16.4 - 16.6 Reproduction in humans Flashcards
prostate gland
produces fluid called semen that provide sperm cells with nutrients
sperm duct
sperm passes through the sperm duct to be mixed with fluids produced by the glands before being passed into the urethra for ejaculation
urethra (male)
tube running down centre of penis that can carry out urine or semen, a ring of muscle in the urethra prevents the urine and semen from mixing
testis
produces sperm and testosterone
scrotum
sac supporting the testes outside the body to ensure sperm are kept at temps slightly lower than body temp
penis
allows semen to pass into the vagina during sexual intercourse
oviduct
Connects the ovary to the uterus.
Lined with ciliated cells to push the released ovum down it.
Site of fertilisation.
Ovary
contains ova which will mature and develop when hormones are released
uterus
muscular bag with a soft lining where the fertilised egg will be implanted to develop into fetus
cervix
ring of muscle at the lower end of the uterus to keep the developing fetus in place during pregnancy
vagina
where the penis is inserted during sexual intercourse and where sperm are deposited
sperm cell adaptations
flagella - allows it to swim through the female reproductive system
acrosome in head - contains enzymes so that sperm can penetrate egg
many mitochondria - to produce energy
egg cell adaptations
jelly-like coating that changes after fertilisation
- forms an impenetrable barrier after fertilisation to prevent other sperm nuclei from entering
cytoplasm which contains a store of energy - provides energy for the dividing zygote after fertilisation
Sperm cell in terms of: size, motility, and numbers
Size: very small (45 nano meters)
motilitiy: capable of moving on place to another (locomotion)
numbers: produced in huge numbers
Egg cell in terms of: size, motility, and numbers
Size: Large (0.15mm)
Motility: not capable of locomotion
Numbers: one released each month
embryo
the ball of cells that result from the division (by mitosis) of the zygote
mitosis
a type of cell division in which one diploid cell divides to produce two new diploid cells (the daughters) that are genetically identical to itself
After fertilisation what happens to the zygote?
- Zygote travels down the oviduct and divides by mitosis to form an embryo
- Implantation occurs
- The placenta, umbilical cord, and amniotic fluid form
- The embryo diffrentiates to produce a variety of tissues and organs
- The embryo is referred to as fetus
gestation
the period from fertilisation to birth - about 38 weeks.
what happens in early development for the zygote?
The zygote forms an embryo which is a ball of cells that implants itself into the lining of the uterus
What is the placenta?
A tempory organ that develops in the uterus during pregnancy.
function of placenta
- Allows substances to diffuse from the mum’s blood to the fetus (e.g. oxygen and glucose). Substances can also diffuse from the fetus to the mum’s blood (e.g. carbon dioxide and urea)
- Provides a barrier to toxins and pathogens (but not all toxin molecules or pathogenic organisms are stopped from passing)
- Protection: from the mum’s immune system and against flunctuations in mum’s blood pressure
- Secretion of hormones (progesterone) to maintain the lining of the uterus
Adapative features of the placenta for diffusion
Very large surface area between it and the uterus wall.
Villi increase.
Rich supply of maternal blood vessels.
Function of umbilical cord
The umbilical artery - carries urea and carbon dioxide from the fetus to the mothers blood
The umbilical vein - carries oxygen and nutrients from the mother’s blood to the fetus
Labour stages
- When birth starts, the uterus begins to contract rhythmically
- the regular contractions become stronger and more frequent
- the opening of the cervix gradually widens (dilates) enough to let the babies head pass through andthe contractions of the muscles in the uterus are assisted by muscular contraction of the abdomen
- the amniotic sac breaks at some stage in labour and the fluid escapes through the vagina
- the muscular contractions of the uterus wall and abdomen push the abby head first through the widened cervix and vagina
- the umbilcal cord is tied and cut
- the placenta breaks away from the uterus and is pushed out seperately
Antenatal (before birth) care of pregnant women
- should take more folic acid to prevent developmental issues and iron to prevent anemia
- should not do heavy lifting
- stay away from drugs
- vaccination against rubella
- do not smoke - reduces the amount of oxygen in bloodstream = higher likelihood of miscarriage and premature birth
- do not drink - damages nervous system, espiecally the brain = underweight, sick children
What does testosterone do during puberty
Hoarse voice, increased growth rate, broad muscles, sperm production
What does estrogen/progesterone do during puberty
fat depostiion, ovulation, menstruation
role of oestrogen
- stimualtes thickening of the uterus lining
- inhibits FSH secretion
- stimulates secretion of LH
role of LH
stimulates ovulation
results in the formation of a corpus luteum (yellow body)
role of FSH
stimulates egg maturation in the follicles of the ovary
stimulates follicles in the ovaries to secrete oestrogen
role of progesterone
maintains and thickens the uterus lining
if fertiliastion doesn’t occur, levels drop and menstruation occurs
Sexually transmitted infection (STI)
an infection that is transmitter through sexual contact
Human immunodeficiency virus (HIV)
a pathogen that causes an STI
what may a HIV infection lead to?
AIDS
How to control the spread of STIs
- limiting number of sexual partners
- not having unprotected sex (use condoms)
- getting tested (if sex with multiple partners has occured)
- raising awareness by education programmes
methods of transmission of HIV
blood, semen and pre-seminal fluid, vaginal fluid, mucus and breast milk
menstrual cycle in full
FSH is released from the PITUITARY gland and this causes the egg to START to MATURE
FSH then triggers the ovaries to stimulate the PRODUCTION of ESTROGEN.
Once ESTROGEN is released, the UTERUS lining begins to THICKEN and the egg matures.
Once the egg matures, LH is released and this triggers OVULATION to occur and LH also triggers the production of progesterone.
After ovulation, the levels of estrogen drop.
This DROP in estrogen levels result in the release of progesterone,
As progesterone levels rise, this further thickens the UTERUS lining (prep for pregnancy)
Buf if the egg fails to get fertilised by the sperm, the levels of progesterone beings to decrease
Low levels of progesterone results in the uterus lining to break down
The uterus lining breaking down is what causes a period.
STI
sexually transmitted infection is an infection that is transmitted via body fluids through sexual contact
An example of a pathogen that causes an STI
HIV - human immunodeficiency virus
What can a HIV infection lead to?
AIDS
How are STI controlled (individual)
- know the sexual history of partner
- use a condom/femidom for barrier protection
- have a medical chekcl if symptoms occur
How are STI controlled (community)
- indivuals at greatest risk can be offered (free) tests for STIs
- Sexual contacts can be traced to identify sources of infection
How are STI controlled (Worldwide)
- education programs to prevent infection
- provision of antiviral
- developement of vaccines and antivirals
How HIV affects the immune system
(NOT IN SYLLABUS, can skip)
HIV virus attacks the immune system
Infects a certain type of lymphocyte.
(HIV avoids being recognised and destroyed by repeatedly changing its protein coat)
Reduces the number of lymphocytes of the immune system, and the number of antibodies that can be made
Decreasing the body’s ability to fight off infections, leading to AIDS
Fertility drugs how work
Fertility drugs contain FSH. It stimulates oestrogen production and the growth of follicles (egg-sacs) in the ovary
Methods of HIV transmission
Body fluids (often during unprotected sex), also through cuts and injecting drugs using shared needles.
social implications of using fertility drugs
May have multiple births
Problem with unused embryos
Issues with elderly parents
Religious objections to use of fertility drugs
Increases population
Idea that stress is associated with difficulty having children
