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Physiology and Health: Chapter 8-10 Summary
The testes of the human male produce sperm from germline cells in seminiferous tubules
and make testosterone in interstitial cells.
The mobility and viability of sperm are maintained by fluids secreted by the prostate gland
and seminal vesicles.
The ovaries of the human female contain germline cells that produce ova (eggs) each
surrounded by a protective follicle. Hormones made by the ovary are oestrogen and
progesterone.
The pituitary gland releases follicle stimulating hormone (FSH) and interstitial-cellstimulating hormone (ICSH)/luteinsing hormone (LH).
In men, FSH stimulates sperm production and ICSH promotes testosterone production. The
concentration of testosterone is maintained at a steady level by negative feedback control.
In women, FSH stimulates the development of a follicle containing an ovum (egg) and the
secretion of oestrogen. LH triggers ovulation and brings about the development of the
corpus luteum which secretes progesterone.
Oestrogen stimulates the proliferation of the endometrium and progesterone promotes its
further development and vascularisation.
The menstrual cycle lasts for about 28 days and involves a follicular phase and a luteal
phase.
Fertility in men is continuous; fertility in women is cyclical, being restricted to the 1-2 days
following ovulation in each monthly cycle.
Infertility may be caused by failure to ovulate, blockage of oviducts or failure of
implantation in women, and low sperm count in men.
Methods of treatment of infertility include the use of drugs that stimulates ovulation,
artificial insemination, in--vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI).
Pre-implantation genetic diagnosis may be used during IVF to check an embryo for
chromosomal defects before implantation.
Some methods of contraception are based on biological knowledge of the menstrual cycle
and the avoidance of fertile periods. Other physical methods depend on barriers, intrauterine devices or sterilisation. Some chemical methods prevent follicles from being
stimulated and eggs from being released. Others cause thickening of cervical mucus.
During antenatal care, a dating scan is made by ultrasound imaging to determine the stage
the pregnancy has reached. An anomaly scan is used to detect physical problems with the
fetus.
Signs of medical conditions suffered by pregnant women can be detected using screening
tests for marker chemicals. These allow risk of genetic disorders in the fetus to be assessed
and may be followed up by diagnostic tests.
A karyotype is a display of a compliment of chromosomes arranged in pairs to show their
form, size and number.
During amniocentisis, a sample of amniotic fluid is taken to obtain cells for karyotyping to
check for chromosomal abnormalities. During chorionic villus sampling, cells for the same
purpose are obtained from the placenta. This procedure carries a higher risk of miscarraige
than amniocentesis.
A Rhesus-negative mother is given anti-rhesus antibodies after birth of a Rhesus-positive
baby to destroy and Rhesus antigens before her immune system has time to respond to
them.
Postnatal screening is carried out on newborn babies to check for metabolic disorders such
as PKU. Information about particular characteristics can be collected from the members of
a family and be used to construct a pedigree chart. Single gene disorders show different
patterns of inheritance, such as autosomal recessive.