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MEDS1001 > making egg and sperm & development and birth > Flashcards

making egg and sperm & development and birth Flashcards

1
Q

Mitosis

A
  • 4 stages (+ interphase)
  • somatic cells
  • produces 2 diploid daughters
  • gen. var. does not change
  • no. of chromosomes stay the same
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2
Q

Meiosis

A
  • 8 stages (+ interphase)
  • germ/sex cells
  • produces 4 haploid daughter cells
  • gen. var. increases
  • no. of chromosomes is halved
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3
Q

Female reproductive system

A
  • Ovaries open into peritoneal cavity
  • Fimbriae direct ovum in uterine tube/fallopian tube/oviduct
  • Successful fertilisation normally occurs in the first third of the uterine tube
  • Vagina
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4
Q

Male reproductive system

A

Testis and scrotum
Epididymis
Vas deferens or ductus deferens
Urethra

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5
Q

Seminal vesicles

A
  1. Prostaglandin, stimulate motility of sperm
  2. Fructose, nutrient source for the sperm
  3. Clotting agents (different from blood), coagulates semen after ejaculation
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6
Q

Prostate gland

A
  • Citric acid, used by sperm in ATP production (energy)
  • Proteolytic enzymes, eventually breakdown clotting agents
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7
Q

Bulbourethral (Cowper’s) glands

A
  • Mucous (released pre-ejaculation), lubricate urethra and end of penis to prevent damage to sperm
  • Alkaline fluid, neutralise acidity of urethra
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8
Q

Vagina

A

channel connecting to the cervix

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9
Q

Spermatogenesis

A

the process of sperm cell formation that occurs in the seminiferous tubules of the testes in males

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10
Q

seminiferous tubules

A

coiled tubes, the walls of which contain cells that produce sperm

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11
Q

Sperm. Proliferative phase:

A
  • Undifferentiated germ cells (spermatogonia) undergo mitotic divisions to increase their numbers.
  • As a result, some of the spermatogonia become primary spermatocytes, which enter the meiotic phase.
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12
Q

Sperm. Meiotic phase:

A
  • primary spermatocytes undergo two successive meiotic divisions to produce four haploid cells called spermatids.
  • Each spermatid contains half the genetic material of the original primary spermatocyte.
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13
Q

Spermatid differentiation

A

the process by which immature, haploid cells called spermatids transform into mature, highly specialised sperm cells during the final phase of spermatogenesis

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14
Q

1.Formation of the acrosome:

A
  • Acrosome: specialised organelle that covers the head of the mature sperm and contains enzymes needed for fertilisation.
  • During spermatid differentiation, a vesicle derived from the Golgi apparatus fuses with the nuclear envelope to form the acrosome.
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15
Q

2.Elongation and condensation of the nucleus:

A

The spermatid nucleus becomes highly condensed and elongated to form the head of the mature sperm.

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16
Q

3.Formation of the flagellum:

A
  • Flagellum: long, whip-like structure that propels the sperm.
  • During spermatid differentiation, a centriole at the base of the cell elongates and forms the axoneme, the core of the flagellum.
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17
Q

4.Shedding of excess cytoplasm:

A
  • Immature spermatids contain a large amount of excess cytoplasm, which is removed during spermatid differentiation to create a streamlined shape for easier movement.
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18
Q

Oogenesis

A
  • process of egg cell formation in females.
  • It occurs in the ovaries and begins during foetal development, but most of the process occurs after puberty and continues until menopause.
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19
Q

Ovaries

A
  • Suspended by ligaments
  • Ovarian follicle containing - Oocyte, blood vessels, lymphatic vessels and nerves
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20
Q

Oog. Proliferative Phase:

A
  • Begins during foetal development when the primordial germ cells divide and differentiate into oogonia, which are the precursor cells of eggs.
  • Oogonia undergo mitotic divisions to increase their numbers and form primary oocytes.
21
Q

Oog. Meiotic Phase:

A
  • Paused at prophase I of meiosis until puberty.
  • At puberty, a small number of primary oocytes are stimulated to resume meiosis I.
  • One of these primary oocytes is released from the ovary during each menstrual cycle and begins meiosis II, which is only completed if the egg is fertilised.
  • Meiosis results in the production of one mature egg and three nonfunctional polar bodies.
22
Q

Oog. Differentiation Phase:

A
  • Occurs after fertilisation or after the primary oocyte has completed meiosis II to produce a mature egg.
  • The egg undergoes further differentiation, during which it acquires the necessary organelles and molecular machinery to support early embryonic development.
23
Q

The hormones in males (before puberty)

A

Testosterone and Inhibin inhibit:
* GnRH (secreted by immature hypothalamus) and,
* Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) secretion by the anterior pituitary gland

24
Q

The hormones in males (puberty)

A
  • Begins 12-14yrs old
  • Hypothalamus maturation reduces sensitivity to testosterone and inhibin
  • GnRH secretion that increases Luteinizing hormone (LH) and follicle stimulating hormone (FSH)
  • Enlargement of reproductive organs and development of secondary male characteristics
25
Q

The hormones in females (before puberty)

A
  • Oestrogen and progesterone (ovaries) negative-feedback
  • Low GnRH (immature hypothalamus), low LH and FSH (anterior pituitary)
26
Q

The hormones in females (puberty)

A
  • Begins 11-13yrs old
  • Maturation of hypothalamus: high GnRH, high LH and FSH
  • decrease negative-feedback of oestrogen and progesterone
  • oestrogen production increased by developing follicle
  • Enlargement of reproductive organs and development of secondary female characteristics
27
Q

Menses

A

(4-5 days)
removal of superficial layer of endometrium
Day 1 of cycle – first full day bleeding

28
Q

Proliferative Stage (menstrual)

A
  • Sustained increase in oestrogen stimulates GnRH secretion by hypothalamus
  • GnRH triggers LH and FSH secretion from anterior pituitary
  • FSH stimulates oestrogen prod. by develop. follicles, results in positive feedback
  • Large increase in LH triggers ovulation (approx.day 14) which is the start of the secretory stage
29
Q

Secretory Stage, Corpus luteum

A
  • Secretes progesterone and small amounts of oestrogen
  • Progesterone thickens endometrium and causes fluid secretion (nutrients for embryo)
  • Progesterone and oestrogen inhibit hypothalamus and anterior pituitary and hence LH and FSH secretion decline after ovulation
30
Q

If fertilisation…

A

(7-8 days after ovulation)
* Endometrium becomes fully developed
* Human chorionic gonadotropin (HCG) production by the trophoblasts during implantation of the embryo which maintains corpus luteum

31
Q

If no fertilisation…

A

(menses)
* Endometrium sloughed
* Corpus luteum degenerates, reducing progesterone
* Increase FSH

32
Q

Fertilisation Day 0

A
  • Preventing polyspermy
    Two mechanisms prevent more than one sperm:
  1. Fast block (Na+) diffuses into oocyte from extracellular space, and
  2. Slow block (Ca2+) release by ER, initiate cell division (complete meiosis) and trigger cortical reaction
33
Q

Zygote

A

Formed when pronuclei of sperm and egg fuse

34
Q

Cleavage Day 1 to 6

A

repeated mitotic division as the embryo migrates down the oviduct to the uterus

35
Q

Implantation Day 7 to 10

A

The developing embryo attaches to the lining of the uterus and begins to receive nutrients and oxygen from the mother’s blood supply.

36
Q

Gastrulation Day 12

A
  • The inner cell mass of the blastocyst undergoes complex cellular and molecular changes that result in the formation of the three germ layers: the endoderm, mesoderm, and ectoderm.
  • These germ layers will give rise to all the different tissues and organs of the body.
37
Q

Neurulation Day 18

A
  • Ectoderm differentiates into the neural plate, which will eventually give rise to the central nervous system (CNS)
  • Folding of neural tube determines position of:
    Grey matter (unmyelinated neurons and cell bodies) and
    White matter (myelinated neurons) in CNS
38
Q

Organogenesis begins around 3 to 8 weeks and continues until birth

A

Depends on the development of different organs
Brain: week 3
Heart: week 3, the 4 chambers formed in week 7
Kidneys: week 9
* From fertilisation to week 7 a developing human is referred to as an embryo.
* From week 8 to birth, the developing human is called a foetus

39
Q

Gestation 280 Days

A

… 40 weeks or 9 months (3 trimesters)

40
Q

Parturition

A
  • Dilation of the cervix (contractions of the uterine muscles)
  • Descent and expulsion of the baby through the birth canal
  • Delivery of the placenta.
41
Q

Developmental origins of health and disease

A

the exposure to environmental factors during gestation (prenatal) and the first year after birth (perinatal) will determine the development of human diseases in adulthood

42
Q

Which of the following best describes the feedback mechanism between the gonads and the hypothalamus/pituitary gland in females?

A

It is sometimes positive feedback and sometimes negative feedback

43
Q

Gonads

A

glands that produce hormones that are involved in reproduction and other functions of the body

44
Q

chimera

A

a single organism composed of cells with more than one distinct genotype

45
Q

embyonic development

A
  1. Production of a polar body through meiosis II
  2. Mitosis
  3. Leaving the zona pellucida
  4. Implantation
46
Q

The stages of embryonic development

A

Zygote > Morula > Blastocyst > Gastrula

47
Q

The largest number of oocytes are produced in the ovaries during which period of life:

A

birth

48
Q

Which is the first developmental stage when all three cell layers are present?

A

gastrula

MEDS1001 (21 decks)

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