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Anatomy and Physiology 2B > Human Development and Aging > Flashcards

Human Development and Aging Flashcards

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1
Q

What is embryogenesis?

A

Events in development leading up to the embryo

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2
Q

The preembryonic stage is___

A

the first 16 days after fertilization

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3
Q

What is the fertilization window?

A

egg must be fertilized within 12-24 hours of ovulation

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4
Q

What is sperm capacitation?

A

the process that migrating sperm must undergo to make egg penetration possible

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5
Q

What are the two important events that occur during capacitation?

A
  • Female fluids leech cholesterol from sperm

- sperm becomes permiable to to Ca2+ increasing powerful flagella movements

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6
Q

How long is sperm viable for after ejaculation?

A

6 days

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7
Q

What reaction does sperm undergo when it encounters the egg?

A

An acrosomal reaction

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8
Q

What is a acrosomal reaction?

A

The exocytosis of the acrosome causing the release of enzymes needed to penetrate the egg

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9
Q

Once acrsomoal enzymes clear a path through the granulosa cells the next step is?

A

-sperm binds to the zona pellucida releasing more enzymes to help it to contact the egg

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10
Q

Once the sperm contacts the egg?

A

The egg destroys the sperms mitochondria so only the head enters

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11
Q

Fertilization is a combination of ___

A

The haploid set from the egg and spem combind

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12
Q

When the two haploid sets combine what is the produce?

A

a diploid. Fertilization is complete

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13
Q

What is polyspermy?

A

Fertilization of an egg by two or more sperm

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14
Q

What two mechanisms prevent polyspermy?

A
  1. Fast block-when sperm binds it opens Na+ channels causing depolarization preventing additional binding
  2. slow block-Penetration by sperm causes inflow of Ca2+ causing a swell of fluid beneth the zona pellucida pushing the rest of the sperm away
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15
Q

What step occurs after fertilization?

A

-The secondary oocyte completes meiosis II

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16
Q

What becomes of the egg and sperms nuclei after fertilization?

A
  • The egg discards one chromatid from each chromosome
  • the sperm and egg swell to become pronuclei
  • pronucli rupture and mix into a single diploid set
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17
Q

Once a diploid set is formed the egg is now called a ___ and is ready for___

A

Zygote ready for mitotic division

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18
Q

____ of all embros die in the first trimester. Why?

A
  • more than 50%
  • Conceptus is most vulnerable at this stage and precautions may not be taken because pregnancy may not have been noticed yet
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19
Q

What developments occur in the second trimester?

A
  • Most organs complete development
  • Distinct human form
  • Possible to survive if born
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20
Q

What occurs during the thrid trimester

A
  • Fetus growth is rapid
  • organs can support life
  • birth occurs at end of third trimester
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21
Q

When is a fetus considered mature?

A

35 weeks and 5.5 pounds

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22
Q

What are the three major processes during the preembryonic stage?

A
  1. Cleavage
  2. Implantation
  3. Embryogenesis
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23
Q

What is cleavage?

A

mitotic divisions in the first 3 days after fertilization

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24
Q

What is implantation?

A

The zygote implants itself into the endometrium

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25
What is embryogenesis?
the arrangement of the three primary germ layers
26
How many cells are produced during cleavage? | how long is the process of cleavage?
about 100 cells in about 72 hours
27
The end result of cleavage is called the___. How long does it rest in the uterus until implantation?
Morula? | 4-5 days
28
The morula becomes a blastocyst after___
The zona pellucida disintegrates and releases the conceptus
29
What is the internal cavity of the blastocyst?
The blastocel
30
What is the inner mass within the blastocel?
The embryoblast
31
Which portion of the blastocyst becomes the placenta?
the outer layer of cells called thee trophoblast
32
Which portion of the blastocyst secretes HCG?
The trophoblast
33
The three portions of the blastocyst are_ | BTE
- Blastocoel: internal cavity - Trophoblast: future placenta - Embryoblast: future embryo
34
Implantation occurs when the ____attaches to the _____. This occurs ___ days after ovulation
Blastocyst Placenta 6
35
How does the blastocyst attach to the endometrium?
The trophoblast cells that come into contact with the endometrium form two layers and invade the endometrium causing the endometrium to grow over the blastocyst
36
What are the two layers of cells formed by the trophoblast during implantation?
- Syncytiotrophoblast | - Cytotrophoblast
37
What is the function of the syncytiotrophoblast?
it is the layer of the trophoblast that invades the endometrium
38
How long does the process of implantation take?
about one week
39
What is the first step of embryogenesis?
The embryoblast forms an embryonic disc separates into two layers - Epiblast - Hypoblast
40
After the first seperation what is the next step in embryogenesis?
The emergence of three primary germ layers from the embryonic disc.
41
What are the three primary germ layers?
1. Ectoderm 2. Endoderm 3. Mesoderm
42
What are the two paces that flank the embryonic disc?
The Amniotic cavity and the Yolk sac
43
What is the primitive groove?
A split in the epiblast (soon to be sctoderm)
44
What is gastrulation?
The process of epiblast cells migrating into the groove and forming replacing the hypoblast with endoderm
45
Inbetween the endoder and the ectoderm forms the____
Mesoderm
46
Mesoderm eventually becomes ___
Mesenchyme
47
When is Embryogenesis complete
Once all three primary germ layers are fully formed
48
Once embryogenesis is complete the zygote is officially a ____
Embryo
49
When does the placenta form?
6 weeks from the begining of the embryonic stage begins
50
When are nearly all organs present?
at 8 weeks
51
Explain the process of embryonic folding
- The flat embryonic disc converts into a cylindrical form - The embryo folds around the yolk - the ectoderm doubles over and eventually covers the entire embryo - The mesoderm splits and forms two layers.
52
What form does the embryo have after the process of embryonic folding
A ball with a tube down the middle
53
The ectoderm eventually becomes the ____
epidermis
54
the mesoderm eventually becomes the ___
connective tissue
55
The endoderm eventually becomes the ___
Inner epithelial layers of the digestive tract
56
What are somites?
Segmentations of the mesoderm that eventually become the vertebral column, trunk muscles, and the dermis
57
What is the Amnion?
- Amniotic sac - a transparent sac that develops from the epiblast - completely encloses the embryo - penetrated by the umbilical cord
58
What is the yolk sac?
- A sac a fluid that forms from the hypoblast | - contributes to formations of GI tract, blood cells, and future egg and sperm
59
What is the Allantois?
- A pocket that forms from the yolk sack. | - forms the base of the umbillical and part of the bladder
60
What is the chorion?
the outtermost embryonic membrane that encloses all of the rest
61
What are the chorionic villi?
Pertrusions of embryonic blood vessels that pull nutrients from the mothers blood. Eventually form the placenta
62
What are the three sources of prenatal nutrition?
- Uterine milk - Trophoblastic nutrition - placental nutrition
63
What is uterine milk?
glycogen-rich secretion of the uterine tubes and endometrial glands -Used for nutrition before implantation
64
What is trophoblastic nutrition.
-Nutrition derived from the consumption of endometrium cells.
65
How long does is trophoblastic nutrition used for?
Up to 12 weeks but declines as the placenta grows
66
What is the placenta?
a disc-shaped organ attached to the uterine wall and to the fetus on the other
67
What is placental nutrition?
Nutrients diffused from the mothers blood through the placenta
68
What is the placental stage?
The period beginning around 9 weeks until birth where nutrition is supplied by the placenta.
69
What is placentation?
The development of the placenta
70
What is contained within the umbilical cord?
two umbilical arteries and one umbilical vein
71
What pumps blood from the placenta?
The fetal heart
72
Blood returns to the fetus via the
umbilical vein
73
An embryo is considered a fetus after ___ weeks
8
74
How any circulatory shortcuts are present in the fetus?
3
75
The two umbilical arteries form from the ____
Internal iliac arteries
76
O2 rich blood flows from the placenta to the _____ via the _____
Inferior vena cava | umbilical vein
77
How does the flow of blood differ in the fetus compaired to an infant?
- Blood mostly bipasses the pulmonary circuit | - Passes from atrium to atrium via fossa

Anatomy and Physiology 2B (7 decks)

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