Human Development

Question 1

starts about 24 hours after fertilization and continues as the embryo moves down the oviduct towards the uterus

Answer 1

Cleavage

Question 2

the mammalian equivalent of the sea urchin blastula

Answer 2

Blastocyst

Question 3

has a fluid-filled cavity, an inner cell mass that will actually form the baby

Answer 3

Human blastocyst

Question 4

an outer layer of cells

Answer 4

Trophoblast

Question 5

the organ that provides nourishment and oxygen to the embryo and helps dispose of its metabolic wastes.

Answer 5

Placenta

Question 6

under way by 9 days after conception

Answer 6

Gastrulation

Question 7

develop as attachments to the embryo and help support it.

Answer 7

Extraembryonic membranes

Question 8

Extraembryonic Membranes

Answer 8

1. Amnion
2. Yolk sac
3. Chorion
4. Allontois

Question 9

Developing as an extension of the yolk sacs

Extraembryonic Membranes

Answer 9

Allontois

Question 10

outer part of the
embryo’s skin; continuous with
the amnion

Answer 10

Ectoderm

Question 11

the embryo’s digestive tract; continuous with the yolk sac

Answer 11

Endoderm

Question 12

the bulk of most other organs

Answer 12

Mesoderm

Question 13

is filled with fluid, which protects the embryo

Answer 13

amniotic cavity

Question 14

breaks just before childbirth and the amniotic fluid (“water”) leaves the mother’s body through her vagina.

Answer 14

amnion

Question 15

remains small and produces the embryo’s first blood cells and its first germ cells, the cells that will give rise to the gamete-forming cells in the gonads.

Answer 15

Placenta

Question 16

it forms part of the umbilical cord

Answer 16

Allantois

Question 17

forms the embryo’s urinary bladder

Answer 17

Allantois

Question 18

In a bird and reptiles, the ____ expands around the embryo and functions in waste disposal.

Answer 18

Allantois

Question 19

lifeline between the embryo and the placenta

Answer 19

umbilical cord

Question 20

developed from the trophoblast and from mesoderm cells derived from the yolk sac

Answer 20

Chorion

Question 21

outermost extraembryonic membrane

Answer 21

Chorion

Question 22

cells in the chorion secrete a hormone called

Answer 22

human chorionic gonadotrophin (HCG)

Question 23

maintains the corpus luteum of the ovary during the first 3 months of pregnancy.

Answer 23

human chorionic gonadotrophin (HCG)

Question 24

contain embryonic blood vessels formed from mesoderm

Answer 24

Chorionic villi

Question 25

The chorionic blood vessels

color red: (1)
color blue: (2)

Answer 25

(1) absorb nutrients and oxygen
(2) carry wastes away from the embryo

Question 26

takes care of the embryo’s every need

Answer 26

Placenta

Question 27

allows protective antibodies to pass from the mother to the fetus.

Answer 27

Placenta

Question 28

A month-old human embryo is about ____ long

Answer 28

7mm (0.28in)

Question 29

____________ about 9 weeks after fertilization

Answer 29

Fetus

Question 30

the clear sac around the fetus is the _________

Answer 30

amnion

Question 30

First Trimester,

A fetus is about ____ long has all of its organs and major body parts, including a disproportionately large head.

Answer 30

5.5 cm (2.2in)

Question 31

Identify the trimester

• the somites have developed into segmental muscles and the bones of the back and ribs.
• the limb buds have become tiny arms and legs with fingers and toes.

Answer 31

First Trimester

Question 32

By the end of 1st trimester:

Answer 32

• the fetus looks like a miniature human being although its head is still oversized for the rest of the body.
• the sex of the fetus is usually evident at this time.

Question 33

2nd Trimester

At 14 weeks, The fetus is now about ________ long

Answer 33

6 cm (2.4 in)

Question 34

Identify the trimester

• Placenta takes over the task of maintaining itself by
  secreting progesterone rather than receiving it from corpus luteum
• At the same time, the placenta stops secreting HCG and the
  corpus luteum no longer needed to maintain pregnancy, degenerates

Answer 34

2nd Trimester

14 weeks

Question 35

2nd Trimester

At 20 weeks, the fetus is about ________ longs, weighs about ______

Answer 35

19 cm (7.6 in) & 1/2 kg (1lb)

Question 36

Identify the trimester

• Face of an infant, complete with eyebrows and eyelashes
• Its arms, legs, fingers and toes have lengthened
• It also has fingernails and toenails and is covered with fine hair

Answer 36

2nd Trimester

20 weeks

Question 37

Identify the trimester

• By this time, the fetal heartbeat is readily detected, and the fetus usually is quite active
• The mother’s abdomen has become markedly enlarged and she may often feel her baby move

Answer 37

Second Trimester

Question 38

Because of the limited space in the uterus, the fetus flexes forward into the so-called ______

Answer 38

fetal position

(Second Trimester)

Question 39

By the end of 2nd trimester:

Answer 39

the fetus eyes are open and its teeth are forming

Question 40

Identify the trimester

A time of rapid growth as the fetus gains the strength it will need to survive outside the protective environment of the uterus.

Answer 40

Third Trimester

Question 41

Identify the trimester

the fetus’ circulatory system and respiratory system undergo changes that will allow the switch to air breathing.

Answer 41

Third Trimester

Question 42

Identify the trimester

The fetus gains the ability to maintain its own temperature and its bones begin to harden and its muscles thicken.

Answer 42

Third Trimester

Question 43

Identify the trimester

• The fetus loses much of its fine body hair, except on its head
• The head itself changes its proportions

Answer 43

Third Trimester

Question 44

Identify the trimester

The fetus becomes less active as it fills the space in the uterus

Answer 44

Third Trimester

Question 45

At birth, a typical baby is about ________ longs and weighs _________

Answer 45

50 cm (20in) & 2.7-4.5 kg (6-10lbs)