HUMAN REPRODUCTION
Male
What makes up the reproductive system?
- primary sex organs: testis
- ducts: epididymis, vas deferens, urethra
- accessory glands: e.g. prostate gland
- external genitalia: penis
Scrotum – contains testis
Functions:
- acts as a T° regulator, keeping testis 2-3° lower than the body T°, the
lower T° is necessary for the formation of fertile sperm – in cold
conditions, testes are pulled closer abdomen for warmth/ in warm
weather, testes are suspended far away from the body, in this way the
developing sperm are always kept at a constant T°
- protects/houses testes
Testes
- two oval structs. suspended outside body in the scrotum
- in the embryonic stage, the testes are in the abdominal cavity below
the kidneys and before birth they descend into the scrotum
- testes consist of many compartments/lobules which contain highly
convoluted tubules being the seminiferous tubules – these total +/-
250m in each testis
- germinal epithelium lines tubules
- between tubules are groups of endocrine (secretes testosterone) cells
– the interstitial cells or cells of Leydig
Functions: testis produce:
- sperm (male gametes) by the germinal layer
- testosterone (male hormone) by the interstitial cells
Ducts
- a. epididymis, b. vas deferens (sperm duct) and c. urethra
a. seminiferous tubules join to form epididymis, highly convoluted tubule,
+/- 5m long
Functions:
- immature sperm epididymis where they:
mature to become motile + fertile
, are stored for many months – if longer then they are broken down
by the epithelial cells of epididymis and are reabsorbed into the
body
b. muscular sperm duct = a continuation of the epididymis – it leaves
the scrotum, passes through the prostate gland and then enters the
urethra
Functions:
- secretes sticky fluid containing fructose and globulin which are
nutrients for the sperm cells
- pushes mature sperm forward by strong peristaltic waves from the
epididymis into the urethra – known as ejaculation
peristaltic wave = strong contraction of smooth muscle in the walls of
ducts
c. the duct at the end of the uro-genital system leading to the exterior
Functions:
- forms a common duct for the transportation of semen and urine
although these processes never occur together
Prostate gland
- plum sized gland surrounding the urethra at the base of the bladder
- w/ increased age, this gland may enlarge and exert pressure on the
urethra which slows down the emptying of the bladder – can be
removed surgically
Functions:
- secretes a fluid that aids the transportation of sperm and contains
enzymes that make sperm more active – this fluid makes up +/- one
third of the seminal fluid (semen)
Cowper’s gland
- the two Cowper’s glands are found at the base of the penis
Functions:
- Cowper’s glands produce an alkaline mucous-like fluid when sexually
aroused, this fluid:
neutralises acidic urine that may still be present in the urethra
lubricates the urethra and external urethral opening to protect
sperm from mechanical damage during ejaculation
, Penis
- the urethra passes down the male external organ, the penis
- consists of special spongy tissue (erectile tissue)
- running the length of the penis, there are three sections of erectile
tissue – two are situated on the dorsal side, the corpus cavernosa, and
one on the ventral side, the corpus spongiosum
- primary mechanism that causes erection = the dilation of dorsal and
central arteries supplying blood to the penis
- this allows more blood to fill the three spongy erectile tissue chambers
causing the penis to lengthen and stiffen
- without an erection, sperm can’t be transferred to the female’s vagina
during sexual intercourse
- head of penis = very sensitive and is protected by foreskin –
sometimes removed in simple operation which may be done for
religious/cultural reasons or because it is too tight = circumcision
Functions:
- penis deposits semen w/ sperm into the female’s vagina during
copulation, in this way sperm are brought closer to the egg for
fertilisation, increases chances of fertilisation
What is distinctive about the human penis?
- human male is only mammal w/ no erectile bone (baculum) in the
penis; it relies entirely on engorgement (filling up) w/ blood to reach its
erect state
- human penis isn’t attached to abdominal wall but hangs free, different
to most other mammals where penis is stored internally until erect
Semen
- semen consists of sperm from testis and seminal fluid from sperm duct
and accessory glands
- average volume for semen in ejaculation is 2.5-5ml
- average number of sperm ejaculated is 50-150 million per ml, i.e. 700
million per ejaculation
- semen w/ sperm count of less than 20 million per ml is infertile
Female
What makes up the reproductive organs?
- ovaries
- accessory glands: fallopian tubes (oviduct), uterus, vagina
- external genitalia: vulva
Male
What makes up the reproductive system?
- primary sex organs: testis
- ducts: epididymis, vas deferens, urethra
- accessory glands: e.g. prostate gland
- external genitalia: penis
Scrotum – contains testis
Functions:
- acts as a T° regulator, keeping testis 2-3° lower than the body T°, the
lower T° is necessary for the formation of fertile sperm – in cold
conditions, testes are pulled closer abdomen for warmth/ in warm
weather, testes are suspended far away from the body, in this way the
developing sperm are always kept at a constant T°
- protects/houses testes
Testes
- two oval structs. suspended outside body in the scrotum
- in the embryonic stage, the testes are in the abdominal cavity below
the kidneys and before birth they descend into the scrotum
- testes consist of many compartments/lobules which contain highly
convoluted tubules being the seminiferous tubules – these total +/-
250m in each testis
- germinal epithelium lines tubules
- between tubules are groups of endocrine (secretes testosterone) cells
– the interstitial cells or cells of Leydig
Functions: testis produce:
- sperm (male gametes) by the germinal layer
- testosterone (male hormone) by the interstitial cells
Ducts
- a. epididymis, b. vas deferens (sperm duct) and c. urethra
a. seminiferous tubules join to form epididymis, highly convoluted tubule,
+/- 5m long
Functions:
- immature sperm epididymis where they:
mature to become motile + fertile
, are stored for many months – if longer then they are broken down
by the epithelial cells of epididymis and are reabsorbed into the
body
b. muscular sperm duct = a continuation of the epididymis – it leaves
the scrotum, passes through the prostate gland and then enters the
urethra
Functions:
- secretes sticky fluid containing fructose and globulin which are
nutrients for the sperm cells
- pushes mature sperm forward by strong peristaltic waves from the
epididymis into the urethra – known as ejaculation
peristaltic wave = strong contraction of smooth muscle in the walls of
ducts
c. the duct at the end of the uro-genital system leading to the exterior
Functions:
- forms a common duct for the transportation of semen and urine
although these processes never occur together
Prostate gland
- plum sized gland surrounding the urethra at the base of the bladder
- w/ increased age, this gland may enlarge and exert pressure on the
urethra which slows down the emptying of the bladder – can be
removed surgically
Functions:
- secretes a fluid that aids the transportation of sperm and contains
enzymes that make sperm more active – this fluid makes up +/- one
third of the seminal fluid (semen)
Cowper’s gland
- the two Cowper’s glands are found at the base of the penis
Functions:
- Cowper’s glands produce an alkaline mucous-like fluid when sexually
aroused, this fluid:
neutralises acidic urine that may still be present in the urethra
lubricates the urethra and external urethral opening to protect
sperm from mechanical damage during ejaculation
, Penis
- the urethra passes down the male external organ, the penis
- consists of special spongy tissue (erectile tissue)
- running the length of the penis, there are three sections of erectile
tissue – two are situated on the dorsal side, the corpus cavernosa, and
one on the ventral side, the corpus spongiosum
- primary mechanism that causes erection = the dilation of dorsal and
central arteries supplying blood to the penis
- this allows more blood to fill the three spongy erectile tissue chambers
causing the penis to lengthen and stiffen
- without an erection, sperm can’t be transferred to the female’s vagina
during sexual intercourse
- head of penis = very sensitive and is protected by foreskin –
sometimes removed in simple operation which may be done for
religious/cultural reasons or because it is too tight = circumcision
Functions:
- penis deposits semen w/ sperm into the female’s vagina during
copulation, in this way sperm are brought closer to the egg for
fertilisation, increases chances of fertilisation
What is distinctive about the human penis?
- human male is only mammal w/ no erectile bone (baculum) in the
penis; it relies entirely on engorgement (filling up) w/ blood to reach its
erect state
- human penis isn’t attached to abdominal wall but hangs free, different
to most other mammals where penis is stored internally until erect
Semen
- semen consists of sperm from testis and seminal fluid from sperm duct
and accessory glands
- average volume for semen in ejaculation is 2.5-5ml
- average number of sperm ejaculated is 50-150 million per ml, i.e. 700
million per ejaculation
- semen w/ sperm count of less than 20 million per ml is infertile
Female
What makes up the reproductive organs?
- ovaries
- accessory glands: fallopian tubes (oviduct), uterus, vagina
- external genitalia: vulva
