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Chapter 5 Flashcards

1
Q

How many chromosomes results from meiosis?

A

23 (22 autonomies and 1 sex chromosome)

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2
Q

What is crossing over?

A

Each chromosome exchanges some material with its mate to allow variation in genetic material

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3
Q

What are primary follicles?

A

A layer of follicular cells that surround primary oocytes

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4
Q

Throughout childhood, what stage are a females eggs at?

A

The primary follicle and its oocyte, which still contains 46 chromosomes remain dormant

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5
Q

When are primary germ cells produced in females?

A

During about 30th week of fetal life

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6
Q

when are primary germ cells produced in males?

A

Continuously after puberty

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7
Q

Number of mature germ cells that develop from each primary cell in males and females?

A

Females: 1
Males: 4

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8
Q

When does the primary oocyte complete its first meiotic division, which began in fetal life?

A

Shortly before ovulation (the result is a secondary oocyte containing 23 chromosomes)

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9
Q

When does the second meiotic division of an oocyte occur?

A

Is prolonged and remains suspended in metaphase until fertilization occurs

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10
Q

Two layers that surround the mature ovum when it’s released from the ovary

A

Zona pellucida
The cells of the corona radiata

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11
Q

How long does spermatogenesis take?

A

Approx 70 days

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12
Q

Hormones that cause oocytes to begin to mature before ovulation

A

FSH & LH

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13
Q

Sac the maturing oocyte is contained in before ovulation

A

Graafian follicle

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14
Q

Hormones the Graafian follicle produces
Why?

A

Estrogen and progesterone
To prepare the endometrium for a possible pregnancy

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15
Q

After the mature ovum and its surrounding cells are released onto the surface of the ovary, what does the collapsed follicle transform into and what is its purpose?

A

Corpus luteum
Maintains high estrogen and progesterone secretion which is necessary to finish preparing uterine lining for fertilized ovum

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16
Q

Where does fertilization normally occur?

A

In the distal third of the Fallopian tube (ampulla) near the ovary

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17
Q

How long after release from the ovary does it take for the ovum to enter the uterus?

A

4 days

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18
Q

Function of seminal fluid

A

Nourishes and protects sperm from acidic environment of the vagina

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19
Q

What is capacitation?

A

Changes sperm undergo to enable one of them to penetrate the protective layers surrounding the ovum

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20
Q

When has fertilization officially occurred?

A

When one spermatozoon enters the ovum and the two neuclei containing the parents’ chromosomes merge

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21
Q

When is the preembryonic period?

A

First 2 weeks after conception

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22
Q

What occurs during the preembryonic period?

A

Initiation of cell division (conceptus)
Zygote enters the uterus (4th day after fertilization)
Implantation in the decidua (what the endometrium is now called)
Zygote secretes hCG to signal woman’s body that pregnancy has begun

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23
Q

Cells and membranes resulting from fertilization of the ovum

A

Conceptus

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24
Q

When the conceptus is a solid ball of 16 cells

A

Morula

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25
After the blastocyst enters the uterus, how long does it stay before it implants?
Approx 2-4 days
26
Another name for implantation
Nidation
27
When does implantation occur?
Approx 6-10 days after fertilization
28
How is the decidua maintained?
Zygote secretes hCG to signal pregnancy to woman’s body Production of hCG by conceptus causes corpus luteum to continue secretion of estrogen and progesterone until placenta takes over this function
29
Why is the upper uterus the best place for implantation?
Richly supplied with blood Lining is thicker, preventing placenta from attaching too deeply Limits blood loss after birth because of strong interlacing muscle fibers in this area
30
What are primary chorionic villi?
Tiny projections of surface of the conceptus that extend into the endometrium (the decidua now) and eventually form the fetal side of the placenta
31
What forms the maternal side of the placenta?
Decidua basalis (what the endometrium was)
32
When is the embryonic period?
From the beginning of the 3rd week through the 8th week after conception
33
What occurs during the embryonic period?
Basic structures of all major body organs are completed
34
When is the fetal period?
Begins 9 weeks after conception and ends with birth
35
Define embryo
Developing baby from the beginning of the third week through the 8th week after conception
36
When are structures of the baby most vulnerable to damage from teratogens and why?
During the embryonic period (3rd - 8th week) because structures are developing so rapidly
37
What is considered full term?
36-40 weeks of fertilization age 38-42 weeks of gestational age
38
Major developments during weeks 9-12
Eyes close at 9 weeks Intestines move from umbilical cord to abdomen at 11 weeks Blood formation shifts form the liver to the spleen by end of week 12 Fetus begins producing urine Fetal gender can be determined by end of week 12
39
Developments during weeks 13-16
Head becomes more proportionate to body as body grows rapidly in length Movements strengthen, mother may be able to detect them Ears become in line with the eyes
40
Developments during weeks 17-20
Fetal movements feel like fluttering Vernix covers skin Lanugo covers body Brown fat deposited
41
Developments during weeks 21-24
Skin is still translucent Lungs begin to produce surfactant (actually begins at 20 weeks and continues throughout) Capillary network surrounding alveoli increasing
42
Developments during weeks 25-28
Lungs, pulmonary capillaries, and CNS more mature, survival is more likely Subcutaneous fat deposited under skin Skin gradually becomes less red Eyes reopen Head hair is abundant Blood formation shifts from spleen to bone marrow *Fetus usually assumes head down position
43
Developments during weeks 29-32
Skin is pigmented according to race Toenails present, fingernails extend to fingertips More subcutaneous fat which rounds body contours Chances of survival are good, esp with specialized neonatal care
44
Developments during weeks 33-38
Fetus mainly gaining weight Lanugo may be present on forehead, upper back, upper arms Vernix remains in major creases Testes in scrotum Breast tissue palpable b/c of maternal hormone effects
45
List the auxiliary structures that sustain pregnancy and permit normal prenatal development
Placenta Umbilical cord Fetal membranes
46
Which side of the placenta is which?
Smooth side is toward fetus Rough side is toward uterus
47
What are the intervillous spaces of the placenta?
Where exchange of substances between mother and fetus occurs Maternal blood washes over chorionic villi containing fetal vessels and returns to maternal circulation
48
3 reasons that explain how the fetus can thrive in the low-oxygen environment
- fetal hemoglobin can carry more oxygen - fetus has higher hemoglobin level so can cherry more oxygen - low carbon dioxide partial pressure (Pco2) levels allow hemoglobin to carry more oxygen
49
Major energy source for fetal growth
Glucose
50
Functions of the placental hormone, human placental lactogen
Promotes normal nutrition and growth of the fetus Promotes maternal breast development for lactation Decreases maternal insulin sensitivity and glucose use, making more glucose available for the fetus
51
Steroid hormones secreted by the placenta
Progesterone and estrogen
52
Two fetal membranes
Amnion (inner membrane) Chorion (outer membrane)
53
How does the amniotic fluid protect the fetus
- cushions against impacts - maintains stable temperature - promotes normal prenatal development (Symmetric development, prevents membranes from adhering to developing fetal parts, allows movement)
54
Abnormally small amount of amniotic fluid
Oligohydramnios
55
Too much amniotic fluid
Hydramnios
56
Functions of the arteries in the umbilical cord
Carry deoxygenated blood and waste products away from the fetus to the placenta
57
Function of the vein in the umbilical cord
Carries oxygenated blood and nutrients from the placenta back to the fetus
58
What is Wharton’s jelly?
Soft substance in umbilical cord that prevents obstruction
59
Three shunts in the fetal circulatory system
Ductus venous Foramen ovale Ductus arteriosus
60
Function of the three shunts in the fetal circulatory system
Allow blood with the highest oxygen concentration to be sent to the fetal heart and brain
61
What does the ductus venous connect to?
The inferior vena cava (skips the liver)
62
What is the Foramen ovale?
Flap valve in septum between right and left atria of fetal heart
63
What does the ductus arteriosus connect to?
Connects the pulmonary artery and the descending aorta during fetal life
64
What happens to the Foramen ovale after birth?
When the infant breathes air, the Foramen ovale closes
65
What happens to the ductus arteriosus after birth?
It constricts as the arterial oxygen levels rise
66
What happens to the ductus venous after the baby is born?
It constricts when the flow of blood from the umbilical cord stops Becomes a ligament
67
How are monozygotic twins conceived?
By a single ovum and spermatozoon that divide into two
68
How are dizygotic twins conceived?
Arise from two ova fertilized by different sperm

OB (11 decks)

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