[With video] What is inside the male genitalia?

male genitaliaThe penis, also known as the urethra, is a core component of the human reproductive system. It is responsible not only for urination and ejaculation but also plays a crucial role in sexual intercourse. Its intricate structure, composed of multiple layers of precisely combined tissues, allows for rapid response to stimulation.erectionIt exhibits remarkable elasticity and functionality. According to medical literature, the average length of the penis is about 9-10 cm in a flaccid state and can reach 13-14 cm when erect, but there is a great deal of individual variation, which is affected by genetics, hormones and lifestyle habits.

The penis consists of two penises.Corpus cavernosumThe corpus cavernosa and the corpus spongiosum together form the urethra, with a small opening at the bottom that serves as the passage for urine and semen. The corpus cavernosum is surrounded by a tough tunica albuginea, and its expansion mechanism depends on the lacunae and vascular network. When stimulated, arterial blood rushes in, veins are compressed and closed, and pressure increases. The seminiferous tubules in the testes produce sperm and androgens. Unilateral orchiectomy has a limited impact; psychological factors are more crucial.

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External structure analysis

The external structure of the male genitalia can be divided into the penile shaft, glans penis, foreskin, and scrotum.

Penile shaft (shaft)
The penis shaft is the main part, approximately 8-12 cm long and 3-4 cm in diameter. It is covered with a thin layer of skin rich in nerve endings, making it extremely sensitive. It is soft when flaccid and hard as iron when erect. This is thanks to the internal corpus cavernosum structure, which we will discuss in detail later.

Glans (Glans Penis)
glans penisLocated at the tip of the penis, shaped like a mushroom, with a smooth and moist surface, it extends from the corpus spongiosum. The coronal sulcus of the glans is a sensitive zone surrounding the base of the glans. Circumcision removes the foreskin, exposing the glans and reducing the risk of infection. According to WHO data, approximately 301,000 men worldwide undergo circumcision, primarily in...MuslimandJewsCommunity.

Foreskin (Prepuce)
foreskinIt is a retractable skin fold that protects the glans. An overly long foreskin easily accumulates smegma, leading to balanitis. Milestone:Ancient EgyptThe circumcision was already being performed 3000 years ago, symbolizing adulthood.

Scrotum
scrotumHanging below the penis, it houses the testicles. Increased skin folds allow for heat dissipation, maintaining a testicular temperature 2-3°C lower than body temperature to ensure sperm survival.

1.external urethral meatus	2.glans penis	3.coronal sulcus	4.Corpus cavernosum of the penis	5. Corpus spongiosum	6.scrotum
7.Penis crest	8. Urethral bulb	9.anus	10.Frenulum	11.Penis root

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In-depth analysis of internal structure

The inside of the penis is composed ofTwo corpora cavernosa of the penisandA corpus spongiosumTogether they form a whole.

Corpus cavernosum of the penis
The two parallel corpora cavernosa, comprising 701 TP3T of the penis volume, are cylindrical in shape and extend from the pubic bone to the glans. They are surrounded by...A very tough white film(Tunica albuginea), approximately 2mm thick, rich in collagen fibers, prevents excessive swelling.

Internal structure:It consists of a large number of interconnected cavities and vascular networks.These cavities, like sponge pores, are lined with smooth muscle and endothelial cells. At rest, the smooth muscle contracts, limiting blood flow.

Corpus spongiosum
Located below the two corpora cavernosa, surrounding the urethra.The small hole below is the outlet of the corpus spongiosum.The external urethral meatus, approximately 0.6 cm in diameter, is...Channels for the expulsion of urine and semenDuring ejaculation, semen is expelled from the vas deferens through the urethra; during urination, urine flows into the bladder.

The corpus spongiosum is relatively soft, preventing pressure on the urethra during erection. The tunica albuginea is thin, allowing for slight expansion.

Blood vessels and neural networks
Arteries: The deep arteries of the penis supply the corpora cavernosa and are spiral-shaped to prevent twisting during erection.
Veins: The cavernous sinus veins drain water and are closed by pressure from the tunica albuginea during erection.
Nerves: The dorsal nerve of the penis transmits tactile sensation, and the parasympathetic nerves trigger erection.

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Erectile Mechanism and Physiological Process

The main function of expansion is a process of mutual generation and mutual generation with the sudden emergence of internal pores.—While this description is poetic, scientifically it refers to congestion of the cavity.

fromPhysiologyFrom a certain perspective, erection is due toBlood vesselandnerveBorn from the mechanism^.Its originparasympathetic nervous system（Autonomic nervous systemCaused by (part of) it will makeVasodilators——Nitric oxideAtpenisXiao Liangarteryandsmooth muscleThe concentration inside increased.arteryRelaxation and relaxationCorpus cavernosum of the penisandurinary tractCorpus cavernosumcongestionHowever, the lattercongestionThe degree is relatively low; at the same time, the ischiocavernosus and bulbospongiosus muscles will compress...Corpus cavernosum of the penisvein,limitbloodoutflow. whenparasympathetic nervous systemWhen activity subsides to a normal state, penile erection subsides. Human erections rely more heavily on the second signal system than those of other animals; they occur without a corresponding signal.erogenous zonesconductphysicsStimulateThis can trigger an erection.

Erection Steps

1. Stimulation phaseVisual, tactile, or psychological stimuli activate the parasympathetic nervous system, releasing nitric oxide (NO).
2. Blood flow:When our body is stimulated by external factors, a large amount of arterial blood rushes into these cavities, causing them to swell and expand..
3. Venous closureSmooth muscle relaxation, tunica albuginea compressionSimultaneously, the outflowing veins will temporarily close when compressed..
4. Increased pressure:It is this combined effect of massive blood influx and restricted outflow that causes the pressure within the corpora cavernosa to rise dramatically.The blood pressure reaches 100-200 mmHg, and the penis is as hard as bone.

Milestone: In 1998, Pfizer launched...Viagra(Viagra) inhibits PDE5 enzyme, enhances NO effect, and revolutionizes the treatment of ED (erectile dysfunction).

The top image shows a flaccid penis, and the bottom image shows an erect penis. An erect penis is mainly composed of three engorged tissues.

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Ejaculation and orgasm

ejaculationThe ejaculation process is divided into two phases: ejaculation (semen entering the urethra) and ejection (sperm being expelled through the urethra). The prostate and seminal vesicles contribute 901 TP3T of semen volume. During the ejaculation phase, sperm are ejected from...Epididymispassvas deferens,andmale accessory glandsThe liquid mixture entersurinary tractDuring the volleying phase,pelvic floorMuscles andbulbospongiosus muscleThe rhythmic contraction willsemenPush it towards the urethral opening and expel it from the penis in several jets.

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Testes and Hormone System

Although the penis does not directly contain the testicles, the testicles are an integral part of the reproductive system.

Sperm tubules
At the same time, the meandering, spiraling ducts that flow out are the site of sperm production and also the site of androgen secretion.Each testicle contains 250-300 lobules and 700 seminiferous tubules. It produces 100 million sperm daily.

1:testicular septum
2:fine tube
3:Testicular leaflets
4:Straight tubules
5:Output tube
6:Testicles website

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Unilateral testicular influence

Although men are born with two testicles, if one is accidentally removed, the remaining one is perfectly capable of carrying out reproductive functions.As long as hormone levels and sperm production are maintained,The impact on fertility and sexual function is very small.(The "exchange of eggs" may refer to the price "obtained"). After unilateral testicular resection, 90% is used to maintain fertility in patients with testicular cancer.

Even if you can't overcome the psychological hurdle, you can still have a complete life physically, as long as you maintain a positive and optimistic attitude.Psychotherapy, such as CBT, can help overcome this.

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Development and Embryology

Sexual differentiation begins in the 6th week of embryonic development. The SRY gene on the Y chromosome initiates testicular development, and the penis forms in the 9th week. During puberty, testosterone levels surge, and the penis grows by 50%.

Milestone: Embryonic stem cell research, 2023 laboratory culture of miniature penis tissue.

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Common Diseases and Prevention

• Erectile dysfunctionCauses: Diabetes, cardiovascular disease. Prevention: Exercise, blood sugar control.
• prostatitisBacterial infection, symptoms include painful urination.
• Penile cancerRare, HPV-related. Circumcision reduces the risk.
• phimosisSurgical correction.

The male reproductive organs are a miracle of life, and understanding their structure contributes to health. Whether it's unilateral testicular dysfunction or impotence, an optimistic attitude is key. Regular checkups, avoiding tobacco and alcohol, and enjoying a fulfilling life are essential.

Further reading:

• How, Why, and What They Do in Different Countries
• [Video] The relationship between blood vessels and male erections
• Why are penis beads popular in prisons?
• Why is a man without pubic hair called a "Qinglong"?