developmental fate of an adjacent cell or tissue (responder)
-achieved by the diffusion of a chemical signal to nearby tissue
-often dependent on previous interactions that have primed the target tissue

Question 5

what is the embryonic period?

Answer 5

the moment from fertilisation top the end of week 8 of development

Question 6

what is the foetal period?

Answer 6

week 9 to week 36 of development

Question 7

what happens during the first stage of fertilisation?

Answer 7

1. sperm binds to the zona pellucida and releases digestive enzymes
   2.the sperm fuses with the plasma membrane
2. this triggers the egg activation process
3. cell cycle resumes
4. egg metabolism is activated
5. polyspermy is prevented

Question 8

what happens at at Carnegie stage 1

Answer 8

you have a single celled zygote being a fertilised oocyte

Question 9

how many genes does mitchondrial dna encode? what are some diseases that a mutation of some of these can cause?

Answer 9

37
-motor neuron disease
-parkinson’s
-neuropathy, ataxia, retinitis pigmentosa and ptosis (NARP syndrome)
-leber’s optic atrophy/ leber’s hereditary optic neuropathy (LHON)

Question 10

what is LHON caused by and what is the sequence of symptoms?

Answer 10

caused by mutations in the mitochondrial DNA coding a subunit of enzyme NADH
1. onset in young adulthood
2. blurring of central vision
3. desaturation of colour
4. central vision deteriorates to counting fingers in 80%
5. optic atrophy
6. permenant large scotoma

Question 11

what is compaction?

Answer 11

where the 8 cell stage zygote cells become compacted so expression of cadherins and formation of adhering junctions

Question 12

describe when does cavitation and blastocyst formation occur?

Answer 12

at the 16 cell stage a fluid filled cavity being a blastocoel is formed within the ball of cells by the action of sodium pumps forming a blastocyst

Question 13

what does the trophoblast form?

Answer 13

the foetal part of placenta and other extraembryonic tissue

Question 14

what happens at Carnegie stage 3?

Answer 14

the blastocyst hatches from the zona pellucida shell

Question 15

what day does implantation start and when is it complete?

Answer 15

starts at day 5 to 6 , its complete by approx. day 12

Question 16

where are totipotent stem cells from and what do they do?

Answer 16

in the morula of the embryo and can give rise to every cell in the body and form an entire organism

Question 17

where are pluripotent stem cells from and what do they do?

Answer 17

in the inner cell mass of a blastocyst and can generate virtually all cell types apart from the placenta

Question 18

where are multipotent stem cells from and what do they do?

Answer 18

found at specific sites as they are adult stem cells/ progenitor cells, they can only give rise to a limited number of cell types

Question 19

what can iPSCs be used for?

Answer 19

treatment of retinal degenerative diseases

Question 20

how has retinal stem cell transplant been demonstrated?

Answer 20

retinal stem cells from the ciliary margin of human donors were transplanted into the mouse retina and some transplanted cells differentiated into photoreceptors and others into RPE cells

Question 21

what happens at week 2 of embryonic development?

Answer 21

-completion of implantation
-formation of bilaminar germ disc

Question 22

how does the bilaminar germ disc form?

Answer 22

the inner cell mas divides to form
-epiblast which divides top line aminotic cavity and form all tissues in embryp
-hypoblast likes blastocoel and gives rise to the yolk sac

Question 23

what happens at week 3 of embryo development?

Answer 23

gastrulation and then neurulation

Question 24

what is the first sign of gastrulation? what is it? what does it establish?

Answer 24

-the formation of the primitive streak
-its where the epiblast cells ingress forming a furrow at the tail end of the embryonic disk
-the streak establishes the longitudinal axis of bilateral symmetry in the embryo

Question 25

what is the process of gastrulation?

Answer 25

-gastrula and blastula are formed
-2 layer embryo is converted into a 3 layer
-the 3 primary germ layers are formed:
ectoderm e.g. CNS, epidermis, endoderm e.g. lung, thyroid, mesoderm e.g. heart, muscle

Question 26

what does neurulation begin with?what is it? What does this do?

Answer 26

formation of the notochord which is a flexible rod
it induces the formation of the CNS by signalling to the ectoderm layer above it to form the neural plate

Question 27

when does neurulation occur?

Answer 27

a bit after gastrulation while it is still occuring

Question 28

what is neuralation?

Answer 28

the folding process that forms the neural tube at which stage the embryo is referred to as the neurula

Question 29

give the process of neuralation

Answer 29

1. formation of notochord
2. formation of the neural plate,
3. formation of the neural tube
4. closure of the neuropores where it ends at day 23-24
5. leads to the formation of brain and spinal cord
6. leads to neurocrest formation

Question 30

where do the neural crest cells originate and where do they end up?

Answer 30

they originate from ectoderm at the top of the neural tube and then migrate extensively

Question 31

What is the embryonic origin of the corneal epithelia and stroma?

Answer 31

-neural crest
-surface ectoderm

Question 32

which parts of the eye and adnexa are formed from the mesoderm?

Answer 32

the retina

Question 33

which parts of the eye are derived from the neural cres?

Answer 33

-corneal endothelium
-choroidal melanocytes
-corneal stroma

Question 34

from which part of ectoderm are the retinal neurons and retinal pigment epithelium originate from?

Answer 34

-the neural tube
-the neural ectoderm

Question 35

What stages of embryonic development does the zona pellucida surround the dividing cells of an early embryo?

Answer 35

-morula
-initial cleavage of the zygote

Question 36

what parts of the eye and adnexa are formed from the mesoderm?

Answer 36

-sclera
-blood vessels
-ciliary muscles
-bones of the orbit