REPRODUCTION IN HUMANS Flashcards
What are the functions of the two hormones in the female reproductive system and what do they secrete?
Estrogen:
Causes repair and growth of uterine lining, becoming thick and spongy with blood vessels.
Inhibits FSH production at high levels.
Progesterone:
Maintains uterine lining by causing it to thicken further and be richly supplied with blood capillaries, preparing it for implantation.
Inhibits ovulation and FSH
What happens when no fertilisation occurs?
Egg breaks down. LH production inhibited by a high conc of progesterone in the blood. The drop in LH level causes Corpus Luteum (CL) to break down. When the CL breaks down , progesterone is not secreted. Without progesterone, the thickened uterine lining cannot be maintained so it breaks down. The lining flows from the uterus together with some blood through the vagina, marking the beginning of menstruation. FSH is then produced by the pituitary gland and the cycle repeats
What happens when fertilisation occurs?
The egg becomes a zygote then an embryo. The embryo embeds itself into the uterine lining. The embryo secretes a hormone which prevents the CL from breaking down until the placenta is formed. The CL continues to secrete progesterone and estrogen until placenta is able to take over the production.
Why is the fetal blood separated from the maternal blood?
The blood pressure of the mother could kill the fetus, as it is much higher than the fetus.
The blood group of the fetus may be different from the mother. If the blood was allowed to mix, blood cells may agglutinate and harm both mother and fetus.
What are the functions of the placenta?
Allows oxygen and dissolved food substances to diffuse from maternal blood to fetal blood.
Allows metabolic waste/excretory products such as urea and carbon dioxide to diffuse from fetal to maternal blood.
Allows protective antibodies to diffuse from maternal blood to fetal blood and protect the fetus against diseases like german measles
Produces progesterone, maintaining the uterine lining in a healthy state during pregnancy
What are the functions of the umbilical cord? (U.C)
U.C attaches fetus to placenta, containing the blood vessels of the fetus.
2 umbilical arteries that transported deoxygenated blood/metabolic waste products from the fetus to the placenta.
1 umbilical vein that transports oxygenated blood and food substances fro the placenta to the fetus.
What are the functions of amniotic fluid?
- Supports and cushions fetus before birth.
- Shock absorber against mechanical damage
- As it cannot be compressed, it protects the fetus from physical injury.
- Allows the fetus a certain degree of muscular development that promotes muscular development.
- Lubricates fetus in birth canal.
Describe the sequence of events that occur after the human egg cell is fertilised which enables it to develop and survive in the uterus.
The Zygote is swept to uterus by cilia lining of oviduct and peristaltic action of oviduct walls.
Zygote undergoes cell division
Embryo implants into the endometrium
Villi grow from embryo into endometrium to form placenta.
Placenta allows uterus to receive glucose and oxygen from mother, enabling it to survive.
What are the hormone cycles in the female body?
FSH —> estrogen —> LH —> Progesterone—> limits FSH
Describe the menstrual cycle.
After the ovum is released, an egg can survive for 24h. For a 28 day cycle ovulation occurs on day 14.
Describe fertilisation.
The ovum released from ovary is usually surrounded by a few layers of follicle cells.
To penetrate the egg, the acrosome of the sperm release an enzyme to disperse the follicle cells and breakdown part of the egg membranes.
Only 1 sperm nucleus enters the egg. Haploid nuclei fuse, diploid zygote formed. As soon as this occurs membrane of egg changes so no other sperms can enter. Remaining sperm die.
