Human reproduction Flashcards
Define sexual reproduction
Sexual reproduction is the fusion of the haploid nuclei of the male and female gametes to form a zygote, producing a new organism that is genetically distinct from its parents
Describe the structures and functions of the testes
- Produces sperms
- Produces testosterone
Describe the structures and functions of the epididymis
- Stores inactive sperms from testes temporarily
Describe the structures and functions of the scrotum
- Pouch like sac that holds the testes
- Outside main body cavity to keep testes slightly below body temperature for optimal sperm development
Describe the structures and functions of the urethra
- Provides common passage for discharge of semen and urine
Describe the structures and functions of the sperm duct
- Carries sperms from testes to urethra
Describe the structures and functions of the prostate gland
Secretes fluid to:
- Activate and nourish sperms
- Neutralise acidity in female reproductive tract
- Provide medium for sperms to swim in
Describe the structures and functions of the sperm
- Head has acrosome containing enzymes that break down egg membrane to allow sperm to enter egg
- Middle piece contains many mitochondria to provide sperm with energy
- Flagellum just exists
Describe the structures and functions of the ovary
- Produces ovum
- Produces progesterone and oestrogen
Describe the structures and functions of the oviduct
- Site of fertilisation
- Transports ovum to uterus using cilia
Describe the structures and functions of the uterus
- Site of implantation
- Offers protection and stable environment for embryo development
- Muscular walls contract to expel fetus at birth
Describe the structures and functions of the cervix
- Connects uterus to vagina
Describe the structures and functions of the vagina
- Birth canal for fetus
Describe the structures and functions of the ovum
- Surrounded by additional outer membrane and layers of follicle cells
- Abundant cytoplasm contains small amount of yolk to provide nutrients for embryo
- Spherical
What are the stages in the menstrual cycle
Menstruation
After menstruation
Ovulation
After ovulation
Describe menstruation
- Low levels of oestrogen and progesterone cause uterine lining to break down and shed in the form of menstrual blood
Describe after menstruation
- Overy produces oestrogen
- Oestrogen stimulates the repair and growth of uterine lining
- Uterine lining becomes thick and spongy with blood vessels
Describe ovulation
- One of the 2 ovaries releases an ovum into the oviduct
Describe after ovulation
- Ovary produces progesterone
- Progesterone stimulates uterus to maintain uterine lining by causing it to thicken further in preparation for implantation
- Progesterone inhibits ovulation and further development of ovum
- Oestrogen levels decrease
- Progesterone levels decrease and uterine lining breaks down if ovum not fertilised
Which is the ovulation day
Last day of cycle minus 14
When is the fertile period
+ or - 3 days after ovulation day
What happens after ovum is fertilised
- Embryo secretes the human chorionic gonadotropin, which causes ovary to continue producing oestrogen and progesterone
Describe fertilisation
- Ovum released into ovary is surrounded by layers of follicle cells
- Acrosome of sperm releases enzymes to disperse follicle cells and break down part of ovum membrane
- Only 1 sperm can enter the ovum
- Nucleus of haploid sperm fuses with nucleus of haploid ovum, forming a diploid zygote
- Membrane of ovum changes the moment a sperm enters to prevent others from entering
Describe implantation
- Cilia lining the oviduct along with peristaltic contractions move the zygote along the oviduct towards uterus
- Zygote divides by mitosis to form a hollow ball of cells called the embryo
- Developing embryo moves down the uterus and embeds itself in the uterine lining
Describe the development of placenta and amniotic sac
- After implantation, chorionic villi grow from embryo into uterine lining
- Villi and uterine lining in which villi are embedded in make up the placenta
- Umbilical cord attaches embryo to placenta
- A membrane called the amniotic sac develops around the same time, and it encloses the embryo in a fluid-filled space called amniotic cavity
- Fluid is known as amniotic fluid
What are the functions of the amniotic fluid
- Absorb shock to support and cushion fetus before birth
- Protects fetus from mechanical injury
- Allows fetus a certain degree of movement
- Lubricates vagina during birth
What are the functions of the placenta
- Allows oxygen and nutrients to diffuse from maternal blood to fetal blood
- Allows metabolic waste products to diffuse from fetal blood to maternal blood
- Allows protective antibodies to diffuse from maternal to fetal blood
- Produces progesterone which maintains uterine lining in healthy state for pregnancy
Explain how the placenta is adapted to its functions
- Chorionic villi increase SA:V to increase rate of diffusion of substances between maternal and fetal blood
- Chorionic villi surrounded by maternal blood supplied at low pressure, ensuring there is sufficient time for transfer of materials between maternal and fetal blood
- Fetal blood capillaries separated from maternal blood by a thin layer of tissue, decreasing distance that substances need to diffuse over, increasing diffusion rate
What are the functions of the umbilical cord
- Contains 2 umbilical arteries that transport deoxygenated blood and metabolic waste products from fetus to the placenta
- Contains 1 unbilical vein that transports oxygenated blood and nutrients towards fetus
What is HIV
- Human immunodeficiency disease
- Destroys body’s immune system by destroying lymphocytes
- Body not able to produce sufficient antibodies for protection
How can HIV be transmitted
- Blood transfusion
- Sexual intercourse
- Passed from mother to fetus
