Human Reproduction Flashcards
What is a gonad?
An organ that produces sex cells in animals
What is ejaculation?
The release of semen from the penis
What are the associated glands?
Seminal vesicles, prostate and cowper’s gland
What are secondary sexual characteristics?
Features that distinguish males from females, apart from the sex organs themselves
What is the function of FSH in males?
Causes sperm producing cells in testes to divide by meiosis and produce sperm
What the function of LH in males?
Stimulates the testes to produce testosterone
What is infertility?
Inability to produce offspring
Give an example of male infertility?
Low sperm count
What is ovulation?
The release of an egg from the ovary
What is the menstrual cycle?
Series of events that occurs every 28 days on average in the female if fertilisation has not taken place.
Day 1-5 menstrual cycle
Endometrium breaks down and is shed- period. Meiosis occurs in ovary to produce egg. New egg surrounded by graafian follicle.
Days 6-14 menstrual cycle
Developing graafian follicle produces oestrogen. It causes endometrium to thicken again and prevents new egg developing.
Day 14 menstrual cycle
Ovulation occurs when graafian follicle bursts to release egg. Eggs passes to abdomen and then to fallopian tube. Egg available for fertilisation for 48hrs.
Days 14-28 menstrual cycle
Remains of graafian follicle develop into corpus luteum. This makes progesterone which causes endometrium to thicken more. Progesterone prevents new eggs forming. Egg will die by day 16. If not fertilised, corpus luteum starts to degenerate by day 22. This causes drop in progesterone which leads to menstruation on day 28
Example of female infertility?
Endocrine gland failure
Give an example of a menstrual disorder
Fibroids
What is insemination?
The release of semen into the vagina, just outside the cervix.
How do sperm enter egg?
Acrosome (head of sperm) contains enzymes that digest an opening into the egg. Sperm loses tail and head enter. Causes egg to produce fertilisation membrane which stops other sperm entering.
What is fertilisation?
When the nucleus of the sperm fuses with the nucleus of the egg, forming a diploid zygote.
What is birth control?
Methods taken to limit the number of children that are born
What is an abortion?
Termination of a pregnancy
What is contraception?
Deliberate prevention of fertilisation or pregnancy
What is implantation?
The embedding of the fertilised egg into the lining of the uterus
What is IVF?
Involves the removing of eggs from an ovary and fertilising them outside the body
what is a morula?
A solid ball of cells formed from a zygote by mitosis
What is a blastocyst?
A hollow ball of cells formed from a morula
What are germ layers?
The basic layers of cells in the blastocyst from which all adult tissues and organs will form.
What is gestation?
The length of time spent in the uterus from fertilisation to birth.
What is lactation?
The secretion of milk by the mammary glands of the female.
What is the function of the placenta?
- Provide embryo with oxygen, food, antibiotics, hormones, etc
- Remove carbon dioxide, salts and urea from embryo
Describe zygote development
1) fertilised
2) zygote divides rapidly. Becomes a morula after 3 days
3) 5 days after fertilisation, morula forms hollow ball of cells called a blastocyst. Outer cells form trophoblast. This will form membrane around embryo. Inner cells will form embryo.
4) blastocyst pushed down fallopian tube to uterus.
How does the embryo develop?
- 10 days after fertilisation, inner cells form embryonic disc. This develops into the 3 germ layers. The middle layer (mesoderm) divides into an outer and inner layer. Gap between them (coelom) allows organs to develop.
- After 4 weeks from fertilisation, heart forms and beats, brain and umbilical cord forms.
- Week 5, organs and limbs start to form.
- Week 6, eyes visible and mouth,nose and ears form.
- Week 8, tail is gone. Face is human and major organs formed. Gonads distinguishable and cartilage turns to bone. It is a foetus
- Week 8 onwards, foetus grows.
- Third mth, eyes low in face and widely spaced. Ossification occurs, muscles and nerves become coordinated, foetus kicks, sucks thumb and grows milk teeth.
- Gestation lasts 266 days (38 weeks/9 mths).
Describe birth
- During pregnancy progesterone and oestrogen produced in great amounts. After week 12, placenta makes them.
- Immediately before birth placenta stops producing progesterone. Uterus contracts
- Pituitary gland produces oxytocin. This causes labour.
- Labour divided into 3 stages.
- Stage 1 (12hrs), contractions push foetus down to cervix. Waters break.
- Stage 2 (20mins-1hr), cervix dilates. Baby pushed out. Umbilical cord clamped and cut.
- Stage 3 (within 5-30mins of birth), afterbirth expelled.
Describe lactation
- Breasts produce colostrum for first few days.
- During pregnancy, progesterone prevents production if prolactin. Once baby born prolactin produced and milk is produced.
- Once breast- feeding stops, breasts stop producing milk.
What are the benefits of breast- feeding?
- Contains ideal balance of nutrients
- Antibiotics
- Reduces risk of breast cancer.
What does the ectoderm produce?
Skin, nails, hair, nervous system
What does the mesoderm produce?
Muscles, skeleton, organs
What does the endoderm produce?
Inner lining of digestive, respiratory and excretory systems
