The Testis, Epididymis, and Ductus Deferens Flashcards
the male reproductive system
functions primarily to produce sperm and transport it out of the body
- the testis is the site of sperm production and hormone secretion
- sperm produced in the testis is transported to the epididymis, where it is stored for maturation
- ductus deferens transports the sperm from the epididymis to the ejaculatory duct where seminal fluid from the ductus deferens and seminal vesicle is added
- from the ejaculatory duct, seminal fluid is transported into the prostatic urethra
- secretions from the bulbourethral gland are added to the seminal fluid as it travels to the penile urethra
- finally, the sperm is ejaculated out of the penile urethra
the testis
both an exocrine (producing spermatozoa) and an endocrine (producing hormones) gland
testis associated structures
tunica vaginalis
tunica albuginea
seminiferous tubules
rete testis
efferent ducts
epididymis
vas deferens
tunica vaginalis
each testis is covered by the tunica vaginalis, a serous membrane composed of CT lined by simple squamous epithelium
- has two layers that are continuous with each other: a visceral and parietal layer
tunica albuginea
deep to the tunica vaginalis
- a layer of dense CT which extends into the testis to form lobules
- at the posterior region of the testis, the CT that forms the albuginea thickens and protrudes into the testis, forming the mediastinum
introduction to the seminiferous tubules
tightly coiled tubules among the lobules
- where sperm is formed (spermatogenesis)
rete testis
sperm produced in the seminiferous tubules travels to a collection of tubules called the rete testis
efferent ducts
efferent ductules are a series of parallel, thin, delicate tubules that connect the rete testis to the epididymis
epididymis
a long, coiled tube that stores sperm and transports it from the testes
vas deferens
a long, muscular tube that transports mature sperm from the epididymis to the urethra in preparation for ejaculation
the seminiferous tubules: exocrine functions
the exocrine function of the testis is performed by the epithelium that lines the convoluted portions of the seminiferous tubules
- each convoluted tubule is lined by stratified epithelium composed of germ cells and Sertoli cells
seminiferous tubules: endocrine functions
endocrine functions of the testis occur within the CT stroma surrounding the seminiferous tubules, specifically by Leydig cells
Leydig cells
located in the CT stroma between seminiferous tubules,
produce androgens under the influence of LH from the pituitary gland
- specifically, the produce testosterone, which is necessary for sperm development
Leydig cell histology
they are polyhedral in shape, eosinophilic, and have large round nuclei
- cytoplasm is filled with vacuoles, which is typical of steroid producing cells
- the stroma of these cells have abundant blood vessels and lymphatics
Sertoli cells
nourish and protect germ cells during their formation before they are released into the lumen of the tubule
- they form the blood-testis barrier and do not divide
sertoli cell histology
they extend the entire thickness of the epithelium
- can be identified by their prominent nuclei, which are oval, euchromatic, and display a prominent nucleolus
- their outlines are difficult to distinguish due to cytoplasmic processes which extend between germ lines
germ cells
divide and differentiate to form spermatozoa (sperm) in a process called spermatogenesis
intratesticular tubules
immature sperm are transported through the testis to the epididymis via three intratesticular tubules, distinguishable by their different epithelia
3 intratesticular tubules
- the convoluted portion of the seminiferous tubule
- the straight portion of the seminiferous tubule
- the rete testis
convoluted portion of the seminiferous tubule
lined with stratified germinal epithelium
straight portion of the seminiferous tubule
loses its germ cells and is instead lined with simple columnar epithelium (Sertoli cells)
intratesticular tubules: rete testis
straight tubules continue into the rete testis, located within the mediastinum
- they transport sperm from the mediastinum, through the tunica albuginea, and continue into the epididymis as efferent ducts
- lined by simple cuboidal epithelium surrounded by CT
- some absorption of seminiferous fluid and sperm surface molecules here, which increases the concentration of sperm in the lumen
the epididymis
a comma shaped structure located on top of the testes
- has 3 divisions: a head, body, and tail
- primary function is to aid in sperm maturation, fluid secretion, fluid absorption, and storage of the sperm until ejaculation
epididymis head
in contact with the superior pole of the testes and contains efferent ducts and the duct of the epididymis
epididymis body
contains only the highly coiled ducts of the epididymis
- this duct can be differentiated from efferent ducts as they are larger with a wider lumen
- site of maturation of spermatozoa and sperm storage
epididymis tail
has the same histology as the body, only contains the duct of the epididymis
- site of maturation for spermatozoa and sperm storage
efferent ducts
arranged in a cone pattern that emerges from the testes
- they anastomose to become the highly coiled duct of the epididymis
- some of the columnar cells in duct epithelium have cilia at their luminal surfaces which help propel sperm through efferent ducts
- they have numerous lysosomes that are acidic staining with multiple granules. these absorb and breakdown testicular fluid that helps to move sperm cells. absorption of this from the lumen results in a higher concentration of sperm that ends up in ejaculate fluid
efferent duct histology
simple columnar epithelium composed of tall and short cells
- variation in height imparts a ‘scalloped’ border which is diagnostic for these
duct of the epididymis
larger and with a wider lumen than the efferent ducts
- lined by tall regular pseudostratified columnar epithelium that has both secretory and absorptive functions
- stored sperm are often found here
features of the epithelium of the epididymis
- stereocilia at the luminal surface
- smooth muscle that surrounds the epithelium of each duct. this layer increases in thickness as the duct progresses from the head to the tail
- basal cells at the base of the tall regular pseudostratified epithelium
ductus deferens
the duct of the epididymis exits the epididymis to continue as the ductus deferens
- ductus deferens travels within the spermatic cord, along with the testicular artery, the pampiniform plexus of veins, the cremaster muscle, nerves, and CT
ductus deferens histology
the ductus deferens is lined by pseudostratified columnar epithelium with stereocilia
- has a prominent lamina propria and three smooth muscle layers
smooth muscle layers of the ductus deferens
- inner longitudinal layer
- middle circular layer
- outer longitudinal layer
