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613: Human Development and the Life Cycle > Preparation for Pregnancy > Flashcards

Preparation for Pregnancy Flashcards

1
Q

Gametogenesis

A

The process in which cells undergo meiosis to form gametes

  • Oogenesis in females
  • Spermatogenesis is males
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2
Q

4 Phases of Gametogensis

A

(1) the extraembryonic origin of the germ cells and their migration into the gonads
(2) An increase in the number of germ cells by mitosis
(3) A reduction in chromosomal number by meiosis
(4) Structural and functional maturation of the eggs and spermatozoa

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3
Q

Primordial germ cells

A

Cells are responsible for differentiating into eggs and sperm
* Earliest recognizable precursors of gametes

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4
Q

When does oogenesis begin? spermatogenesis?

A 
Females = before birth
Males = at puberty
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5
Q

Describe what happens during the first phase of the Gametogenesis

A

Primordial germ cells arise outside the gonads and migrate into the gonads during early embryonic development

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6
Q

Describe the migratory path of PGC’s

A

They exit from the yolk sac into the hindgut epithelium and then migrate through the dorsal mesentery until they reach the primordia of the gonads (initially at the level of L1)

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7
Q

Obstetric age vs. scientific age

A

Obstetric:
- begins at the beginning of the last menstrual cycle
- 40 weeks = 280 days
Scientific:
- Begins when the sperm actually penetrates the egg
-38 weeks = 266 days

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8
Q

When must fertilization take place to create a viable pregnancy?

A

Within 24 hours of ovulation otherwise the egg degenerates

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9
Q

4 Actions during development

A
  • Growth
  • apoptosis
  • differentiation
  • organization
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10
Q

What happens during growth?

A

(1) Hypertrophy
- increased cell size
(2) cell proliferation
- increase cell number
(3) accretion
- Increase extracellular matrix

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11
Q

What is apoptosis?

A

Programmed cell death

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12
Q

Describe the process of differentiation

A

The process by which a cell changes from a multipotent state of fundamental specificity

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13
Q

What happens during organization phase of development?

A

The fate of cells is sometimes based on their 3-D organization

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14
Q

What is morphogenesis?

A

The origin and development of landforms and other structures

* For example as shape changes so does function

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15
Q

When do the embryonic and fetal periods begin and end?

A

Embryonic Period:
- From fertilization through the end of the eighth week
Fetal Period:
- From the ninth week to birth (approximately 38 weeks after fertilization or 40 weeks after the last period)

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16
Q

How is a nine month pregnancy typically split?

A

Into three trimesters

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17
Q

At how many weeks (scientific age) does a fully formed fetus occur? how long is it?

A

About eight weeks and it is approximately 3 cm long

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18
Q

At how many weeks (obstetric age) is there a 50% survival rate?

A

24 wks

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19
Q

What is CR?

A

Crown rump length

*from the top of the skull to the gluteus maximus

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20
Q

Given CR length how can gestational age be approximated?

A

Age in weeks =CR length + 6.5

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21
Q

Two major parts of the uterus

A
  • Body

- cervix

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22
Q

Describe the uterine tubes

A
  • Approximately 10 cm long and 1 cm in diameter.

- extend laterally from the horns of the uterus and into the peritoneal cavity at its distal end

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23
Q

Where does fertilization occur?

A

In the ampulla of the uterine tube

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24
Q

What is a morula?

A

A solid ball of cells resulting from division of a fertilized ovum and from which a blastula is formed

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25
Q

How many cells are allowed to penetrate the egg?

A

Only one

- once the zona pellucida is penetrated it becomes impervious to other sperm

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26
Q

Fertilization creates a _______ cell called a _______.

A

Totipotent

Zygote

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27
Q

Define totipotent

A

Capable of giving rise to any cell type or a complete embryo

28
Q

Of the 23 pairs of chromosomes how many are autosomes and how many are allosomes?

A

22 pairs of autosomes and 1 pair of sex chromosomes (allosomes)

29
Q

Mitosis vs. meiosis

A

Mitosis is the process whereby one cell divides giving rise to two daughter cells each with 46 chromosomes
Meiosis is the cell division that takes place in the germ cells to generate male and female gametes. This process requires to 2 cell divisions to reduce the number of chromosomes from 46 to the haploid number of 23

30
Q

How many sperm form from one primary spermatocyte?

A

4

31
Q

How many mature oocytes result from maturation of a primary oocyte?

A

1

32
Q

Three importances of meiosis

A

(1) Provides consistency of the chromosome number from generation to generation by making diploid cells haploid
(2) allows random assortment of maternal and paternal chromosomes between gametes
(3) relocates segments of maternal and paternal chromosomes by crossing over of chromosome segments which “shuffles” the genes and produces recombination

33
Q

Describe to sperm features that are required for fertilization

A

1) The head has an acrosomal full of enzymes to help penetrate the ovum
2) Mitochondria in the spermatozoa provide energy that allows them to swim upstream in the uterus and against contraction of the uterine tube

34
Q

What do the spermatozoa contribute to the ovum?

A

DNA

- this includes the mitochondrial DNA

35
Q

Where does final maturation of the spermatozoa occur?

A

Epididymis

36
Q

Where are sperm deposited?

A

In the posterior fornix of the cervix

37
Q

Describe it which glands and hormones control the ovarian cycle

A

The hypothalamus produces gonadotropin releasing hormone (GnRH) which acts on the anterior lobe of the pituitary gland. This in turn secretes follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These two gonadotropins stimulate and control cyclic changes in the ovary

38
Q

What does FSH do?

A

It is the gonadotropin that stimulates the development of ovarian follicles and the production of estrogen by the follicular cells

39
Q

What does LH do?

A

It serves as the “trigger” for ovulation (release of the secondary oocyte) and stimulates the follicular cells and corpus luteum to produce progesterone

40
Q

What effect does LH have on the endometrium during pregnancy?

A

Implantation causes the pituitary gland to continue to release LH which signals to the corpus luteum to continue to secrete progesterone and estrogen for the upkeep of the uterine wall

41
Q

What happens to the uterine wall if implantation does not take place?

A

LH is not released so the corpus luteum does not continue to release estrogen and progesterone and the uterine wall is shed

42
Q

When does implantation typically occur and where?

A

In the posterior wall of the uterus on day six

43
Q

What must occur for the trophoblast (Outer cell mass of the blastocyst) to implant?

A

The zona pellucida must degenerate

44
Q

What is the menstrual cycle?

A

The time during which that oocyte matures, is ovulated, and enters the uterine tube

45
Q

Name of the five phases of the ovarian cycle

A

1) Menstrual phase
2) proliferative phase
3) ovulation
4) secretory (luteal) phase
5) ishemic phase

46
Q

Describe the menstrual phase

A

The first phase of the menstrual cycle during which the lining of the uterus is shed

47
Q

Describe the proliferative phase

A

The second phase of the menstrual cycle in which the endometrium regenerates and thickens

48
Q

Describe ovulation

A

The third phase of the menstral cycle in which an ovum is released from the ovary

49
Q

Describe the secretory or luteal phase

A

The fourth phase of the menstrual cycle in which the corpus luteum secretes progesterone which prepares the endometrium for implantation

50
Q

Describe the Ishemic Phase

A

The last phase of the menstrual cycle in which the lining of the uterus disintegrates and prepares to be shed

51
Q

How many days is the average menstrual cycle?

A

28 fays

52
Q

How long is the menstrual phase and on what days does it begin and end?

A

1-4

4 days long

53
Q

How long is the Proliferative phase and on what days does it begin and end?

A

5-13

9 days long

54
Q

How long is the ovulation phase and on what days does it begin and end?

A

13-16

4 days long

55
Q

How long is the Luteal phase and on what days does it begin and end?

A

16-28

13 days long

56
Q

How long is the Ischemic phase and on what days does it begin and end?

A

27-28

2 days long

57
Q

The endometrium is a ______ of the ovarian cycle. Why?

A

“Mirror”

It responds in a consistent manner to the fluctuating concentrations of Gonadotropic and ovarian hormones

58
Q

How can a woman tell if she is ovulating?

A

Basal body temperature increases 0.5°C

59
Q

At approximately what day does the blastocyst implant in the endometrium?

A

In the sixth day of the luteal phase which is day 20 of the 28th day cycle

60
Q

What roles do FSH and LH play in males?

A

FSH affects the Sertoli cells which stimulate the process of spermatogenesis to occur.
LH triggers the Leydig cells of the testes to produce and secrete testosterone, which is essentially needed for sperm production

61
Q

Describe human development all the way from fertilization up to birth

A

1) Zygote which is a single pluripotent cell until 8 cells
2) Morula which is a solid ball of 16 cells
3) Blastocyst which is when the zygote divides to 32 cells
4) Embryo which is the third week through the eighth week
5) fetus which is the ninth week until birth

62
Q

When is a morula considered a blastocyst?

A

When a cavity appears in the morula

63
Q

What are the three parts to the morula and what will they become?

A

1) Intercell mass which will become the embryo
2) Blastocyst cavity Will become the blastocoel
3) Outer Cell mass which will become the trophoblast and will contribute to the placenta

64
Q

At the end of week one what do we have?

A 
Two layers to the embryo: 
   - epiblast
   - hypoblast
Two layers of the trophoblast
   - cytotrophoblast
   - syncytioyrophoblast
Two cavities 
   - amniotic cavity
   - blastocyst cavity (aka the primary yolk sac)
65
Q

Describe the syncytioyrophoblast

A

The outer layer of the trophoblast that invades the endometrial epithelium and underlying tissue
* It also secretes hCG to maintain the corpus luteum

66
Q

By the end of the first week the blastocysts is superficially implanted in the endometrium with the help of the _____ and the _____.

A

Syncytiotrophoblast

Hypoblast

67
Q

What percent of pregnancies end in spontaneous abortion?

A

50%

613: Human Development and the Life Cycle (7 decks)

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