Reproduction in Man Flashcards
What is the function and structure of the male gamete (sperm cell)
Swims towards the ovum and its nucleus will fuse with the ovum’s nucleus during fertilisation
To deliver the 23 (haploid) chromosomes in the nucleus, which will fuse with the egg cell’s nucleus (haploid) during fertilisation, forming the zygote (diploid)
Head: acrosome and nucleus, middle piece, flagellum (tail)
Function of the sperm’s acrosome
Vesicle containing enzymes that help the sperm break down part of the egg membranes, so sperm can penetrate the egg during fertilisation
Function of sperm’s nucleus
Contains 23 chromosomes (haploid)
Function of sperm’s middle piece
Numerous mitochondria, releases large amounts of energy during respiration for sperm to swim
Function of sperm’s flagellum
Enables the sperm to be motile and swim towards egg
What is the largest cell in the human body?
Female gamete, can be seen without a microscope
Function of ovum’s nucleus
Contains 23 (haploid) chromosomes
Only 1 X chromosomes
Does not have Y chromosomes
Function of ovum’s mitochondria
Large numbers of mitochondria
Zygote formed after fertilisation contains mainly maternal mitochondria
Function of ovum’s cytoplasm
Abundant cytoplasm
May contain a small amount of yolk
Difference between sperm and ovum
Sperm cell is small, 60um. Ovum is large, 120-150um
300 million sperm per ejaculate, 1 mature ovum during monthly ovulation
Constant production by testes of sperm, all potential ovum present at birth
Sperm are motile, ovum are not
Both contains 23 chromosomes, sperm either X or Y, ovum only X
What is the function of the male reproductive system?
Production of sperm, and delivery of semen to the female reproductive system during sexual intercourse
What are the parts of the male reproductive system?
Testes, epididymis, scrotum, sperm duct (vas deferens), prostate gland + seminal vesicle + Cowper’s gland, urethra, penis
Function of testes
Production of sperm
Production of male sex hormones eg testosterone
Function of epididymis
Where sperm is temporarily stored before entering the sperm duct (vas deferens)
Function of scrotum
Found outside main body cavity, contains testes
Allows testes to be exposed to temperatures lower than body temperature for proper sperm development
Function of the sperm duct (vas deferens)
Sperm released from testes travel through the sperm duct, opens into urethra
Only sperm travel in sperm duct
Function of prostate gland and seminal vesicle and Cowper’s gland
Secretes semen that mixes with sperm
Contains nutrients to nourish the sperm
Actives sperm, allowing them to swim faster
Function of urethra
Tube which passes from bladder through the centre of the penis to outside the body
Both semen and urine pass through urethra
Function of penis
Erectile organ
Enters woman’s vagina during sexual intercourse to deposit semen, containing sperm
Parts of the female reproductive system
Ovaries, oviducts (Fallopian tubes), uterus, cervix, vagina
Function of ovaries
Produces ova (during foetal development)
Releases a mature ovum monthly during ovulation
Production of female sex hormones (like progesterone and oestrogen)
Function of oviducts
Muscular narrow tube
Mature eggs are released here for fertilisation to occur
Function of uterus
Elastic, muscular organ that can contract to push foetus out during birth
Where foetus develops during pregnancy
Function of the cervix
Lower, narrow part of the uterus
Ring of muscle
Dilates during childbirth
Function of the vagina
Birth canal that leads from the cervix to the outside
Semen deposited here during sexual intercourse
Define fertilisation
Fertilisation is the process where sperm nucleus fuses with the ovum nucleus to form the zygote
What happens after fertilisation till implantation?
Fertilisation occurs in the oviduct, forming the diploid zygote (fertilised ovum)
The zygote divides via meiosis to form embryo (a ball of cells)
Cilia lining the inner surface of the oviduct sweep the zygote along the oviduct towards the uterus, aided by peristaltic movements of the oviduct
Embryo —> blastocyst reaches uterus in 5 days
Implantation on day 8, embryo embedded into uterus lining (endometrium)
Placenta and umbilical cord develop after implantation
What is the amniotic sac?
Thin and tough transparent membrane that contains amniotic fluid and the foetus formed in the uterus
Function of amniotic fluid
- A liquid that surrounds the foetus in the amniotic sac
Protects the foetus by cushioning against impacts
Allows foetus to move freely during pregnancy
Lubricates and reduces friction in vagina during birth
What is the placenta and its function?
- An organ of exchange that allows nutrient uptake, waste elimination and gaseous exchange between foetus and mother’s blood supply
- Secretes progesterone, maintaining health endometrium throughout pregnancy
Structure and function of umbilical cord
Connects foetus to the placenta
Two umbilical arteries, transport blood and waste away from foetus to placenta
One umbilical vein, transports blood rich in nutrients and oxygen from placenta to foetus
(Arteries and veins composition different for umbilical)
Why are the foetal and mother’s blood supply not continuous and separated by the placenta?
If the blood group of mother and foetus are different, mixing could result in fatal agglutination to both
Mother’s blood pressure also much higher than foetus’, mixing would kill foetus by pressure
How do exchange of substances in the placenta occur?
Via diffusion:
Useful substances like oxygen, glucose, amino acids diffuse from mother to foetus. Protective antibodies too.
Waste substances like carbon dioxide, urea (excretory and metabolic waste products) from foetus to mother
What are the placenta’s villi for?
Finger-like projections that further increase surface area to volume ratio, enhancing speed of diffusion for substances across the placenta
How long is the menstrual/ovarian cycle?
Typically 28 days
Natural variation caused by an unbalanced diet or malnutrition, high stress, lifestyle factors or illness
What is a follicle?
The ovum and its surrounding supporting follicle cells
What happens during the follicular phase and when is it?
Primary follicles begin to mature to form secondary follicles, due to follicle stimulating hormone (FSH) secreted by the pituitary gland,
Follicle cells secrete a fluid
Day 6-13
What is the Graafian follicle?
The one follicle that fully matures and releases the mature ovum (due to luteinising hormone LH)
What happens to the Graafian follicle after ovulation?
Develops into the corpus luteum due to LH
Acts as a temporary endocrine gland, secreting oestrogen and progesterone
If fertilisation does not occur, the corpus luteum degenerates
Define ovulation
Ovulation is the release of a mature ovum from one of the two ovaries
What are the phases before and after ovulation, and what occur then?
Follicular phase is the period before ovulation, primary to Graafian
Luteal phase is the period after ovulation, formation of corpus luteum
Overview of the menstrual cycle
1-5: menstruation occurs, breakdown and expelling endometrium due to low oestrogen and progesterone
6-13: repair and thickening of endometrium, stimulated by oestrogen from developing follicles
14: ovulation occurs, mature ovum released due to LH surge due to oestrogen rise
15-28: luteal phase. maintaining and thickening endometrium, progesterone stimulates endometrium’s tiny glands to secrete nutrient-filled fluid, progesterone increases endometrium blood supply to ready it for implantation if fertilisation occurs
Endocrine gland, target organ and action of oestrogen
From ovaries and developing follicles (day 5-13), targeting endometrium (thickens and repairs it)
Endocrine gland, target organ and action of progesterone
From ovaries, corpus luteum, targeting endometrium to thicken and prepare for fertilisation and pregnancy, inhibiting ovulation and FSH production, no more new ovum
When are the fertile and infertile phase from? Lifespan of gametes?
Fertile: day 12-16
Infertile: 1-11, 17-28
Sperm and eggs can survive for approximately two days in the female reproductive system
What happens if fertilisation does not occur?
Corpus luteum degenerates after about 8 days, decreasing progesterone levels
Endometrium no longer maintained, disintegrates and removed via menstruation
Failure rate of chance (no contraception)?
90%
What is abortion?
The termination of a pregnancy resulting in the death of embryo or foetus
Hormone contraceptives: what and how?
Oral, patches, injections
Increases oestrogen and progesterone, pituitary gland does not secrete LH, no ovulation
How do spermicides work?
Chemically kills sperm, used with a condom or diaphragm
How do IUDs work and what do they stand for?
Intrauterine device
Copper (poisonous to sperm) IUD interferes with embryo implantation
How do condoms work
Physical barrier preventing sperm from entering vagina
Only contraceptive that protects against HIV and STDs
How do contraceptive diaphragms work?
Physical barrier that blocks cervix entrance
What is rhythm contraception?
Abstinence during fertile period
How do vasectomy and tubal ligation work?
Vasectomy cutting and cause rising the vas deferens, so sperm cannot leave duct
Tubal ligation cutting and cauterising Fallopian tubes, preventing ovum and sperm from meeting
Name of STI
Acquired Immune Deficiency Syndrome (AIDS)
AIDS is caused by?
Human Immunodeficiency Virus (HIV)
How does HIV work?
It attacks a type of white blood cell, weakening the body’s immune system
HIV+ does not mean having AIDS
Stage 3 HIV infection = AIDS
Someone with HIV is more at risk for opportunistic infections
How can HIV be spread?
Sexual intercourse (abstinence or condom), blood transfusions (screening in blood banks), pregnancy (caesarean and no breastfeeding), sharing contaminated needles (sterilisation)
