Reproduction 6 - Male anatomy Flashcards
What divides the scrotum into two halves?
septum of the scrotum.
What is the scrotum? Where is it? What is it a derivative of?
The scrotum is a cutaneous fibro-muscular sac for the testes and associated structures. It is situated posteroinferior to the penis and inferior to the pubic symphysis. The bilateral embryonic formation of the scrotum is indicated by the mid-line scrotal raphe, which is continuous on the ventral surface of the penis with the penile raphe.
What are the testes? What do they do?
The testes (testicles) are the male gonads. They are paired, ovoid reproductive glands that produce spermatozoa and male hormones, primarily testosterone.
Where are the testis?
The testis are suspended in the scrotum by the spermatic cords.
Describe the coverings of the testes
The surface of each testis is covered by the visceral layer of the tunica vaginalis, except where the testis attach to the epididymis and spermatic cord. The parietal layer of the tunica vaginalis is adjacent to the internal spermatic fascia, is more extensive than the visceral layer and extends superiorly for a short distance onto the distal part of the spermatic cord.
What is between the two layers of tunica vaginalis? Why?
There is a small amount of fluid between the two layers, in the cavity of the tunica vaginalis, allowing the testis to move freely in the scrotum.
What is the tunica albuginea?
A tough, fibrous outer surface, which thickens into a ridge on its internal, posterior aspect as the mediastinum of the testis.
Which part of the testes are sertoli cells associated with? What process are they involved in?
o Associated with Seminiferous Tubules o Spermatozoa development
What cells in the interstitial tissue secrete testosterone?
Leydig cells
In embryological development, where do the testes arise?
The testes arise in the Mesonephric ridge in the upper lumbar regions, at the lower pole of the kidneys
In the embryo, what are the testes tethered to and by what?
They are tethered to the labioscrotal folds, (Genital swellings, future scrotum), by the Gubernaculum.
Describe processus vaginalis
As the body grows, the relative position of the testis becomes more caudal. A musculo-fascial layer evaginates into the scrotum as it develops, together with peritoneal membrane to form the Processus Vaginalis.
What is the vestigial remnant of the gubernaculum called?
Scrotal ligament
Describe the venous drainage of the testis and why this is special
The venous drainage of the testes is asymmetrical. The veins emerging from the testis and epididymis form the Pampiniform Venous Plexus. This plexus is part of the thermoregulatory system of the testis, helping to keep the gland at a constant temperature. The veins of the plexus converge superiorly, forming the Right and Left Testicular Veins. The Right Testicular Vein drains into the Inferior Vena Cava (IVC) and the Left Testicular Vein drains into the Left Renal Vein. Testes –> Pampiniform Venous Plexus –> Right Testicular Vein –> IVC Testes –> Pampiniform Venous Plexus –> Left Testicular Vein –> Left Renal Vein The blood from the abdominal aorta is cooled as it passes through the testicular artery, as it is wrapped in the testicular vein.
Describe the blood supply to the testes
Arterial supply to the testes and epididymis is via the paired testicular arteries, which arise directly from the abdominal aorta. They descend down the abdomen, passing retroperitoneally and cross over the ureters and the inferior part of the external iliac arteries to reach the deep inguinal rings. The arteries then pass through the inguinal canal, emerging through the superficial inguinal rings and enter the spermatic cords.
Describe the structure and location of the epidymis
The Epididymis has a Head (Caput), Body (Corpus) and Tail (Caudal) segments. It is located on the superior and posterolateral surface of the testis.
What is the function of the epididymis?
The epididymis connects to the seminiferous tubule via efferent ductules and the rete testis. Its main function is sperm transport, maturation and storage.
Innervation of the testes
o Lumbar Plexus ▪ Anterior surface
o Sacral Plexus ▪ Posterior and inferior surfaces
Lymphatic drainage of the testes - why is it different?
o Testes ▪ Drains to paraaortic nodes o Scrotum ▪ Drains to superficial inguinal nodes Different drainage due to their embryological development
What is the ductus vas deferens, what does it do?
The Ductus Deferens (Vas Deferens) is a straight muscular tube that emerges from the caudal epididymis. It is contained within the spermatic cord and its main function is to transport the sperms rapidly to the prostatic urethra.
What feature helps the vas deferens to propel the tube’s contents towards the ejaculatory ducts?
Rich autonomic innervation of smooth muscle fibres of the ducts
The spermatic cord contains the structures running to and from the testes - what are they?
o Neurovascular
▪ Testicular Artery, Cremasteric Artery, Artery to Vas
▪ Pampiniform Plexus
▪ Genital branch of Genitofemoral Nerve
o Vas Deferens
o Lymphatics
o Processus vaginalis
Where does the spermatic cord run from and to?
It runs from the deep inguinal ring, lateral to the inferior epigastric vessels to the posterior border of the testis via the inguinal canal and superficial inguinal ring.
What are the seminal vesicles?
The seminal vesicles are two small glands that lie posterior to the prostate, between the bladder and rectum. The gland body consists of a single, highly convoluted tube that joins the ampulla of the ductus (vas) deferens to form the ejaculatory duct.
Where do the coverings of the spermatic cord come from? What are they?
The contents of the spermatic cord are mainly bound together by three fascial layers. They are all derived from anterior abdominal wall:
- External spermatic fascia – derived from the aponeurosis of the external oblique.
- Cremaster muscle and fascia – derived from the internal oblique and its fascial coverings.
- Internal spermatic fascia – derived from the transversalis fascia.
What runs through the prostate?
The urethra
Name the zones or lobes of the prostate
The prostate is divided into anatomical lobes (inferoposterior, inferolateral, superomedial, and anteromedial) by the urethra and the ejaculatory ducts as they pass through the organ.
However, more important clinically is histological division of the the prostate into zones:
- Central zone
- Transitional zone
- Peripheral zone
Outline the structure of the prostate
The gland is surrounded by a fibro-muscular capsule from which branching septae divide it into numerous small, but separate, compound alveolar glands from which excretory ducts originate and open independently into the prostatic urethra. The septae are characterised by discrete bundles of smooth muscle fibres interweaving with the connective tissues.
What do prostate secretions contain?
Prostaglandins, proteolytic enzymes and citric acid.
What volume of ejaculate is made up the the prostate?
~30%
What do bulbourethral glands do?
Just prior to ejaculation, these glands produce a clear water secretion that may lubricate the urethra
Where are the bulbourethral glands?
Enclosed within the fibres of the external urethral sphincter. They are situated posterolateral to the membranous urethra and superior to the bulb of the penis.
What type of glands do the bulbourethral glands contain?
Tubular and alveolar-type glands
Name three divisions of the penis
Root, body and glans.
What are the two internal structures of the penis?
Pair of Corpoa Cavernosa dorsally and a single Corpus Spongiosum ventrally.
Blood supply to the penis
Branches of the Internal Pudendal Arteries
Where does the internal pudendal artery originate from?
Abdominal Aorta –> Common Iliac à Internal Iliac –> Anterior Division of Internal Iliac –> Internal Pudendal Artery
