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