Reproduction in Humans
Sexual Reproduction
Involves fusion of reproductive cells AKA. gametes
Gametes
Come frm. a male & female parent
Gametes prod. in special reproductive organs AKA. gonads
Gonads
Male
Female
Testes, prod. sperms (male gametes)
Ovaries prod. ova (female gametes)
Mating process required for sperm & egg to meet
No. of chromosomes
VS. Human/Body cells
Diploid (2n)
46
Sperm/Egg
Haploid (n)
23
Upon fusion of sperm + egg
Zygote formed
Diploid (2n)
46
Male Reproductive System
Testis
Scrotum
Sperm duct
Urethra
Penis
Prostate gland
Prod. sperm + male sex hormones (testosterone)
Pouch-like sac outside body cavity
Maintains lower temp. thn. body for development of sperms
Pathway traveled by spemrs aft. release frm. testis
Activates sperms thru. secretion of slippery fluid tht. cont. enzymes & nutrients
Mixture of fluid + sperms is known as semen
Erectile organ
Become erect + hard during sexual intercourse to enter vagina & deposit semen cont. sperms
Due to blood filling up spongy tissue in penis
Tube which extends frm. bladder to penis to outside of body
Urine & semen passes thru. urethra but nvr. @ same time
Due to sphincter muscles @ base of urinary bladder, prev. urine frm. coming out during ejaculation
Sperms
Prod. thru/o lifeitme of a male aft. physical maturity
Head
Middle piece
Tail
Acrosome
(Small amt.) Cytoplasm
Nucleus
Cont. enzymes used to break down part of egg membrane to allow sperm to penetrate during fertilisation
Carries one haploid set of chromosomes
Numerous mitochondria
Provides sperm energy to swim to egg
Flagellum
Beating movement enables sperm to be motile & swim towards egg
Female Reproductive System
Oviduct
Ovary
Uterus
Uterine lining
Cervix
Vagina
Narrow muscular tube w. funnel like opening
Leads frm. ovary to uterus
Mature eggs released frm. ovary into oviduct to be fertilised
Prod. eggs + female sex hormones (oestrogen, progesterone)
Whr. fetus develops during pregnancy
Has elastic muscular walls
Soft, smooth inner lining of uterus
Important for embryo implantation
Enables contraction to push out fetus during birth
Circular ring of muscle @ lower end
Can enlarge to allow delivery of fetus
Whr. semen is deposited during sexual intercourse
Leads frm. cervix to opening on outside
Ovum
Present in ovaries of female @ birth
Large nucleus
(Large amt.) Cytoplasm
Cell surf. membrane
Cont. one haploid set of chromosomes
May cont. small amt. of yolk
Surrounded by an outer membrane
Only 500/70 000 eggs will mature
Released frm. time female becomes physically mature until 45-55 yrs. of age
Puberty
Definition
Secondary sexual characteristics developed
Menstruation
Stage of human growth & development in which person becomes sexually mature
Sex organs mature
Sex organs secrete sex hormones
Testosterone
Oestrogen + Progesterone
Male
Female
Hair (pubic regions, under armpits, face)
Penis + Testicles incr. in size
Larynx enlarges
Voice deepens
Prod. of sperm begins
Hair (pubic regions, under armpits)
Breasts & uterus enlarge
Hips brosden
Menstruation & ovulation begin
Menstrual cycle
(Day 6 to 13) Follicle stage
(Day 14) Ovulation
(Day 1 - 5) Menstrual flow
Process of blood/menses being discharged frm, uterus via vagina
Avg. is 28 days
Menopause
Natural variation in length ranging frm. 21 - 33 days
Can be affected by stress, illness, unbalanced diet or malnutrition
Cond. whr. female eventually stops prod. eggs, ending menstrual cycle
Cycle of events taking place in female repro. system every month
Uterine lining breaks down, flows frm. uterus out of body thru. vagina
Prod. of oestrogen
Causes repair & growth of uterine lining
Making it thick & spongy w. blood vessels
Secretion of progesterone
Prepares uterine lining for fertilised egg
Causes it to thicken further by supplying it w. blood capillaries
Fertile period
Infertile period
Day 11 - 16
Egg can survive frm. Day 14 - 16
Sperms can live for 2 - 3 days in fem. repro. system
Rest of days
Sexual Intercourse
Sexual arousal
Penis becomes erect (blood pumped into spongy tissue)
Semen cont. 100 mil. sperms ejaculated into vagina
Sperms swim up oviduct to meet egg
Only one sperm can enter + fertilise egg
Fertilisation
Acrosome from sperm releases enzyme to disperse follicle cells
Breaks down part of egg membrane to allow sperm to enter
Only one sperm nucleus enters egg
Sperm nucleus fuse w. egg nucleus
Forming fertilised egg
AKA. Zygote
As soon as sperm enters egg, membrane of egg changes so no other sperm enters
Remaining sperms tht. did not fertilise egg eventually die
Implantation
Cilia lining sweeps fertilised egg along oviduct
Zygote divides
Forms embryo
Embryo takes arnd. a week to reach uterus
May float freely for another 2 days
Happens whn. embryo becomes embedded in uterine lining
Sexually-transmitted Infections
Definition
Diseases spread thru. sexual intercourse
Possible causes
Bacteria or viruses
How it is spread
Via semen/fluid in vagina
Blood of infected getting into bloodstream of uninfected
AIDS
Caused by HIV (Human Immunodeficiency Virus)
Destroys body’s immune system
Infected person is unable to prod. sufficient antibodies to act against bacteria & virus
Infections tht. are nromally mild may become fatal
Symptoms
Severe diarrhoea, lasts months
Chronic/persistent fever
Pneumonia
Widespread tuberculosis, affects many organs at one time
Cancer of blood vessels
Brain infection
Mode of transmission
Sexual intercourse w. infected person
Sharing of hypodermic needles w. infected person
Blood transfusion w. blood frm. infected person
Passed frm. mother to fetus during pregnancy
Steps to prevent
Keep to one sex partner
Do not have sex
Make sure needles used for acupuncture treatment/tattooing/ear piercing are sterilised
Use a condom to reduce risk of infection
Do not abuse drugs
Drug addicts tend to share needles
Do not share instruments like razors/toothbrushes as they cld easily break the skin & get contaminated w. blood