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BIOM 3200 > Reproductive System > Flashcards

Reproductive System Flashcards

1
Q

Which type of cells are involved in spermatogenesis? Where are they located?

A
  • Sertoli cells

- Basement membrane of seminiferous tubule (form continuous layer connected by tight junctions)

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2
Q

Describe the blood-testis barrier?

A
  • Molecules from blood must be allowed through Sertoli cells to reach developing spermatozoa
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3
Q

Where are spermatogonia located?

A
  • Located on the basement membrane of seminiferous tubules
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4
Q

Where do spermatogonia travel towards?

A
  • Move towards lumen as they develop into spermatozoa
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5
Q

Describe the 5 steps of spermatogenesis?

A

1 - Spermatogonia are DIPLOID cells that give rise to 2 daughter cells via MITOSIS
2 - One remains at the basement membrane as a stem cell
3 - Another (primary spermatocyte) develops into spermatozoa as it moves toward the tubule lumen
4 - 1st meiosis: DNA duplicates, then homologous chromosomes separate into 2 HAPLOID daughter cells
5 - 2nd meiosis: Duplicate chromatids separate into 4 HAPLOID daughter cells

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6
Q

How many spermatogonia are present in embryonic testes?

A
  • 1000-2000

- So mitosis is crucial

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7
Q

How many sperm does the median ejaculation contain?

A
  • About 255 million sperm in 1.5-5 mL fluid
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8
Q

What is considered oligospermia?

A
  • Less than 20 million/mL

- Leads to decreased fertility

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9
Q

How are the seminiferous tubules protected from immune attack?

A
  • By Sertoli cells
  • Blood-testis barrier
  • Production of FAS ligand which binds to FAS receptor on T cell, triggering T cell apoptosis and preventing immune system attack on developing sperm
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10
Q

What is the life span of sperm once ejaculation has occurred?

A
  • About 80 hrs or 3 days
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11
Q

What helps in maintaining metabolic requirements of sperm?

A
  • Cervical mucus
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12
Q

What happens to sperm when they migrate in the female reproductive tract?

A
  • Sperm are rapidly separated from seminal fluid and resuspended in female reproductive fluid
  • Undergo ‘capacitation’ (or maturation) during their passage through female reproductive tract
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13
Q

What is the acrosome of spermatozoa?

A
  • Protein/enzyme layer at tip of sperm
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14
Q

Where is the nucleus located in spermatozoa?

A
  • Head
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15
Q

Where is the mitochondria of spermatozoa located?

A
  • Mid piece
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16
Q

What is capacitation?

A
  • The process of physiological changes occurring in mammalian sperm during passage through the female reproductive tract that enables them to penetrate the egg membrane
  • Alteration of glycoprotein surface of sperm under the influence of secretion of the tissues of the female reproductive tract
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17
Q

Which sperm does not require capacitation?

A
  • Non-mammalian sperm
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18
Q

What does the surface of epididymal sperm contain?

A
  • Glycoproteins
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19
Q

What happens to the glycoproteins when sperm is ejaculated?

A
  • Surface glycoproteins are coated with seminal plasma proteins
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20
Q

What does capacitated sperm look like?

A
  • Surface glycoproteins are removed

- Exposes molecules that can bind zona pellucida of the oocyte

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21
Q

How many sperm reach the site of fertilization?

A
  • Only few
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22
Q

Where are most sperm eliminated? How?

A
  • Cervix
  • Uterotubal junction
  • Female immune system attack
  • Phagocytosis
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23
Q

What happens to damaged/immotile sperm?

A
  • Carried back to cervix by ciliated cells
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24
Q

What is fertilization?

A
  • Series of processes beginning with sperm penetrating corona radiata/zona pellucida surrounding the oocyte, entering the oocyte, and ending with intermingling of maternal/paternal chromosomes
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25
Q

Where does fertilization usually occur?

A
  • Fallopian tube
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26
Q

About how many mature sperm reach the egg in the fallopian tube?

A
  • About 100
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27
Q

How does fertilization occur?

A
  • First sperm to successfully fuse with egg blocks polyspermy
  • Electrical polyspermy blocks function in some animals (frogs, clams, marine worms)
  • Mammals lack electrical block; polyspermy prevented by secreted chemical barrier
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28
Q

What is necessary to release egg?

A
  • LH surge to promote follicle rupture
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29
Q

How do the LH/FSH levels change 2 days before ovulation?

A
  • LH increases 6-10 fold

- FSH increases 2-3 fold

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30
Q

How does LH affect ovulation?

A
  • Converts granulosa cells to estrogen/progesterone-secreting cells
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31
Q

When can fertilization occur?

A
  • As early as 3 days prior to ovulation

- Up to 1 day after ovulation

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32
Q

When does the secondary oocyte disintegrate?

A

12-24 hours after ovulation if it isn’t fertilized

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33
Q

Describe the process of egg transport.

A
  • Secondary oocyte enters fallopian tube
  • Fertilization
  • Becomes zygote
  • Mitosis creates multi-celled zygote
  • Morula (12-16 cells) formed when it enters the uterus
  • Becomes a blastocyst after 5-6 days
  • Implanted blastocyst contains inner (fetus) and outer (placenta) cell mass
34
Q

How are dizygotic twins formed?

A
  • Fraternal twins

- Develop from 2 separate oocytes fertilized at the same time

35
Q

How are monozygotic twins formed?

A
  • Identical twins
  • Two individuals developed from one fertilized oocyte
  • Identical genomes
36
Q

What are conjoined twins?

A
  • Monozygotic twins whose bodies are joined to a varying extent
37
Q

How does implantation/nidation of the blastocyst occur?

A
  • Trophoblasts produce enzymes that allow blastocyst to implant in endometrium of posterior wall of uterine cavity
  • Trophoblasts secrete hCG to maintain corpus luteum (to make progesterone until placenta takes over)
38
Q

Why do about 75% of lost pregnancies occur?

A
  • Failed implantation
39
Q

What is an ectopic pregnancy? How often does it happen?

A
  • Implantation in different site than posterior wall of uterine cavity
  • 0.25-1% of pregnancies
40
Q

What is detected in pregnancy tests? Where is it made?

A
  • hCG

- Trophoblasts in blastocyst

41
Q

What hormones are secreted in pregnancy? By what?

A
  • hCG (secreted by blastocyst)
  • > High in early pregnancy, then drops after 2 months
  • Estrogen/progesterone (secreted by corpus luteum then placenta)
  • > gradually increases until delivery
42
Q

Describe the mechanism of a pregnancy test?

A
  • Immunoassay: tagged antibody specific to hCG (detected in blood/urine)
    1 - 1st window
    -> if hCG present = dye accumulates = visible line
    2 - 2nd window
    -> control to ensure proper function
43
Q

What is the luteal-placental shift?

A
  • Placenta takes over secreting estrogen/progesterone to maintain endometrial lining instead of corpus luteum
44
Q

Why is the placenta required for pregnancy?

A
  • ‘feeds’ fetus through umbilical cord
  • Placental a2-adrenoceptors control vascular development at the interface b/n mother and embryo
  • Substantial percentage of pregnancies are lost due to inadequately developed placenta
  • Proper development of placental vascular system is essential to nutrient, gas, and waste exchange b/n mother and developing fetus
45
Q

Which systems does the placenta perform the function of for the fetus?

A
  • Digestive
  • Respiratory
  • Renal
46
Q

What is the most preventable cause of illness and death among mothers and infants?

A
  • Smoking during pregnancy
47
Q

What necessary hormones does the placenta provide?

A
  • Unique endocrine gland (transient, without extrinsic control)
  • hCG: maintains corpus luteum
  • Estrogen: Acts on uterine myometrium (growth, oxytocin receptors), breast ducts
  • Progesterone: Suppresses uterine contractions, cervical plug, milk glands
  • PTHrP: Mobilizes mother’s bone calcium
  • CRH: Fetal lung maturation
48
Q

What type of loop controls parturition?

A
  • Positive feedback
49
Q

Describe the endocrine control of parturition?

A

1 - Fetal adrenal gland secretes DHEAS and cortisol upon stimulation by CRH and ACTH
2 - Cortisol stimulates the placenta to secrete CRH, producing a positive feedback loop
3 - DHEAS is converted in placenta to Estriol, which together with placental prostaglandins and maternal oxytocin stimulate the maternal myometrium to undergo changes leading to labour

50
Q

What are the only 2 anterior pituitary hormones whose secretion is regulated by both hypothalamic releasing and inhibiting hormones?

A
  • Prolactin and GH
51
Q

Describe the hypothalamus -anterior pituitary gland-mammary gland axis?

A

Hypothalamus -PIH/PRH-> Anterior pituitary -prolactin-> Mammary glands -> Milk production and growth/development of glands and ducts

52
Q

How many lobes is the mammary gland composed of? What is it divided by?

A
  • 7-10 lobes

- Divided by adipose tissue

53
Q

How are the lobes of the mammary gland divided?

A
  • Each lobe is subdivided into lobules

- Lobules contain alveoli

54
Q

Which part of the mammary glands secretes milk?

A
  • Alveoli secrete milk into secondary tubules, which form into mammary ducts, then lactiferous duct, then drain at nipple
55
Q

What is the function of myoepithelial cells in lactation?

A
  • Myoepithelial cells contract to propel milk through the duct system
56
Q

Where does milk accumulate during nursing?

A
  • Lumen of the lactiferous duct
57
Q

Describe prolactin levels during pregnancy?

A
  • High estrogen inhibits PIH, allowing prolactin to stimulate milk production
  • However, high estrogen and progesterone levels inhibit milk secretion until after parturition when estrogen and progesterone levels decrease
58
Q

How are high prolactin levels maintained?

A
  • Act of nursing via neuroendocrine reflex

- Stimulus may be suckling or visual or auditory cue, or thought of child

59
Q

Describe the milk-ejection reflex?

A
  • Oxytocin stimulates myoepithelial cells surrounding lactiferous ducts to contract
60
Q

What does human breast milk contain that can’t be replicated in formula?

A
  • Immune cells
  • Stem cells
  • Immunoglobulins
  • Cytokines
  • Growth factors
  • Other hormones
61
Q

What is the trust/love potion?

A
  • Oxytocin
62
Q

What determine biological sex?

A
  • SRY (Sex determining Region of the Y) induces the embryonic gonads to become testes
  • Biological females lack a Y chromosome, and the absence of this gene causes the development of ovaries
63
Q

Describe sex differentiation for females?

A

1 - Absence of SRY protein - gonadal tissue develops into ovaries
2 - Hence no Sertoli cells or testosterone, so no Mullerian inhibition factor (MIF) is made from Sertoli cells, so Wolffian duct degerates
3 - Absence of MIF allows the Mullerian duct to become the fallopian tube, uterus and vagina.

64
Q

What is the sex of the fetus considered to be at 6 weeks?

A
  • Bipotential primordium

- Gonadal tissue is indistinguishable between female and male

65
Q

Describe sex differentiation in males?

A

1 - Presence of SRY protein - gonadal tissue develops into testes
2 - Presence of Sertoli cells and testosterone, so MIF is secreted from Sertoli cells, which maintains the Wolffian duct and causes the Mullerian duct to degerate
3 - Testosterone allows Wolffian duct to become seminal vesicle, vas deferens and epididymis

66
Q

What is TDF?

A

Testis-determining factor

67
Q

What are true hermaphrodites?

A
  • An intersex condition where individuals have both ovary and testis tissue
  • Abnormality in sex chromosomes
  • Various degrees of mosaicism
68
Q

What are pseudohermaphrodites?

A
  • Congenital condition where a person has external genitalia of one sex, and internal sex organs of the other sex
  • Born with external genitalia that appears female, at puberty, male genitalia and characteristics develop
  • Endocrine disorder
  • Genetically males with a defective gene for 5alpha-reductase (converts testosterone to 5-DHT)
69
Q

Describe the mechanism of pseudohermaphroditism?

A
  • Normal testosterone production
  • Defective 5alpha-reductase
  • Inadequate 5-DHT
  • Inappropriate exposure to androgens early on
  • At puberty, testes secrete testosterone again
70
Q

In which sex does puberty occur more rapidly and earlier?

A
  • Females
71
Q

Describe puberty

A
  • Activation of HPG axis resulting in gonad maturation
72
Q

What is adolescence?

A
  • Maturation of adult social and cognitive behaviours
73
Q

What controls metamorphosis of the child into adult?

A
  • Coupling of puberty and adolescence between endocrine system and nervous system
74
Q

Describe the GnRH pathway?

A

Hypothalamus -GnRH-> Anterior pituitary -FSH/LH-> Endocrine cells of gonads -Androgen/estrogen/progesterone-> Germ cells of gonads

75
Q

How does GnRH secretion occur?

A
  • In pulses, NOT steadily
76
Q

What happens to children with a deficiency in GnRH?

A
  • Do not mature sexually
77
Q

How do they treat a deficiency in GnRH? What is the result?

A
  • Treat with GnRH pulses similar to those that occur naturally
  • Children go through puberty
78
Q

What affects puberty onset?

A
  • Genetic variations
  • Environmental factors
  • Synthetic chemicals
  • Nutrition
  • Chronic illness
  • Psychological factors
79
Q

What has changed in puberty onset in developed countries?

A
  • Girls are experiencing puberty earlier
80
Q

What are some potential causes of early puberty?

A
  • Obesity
  • Premature birth
  • Reduced altitude
  • Exposure to light
  • Endocrine-disrupting chemicals (flame retardants on fabric, bisphenol A in plastic, cigarette smoke)
  • Family conflict/abuse

BIOM 3200 (4 decks)

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