Male Reproductive System Flashcards
Function of male reproductive systme
- Reproduction
- Production of androgens for reproduction & development of secondary male characteristics
Testis function
Spermatogenesis
Steroidogenesis: production of androgens (testosterone)
The adrenal glands are responsible for producing only <5% of testosterone, the rest is in the testis
Structure of testis
- Tunica albuginea: thick, dense irregular connective
-
Mediastinum testis: inward projection of thickened tunica albuginea in posterior surface of the testis
- Excurrent ducts, blood vessels, and lymphatic vessels go through here
- Septa: connective tissue projected from the capsule separating each testis into lobules
Where do blood vessels and efferent ductules go through?
Mediastinum: connective tissue region
Rete testes
Maze of interconnecting channels within the mediastinum testis.
Gives rise to straight tubules/tubuli recti, which leads to convoluted seminiferous tubules
A single testicular lobule (L) is composed of
1-4 highly convoluted seminiferous tubulesspread throughout interstitialconnective tissue stroma
Interstitial connective tissue between seminiferous tubules
Loose connective tissue containing
- Fibroblasts - flat nuclei (mouse arrow)
- Leydig/interstitial cells - lots of cytoplasm
Leydig cells - what is their function?
Synthesize & secrete testosterone
How do Interstitial/leydig cells appear histologically?
- Forms small clusters
- Round or polygonal in shape
-
Acidophilic cytoplasm
- Like all steroid-producign cells, they have a elaborate sER and a lot of lipid droplets
- Large & round nucleus*
Function of seminiferous tubule
Sperm production
super long and convoluted
Wall of the seminiferous tubule
-
Lamina/tunica propria outer):
- Myoid cells
- Collagen
- Basement membrane
-
Seminiferous / Complex stratified epithelium
- Sertoli/supporting cells
- Spermatogenic cells
Myoid cells
flat, elongated smooth-muscle-like cells whose contraction moves sperm & fluid ino the excurrent duct system
(flat nucleus above mouse arrow)
Describe seminiferous / complex stratified epithelium of the seminiferous tubule
One single layer of sertoli cells surround multiple layers of spermatogenic cells
Sertoli / Supporting / Sustentacular cells’ functions
- Gives structural organization to the tubules
- Extends from the basement membrane to the luminal surface of the seminiferous epithelium
- Doesn’t replicate after puberty
- Extends from the basement membrane to the luminal surface of the seminiferous epithelium
- Support/nurse maturing sperm cells
- Phagocytose unneeded cytoplasmic portion of developing sperm and any messed up spermatogenic cells
- Forms blood-testis barrier by forming tight junctions between Sertoli cells dividing the epithelium into basal and adluminal compartments
- Exocrine & endocrine secretions - androgen-binding protein, estrogen, inhibin, MIF, growth factors
Spermatogenic cells characteristics
- Replicates & differentiates into mature sperm
- Organized in poorly dfined layers of progressive development:
- Spermatogonia (most immature) rests on basal lamina
- Spermatids (most mature) attached to apical portion of the Sertoli cells, where they border the tubule lumen
5 types of spermatogenic cells from immature to most mature
Spermatogonia (most immature)
Primary spermatocytes
Secondary spermatocytes
Spermatids
Spermatozoa (z last letter of alphabet!)
3 phases of spermatogenesis
1) Mitosis: spermatogonia self-replicate and differentiate into primary spermatocyte
2) Two rounds of Meiosis:
primary spermatocyte
> 2 secondary spermatocytes
> 4 spermatids
3) Spermiogenesis: spermatids transform into spermatozoa
The most mature form of sperm that is still within the seminiferous tubule epithelium is ___.
At what point does the thick cytoplasmic bridge connecting them disintegrate?
Spermatids
Bridge doesn’t disintegrate until released from epithelium
What is the function of the cytoplasmic bridge?
- Ensures synchronous development
- Allows free cytoplasmic communication among cells
- Allows sharing of gene products among haploid cells
- –> So they can have the proteins and RNAs encoded by the complete diploid genome
Spermatogonia appearance
- Large
-
Round nucleus w diff patterns of chromatin
- Don’t have to recognize, but there are 3 types (Type A dark, type A pale, and type B) because they undergo asymmetric cell division (shown among the 3 in the photo).
- In contact with the basal lamina
Primary spermatocyte appearance
- Largest germ cell; above spermatogonia
- Spherical or ovoid
- Large, round nucleus w strands of heterochromatin
These will divide and differentiate into
primary spermatocytes
because this is spermatogonia
These will under go ____ to produce ___
These are primary spermatocytes - they will undergo first meiosis to produce 2 secondary spermatocytes
Introduces genetic variation (by chromosomal crossover and random inclusion of either parental chromosomes) to increase genetic variability of the gamete.
Secondary spermatocytes appearance
Seldom seen in histological preparations because they immediately enter and complete teh second meiotic division! Don thave to recognize
These will undergo ___ to produce ___
These are spermatids and they will undergo spermiogenesis (structural changes) to become spermatozoa
Early vs late spermatids
Early: small; round nuclei w condensed chromatin
Late: elongated nucleus; tail; on the apical portion of Sertoli cells, bording lumen of tubule
Spermiogenesis
transforms spermatids to spermatozoa through 4 overlapping processes:
- Nuclear condensation & elongation
- Acrosome formation
- Flagellum formation
-
Cytoplasm reduction : elimination of cytoplasm by Sertoli cells and release into the lumen of seminiferous tubules
- <em>Spermiation</em>: release of spermatozoa to the lumen; determines how much sperm ends up in semen
In the release of spermatozoa into the lumen, much of the cytoplasmic portion (residual body)
that cytoplasmic bridge holding them together is phagocytosed by sertoli cells
pictured w mouse arrow: free spermatozoa in lumen
When do spermatozoa become motile?
They develop the capability to move and fertilize in the epdidymis , where they are stored at the distal portion before ejaculation
Spermatozoa survival in male vs female reproductive system
spermatozoa live for wks in male excurrent duct system
survives 2-3 days in female reproductive tract
Endocrine secretions of Sertoli Cells
-
Estradiol
- Aromatase in Sertoli cells ( in neonatal and prepubertal mammals) converts testosterone to estradiol to regulate spermatogenesis and to inhibit testosterone production by Leydig cells
- Inhibin B provide negative feedback on gonadotroph’s FSH synthesis and release from the adenohypophysis
-
Mullerian-inhibiting factor (MIF) causes regression of embryonic mullerian ducts
- Inhibits development of female reproductive tract
- Growth factors (GDNF & stem cell factor): maintain the number of spermatogonia
Appearance of sertoli cells under light microscope
-
OVOID or TRIANGULAR NUCLEUS
- large & lightly stained
- may have 1 or more deep infoldings
- Prominent nucleolus
- Tall, columnar cell
Exocrine secretions of the sertoli cells
Fluid: facilitates passage of maturing sperm along teh seminiferous tubules to the itnra-testicular ducts
Androgen-binding protein (ABP): binds testosterone and makes it less lipophilic & highly concentrated within the luminal fluid of the seminiferous tubules to stimulate sperm development
Appearance of sertoli cells under electron microscope:
- extensive sER, lipid droplets
- Lots of mitochondria
- Well-developed rough ER & Golgi
- Lateral processes surrounding the adjacent spermatogenic cells
- Tight junctions
What are teh arrows poitning at
the tight jxns between two sertoli cells
____ divides the epithelium into ___ and ____ compartments.
What type of cells are restricted to each compartment?
Tight jxns between Sertoli cells divide the epithelium into basal and adluminal compartments.
Basal compartments = spermatogonia & early primary spermatocytes
Adluminal compartments = everything else
When early spermatocytes pass through the tight jxn to move from the basal to the adluminal compartment, is there a breakdown of the blood-testis barrier?
No - otherwise, you’d see spermatids in the blood
What happens is that the sertoli cells form new tight junctions below the newly formed spermatocytes, followed by breakdown of the junction above them
Meiosis & spermiogenesis occur in which compartment
Adluminal
Blood-testis barrier
- Physiologic division formed by tight jxns within seminiferous epithelium with respect to ionic, aa, carbs,a nd proteins.
- –> luminal fluid is diff from blood plasma & testicular lymph
- –> isolates the genetically different and thus antigenic haploid germ cells from the immune system
Temperature regulation of the testis to protect spermatogenesis
- Cremaster reflex: contraction & relaxation of the cremaster (skeletal) muscle to bring the testes towards or away from the heat of the body
- Col temperature causes the dartos (smooth) muscle to contract so the scrotum wrinkles to regulate heat loss
- Smooth = striations
- The testicular artery is surrounded by the pampiniform venous plexus (which is cooler blood)
What kidn of cells are the top left two Y’s pointing at?
Top is pointing at the interstitium –> Leydig cells
Bottom one has that dark nucleolus–> Sertoli cells
Wheres the Sertoli cell here?
Dark nucleolus
Recap on seminiferous epithelium
Cryptochordism
Undescended testes - testes temp is the same as body temp, which will degenerate most spermatogenic cells (except spermatogonia)
–> only see interstitial structures
Why do the veins of the pampiniform plexus have such thick smooth muscle structure?
It has to propel the blood against gravity back up into the abdominal veins from the testes
What is this
testicular artery (center) surrounded by pampiniform veins
is this cremaster or dartos?
cremaster because it’s skeletal muscle (nucleus in periphery, striations)
Testis
Tunica albuginea
spermatogonium
primary spermatocyte
Sertoli cell
Spermatid
Spermatozoa
myoid
leydig
