1. Sexual Reproduction in
Humans
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2. Female urinogenital system
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3. Female reproductive system
• Ovaries:
– site of production of the female gametes (ova) and
female sex hormones (oestrogen and progesterone)
• Oviducts (Fallopian tubes):
– collect secondary oocytes released by ovaries
– sweeps egg towards uterus
– site for fertilisation
– end in funnels fringed with feathery processes called
fimbriae
• Uterus (womb):
– expands during pregnancy
– consist of myometrium and endometrium (lining
which is shed every month unless pregnant)
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4. • Cervix:
– narrow junction between uterus and vagina
where ring of muscle can close off uterus
• Vagina:
– site where semen is deposited from the penis
during sexual intercourse
– the birth canal during childbirth
– can enlarge to allow entry of erect penis or
exit of baby due to elastic tissue and folded
epithelium lining
– epithelium secretes acid which deter growth
of harmful microorganisms
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5. • Vulva:
– labia majora and labia minora
– protect the openings of the vagina and
urethra
• Clitoris:
– female equivalent of the penis
– contains many nerve endings and swells with
blood, becoming erect when sexually
stimulated
– source of sexual arousal during sexual
intercourse
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6. Male urinogenital system
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7. Male reproductive system
• Testis:
– site of production of the male gametes
(spermatozoa/sperm)
• Seminiferous tubules:
– cells lining the walls produce the sperm
• Epididymis:
– sperm are stored while completing their
maturation
– fluid is absorbed to make sperm more
concentrated
– where sperm become mobile
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8. • Scrotal sac/scrotum:
– sac of skin containing the 2 testes which
hangs from the main body cavity and helps
keep the sperm about 3ºC cooler than normal
body temperature
• Vas deferens/vas deferentia:
– tube which carries sperm out of the testis to
the urethra
– sperm storage
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9. • Prostate gland, Cowper’s glands and
seminal vesicles:
– secrete fluid for carrying the sperm and in which
sperm can swim (semen)
– alkaline fluids (Cowper’s and seminal vesicles) to
neutralise the acidity of remaining urine in urethra
– secretes mucus (prostate)
– secretes fructose (vesicles)
• Penis:
– contains urethra which carries sperm to outside world
– contains special spongy tissue which can fill with
blood when the male is sexually stimulated, causing it
to become erect and rigid
– ejaculates semen into vagina during sexual
intercourse
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10. Gametogenesis
• Formation of gametes in the gonads
(testes in the male and ovaries in the
female)
• Involves meiosis in nuclei of diploid
‘mother cells’ to form haploid gametes
• Formation of sperm – spermatogenesis
• Formation of eggs – oogenesis
• Mother cells known as oocytes and
spermatocytes
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11. Spermatogenesis
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12. • Process starts between the ages of 11 and 15
and will continue for life
• Gametes produced in vast numbers in a
continuous production line of several thousand
per second (> 100 million/day)
• In testes (walls of seminiferous tubules)
• From outer layer of tube (germinal epithelium)
towards centre of tube where mature sperm
break away from wall and float down towards
epididymis for storage
• Sertoli cells:
– Secrete fluid found in lumen of tubes
– Sperm development take place in close association
– Assist in complex modelling of sperm, particularly
spermatids (phagocytosis of spermatid cytoplasm)
• Interstitial cells (cells of Leydig):
– Secrete the male sex hormone (testosterone)
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13. Photomicrograph of t.s. of
mammalian testis
Layer of spermatogonia
attached to epithelium and
dividing by mitosis
Primary spermatocytes dividing
by meiosis and moving towards
lumen
Haploid spermatids maturing
into spermatozoa
Mature spermatozoa released
into lumen
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14. Seminiferous tubules and interstitial
cells
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15. Sperm
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16. • Acrosome: contains hydrolytic enzymes
needed to digest a path to the egg at
fertilisation
• Nucleus: carries haploid set of
chromosomes
• Axial filament: responsible for the wave-
like beating of the tail which propels
through fluid surroundings ; microtubules
have ‘9+2’ arrangement
• Centriole: form microtubules
• Middle piece and tail: propulsion
• Mitochondria: energy for beating of tail
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17. Oogenesis
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18. • Process starts before birth
• Outer layer of ovary (germinal epithelium) produces primary
oocytes and follicle cells which multiply and cluster around
the oocytes, forming structures know as primary follicles (~2
million already present at birth)
• By birth, each primary oocyte has started to divide by meiosis
but stops once chromosomes pair up in prophase I
• Once sexually mature, one primary follicle per month is
stimulated to complete development into a Graafian follicle
(surrounded by layer called theca which secretes the hormone
oestrogen)
• Follicle cells multiply and several fluid-filled spaces develop which
fuse to form one space
• Primary oocyte completes meiosis I and divides unequally into 2
• Smaller daughter cell (polar body) disintegrates
• Larger daughter cell (secondary oocyte) – released at
ovulation with some of the surrounding follicle cells
• After ovulation, empty follicle develops into a corpus luteum
(yellow body) which disintegrates unless fertilisation takes place
• Corpus luteum secretes hormone progesterone
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19. Sequence from a primary follicle to
a secondary follicle
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20. Photomicrograph of mature follicle
Ovary tissue
Follicle cells
secreting
oestrogen
Fluid-filled
cavity
Haploid secondary oocyte held at metaphase II
of meiosis, ready to be released at ovulation
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21. Secondary oocyte and egg
• Egg is largest cell in human body
• Contains no conspicuous yolk
• Obtains nutrients from surrounding cells
• Lysosomes function at fertilisation
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