Reproduction Flashcards
What produces gametes?
Meiosis
Where is sperm produced?
In the seminiferous tubules in the testes.
What do the prostate gland and seminal vesicles do to help sperm?
They secrete fluids that maintain the mobility and viability of the sperm.
What do the interstitial cells produce?
The hormone testosterone.
What is the female gamete and where is it found?
The gamete is the ova and they are found in the ovaries.
What is each ovum surrounded by that protects it and secrets hormones?
A follicle
Where are mature ova released into to await sperm?
The oviduct
When a mature ova is fertilised what is formed?
A zygote
What controls the onset of puberty, sperm production and the menstrual cycle?
Hormones.
What does the hypothalamus secret at puberty?
Releaser hormones
What two hormones does the pituitary gland release in females?
Follicle stimulating hormone and luteinising hormone.
What two hormones does the pituitary gland release in males?
Follicle stimulating hormone and interstitial cell stimulating hormone.
What does FSH promote in males?
Sperm production in the seminiferous tubules in the testes.
What does ICSH stimulate?
The interstitial cells in the testes to produce testosterone.
What does testosterone do?
Testosterone also stimulates sperm production and activates the prostate gland and seminal vesicles to produce their fluid secretions.
How is overproduction of testosterone prevented?
By a negative feedback mechanism. High testosterone inhibits the secretion of FSH and ICSH from the pituitary gland, resulting in a decrease in the production of testosterone by the interstitial cells.
How long does the menstrual cycle take approximately?
28 days
Which day of menstrual cycle is regarded as menstruation?
Day 1
What does FSH stimulate in females?
The development and maturation of a follicle surrounding the ovum and the production oestrogen by the follicle.
What oestrogen stimulate?
The repair and proliferation of the endometrium, preparing it for implanting as well as affecting the consistency of the cervical mucus making it more easily penetrated by the sperm.
What does a peak level of oestrogen stimulate?
A surge in the secretion of LH by the pituitary gland.
What does the surge in LH trigger?
Ovulation
What is ovulation?
Ovulation is the release of an egg (ovum) from a follicle in the ovary and usually occurs around the midpoint of the menstrual cycle.
What does LH stimulate?
The development of the corpus luteum from the follicle and stimulates the corpus luteum to secrete progesterone.
What does progesterone promote?
Further development and vascularisation of the endometrium preparing it for implantation if fertilised.
What do high levels of oestrogen and progesterone inhibit?
The secretion of FSH and LH by the pituitary gland, which prevents further follicles from developing.
What does the lack of LH at the end of the menstrual cycle lead to?
The degeneration of the corpus luteum with a subsequent drop in progesterone levels, leading to menstruation.
If fertilisation occurs what happens to the corpus luteum?
It does not degenerate and progesterone levels remain high.
What type of fertility do men show and why?
Continuously fertility as they continuously produce sperm due to the constant levels of pituitary hormones.
What type of fertility do women show and why?
Cyclical fertility as they are only fertile for a few days each menstrual cycle.
When is a women most fertile?
A few days before until one or two days after ovulation.
How can time of ovulation be estimated?
A slight rise in body temperature (about 0.5*c) on the day of ovulation and the thinning of cervical mucus (becomes thin and watery).
What may cause infertility in women?
Failure to ovulate, which is usually the result of a hormone imbalance.
How is ovulation stimulated?
By drugs that prevent the negative feedback effect of oestrogen on FSH secretion. Or by drugs which mimic then action of oestrogen and progesterone.
What can ovulation drugs cause?
Super ovulation which can result in multiple births or be used to collect ova for IVF programmes.
What is artificial insemination?
AI is a treatment of infertility in which seman is is inserted into the female reproductive tract. (Several sperm samples are collected and combined).
When is AI useful?
When a male has a low sperm count.
What happens in AI if a male partner is infertile/sterile?
A donor may be used.
What does in vitro fertilisation involve?
IVF involves the surgical removal of eggs from the ovaries after hormone stimulation, mixing with sperm to achieve fertilisation, incubation of zygotes and uterine implantation.
What is IVF used in conjunction with?
Pre-implantation genetic diagnosis (PGD).
What does PGD identify?
Single gene disorders and chromosome abnormalities.
In IVF what are sperm and eggs mixed in?
A culture dish.
How long is the fertilised egg incubated for in IVF?
Until it has formed at least 8 cells.
What infertility treatment is used when mature sperm are defective or low in number?
Intracytoplasmic sperm injection (ICSI).
What does ICSI involve?
The head of a sperm being drawn into a needle and injected directly into the egg to achieve fertilisation.
List some physical contraceptive methods.
Barrier methods (condom, diaphragm), intra-uterine devices and sterilisation procedures.
What is the oral contraceptive pill?
A chemical method of contraception, containing a combination of synthetic oestrogen and progesterone that mimic negative feedback, preventing the release of FSH and LH from the pituitary gland.
What does the progesterone-only (mini) pill do?
Causes the thickening of the cervical mucus preventing sperm entry and fertilisation.
What does the morning-after pill prevent?
Ovulation or implantation.
What does antenatal screening identify?
The risk of a disorder
What are the two types of ultrasound scans?
- Dating scan
- Anomally scan
What is a dating scan and when does it take place?
A dating scan is an ultrasound scan that determines pregnancy stage and the due date. It is called out between 8 and 14 weeks into the pregnancy.
What is an anomally scan and when does it take place?
An anomally scan is an ultrasound scan that detects serous physical abnormalities in the foetus. It is carried out between 18 and 20 weeks into the pregnancy.
What do routine blood and urine tests monitor?
The concentrations of marker chemicals.
What happens when a marker chemical is measured at the wrong time during a blood or urine test?
It can lead to a false negative result.
If an artificial marker chemical concentration is measured during a blood or urine test what happens next?
Diagnostic testing to determine if the foetus actually has a medical condition.
What are the two types of diagnostic tests?
- Amniocentesis
- Chorionic villus sampling (CVS)
What is amniocentesis and when is it carried out?
Amniocentesis is a diagnostic test that uses a small amount of amniotic fluid from the amniotic sac surrounding the foetus to check for genetic disorders. It can be carried out at 14-16 weeks.
What is CVS and when is it carried out?
CVS is a diagnostic test that tests a sample of cells from the mothers placenta for genetic disorders. It can be carried out at 8 weeks but has a higher risk of miscarriage.
What is a karyotype?
A karyotype shows an individuals chromosomes arranged as homologous pairs.
What are pedigree charts used for?
To analyse patterns of inheritance in genetic screening and counselling.
What are alleles?
Forms of the same gene.
What does homozygous mean?
Individuals have two copies of the same gene.
What does heterozygous mean?
Individuals have copies of two different alleles.
What is an autosomal recessive disorder?
A disorder which only affects an individual when they have two alleles with the disorder. E.g. cystic fibrosis
What is an autosomal dominant disorder?
A disorder that affects anyone with at least one copy of the disorder. E.g. Huntington’s Disease.
What is an autosomal incomplete dominance disorder?
A disorder where someone with two alleles of the disorder are seriously affected whereas someone with just one allele of the disorder are only mildly affected. E.g. sickle cell anaemia
What is a sex-linked recessive disorder?
A disorder that involves the sex chromosomes and men are more affected than women (XhY and XHXh). E.g. haemophilia
What are postnatal screening tests?
Tests that are carried out after the birth of a child to detect conditions or abnormalities.
What can postnatal diagnostic testing be used to detect?
Metabolic disorders such as phenylketonuria. (PKU)
What is PKU?
PKU is an inborn error of metabolism caused by an autosomal recessive genetic disorder. In PKU a substitution mutation means that the enzyme which converts phenylalanine to tyrosine is non-functional.
How is PKU most commonly tested for?
Using a ‘heel prick test’ which is where a sample of blood is drawn from a pin prick in the heel of the newborn.
What happens is PKU is not detected soon after birth?
The babies mental development could be affected.
What happens to individuals with PKU?
They are placed on a restricted diet that lacks the amino acid phenylalanine.
