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Body Logistics > Session 3 - Early Embryology > Flashcards

Session 3 - Early Embryology Flashcards

1
Q

What is the name of the protective coat that surrounds a mature ooctye? What is the name given to the cell formed when 1 sperm cell fertilises the oocyte?

A

Zona Pellucida

Zygote

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2
Q

Why is the clinical time of pregnancy around 2 weeks longer than that post fertilisation? As such how long is a normal time of pregnancy and how long is a normal time of gestation?

A

The clinical time of pregnancy is taken from the LMP (Last Menstrual Period) this is around 2 weeks before fertilisation.
Pregnancy is normally 40 weeks, gestation is 2 weeks less than this (as there are 2 weeks after the LMP to ovulation) so it is 38 weeks

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3
Q

What are the 3 stages of gestation and when are they?

A 
Pre-embryonic = 0-2 weeks (ends after 14days)
Embryonic = 3-8 weeks (starts on 15th day)
Foetus = 9-38 weeks
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4
Q

Where is the most common site for fertilisation in the fallopian tube?

A

It occurs is in the ampulla region. This is the middle region after the isthmus (working from the uterus, direction of sperm travel ) and before the infundibulum region just after the ovaries.

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5
Q

What point indicates the start of the embryonic stage and what is the name of this first stage? What is the significance in law?

A

The formation of the primitive streak at the start of week 3. This indicates the end of the pre-embryonic stage and the start of the embryonic stage with Gastrulation.
In law the significance of this is that it shows the start of the development of an individual.

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6
Q

What is cleavage and why does it occur?

A

Cleavage is the process where by cells divide without growth directly after fertilisation to form. They have to do this as the Zona Pellusida restricts any expansion of the cells

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7
Q

When fertilisation of the oocyte occurs in-vitro what do they look for to determine the viability of the morula?

A

The morula is determined as being viable after the 4-8 cell stage before being inserted into the uterus. This shows that there is cleavage and continued mitosis.

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8
Q

What is the difference between an ovum and an oocyte?

A

An oocyte in immature ovum

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9
Q

Define a zygote

A

A diploid cell resulting from the fusion of two haploid gametes; fertilised ovum

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10
Q

Define cleavage

A

The division of cells in the early embryo without any cellular growth

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11
Q

Define the zona pellusida

A

A glycoprotein layer surrounding the ovum and morula

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12
Q

Define the morula

A

An early stage embryo consisting of 16 cells (blastomeres) within the zona pellusida.

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13
Q

Define an ovary

A

Organ in the female reproductive system that produces an ovum

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14
Q

What are the fallopian tubes?

A

A pair of tubes along which eggs travel from the ovaries to the uterus

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15
Q

What is the uterus?

A

Ha hollow muscular organ located in the female pelvis. It is the site of gestation

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16
Q

Why is week two of the gestation called the “week of twos”?

A

Differentiation progresses and two distinct layers form.
Outer cell mass becomes: cytotrophoblasts and syncytiotrophoblasts
Inner cell mass becomes the bilaminar disk: epiblasts and hypoblasts

17
Q

Define a blastocyst

A

A structure formed in the early development of an embryo. It processes and inner cell mass developing into the embryo and an outer cell mass forming into the placenta

18
Q

What is they role of trophoblast?

A

They play a role in embryo implantation and the interaction with the decidualized (modified) endometrium they go on to form the placenta and other supporting tissues

19
Q

What is the role of the inner cell mass?

A

Also known as the embryoblasts it is what gives rise to the primordial embryo

20
Q

What is implantation?

A

This is the process in which a developing embryo, moving as a blastocyst, makes contact with the uterine wall and starts to form supporting structures for the development of the embryo

21
Q

What is the role of cytotrophoblasts?

A

These are primary there to anchor the blastocyst to the uterus

22
Q

What is the role of the syncytiotrophoblasts?

A

These are what determine which substances cross the placenta.

23
Q

What are the main stages of the embryonic stage?

A

Gastrulation, Neurulation, Segmentation, Folding

24
Q

What are the important derivatives of the ectoderm?

A

Organs and structures that maintain contact with the outside world -e.g: nervous system, epidermis

25
Q

What are the important derivatives of the mesoderm?

A

Muscle, cartilage, bone, vascular system (including the heart and vessels)
Supporting tissues

26
Q

What are the important derivatives of the endoderm?

A

Internal structures

E.g: epithelial lining of GI tract, reparatory tract, parenchyma of glands

27
Q

Give some examples of left right assymetry

A

Liver on right, stomach and spleen on right left.

L lung has 2 lobes, R lung has 3 lobes.

28
Q

What causes left-right asymmetry?

A

The action of ciliates cells at the node result in leftward flow of signalling molecules and as such there are side specific signalling cascades.

29
Q

What are the derivatives of the intermediate mesoderm?

A

Kidneys

30
Q

What are the derivatives of the somatic mesoderm?

A

Diaphragm, limb muscles

31
Q

What are the derivatives of the splanchnic mesoderm?

A

Muscles of the heart and the viscera

32
Q

What are the derivatives of the Inter embryonic coelom?

A

Body Cavities

33
Q

What can be used to determine the age of an early embryo during segmentation?

A

The formation of somites is very predictable and as such can be used to determine the age of an embryo

34
Q

Define a germ layer?

A

Each of three layers of cells that are formed in the early embryo

35
Q

What is the dermatome?

A

Area of skin which is derived from a single somite.

36
Q

What is a myotome?

A

Area of muscle which is derived from a single somite

37
Q

What is a sclerotime?

A

Area of hard tissue (bone) which is derived from a single somite

38
Q

What are the names given to the two stages of folding of the early embryo?

A

1) cephalocaudal folding

2) lateral folding

Body Logistics (12 decks)

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