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Biology 235 > Chapter 29 Fetal Development and Childbirth > Flashcards

Chapter 29 Fetal Development and Childbirth Flashcards

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1
Q

What is the Embryonic Period

A

extends from fertilization through the eighth week. Includes fertilization, cleavage of the zygote, blastocyst formation and implantation
week 1 through 8
tissues and organs have already formed by the end

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2
Q

What is the fetal Period?

A

9th week to birth

very few new structures appear

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3
Q

What is pregnancy?

A

is a sequence of events that begins with fertilization; proceeds to implantation, embryonic development, and fetal development; and ideally ends with birth about 38 weeks later, or 40 weeks after the last menstrual period

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4
Q

What are the sections of prenatal development?

A

Prenatal - fertilization to birth

divided into 3 sections 1st, 2nd, 3rd trimester

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5
Q

Describe Fertilization

A 
the genetic material from a haploid sperm cell (spermatozoon) and a haploid secondary oocyte merges into a single diploid nucleus. Usually happens in the Fallopian tube near the ovary also called Uterine Tube
200 mil sperm introduced
2 mil (1%) reach cervix
200 reach secondary ooctye
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6
Q

What is capacitation?

A
  • a series of functional changes that cause the sperm’s tail to beat even more vigorously and prepare its plasma membrane to fuse with the oocyte’s plasma membrane

at the same time the female secretions remove cholesterol, glycoproteins and proteins from the plasma membrane around the head of the sperm

Only capacitate sperm are attracted to and respond to the cells around the oocyte

usually happens in Fallopian Tube (aka Uterine Tube)

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7
Q

What is the Corona Radiate

A

one of 2 layers that sperm must penetrate . Granulosa cells that surround the secondary oocyte

remember Corona is the outer layer of the sun and the oocyte!

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8
Q

Where is the zona pellucide located?

A

It is a – clear glycoprotein layer between the corona radiate and oocyte’s plasma membrane .

the glycoprotein ZP3 from this area acts as a sperm receptor

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9
Q

What is the acrosome?

A

the helmetlike structure that covers the head of the sperm

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10
Q

Describe the Acrosomalreaction

A

This is the release of the contents of the acrosome how?
binding of ZP3 with sperm and Voila released!

The acrosomal enzymes digest a path through the zona pellucida – many sperm bond to ZP3 only first one through fertilizes the egg

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11
Q

What is polyspermy

A

oocyte being fertilized by more than one cell

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12
Q

Describe the mechanisms of both fast and slow block to polysperm

A

FAST Block - – cell membrane depolarizes (once depolarized can’t fuse with another sperm)

Slow Block - depolarization causes Ca+ ions to be released this makes theZP3 inactive and harden the zona pell

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13
Q

What are the male and female pronucleus?

A

Male - – this is what the head of the sperm develops into after the first meiosis of the oocyte

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14
Q

How quickly can sperm fertilize the oocyte?

A

Arrive with in minutes after but can’t fertilize for at least 7 hour,usually within 12 - 24 hrs can live for 48 hours

Oocyte can only live 24 hr

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15
Q

Figure 29.1 will give you visual of layers of the secondary oocyte

A

can you name them?

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16
Q

What is a syngamy?

A

The process when the male and female pronuclei fuse and produce a single diploid nucleus

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17
Q

What is a zygot?

A

The fertilized ovum resulting from the union of the male and female gametes

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18
Q

What is the difference between a monozygotic twin and a dizygotic twin?

A

Mono - twins who develop from a SINGLE ovum - identical twins

DI - twins who develop when 2 separate ovum are fertilized (fraternal twins)

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19
Q

What happens to produce conjoined twins?

A

When separation of monozygotic twins after 8 days is not complete – means twins joined and share some body structures

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20
Q

What are the stages the zygote develops through.

A

The zygote is still travelling in the Fallopian Tube.
First Step is Cleavage
2nd is Formation of Blastocyst
3rd is Implantation

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21
Q

More about Cleavage. When does it start, how big is the zygote when this stage is finished?

A

cleavage - rapid mitotic cell divisions of the zygote (first division starts 24 hour after finished 6 hours later, by 2nd day second cleavage complete = 4 cells, 3rd day 16 cells)

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22
Q

During cleavage we know that the cells produced get smaller and smaller. What is their name?

A

Blastomeres

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23
Q

During cleavage the zygote still has the Zona Pellucida surrounding it and it hasn’t grown in size.
What is the solid sphere of cells produced by cleavage called?

A

Morula

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24
Q

What is the Blastocyst and when does it form?

A

at about day 4 or 5 (32 cells in the morula) – fluid enters the morula and cells reorganize around a cavity filled with fluid in the center (blastocavity). Once the cavity is formed the entire mass is called a BLASTOCYST. (100’s cells but still same size as the zygote)

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25
Q

The Blastocyst has 2 types of cells in it, what are they?

A

Inner Cell Mass -embryoblast cells are located internally and develop into embryo
Trophoblast -outer layer of cells that forms a wall around the blastocyst

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26
Q

What will Trophoblast cells later develop into?

A

will develop into the outer chorionic sac surrounding the fetus

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27
Q

What happens around the 5th day?

A

Blastocyst hatches through the zona pell and this allow implantation to occur. Implantation (the blastocyst loosely attaches to the endometrium) Takes about 1 - 2 more days .

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28
Q

Figure 29.2 shows the steps of blastocyst formation

A

There are 4 steps and 5 pictures

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29
Q

How long does the blastocyst hang out in the uterus before it decides to attach?

A

bout 2 day….. indecisive little snot!

Then loosely attaches and by 7th day firmly attaches

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30
Q

Where does the blastocyst usually implant?

A

in either the posterior portion of the fundus or the body of the uterus.

It turns with the inner cell mass toward the endometrium

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31
Q

What are the layers of the Decidua?

What is the Decidua formerly known as?

A

Decidua Basalis and decidua capsularis and decidua parietalis (decidua means falling off and the decidua separates from mother after birth and is expelled)

Before implantation, the decidua is known as endometrium

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32
Q

What is the function of the Decidua Basalis?

A

– provides large amounts of glycogen and lipids for the embryo and later the fetus (finally become part of the maternal placenta)

It is located between the embryo and the stratum basalis of the uterus

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33
Q

What type of decidua is the endometrium that is in the uterus but not involved with the embryo?

A

Decidua Parietalis

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34
Q

Where is the Decidua Capsularis located?

A

is the portion of the endometrium located between the embryo and the uterine cavity

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35
Q

What is an ectopic pregnancy

A
  • development of an embryo or fetus outside the uterine cavity usually in the Uterine tube

Fatal to mom if not aborted

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36
Q

What is the single layer of squamous cells that form a domelike roof above the epiblast cells (the inner cell mass in the bastocyst) called?

A

amnion

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37
Q

What are the purposes of amniotic fluid?

A

serves as a shock absorber and regulates fetal body temperature, keep fetus hydrated, stops fetus from adhering between fetus and surrounding tissue

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38
Q

How is amniotic fluid created.

This question was on at least 2 of the quizzes I took either in book or online.

A

first from maternal blood- later fetus contributes urine –

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39
Q

How is the yolk sac formed

A

– 8th day, when cells migrate and cover the inner surface of the blastocyst wall they become squamous cells (flat) and form a thin membrane (exocoelomic membrane).

This membrane combines with hypoblast & forms the wall of the yolk sac –

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40
Q

What is the purpose of the yolk sac?

A

supplies nutrients during 2nd and 3rd weeks of development. Is source of blood cells during 3rd to 6th weeks. Contains first cells that develop into gonads, form gametes, form parts of gut and acts as a shock absorber and stops fetus from drying

41
Q

What membrane that surrounds the embyro becomes a prinicpal part of the placenta?

A

Chorin

42
Q

How does the Chorin protect baby from Mom’s immune response?

A

Protects baby from immune response of the Mom in 2 ways. Promotes production of T lymphocytes that suppress immune response of uterus. Produces hCG (human chorionic gonadotropin)

43
Q

Figure 29.5 has nice summary of first week of development

Can you list the stages with time frame?

A
  1. Fertilization - fallopian tube 12 to 24 hours
  2. Cleavage -1st cleavage about 30 hrs after ferti
  3. Morula (3 -4 days after fert moving toward uterus now)
  4. Blastocyst ( 4.5 - 5 day )
  5. implantation ( 6 ish day)
44
Q

What forms the roof of the amniotic cavity and what forms the floor

A

The amnion forms the roof and epiblasts form the floor

45
Q

When the amnion ruptures just before birth what is the fluid like?

A

Clear and runny like water.

46
Q

Why is the yolk sac relatively unimportant in human development?

A

because fetus gets most of it’s nutrients from the endometrium

47
Q

What layers form the Chorion?

A

the extraembryonic mesoderm and 2 layers of the trophblast

Chorion surrounds embryo and later the fetus

48
Q

What are the main features of the 2nd week of development?

A

formation of the amnion, yolk sac, chorion and connecting stalk.

49
Q

What are the main features of the 3rd week of development?

A

Gastrulation, neurulation, development of chorionic villi and placenta

50
Q

What is gastrulation?

A

the bilaminar embryonic disc transforms into trilaminar ( 3 layers)embryonic disc

51
Q

Describe the process of Gastrulation

A

Formation of the primitive streak which is a grove on the disc which establishes the head and tail , right and left sides

52
Q

What are the primary Germ layers

A

they are the major embryonic tissues from which the various tissues and organs of the body develop. Forms after primitive streak appears

53
Q

In primary Germ layers describe the 3 layers

A

Ectoderm
Mesoderm
Endoderm

54
Q

Cells made of epithelia tissue (tightly packed cells) in the ECTOderm develop into what parts of the fetus?

A

develops into the epidermis of skin and nervous system.

55
Q

Cells between the Epiblast and new endoderm are called what?

A

Mesoderm

56
Q

What do cells in the mesoderm develop into

A

develops into muscles, bones, connective tissues and peritoneum

57
Q

What do cells in the Endoderm develop into

A

– eventually becomes lining of the gastrointestinal tract, respiratory tract and other organs

58
Q

How many types of embroyonic discs are there?

A

2 types , 2 and 3 layered disc made up of cells from hypoblast and epiblast cells

59
Q

The process by which the neural plate and neural folds and neural tube are created is called?

A

Neurulation

60
Q

What is the neurul groove?

A

the depressed area in between the neural folds in the neural groove

61
Q

How is the neural fold created?

And what does it develop into?

A

lateral edges of neural plate curve up (elevate) and create the neural fold –eventually edges meet and create a tube called neural tube. Starts in the middle of the embryo and moves out toward head and tail, neural tube cells develop into brain and spinal cord

62
Q

What is Lucuae

A

maternal blood filled spaces in the uterine wall

created as embryonic tissue invades the uterine wall

63
Q

What is Chorionic Villa?

A

fingerlike projections consist of chorion (syncytiotrophoblast surrounded by cytotrophoblast) that projects into the endometrial wall of the uterus

64
Q

When do blood capillaries develop in the choronic villa

A

by the end of the 3rd week. these start to form at the end of the second week

65
Q

When fetal blood capillaries (part of the chorion villa invade the lacuae, these 2 structures combine to form what?

A

Intervillious Spaces

where chorionic villa is bathed in maternal blood

66
Q

Do materal and fetal blood mingle?

A

This is strictly a look but don’t touch situation.

Fetal blood and maternal blood next mix

67
Q

How does the fetal blood get the nutrients and O2 needed?

A

diffuse across cell membrance from the intervervillous spaces to the chorionic villa

68
Q

What is the placenta?

A

the site of exchange of nutrients and wastes between the mother and fetus

69
Q

What part of mom forms into the placenta?

A

Decidua basalis

This has been in several questions. Often they use the wrong type of decidua, making that choice incorrrect

70
Q

When does the placenta develop and what parts of the baby and mom form the placenta

A

Unique because it develops from 2 separate individuals.

in the 12th week

chorionic villa and decidua basalis

pancake shape

71
Q

What are the main functions of the placenta

A

Allows oxygen and nutrients to diffuse from mother, CO2 and waste removed the same way
Protects from microrganisms can’t get through
Viruses can, HIV, measles, chickenpox etc.
Drugs, alcohol can pass through
Placenta stores carbohydrates, proteins, calcium, iron to be released into baby’s circulation as needed

72
Q

Know what can go through the placenta and what is stopped by the placenta.

A

no go - microrganisms

can go - drugs, alcohol, viruses

73
Q

Describe the umbilical cord it, components and purpose

A

develops from the connecting stalk and connects embryo and later fetus to placenta
2 cm wide, 50-60 cm long
Has 2 arteries that carry Deoxygenated fetal blood to placenta
Has 1 vein that carries oxygen and nutrients to fetus (these come from mom’s intervillious spaces)

74
Q

When the placenta detaches from the uterus and is expelled after birth it’s called the ?

A

After birth

75
Q

What is the umbilicus

A

The navel. How it’s formed?
at birth cord is cut and about an inch is left on the baby. This dries and falls off after 10/12 days. Scar tissue develops where the cord was attached and this is the umbilicus

76
Q

What is the fetal period?

A

9th week to birth – tissues/organs already formed continue to grow and differentiate. Very few new structures appear. Fetus is less vulnerable to effects of drugs and radiation

77
Q

Describe the embryo’s growth in the 5th and 6th weeks

A

5th week - rapid brain development
end of 6th - head grows large in comparison to trunk
neck and trunk begin to straighten, hear now has 4 chambers,

78
Q

Describe embryo’s growth in 7th and 8th weeks

A

7th week - limbs become distinct beginning of digits appear
8th - start of this week - tail is shorter but visible, fingers/toes are webbed
eyes are open, ears are visible
end of 8th week
all regions of limbs apparent
no more webbing in fingers and toes
tail disappears and external genital appear

79
Q

What are the 3 stages of labour?

This was a common question

A

Dilation - opening of the cervix to 10 cm
Explusion - baby coming out
Placental stage - delivery of placenta

80
Q

Parturtion is another word for ?

A

Labour

81
Q

Define Labour.

A

process by which the fetus is expelled from uterus through the vagina

82
Q

What are the chemical changes that start labour?

A

During pregnancy PROESTERONE (PRO) inhibits labour. So when labour starts, sharply increasing ESTROGEN (EST) levels in mom overcome the progesterone

Inceasing EST level stimulate fetus to produce ACTH which causes fetus to produce DHEA

Placenta coverts DHEA into EST which stimulates OXYCTOCIN receptors in the uterus .
OXYCTOCIN causes uterine contractions

83
Q

What are the symptoms of true labour

A

when uterine contraction occur at regular intervals, usually produciong pain. Some women get concentrate lower back pain - **most reliable symptom is dilation of the cervix and the show, discharge of blood containing mucus plug from the cervix

84
Q

Typically how long do the 3 stages of labour last?

A

Dilation 6 - 12 hour
Explusion 10 min to several hours
Placental - 5 to 30 min

85
Q

What must happen in mom to move from dilation stage to expulsion stage?

A

Cervix must be 10 cm dilated

86
Q

Why are uterine contractions after the delivery of the palcenta so important

A

contractions also constrict blood vessels that were torn during delivery (to stop bleeding) OXYCTOCIN is important here to keep Uterine contracting

87
Q

Is the control of labour contractions a positive feedback cycle?

A

Yes, uterine contracts for baby’s head into cervix stretching it. Nerve in cervix send message to hypothalamus causing it to release more OXY into blood which is carried to uterus and causes uterine contractions

88
Q

What stops the positive labour feedback cycle?

A

Baby’s head moves past the cervix and no longer pushes on it.

89
Q

When the uterus shrinks it is called ?

A

Involution

90
Q

When does the embryos heart start beating?

A

within 4 weeks

91
Q

Between 5 and 8 weeks, what develops in the embryo?

A

heart becomes 4 chambered,
nose develops but it’s flat,
bone formation begins,
blood cells start to form in liver,
many internal organs continue to develop
There are others covered in another slide

92
Q

9 - 12 weeks fetus charateristics

A 
Heart beat detected
head is half the body length
fetal length nearly doubles
brain grows larger
eyes fully developed
external ears develop
upper limbs longer than lower limbs
can determine gender
excreted urine is added to amniotic fluid
fetus begins to move but can't be felt by mom
93
Q

13-16 weeks

A

head is smaller than the rest of the body
eyes and ears move to final positions
lower limbs lengthen

94
Q

17 - 20 weeks

A

head is more proportionate to rest of body
eyebrows and head hair grow
lower limbs continue to lengthen but more slowly
fetus covered in Vernix caseosa (fatty secretions and dead epithelial cells) and Lanugo (delicate fetal hair)
fetal movements felt by mom

95
Q

21-25 weeks

A

head become even more porportionate to body
weight gain is substantial
skin is pink and wrinkled
can survive from 24 weeks onward

96
Q

26 - 29 weeks

A

eyes are open
toe nails visible
body gains fat (3.5% of total body weight)
tests begin to descend
red bone marrow is major site of blood cell production

97
Q

30 -34

A

skin pink and smooth
fetus moves to an upside down position
body fats moves up to 8%

98
Q

35- 38 weeks

A

circumference of belly bigger than head
skin is bluish pink
body fat 16%

99
Q

Parturition is another name for ?

A

Labour

Biology 235 (14 decks)

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