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ANAT1003 > Cleavage > Flashcards

Cleavage Flashcards

1
Q

During cleavage, the egg size increases as cells multiply. True or false?

A

False. The size remains the same but the cell numbers multiply until normal somatic cell size is reached.

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2
Q

In mammals, a ball of cells with a fluid filled cavity is called:

A

blastocyst

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3
Q

production of mature eggs and sperm. What process is this?

A

gametogenesis

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4
Q

In meiosis, cell division produces gametes with how many sets of chromosomes? haploid or diploid?

A

haploid

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5
Q

In males, meiotic divisions produce how many spermatozoa？

A

4

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6
Q

the sperm lose its cytoplasm when matured. true or false

A

true

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7
Q

The head of the sperm contains:

A

haploid nucleus,
centriole
acrosome

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8
Q

Behind the head is the mid piece, which connects the head and the tail. It is responsible for powering movement. What are the two main components of the mid piece?

A

sperm motor–axoneme

mitochondria

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9
Q

The sperm moves by its single flagellum, which contains a substance called?

A

tubulin

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10
Q

Spermatogenesis starts when the boy is born. True or false?

A

false. it begins after puberty and continues through life

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11
Q

How many days does it take to produce mature sperm?

A

64 days

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12
Q

In western societies, how much sperm does an average man ejaculate?

A

20-40 million sperm per ml

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13
Q

How much sperm ejaculated is considered abnormal and would result in reduced fertility?

A

15 million per ml or less

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14
Q

where in the female reproductive tract does fertilization take place?

A

fallopian tubes

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15
Q

In females, meiotic divisions are unequal; this results one large ovums and how many polar bodies? And in the small cellular fragments of these polar bodies, what do they contain?

A

two polar bodies

discarded chromosomes

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16
Q

Meiosis of the ovary begins before birth, during development. True or false

A

True

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17
Q

At puberty, how much oocytes would be left in the female?

A

40,000

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18
Q

Which meiotic phase are the oocytes suspended at before puberty is reached?

A

prophase I

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19
Q

The oocytes are held until fertilized in which meiotic phase?

A

Metaphase II

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20
Q

A small number of oocytes are released by the ovary during each menstrual cycle and wafted into which part of the fallopian tubes?

A

ampulla

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21
Q

The egg is surrounded by a layer of membrane and somatic cells. What are they called?

A

zona pellucida; granulosa cells

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22
Q

Membrane bound vesicles beneath the plasma membrane of the egg are called the:

A

cortical granules

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23
Q

What is parthenogenesis?

A

development of egg without fertilization. Observed in plants and some invertebrates and some reptiles. Although development is usually abnormal.

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24
Q

What are hydatidiform moles?

A

similar to andromorphic embryos in mice and are either diploid with only male chromosomes (complete hydatidiform mole) or triploid with two copies of male chromosomes and a single copy of female chromosomes (partial hydatidiform mole). In other words YY or XYY

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25
Q

Successful development of the human embryo requires both male and female chromosomes. This is called:

A

genomic imprinting.

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26
Q

Describe genomic imprinting

A

When histones and DNA are methylated during gametogenesis and some genes are inactivated ( non-Mendelism called epigenetics). Some genes are inactivated in the female eggs and some in the male sperm. Thus only when they fuse, the embryo is normal.

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27
Q

Name one genetic disease linked with faulty genomic imprinting.

A

Angleman syndrome

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28
Q

When the sperm first reach the egg, they must go through two layers of cells. What are they?

A

granulosa cells and somatic follicle cells

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29
Q

After going through the two layers of cells in the ovary, which layer do they fuse with?

A

zona pellucida

30
Q

The membrane zona pellucida contains a species-specific protein, what is it called? What will happen if the membrane lacks this protein?

A

ZP3

become infertile

31
Q

Contact by the sperm and zona pellucida induces what reaction?

A

acrosome reaction

32
Q

What does the acrosome reaction do?

A

enzymes in the acrosome is released and digest a hole in the plasma membrane so that sperm can penetrate the zona pellucida

33
Q

The fusion of sperm and egg causes a series of reactions. Briefly state these reactions:

A
  • causes a localized increase of calcium in the cytosol that quickly spreads throughout the egg.
  • calcium increase causes cortical granules to fuse with the plasma membrane and it becomes hard so that no sperm can come in. This is the cortical reaction.
  • cortical granules release contents into the extracellular space, modify sperm receptors ZP3 so that sperm can no longer bind to them.
34
Q

What is polyspermy

A

when many sperm fuse with one egg.

35
Q

Describe what happens during meiotic divisions in the fertilized egg.

A
  • sperm fuses with egg, causes egg to complete meiosis and generate both the haploid female pronucleus and second polar
  • generate a diploid nucleus from meiosis
  • mitotic divisions occur immediately after this
  • cell does not increase in size; the blastomeres becoming smaller in each division so that cells are the normal size.
36
Q

What are cleavage divisions then?

A

embryonic cell divisions that are not accompanied by growth

37
Q

The blastomeres undergo a sudden compaction at how many cell stage?

A

32

38
Q

What is the blastocyst?

A

a fluid filled cavity within the embryo

39
Q

The blastocyst has an outer layer of membrane called:

and a small clump of inner cells called:

A

trophoblast

Inner cell mass

40
Q

The trophoblast will form which tissue of the placenta?

A

chorionic tissue

41
Q

The Inner cell mass will form:

A 
the foetus and two extraembyonic membranes
extraembryonic endoderm, extraembyonic mesoderm and
amniotic membrane (extraembryonic ectoderm)
42
Q

The extraembyonic endoderm is also called:

A

Heuser’s membrane

43
Q

The extraembryonic mesoderm forms the:

A

vasculature of the umbilical cord and placenta

44
Q

All of the extraembryonic tissues will be discarded at birth. what are these called?

A

decidua

45
Q

Which part of the fertilized cell will form the three germ layers?

A

ICM

46
Q

When two eggs are ovulated and fertilized at the same time, what type of twins would form?

A

dizygotic twins

47
Q

70% of monozygotic twins will share a common tissue but separate ICM. what is the common tissue?

A

placenta

48
Q

About less than 1% of twins share the same chorion and same amniotic membrane. These twins are likely to be:

A

conjoined twins

49
Q

How is tetragametic chimera formed

A

when two eggs of unidentical genes fuse together to form a single embryo

50
Q

During pre-implantation diagnosis, which set of cells can be taken out and tested for genetic defects?

A

blastomeres

51
Q

what is implantation?

A

blastocyst burrows into the mothers uterine wall, where it can
establish close contact with the mothers blood supply

52
Q

Why are ectopic pregnancies dangerous?

A

They implant somewhere else such as the fallopian tubes, ovaries or abdomical area.
They attract large maternal blood supply but do not implant properly.
embryo might easily break away from the maternal tissue
Cause excessive bleeding

53
Q

The trophoblast then contacts with the endometrium. This will result in:

A

rapid cell proliferation

54
Q

As cell proliferates, the nuclei divide but the cytoplasm does not. This then forms a tissue called:

A

syncytiotrophoblast

55
Q

The trophoblast that lines the blastocoel and in contact with ICM, remain as a single layer epithelium called:

A

cyntiotrophoblast

56
Q

Which tissue penetrates and invades the endometrium for implantation?

A

syncytiotrophoblast

57
Q

How is penetration achieved by syncytiotrophoblast?

A

It secretes enzymes that digest the extracellular material. The invasion is a reminiscent of a metastatic tumor.

58
Q

Beginning of maternal-placental circulation is made possible by a few steps. What are they?

A

lacunae, cavities formed in the syncytiotrophoblast filled with maternal blood from uterine capillaries, ruptured by the syncytiotrophoblast

59
Q

The ovary has to be maintained as no follicle cells are wanted after implantation. The leftover corpus luteum secretes called:

A

progesterone

60
Q

The trophoblast secretes a hormone that is required for maintenance of progesterone. What is it?

A

HCG

61
Q

Production of progesterone will eventually move from the corpus luteum to where?

A

the placenta

62
Q

the trophoblast will secrete hormones for which functions?

A

placenta growth, growth of mammary glands and regulate mother’s metabolism

63
Q

Explain another function of the trophoblast regarding immunology.

A

It prevents termination of pregnancy by providing the embryo with immunological privilege site.
The embryo will have both maternal and paternal antigens. The paternal antigens would trigger reaction by the mother’s antibodies.
The trophoblast prevents this

64
Q

During implantation the ICM splits into two tissues called the:

A

hypoblast and epiblast

65
Q

The hypoblast forms the Heuser’s membrane, also known as the:

A

extraembryonic endoderm.

66
Q

The Heuser’s membrane forms which structure of the embryo?

A

The yolk sac

67
Q

What does the epiblast form?

A

the three germ layers
the extraembryonic mesoderm
the amniotic membrane (extraembyonic ectoderm) that makes fluid that bathes the embryo

68
Q

After 14 days, the cytotrophoblast and extraembryonic mesoderm now protrudes into the syncitiotrophoblast, which extend into the lucanae to form what?

A

stem villi

69
Q

Within the stem villi, the mesoderm that forms blood vessels provide what purpose?

A

Increase efficiency of transfer of oxygen, carbon dioxide, nutrients and wastes between mother and foetus

70
Q

Transfer of oxygen from mother to foetus is by which haemoglobin, that has higher affinity for oxygen than the mother’s has?

A

embryonic and fetal haemoglobin

ANAT1003 (12 decks)

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