Structure of the Male Reproductive System week 3 Flashcards
What are 3 functions of the male reproductive system?
What are the parts of the male reproductive system?
Function: Production of semen/gametes (i.e. seminal fluid and spermatozoa) and sex hormones Facilitation of fertilization: delivery of gametes into the female reproductive tract
Definition of the system: The male reproductive system is comprised of the testis, a system of genital ducts, accessory glands and the penis. The accessory glands consist of the prostate, seminal vesicles and the bulbourethral glands.
Where do testes develop? What do they have to pass through to descend into the scrotum?
What is crptorchidism?
The testes are paired structures located in the scrotum. They develop in the abdomen and descend into the scrotum by passing through the inguinal canal. Failure of the testis to descend into the scrotal sac is called Cryptorchidism and has implications on spermatogenesis and increases the risk of testicular malignancy.
What is the tunica vaginalis?
What kind of epithelium does it have? How many layers does it have?
What is its function?
The testes have important anatomic relationships to coverings and components of the scrotum. In histology we will see one component of these covering layers: the visceral layer of the tunica vaginalis. The tunica vaginalis is a double layer of squamous epithelium, shaped into a flattened balloon, located adjacent to the testis. It allows the testes to be moved within the scrotum.
What are the accessory glands of the male reproductive tract?
Where are the accessory glands located?
What are the functions of the accessory glands?
Describe the pH of semen.
The prostate gland is unpaired; it contains the urethra and receives the ejaculatory ducts. The seminal vesicles are paired glands located near the bladder and prostate gland. The ejaculatory ducts are the junctions of the vas deferens and the duct of the seminal vesicle. The bulbourethral glands secrete a mucous-like substance which lubricates the urethra. The accessory glands produce components of the seminal fluids. Hence, semen contains fluids from the accessory glands and sperm from the testes. Semen is alkaline which may assist in neutralizing the acidic environment of the vagina.
State where the tubules and ducts are located in the male reproductive tract and how they are connected to one another.
State which are intra- and extratesticular.
What structure divides the testes into lobules? What is this structure composed of?
- The testis has a hick connective tissue capsule called the tunica albuginea.
- Projecting from this capsule into the testis are septa that divide the organ into lobules.
What underlies the tunica albuginea? What is contained within this strucutre and what is this structure composed of?
What is the mediastinum? What is contained within the mediastinum?
What is contained within lobules of the tesits?
Underlying this capsule is a loose connective tissue layer that contains blood vessels; hence it is called the tunica vasculosa. Projecting from this capsule into the testis are septa that divide the organ into lobules. A thickened area of the capsule is called the mediastinum. Here the capsule thickens along the posterior surface of the testis and it contains blood and lymphatic vessels and a portion of the duct system; the rete testis. Each lobule consists of one to four seminiferous tubules. Connective tissue stroma surrounds these highly convoluted and looped tubules. The tubules end near the mediastinum in short straight tubules (tubuli recti). These tubuli recti are continuous with the rete testis, which is an anastomosing system of channels in the mediastinum.
Where are Leydig cells found?
Describe the appearance of Leydig cells.
What do Leydig cells secrete? What is its secretion important for?
Cells of Leydig
- found in clusters between the tubules
- large, polygonal in shape and they typically contain lipid droplets
- cells secrete testosterone throughout life
- testosterone is key for spermatogenesis and accessory glands and ducts and development of secondary sexual characteristics
Describe the length and arrangement of seminiferous tubules.
What is the name of the epithelium that lines seminiferous tubules? How many cell layers thick is it?
What surrounds seminferous tubules?
What are the 2 cell types present in seminiferous tubules?
Seminiferous tubules.
• each is 30-70 cm in length-highly convoluted. •
lined by seminiferous epithelium, (4-8 cell layers thick).
- surrounded by peritubular and interstitial tissue
- consists of 2 cell types: Sertoli cells and Spermatogenic cells.
Describe the appearance of Sertoli cells.
Where are Sertoli cells within the seminferous epithelium?
What cells do they surround?
Sertoli cells.
- has a pale, oval nucleus with prominent nucleolus.
- extends the entire thickness of the seminiferous epithelium.
- surrounds adjacent spermatogenic cells forming compartments within the thickness of the tubule.
What are the many functions of Sertoli cells?
- protect developing sperm cells from immune system. (gap junctions connect Sertoli cells) This creates the blood testis barrier. If not for this barrier, sperm could leak into blood and antibodies may be formed against them.
- support and nurture developing spermatogenic cells.
- secrete fluid into the lumen that facilitates transport of spermatozoa.
- secrete inhibin which inhibits FSH release by anterior pituitary. • synthesize androgen-binding protein (ABP) under the influence of FSH.
- testosterone binds to ABP-this complex exists in the lumen of the seminiferous tubules to maintain high concentrations of testosterone which enhances spermatogenesis.
- produce anti-mullerian hormone.
- phagocytose excess cytoplasm discarded by maturing spermatids.
How are spermatogenic cells arranged within seminiferous tubules?
What sperm cells are the most immature? Where are they located within the seminiferous tubules? What is the appearance of these cells?
What sperm cells are the most mature? Where are they located within the seminiferous tubules?
Spermatogenic cells (differentiate into mature sperm).
- arranged in ill-defined layers of advancing development between the Sertoli cells.
- the most immature cells, called spermatogonia rest on the basal lamina. Have a large round nucleus.
- the most mature cells, spermatids attached to the apical portion of the Sertoli cells extending into the lumen of the tubule.
Explain the process of spermatogenesis and the cell intermediates in this process.
Five categories of cells play a role in this process (spermatogenesis)
- Spermatogonia
- Primary spermatocyte
- Secondary spermatocyte (will not identify)
- Spermatids
- Spermatozoa
- Spermatogonial phase (spermatogonia form primary spermatocytes). Spermatogonia divide to replicate themselves and to produce primary spermatocytes. Full chromosomal amount.
- Spermatocyte phase (primary spermatocytes undergo two meiotic divisions to produce spermatids.) Cross over occurs in this phase and results in genetic exchange. The primary spermatocyte completes the first meiotic division, forming two secondary spermatocytes. These cells immediately enter the second meiotic division without synthesizing new DNA. When the secondary spermatocytes complete the second meiotic division they each give rise to two haploid spermatids.
- Spermatid phase
Explain what occurs during spermiogenesis.
Spermatid phase (a.k.a. spermiogenesis - spermatids differentiate into mature sperm cells).
- extensive cell remodeling but no cell division.
- formation of the acrosomal structure (which houses hydrolytic enzymes).
- acrosome expands over the nucleus.
- nucleus condenses to the head region.
- formation of flagellar structure.
- mitochondria aggregate around flagella.
- cytoplasm diminished and the tail elongates.
Describe the appearance of primary spermatocytes.
Fairly large round nuclei with heterochromatin
Describe the appearance of tubuli recti.
What kind of cells are present in tubuli recti?
What kind of epithelium is present in tubuli recti?
What part of the testis is the rete testis located?
What kind of epithelium is present within rete testis?
Tubuli recti are the terminal portion of the seminiferous tubules. They are best described as a series of short, straight tubules with a lining of Sertoli cells (only-no sperm!) transitioning to cuboidal epithelium.
Rete Testis are interconnecting channels in the mediastinum of the testis lined by a simple cuboidal epithelium, a feature to note is the presence of apical cilium.
Approximately how many efferent ducts are in each testis?
What kind of epithelium is present within efferent ducts?
What kind of muscle is present and why?
Efferent ducts are a collection of 10-20 tubules leading from the rete testis to the epididymis. These ducts are lined by pseudostratified columnar epithelium with cilia. One can note clumps of tall and short cells giving the cross-section of the duct a wavy appearance. These profiles of ducts are surrounded by smooth muscle-movement of sperm into epididymis.
Describe the lenth of the epididymis.
What is the function of the epididymis? What do sperm do in the epididymis?
What kind of epithelium is within the epididymis?
What are the 2 cell types in its epithelium?
What kind of muscle is located in the epididymis and why?
Epididymis is a highly coiled tube, 4-6 m in length. In this location the new produced sperm mature and acquire motility. These profiles of tubes are lined by a pseudostratified columnar epithelium with tall cells called principal cells and short cells in a basal position. The principal cells have stereocilia. Smooth muscle surrounds each duct profile (movement of sperm during ejaculation). The epididymis serves as a reservoir for mature sperm. Note the smooth lumen.
What kind of epithelium lines the vas/ductus deferens?
Describe the lumen of the vas deferens and compare it to the epididymis. What is the likely cause of the difference btwn these 2 lumens?
Vas or ductus deferens is a continuation of the epididymis. The vas is lined with pseudostratified columnar epithelium, resembling the lining of the epididymis. In contrast to the epididymis, the lumen of the duct does not appear uniform and smooth. This irregularity in shape is likely due to the contraction of the thick muscular coat of the duct during fixation and preparation of the tissue. Near the end the vas enlarges and joins the duct of the seminal vesicle to form the ejaculatory ducts which enter the prostate gland.
Where are the seminal vesicles located within the body?
What kind of epithelium do seminal vesicles have?
What is the appearance of the mucosa? How many lumens do seminal vesicles have?
What are the 2 components of the walls of seminal vesicles?
How much of the human ejaculate does semen produced by seminal vesicles comprise? What is contained within semen to provide sperm energy?
Seminal vesicles are highly folded paired glands located near the bladder. The epithelium is pseudostratified columnar. The mucosa is thrown into folds, giving the appearance of multiple chambers, however there is one lumen. The wall consists of fibroelastic connective tissue with some smooth muscle. The secretory product constitutes about 70% of the human ejaculate. It contains fructose (GLUT 5 transporter), which is the principal metabolic substrate for sperm. The smooth muscle will contract during ejaculation moving this fluid into the ejaculatory ducts and through the urethra. There is no sperm in the seminal vesicles.
What is the normal size and shape of the prostate gland?
What is the central lumen of the prstate?
What kind of glands are present within the prostate? What structure do these glands open into?
What kind of epithelium does the prostate have? What is its height influenced by?
What are prostatic concretions? Where are they found within the prostate gland?
What are the secretions from the prostate gland?
Prostate gland is the normal size and shape of a walnut. It has a central lumen which is the prostatic urethra. It consists of multiple (complex) tubuloalveolar glands, with multiple ducts which open directly into the prostatic urethra. The epithelium is typically simple columnar however, because these cells are influenced by testosterone, they may be cuboidal, squamous or pseudostratified. The alveoli may contain prostatic concretions (corpora amylacea) of varied shapes and sizes most commonly in older men. These concretions appear as concentric lamellated structures and may be formed by precipitation of secretory materials, they may be partially calcified. The prostate has a dense capsule. The secretions from the prostate gland include: Prostatic acid phosphatase (PAP), fibrinolysin, citric acid and Prostate-specific antigen (PSA) also known as the enzyme serine protease. This enzyme is secreted into the prostate gland alveoli and incorporated into the seminal fluid. Normal individuals have a low serum concentration of PSA. In prostate cancer, serum concentration of PSA increases and is used as a marker for presence and progression of the disease.
Within the prostatic urethra, describe the following parts:
urethral crest
prostatic sinuses
seminal colliculus
Prostatic urethra
- urethral crest – posterior wall; median ridge with grooves on each side
- prostatic sinuses – grooves on the sides of the urethral crest, openings for the prostatic ducts
- seminal colliculus – has openings for the ejaculatory ducts (2) and the prostatic utricle (blind pouch analogous to the uterus and vagina in the female)
What is contained within the corpus cavernosa and the 2 corpus spongiosum?
What binds the 3 parts of the penis together? What is the composition of this structure?
The penis consists of three separate cylinders of erectile tissue. In the histology lab we will see the erectile tissue mass that contains the penile urethra; called the corpus spongiosum. The other two masses are dorsally positioned and are called the corpora cavernosa. Each cylinder of tissue is a collection of irregularly shaped vascular spaces lined with vascular epithelium, the erectile tissue masses have trabeculae that contain elastic fibers and some smooth muscle interwoven around the vascular spaces. The erectile tissue masses are surrounded by a dense, fibroelastic layer called the tunica albuginea which binds these components of the penis together.
What kind of epithelium does the urethra have?
What glands are contained near the urethra and what is their function?
The urethra has a stratified epithelium that varies. It is transitional in some parts and pseudostratified in other parts.
Glands of Littre are responsible for secretion of mucus for lubrication of the urethra.
