Male External Genital Organs - PowerPoint Presentation

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Male External Genital Organs

EXTERNAL GENITAL ORGANS

1. Penis,

2. Scrotum,

3. Testes,

4.

Epididymes

, and

Spermatic

cords.

The penis is the male organ of copulation. It is made up of: (a) A root or attached portion, and (b) a body or free portion.

Root of Penis

• Root of the penis is situated in the superficial

perineal

pouch.

• It is composed of three masses of erectile tissue, namely the two

crura

and one bulb.

• Each

crus

(Latin leg) is firmly attached to the margins of the pubic arch, and is covered by the

ischiocavernosus

.

• The bulb is attached to the

perineal

membrane in between the two

crura

. It is covered by the

bulbospongiosus

.

Body of Penis

It is composed of three elongated masses of erectile tissue.

These masses are the right and left corpora

cavernosa

, and a median corpus

spongiosum

.

The penis has a ventral surface that faces backwards and downwards, and a dorsal surface that faces forwards and upwards.

The

corpus

spongiosum

is the forward continuation of the bulb of the penis. Its terminal part is expanded to form a conical enlargement, called the

glans

penis.

The supports of the body of penis are the following.

a. The

fundiform

ligament It lies superficial to the

suspensory

ligament

b. The

suspensory

ligament extends from the pubic

symphysis

and blends below with the fascia on each side of the penis

Arteries of the Penis

• The

deep artery of the penis

• The

dorsal artery of the penis

• The

artery of the bulb of the penis

• Veins of the penis

• The dorsal veins, superficial and deep, are unpaired.

Nerve Supply of the Penis

The sensory nerve supply to the penis is derived from the dorsal nerve of the penis and the

ilioinguinal

nerve.

2. The autonomic nerves are derived from the pelvic plexus via the

prostatic plexus. The sympathetic nerves are vasoconstrictor, and the parasympathetic nerves (S2–S4) are vasodilator.

(a) Male genital organs; parts of the penis—(b) ventral view, and (c) sagittal section

Transverse section through the body of the penis

Lymphatic Drainage

Lymphatics from the glans drain into the deep inguinal nodes, also called gland of Cloquet. Lymphatics from the rest of the penis drain into the superficial inguinal lymph nodes.

Mechanism of Erection of the Penis

Dilatation of the

helicine arteries

This enlargement presses the veins

Expansion of the corpora cavernosa,

Erection is controlled by parasympathetic nerves (nervi erigentes, S2–S4).

SCROTUM

The scrotum (Latin

bag) is a

cutaneous

bag containing the right and left testes, the

epididymis

and the lower parts of the spermatic cords.Layers of the Scrotum1. Skin2. Dartos muscle

3. The external spermatic fascia from external oblique muscle.

4. The

cremasteric

muscle and fascia from internal oblique muscle.

5. The internal spermatic fascia from fascia

transversalis

Nerve Supply

The anterior one-third of the scrotum is supplied by segment L1

The posterior two-thirds of the scrotum are supplied by

segment S3

Testis

The testis is the male gonad.

External Features

1. Two poles or ends

2. Two borders, anterior and posterior

3. Two surfaces, medial and lateral.

(a) Testis epididymis, sinus of the epididymis, and (b) longitudinal section of testis and epididymis

Coverings of the Testis

• The

tunica vaginalis

• The

tunica albuginea

• The

tunica vasculosa

Structure of the Testis

The glandular part of the testis consists of 200 to 300 lobules. Each lobule contains two to three seminiferous tubules.

The

seminiferous tubules

join together at the apices of the lobules to form 20 to 30 straight tubules which enter the mediastinum. Here they form a network of tubules, the rete testis. In its turn, the rete testis gives rise to 12 to 30 efferent ductules which emerge near the upper pole of the testis and enter the epididymis.

Arterial Supply

The

testicular artery from abdominal aorta: It descends on the posterior abdominal wall to reach the deep inguinal ring where it enters the spermatic cord.

Venous Drainage

The veins emerging from the testis form the

pampiniform plexus (pampiniform = like a vine). Right vein drains into inferior vena cava. Left vein drains into left renal vein.

Lymphatic Drainage

The lymphatics from the testis ascend along the testicular vessels and drain into the

preaortic and para-aortic groups of lymph nodes.

Nerve Supply

The testis is supplied by sympathetic nerves arising from segment T10 of the spinal cord.

Epididymis

The epididymis is an organ made up of highly coiled tube that act as reservoir of spermatozoa.

Parts

•

efferent ductules

•

head

•

body

•

the duct of the epididymis which continuous as

•

ductus deferens

Development of Testis

It is comprised of spermatogenic cells, cells of Sertoli and Leydig’s cells.

Spermatogenic series of cells are derived from endoderm of dorsocaudal part of yolk sac, i.e. endoderm.

Cells of Sertoli are derived from epithelial cells, i.e. coelomic epithelium.

Leydig’s cells: Mesodermal in origin.

Descent of the Testis

• The testes develop in relation to segments T10 to T12.

Subsequently, they descend to reach the scrotum during the second month of intrauterine life.

It reaches the iliac

fossa

by the 3rd month,

• Rests at the deep inguinal ring • Traverses the inguinal canal • Reaches the superficial inguinal ring

• And the bottom of the scrotum by the 9th month.

Stages of descent of testis include formation of processus vaginalis

Ducts

The predominant duct in males is the medially placed

mesonephric

or

Wolffian

duct.

Its functional derivatives are:• Trigone of urinary bladder•  Epididymis

• 

Ductus

deferens

•  Seminal vesicles

•  Ejaculatory duct

2.

Paramesonephric

duct forms

vestigeal

component, the appendix of testis.

3.

Mesonephric

tubules form functional

rete

testis and

vestigeal

paradidymis

and superior and inferior aberrant

ductules

.

FACTS TO REMEMBER

• The cavernous tissue is finer in corpus spongiosum as it contains urethra.

• Penis is supplied by deep, dorsal arteries of penis artery to the bulb and superficial external pudendal artery.

• Tunica vaginalis is the lower persistent part of processus vaginalis, an extension of peritoneal cavity.

• Right testicular vein drains into inferior vena cava. Left testicular vein drains into left renal vein.

• Lymph node of Cloquet is involved in cancer of the penis. Varicocoele is common on left side.

• Hydrocoele is the commonest cause of swelling of the scrotum.