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Biology - Chapter 19-29 > Chapter 29 - Development and Inheritance > Flashcards

Chapter 29 - Development and Inheritance Flashcards

1
Q

What is developmental biology?

A

The study of the sequence of events from the fertilization of a secondary oocyte by a sperm cell to the formation of an adult organism

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2
Q

When does the embryonic period occur?

A

From fertilization through the 8th week

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3
Q

What is pregnancy?

A

A sequence of events that begins with ferilization, proceeds with implantation, embryonic development and fetal development
- end with birth 38-40 weeks later

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4
Q

What happens during fertilization?

A

Haploid sperm cell and haploid secondary oocyte merge into a single diploid nucleus

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5
Q

What is capacitation?

A

A series of functional changes that causes the sperm’s tails to beat more vigorously and prepare its plasma membrane to fuse with the oocyte’s plasma membrane

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6
Q

In order for fertilization to occur, what two layers must the sperm cell penetrate?

A
  1. Corona radiata - granulosa cells that surround the secondary oocyte
  2. Zona pellucida - glycoprotein layer between the corona radiata and the oocyte’s plasma membrane
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7
Q

What is the acrosomal reaction?

A

Release of the contents of the acrosome

- digest a path through the zona pellucida as the lashing sperm tail pushes the sperm cell forward

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8
Q

What is the acrosome?

A

Helmet-like structure that covers the head of a sperm

- contains several enzymes

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9
Q

What happens as a sperm cell fuses with the secondary oocyte?

A

Events that prevent polyspermy (fertilization by more than one sperm cell)

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10
Q

Describe fast block to polyspermy.

A

Once a sperm cell fuses with a secondary oocyte, the cell membrane of the oocyte depolarizes
- a depolarized oocyte cannot fuse with another sperm

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11
Q

What happens during slow block to polyspermy?

A

Depolarization (from fast block) stimulates exocytosis of molecules that inactivate ZP3 which harden the entire zona pellucida

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12
Q

What does the nucleus in the head of the sperm develop into?

A

The male pronucleus

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13
Q

What does the nucleus of the fertilized ovum develop into?

A

The female pronucleus

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14
Q

What happens during syngamy?

A

Fusion of the male and female pronucleus

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15
Q

What is a zygote?

A

A diploid cell (2n) resulting from the fusion of two haploid gametes
- a fertilized ovum

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16
Q

How do dizygotic (fraternal) twins occur?

A

Release of two secondary oocutes and the subsequent fertilization of each by different sperm
- may or may not be the same sex

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17
Q

How do monozygotic (identical) twins occur?

A

Develop from a single fertilized ovum

  • same genetic material, same sex
  • arise from separation of the developing cells into two embryos before 8 days have passed
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18
Q

What is the result of conjoined twins?

A

Separations that occur later than 8 days

- twins are joined together and share some body structures

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19
Q

What is cleavage and when does it occur?

A

Rapid mitotic cell division

  • begins about 24 hours after fertilization
  • completed in about 6 hours
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20
Q

What are blastomeres?

A

Progressively smaller cells produced by cleavage

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21
Q

What is a morula?

A

A solid sphere of cells

  • results from successive cleavage
  • still surrounded by the zona pellucida and is about the same size as the original zygote
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22
Q

What is a blastocyst?

A

Forms from the morula

  • once fluid enters the morula
  • forms a blastocyst cavity
  • has hundreds of cells, about the same size as original zygote
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23
Q

During the formation of the blastocyst, what are the two distinct cell populations that arise?

A
  1. Embryoblast (inner cells mass) - internal layer and develops into the embryo
  2. Trophoblast - outer superficial layer of cells, develops into outer chorionic sac that surrounds fetus
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24
Q

How long does the blastocyst remain in the uterine cavity before attaching to the uterine wall?

A

About 2 days

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25
What is implantation?
Blastocyst LOOSELY attaches to the endometrium - about 6 days after fertilization Balstocyst BURROWS into endometrium and becomes surrounded by it - about 7 days after fertilization
26
What is the decidua basalis?
Portion of the endometrium between the embryo and the stratum basalis of the uterus - provides a large amount of glycogen and lipids for the developing embryo and fetus
27
What is the decidua capsularis?
Portion of the endometrium located between the embryo and the uterine cavity
28
What is an ectopic pregnancy?
Development of an embryo and fetus outside of the uterine cavity - can occur in uterine tube, ovary, abdominal cavity or uterine cervix
29
Summarize the events of fertilization during the first week.
1. Fertilization occurs (12-24 hours after ovulation) 2. Cleavage (completed 30 hours after fertilization) 3. Morula (3-4 days after fertilization) 4. Blastocyst (4.5-5 days after fertilization), in uterine cavity 5. Implantation (6 days after fertilization)
30
What hormone is an indicator of pregnancy?
hCG (Human chorionic gonadotropin) | - secreted by trophoblast
31
What is an amnion?
The innermost membrane that encloses the embryo
32
What is amniotic fluid?
The fluid surrounding a fetus within the amnion - initially maternal blood - fetus contributes by excreting urine
33
What is the function of amniotic fluid?
- shock absorber - regulates fetal body temperature - prevents fetus from drying out - prevents adhesion between the skin of the fetus and surrounding tissues
34
What are the functions of the yolk sac?
- supplies nutrients to the embryo during the second and third weeks of development - source of blood cells (3-6 weeks) - contains first cells that will develop into gonads - forms part of the gut - shock absorber - helps prevent drying out
35
What does the chorion form?
Becomes principal embryonic part of the placenta | - structure of exchange between mother and fetus
36
How does the chorion protect the embryo and fetus from immune responses of the mother?
1. Secretes proteins that block antibody production by the mother 2. Promotes the production of T lymphocytes that suppress the normal immune response in the uterus
37
What important hormone does the chorion produce?
hCG
38
What important event occurs during the 3rd week of pregnancy?
Three primary germ layers are established - gastrulation - embryonic disc
39
What are the three primary germ layers?
1. Ectoderm - epidermis of skin and nervous system 2. Mesoderm - muscles, bones, connective tissues 3. Endoderm - GI tract, respiratory tract, organs
40
What is the neural fold?
A structure that arises during neurulation in the embryonic development
41
What is the neural groove?
Depressed mid-region of the neural fold - converts neural plate into neural tube - eventually forms spinal cord and brain
42
What is neurulation?
Process by which the neural plate, neural folds and neural tube form
43
What are chorionic villi?
Finger-like projections consist of chorion that projects into the endometrial wall of the uterus - by the end of the 2nd week
44
What unites to form the intervillous spaces?
Fetal blood capillaries within the chorionic villi project into the lacunae - bathe the chorionic villi with maternal blood
45
Does fetal blood and maternal blood mix?
NO! - the vessels do not join - oxygen and nutrients in mother's blood diffuses across cell membranes into the capillaries of the villi
46
What is the placenta?
The site of exchange of nutrients and wastes between the mother and fetus - also produces hormones to sustain the pregnancy - a protective barrier
47
Why is the placenta unique?
B/c it develops from two separate individuals | - mother and fetus
48
What are the two distinct parts of the placenta?
1. Fetal portion: formed by chorionic villi | 2. Maternal portion: formed by decidua basalis
49
What is the function of the umbilical cord?
The connection between the placenta and the embryo
50
What is the afterbirth?
The placenta when it detaches from the uterus | - after the birth of the baby
51
What is the umbilicus?
Area when the umbilical cord was attached to the baby - scar tissue forms - the "navel" or belly button
52
When is the fetal period of development?
9 weeks until birth
53
What are the major events that occur during the fetal period of development?
- organs grows and differentiate - rate of body growth is remarkable - less vulnerable to the damaging effects of drugs, radiation, and microbes than it was as an embryo
54
During the first 3-4 months of pregnancy, what hormones is the corpus luteum secreting?
Progesterone and estrogens - maintain the lining of the uterus during pregnancy - prepare mammary glands to secrete milk
55
What hormone does the placenta produce?
Progesterone and estrogens | - from 3rd month onwards
56
What hormone does the chorion secrete?
hCG = human chorionic gonadotropin into the blood | - stimulates corpus luteum to secrete progesterone and estrogens
57
What happens to the levels of progesterone and estrogens during the pregnancy?
Increase in quantities until the time of birth
58
What is relaxin? Why is it important for pregnancy?
Increases the flexibility of the pubic symphsis - helps dilate the cervix during labor - produced by the corpus luteum and then later by the placenta
59
What is the function of human chorionic somatomammotropin during pregnancy? (hCS)
Produced by the chorion of the placenta - helps prepare mammary glands for lacation - enhance maternal growth by increasing protein synthesis - decreases glucose use and increases fatty acid use for ATP production - regulates metabolism for mother and fetus
60
What is the function of the cortiotropin-releasing hormone (CRH)?
- part of the "clock" that establishes the timing of the birth - increases towards end of pregnancy - increases the secretion of cortisol (needed for maturation of fetal lungs and production of surfactant) - produced by the placenta
61
What are some anatomical and physiological changes that occur during pregnancy?
- uterus fills abdominal cavity - weight gain due to the fetus/amniotic fluid/placenta/uterine enlargement/increased total body water - breast enlargement - stroke volume increases, cardiac output increases - increased respiratory functions - increased appetite - uterus increases in size - changes in skin
62
What is parturition?
Labor! | - process by which the fetus is expelled from the uterus through the vagina
63
What is true labor?
Begins when uterine contractions occur at regular intervals, usually producing pain - interval between shortens, contractions intensify - localized back pain, intensified by walking
64
What is false labor?
Pain is felt in the abdomen at irregular intervals | - does not intensify and walking does not alter it
65
What are the three stages of true labor?
1. Stage of dilation 2. Stage of expulsion 3. Placental stage
66
What is the stage of dilation?
First stage - lasts 6-12 hours - time from onset of labor to complete dilation of cervix - regular contractions of uterus - amniotic sac ruptures
67
What is the stage of expulsion?
Second stage - 10 minutes to several hours - from complete cervical dilation to delivery of baby
68
What is the placental stage?
Third stage - 5-30 minutes - after delivery until the placenta is expelled
69
What are the respiratory adjustments that occur to the fetus/baby when it is born?
- after delivery, oxygen is no longer delivered by the mother, CO2 is no longer removed - it builds up in the blood - rising CO2 levels, stimulate medulla oblongata causing the respiratory muscles to contract - baby draws his first breath
70
What are the cardiovascular adjustments that occur to the fetus/baby when it is born?
- closure of the foramen ovale between the atria of the fetal heart - ductus arteriosus shuts off once lungs begin to function - when umbilical cord is severed, ductus venosus collapses, venous blood from the viscera of the fetus flows into the hepatic portal vein
71
What is lacation?
Production and ejection of milk from the mammary glands
72
What is the principal hormone in promoting milk production?
Prolactin | - secreted by anterior pituitary
73
What hormone inhibits the effects of prolactin? | reason why a woman doesn't produce milk during pregnancy
Progesterone inhibits the effects of prolactin
74
What is the milk ejection reflex?
Oxytocin causes the release of milk into the mammary ducts | - stimulation of touch receptors in the nipple initiates sensory nerve impulses that are relayed to the hypothalamus
75
What is milk ejection (let-down)?
Movement of milk from the alveoli of the mammary glands into the mammary ducts, where it can be suckled
76
What is colostrum?
Cloudy fluid secreted by mammary glands during a late pregnancy - not as nutritious as milk, it serves until the appearance of real milk
77
What are some benefits of breast feeding?
- beneficial cells (white blood cells) - beneficial molecules (antibodies/antimicrobial) - decreased incidence of diseases later in life - miscellaneous benefits (supports growth, enhances intellectual and neurological development, fosters mother-infant relationships)
78
What is female infertility?
Inability to conceive | - ovarian disease, obstruction of uterine tubes, uterus not prepared to received a fertilized ovum
79
What is male infertility?
Inability to fertilize a secondary oocyte | - does not simply imply erectile dysfunction
80
What is down syndrome (DS)?
Disorder characterized by three rather than two copies of chromosome 21 - mental retardation, physical development, kidney defects, suppressed immune system, malformations of heart, ears, hands and feet

Biology - Chapter 19-29 (11 decks)

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