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Biology 30 > 15.1 > Flashcards

15.1 Flashcards

1
Q

What are the 2 main periods of prenatal development?

A

The embryonic period and the fetal period

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2
Q

When does the Embryonic period of development take place?

A

The first 8 weeks, or the first 2/3rds of the first trimester

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3
Q

What happens in the embryonic stage of development?

A

Cells divide and become redistributed. tissues and organs form, as do structures that support and nourish the developing embryo

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4
Q

When does the Fetal period of development take place?

A

From the start of the 9th week till birth

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5
Q

What happens in the fetal period of development?

A

The body grows rapidly and organs begin to function and coordinate to form organ systems

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6
Q

What is fertilization?

A

The joining of male and female gametes that join to form a single cell with 23 chromosomes from each parent

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7
Q

How many days after ovulation does it take the ova to reach the uterus?

A

4 days

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8
Q

How many hours after ovulation must an egg be fertilized?

A

12 to 24 hours

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9
Q

When and where must the sperm meet the egg?

A

During the early part of its movement through the oviduct

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10
Q

Where must sperm go once its it ejaculated?

A

It must makes its way through the cervix and then through the uterus and finally the oviduct and into the egg

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11
Q

Why don’t most sperm survive the journey?

A

Because of the naturally acidic environment of the vagina and other go the wrong way

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12
Q

What is the membrane of the egg surrounded?

A

A thin clear layer of protein and carbohydrates called zona pellucida

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13
Q

What is the Zona Pellucida surrounded by?

A

Several jelly like layers of follicle cells that loosley adhere to one another called the Corona Radiata

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14
Q

What were the Corona Radiata to an egg?

A

A source of nourishment when it was in an ovarian follicle

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15
Q

What happens when sperm meets the corona radiate?

A

The sperms enzyme containing acrosome releases its contents

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16
Q

What do the enzymes released by the Acrosome do?

A

The enzymes digest a path through the corona zona pellucida

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17
Q

What happens once a sperm enters the egg?

A

The eggs plasma membrane depolarizes, preventing other sperm from binding and entering

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18
Q

What is a Zygote?

A

The single cell that is created when an egg and sperm join

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19
Q

What happens within 30 seconds of a zygote forming?

A

The 0.1 mm zygote divides by mitosis until it forms eight cells and so one

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20
Q

What is cleavage?

A

The process of cell division by a zygote with out the enlargement of cells

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21
Q

What is the morula stage?

A

When a zygote is a sphere of 16 cells

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22
Q

How many days after fertilization does the morula reach the uterus?

A

Within 3 to 5 days after fertilization

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23
Q

What happens as the Morula begins to fill with fluid?

A

2 different groups of cells form

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24
Q

What is the Blastocyst stage?

A

The stage after the Morula fills with liquid and 2 cell groups form

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25
What is one of the cell groups in the Blastocyst?
The trophoblast, which forms the outer layer
26
What does the Trophoblast develop in?
A membrane called the Chorion
27
What does the Chorion in turn develop into?
The placenta
28
What is the Placenta?
The structure that provides nutrients and oxygen and removes wastes from developing offspring
29
When does the other group of cells within the blastocyst form?
The Inner Cell Mass (embryoblast)
30
What does the Inner cell mass develop into?
The embryo itself
31
How many does after fertilization does the blastocyst attach itself to the endometrium?
Between the fifth and seventh day after fertilization
32
What does the Trophoblast do after the Blastocyst attaches itself to the endometrium?
The Trophoblast cells secrete enzymes that digest some of the tissues and blood vessels of the endometrium to allow the blastocyst to sink into the uterine wall
33
What is implantation?
The nestling of the blastocyst into the endometrium
34
On what day of fertilization does implantation take place?
By day 10-14
35
What does the Trophoblast secrete after implantation?
A hormone called human chorionic gonadotropin (hCG)
36
What does hCG do?
It has the same effects as as LH and maintains the corpus luteum past the time it would otherwise degenerate
37
What happens as a result of the Corpus Luteum being maintained?
It continues to secrete estrogen and progesterone which maintains the endometrium
38
What are the levels of hCG over pregnancy?
hCG continues at a high level for about two months then declines to a low level by the end of four months
39
How long does the Corpus Luteum remain intact?
Throughout the entire pregnancy
40
What secretes hormones after the first trimester?
The placenta which secretes estrogen and progesterone
41
What is the Amniotic cavity?
The space between the inner cell mass and trophoblast that fills with fluid and the baby will develop
42
What happens to the inner cell mass as the amniotic cavity forms?
The inner cell mass flattens into a disc like structure called the embryonic disc
43
What is the embryonic disc supported by?
A short stalk which connects the blastocyst to the endometrium
44
What are the 3 layers of the embryonic disc?
The outer ectoderm which is closer to the amniotic cavity The inner endoderm And the middle layer called mesoderm
45
What is Gastrulation?
The process of forming the 3 layers of the embryonic disc
46
What are the primary germ layers?
The 3 layers of the embryonic disc
47
What is the name of the developing embryo once it develops the primary germ layers?
The Gastrula
48
What does Gastrulation mark the start of?
Morphogenesis
49
What is Morphogenesis?
The series of events that form distinct structures of the developing organism
50
What is differentiation?
The cellular process that enable cells to develop a particular shape and to perform specific functions
51
What happens between the 3rd and 8 weeks of a developing embryo?
Different rates of cell division in the primary germ layers cause tissues to fold it distinct patterns
52
What happens on the third week of development?
A thickened band of mesoderm cells develop along the back of the embryonic disk
53
What does the mesoderm form?
A rod like structure called the notochord which will eventually form the baby's back and be the framework for the skeleton
54
Which layer of the three layers does the nervous system form from?
The ectoderm
55
What are the three layers of the embryonic disk?
Ectoderm (outer) Endoderm (Inner) Mesoderm (middle)
56
What is Gastrulation?
The process of forming the three layers of the embryonic disc
57
What is the collective name of the 3 layers of the embryonic disc?
The primary germ layers
58
Why is the formation of the primary germ layers important?
Because the cells, tissues, and organs of the body are derived from the primary germ layers
59
What does the mesoderm form?
A baby's back and forms a rod like structure called the notochord
60
Which primary germ layer does the nervous system come from?
The ectoderm
61
How does the spinal chord form from the primary germ layers?
First, the cells along the surface above the notochord (the ectoderm) begin to thicken and then folds develop on each side of a groove along the surface. And then the folds fuse and become a tube
62
What is the tube that fuses around the notochord called?
The neural tube
63
What is Neurulation?
The process of forming the neural tube
64
By what day of development does the heart start beating?
Day 18
65
What happens after the fourth week of prenatal development?
Rapid growth and differentiation
66
What happens during the fourth week?
Blood cells start to form and fill vessels | Distinct head and facial features form
67
What happens during the 5th week of development?
The embryo's head is very large in comparison with its body They eyes open Cells in the brain are differentiating very quickly The cells in the embryo are 1.3 centimeters
68
What happens in the sixth week of development?
The brain continues rapid development The limbs lengthen and flex slightly The gonads are starting to produce hormones
69
What happens during the 7th and 8th week of development?
The embryo has distinct human characteristics The organs are formed and the nervous system is starting to coordinate body activity A skeleton of cartilage has formed Eyes are developed but the lids are now closed Genitalia is forming
70
What happens by the end of the 8th week?
The embryo is about the size and mass of a paper clip and about 90 percent of the organs and other structures that make up the human body are established
71
What are extra-embryonic membranes?
An intricate system of membranes that are external to the embryo
72
What are the extra-embryonic membranes?
Allantois Amnion Chorion yolk sac
73
What are the extra-embryonic membranes responsible for?
Protection Nutrition Respiration Excretion of the embryo
74
What are Chorionic Villi?
Finger like projection that extend from the chorion into the uterine lining that establish the beginnings of the placenta
75
What is a placenta?
A disk shaped organ that is rich in blood vessels
76
How is the embryo attached to the uterine wall?
By the placenta
77
What is the placenta the site of?
Metabolic exchange
78
When is the placenta fully developed?
By about 10 weeks
79
What is Amnion?
A transparent sac that develops from the cells of the embryonic disk which encloses the embryo completely and is penetrated by the umbilical cord
80
What is the purpose of amniotic fluid?
Protects the embryo from trauma and temperature fluctuations
81
What is the Yolk Sac?
A small sac that is suspended from the abdominal area of the embryo
82
What does the Yolk Sac do?
Contributes to the formation of the digestive tract and produces the first blood cells and the future egg or sperm cells
83
What does the Allantois do?
Forms the foundation of the umbilical cord
84
What happens to the Allantois do during the second month?
The allantois degenerates and the remainder becomes part of the urinary bladder
85
What is the Chorion?
The outermost membrane that encloses all other extra-embryonic membranes
86
Which part of the placenta comes from the embryo?
The chorion
87
What does the closeness of the mother and embryo permit?
Nutrients and oxygen to diffuse from the mothers circulatory system to the baby and for wastes to leave the baby's circulation
88
What does the placenta not filter out?
Alcohol Drugs Nicotine
89
What is the umbilical cord?
A rope like structure that leads from the belly button of the fetus to the centre of the placenta
90
What do the two arteries of the placenta do?
Transport oxygen depleted blood from the fetus to the placenta. It also contains on vein which brings oxygen rich blood to the fetus

Biology 30 (34 decks)

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