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

Chapter 29 - Development and Inheritance Flashcards

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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
Q

What is implantation?

A

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

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26
Q

What is the decidua basalis?

A

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

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27
Q

What is the decidua capsularis?

A

Portion of the endometrium located between the embryo and the uterine cavity

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28
Q

What is an ectopic pregnancy?

A

Development of an embryo and fetus outside of the uterine cavity
- can occur in uterine tube, ovary, abdominal cavity or uterine cervix

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29
Q

Summarize the events of fertilization during the first week.

A
  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)
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30
Q

What hormone is an indicator of pregnancy?

A

hCG (Human chorionic gonadotropin)

- secreted by trophoblast

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31
Q

What is an amnion?

A

The innermost membrane that encloses the embryo

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32
Q

What is amniotic fluid?

A

The fluid surrounding a fetus within the amnion

  • initially maternal blood
  • fetus contributes by excreting urine
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33
Q

What is the function of amniotic fluid?

A
  • shock absorber
  • regulates fetal body temperature
  • prevents fetus from drying out
  • prevents adhesion between the skin of the fetus and surrounding tissues
34
Q

What are the functions of the yolk sac?

A
  • 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
Q

What does the chorion form?

A

Becomes principal embryonic part of the placenta

- structure of exchange between mother and fetus

36
Q

How does the chorion protect the embryo and fetus from immune responses of the mother?

A
  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
Q

What important hormone does the chorion produce?

A

hCG

38
Q

What important event occurs during the 3rd week of pregnancy?

A

Three primary germ layers are established

  • gastrulation
  • embryonic disc
39
Q

What are the three primary germ layers?

A
  1. Ectoderm - epidermis of skin and nervous system
  2. Mesoderm - muscles, bones, connective tissues
  3. Endoderm - GI tract, respiratory tract, organs
40
Q

What is the neural fold?

A

A structure that arises during neurulation in the embryonic development

41
Q

What is the neural groove?

A

Depressed mid-region of the neural fold

  • converts neural plate into neural tube
  • eventually forms spinal cord and brain
42
Q

What is neurulation?

A

Process by which the neural plate, neural folds and neural tube form

43
Q

What are chorionic villi?

A

Finger-like projections consist of chorion that projects into the endometrial wall of the uterus
- by the end of the 2nd week

44
Q

What unites to form the intervillous spaces?

A

Fetal blood capillaries within the chorionic villi project into the lacunae
- bathe the chorionic villi with maternal blood

45
Q

Does fetal blood and maternal blood mix?

A

NO!

  • the vessels do not join
  • oxygen and nutrients in mother’s blood diffuses across cell membranes into the capillaries of the villi
46
Q

What is the placenta?

A

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

  • also produces hormones to sustain the pregnancy
  • a protective barrier
47
Q

Why is the placenta unique?

A

B/c it develops from two separate individuals

- mother and fetus

48
Q

What are the two distinct parts of the placenta?

A
  1. Fetal portion: formed by chorionic villi

2. Maternal portion: formed by decidua basalis

49
Q

What is the function of the umbilical cord?

A

The connection between the placenta and the embryo

50
Q

What is the afterbirth?

A

The placenta when it detaches from the uterus

- after the birth of the baby

51
Q

What is the umbilicus?

A

Area when the umbilical cord was attached to the baby

  • scar tissue forms
  • the “navel” or belly button
52
Q

When is the fetal period of development?

A

9 weeks until birth

53
Q

What are the major events that occur during the fetal period of development?

A
  • 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
Q

During the first 3-4 months of pregnancy, what hormones is the corpus luteum secreting?

A

Progesterone and estrogens

  • maintain the lining of the uterus during pregnancy
  • prepare mammary glands to secrete milk
55
Q

What hormone does the placenta produce?

A

Progesterone and estrogens

- from 3rd month onwards

56
Q

What hormone does the chorion secrete?

A

hCG = human chorionic gonadotropin into the blood

- stimulates corpus luteum to secrete progesterone and estrogens

57
Q

What happens to the levels of progesterone and estrogens during the pregnancy?

A

Increase in quantities until the time of birth

58
Q

What is relaxin? Why is it important for pregnancy?

A

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
Q

What is the function of human chorionic somatomammotropin during pregnancy? (hCS)

A

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
Q

What is the function of the cortiotropin-releasing hormone (CRH)?

A
  • 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
Q

What are some anatomical and physiological changes that occur during pregnancy?

A
  • 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
Q

What is parturition?

A

Labor!

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

63
Q

What is true labor?

A

Begins when uterine contractions occur at regular intervals, usually producing pain

  • interval between shortens, contractions intensify
  • localized back pain, intensified by walking
64
Q

What is false labor?

A

Pain is felt in the abdomen at irregular intervals

- does not intensify and walking does not alter it

65
Q

What are the three stages of true labor?

A
  1. Stage of dilation
  2. Stage of expulsion
  3. Placental stage
66
Q

What is the stage of dilation?

A

First stage

  • lasts 6-12 hours
  • time from onset of labor to complete dilation of cervix
  • regular contractions of uterus
  • amniotic sac ruptures
67
Q

What is the stage of expulsion?

A

Second stage

  • 10 minutes to several hours
  • from complete cervical dilation to delivery of baby
68
Q

What is the placental stage?

A

Third stage

  • 5-30 minutes
  • after delivery until the placenta is expelled
69
Q

What are the respiratory adjustments that occur to the fetus/baby when it is born?

A
  • 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
Q

What are the cardiovascular adjustments that occur to the fetus/baby when it is born?

A
  • 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
Q

What is lacation?

A

Production and ejection of milk from the mammary glands

72
Q

What is the principal hormone in promoting milk production?

A

Prolactin

- secreted by anterior pituitary

73
Q

What hormone inhibits the effects of prolactin?

reason why a woman doesn’t produce milk during pregnancy

A

Progesterone inhibits the effects of prolactin

74
Q

What is the milk ejection reflex?

A

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
Q

What is milk ejection (let-down)?

A

Movement of milk from the alveoli of the mammary glands into the mammary ducts, where it can be suckled

76
Q

What is colostrum?

A

Cloudy fluid secreted by mammary glands during a late pregnancy
- not as nutritious as milk, it serves until the appearance of real milk

77
Q

What are some benefits of breast feeding?

A
  • 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
Q

What is female infertility?

A

Inability to conceive

- ovarian disease, obstruction of uterine tubes, uterus not prepared to received a fertilized ovum

79
Q

What is male infertility?

A

Inability to fertilize a secondary oocyte

- does not simply imply erectile dysfunction

80
Q

What is down syndrome (DS)?

A

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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