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Block
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Bio 12 Notes: Reproductive System Intro & Male System
I) Intro
-many organisms reproduce asexually (1 parent only): binary fission, parthenogenesis
-advantages:
-disadvantage:
-sexual reproduction happens in most organisms (multicellular ones)
-advantages
-
: sexual cell with ½ the # of chromosomes which combine with gamete of
opposite gender during
-
: male gamete, usually small and motile
-
: female gamete, usually large and non-motile with large nutrient store to
support embryonic development, often called an egg cell
II) Male Reproductive System (more parts, simpler hormones)
A) Main Structures
1)
(plural = testes):
-develop in abdomen, descent
2 months-few days before
birth into the scrotum through
the inguinal canal. Cannot
retreat: membrane grows and
blocks canal
(scrotal sac) holds testes
outside body where _
 37 degrees Celsius = too hot. Ideal temp to keep sperm alive:
32-35 degrees
-testes mostly a “tangle” of
-seminiferous tubules are lined with undifferentiated
-
in tubules assist sperm maturation by
providing nutrients and phagocytizing excess cytoplasm from
meiotic/mitotic events
-testes also composed of
2)
: receives sperm from seminiferous tubules via small tubes called _
-
cells up to several weeks
-sperm undergo further maturation here, leave during ejaculation
3) ________________________: transport sperm (from each epididymis) up to
4) ejaculatory duct: location where
and
where 3 accessory glands secrete
(swimming medium for sperm cells)
-semen = ____________________ & _________________________
-during ejaculation ~3.5 mL semen is released with 400-500 million sperm cells
5) Accessory glands
a)
(2): secrete fluid into ejaculatory duct that contains
1)
:
source to produce ATP for swimming sperm
2)
: hormones that cause
that aid
through female. (sperm arrive at oviducts in ~ 5 minutes
with help of prostaglandins)
b)
(1): secretes a
(~pH 7.5) into
ejaculatory duct
-vagina is acidic which kills bacteria, but also sperm cells
-recall: prostate positioned at base of bladder with urethra running through it. Trouble with
urination in male is often a sign of enlarged prostate, a precursor to prostate cancer
c)
(2) (aka bulbourethral glands): secretes
which aids passage of sperm and protects sperm from
(from passage of urine)
6)
: conducts semen from
-recall: also transports urine from bladder
-passes through
(organ of copulation) that is inserted into vagina
during
-allows efficient transfer of sperm: deposited at cervix (base of the uterus) which is much
closer to “target”
-contains
which fills with blood during sexual arousal
causing erection: blood enters erectile tissue and fills normally empty sinuses. Penis expands
in length and girth. Average erect penile length: 13-15 cm (average flaccid length: 9-10 cm)
-erectile tissue allows
B) Spermatogenesis: creating sperm cells
-produced from puberty until late in life (world’s oldest father = 94)
-__________________________________: stem cells inside seminiferous tubules
-in adolescence, these respond to an increase in testosterone (secreted by interstitial cells) and
differentiate into 1 spermatocytes
-undergo meiosis 1 to form 2 spermatocytes
-undergo meiosis II to form ___________________ (________________________)
-spermatids differentiate and mature into sperm cells with 3 main parts
1) _____________: nucleus & a limited amount of cytoplasm, and the ____________________
(contains enzymes that digest egg outer coating and allow penetration)
2) _________________: full of mitochondria to produce ATP for swimming
3) _______________: made of a single
Sketch
OVER
Self Quiz: Can you identify each structure?