Anatomy & Physiology: Testis Penis Hosam Serag ST7 Urology University Hospital of Wales
Testis Dimensions: 4 to 5 cm long 3 cm wide 2.5 cm deep volume of 30 ml
Prader Orchidometer
Layers Visceral tunica vaginalis Tunica albuginea, Tunica vasculosa: is the vascular layer of the testis, consisting of a plexus of blood vessels, held together by delicate areolar tissue. It clothes the inner surface of the tunica albuginea and the different septa in the interior of the gland, and therefore forms an internal investment to all the spaces of which the gland is composed.
The epididymis attaches to the posterolateral aspect of the testis. The tunica albuginea projects inward to form the mediastinum testis, the point at which vessels and ducts traverse the testicular capsule. Septa radiate from the mediastinum to attach to the inner surface of the tunica albuginea to form 200 to 300 coneshaped lobules Leydig cells lie in the loose tissue surrounding the tubules
Testis
Spermatic cord Consists of 3 layers of fascia: Ext spermatic fascia Cremasteric muscle and fascia Internal spermatic fascia 3 arteries Testicular artery (from aorta) Cremasteric a. (from inferior epigastric) Artery of Vas (from inf. Vesical)
3 veins Pampiniform plexus of veins (right to IVC and Left to Left renal vein) Cremasteric V. Vein of the Vas 3 nerves Ilioinguinal (on the cord) Nerve to cremaster (from Genitofemoral) Sympathetic fibres 3 Other Vas deferens Lymphatics?patent processus vaginais
Nerve supply A portion arises in the renal and aortic plexuses and travels with the gonadal vessels Gonadal afferent and efferent nerves course from the pelvic plexus in association with the vas deferens
Retroperitoneal Lymphatics Lymphatics join posterior to the aorta at the level of the first or second lumbar vertebrae to form the thoracic duct There is flow not only cranially but also laterally, predominantly from the right to the left
Three major nodal areas : Right paracaval: nodal region extends from the midline of the IVC to the right ureter Interaortocaval: region extends from the midline of the IVC to the midline of the aorta Left para-aortic region: extends from the midline of the aorta to the left ureter
Lymphatic metastases from testicular tumors Drainage is consistent and follows the general scheme of vertical drainage with lateral flow from right to left. Lymphatic metastases from the right testis drain primarily into the interaortocaval nodes with significant drainage to the right paracaval nodes. In addition there is a small amount of drainage to the left para-aortic nodes. The left testis drains primarily to the left para-aortic nodes with significant drainage to the interaortocaval nodes. There is essentially no drainage to the right paracaval nodes from left-sided tumors.
Surgical considerations Gubernacular fibres attaching testicle to buttom of scrotum needs to be divided during radical orchidectomy,, be aware not to button hole the scrotal skin.
The epididymis attaches to the posterolateral aspect of the testis. Tunica albuginea projects inward to form the mediastinum testis, the point at which vessels and ducts traverse the testicular capsule Septa radiate from the mediastinum to attach to the inner surface of the tunica albuginea to form 200 to 300 cone-shaped lobules, each of which contains one or more convoluted seminiferous tubules. Each tubule is U shaped and has a stretched length of nearly 1 meter
Physiology Hormonal function Spermatogenesis
HYPOTHALAMIC-PITUITARY-GONADAL AXIS The hypothalamus secretes luteinizing hormone-releasing hormone (LHRH), also known as gonadotrophin-releasing hormone (GnRH). This causes pulsatile release of anterior pituitary gonadotrophins, follicle stimulating hormone (FSH) and luteinizing hormone (LH) FSH stimulates the seminiferous tubules to secrete inhibin and produce sperm. LH acts on Leydig cells to produce testosterone
Testosterone Secreted by the interstitial Leydig cells It promotes development of the male reproductive system and secondary sexual characteristics.
Spermatogenesis Seminiferous tubules are lined with Sertoli cells, which surround developing germ cells (spermatogonium), and provide nutrients and stimulating factors, as well as secreting androgen-binding factor and inhibin Primordial germ cells divide to form primary spermatocytes. a first meiotic division to create secondary spermatocytes (46 chromosomes) second meiotic division to form spermatids (23 chromosomes) differentiate into spermatozoa. Takes 70 days. The non-motile spermatozoa leave the seminiferous tubules and pass to the epididymis, for storage and maturation (until ejaculation).
Spermatogenesis in the seminiferous tubules of the testis
Penis
Size
Normal Size!! Length: 13.1 cm when erect Circumference: 11.6 cm when erect Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15521 men Veale et al, BJUI June 2015
Text Atlas of Penile Surgery D Yachia
Root: Lies in the superficial perineal pouch Three erectile bodies of the penis have their bony and fascial attachments The paired corpora cavernosa attach to the inferior ischiopubic rami and perineal membrane and are surrounded by the ischiocavernosus muscles The corpus spongiosum dilates as the bulb of the penis and is fixed to the center of the perineal membrane. It is encompassed by the bulbospongiosus muscles
Body The corpora cavernosa form the major portion of the body of the penis. They are separated by a septum that becomes pectiniform distally, so their vascular spaces freely communicate. They are enclosed by the tough tunica albuginea Distal to the bulb, the corpus spongiosum tapers and runs on the underside (ventrum) of the corpora cavernosa and then expands to cap them as the glans penis. Traversed throughout its length by the anterior urethra Buck fascia surrounds both cavernosal bodies dorsally and splits to surround the spongiosum ventrally
Campbell s Urology
Skin highly elastic, no subcutaneous fat The root of the penis is fixed to the perineum within the superficial pouch The corpora cavernosa join beneath the pubis
Arterial supply Internal Pudendal Artery a branch of Internal iliac (antyerior division) Accessory arteries : External iliac, obturator, vesical, femoral Internal pudendal aretry becomes the common penile artery. Penile artery branches Dorsal: Engorgment of glans penis. Bulbourethral: bulb and corpus spongiosum Cavernous artery: Tumescence of the corpus cavernosum Distally, they join to form a vascular ring near the glans Skin: Its blood supply is independent of the erectile bodies and is derived from the external pudendal branches of the femoral vessels
Venous Drainage
Venous Drainage Deep dorsal Vein: At the base of the glans, several venous channels coalesce to form the dorsal vein of the penis, which runs in a groove between the corporal bodies and drains into the preprostatic plexus Superficial dorsal vein: divides into 2 branches which join the superficial ext. pudendal veins or saphenous vein
Nerve Supply The dorsal nerves (one of 2 terminal branches of pudendal nerve) provide sensory innervation to the penis. Small branches from the perineal nerve supply the ventrum of the penis
Lymphatic drainage of Penis Skin of the penis and prepuce: Lymphatics drain primarily into the superficial inguinal lymph nodes Glans penis: Lymphatics drain into the deep inguinal and external iliac lymph nodes. May also drain into the superficial inguinal lymph nodes. Erectile tissue: Lymphatics drain into the internal iliac lymph nodes. Metastasis to pelvic lymph nodes is uncommon in the absence of inguinal lymphatic involvement. Penile urethra : Lymphatics drain into the internal iliac lymph nodes. Metastasis to pelvic lymph nodes is uncommon in the absence of inguinal lymphatic involvement
Ligaments of the Penis Suspensory ligament: Attached to the midline of the penile root rises from the linea alba and symphisis pubis. Contains mostly elastic fibers Fundiform ligament or ligament of Luschka: It fans laterally and ventrally to encircle the penile root
Hemodynamics and Mechanism of Erection And Detumescence In the flaccid state, these smooth muscles are tonically contracted, allowing only a small amount of arterial flow for nutritional purposes.
Sexual stimulation triggers release of neurotransmitters from the cavernous nerve terminals. This results in relaxation of these smooth muscles and the following events (1) dilation of the arterioles and arteries by increased blood flow in both the diastolic and systolic phases (2) trapping of the incoming blood by the expanding Sinusoids; (3) compression of the subtunical venous plexuses between the tunica albuginea and the peripheral sinusoids, reducing venous outflow
(4) stretching of the tunica to its capacity, which occludes the emissary veins between the inner circular and outer longitudinal layers and further decreases venous outflow to a minimum (5) an increase in PO2 (to about 90 mm Hg) and intracavernous pressure (around 100 mm Hg), which raises the penis from the dependent position to the erect state (the fullerection phase); (6) a further pressure increase (to several hundred millimeters of mercury) with contraction of the ischiocavernosus muscles (rigiderection phase).
Erection thus involves Sinusoidal relaxation Arterial dilation Venous compression
NO : Principal neurotransmitter. Potent relaxant of peripheral vascular smooth muscle. Action mediated by cgmp. cgmp degraded by type V phosphodiesterase, PDE 5. PDE-5 inhibitors increases cgmp enhance smooth muscle relaxation and erection.
References Campbell's Urology 10 th edition Text Atlas of Penile surgery. D Yachia