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ANATOMY OF MALE REPRODUCTIVE ORGANS
@gracienotes
1. The penis is an external organ of the male reproductive system. It has
two main functions:
Sexual intercourse – During erotic stimulation, the penis undergoes erection,
becoming engorged with blood. Following emission, (mixing of the components of
semen in the prostatic urethra) ejaculation can occur, whereby semen moves out of
the urethra through the external urethral orifice. Finally, the penis undergoes
remission, returning to a flaccid state.
Micturition – The penis also has an important urinary role. It contains the urethra,
which carries urine from the bladder to the external urethral orifice, where it is
expelled from the body.
In this article, we will look at the functions and structure of the penis and how
these give rise to certain clinical conditions.
Note: In the anatomical position the penis is erect, so the dorsal side is that closest
to the abdomen and the ventral side is closest to the testes.
Structure of the Penis
The penis can be anatomically divided into three parts:
Root – the most proximal, fixed part of the penis. It is located in the superficial
perineal pouch of the pelvic floor, and is not visible externally. The root contains
three erectile tissues (two crura and bulb of the penis), and two muscles
(ischiocavernosus and bulbospongiosus).
Body – the free part of the penis, located between the root and glans. It is
suspended from the pubic symphysis. It is composed of three cylinders of erectile
tissue – two corpora cavernosa, and the corpus spongiosum.
Glans – the most distal part of the of penis. It is conical in shape, and is formed by
the distal expansion of the corpus spongiosum. This contains the opening of the
urethra, termed the external urethral orifice.
, 2
Fig 1 – The three parts of the penis.
Erectile Tissues
The erectile tissues fill with blood during sexual arousal, producing an erection.
The root and body of the penis are spanned by three masses of erectile tissue.
In the root, these tissues are known as the left and right crura, and the bulb of the
penis. The bulb is situated in the midline of the penile root, and is traversed by the
urethra. The left and right crura are located laterally; attached to the ipsilateral
ischial ramus, and covered by the paired ischiocavernosal muscles.
The erectile tissues continue into the body of the penis. The left and right crura
continue anteriorly into the dorsal part of the penis – they form the two corpora
cavernosa. They are separated by the septum of the penis, although often
incompletely. The bulb forms the corpus spongiosum, which lies ventrally. The
male urethra runs through the corpus spongiosum – to prevent it becoming
occluded during erection the corpus spongiosum fills to a reduced pressure.
Distally, the corpus spongiosum expands to form the glans penis.
, 3
Fig 2 – The erectile tissues of the penis.
Muscles
There are four muscles located in the root of the penis:
Bulbospongiosus (x2) – associated with the bulb of the penis. It contracts to empty
the spongy urethra of any residual semen and urine. The anterior fibres also aid in
maintaining erection by increasing the pressure in the bulb of the penis.
Ischiocavernosus (x2) – surrounds the left and right crura of the penis. It contracts
to force blood from the cavernous spaces in the crura into the corpora cavernosa –
this helps maintain erection.
Fascial Coverings
Each mass of erectile tissue has two fascial coverings. The most superficial layer,
immediately under the skin, is the external fascia of Colles (which is in continuity
with the fascia of Scarpa which covers the abdominal wall).
ANATOMY OF MALE REPRODUCTIVE ORGANS
@gracienotes
1. The penis is an external organ of the male reproductive system. It has
two main functions:
Sexual intercourse – During erotic stimulation, the penis undergoes erection,
becoming engorged with blood. Following emission, (mixing of the components of
semen in the prostatic urethra) ejaculation can occur, whereby semen moves out of
the urethra through the external urethral orifice. Finally, the penis undergoes
remission, returning to a flaccid state.
Micturition – The penis also has an important urinary role. It contains the urethra,
which carries urine from the bladder to the external urethral orifice, where it is
expelled from the body.
In this article, we will look at the functions and structure of the penis and how
these give rise to certain clinical conditions.
Note: In the anatomical position the penis is erect, so the dorsal side is that closest
to the abdomen and the ventral side is closest to the testes.
Structure of the Penis
The penis can be anatomically divided into three parts:
Root – the most proximal, fixed part of the penis. It is located in the superficial
perineal pouch of the pelvic floor, and is not visible externally. The root contains
three erectile tissues (two crura and bulb of the penis), and two muscles
(ischiocavernosus and bulbospongiosus).
Body – the free part of the penis, located between the root and glans. It is
suspended from the pubic symphysis. It is composed of three cylinders of erectile
tissue – two corpora cavernosa, and the corpus spongiosum.
Glans – the most distal part of the of penis. It is conical in shape, and is formed by
the distal expansion of the corpus spongiosum. This contains the opening of the
urethra, termed the external urethral orifice.
, 2
Fig 1 – The three parts of the penis.
Erectile Tissues
The erectile tissues fill with blood during sexual arousal, producing an erection.
The root and body of the penis are spanned by three masses of erectile tissue.
In the root, these tissues are known as the left and right crura, and the bulb of the
penis. The bulb is situated in the midline of the penile root, and is traversed by the
urethra. The left and right crura are located laterally; attached to the ipsilateral
ischial ramus, and covered by the paired ischiocavernosal muscles.
The erectile tissues continue into the body of the penis. The left and right crura
continue anteriorly into the dorsal part of the penis – they form the two corpora
cavernosa. They are separated by the septum of the penis, although often
incompletely. The bulb forms the corpus spongiosum, which lies ventrally. The
male urethra runs through the corpus spongiosum – to prevent it becoming
occluded during erection the corpus spongiosum fills to a reduced pressure.
Distally, the corpus spongiosum expands to form the glans penis.
, 3
Fig 2 – The erectile tissues of the penis.
Muscles
There are four muscles located in the root of the penis:
Bulbospongiosus (x2) – associated with the bulb of the penis. It contracts to empty
the spongy urethra of any residual semen and urine. The anterior fibres also aid in
maintaining erection by increasing the pressure in the bulb of the penis.
Ischiocavernosus (x2) – surrounds the left and right crura of the penis. It contracts
to force blood from the cavernous spaces in the crura into the corpora cavernosa –
this helps maintain erection.
Fascial Coverings
Each mass of erectile tissue has two fascial coverings. The most superficial layer,
immediately under the skin, is the external fascia of Colles (which is in continuity
with the fascia of Scarpa which covers the abdominal wall).
