1. Conceptual Overview: What Forms the Urogenital Diaphragm

• The male urogenital region contains a structural unit called the urogenital diaphragm.
• It is formed by two layers of fascia enclosing two muscles.
• Together, these fasciae + muscles create a supportive and sphincteric platform for the membranous urethra.

Components

• Superior fascia of urogenital diaphragm
• Thin
• Ill-defined
• Inferior fascia of urogenital diaphragm
• Thick
• Called the perineal membrane
• Muscles enclosed
• Sphincter urethrae
• Deep transverse perineal muscles

👉 These four together = urogenital diaphragm.

The urogenital diaphragm is formed by a thin superior fascia, a thick inferior fascia (perineal membrane), and the sphincter urethrae with deep transverse perineal muscles, which together support the membranous urethra.

2. Deep Perineal Space (Deep Perineal Pouch): What Lies Between the Fasciae

• The space between superior and inferior fasciae is the deep perineal space (pouch).

Contents of the Deep Perineal Space

Male specific structures-

• Membranous part of urethra
• Paired bulbourethral (Cowper) glands

neurovascular structures-

• Internal pudendal vessels
• Dorsal nerve of penis (laterally)
• Perineal nerve (laterally)

Muscles-

• Sphincter urethrae muscle
• Deep transverse perineal muscles

The deep perineal space is the space between the superior and inferior fasciae and contains the membranous urethra, internal pudendal vessels, dorsal nerve of penis, perineal nerve, paired bulbourethral glands, sphincter urethrae, and deep transverse perineal muscles.

3. Perineal Membrane: Structure, Attachments, Orientation

• The perineal membrane is:
• Thick
• Unyielding
• Fibrous
• It forms the base on which the penis and penile musculature are fixed.

Attachments

• Laterally:
• To ischiopubic rami
• From just behind the subpubic angle
• Back to the anterior part of the ischial tuberosities
• Anterior border:
• Forms the transverse perineal ligament
• Posterior border:
• Fuses centrally with the perineal body

Orientation

• In the upright position, the perineal membrane lies approximately horizontal.

The perineal membrane is a thick, unyielding fibrous sheet forming the base for the penis and its muscles, attached laterally to the ischiopubic rami from just behind the subpubic angle to the anterior ischial tuberosities, with an anterior transverse perineal ligament, posterior fusion with the perineal body, and it lies approximately horizontal in the standing.

4. Important Gap at the Anterior Border

• There is a small gap:
• Between the transverse perineal ligament
• And the arcuate pubic ligament
• Through this gap passes:
• Deep dorsal vein of the penis
• Which drains into the vesicoprostatic plexus

A small gap between the transverse perineal ligament and the arcuate pubic ligament transmits the deep dorsal vein of the penis, which drains into the vesicoprostatic plexus.

5. Relations of the Perineal Membrane

• Above the membrane:
• Membranous urethra
• Surrounded by urethral sphincter
• Located below the apex of the prostate
• Below the membrane:
• Structures of the superficial perineal region

Structures Piercing the Membrane

• Urethra
• Ducts of bulbourethral glands
• Nerves and vessels

The perineal membrane has the membranous urethra surrounded by the urethral sphincter just below the apex of the prostate above it, the superficial perineal structures below it, and it is pierced by the urethra, ducts of the bulbourethral glands, and accompanying nerves and vessels.

6. Membranous Urethra: Course and Characteristics

• After leaving the prostate:
• The prostatic urethra becomes the membranous urethra
• Course:
• Passes downward for about 1.5 cm
• Pierces the perineal membrane
• At 2.5 cm behind the pubic symphysis
• Continues as the penile urethra
• Characteristics:
• Shortest part of the urethra
• Least dilatable part of the urethra
• Wall composition:
• Upper part contains smooth muscle fibres
• These are continuous with smooth muscle of prostatic urethra

Sentence (simple, single line):

The membranous urethra is the shortest and least dilatable part of the urethra, formed when the prostatic urethra leaves the prostate, runs downward for about 1.5 cm, pierces the perineal membrane 2.5 cm behind the pubic symphysis, continues as the penile urethra, and has an upper wall containing smooth muscle continuous with the prostatic urethra.

7. Sphincter Urethrae (External Urethral Sphincter)

• Clinically called the external urethral sphincter
• Shape:
• Roughly pear-shaped
• Orientation:
• Upper narrow part:
• Extends upward out of the deep perineal pouch
• Surrounds the lower part of the prostatic urethra
• Lower bulbous part:
• Lies below the apex of the prostate
• Lies above the perineal membrane

Fibre Arrangement

• Some fibres:
• Arise from pubic rami
• Form U-shaped loops in front of and behind the urethra
• Some fibres:
• Run from transverse perineal ligament to perineal body
• Some fibres:
• Completely encircle the urethra

Muscle Type

• Striated muscle
• Fibres are:
• Small diameter
• Slow-twitch variety

Nerve Supply

• Perineal branch of pudendal nerve

Sentence (simple, single line):

The sphincter urethrae (external urethral sphincter) is a roughly pear-shaped, striated, slow-twitch muscle whose narrow upper part extends upward from the deep perineal pouch to surround the lower prostatic urethra and whose bulbous lower part lies below the prostatic apex and above the perineal membrane, with fibres arising from the pubic rami forming U-shaped loops, fibres running from the transverse perineal ligament to the perineal body, fibres completely encircling the urethra, and innervation from the perineal branch of the pudendal nerve.

8. Deep Transverse Perineal Muscle

• Location:
• Lies above the posterior part of the perineal membrane
• Attachments:
• From ischial ramus
• To perineal body
• At the perineal body:
• Fibres decussate
• With:
• Contralateral deep transverse perineal muscle
• External anal sphincter
• Relations:
• Merges anteriorly with sphincter urethrae
• Nerve supply:
• Same as sphincter urethrae (perineal branch of pudendal nerve)

The deep transverse perineal muscle lies above the posterior part of the perineal membrane, runs from the ischial ramus to the perineal body where its fibres decussate with the opposite muscle and the external anal sphincter, merges anteriorly with the sphincter urethrae, and is supplied by the perineal branch of the pudendal nerve.

9. Bulbourethral (Cowper’s) Glands

• Number:
• Paired
• Position:
• One on each side of the membranous urethra
• Located in the deep perineal pouch
• Above (deep to) the perineal membrane
• Covered by the urethral sphincter
• Size:
• About 1 cm in diameter
• Ducts:
• One duct from each gland
• About 2.5 cm long
• Pierces the perineal membrane
• Opens into the bulb of the penile urethra
• Function:
• Contribute a small amount to seminal fluid

10. Superficial Perineal Fascia (Colles’ Fascia)

• Lies deep to the skin of the urogenital region
• It is a continuation of:
• Membranous fascia (Scarpa’s fascia) of anterior abdominal wall
• Attachments:
• To ischiopubic rami
• To posterior margin of the perineal membrane

Resulting Space

• These attachments enclose the superficial perineal space (pouch)
• This space is continuous with:
• Space deep to Scarpa’s fascia of the anterior abdominal wall

11. Extensions of Colles’ Fascia

• From its attachments, the fascia projects into:
• A bulbous scrotal expansion
• A cylindrical penile expansion
• The distal end of the penile expansion:
• Attaches around the corona of the glans penis

12. Clinical Correlation: Urethral Rupture

• Rupture of the penile urethra allows urine to extravasate:
• Beneath Colles’ fascia
• Spread of urine:
• Distends scrotum
• Distends penis
• Then passes upwards over anterior abdominal wall
• Beneath Scarpa’s fascia

13. Deep Perineal Fascia

• A deep perineal fascia:
• Intimately surrounds:
• Cavernous bodies of penis and clitoris
• Superficial perineal muscles associated with them

Male Urogenital Region — Complete Integrated Table (Zero-Omission)

One-Line Exam Lock 🔒

The male urogenital diaphragm consists of a thin superior fascia, a thick perineal membrane, the sphincter urethrae, and deep transverse perineal muscles enclosing the deep perineal pouch that supports the membranous urethra.

Penis — Logic-Based Core Note

1. Basic Division

• The penis consists of:
• Root
• Body

2. Root of the Penis: Components and Attachments

• The root of the penis is:
• Attached to the inferior surface of the perineal membrane
• It consists of:
• Central bulb of the penis
• One crus on each side

Crura

• Each crus:
• Is attached to the angle between the perineal membrane and the everted margin of the ischiopubic ramus
• Receives the deep artery of the penis near its anterior end
• Continues forwards to become a corpus cavernosum

Bulb

• The bulb:
• Is the posterior end of the corpus spongiosum
• Lies in the midline

3. Formation of the Body of the Penis

• At the front of the root area, below the subpubic angle:
• The two corpora cavernosa lie side by side
• The corpus spongiosum lies behind them when the penis is dependent
• The corpus spongiosum lies ventral to them when the penis is erect
• Together these form the body of the penis

4. Corpus Spongiosum, Urethra, and Glans

• The penile urethra:
• Runs through the entire length of the corpus spongiosum
• Extends from:
• The bulb posteriorly
• To the expanded distal end, the glans penis
• The glans penis:
• Forms the tip of the penis
• Overlaps the distal ends of the corpora cavernosa

Bulb–Urethra Relationship

• The urethra:
• Enters the bulb from above near its front
• Therefore:
• Most of the bulge of the bulb lies behind and below the urethra
• The bulb:
• Has a slight palpable midline notch on its under surface
• Extends back towards the perineal body
• The arteries of the bulb:
• Enter near the urethra
• The urethra here receives the ducts of the bulbourethral glands

MALE URETHRA — COMPLETE ANATOMY MASTER TABLE

A. Overview

B. Parts of the Male Urethra

C. Prostatic Urethra — High-Yield Internal Anatomy

📌 Exam pearl: Ejaculatory ducts do NOT open into bladder → they open into prostatic urethra.

D. Membranous Urethra — THE DANGER ZONE

📌 Exam pearl: Posterior urethral rupture = membranous urethra.

E. Spongy (Penile) Urethra

📌 Exam pearl: Anterior urethral injuries involve spongy urethra.

URETHRAL INJURY & URINE EXTRAVASATION — MASTER TABLE

A. Anterior Urethral Injury (Spongy urethra)

B. Posterior Urethral Injury (Membranous urethra)

5. Erectile Tissues and Their Sheaths

• The erectile tissues are:
• Two corpora cavernosa
• One corpus spongiosum

Tunica Albuginea

• Each corpus is surrounded by a tough fibrous sheath:
• Called the tunica albuginea of the corpus
• This is not the same as the tunica albuginea of the testis
• The tunica albuginea of the corpus spongiosum:
• Enlarges distally
• Encloses the glans

Trabeculae and Cavernous Spaces

• Fibrous trabeculae extend inward from the tunica
• These divide the corpora into:
• Numerous endothelial-lined cavernous spaces
• Helicine arteries open into these spaces

Septum Between Corpora Cavernosa

• Between the two corpora cavernosa:
• There is a connective tissue septum
• It is partly divided into comb-like strands

6. Deep Fascia and Suspensory Ligament

• The fibrous sheaths of the corpora are encircled by:
• Deep fascia of the penis
• This is an extension of the deep perineal fascia
• This fascia is attached to the front surface of the pubic symphysis by:
• The suspensory ligament of the penis
• A triangular sheet of fibrous tissue

Deep Dorsal Structures

• Lying deep to the deep fascia:
• Deep dorsal vein in the midline
• Dorsal artery on each side
• Dorsal nerve more laterally

7. Skin, Superficial Fascia, and Frenulum

• The skin of the penis:
• Is hairless
• Is prolonged forwards as the prepuce
• The prepuce:
• Partly overlaps the glans
• Doubles back
• Attaches to the neck of the glans

Superficial Fascia

• Beneath the skin lies:
• Superficial fascia of the penis (Buck’s fascia)
• This is a cylindrical prolongation of Colles’ fascia
• In the midline of this layer:
• Lies the superficial dorsal vein
• Accompanied by lymphatics from the skin and anterior part of the urethra

Frenulum

• On the inferior aspect of the glans:
• A fold of skin, the frenulum
• Passes from the prepuce to the ventral end of the urethral orifice

8. Blood Supply

• The penis receives three pairs of arteries
• All are branches of the internal pudendal arteries

Arterial Distribution

• Artery to the bulb:
• Supplies the corpus spongiosum
• Supplies the glans
• Deep artery of the penis:
• Supplies the corpus cavernosum
• Dorsal artery:
• Supplies skin
• Supplies fascia
• Supplies glans

Anastomoses

• There is anastomosis between:
• Artery of the bulb
• Dorsal artery
• This occurs via continuity of:
• Corpus spongiosum
• Glans
• The deep arteries:
• Supply only the corpora cavernosa

Additional Skin Supply

• Penile skin also receives blood from:
• Superficial external pudendal branches
• From the femoral arteries

9. Venous Drainage

• Venous return from the corpora occurs:
• Partly via veins accompanying arteries → internal pudendal veins
• Mostly via the deep dorsal vein

Deep Dorsal Vein

• Pierces the suspensory ligament
• Passes above the perineal membrane
• Enters the vesicoprostatic venous plexus

Superficial Dorsal Vein

• Drains the dorsal skin of the penis
• Divides to join:
• Superficial external pudendal tributaries
• Of the great saphenous veins

10. Lymphatic Drainage

• Skin of penis:
• Drains to superficial inguinal lymph nodes
• Glans and corpora:
• Drain to deep inguinal lymph nodes

11. Nerve Supply

Cutaneous Innervation

• Supplied mainly by pudendal nerves
• Via:
• Posterior scrotal nerves
• Dorsal nerve of the penis
• The glans is supplied by the dorsal nerve
• Main dermatome involved:
• S2
• A small area on the dorsum of proximal penis:
• Supplied by ilioinguinal nerve (L1)

Motor Supply

• Bulbocavernosus muscle
• Ischiocavernosus muscle
• These:
• Contract spasmodically during ejaculation
• Are supplied by the perineal nerve
• From the pudendal nerve (S2, S3)

Autonomic Supply

• Sympathetic nerves:
• Necessary for initial stages of ejaculation
• Derived from L1 spinal segment
• Via superior and inferior hypogastric plexuses
• Parasympathetic nerves (Erection):
• From pelvic splanchnic nerves (S2, S3)
• Supply cavernous tissue of all three corpora
• Allow increased blood flow for erection

12. Circumcision

• Circumcision:
• Probably the oldest operation in the world
• Performed for religious or racial reasons
• Medical indication:
• Phimosis (tightly constricting prepuce)

Procedure

• The prepuce is:
• Incised on the dorsum
• From the tip towards the base of the glans
• Adhesions are dissected
• The incision is carried circumferentially
• Skin edges are sutured
• Bleeding from a vessel in the frenulum:
• Must be controlled

PENIS — COMPLETE LOGIC-BASED MASTER TABLE (ZERO-OMISSION)

🔑 Exam-Reflex One-Liners

• Bulb = spongiosum, crura = cavernosa
• Deep artery = erection, bulb artery = spongiosum + glans
• Deep dorsal vein → vesicoprostatic plexus
• Parasympathetic (S2–S3) = erection, Sympathetic (L1) = ejaculation

Superficial Perineal Muscles — Logic-Based Core Note (Zero Omission)

1. Overall Pattern and Arrangement

• The bulb and each crus of the penis are covered by superficial perineal muscles.
• These muscles are:
• Bulbospongiosus (over the bulb)
• Ischiocavernosus (over each crus)
• In addition:
• There is a paired superficial transverse perineal muscle
• This lies along the posterior border of the perineal membrane
• When viewed in the lithotomy position:
• The three superficial perineal muscles on each side
• Form a triangular pattern

2. Bulbospongiosus Muscle

Origin

• Arises from:
• The perineal body
• And anterior to that from a median raphe
• The median raphe:
• Joins the right and left bulbospongiosus muscles together

Insertion and Fibre Direction

• Posterior fibres:
• Directed forwards and laterally
• Pass over the bulb
• Insert into:
• The perineal membrane
• A dorsal fibrous expansion on the penis
• Fibre relationships:
• The more posterior fibres:
• Clasp the corpus spongiosum
• The more anterior fibres:
• Extend onto the corpora cavernosa

Actions

• Empties the urethra at the end of micturition
• Assists in erection:
• By compressing the deep dorsal vein of the penis
• Contracts during ejaculation

3. Ischiocavernosus Muscle

Origin

• Arises from:
• The posterior part of the perineal membrane
• The ischial ramus

Insertion

• Inserted by an aponeurosis
• Onto the surface of the corpus cavernosum

Function

• Assists in:
• Supporting the erect penis
• Slight movement of the erect penis

4. Superficial Transverse Perineal Muscle

Origin

• Arises from the ischial tuberosity

Insertion

• Inserted into the perineal body

Function

• Helps to stabilize the perineal body

5. Nerve Supply

• All three superficial perineal muscles are supplied by:
• The perineal branch of the pudendal nerve
• Spinal segments:
• S2, S3

Superficial Perineal Muscles — Complete Comparative Table

Ultra-high-yield exam pattern (1-liner)

Superficial perineal muscles = bulbospongiosus + ischiocavernosus + superficial transverse perineal, all supplied by perineal branch of pudendal nerve (S2–S3), forming triangular arrangement in lithotomy position.

Male Urethra — Logic-Based Core Note

1. Overall Structure and Length

• The male urethra consists of three parts:
• Prostatic
• Membranous
• Spongy (penile)
• Total length:
• About 20 cm
• The prostatic and membranous parts:
• Have been described previously

2. Spongy (Penile) Urethra: Length and Subdivisions

• The spongy (penile) urethra:
• Is about 15 cm long
• Lies within the corpus spongiosum of the penis
• It is divided into:
• Bulbous part
• Pendulous part

3. Bulbous Part and Course at the Root

• The posterior part of the corpus spongiosum:
• Is attached to the undersurface of the perineal membrane
• Is enlarged to form the bulb
• After piercing the perineal membrane:
• The urethra enters the bulb
• Immediately takes a right-angled (90°) curve forwards within the bulb
• The urethra then:
• Continues through the corpus spongiosum
• Passes beyond the root of the penis
• Enters the body of the penis

4. Distal Part and Navicular Fossa

• Just proximal to the external urethral meatus at the tip of the glans:
• There is a short, dilated region called the navicular fossa
• Epithelial lining:
• Navicular fossa:
• Stratified squamous epithelium
• Rest of the urethra:
• Transitional epithelium
• Typical of the urinary tract

5. Mucosa, Glands, and Urinary Stream

• The urethral mucosa contains:
• Very small blind-ending pockets (lacunae)
• Numerous mucous urethral glands (glands of Littre)
• Shape and stream:
• Empty urethra:
• Horizontal in cross-section
• External meatus:
• Vertical slit
• Result:
• Spiral stream of urine

6. Calibre and Dilatations

• The narrowest part of the urethra:
• External urethral meatus
• Dilatations occur in:
• Prostatic part
• Bulb
• Navicular fossa

7. Clinical Anatomy: Catheterization

• When passing a catheter:
• The 90° change of direction in the bulbar part
• Before entering the membranous urethra
• Must be kept in mind
• Due to a particularly large lacuna:
• Located on the roof of the navicular fossa
• Instruments passed through the external meatus:
• Should be initially pointed towards the floor of the fossa

8. Blood Supply

• There is no single artery to the urethra
• Blood supply comes from:
• Adjacent vessels
• These supply the urethra as it passes through:
• Prostate
• Sphincter urethrae
• Corpus spongiosum

9. Nerve Supply

• Mucous membrane of the penile urethra:
• Supplied by a branch from the perineal nerve
• More proximal parts:
• Receive filaments from the inferior hypogastric plexuses

10. Development of the Male Urethra

Proximal Part(intermediate mesoderm)

• The part of the urethra proximal to the openings of:
• Ejaculatory ducts
• Prostatic utricle
• Develops from:
• Lower ends of the mesonephric ducts
• Ureters
• These are:
• Absorbed into the bladder wall
• This development is similar to:
• The trigone of the bladder

Remaining Parts

• The rest of the urethra develops from:
• Pelvic part of the urogenital sinus
• Phallic part of the urogenital sinus
• Genital tubercle
• In the penile part:
• Development is supplemented ventrally
• By fusion of the urogenital folds

11. Development of the Navicular Fossa and Hypospadias

• The epithelium of the navicular fossa:
• Is ectodermal
• Derived from the genital tubercle
• It begins as:
• A solid epithelial column
• Which later becomes canalized
• If canalization fails:
• And there is failure of complete fusion of the urogenital folds
• Result:
• Hypospadias
• A midline opening on the ventral surface of the penis

Male Urethra — Complete Logic-Based Master Table (Zero Omission)

Spongy (Penile) Urethra — Anatomy

Bulbous Part & Course

Distal Part & Navicular Fossa

Mucosa, Glands & Urinary Stream

Calibre & Dilatations

Clinical Anatomy — Catheterization

Blood Supply

Nerve Supply

Development of the Male Urethra

Proximal Part (Intermediate Mesoderm)

Remaining Parts

Navicular Fossa & Hypospadias

Scrotum — Logic-Based Core Note

1. Definition and Contents

• The scrotum is a pouch of skin.
• It contains:
• The testes
• The spermatic cords

2. Skin and Subcutaneous Tissue

• The subcutaneous tissue of the scrotum:
• Contains no fat
• Contains the dartos muscle
• The dartos muscle:
• Sends a sheet into the midline fibrous septum of the scrotum
• The rugosity (wrinkling) of the scrotal skin:
• Is due to contraction of the dartos muscle

Nature and Innervation of Dartos

• Dartos is:
• Smooth muscle
• Nerve supply:
• Sympathetic fibres
• Probably carried by the genital branch of the genitofemoral nerve

3. Blood Supply

• The skin of the scrotum receives blood from:
• Superficial external pudendal arteries (from the femoral artery)
• Deep external pudendal arteries (from the femoral artery)
• Scrotal branches of the perineal artery (from the internal pudendal artery)

Venous Drainage

• Venous drainage is mainly by:
• Superficial external pudendal veins
• Deep external pudendal veins
• These drain into:
• The great saphenous vein

4. Lymphatic Drainage

• Lymph from the scrotum drains to:
• Superficial inguinal lymph nodes

5. Nerve Supply

• The anterior axial line crosses the scrotum.
• Sensory supply is divided regionally:

Anterior One-Third of Scrotal Skin

• Supplied by:
• Ilioinguinal nerve (L1)
• Genital branch of the genitofemoral nerve (L1)

Posterior Two-Thirds of Scrotal Skin

• Supplied by:
• Scrotal branches of the perineal nerve (S3)
• Reinforced laterally by:
• Perineal branch of the posterior femoral cutaneous nerve (S2)

6. Development

• The scrotum develops from:
• Labioscrotal swellings
• Urogenital folds
• The site where the urogenital folds meet:
• Is marked by a midline cutaneous raphe
• This raphe:
• Is visible on the scrotum
• Continues onto the inferior surface of the penis

Female Comparison

• In the female:
• Labioscrotal folds → labia majora
• Urogenital folds remain separate → labia minora

SCROTUM — COMPLETE MASTER TABLE (ZERO OMISSION)

Perineal Vessels and Nerves — Logic-Based Core Note

1. Internal Pudendal Artery: Entry and Course

• The internal pudendal artery:
• Enters the deep perineal pouch
• From the anterior end of the pudendal canal
• It passes forwards:
• Along the ischiopubic ramus
• Above the perineal membrane
• Relations (from above downwards):
• Dorsal nerve of penis lies above
• Internal pudendal artery in the middle
• Perineal nerve lies below

2. Branches of the Internal Pudendal Artery

Perineal Branch

• Pierces the posterior angle of the perineal membrane
• Gives rise to:
• Posterior scrotal branches
• Transverse perineal branches

Artery to the Bulb

• Arises further forward
• Pierces the perineal membrane alongside the urethra
• Enters the corpus spongiosum
• Supplies:
• Cavernous tissue of the corpus spongiosum
• Continues forwards to supply the glans penis

3. Terminal Branches of Internal Pudendal Artery

• Near the anterior margin of the perineal membrane:
• The artery divides into:
• Deep artery of the penis
• Dorsal artery of the penis

Deep Artery of the Penis

• Pierces the perineal membrane
• Enters the crus of the penis
• Supplies:
• Erectile cavernous tissue of the corpus cavernosum
• Supply occurs via:
• Helicine branches

Dorsal Artery of the Penis

• Pierces the perineal membrane
• Passes:
• Between the crus of the penis and the pubic symphysis
• Pierces the suspensory ligament
• Runs forwards:
• Alongside the median deep dorsal vein
• With dorsal nerves laterally
• Between:
• Deep fascia of the penis
• Fibrous sheaths of the corpora cavernosa
• Terminates in the glans
• Anastomoses with:
• Terminal branches of the artery to the bulb

4. Deep Dorsal Vein of the Penis

• Drains most of the blood from the corpora
• Course:
• Runs proximally in the midline
• Pierces the suspensory ligament
• Passes upwards through the gap between:
• Pubic symphysis (arcuate pubic ligament)
• Perineal membrane
• Enters the pelvis and drains into:
• Vesicoprostatic venous plexus

5. Pudendal Nerve: Division and Relations

• The pudendal nerve:
• Divides within the pudendal canal
• Into two terminal branches:
• Dorsal nerve of the penis
• Perineal nerve
• Both branches:
• Enter the deep perineal pouch
• Run forwards:
• Dorsal nerve above the internal pudendal artery
• Perineal nerve below the artery

6. Dorsal Nerve of the Penis

• Appears to be the direct continuation of the pudendal nerve
• Course:
• Pierces the anterior angle of the perineal membrane
• Accompanies the dorsal artery on its lateral side
• Supplies:
• Skin of the penis
• Glans penis
• Gives branches to the corpus cavernosum
• Important negative fact:
• Has no branches in the deep perineal pouch

7. Perineal Nerve

• Is the larger terminal branch of the pudendal nerve
• Gives muscular branches to:
• Superficial perineal muscles
• Deep perineal muscles
• Sphincter urethrae
• The branch to bulbospongiosus:
• Supplies sensory fibres to the mucous membrane of the urethra
• Posterior scrotal branches:
• Arise either before or just after entering the deep perineal pouch
• Run forwards superficial to the perineal membrane
• Supply scrotal skin

8. Neural Control of Erection and Ejaculation: Fundamental Difference

• Erection:
• Parasympathetic
• Ejaculation:
• Sympathetic + somatic

9. Erection: Mechanism

• Parasympathetic impulses travel via:
• Genital branches of the pelvic splanchnic nerves
• These impulses cause:
• Vasodilatation of helicine arteries
• Within the erectile tissue of the corpora cavernosa
• Hence the historical name:
• Nervi erigentes
• As erectile tissue becomes engorged:
• Some compression of draining veins may occur
• Primary mechanism of erection:
• Increased arterial inflow
• Due to relaxation of smooth muscle in trabeculae of corpora
• This process depends on:
• Nitric oxide
• Cyclic GMP
• Erection may be:
• Reflex (physical stimulation)
• Psychogenic

10. Ejaculation: Emission Phase

• Sympathetic outflow:
• From spinal segments T11 to L2
• Targets smooth muscle in:
• Epididymis
• Vas deferens
• Seminal vesicle
• Ejaculatory duct
• Prostate
• Superficial trigonal muscle of bladder
• Circular muscle of bladder neck
• Effect:
• Contraction of smooth muscle
• Causes flow of seminal fluid into the prostatic urethra
• This phase is called emission
• Bladder neck:
• Internal urethral opening becomes constricted
• Prevents retrograde flow into the bladder

11. Ejaculation: Expulsion Phase

• Rhythmic contraction of bulbospongiosus
• Supplied by:
• Perineal nerve
• Effect:
• Compresses the penile urethra
• Expels the seminal fluid

12. Orgasmic Sensations and Spinal Cord Lesions

• Orgasmic sensations:
• Travel in the spinothalamic tract
• These sensations:
• Are abolished by cord transection
• However:
• In transections above the lower thoracic segments
• Ejaculation can still occur

Perineal Vessels, Nerves & Sexual Function — COMPLETE MASTER TABLE (Zero Omission)

A. Internal Pudendal Artery — Course & Relations

B. Branches of Internal Pudendal Artery

C. Terminal Branches of Internal Pudendal Artery

D. Venous Drainage

E. Pudendal Nerve — Division & Relations

F. Dorsal Nerve of the Penis

G. Perineal Nerve

H. Neural Control — Erection vs Ejaculation

I. Erection — Mechanism

J. Ejaculation — Emission Phase

K. Ejaculation — Expulsion Phase

L. Orgasmic Sensation & Spinal Cord Lesions