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Renal and Endocrine Biology > REB 15. Gametogenesis, Implantation, Foetal Membranes > Flashcards

REB 15. Gametogenesis, Implantation, Foetal Membranes Flashcards

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1
Q

What are gametes? Give examples.

A

Gametes are the specialized reproductive cells.

Females = Ovum 
Males = Sperm
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2
Q

What is gametogenesis? What process does it go through? What cells are involved?

A

Gametogenesis: the creation of gametes
- e.g spermatozoa and ova

Gametes are formed from Germ Cells

  • Germ Cells are DIPLOID
  • Germ Cells undergo MEIOSIS
  • Germ Cells become HAPLOID (Gametes)
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3
Q

How many pairs of chromosomes are the same in males and females?

A

22 pairs

- 1 unique pair (sex chromosomes)

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4
Q

What is sexual reproduction?

A

It is where 2 distinct types of specialized reproductive cells (gametes) fuse together

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5
Q

What are primordial germ cells (PGCs)? Where are they created and where do they end up?

A

PGC’s are created in the YOLK SAC

PGC’s migrate to the gonadal ridge (the gonadal ridge becomes the male + female gonads - ovaries/testes)

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6
Q

What is a teratoma? What is a possible cause?

A
  • teratoma contains a variety of tissue (bone, hair, muscle, gut epithelia and others…)
  • thought to contain pluripotent stem cells that can differentiate into any of the 3 germ layers or their derivatives

possible cause: PGCs that have strayed from their migratory path

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7
Q

What happens in each stage of Meiosis I?

A

PROPHASE I:

  • 46 homologous pairs (92 chromosomes - duplicated themselves in interphase)
  • crossing over (exchange of genetic material) between homologous pairs

METAPHASE I:
- the chromosomes align along the equatorial plane and the spindle fibres

ANAPHASE I:
- homologous chromosomes pulled to opposite poles of cell

TELOPHASE I:
- the cell pinches off to create 2 new cells

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8
Q

At what stage of meiosis does crossing over take place?

A

Prophase I

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9
Q

What is non-disjunction? What is an example?

A

When there normal separation of chromosomes in meiosis does not occur

  • trisomy (3 chromosomes)
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10
Q

What happens when there is not the normal separation of chromosomes in meiosis?

A

Non-Disjunction

- can lead to miscarriage or illnesses

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11
Q

What is Trisomy 21?

A

down syndrome

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12
Q

What is Prader-Wili syndrome?

A

it occurs when there is a microdeletion on the paternal chromosome 15

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13
Q

What is Turner Syndrome?

A

it is when the child (female) is born with only 1 X chromosome

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14
Q

What is oogenesis? Explain the process.*

A

Oogenesis: the production or development of an ovum

[1] PGCs differentiate (undergo mitosis) to create oogonia
[2] oogonia give rise to primary oocytes
[3] oocytes start meiosis before birth, but are stopped in meiosis I (prophase I)
[4] meiotic arrest
[5] at puberty, meiosis continues and produces 1 ovum each month

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15
Q

What is meiotic arrest in oogenesis?

A

oocytes begin meiosis before birth, but are stopped in meiosis I (prophase I) until puberty

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16
Q

What are the 2 main processes involved in the creation of viable sperm?

A

[1] Spermatogenesis - formation of spematids

[2] Spermiogenesis - maturation of spermatids into spematazoa

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17
Q

Explain the steps involved in spermatogenesis.

A
  • germ cells (PGCs) differentiate into spermatagonia through mitosis
  • spematogonis give rise to primary spermatocytes through mitosis
  • primary spermatocytes give rise to secondary spermatocytes through meiosis
  • secondary spermatocytes give rise to spermatides
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18
Q

Where does spermatogenesis occur?

A

the haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis

19
Q

What is involved in spermiogenesis?

A
  • spermatids are turned into spermatozoa
  • some changes are:
  • — formation of acrosome
  • — condensation of nucleus
  • — formation of neck, middle piece + tail
  • — shedding of most of cytoplasm
20
Q

What is Mittelscherz?

A

the pain a woman may feel on one side, once a month, while she’s ovulating (midway through the cycle - day 14)

21
Q

What is Menarche age?

A

it is the first occurrence of menstruation (age 8 to 14)

22
Q

What is menopause?

A

stopping of period

- occurs around age 45 to 55

23
Q

What are the 3 distinct phases of the menstrual cycle? Explain the phases.

A

[1] Menstrual Phase

  • Day 1 is the first day of menstrual bleed
  • period

[2] Proliferative Phase
- the endometrium thickens, blood vessels + glands develop

[3] Secretory Phase

  • the corpus luteum secretes estrogen + progesterone
  • progesterone stimulates glands to secrete substances that maintain the endometrium
24
Q

What happens during/after the secretory phase if pregnancy does not occur?

A

then menstrual bleeding takes place and endometrium sheds

25
Q

What happens during/after the secretory phase if pregnancy occurs?

A
  • implantation of the blastocyst
  • HCG (human chorionic gonadotropic hormone) maintains the corpus luteum in the ovary
  • the corpus luteum stimulates estrogen + progesterone
  • an increase in progesterone leads to endometrium thickening
26
Q

Where does fertilization occur?

A

ampulla of the fallopian tube

27
Q

What is the blastocyst? What are some defining characteristics?

A

Blastocyst: a hollow ball of cells

Characteristics:

  • outer trophoblast
  • inner cell mass
  • fluid filled cavity (blastocoel)
  • — this happens when fluid penetrates through zona pellucida of morula
  • NO zona pellucida
28
Q

What is the function of the trophoblast?

A
  • forms the outer layer of a blastocyst

- it penetrates the endometrum of the uterus wall

29
Q

What are the 2 parts that the trophoblast differentiates into?

A

[1] Syncythiotrophoblastic Cells

[2] Cytotrophoblast Cells

30
Q

What does the trophoblast secrete?

A

it secretes Human Chorionic Gonadotropin hormone (HCG)

  • when HCG is detectable in the urine/blood, this is a positive pregnancy test
31
Q

What do stromal cells of the uterine wall become?

A

decidual cells (the decidua)

32
Q

What is the decidua?

A

a thick layer of modified mucous membrane that lines the uterus during pregnancy

  • remains through the first trimester
  • after that, it becomes the placenta
33
Q

What is the chorion?

A
  • the outermost foetal membrane

- comes from trophoblast layer

34
Q

What is the amnion?

A
  • chorion + amnion make up and contain the amniotic sac

- they fuse and burst just before labour (breaking of the waters)

35
Q

What is the yolk sac?

A
  • the allantois and yolk sac make up the umbilical cord
36
Q

What are the functions of foetal membranes?

A
  • contain and protects the embryo/foetus
  • function in nutrition and collection of waste from the foetus
  • help develop the blood + oxygen supple of the foetus
  • involved in signalling between maternal decidua and foetus
37
Q

What is an important function that the outer syncythiotrophoblast layer does? Explain the steps involved.

A
  • involved in blood exchange between foetus and mother

[1] develops projections into the endometrium
[2] small spaces within the layer form = lacunae
[3] the syncythiotrophoblast invades endometrial blood vessels + glands
[4] lacunae become filled with blood + secretions
[5] lacunae coalesce to produce primitive maternofoetal circulation
— maternal + fetal blood do not mix
— all exchanges occur between the 2 bloodstreams take place across an extremely thin barrier

38
Q

What is an important function that the inner cytotrophoblast layer does? Explain the steps involved.

A
  • it is important for gas exchange

[1] cytotrophoblasts project into the syncythiotrophoblasts - primary villi develop
[2] secondary villi develop
[3] tertiary villi develop

39
Q

Where is the umbilical cord located? What does it contain?

A
  • goes between the placenta and fetus
  • formed by 5th week of development

contains:

    • 2 arteries (carrying deoxygenated blood)
    • 1 vein (carrying oxygenated blood)
    • in loose connective tissue (Wharton’s Jelly)
40
Q

What is Wharton’s Jelly?

A

a gelatinous substance that provides insulation and protection within the umbilical cord

41
Q

What are the functions of the placenta?

A
  • nutrient uptake
  • gas exchange via the mother’s blood supply
  • secretes progesterone and estrogen
  • thermo-regulation
  • waste elimination
  • protects the fetus against internal infection
  • it metabolizes a number of substances
42
Q

List the clinical problems that can arise from the placenta

A
  • Placenta Praevia
  • Placenta Abruptia
  • Placental Degradation
  • Placenta Accretia
  • Hydatidyform Mole
  • — the placenta forms a mass with little/no fetal tissue
  • — secretes high levels of human chorionic gonadotrophin (HCG)
  • — may become carcinogenic (2%)
  • — paternal genes only
43
Q

What is In-Vitro Fertilization (IVF)? Explain the process.

A

IVF = a type of assisted reproduction

  • ovaries hyperstimulated and ova collected under general anaesthetic
  • sperm is collected from the male
  • a sperm + ovum put together in a lab dish to produced fertilized ovum which becomes a blastocyst
  • good quality blastocyst(s) collected and transferred into the uterus
  • – OR they are frozen for later on

Renal and Endocrine Biology (25 decks)

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