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Anatomy And Physiology > Embryology > Flashcards

Embryology Flashcards

1
Q

What does embryotic development begin from?

A

A single cell
( the fertilised egg or zygote)

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2
Q

How long is a human pregnancy?

A

280 days

40 weeks

3 trimesters

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3
Q

From what weeks is the first second and third trimester?

A

1st trimester-> 0-13 (embryo)

2nd trimester->14-26 (foetus)

3rd trimester->27-40 (foetus)

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4
Q

How does the body grow?

A

Due to cells dividing through mitosis to produce two diploid (2n) cells

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5
Q

How are germ cells different to original diploid cells and why is this?

A

Germ cells have only 1 copy of each chromosome (haploid/n)

Bcus the nuclei of two germs will fuse at fertilisation to create a 2n zygote

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6
Q

How is meiosis introduced into embryology?

A

Halves the number of chromosomes in the cell to produce 4x germ cells.

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7
Q

What are PGCs and how do they function during pregnancy?

A

Primordial germ cells

Germ cells are derived from PGCs
Can multiply by mitosis prior to the beginning of meiosis

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8
Q

When does meiosis start and end for a woman?

A

Begins during foetal development, then paused after first division does not resume until puberty years later

During this pause a woman carries oocytes (eggs) that she will use

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9
Q

What is a follicle?

A

Layer of epithelial cells surrounding the egg

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10
Q

What is a mature follicle called & what does it contain?

A

Graafian follicle

contains a fluid-filled cavity called the antrum

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11
Q

When does the oocyte resume meiosis?

A

On day 13/14 of menstruation, completing meiosis I and producing a polar body, meiosis II is complete after fertilisation

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12
Q

What is the function of the follicle ruptures?

A

At ovulation to release the oocyte into the fallopian tube, this carried to womb by the flow created by beating cilia

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13
Q

What does the raptured follicle form?

A

The corpus luteum which acts as an endocrine organ, signalling to the endometrium

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14
Q

What 2 hormones are produced from the pituitary gland of the brain trigger ovulation?

A
  • follicle stimulating hormone (FSH)
  • leutenising hormone (LH)
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15
Q

What 2 hormones are released by the corpus luteum?

A

Oestrogen

Progesterone

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16
Q

What 3 anatomical regions do spermatozoa contain?

A

1) head- contains condensed nucleus and acrosome

2) midpiece- contains mitochondria

3) tail- flagellum

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17
Q

What layer do sperm push themselves through to get to the oocyte?

A

Cumulus cell layer

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18
Q

What is polyspermy ? How is it prevented?

A

Fertilisation by more than one sperm

Prevented by changed which are triggered by membrane fusion including generation of a calcium wave and release of cortical granules

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19
Q

What is the fertilised egg called?

A

Zygote

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20
Q

What happens at day 8-9 implantation mark?

A

The blastocyst becomes embedded within the wall of the endometrium

The placenta begins to develop from the trophoblast layer

21
Q

What are the two different cell types that can be seen on day 5 blastula-stage embryo?

A
  • inner cell mass
    Contains embryonic stem cells (cells from which the embryo was generated)

-trophoblast
The outer layer of cells
These calls later form in the placenta
They do not contribute to the embryo

22
Q

When does gastrulation occur?

A

Day14-21

23
Q

What 3 major events occur using gastrulation?

A

1 cells become fate-restricted (to form one of three germ layers)

2 cells become motile (there are 3 major cell movements around the embryo)

3 the embryo is patterned ( to form the major axes which determines the body plan)

24
Q

Outline the 3 germ layers produced in gastrulation and examples of where they are?

A
  • Ectoderm (outer layer) brain, nervous system, skin, hair
  • mesoderm (middle layer) muscle, bone, most internal organs
  • endoderm ( inner layer) gut, inner surface of lungs
25
Q

Where does the brain and spinal cord develop from?

A

Neural tube

26
Q

From early on, 3 morphological divisions of the brain can be seen;

A

(1) forebrain

(2) midbrain

(3) hindbrain

27
Q

What are two fundamental processes that occur during embryonic development ?

A

1) differentiation- process of mature cells with a defined function

2) morphogenesis - the acquisition of shape and form
The new cells produced must be precisely organised to form tissues and organs

28
Q

What is differentiation about?

A

Gene regulation

29
Q

How are cells organised to form tissues and organs?

A

The embryo contains patterning centres which release signals that organise and pattern the body

30
Q

When does development of tissues and organs occur?

A

During the second half of embryogenesis

31
Q

What are the 2 stages of the development of tissues and organs?

A

1- fields of precursor cells are first pattered, receive and respond signals which give the cells an identity, tells the cells where they are and where they need to be

2-by the time the embryo is a foetus the major organs and limbs have formed and the foetus resembles a small person

32
Q

What is a stem cell? And what are 2 key properties?

A

A stem cell is an undifferentiated progenitor cell

1) can replicate indefinitely in an undifferentiated state

2) under right conditions, can differentiate into one or more mature cell types

33
Q

What is potency?

A

Ability of a stem cell to differentiate into one or more different cell types

34
Q

What are the 4 levels of potency?

( in order of decreasing levels)

A

1- totipotency
2-pluripotency
3-multipoentcy
4-unipoency

35
Q

What is totipotency?

A

The zygote (fertilised egg) has the highest possible potential

The ability to differentiate into any cell both within the body and within the extra-embryonic structures needed for development

36
Q

What day is the blastula stage of development reached in humans?

A

Day 5

37
Q

What two distinct cell types does the blastula contain?

A

1) Outer layer composed of trophoblasts (these cells will go on to form the extra-embryonic structures)

2) inner layer mass containing embryonic stem cells (ESC) (these give rise to the embryo themselves)

38
Q

Why are pluripotent cells different to others?

A

They can differentiate into any cell of the embryo but cannot form extra-embryonic cell types

39
Q

Describe multipotent stem cells;

A

Have mid-range potential and can differentiate into a limited number of cell fates

Example- mesenchymal stem cells from the bone marrow

40
Q

What stem cell has the lowest potential of any stem cell?

A

Unipotent stem cells

41
Q

Where are unipotent stem cells found?

A

In adults, particularly in tissues that are continually growing (hair&skin)

42
Q

Describe how unipotent stem cells propagate;

A

Propagate indefinitely in an undifferentiated state, but then they differentiate they can only adopt a single fate

43
Q

What is lost as embryonic and foetal development proceeds?

A

Gradual loss of potency

The fertilised egg is totipotent

44
Q

What does development potential indicate?

A

What a cell could differentiate into

(they actually differentiate into is cell fate )

45
Q

What does cell fate describe?

A

The differentiated state a cell adopts at the end of development

46
Q

What is fate specification?

A

The process by which cells choose what date they will adopt

47
Q

What does determination describe in cell fate?

A

The state of being irreversibly committed to adopting a particular cell fate

48
Q

How is the potential of a stem cell differentiate into a given cell reduced during development?

A

It is reduced because certain regions of the genome are silenced

49
Q

Not ever cell..

A

Uses every gene in the genome

Anatomy And Physiology (21 decks)

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