Anatomy Sok Sanith (Penis)

Human penis

The human penis is an external male intromittent organ that additionally serves as the urinal duct. The main parts are the root (radix); the body (corpus); and the epithelium of the penis including the shaft skin and the foreskin (prepuce) covering the glans penis. The body of the penis is made up of three columns of tissue: two corpora cavernosa on the dorsal side and corpus spongiosum between them on the ventral side. The human male urethra passes through the prostate gland, where it is joined by the ejaculatory duct, and then through the penis. The urethra traverses the corpus spongiosum, and its opening, the meatus , lies on the tip of the glans penis. It is a passage both for urination and ejaculation of semen.

Most of the penis develops from the same tissue in the embryo as does the clitoris in females; the skin around the penis and the urethra come from the same embryonic tissue from which develops the labia minora in females. An erection is the stiffening and rising of the penis, which occurs during sexual arousal, though it can also happen in non-sexual situations. Spontaneous non-sexual erections frequently occur during adolescence and during sleep.

The tip, or glans of the penis is darker in color, and covered by the foreskin, if present. In its fully erect state, the shaft of the penis is rigid, with the skin tightly stretched. \n The glans of the erect penis has the feel of a raw mushroom. The erect penis may be straight or curved and may point at an upward or downward angle, or straight ahead. It may also have a tendency to the left or right.

Measurements vary, with studies that rely on self- measurement reporting a significantly higher average than those with a health professional measuring. As of 2015, a systematic review of 15,521 men, and the best research to date on the topic, as the subjects were measured by health professionals, rather than self-measured, has concluded that the average length of an erect human penis is 13.12 cm (5.17 inches) long, while the average circumference of an erect human penis is 11.66 cm (4.59 inches). Neither age nor size of the flaccid penis accurately predicts erectile length. \n The most common form of genital alteration is circumcision, removal of part or all of the foreskin for various cultural, religious and, more rarely, medical reasons. There is controversy surrounding circumcision.

The male reproductive system is a fascinating arrangement of external and internal genital organs that are intimately connected to the male urinary tract through the penis externally and the urethra internally. The penis is the largest part of the external male genitalia and is made up of three main parts:

  • the root
  • the body
  • the glans penis

Parts \n Root \n The root of the penis consists of: \n • the median urethral bulb \n • the crura, one on either side \n Each crus is covered by the Ischiocavernosus, while the bulb is surrounded by the bulbocavernosus. The root of the penis lies in the perineum, between the inferior fascia of the urogenital diaphragm and the fascia of Colles. In addition to being attached to the fasciæ and the pubic rami, it is bound to the front of the symphysis pubis by the fundiform and suspensory ligaments.

Body

The body of the penis stems from the superficial perineal space where it is attached to the perineal membrane. It is made up of three masses of erectile tissue, which include the paired corpora cavernosa and the corpus spongiosum.

These three sections of the shaft of the penis are cylindrical in shape and are individually covered by the fibrous tunica albuginea internally and Buck’s fascia externally. The latter is continuous above with the fascia of Scarpa, and below with the dartos tunic of the scrotum and the fascia of Colles. The skin of the penis connects to this fascia through the loose areolar connective tissue.

The corpora cavernosa curve laterally to form the crura of the penis, to which the ischiopubic ramus is attached to, just in front of the ischial tuberosity. The two muscles which associate with the erectile bodies are the bulbospongiosus muscles and the ischiocavernosus muscle.

The bulbospongiosus muscle attaches proximally to the perineal body and also to the proximal surface of the bulb of the penis. \n Its distal attachment is to the corpus spongiosus and it helps to compress the bulb of the penis, force blood into an erect penis and compress the outflow veins.

The ischiocavernosus muscle originates from the inferior internal surface of the ischiopubic ramus and the ischial tuberosity and inserts onto the crus of the penis. It aids erection by increasing blood flow and preventing outflow.

Glans Penis \n The glans penis is the most distal portion of the corpus spongiosum and expands laterally at the distal aspect of the body of the penis, before narrowing at the very tip. It forms a bulbous shape and part of the bulb of the penis.

It is covered by a double layer of skin and connective tissue, which extends from the neck of the glans to just beyond the tip of the penis and is known as the foreskin or prepuce.

Structure

The human penis is made up of three columns of tissue: two corpora cavernosa lie next to each other on the dorsal side and one corpus spongiosum lies between them on the ventral side. corpus cavernosum

The enlarged and bulbous-shaped end of the corpus spongiosum forms the glans penis with two specific types of sinusoids, which supports the foreskin, or prepuce, a loose fold of skin that in adults can retract to expose the glans.

The area on the underside of the penis, where the foreskin is attached, is called the frenum, or frenulum. The rounded base of the glans is called the corona. The perineal raphe is the noticeable line along the underside of the penis.

The urethra, which is the last part of the urinary tract, traverses the corpus spongiosum, and its opening, known as the meatus, lies on the tip of the glans penis. It is a passage both for urine and for the ejaculation of semen. Sperm are produced in the testes and stored in the attached epididymis. During ejaculation, sperm are propelled up the vas deferens, two ducts that pass over and behind the bladder.

Fluids are added by the seminal vesicles and the vas deferens turns into the ejaculatory ducts, which join the urethra inside the prostate gland. The prostate as well as the bulbourethral glands add further secretions, and the semen is expelled through the penis.

The raphe is the visible ridge between the lateral halves of the penis, found on the ventral or underside of the penis, running from the meatus (opening of the urethra) across the scrotum to the perineum (area between scrotum and anus).

The human penis differs from those of most other mammals, as it has no baculum (or erectile bone) and instead relies entirely on engorgement with blood to reach its erect state. It cannot be withdrawn into the groin, and it is larger than average in the animal kingdom in proportion to body mass.

The human penis is reciprocating from a cotton soft to a bony rigidity resulting from penile arterial flow varied between 2-3 to 60-80 mL/Min implies the most ideal milieu to apply Pascal's law in the entire human body; the overall structure is unique.

Size \n Measurements vary, with studies that rely on self- measurement reporting a significantly higher average than those with a health professional measuring. As of 2015, a systematic review of 15,521 men, and the best research to date on the topic, as the subjects were measured by health professionals, rather than self- measured, has concluded that the average length of an erect human penis is 13.12 cm (5.17 inches) long, while the average circumference of an erect human penis is 11.66 cm (4.59 inches).

Among all primates, the human penis is the largest in girth, but comparable to chimpanzees and certain other species in length. \n Penis size difference may be caused by genetics but also by environmental factors such as fertility medications, culture, diet, and chemical/pollution exposure.

The longest officially documented human penis was found by physician Robert Latou Dickinson. It was 34.3 cm \n (13.5 in) long and 15.9 cm (6.26 in) around.

Normal variations

 Pearly penile papules are raised bumps of somewhat paler color around the base (sulcus) of the glans which typically develop in men aged 20 to 40. As of 1999, different studies had produced estimates of incidence ranging from 8 to 48 percent of all men. They may be mistaken for warts, but are not harmful or infectious and do not require treatment.

  •   Fordyce's spots are small, raised, yellowish-white spots 1–2 mm in diameter that may appear on the penis, which again are common and not infectious.
  •   Sebaceous prominences are raised bumps similar to Fordyce's spots on the shaft of the penis, located at the sebaceous glands and are normal.

Fordyce spots on the penis

Fordyce spots on Lip

 Phimosis is an inability to retract the foreskin fully. It is normal and harmless in infancy and pre- pubescence, occurring in about 8% of boys at age 10. According to the British Medical Association, treatment (topical steroid cream and/or manual stretching) does not need to be considered until age 19.

 Curvature: few penises are completely straight, with curves commonly seen in all directions (up, down, left, right). Sometimes the curve is very prominent but it rarely inhibits sexual intercourse. Curvature as great as 30° is considered normal and medical treatment is rarely considered unless the angle exceeds 45°. Changes to the curvature of a penis may be caused by Peyronie's disease.

Development

Differences between female and male organs

In the developing fetus, the genital tubercle develops into the glans of the penis in males and into the clitoral glans in females; they are homologous. The urogenital fold develops into the skin around the shaft of the penis and the urethra in males and into the labia minora in females.

The corpora cavernosa are homologous to the body of the clitoris; the corpus spongiosum is homologous to the vestibular bulbs beneath the labia minora; the scrotum, homologous to the labia majora; and the foreskin, homologous to the clitoral hood. The raphe does not exist in females, because there, the two halves are not connected.

Growth in puberty

On entering puberty, the penis, scrotum and testicles will enlarge toward maturity. During the process, pubic hair grows above and around the penis. A large-scale study assessing penis size in thousands of 17- to 19-year-old males found no difference in average penis size between 17-year- olds and 19-year-olds. From this, it can be concluded that penile growth is typically complete not later than age 17, and possibly earlier.

Blood Supply and Venous Drainage \n The arterial supply of the penis includes the dorsal arteries of the penis, which are a continuation of the internal pudendal arteries, as are the deep arteries of the penis and the artery of the bulb of the penis. The external pudendal artery supplies the skin of the penis.

The venous drainage of the penis is controlled by the deep dorsal vein of the penis, which drains to the prostatic venous plexus and then on to the internal iliac or internal pudendal veins. Also, the superficial dorsal vein of the penis drains into the superficial external pudendal vein, a tributary of the great saphenous vein.

Lymphatic Drainage

The various parts of the penis may present lymph drainage pathways, depending on the region in question. \n Firstly, the skin of the penis always drains into the superficial inguinal lymph nodes.

Lymph drained from both the glans and cavernous bodies of the penis also primarily drains into the medial members of the horizontal tract of the superficial inguinal lymph nodes. However these structures are also described as having some efferent lymph vessels which terminate at the deep inguinal lymph nodes.

Both the superficial and deep inguinal lymph nodes eventually drain into the external iliac lymph nodes, and subsequently the common iliac lymph nodes. From here, efferent vessels pass to the lumbar lymph nodes and continue to the cisterna chyli, via the lumbar lymph trunk. The cisterna chyli drains into the thoracic duct, which finally terminates at junction of the left subclavian vein and left internal jugular vein.

Innervation

The innervation of the penis is handled by three major nerves: \n • The skin and the glans penis are supplied by the

dorsal nerve of the penis, which stems from the pudendal nerve and travels the length of the penis, beneath the deep fascia.

  • The skin of the proximal part of the body of the penis is supplied by the ilioinguinal nerve.
  • Finally, the erectile function is controlled by the parasympathetic nervous system; the pelvic splanchnic nerves in particular.

Highlights

The penis is the largest part of the external male genitalia and is made up of three main parts: the \n root, body, and glans penis. The root consists of the median urethral bulb and the crura, one on either side. The root lies in the perineum. The body of the penis stems from the superficial perineal space where it is attached to the perineal membrane.

It is made up of three masses of erectile tissue, which include the paired corpora cavernosa and the corpus spongiosum. The glans penis is the most distal portion of the corpus spongiosum and expands laterally at the distal aspect of the body of the penis, before narrowing at the very tip. It forms a bulbous shape and part of the bulb of the penis.

All the lymphatic vessels of the penis pass to the superficial inguinal lymph nodes by accompanying the external pudendal blood vessels. \n The innervation of the penis is handled by three major nerves: \n • Dorsal nerve of the penis \n • Ilioinguinal nerve \n • Pelvic splanchnic nerves

The arterial supply of the penis includes the: • Dorsal artery of the penis \n • Deep artery of the penis \n • External pudendal artery

Developmental disorders

Hypospadias

  •   Hypospadias is a developmental disorder where the meatus is positioned wrongly at birth. Hypospadias can also occur iatrogenically by the downward pressure of an indwelling urethral catheter. It is usually corrected by surgery.
  •   A micropenis is a very small penis caused by developmental or congenital problems.
  •   Diphallia, or penile duplication (PD), is the condition of having two penises. However, this disorder is extremely rare.

Clinical significance

Disorders

 Paraphimosis is an inability to move the foreskin forward over the glans. It can result from fluid trapped in a foreskin left retracted, perhaps following a medical procedure, or accumulation of fluid in the foreskin because of friction during vigorous sexual activity.

 InPeyronie'sdisease,anomalousscartissuegrows in the soft tissue of the penis, causing curvature. Severe cases can be improved by surgical correction.

Peyronie's disease

  •   Athrombosiscanoccurduringperiodsoffrequent and prolonged sexual activity, especially fellatio. It is usually harmless and self-corrects within a few weeks.

  •   Infection with the herpes virus can occur after sexual contact with an infected carrier; this may lead to the development of herpes sores.

  •   Pudendal nerve entrapment is a condition characterized by pain on sitting and the loss of penile sensation and orgasm. Occasionally there is a total loss of sensation and orgasm. The pudendal nerve can be damaged by narrow, hard bicycle seats and accidents. This can also occur in the clitoris of females.

  •   Penile fracture can occur if the erect penis is bent excessively. A popping or cracking sound and pain is normally associated with this event. Emergency medical assistance should be obtained as soon as possible. Prompt medical attention lowers the likelihood of permanent penile curvature.

Penile fracture

 In diabetes, peripheral neuropathy can cause tingling in the penile skin and possibly reduced or completely absent sensation. The reduced sensations can lead to injuries for either partner and their absence can make it impossible to have sexual pleasure through stimulation of the penis. Since the problems are caused by permanent nerve damage, preventive treatment through good control of the diabetes is the primary treatment. Some limited recovery may be possible through improved diabetes control.

 Erectile dysfunction is the inability to develop and maintain an erection sufficiently firm for satisfactory sexual performance. Diabetes is a leading cause, as is natural aging. A variety of treatments exist, most notably including the phosphodiesterase type 5 inhibitor drugs (such as sildenafil citrate, marketed as Viagra), which work by vasodilation.

 Priapism is a painful and potentially harmful medical condition in which the erect penis does not return to its flaccid state. Priapism lasting over four hours is a medical emergency. The causative mechanisms are poorly understood but involve complex neurological and vascular factors. Potential complications include ischaemia, thrombosis, and impotence. In serious cases the condition may result in gangrene, which may result in amputation. However, that is usually only the case if the organ is broke out and injured because of it. The condition has been associated with a variety of drugs including prostaglandin. Contrary to common knowledge, sildenafil (Viagra) will not cause it.

  •   Lymphangiosclerosis is a hardened lymph vessel, although it can feel like a hardened, almost calcified or fibrous, vein. It tends not to share the common blue tint with a vein however. It can be felt as a hardened lump or "vein" even when the penis is flaccid, and is even more prominent during an erection. It is considered a benign physical condition. It is fairly common and can follow a particularly vigorous sexual activity for men, and tends to go away if given rest and more gentle care, for example by use of lubricants.
  •   Carcinoma of the penis is rare with a reported rate of 1 person in 100,000 in developed countries. Some sources state that circumcision can protect against this disease, but this notion remains controversial among medical circles.

Carcinoma of the penis