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Biology 235 > Chapter 29 Fetal Development and Childbirth > Flashcards

Chapter 29 Fetal Development and Childbirth Flashcards

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
The Blastocyst has 2 types of cells in it, what are they?
Inner Cell Mass -embryoblast cells are located internally and develop into embryo Trophoblast -outer layer of cells that forms a wall around the blastocyst
26
What will Trophoblast cells later develop into?
will develop into the outer chorionic sac surrounding the fetus
27
What happens around the 5th day?
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 .
28
Figure 29.2 shows the steps of blastocyst formation
There are 4 steps and 5 pictures
29
How long does the blastocyst hang out in the uterus before it decides to attach?
bout 2 day..... indecisive little snot! Then loosely attaches and by 7th day firmly attaches
30
Where does the blastocyst usually implant?
in either the posterior portion of the fundus or the body of the uterus. It turns with the inner cell mass toward the endometrium
31
What are the layers of the Decidua? What is the Decidua formerly known as?
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
32
What is the function of the Decidua Basalis?
– 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
33
What type of decidua is the endometrium that is in the uterus but not involved with the embryo?
Decidua Parietalis
34
Where is the Decidua Capsularis located?
is the portion of the endometrium located between the embryo and the uterine cavity
35
What is an ectopic pregnancy
- development of an embryo or fetus outside the uterine cavity usually in the Uterine tube Fatal to mom if not aborted
36
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?
amnion
37
What are the purposes of amniotic fluid?
serves as a shock absorber and regulates fetal body temperature, keep fetus hydrated, stops fetus from adhering between fetus and surrounding tissue
38
How is amniotic fluid created. This question was on at least 2 of the quizzes I took either in book or online.
first from maternal blood- later fetus contributes urine –
39
How is the yolk sac formed
– 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 –
40
What is the purpose of the yolk sac?
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
What membrane that surrounds the embyro becomes a prinicpal part of the placenta?
Chorin
42
How does the Chorin protect baby from Mom's immune response?
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
Figure 29.5 has nice summary of first week of development | Can you list the stages with time frame?
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
What forms the roof of the amniotic cavity and what forms the floor
The amnion forms the roof and epiblasts form the floor
45
When the amnion ruptures just before birth what is the fluid like?
Clear and runny like water.
46
Why is the yolk sac relatively unimportant in human development?
because fetus gets most of it's nutrients from the endometrium
47
What layers form the Chorion?
the extraembryonic mesoderm and 2 layers of the trophblast Chorion surrounds embryo and later the fetus
48
What are the main features of the 2nd week of development?
formation of the amnion, yolk sac, chorion and connecting stalk.
49
What are the main features of the 3rd week of development?
Gastrulation, neurulation, development of chorionic villi and placenta
50
What is gastrulation?
the bilaminar embryonic disc transforms into trilaminar ( 3 layers)embryonic disc
51
Describe the process of Gastrulation
Formation of the primitive streak which is a grove on the disc which establishes the head and tail , right and left sides
52
What are the primary Germ layers
they are the major embryonic tissues from which the various tissues and organs of the body develop. Forms after primitive streak appears
53
In primary Germ layers describe the 3 layers
Ectoderm Mesoderm Endoderm
54
Cells made of epithelia tissue (tightly packed cells) in the ECTOderm develop into what parts of the fetus?
develops into the epidermis of skin and nervous system.
55
Cells between the Epiblast and new endoderm are called what?
Mesoderm
56
What do cells in the mesoderm develop into
develops into muscles, bones, connective tissues and peritoneum
57
What do cells in the Endoderm develop into
– eventually becomes lining of the gastrointestinal tract, respiratory tract and other organs
58
How many types of embroyonic discs are there?
2 types , 2 and 3 layered disc made up of cells from hypoblast and epiblast cells
59
The process by which the neural plate and neural folds and neural tube are created is called?
Neurulation
60
What is the neurul groove?
the depressed area in between the neural folds in the neural groove
61
How is the neural fold created? And what does it develop into?
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
What is Lucuae
maternal blood filled spaces in the uterine wall created as embryonic tissue invades the uterine wall
63
What is Chorionic Villa?
fingerlike projections consist of chorion (syncytiotrophoblast surrounded by cytotrophoblast) that projects into the endometrial wall of the uterus
64
When do blood capillaries develop in the choronic villa
by the end of the 3rd week. these start to form at the end of the second week
65
When fetal blood capillaries (part of the chorion villa invade the lacuae, these 2 structures combine to form what?
Intervillious Spaces where chorionic villa is bathed in maternal blood
66
Do materal and fetal blood mingle?
This is strictly a look but don't touch situation. Fetal blood and maternal blood next mix
67
How does the fetal blood get the nutrients and O2 needed?
diffuse across cell membrance from the intervervillous spaces to the chorionic villa
68
What is the placenta?
the site of exchange of nutrients and wastes between the mother and fetus
69
What part of mom forms into the placenta?
Decidua basalis This has been in several questions. Often they use the wrong type of decidua, making that choice incorrrect
70
When does the placenta develop and what parts of the baby and mom form the placenta
Unique because it develops from 2 separate individuals. in the 12th week chorionic villa and decidua basalis pancake shape
71
What are the main functions of the placenta
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
Know what can go through the placenta and what is stopped by the placenta.
no go - microrganisms | can go - drugs, alcohol, viruses
73
Describe the umbilical cord it, components and purpose
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
When the placenta detaches from the uterus and is expelled after birth it's called the ?
After birth
75
What is the umbilicus
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
What is the fetal period?
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
Describe the embryo's growth in the 5th and 6th weeks
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
Describe embryo's growth in 7th and 8th weeks
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
What are the 3 stages of labour? This was a common question
Dilation - opening of the cervix to 10 cm Explusion - baby coming out Placental stage - delivery of placenta
80
Parturtion is another word for ?
Labour
81
Define Labour.
process by which the fetus is expelled from uterus through the vagina
82
What are the chemical changes that start labour?
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
What are the symptoms of true labour
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
Typically how long do the 3 stages of labour last?
Dilation 6 - 12 hour Explusion 10 min to several hours Placental - 5 to 30 min
85
What must happen in mom to move from dilation stage to expulsion stage?
Cervix must be 10 cm dilated
86
Why are uterine contractions after the delivery of the palcenta so important
contractions also constrict blood vessels that were torn during delivery (to stop bleeding) OXYCTOCIN is important here to keep Uterine contracting
87
Is the control of labour contractions a positive feedback cycle?
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
What stops the positive labour feedback cycle?
Baby's head moves past the cervix and no longer pushes on it.
89
When the uterus shrinks it is called ?
Involution
90
When does the embryos heart start beating?
within 4 weeks
91
Between 5 and 8 weeks, what develops in the embryo?
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
9 - 12 weeks fetus charateristics
``` 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
13-16 weeks
head is smaller than the rest of the body eyes and ears move to final positions lower limbs lengthen
94
17 - 20 weeks
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
21-25 weeks
head become even more porportionate to body weight gain is substantial skin is pink and wrinkled can survive from 24 weeks onward
96
26 - 29 weeks
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
30 -34
skin pink and smooth fetus moves to an upside down position body fats moves up to 8%
98
35- 38 weeks
circumference of belly bigger than head skin is bluish pink body fat 16%
99
Parturition is another name for ?
Labour

Biology 235 (14 decks)

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