1.5

Question 0

As the chorionic villi develop, they become surrounded by maternal blood spaces. This provides a

Answer 0

Large surface are over which the foetus can obtain nutrients and exchange gases with the mother’s blood

Question 1

Some of the cells in the blastocyst form

Answer 1

Chorionic villi that secrete enzymes to digest the outer layer of the endometrium

Question 2

Chorionic villi =

Answer 2

Beginning of the placenta

Question 3

the cells in the inner mass of the blastocyst differentiate into the

Answer 3

Many different kinds of cell that makes up tissues and organs

Question 4

25 days after ovulation the embryo has a

Answer 4

Primitive bating heart

Question 5

4 weeks after ovulation the

Answer 5

Brain is growing rapidly
The eyes and ears have started to form
Gut is beginning to develop

Question 6

10 weeks after fertilisation the

Answer 6

Main body organs have formed and the embryo becomes a foetus
Main body organs have now formed
Foetus only about 35mm long from rump to head

Question 7

The foetus is protected inside a sac called the

Answer 7

Amnion

Question 8

Amnion secretes

Answer 8

Amniotic fluid

Question 9

The umbilical cord connects the foetus to the placenta and carries

Answer 9

Blood between the two

Question 10

Umbilical cord contains 2 umbilical arteries, carrying blood from the foetus to the placenta and an umbilical vein carrying blood

Answer 10

From the placenta to the vein

Question 11

The foetus depends on the placenta for its development. Nutrients pass from the mother’s blood into the foetus’ blood in the placenta such as:

Answer 11

Glucose
Amino acids
Mineral ions
Water
Oxygen

Question 12

Antibodies also pass from the mother to the foetus so that the foetus is protected from the same diseases as the

Answer 12

Mother

Question 13

Immunity from these antibodies lasts for a short time after birth as the foetus does not

Answer 13

Produce it’s own memory cells

Question 14

The placenta contains a large number of chorionic villi and the capillaries are separate from the maternal blood by a thin membrane that has

Answer 14

3 layers

Question 15

3 layers of the membrane are:

Answer 15

• wall of the villus, consists of a thin layer of fused cells (micro villi which considerably increase surface area)
• a thin layer of connective tissue
• endothelium cells making up the capillary wall

Question 16

The mothers blood and the foetal blood flow in opposite directions know as

Answer 16

Countercurrent flow

Question 17

Countercurrent flow ensures that there is a

Answer 17

Concentration gradient all the way along the capillary

Question 18

CCF - blood from the foetus arriving in the placenta has a very low oxygen concentration (0) but it receives oxygen by diffusion from the mothers blood which has a higher oxygen concentration:

Answer 18

(2)

Question 19

the blastocyst and the developing placenta produce the hormone

Answer 19

Human chorionic gonadotrophin (hCG)

Question 20

hCG is secreted in large amounts in the first 2 months of pregnancy and is

Answer 20

Present in the urine of pregnant women

Question 21

Presence of hCG forms the

Answer 21

Basis of pregnancy tests

Question 22

In the first 3 months of pregnancy, the corpus luteum continues to Secrete progesterone and a small amount of oestrogen. This inhibits

Answer 22

Contraction of the myometrium

Maintains the endometrium

Question 23

After the first 3 months of pregnancy, the corpus luteum begins to

Answer 23

degenerate and the placenta secretes increasing amounts of progesterone together with some oestrogen

Question 24

Progesterone also inhibits the production of FSH

Answer 24

from the pituitary gland

Question 25

Screening in pregnancy :

Answer 25

Amniocentesis | Samples of chorionic villi

Question 26

Amniocentesis a hypodermic needle is inserted through the mother's abdomen and a small sample of amniotic fluid is extracted. This will

Answer 26

Contain some foetal cells

Question 27

Amniocentesis the needle is guided into a suitable position by using an

Answer 27

Ultrasound scan

Question 28

Amniocentesis the cells are extracted and stimulated so that they

Answer 28

Divide by mitosis

Question 29

A spindle inhibitor is then added so that the cells do not complete

Answer 29

Mitosis

Question 30

The cells are placed in a dilute salt solution so that they swell cupcake then chromosomes are photographed. The images of the chromosomes are then manipulated on a computer screen and

Answer 30

Arranged in homologous pairs - enables chromosome defects to be detected

Question 31

Sample of chorionic villi involves using a plastic catheter inserted through the

Answer 31

Vagina

Question 32

After 3-4 days zygote has formed a ball of cells called a

Answer 32

Morula

Question 33

By about 5-6 days it has formed a

Answer 33

Blastocyst

Question 34

The outer layer of cells on a blastocyst (trophoblast) will develop into the

Answer 34

Membranes around the embryo and the beginnings of the placenta

Question 35

The inner cell mass of the blastocyst is the part from which the

Answer 35

Embryo will develop

Question 36

The blastocyst reaches the uterus about a week after fertilisation takes a few days for

Answer 36

Implantation to occur

Question 37

zona pellucida surrounding blastocyst breaks open and the trophoblast cells at one end of the embryo form villi that secrete enzymes-

Answer 37

Digest the outer layer of the endometrium releasing nutrients for the developing embryo

Question 38

4 functions of the placenta:

Answer 38

- allows female mammals to carry young inside during early development - during pregnancy, foetus receives all it's nutrients via the placenta - all the waste products in the foetus' blood are removed via the placenta - the placenta also produces hormones

Question 39

Placenta consists of thousands of chorionic villi that project into the endometrium. The maternal blood vessels surrounding the chorionic villi break down forming

Answer 39

Maternal blood sinuses

Question 40

Placenta is surrounded by capillaries which cause a larger surface area CO2 from O2 from

Answer 40

Chorionic villi to placenta | Placenta to chorionic villi

Question 41

Placenta hormones

Answer 41

Human chorionic gonadotrophin Progesterone Oestrogen Follicle stimulating hormone

Question 42

Functions of placenta:

Answer 42

Barrier Immune protection Site of exchange

Question 43

Placenta acts as a barrier

Answer 43

Limits the transfer of blood components from maternal blood to foetal system Cells of the maternal immune system do not cross so reducing risk of immune rejection

Question 44

Placenta act as a immune protection

Answer 44

Protective molecules cover the surface of the early placenta, 'hiding' it from the maternal immune system

Question 45

Placenta acts as a site of exchange as

Answer 45

Of many dilutes between maternal and foetal systems

Question 46

Foetus haemoglobin has a higher

Answer 46

Affinity for oxygen then maternal haemoglobin

Question 47

Endocrine function

Answer 47

The placenta takes over the production of oestrogen and progesterone as the corpus luteum degenerates ensuring the endometrium is maintained