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Phase 1 SUGER > Reproduction > Flashcards

Reproduction Flashcards

1
Q

Where are spermatazoa produced?

A

In the testis

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2
Q

What is ejaculate?

A

Mixture of spermatazoa and seminal plasma

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3
Q

What is the structure of the testes covered by?

A

Covered anteriorly by tunica vaginalis that descends into the scrotum with the testes
Tunica vaginalis is a saclike extension of the peritoneum

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4
Q

What is the tunica albuginea?

A

White fibrous capsule

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5
Q

What do the septa do?

A

Divide the organ into compartments containing seminiferous tubules where sperm are produced

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6
Q

What are leading cells?

A

Clusters of cells between the seminiferous tubules and source of testosterone

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7
Q

What are sertoli cells?

A

Promote sperm cell development
- blood testis barrier is formed by tight junctions between Sertoli cells separating sperm from immune system

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8
Q

Where do seminiferous tubules drain into?

A

Rete testis

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9
Q

What does the median septum divide?

A

Pendulous pouch holding the testes into two compartments

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10
Q

Why is testicular thermoregulation necessary?

A

Because Sperm are not produced at core body temperature

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11
Q

When does mitosis occur?

A

For Tissue repair and embryonic growth

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12
Q

How does heat exchange occur at the pampiniform plexus?

A

Arterial blood cool as it ascends testicular artery 37-35 degrees towards testis

Heat transfer from artery (testicular artery) vein (pampiniform plexus)

Venous blood carries away heat as it ascends

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13
Q

What are the products of mitosis and meiosis?

A

• Mitosis produces 2 genetically identical daughter
cells (occurs in tissue repair & embryonic growth)
• Meiosis produces gametes haploid cells required
for sexual reproduction

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14
Q

What occurs in meiosis?

A

2 cell divisions (after only one replication of DNA)
• meiosis I separates homologous chromosome pairs2
haploid cells
• meiosis II separates duplicated sister chromatids4 haploid
cells

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15
Q

Where does meiosis occur in males?

A

– meiosis occurs in seminiferous tubules of males

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16
Q

What is a feature of meiosis?

A

meiosis keeps chromosome number constant from
generation to generation after fertilization

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17
Q

What is produced in spermatogenesis?

A

Spermatogonia produce 2 kinds of daughter cells
– type A remain outside blood-testis
barrier & produce more
daughter cells until death
– type B differentiate into
primary spermatocytes

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18
Q

How do type B spermatogonium differentiate?

A

cells must pass through BTB (blood-testis barrier) to move inward toward lumen - new tight junctions form behind
these cells
• meiosis I -> 2 secondary spermatocytes
• meiosis II -> 4 spermatids

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19
Q

What is spermiogenesis?

A

Spermiogenesis is transformation of spermatids into
spermatozoa
– sprouts tail and discards cytoplasm to become lighter

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20
Q

How many sperm are made?

A

300 to 600 sperm are made
per gram of testis per second.
-50g x 50 min x 60 sec x 500
sperm =
75,000,000 spermatozoa

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21
Q

What is the blood-testis barrier formed by?

A

Blood-testis barrier is formed by tight junctions between and
basement membrane under sertoli cells.

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22
Q

What changes happen in spermiogenesis?

A

Changes that transform spermatids into spermatozoa
– discarding excess cytoplasm & growing tails

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23
Q

What is the duration of spermatogenesis?

A

64 in men and 16 day duration of cycle of the seminiferous epithelium

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24
Q

What occurs in the feedback control of the hypothalami-pituitary-testicular axis?

A
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25
Q

What is the structure of a spermatozoon?

A

Head is pear-shaped front end
– 4 to 5 microns long structure
containing the nucleus, acrosome
and basal body of the tail flagellum
• nucleus contains haploid set
of chromosomes
• acrosome contains enzymes
that penetrate the egg
• basal body

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26
Q

How is the tail divided into spermatazoons?

A

Tail is divided into 3 regions
– midpiece contains mitochondria
around axoneme of the flagellum
(produce ATP for flagellar
movement)
– principal piece is axoneme
surrounded by fibers
– endpiece is axoneme only and is
very narrow tip of flagellum

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27
Q

What are the spermatic ducts?

A

Efferent ductless
Epididymis
Ductus (vas) deferens
Ejaculatory duct

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28
Q

What are the efferent ductules like?

A

Efferent ductules
– 12 small ciliated ducts collecting sperm
from the rete testes and transporting it
to the epididymis

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29
Q

What is the S+F of the epididymis?

A

Epididymis (head, body & tail)
– 6 m long coiled duct adhering to the
posterior of testis
– site of sperm maturation & storage
(fertile for 40 to 60 days)

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30
Q

What is the S+F of the ductus (vas) deferens?

A

Ductus (vas) deferens
– muscular tube 45 cm long passing up
from scrotum through inguinal canal to
posterior surface of bladder
– widens into a terminal ampulla

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31
Q

What is the ejaculatory duct like?

A

Ejaculatory duct
– 2 cm duct formed from ductus deferens
& seminal vesicle & passing through
prostate to empty into urethra

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32
Q

What are the accessory glands?

A

Seminal vesicles
Prostate gland
• Bulbourethral glands

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33
Q

How much seminal fluid (semen) is expelled during orgasm?

A

Seminal vesicles
Prostate gland
• Bulbourethral glands

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34
Q

What are some components of sperm?

A

• Other components of semen
– fructose provide energy for sperm motility
– fibrinogen
– clotting enzymes convert fibrinogen to fibrin causing semen to
clot
– fibrinolysin liquefies semen within 30 minutes
– prostaglandins stimulate female peristaltic contractions
– spermine is a base stabilizing sperm pH at 7.2 to 7.6

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35
Q

What is the role of the sex chromosome?

A

Our cells contain 23 pairs of chromosomes
– 22 pairs of autosomes
– 1 pair of sex chromosomes (XY males: XX females)
• males produce 50% Y carrying sperm and 50% X carrying
• all eggs carry the X chromosome
• Sex of the child is
determined by the type
of sperm that fertilizes
the mother’s egg

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36
Q

What is gametogenesis?

A

-The process by which gametes are produced in the reproductive organs (gonads)
of an organism.
-Gametes are fundamental for sexual reproduction and genetic diversity.

37
Q

What occurs in folliculogenesis?

A
38
Q

What occurs in folliculogenesis?

A
39
Q

What occurs in oogenesis?

A
40
Q

Structure of female reproductive tract and oocyte?

A
41
Q

What occurs in the menstrual cycle?

A
42
Q

What is the hormonal control of the menstrual cycle?

A

Hypothalamus pituitary-gonad feedback loop

FSH/LH
Oestrogen and progesterone negative feedback

43
Q

How is sperm transported in the female reproductive tract?

A

-The process by which gametes are produced in the reproductive organs (gonads)
of an organism.
-Gametes are fundamental for sexual reproduction and genetic diversity.

44
Q

What is capacitation and when was it discovered?

A

•Capacitation was first discovered by Chang and
Austin independently (1950).
•The final maturational stage of spermatozoa that
takes place in the female genital tract, before
spermatozoa gain the ability to fertilize oocyte.
•It is one of the most investigated areas of
andrology and one of the least understood areas
of andrology.

45
Q

Necessary to know?

A

Artificial Insemination (AI)
•Embryo Transfer (ET)
•In Vitro Fertilization (IVF)
•Intra-Cytoplasmic Sperm Injection (ICSI)
•Somatic Nuclear Transfer (Cloning)
•Stem Cell Therapy (Regenerative Medicine)
•IPS Cells (Induced pluripotent Stem Cells)

46
Q

What occurs on day 1 of fertilisation?

A

Oocyte activation is key and is triggered by a sperm protein called Phospholipase C zeta (PLCz).
•This ‘activates’ the egg to release calcium from internal stores and this rise in calcium facilitates fertilisation.
•Oocyte activation is essential for the transformation of the decondensed sperm nucleus in to pronucleus.
•4-7 hours after gamete fusion the two sets of haploid chromosomes form the female and male pronucleus (23 chromosomes each)
•Pronuclei are equal size and contain nucleoli
•In IVF multinucleate oocytes can be identified - polyspermic

47
Q

What is syngamy?

A

Male and Female pronucleus migrate to centre (cytoskeletal system plays important role)
•Haploid chromosomes pair and replicate DNA in preparation for the first mitotic division
•The pronuclear membranes breakdown
•The mitotic metaphase spindle forms
•46 Chromosomes organise at the spindle equator

48
Q

What occurs on day 2 of embryo development?

A

Approx 24 hours after fertilisation the ooplasm divides in to two equal halves

•If one or more of the PN fail to decondense and move in to one of the blastomeres, diploid or triploid mosaics may occur

49
Q

What does the zona pellucida do?

A

maintains micro -environment for embryo until hatches at blastocyst stage)

50
Q

When are cleavages timed?

A

Cleavages are timed from sperm entry by an oocyte program that also regulates ‘house keeping’ activities in embryos.

•Successive cleavages result in an increase in cell number – essential to provide sufficient cells for differentiation.

51
Q

What type of genetic control occurs?

A

Prior to 4-8 cell stage the developmental control depends on maternally-derived stores of RNA laid down during oogenesis.

•Activation of the embryonic genome and start of embryonic transcription occurs in a 4-8 cell embryo.

•Developmental arrest can occur.

52
Q

What happens on day 3?

A

Early cleavage stage embryos are ‘totipotent’ – the nuclei of individual blastomeres are each capable of forming an entire foetus.

53
Q

What occurs on day 4?

A

Compaction
Cells flatten
•Maximise intracellular contacts
•Tight junctions form
•Polarisation of outer cells
•Morula – 16 cells

54
Q

What occurs on day 5?

A

Cavitation and differentiation

Tight junctions occur between outer cells – forms the trophectoderm
•Fluid filled cavity expands
•Sodium pumped in which pulls water in by osmosis
•Now >80 cells
•50-66% comprise trophectoderm, rest is ICM
•Pluripotent

In a trophodectoderm - single epithelial layer
Inner cell mass - pluripotent used for stem cell lines

55
Q

What occurs on day 5/6?

A

Cavity expands
•Diameter increases
•ZP thins

Expanded blastocyst

56
Q

What happens on day 6?

A

Hatching

Blastocyst expansion and enzymatic factors cause the embryo to hatch from the ZP.
•Essential for implantation
•TE – extraembyronic
•ICM - embryonic

57
Q

How does In-vivo fertilisation work?

A
58
Q

What are the energy requirements of…?

A

Early preimplantation embryo
–ATP turnover low
–ATP / ADP ratio is high
–Energy metabolism characterised by consumption of pyruvate
–Glucose uptake and utilisation is low

•Blastocyst stage
–Metabolic activity rises sharply
–ATP / ADP ratio falls, reflecting an increase demand for energy e.g for protein biosyntheses and ion pumping associated with blastocoel cavity.
–Glucose is the predominant exogenous energy substrate

59
Q

What is the activity at early cleavage vs blastocyst?

A

Genetic control - maternal vs embryonic
Metabolic activity - low vs high
Biosynthetic activity - low vs high
Nutrient requirements exogenous - simple (low glucose, non-essential amino acids) vs complex - high glucose, essential and non-essential amino acids, vitamins

60
Q

What is the provision of exogenous nutrients in in-vivo

A

Supplied by
–Cumulus cells
–Fallopian Tube secretions e.g. calcium,
sodium, chloride, glucose, proteins.
–Uterine secretions e.g. iron, fat soluble vitamins, glucose

•Concentrations of nutrients vary along the tract to provide the embryo requirements

•Growth factors and cytokines
–important in embryonic growth and differentiation
–Insulin-like growth factor - IGF–I and IGF–II increase cell numbers in blastocyst
–Leukaemia inhibitory factor (LIF) enhances embryo-endo interaction

61
Q

What occurs after implantation?

A

Cellular differentiation – 10 days
•After implantation embryogenesis continues with the next stage of gastrulation when the three germ layers of the embryo form in a process called histogenesis
•The 3 germ layers form: ectoderm, mesoderm and endoderm (three overlapping flat discs)
•It is from these three layers that all the structures and organs of the body will be derived

62
Q

How does the uterus change for implantation?

A

Endometrial cell changes to help absorption of uterine fluid – bring the blastocyst nearer to the endometrium and immobilises it.
•Changes in thickness of endometrium and its blood supply development
•Formation of the decidua

Implantation window = 4 days (6-10 days postovulation)

63
Q

What is the implantation process like?

A

Well defined starting point

•Gradual process over several weeks

•No universal agreement when process is completed

64
Q

What is the histology image at the trophoblastic plate stage?

A

= Carnegie stage 5A
Note the small size of the implantation site compared to the thickness of the endometrium.

1 day after initiation of implantation

65
Q

How is the implantation process regulated?

A

After embryo hatched the embryonic and maternal cells enter into a complex dialogue

•High degree of preparation and coordination required

•Controlled cascade of trophoblast proliferation, differentiation, migration
and invasion

66
Q

What is the cross talk between endometrium and the developing embryo mediated by?

A

The cross talk between endometrium and the developing embryo is mediated by substances including:
–Hormones (sex steroids)
–Cell adhesion molecules
–Proteases
–Cytokines, Growth Factors

–Also genetics
•5 genes up regulated during implantation window (Haouzi et al 2009)

67
Q

What are the 3 phases of embryo implantation?

A

Apposition

•Attachment

•Invasion

68
Q

What occurs in apposition?

A

Unstable adhesion of the
blastocyst to the uterine lining

•Synchronisation of embryo
and endometrium (decidua)

•Hatched blastocyst orientates via embryonic pole (always attaches at the area above the ICM)

•Receptive endometrium (implantation window day 19 – 22)

69
Q

What occurs in attachment?

A

Stable/stronger adhesion
•penetrate with protrusions of the trophoblast cells (microvilli)
•Massive communication between the blastocyst and endometrium conveyed by receptor-ligand interactions
•Apical surfaces of the endometrial epithelial cells express variety of adhesion molecules (integrin subunits)
•Trophoblastic cells also express integrins
•Attachment occurs through the mediation of bridging ligands that connect with integrins on their surfaces

70
Q

What occurs in invasion (penetration)?

A

Trophoblast protrusions continue to proliferate and penetrate the endometrium
•cells differentiate to become syncytiotrophoblast
•The trophoblast surrounding the ICM = cytotrophoblasts.
•Highly invasive - trophoblast quickly expands and erodes into endometrial stroma.
•Invasion is enzymatically mediated
•Syncytiotrophoblast erodes endometrial blood vessels
•Eventually syncytiotrophoblast comes into contact with maternal blood and form chorionic villi – in initiation of the formation of the placenta
•Blood filled lacunae form (spaces filled with maternal blood). Exchange nutrients and waste products.

71
Q

How does the trophoblast change after a few days?

A

After first few days of implantation, the trophoblast changes character to become less invasive

72
Q

What is the decidual reaction?

A

Promotes placental formation
•stromal cells adjacent to the blastocyst differentiate into metabolically active, secretory cells or Decidual Cells (under influence of progesterone)
•Secretions include growth factors/proteins to support growth of implanting blastocyst in the initial stages before the placenta is fully developed.
•Endometrial glands enlarge and local uterine wall becomes highly vascularised.
•The decidual reaction is not required for implantation e.g. ectopic implantation can occur anywhere in the abdominal cavity.

73
Q

What is the role of progesterone?

A

Modifies the distribution of oestrogen receptors
•Stimulates secretory activity
•Stimulates stromal oedema
•Increases volume of blood vessels
•Primes decidual cells
•Stabilises lysosomes
•Might be an immunosuppresent
•May stimulate growth factors and binding proteins
•May regulate the formation of reactive oxygen species (reducing oxidative stress)

74
Q

What is maternal recognition?

A

Embryo is antigenically different from the mother
•At the same time as the decidual reaction, leukocytes in the endometrial stroma secrete interleukin-2 which prevents maternal recognition of the embryo as a foreign body during the early stages of implantation
•uterine natural killer cells

75
Q

What is the role of human chorionic gonadotropin?

A

Essential to sustain early pregnancy
•ensures the corpus luteum continues to produce progesterone throughout the first trimester of pregnancy (prevents menstruation).
•Interacts with the endometrium via specific receptors
•Immunosuppressive – has highly negative charge, may repel the immune cells of the mother & protect the foetus.

76
Q

What are the hCG measurements in early pregnancy?

A

hCG to double every 1.3 days in the first 10-12 days of a normal singleton pregnancy

•A short doubling time signifies a healthy pregnancy

•Slow rate of increase might indicate
–Early abortion
–Ectopic pregnancy
–Delayed implantation
–Inadequate trophoblast

77
Q

What is the provision of exogenous nutrients in in vitro?

A

Embryos are highly sensitive to the environment – essential to optimise conditions to enable successful program

Day 0 - egg collection
Day 1
Day 5/6 - embryo transfer cryopreservation

78
Q

What is the provision of exogenous nutrients in in vitro?

A

Embryos are highly sensitive to the environment – essential to optimise conditions to enable successful program

Day 0 - egg collection
Day 1
Day 5/6 - embryo transfer cryopreservation

79
Q

What are in vitro cultures like from days 1-3+?

A

Use a sequential culture medium – different composition at different stages

Day 1-3
Water, salts &ions
Pyruvate, lactate, protein
and
No/low Glucose
Non essential amino acids

Day 3+
Water, salts &ions
Pyruvate, lactate, protein
and
Glucose
Essential and non essential amino acids
Vitamins

80
Q

What are in vitro cultures like from days 1-3+?

A

Use a sequential culture medium – different composition at different stages

Day 1-3
Water, salts &ions
Pyruvate, lactate, protein
and
No/low Glucose
Non essential amino acids

Day 3+
Water, salts &ions
Pyruvate, lactate, protein
and
Glucose
Essential and non essential amino acids
Vitamins

81
Q

How are in vitro culture systems 1 step?

A

One step (single culture)
–Culture day 1-6 in same media one media
–Let the embryo choose principal
–useful in uninterrupted systems like time lapse
–Why? Reduce stress, less disturbance, Increase embryo viability

82
Q

What factors affect embryo growth in vitro?

A

Maternal Factors
–Follicle environment
–Oocyte maturity (hCG trigger 36hours before egg collection)

•Embryonic factors
–Cleavage rate, size of blastomeres, degree of fragmentation
–Gross chromosome imbalance
–Variations in embryo metabolism
–Failure or abnormal formation of the blastocoel cavity

83
Q

What lab conditions affect in vitro growth?

A

Laboratory Conditions

–Exposure to light
–Exposure to high oxygen concentrations
–Changes in pH or osmolarity
–Culture medium
–Volatile organic compounds

84
Q

How are embryos transferred?

A

•Select morphologically best
embryo(s) to transfer on day 5.

•If any remaining embryos - cryopreserve.

•Need to be of good quality and correct stage of development to be frozen.

85
Q

Relevant? Evidence - blastocyst transfer?

A

Evidence – blastocyst transfer
•Enable better selection (embryonic genome activated)

•Promotes synchronization with the endometrium.

•Higher pregnancy and live birth rates for selected patient populations.
Blake DA, et al Cochrane Database Syst Rev., 2007; (4): CD002118
Papanikoloau EG, et alHum Reprod., 2005; 20 911): 3198 -203
Styer A, et al Fertil. Steril. Epub 2007 Jul 17

•Recent systematic review and meta-analysis demonstrated a much improved live birth rate compared to the early cleavage stage when equal numbers of embryos were replaced
Papanikolaou EG, et al Hum Reprod., 2008; 23 (1): 91 – 9

86
Q

What can cause a failed implantation?

A

Implantation failure is mainly related to either maternal factors or embryonic causes.

•Problem with the embryo - high proportion of embryos fail to implant
–Aneuploidy (40% IVF fertilised eggs abnormal)

•Interaction between embryo and uterus - insufficient trophoblast invasion
– miscarriage

•Insufficient invasion of maternal blood vessels
•Pre-eclampsia, poor foetal growth, hypertension

•Sperm problem – DNA fragmentation (abnormal genetic material). Increase miscarriage. Nutrition & lifestyle.

87
Q

When is it RIF?

A

Recurrent implantation failure when:

Failure to achieve a clinical pregnancy after transfer of at least 4 good quality embryos in at least 3 cycles

•Under the age of 40

88
Q

What are some underlying causes of RIF?

A

Poor ovarian function
•Increased sperm DNA fragmentation
•Uterine pathologies
–Polyps/fibroids
–Congenital anomalies
–Intrauterine adhesions
•Hydrosalpinges shown to significantly reduce implantation and preg rates - fluid toxic to embryos and affects endometrial receptivity.
•Immunological factor (NK cells)

89
Q

How do you manage RIF?

A

Lifestyle changes (smoking, BMI)
•Sperm DNA fragmentation test
•Improve embryo selection e.g. PGT-A
•Hysteroscopy – remove anomalies
•Fibroid / Polyps /Hydrosalpinges removal
•Immunotherapy (intravenous immunoglobulin) – maybe only subgroup of women benefit.

Phase 1 SUGER (9 decks)

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