Cleavage

Question 1

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

Answer 1

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

Question 2

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

Answer 2

blastocyst

Question 3

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

Answer 3

gametogenesis

Question 4

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

Answer 4

haploid

Question 5

In males, meiotic divisions produce how many spermatozoa？

Answer 5

4

Question 6

the sperm lose its cytoplasm when matured. true or false

Answer 6

true

Question 7

The head of the sperm contains:

Answer 7

haploid nucleus,
centriole
acrosome

Question 8

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?

Answer 8

sperm motor–axoneme

mitochondria

Question 9

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

Answer 9

tubulin

Question 10

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

Answer 10

false. it begins after puberty and continues through life

Question 11

How many days does it take to produce mature sperm?

Answer 11

64 days

Question 12

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

Answer 12

20-40 million sperm per ml

Question 13

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

Answer 13

15 million per ml or less

Question 14

where in the female reproductive tract does fertilization take place?

Answer 14

fallopian tubes

Question 15

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?

Answer 15

two polar bodies

discarded chromosomes

Question 16

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

Answer 16

True

Question 17

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

Answer 17

40,000

Question 18

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

Answer 18

prophase I

Question 19

The oocytes are held until fertilized in which meiotic phase?

Answer 19

Metaphase II

Question 20

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

Answer 20

ampulla

Question 21

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

Answer 21

zona pellucida; granulosa cells

Question 22

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

Answer 22

cortical granules

Question 23

What is parthenogenesis?

Answer 23

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

Question 24

What are hydatidiform moles?

Answer 24

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

Question 25

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

Answer 25

genomic imprinting.

Question 26

Describe genomic imprinting

Answer 26

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.

Question 27

Name one genetic disease linked with faulty genomic imprinting.

Answer 27

Angleman syndrome

Question 28

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

Answer 28

granulosa cells and somatic follicle cells

Question 29

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

Answer 29

zona pellucida

Question 30

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

Answer 30

ZP3 | become infertile

Question 31

Contact by the sperm and zona pellucida induces what reaction?

Answer 31

acrosome reaction

Question 32

What does the acrosome reaction do?

Answer 32

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

Question 33

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

Answer 33

- 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.

Question 34

What is polyspermy

Answer 34

when many sperm fuse with one egg.

Question 35

Describe what happens during meiotic divisions in the fertilized egg.

Answer 35

- 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.

Question 36

What are cleavage divisions then?

Answer 36

embryonic cell divisions that are not accompanied by growth

Question 37

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

Answer 37

32

Question 38

What is the blastocyst?

Answer 38

a fluid filled cavity within the embryo

Question 39

The blastocyst has an outer layer of membrane called: | and a small clump of inner cells called:

Answer 39

trophoblast | Inner cell mass

Question 40

The trophoblast will form which tissue of the placenta?

Answer 40

chorionic tissue

Question 41

The Inner cell mass will form:

Answer 41

``` the foetus and two extraembyonic membranes extraembryonic endoderm, extraembyonic mesoderm and amniotic membrane (extraembryonic ectoderm) ```

Question 42

The extraembyonic endoderm is also called:

Answer 42

Heuser's membrane

Question 43

The extraembryonic mesoderm forms the:

Answer 43

vasculature of the umbilical cord and placenta

Question 44

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

Answer 44

decidua

Question 45

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

Answer 45

ICM

Question 46

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

Answer 46

dizygotic twins

Question 47

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

Answer 47

placenta

Question 48

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

Answer 48

conjoined twins

Question 49

How is tetragametic chimera formed

Answer 49

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

Question 50

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

Answer 50

blastomeres

Question 51

what is implantation?

Answer 51

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

Question 52

Why are ectopic pregnancies dangerous?

Answer 52

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

Question 53

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

Answer 53

rapid cell proliferation

Question 54

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

Answer 54

syncytiotrophoblast

Question 55

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

Answer 55

cyntiotrophoblast

Question 56

Which tissue penetrates and invades the endometrium for implantation?

Answer 56

syncytiotrophoblast

Question 57

How is penetration achieved by syncytiotrophoblast?

Answer 57

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

Question 58

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

Answer 58

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

Question 59

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

Answer 59

progesterone

Question 60

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

Answer 60

HCG

Question 61

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

Answer 61

the placenta

Question 62

the trophoblast will secrete hormones for which functions?

Answer 62

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

Question 63

Explain another function of the trophoblast regarding immunology.

Answer 63

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

Question 64

During implantation the ICM splits into two tissues called the:

Answer 64

hypoblast and epiblast

Question 65

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

Answer 65

extraembryonic endoderm.

Question 66

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

Answer 66

The yolk sac

Question 67

What does the epiblast form?

Answer 67

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

Question 68

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

Answer 68

stem villi

Question 69

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

Answer 69

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

Question 70

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

Answer 70

embryonic and fetal haemoglobin