Y4 Unit 2a - Reproduction in humans

Parts of the male reproductive system

testis, scrotum, sperm duct, prostate gland, urethra, penis

Main function of male reproductive system

1. Produce store transport sperm and protective, nutritious fluid (semen)

2. Discharge sperm within female reproductive tract

3. Produce, secrete male sex hormones

Testis (p. Testes)

• produces sperm and testosterone (male sex hormone) → develop and maintenance of secondary sexual characteristics

• Male gonads located outside abdominal cavity in scrotum

• Outside the main body, so sperm-forming cells 2ºC cooler than body temperature, allowing them to function normally

scrotum

• loose pouch like sac of skin that hangs behind penis

• Has special muscles in wall of scrotum allowing contraction and relaxation, move testicles closer to body (warmth) or further (cool temperature)

sperm duct

(Vas deferens)

• deliver sperm —> urethra during ejaculation

• Ejaculation: caused by contraction of muscles along sperm ducts release 5ml of semen

• Only 5% semen consists sperm

Prostate gland

prostate gland is at the base of the urinary bladder, in front of rectum

Secretes fluid that nourishes sperm and provides protection from natural acidity of vagina

Semen

has nutrients and enzymes to nourish sperm and stimulate them to actively swim

Urethra

tube passes from bladder → centre of penis → outside of body

• direct connection of male reproductive and urinary system

Penis

1. Erectile tissue that can fill with blood, causes erection

2. Deliver sperms to vagina

3. Head covered by foreskin (that can be removed via circumcision)

Sections of the sperm and physical characteristic

Head, middle piece, tail (flagellum); streamlined shape

Head

• 2.5 micrometer

• ✅large nucleus with small amount of cytoplasm + haploid set chromosomes

Middle piece

Has many mitochondria → provide energy for sperm to swim

Tail (flagellum)

Beating movement enables swimming, letting sperm become motile

Sperm

Male gamete, many produced after maturity

60 micrometer

Parts of female reproductive system

Ovary, oviduct, uterus, cervix, vagina

Main function of female reproductive system

1. Produce ova/egg cells (singular ovum) for reproduction

2. Transport ova to site of fertilisation (oviduct/fallopian tube)

3. Provide safe and favourable environment for fetal development in uterus

4. Product female sex hormone that maintain reproductive cycle

Ovary

• site of gamete production

• Follicles have: 1 developing egg cells (ovum) surrounded by cells to nourish, protect it

  • Produce oestrogen and progesterone (by corpus luteum)

• Born with 1 - 2 million follicles with immature eggs, only several hundred mature ova will be released

• 1 cycle = 1 follicle = 1 egg released

Purpose of female hormone production

Development and maintenance of secondary sexual characteristics in females

Oviduct/fallopian tube

• where matured egg is released by ruptured follicle and fertilised

• Narrow muscular tube (ovary to uterus)

• Has funnel like opening lying close to ovary

  • Make easier for egg to enter oviduct

• Inner surface lined with cilia

  • Cilia sweeps egg towards uterus

Uterus

• where fetus will develop

• Has thick elastic muscular wall (smooth tissue muscle)

  • Contracts

  • Lined with endometrium wall where embryo will implant and grow

Cervix

• narrow ring of muscle at bottom of uterus

• Opens up into vagina, allows flow of menstrual blood out and direct sperm to uterus

Vagina

Lead from cervix to outside, where semen deposited, just behind opening of urethra

Ovum (general)

• Female gamete

• fixed number at birth

• 70 000 potential egg cells about 500 ever become mature within 2 ovaries

• 1 mature egg released every month from time of physical maturity until 45 -55 years old

Ovum (cellular)

• spherical, 120 - 150 micrometer

• Has abundant cytoplasm that may contain small amount of yolk

• Surrounded by cell membrane → surrounded by outer membrane (jelly coat)

• Jelly coat changes during fertilisation, prevent more sperms from entering

Differences between male female gamete

Male gamete

• has head middle piece tail

• Nucleus has either X or Y chromosome

• 60 micrometer long, diameter 2.5 micrometer for head

• Has tail to enable swimming

• Large number released per ejaculation

Female gamete

• spherical in shape

• 1 X chromosome

• Diameter 120 - 150 micrometer

• Passive movement of egg along oviduct as movement of cilia and peristalsis of oviduct wall takes place

• One egg released per month