Reproductive System Week 4 Flashcards
Where do the testes develop?
In extra-peritoneal connective tissue in the superior lumbar region of the posterior abdominal wall
What structure connects the primordial testes to the anterolateral abdominal wall at the site of the future deep ring of the inguinal canal?
Gubernaculum
What is the processus vaginalis ?
A peritoneal diverticulum
Which traverses the developing inguinal canal, carrying muscular and fascial layers of the anterolateral abdominal wall before it as it enters the primordial scrotum
Where are the testis in the 12th week of development?
Pelvis
In what week do the testes begin to pass through the inguinal canal?
28th week
How long does it take for the testes to pass throught he inguinal canal?
3 days
At approximately which week do the testes enter the scrotum?
Week 32
How do derivatives of anterolateral abdominal wall muscles and fascia come to be in the adult scrotum?
As the testes, ductus deferens, and its vessels and nerves relocate they are ensheathed by musculofascial extensions of the anterolateral abdominal wall
What happens to the processus vaginalis?
Degenerates leaving behind a distal saccular part - forms tunica vaginalis - serous sheath of the testis and epididymis
When does the tunica vaginalis obliterate?
By the 6th month of development
What is the spermatic cord?
Contains structures running to and from the testis and suspends the testis in the scrotum
Describe the course of the spermatic cord
Begins at the deep inguinal ring lateral to the inferior epigastric vessels
Passes through the inguinal canal
Exits at the superficial ring
Ends at the posterior border of the testis
What are the fascial coverings of the spermatic cord and from which anterolateral abdominal wall layer are they derived?
Internal spermatic fascia - from transversalis fascia
Cremasteric fascia - from the fascia of both the deep and superficial surfaces of the internal oblique muscle
External spermatic fascia - from teh external oblique aponeurosis and its investing fascia
What is the cremaster muscle and where does it lie?
The cremasteric fascia contains loops of cremaster muscle
Formed from lowermost fascicles of internal oblique arising from inguinal ligament
What is the function of the cremaster muscle?
Reflexively draws the testes superiorly in the scrotum in response to cold and relaxes in response to heat- attempt to regulate the temperature of the testes for spermatogenesis and protect the testes during sexual activity
What temperature is required for spermatogenesis?
Requires constant temperature of around 1 degree below core body temperature
Which muscle works in conjunction with the cremaster muscle?
The Dartos muscle - smooth muscle of the fat-free subcutaneous tissue (dartos fascia) of the scrotum
Describe the function of the dartos muscle
Inserts into the skin of the scrotum
Assists in testicular elevation
Produces contraction of the skin of the scrotum in response to the same stimuli (temperature, protective during sexual activity)
Which nerve innervates the cremaster muscle?
The genital branch of the genitofemoral nerve (L1, L2) - derivative of lumbar plexus
What is the main difference between the cremaster and dartos muscle innervation
Cremaster - striated - somatic
Dartos - smooth muscle - autonomic
What are the constituents of the spermatic cord?
Ductus deferens - muscular tube - 45cm long - transports spermatozoa from epididymis to ejaculatory duct
Testicular artery - arises from aorta - supplies testes and epididymis
Artery of ductus deferens - arises from inferior vesicle artery
Cremasteric artery - arises from inferior epigastric artery
Pampiniform venous plexus - network of up to 12 begins - converge superiorly as either right or left testicular vein
Sympathetic nerve fibres on arteries and sympathetic and parasympathetic fibres on the ductus deferens
Genital branch of genitofemoral nerve - supplies cremaster
Lymphatic vessels - draining the testes and other associated structures - passes to lumbar lymph nodes
Vestige of processus vaginalis - fibrous thread in anterior part of spermatic cord - extending between abdominal peritoneum and tunica vaginalis - may not be detectable
What is the scrotum?
Cutaneous sac consisting of two layers:
Heavily pigmented skin
Closely related dartos fascia - fat-free fascial layer consisting of dartos muscle fibres - responsible for the rugosa (wrinkled) appearance of the scrotum
How does contraction of the dartos muscle reduce heat loss?
Reduces scrotal surface area
Thickens integumentary layer (skin etc.)
Assists the cremaster in holding the testes closer to the body
What is the septum of the scrotum?
A continuation of the dartos fascia
Divides the scrotum internally into right and left compartments
How is the septum of the scrotum demarcated externally?
Scrotal raphe - cutaneous ridge that marks the line of fusion of labioscrotal swellings
As what, is the dartos fascia continuous posteriorly and anteriorly?
Anteriorly - Scarpa fascia (membranous layer abdomen)
Posteriorly - Colles fascia (membranous layer perineum)
From what embryological derivative does the scrotum develop?
Labioscrotal swellings
Describe the arterial supply and venous drainage of the scrotum
Posterior scrotal branches of perineal artery - branch of internal pudendal artery
Anterior scrotal branches of deep external pudendal artery - branch of the femoral artery
Cremasteric artery - branch of the inferior epigastric artery
Scrotal veins accompany the arteries
Where do the lymphatic vessels of the scrotum drain into?
Superficial inguinal lymph nodes
Describe the innervation of the scrotum
Branches of lumbar plexus to anterolateral surface:
Genital branch of genitofemoral nerve (L1,L2) - supplies anterolateral surface
Anterior scrotal nerves - branches of the ilioinguinal nerve (L1) - supply anterior surface
Branches of sacral plexus to posterior and inferior surfaces:
Posterior scrotal nerves - branches of the perineal branch of the pudendal nerve (S2-4) - supply posterior surface
Perineal branches of posterior cutaneous nerve of thigh (S2,3) - supply posteroinferior surface
What are the testes?
The male gonads - paired ovoid reproductive glands that produce spermatozoa and male hormones (testosterone)
How are the testes suspended?
By the spermatic cord - left testis usually suspended more inferiorly than the right
Describe the layer covering the testes
Surface of each testes, parts of the epididymis and inferior part of ductus deferens covered by visceral layer of tunica vaginalis - except where testis attaches to epididymis and spermatic cord
What is the tunica vaginalis?
Closed peritoneal sac
Partially surrounds the testes
Represents the closed-off distal portion of the embryonic processus vaginalis
What is the sinus of the epididymis?
The slit-like recess of the tunica vaginalis
Between the body of the epididymis and the posterolateral surface of the testis
Where does the parietal layer of the tunica vaginalis lie?
Adjacent to the internal spermatic fascia
More extensive than the visceral layer - extends superiorly for short distance on to the distal spermatic cord
What is the function of the serous fluid in the cavity of the tunica vaginalis?
Allows the testis to move freely in the scrotum
What is the name of the tough fibrous outer surface of the testis?
Tunica albuginea
What is the mediastinum of the testis?
Thickened ridge of tunica albuginea
On internal posterior aspect of testis
What projects inwards from the medistinum of the testis?
Fibrous septa - between lobules of minute but long and highly coiled seminiferous tubules
Separates it into 250 pyramid-shaped lobules
Each lobule contains between 1 and 4 seminiferous tubules
What is the function of the seminiferous tubules?
Spermatogenesis
How are the seminiferous tubules joined to the rete testis?
By straight tubules
Describe the course of the testicular arteries
Arise from the anterolateral aspect of abdominal aorta just inferior to renal arteries
Pass retroperitoneally in oblique direction - over ureters and inferior parts of external iliac arteries to reach deep inguinal ring
Pass through inguinal canal to scrotum to supply testis
Anastomoses with artery of ductus deferens
Describe the venous drainage of the testis
Veins emerging from testis and epididymis form the pampiniform venous plexus (network 8-12veins )
Lies anterior to ductus deferens and surrounds testicular artery in spermatic cord
Part of the thermoregulatory system (along with cremasteric and dartos muscles) - helps to keep gland at constant temperature
Converge to form the right and left testicular veins superiorly
Right testicular vein enters IVC
Left testicular vein enters left renal vein
Describe the lymphatic drainage of the testis
Follows the testicular artery and vein to the right and left lumbar (canal/aortic) lymph nodes and preaortic lymph nodes
Describe the innervation of the testis
Autonomic nerves arise as testicular plexus of nerves on the testicular artery
Contains vagal parasympathetic and visceral afferent fibres, and sympathetic fibres from T7 of spinal cord
What is the epididymis ?
Elongated structure on posterior surface of the testis - transports spermatozoa from efferent ductules to ductus deferens
Formed by minute convolutions of the duct of the epididymis - so tightly compacted they appear solid
Describe the epididymis
Efferent ductules transport newly formed spermatozoa to the epididymis from the rete testis
Duct of the epididymis becomes progressively smaller as it passes from the head of the epididymis on superior testis to the tail
Head - superior expanded part - composed of lobules formed by the coiled ends of 12-14 efferent ductules
Body - consists of the convoluted duct of the epididymis
Tail of the epididymis continues as the ductus deferens - transports spermatozoa to the ejaculatory duct for expulsion through urethra during ejaculation
What are cryptorchid testes and what are the consequences?
Undescended testis
3% fullterm 30% premature infants
95% unilateral
Usually lies somewhere along the normal path of its prenatal descent - commonly inguinal canal
Germ cells absent - Sertoli and Leydig cells secrete male sex hormones still
Spermatogenesis impaired due to elevated temperature
Increased risk of malignant tumours - problematic because not palpable - not detected until late stages
What are oligozoospermia and azoospermia?
Oligozoospermia - abnormally low number of sperm in the semen
Azoospermia - no sperm in the ejaculate
What is orchitis and what are the consequences?
Inflammation of the testis
Occurs in some individuals who suffer from mumps after puberty
Impaired spermatogenesis
Occasionally leads to seminiferous tubule degeneration and sometimes infertility
What are the causes of an absence of germ cells?
Congenital
Acquired - drugs, viral infections, irradiation, cryptorchidism
Describe testicular tumours and their consequences
Rare
High degree of malignancy
Usually arise in germ cells
Present as swelling or lump in testes
Can spread to lumbar lymph nodes –> from here can metastasise to mediastinal and supraclavicular lymph nodes
Can spread by haematogenous route - bones, lungs, liver, brain
What is torsion of the spermatic cord and what are the consequences?
Twisting of the spermatic cord just above upper pole of testis
Surgical emergency
Obstructs venous drainage –> oedema, haemorrhage –> arterial obstruction
May cause necrosis of the testis
To prevent reoccurrence or occurrence on contralateral side both testes are fixed to the scrotal septum
What is the cremasteric reflex and how can it be elicited ?
Rapid elevation of the testis
Light stroke the skin on the medial aspect of the superior part of the thigh with an applicator stick or tongue depressor
Extremely active in children - may simulate undescended testes
Hyperactive reflex can be abolished by having the child sit cross-legged in a squatting position - if the testes are descended they can then be palpated
Describe ductus deferens
Continuation of the duct of the epididymis
Relatively thick muscular walls
Minute lumen
Cord-like firmness
Begins in tail of epididymis at inferior pole of testis
Ascends posterior to testes medial to epididymis
Primary component of the spermatic cord
Penetrates anterior abdominal wall via inguinal canal
Crosses over external iliac vessels and enters the pelvis
Passes along lateral wall of pelvis - lies external to parietal peritoneum
- maintains direct contact with it
Ends by joining the duct of the seminal glad to form the ejaculatory duct
Crosses over the ureter then posterior to the bladder descends medial to ureter and seminal gland
Enlarges to form ampulla of ductus deferens before its termination
Describe the arterial supply and venous drainage of the ductus deferens
Artery to ductus deferens - from superior or inferior vesicle artery - anastomoses with testicular artery posterior to testis
Veins from most of duct drain into testicular vein - including distal pampiniform plexus
Terminal portion drains into vesicular/ prostatic venous plexus
What is the seminal gland and what is its function?
Elongated structure lying between fundus of bladder and rectum
Obliquely placed, superior to prostate
Do not store sperm
Secrete a thick, alkaline fluid with fructose (energy source for sperms) and a coagulating agent that mixes with the sperms as they pass into the ejaculatory ducts and urethra
Superior ends covered with peritoneum, lie posterior to ureters, separated from rectum by rectovesical pouch
Inferior ends only separated form rectum by rectovesical septum
Duct of seminal gland joins ductus deferens to form ejaculatory duct
Describe the arterial supply and venous drainage of the seminal glands
Arteries to seminal glands derive from inferior vesical and middle rectal arteries
Veins accompany arteries and have similar names
Describe the ejaculatory ducts
Slender tubes
Union of ductus deferens and seminal gland
Approx 2.5cm long
Arise near neck of bladder
Run close together as pass anteroinferiorly through posterior prostate and along sides of prostatic utricle
Ejaculatory ducts converge
Open on the seminal colliculus by tiny, slit-like apertures on or within the opening of the prostatic utricle
Prostatic secretions do not join the seminal fluid until ejaculatory ducts terminate in prostatic urethra
Describe the arterial supply and venous drainage of the ejaculatory duct
Artery to the ductus deferens
Veins drain into the prostatic and vesical venous plexuses