Lecture
General anatomy of the Male reproductive system
Genital Glands.—The first appearance of the genital gland is essentially the same in the two sexes, and consists in a thickening of the epithelial layer which lines the peritoneal cavity on the medial side of the urogenital fold. The thick plate of epithelium extends deeply, pushing before it the mesoderm and forming a distinct projection. This is termed the genital ridge, and from it the testis in the male and the ovary in the female are developed. At first the mesonephros and genital ridge are suspended by a common mesentery, but as the embryo grows the genital ridge gradually becomes pinched off from the mesonephros, with which it is at first continuous, though it still remains connected to the remnant of this body by a fold of peritoneum, the mesorchium or mesovarium. About the seventh week the distinction of sex in the genital ridge begins to be perceptible.
The Testis.—The testis is developed in much the same way as the ovary. Like the ovary, in its earliest stages it consists of a central mass of epithelium covered by a surface epithelium. In the central mass a series of cords appear, and the periphery of the mass is converted into the tunica albuginea, thus excluding the surface epithelium from any part in the formation of the tissue of the testis. The cords of the central mass run together toward the future hilus and form a network which ultimately becomes the rete testis. From the cords the seminiferous tubules are developed, and between them connective-tissue septa extend. The seminiferous tubules become connected with outgrowths from the Wolffian body, which, as before mentioned, form the efferent ducts of the testis.
Descent of the Testes.—The testes, at an early period of fetal life, are placed at the back part of the abdominal cavity, behind the peritoneum, and each is attached by a peritoneal fold, the mesorchium, to the mesonephros. From the front of the mesonephros a fold of peritoneum termed the inguinal fold grows forward to meet and fuse with a peritoneal fold, the inguinal crest, which grows backward from the antero-lateral abdominal wall. The testis thus acquires an indirect connection with the anterior abdominal wall; and at the same time a portion of the peritoneal cavity lateral to these fused folds is marked off as the future saccus vaginalis. In the inguinal crest a peculiar structure, the gubernaculum testis, makes its appearance. This is at first a slender band, extending from that part of the skin of the groin which afterward forms the scrotum through the inguinal canal to the body and epididymis of the testis. As development advances, the peritoneum enclosing the gubernaculum forms two folds, one above the testis and the other below it. The one above the testis is the plica vascularis, and contains ultimately the internal spermatic vessels; the one below, the plica gubernatrix, contains the lower part of the gubernaculum, which has now grown into a thick cord; it ends below at the abdominal inguinal ring in a tube of peritoneum, the saccus vaginalis, which protrudes itself down the inguinal canal. By the fifth month the lower part of the gubernaculum has become a thick cord, while the upper part has disappeared. The lower part now consists of a central core of unstriped muscle fiber, and outside this of a firm layer of striped elements, connected, behind the peritoneum, with the abdominal wall. As the scrotum develops, the main portion of the lower end of the gubernaculum is carried, with the skin to which it is attached, to the bottom of this pouch; other bands are carried to the medial side of the thigh and to the perineum. The tube of peritoneum constituting the saccus vaginalis projects itself downward into the inguinal canal, and emerges at the cutaneous inguinal ring, pushing before it a part of the Obliquus internus and the aponeurosis of the Obliquus externus, which form respectively the Cremaster muscle and the intercrural fascia. It forms a gradually elongating pouch, which eventually reaches the bottom of the scrotum, and behind this pouch the testis is drawn by the growth of the body of the fetus, for the gubernaculum does not grow commensurately with the growth of other parts, and therefore the testis, being attached by the gubernaculum to the bottom of the scrotum, is prevented from rising as the body grows, and is drawn first into the inguinal canal and eventually into the scrotum. It seems certain also that the gubernacular cord becomes shortened as development proceeds, and this assists in causing the testis to reach the bottom of the scrotum. By the end of the eighth month the testis has reached the scrotum, preceded by the saccus vaginalis, which communicates by its upper extremity with the peritoneal cavity. Just before birth the upper part of the saccus vaginalis usually becomes closed, and this obliteration extends gradually downward to within a short distance of the testis. The process of peritoneum surrounding the testis is now entirely cut off from the general peritoneal cavity and constitutes the tunica vaginalis.
Descent of the Ovaries.—In
the female there is also a gubernaculum, which
effects a considerable change in the position of the ovary, though not so
extensive a change as in that of the testis. The gubernaculum
in the female lies in contact with the fundus of the
uterus and contracts adhesions to this organ, and thus the ovary is prevented
from descending below this level. The part of the gubernaculum
between the ovary and the uterus becomes ultimately the proper ligament of the
ovary, while the part between the uterus and the labium majus
forms the round ligament of the uterus. A pouch of peritoneum analogous to the saccus vaginalis in the male
accompanies it along the inguinal canal: it is called the
The Metanephros and the Permanent Kidney.—The rudiments of the permanent kidneys make their appearance about the end of the first or the beginning of the second month. Each kidney has a two-fold origin, part arising from the metanephros, and part as a diverticulum from the hind-end of the Wolffian duct, close to where the latter opens into the cloaca. The metanephros arises in the intermediate cell mass, caudal to the mesonephros, which it resembles in structure. The diverticulum from the Wolffian duct grows dorsalward and forward along the posterior abdominal wall, where its blind extremity expands and subsequently divides into several buds, which form the rudiments of the pelvis and calyces of the kidney; by continued growth and subdivision it gives rise to the collecting tubules of the kidney. The proximal portion of the diverticulum becomes the ureter. The secretory tubules are developed from the metanephros, which is moulded over the growing end of the diverticulum from the Wolffian duct. The tubules of the metanephros, unlike those of the pronephros and mesonephros, do not open into the Wolffian duct. One end expands to form a glomerulus, while the rest of the tubule rapidly elongates to form the convoluted and straight tubules, the loops of Henle, and the connecting tubules; these last join and establish communications with the collecting tubules derived from the ultimate ramifications of the diverticulum from the Wolffian duct. The mesoderm around the tubules becomes condensed to form the connective tissue of the kidney. The ureter opens at first into the hind-end of the Wolffian duct; after the sixth week it separates from the Wolffian duct, and opens independently into the part of the cloaca which ultimately becomes the bladder.
The secretory tubules of the kidney become arranged into pyramidal masses or lobules, and the lobulated condition of the kidneys exists for some time after birth, while traces of it may be found even in the adult. The kidney of the ox and many other animals remains lobulated throughout life.
The Urinary Bladder.—The bladder is formed partly from the entodermal cloaca and partly from the ends of the Wolffian ducts; the allantois takes no share in its formation. After the separation of the rectum from the dorsal part of the cloaca (p. 1109), the ventral part becomes subdivided into three portions: (1) an anterior vesico-urethral portion, continuous with the allantois—into this portion the Wolffian ducts open; (2) an intermediate narrow channel, the pelvic portion; and (3) a posterior phallic portion, closed externally by the urogenital membrane. The second and third parts together constitute the urogenital sinus. The vesico-urethral portion absorbs the ends of the Wolffian ducts and the associated ends of the renal diverticula, and these give rise to the trigone of the bladder and part of the prostatic urethra. The remainder of the vesico-urethral portion forms the body of the bladder and part of the prostatic urethra; its apex is prolonged to the umbilicus as a narrow canal, which later is obliterated and becomes the medial umbilical ligament (urachus).
The Prostate.—The prostate originally consists of two separate portions, each of which arises as a series of diverticular buds from the epithelial lining of the urogenital sinus and vesico-urethral part of the cloaca, between the third and fourth months. These buds become tubular, and form the glandular substance of the two lobes, which ultimately meet and fuse behind the urethra and also extend on to its ventral aspect. The isthmus or middle lobe is formed as an extension of the lateral lobes between the common ejaculatory ducts and the bladder. Skene’s ducts in the female urethra are regarded as the homologues of the prostatic glands.
The bulbo-urethral glands of Cowper in the male, and greater vestibular glands of Bartholin in the female, also arise as diverticula from the epithelial lining of the urogenital sinus.
The External Organs of Generation—As already stated, the cloacal membrane, composed of ectoderm and entoderm, originally reaches from the umbilicus to the tail. The mesoderm extends to the midventral line for some distance behind the umbilicus, and forms the lower part of the abdominal wall; it ends below in a prominent swelling, the cloacal tubercle. Behind this tubercle the urogenital part of the cloacal membrane separates the ingrowing sheets of mesoderm.
The first rudiment of the penis (or clitoris) is a structure termed the phallus; it is derived from the phallic portion of the cloaca which has extended on to the end and sides of the under surface of the cloacal tubercle. The terminal part of the phallus representing the future glans becomes solid; the remainder, which is hollow, is converted into a longitudinal groove by the absorption of the urogenital membrane.
In the female a deep groove forms around the phallus and separates it from the rest of the cloacal tubercle, which is now termed the genital tubercle. The sides of the genital tubercle grow backward as the genital swellings, which ultimately form the labia majora; the tubercle itself becomes the mons pubis. The labia minora arise by the continued growth of the lips of the groove on the under surface of the phallus; the remainder of the phallus forms the clitoris.
In the male the early changes are similar, but the pelvic portion of the cloaca undergoes much greater development, pushing before it the phallic portion. The genital swellings extend around between the pelvic portion and the anus, and form a scrotal area; during the changes associated with the descent of the testes this area is drawn out to form the scrotal sacs. The penis is developed from the phallus. As in the female, the urogenital membrane undergoes absorption, forming a channel on the under surface of the phallus; this channel extends only as far forward as the corona glandis.
The corpora cavernosa of the penis (or clitoris) and of the urethra arise from the mesodermal tissue in the phallus; they are at first dense structures, but later vascular spaces appear in them, and they gradually become cavernous.
The prepuce in both sexes is formed by the growth of a solid plate of ectoderm into the superficial part of the phallus; on coronal section this plate presents the shape of a horseshoe. By the breaking down of its more centrally situated cells the plate is split into two lamellæ, and a cutaneous fold, the prepuce, is liberated and forms a hood over the glans. “Adherent prepuce is not an adhesion really, but a hindered central desquamation” (Berry Hart).
The Urethra.—As already described, in both sexes the phallic portion of the cloaca extends on to the under surface of the cloacal tubercle as far forward as the apex. At the apex the walls of the phallic portion come together and fuse, the lumen is obliterated, and a solid plate, the urethral plate, is formed. The remainder of the phallic portion is for a time tubular, and then, by the absorption of the urogenital membrane, it establishes a communication with the exterior; this opening is the primitive urogenital ostium, and it extends forward to the corona glandis.
In the female this condition is largely retained; the portion of the groove on the clitoris broadens out while the body of the clitoris enlarges, and thus the adult urethral opening is situated behind the base of the clitoris.
In the male, by the greater growth of the pelvic portion of the cloaca a longer urethra is formed, and the primitive ostium is carried forward with the phallus, but it still ends at the corona glandis. Later it closes from behind forward. Meanwhile the urethral plate of the glans breaks down centrally to form a median groove continuous with the primitive ostium. This groove also closes from behind forward, so that the external urethral opening is shifted forward to the end of the glans.
The Male Genital Organs (Organa Genitalia Virilia)
The male genitals include the testes, the ductus deferentes, the vesiculæ seminales, the ejaculatory ducts, and the penis, together with the following accessory structures, viz., the prostate and the bulbourethral glands.
1. The Testes and their Coverings—The testes are two glandular organs, which secrete the semen; they are suspended in the scrotum by the spermatic cords. At an early period of fetal life the testes are contained in the abdominal cavity, behind the peritoneum. Before birth they descend to the inguinal canal, along which they pass with the spermatic cord, and, emerging at the subcutaneous inguinal ring, they descend into the scrotum, becoming invested in their course by coverings derived from the serous, muscular, and fibrous layers of the abdominal parietes, as well as by the scrotum.
The coverings of the testes are, the
Skin
Scrotum.
Cremaster.
Dartos tunic
Infundibuliform fascia.
Intercrural fascia.
Tunica vaginalis.
The Scrotum is a cutaneous pouch which contains the testes and parts of the spermatic cords. It is divided on its surface into two lateral portions by a ridge or raphé, which is continued forward to the under surface of the penis, and backward, along the middle line of the perineum to the anus. Of these two lateral portions the left hangs lower than the right, to correspond with the greater length of the left spermatic cord. Its external aspect varies under different circumstances: thus, under the influence of warmth, and in old and debilitated persons, it becomes elongated and flaccid; but, under the influence of cold, and in the young and robust, it is short, corrugated, and closely applied to the testes.
The scrotum consists of two layers, the integument and the dartos tunic.
The Integument is very thin, of a brownish color, and generally thrown into folds or rugæ. It is provided with sebaceous follicles, the secretion of which has a peculiar odor, and is beset with thinly scattered, crisp hairs, the roots of which are seen through the skin.
The Dartos Tunic (tunica dartos) is a thin layer of non-striped muscular fibers, continuous, around the base of the scrotum, with the two layers of the superficial fascia of the groin and the perineum; it sends inward a septum, which divides the scrotal pouch into two cavities for the testes, and extends between the raphé and the under surface of the penis, as far as its root.
The dartos tunic is closely united to the skin externally, but connected with the subjacent parts by delicate areolar tissue, upon which it glides with the greatest facility.
The Intercrural Fascia (intercolumnar or external spermatic fascia) is a thin membrane, prolonged downward around the surface of the cord and testis. It is separated from the dartos tunic by loose areolar tissue.
The Cremaster consists of scattered bundles of muscular fibers connected together into a continuous covering by intermediate areolar tissue.
The Infundibuliform Fascia (tunica vaginalis communis [testis et funiculi spermatici]) is a thin layer, which loosely invests the cord; it is a continuation downward of the transversalis fascia.
Vessels and Nerves.—The arteries supplying the coverings of the testes are: the superficial and deep external pudendal branches of the femoral, the superficial perineal branch of the internal pudendal, and the cremasteric branch from the inferior epigastric. The veins follow the course of the corresponding arteries. The lymphatics end in the inguinal lymph glands. The nerves are the ilioinguinal and lumboinguinal branches of the lumbar plexus, the two superficial perineal branches of the internal pudendal nerve, and the pudendal branch of the posterior femoral cutaneous nerve.
The Spermatic Cord (funiculus spermaticus) extends from the abdominal inguinal ring, where the structures of which it is composed converge, to the back part of the testis. In the abdominal wall the cord passes obliquely along the inguinal canal, lying at first beneath the Obliquus internus, and upon the fascia transversalis; but nearer the pubis, it rests upon the inguinal and lacunar ligaments, having the aponeurosis of the Obliquus externus in front of it, and the inguinal falx behind it. It then escapes at the subcutaneous ring, and descends nearly vertically into the scrotum. The left cord is rather longer than the right, consequently the left testis hangs somewhat lower than its fellow.
Structure of the Spermatic Cord.—The spermatic cord is composed of arteries, veins, lymphatics, nerves, and the excretory duct of the testis. These structures are connected together by areolar tissue, and invested by the layers brought down by the testis in its descent.
The arteries of the cord are: the internal and external spermatics; and the artery to the ductus deferens.
The internal spermatic artery, a branch of the abdominal aorta, escapes from the abdomen at the abdominal inguinal ring, and accompanies the other constituents of the spermatic cord along the inguinal canal and through the subcutaneous inguinal ring into the scrotum. It then descends to the testis, and, becoming tortuous, divides into several branches, two or three of which accompany the ductus deferens and supply the epididymis, anastomosing with the artery of the ductus deferens: the others supply the substance of the testis.
The external spermatic artery is a branch of the inferior epigastric artery. It accompanies the spermatic cord and supplies the coverings of the cord, anastomosing with the internal spermatic artery.
The artery of the ductus deferens, a branch of the superior vesical, is a long, slender vessel, which accompanies the ductus deferens, ramifying upon its coats, and anastomosing with the internal spermatic artery near the testis.
The spermatic veins emerge from the back of the testis, and receive tributaries from the epididymis: they unite and form a convoluted plexus, the plexus pampiniformis, which forms the chief mass of the cord; the vessels composing this plexus are very numerous, and ascend along the cord in front of the ductus deferens; below the subcutaneous inguinal ring they unite to form three or four veins, which pass along the inguinal canal, and, entering the abdomen through the abdominal inguinal ring, coalesce to form two veins. These again unite to form a single vein, which opens on the right side into the inferior vena cava, at an acute angle, and on the left side into the left renal vein, at a right angle.
The nerves are the spermatic plexus from the sympathetic, joined by filaments from the pelvic plexus which accompany the artery of the ductus deferens.
The scrotum forms an admirable covering for the protection of the testes. These bodies, lying suspended and loose in the cavity of the scrotum and surrounded by serous membrane, are capable of great mobility, and can therefore easily slip about within the scrotum and thus avoid injuries from blows or squeezes. The skin of the scrotum is very elastic and capable of great distension, and on account of the looseness and amount of subcutaneous tissue, the scrotum becomes greatly enlarged in cases of edema, to which this part is especially liable as a result of its dependent position.
The
Testes are suspended in the scrotum by the spermatic cords, the left testis
hanging somewhat lower than its fellow. The average dimensions of the testis
are from 4 to
The anterior border and lateral surfaces, as well as both extremities of the organ, are convex, free, smooth, and invested by the visceral layer of the tunica vaginalis. The posterior border, to which the cord is attached, receives only a partial investment from that membrane. Lying upon the lateral edge of this posterior border is a long, narrow, fiattened body, named the epididymis.
The epididymis consists of a central portion or body; an upper enlarged extremity, the head (globus major); and a lower pointed extremity, the tail (globus minor), which is continuous with the ductus deferens, the duct of the testis. The head is intimately connected with the upper end of the testis by means of the efferent ductules of the gland; the tail is connected with the lower end by cellular tissue, and a reflection of the tunica vaginalis. The lateral surface, head and tail of the epididymis are free and covered by the serous membrane; the body is also completely invested by it, excepting along its posterior border; while between the body and the testis is a pouch, named the sinus of the epididymis (digital fossa). The epididymis is connected to the back of the testis by a fold of the serous membrane.
Appendages of the Testis and Epididymis.—On the upper extremity of the testis, just beneath the head of the epididymis, is a minute oval, sessile body, the appendix of the testis (hydatid of Morgagni); it is the remnant of the upper end of the Müllerian duct. On the head of the epididymis is a second small stalked appendage (sometimes duplicated); it is named the appendix of the epididymis (pedunculated hydatid), and is usually regarded as a detached efferent duct.
The testis is invested by three tunics: the tunica vaginalis, tunica albuginea, and tunica vasculosa.
The Tunica Vaginalis (tunica vaginalis propria testis) is the serous covering of the testis. It is a pouch of serous membrane, derived from the saccus vaginalis of the peritoneum, which in the fetus preceded the descent of the testis from the abdomen into the scrotum. After its descent, that portion of the pouch which extends from the abdominal inguinal ring to near the upper part of the gland becomes obliterated; the lower portion remains as a shut sac, which invests the surface of the testis, and is reflected on to the internal surface of the scrotum; hence it may be described as consisting of a visceral and a parietal lamina.
The visceral lamina (lamina visceralis) covers the greater part of the testis and epididymis, connecting the latter to the testis by means of a distinct fold. From the posterior border of the gland it is reflected on to the internal surface of the scrotum.
The parietal lamina (lamina parietalis) is far more extensive than the visceral, extending upward for some distance in front and on the medial side of the cord, and reaching below the testis. The inner surface of the tunica vaginalis is smooth, and covered by a layer of endothelial cells. The interval between the visceral and parietal laminæ constitutes the cavity of the tunica vaginalis.
The obliterated portion of the saccus vaginalis may generally be seen as a fibrocellular thread lying in the loose areolar tissue around the spermatic cord; sometimes this may be traced as a distinct band from the upper end of the inguinal canal, where it is connected with the peritoneum, down to the tunica vaginalis; sometimes it gradually becomes lost on the spermatic cord. Occasionally no trace of it can be detected. In some cases it happens that the pouch of peritoneum does not become obliterated, but the sac of the peritoneum communicates with the tunica vaginalis. This may give rise to one of the varieties of oblique inguinal hernia. In other cases the pouch may contract, but not become entirely obliterated; it then forms a minute canal leading from the peritoneum to the tunica vaginalis.
The Tunica Albuginea is the fibrous covering of the testis. It is a dense membrane, of a bluish-white color, composed of bundles of white fibrous tissue which interlace in every direction. It is covered by the tunica vaginalis, except at the points of attachment of the epididymis to the testis, and along its posterior border, where the spermatic vessels enter the gland. It is applied to the tunica vasculosa over the glandular substance of the testis, and, at its posterior border, is reflected into the interior of the gland, forming an incomplete vertical septum, called the mediastinum testis (corpus Highmori).
The human male reproductive system consists of a number of sex organs that are a part of the human reproductive process. In the case of men, these sex organs are located outside a man's body, around the pelvic region.
The main male sex organs are the penis and the testes which produce semen and sperm, which as part of sexual intercourse fertilize an ovum in a woman's body and the fertilized ovum (zygote) gradually develops into a fetus, which is later born as a child.
The testicle (from Latin testiculus, diminutive of testis, meaning "witness" [of virility],[1] plural testes) is the male generative gland in animals.
The etymology of the word is based on Roman law. The Latin word "testis", witness, was used in the firmly established legal principle "Testis unus, testis nullus" (one witness [equals] no witness), meaning that testimony by any one person in court was to be disregarded unless corroborated by the testimony of at least another. This led to the common practice of producing two witnesses, bribed to testify the same way in cases of lawsuits with ulterior motives. Since such "witnesses" always came in pairs, the meaning was accordingly extended, often in the diminutive (testiculus, testiculi).[citation needed]
Like the ovaries to which they are homologous, testes are components of both the reproductive system (being gonads) and the endocrine system (being endocrine glands). The respective functions of the testes are:
- producing sperm (spermatozoa)
- producing male sex hormones of which testosterone is the best-known
Both functions of the testicle, sperm-forming and endocrine, are under control of gonadotropic hormones produced by the anterior pituitary:
- luteinizing hormone (LH)
- follicle-stimulating hormone (FSH)
[] External appearance
Male mammals have two testes, which are often contained within an extension of the abdomen called the scrotum. In mammals with external testes it is most common for one testicle to hang lower than the other. While the size of the testicle varies, it is estimated that 21.9% of men have their higher testicle being their left, while 27.3% of men have reported to have equally positioned testicles.[2] This is due to differences in the vascular anatomical structure on the right and left sides.
In healthy European adult human males, average testicular
volume is 18 cm³ per testis, with normal size ranging from 12 cm³ to
30 cm³[3].
The average testicle size after puberty measures up to around
- comparing the testicle with ellipsoids of known sizes (orchidometer
).
Duct system
Primary Cell Types
Within the seminiferous tubules
Between tubules (interstitial cells)
· Interstitial macrophages and epithelial cells.
Blood supply and lymphatic drainage
Blood supply and lymphatic drainage of the testes and scrotum are distinct:
- The paired testicular arteries arise directly from the abdominal aorta and descend through the inguinal canal, while the scrotum and the rest of the external genitalia is supplied by the internal pudendal artery (itself a branch of the internal iliac artery).
- The testis has collateral blood supply from 1. the cremasteric artery (a branch of the inferior epigastric artery, which is a branch of the external iliac artery), and 2. the artery to the ductus deferens (a branch of the superior vesical artery, which is a branch of the internal iliac artery). Therefore, if the testicular artery is ligated, e.g., during a Fowler-Stevens orchiopexy for a high undescended testis, the testis will usually survive on these other blood supplies.[6]
- Lymphatic drainage of the testes follows the testicular arteries back to the paraaortic lymph nodes, while lymph from the scrotum drains to the inguinal lymph nodes.
Layers
The blood-testis barrier
Temperature regulation
Cremasteric muscle
Development
There are two phases in which the testes grow substantially; namely in embryonic and pubertal age.
Embryonic
Pubertal
Evolution
External testes
Testicular size
|
Physical injury
Diseases and conditions that affect the testes
Some prominent conditions and differential diagnoses include:
Effects of exogenous hormones
In all cases, the loss in testes volume corresponds with a loss of spermatogenesis.