7. Histology of the Male Reproductive System Flashcards
Why do we have sex?
What are the 2 sources of genetic variation in meiosis?
- Meiosis of one cell produces four genetically unique sex cells with half the chromosome number.
- Meiosis creates a genetic remix from each parent to create unique but related offspring.
- Meiosis generates genetic variability without mutation.
What is the main difference between Gamete formation in men and women?
Equal and Unequal Cell Division
- Gamete formation differs between the sexes.
- Meiosis (nuclear division) is identical in both males and females but cytokinesis (cell division) is not.
- MALES: each meiotic division with equal cytokinesis produces four small sperm cells (male gametes).
- FEMALES: each meiotic division with unequal cytokinesis produces one large egg cell (female gamete) and two or three polar bodies (discards).
What contributions do the sperm and ovum make in fertilisation?
Label the components of the sperm cell.
What is the structure & function of Spermatozoan?
- What does the acrosome contain?
- What connects the nucleus and the tail?
- Which organelle does the tail have a lot of?
- Acrosome - contains enzymes necessary for penetration of the zona pellucida prior to fertilization
- Nucleus - contains the haploid male contribution of DNA to be delivered to the oocyte at fertilization
- Centrioles - provides the physical connection between the nucleus and structural elements of the tail by means of the centrioles, from which the axoneme and outer dense fibres are formed
- Mitochondria - provides energy (ATP) for tail movement
- Flagella - provides motility to the cell to enable transport of the head (acrosome and nucleus) up the female tract and against the current carrying the oocyte down the Fallopian tube
How long is a mature sperm & how long are the individual parts?
- What is the structure of the endpiece?
mature sperm ~ 60 μm long
What are the components of the Male Reproductive Tract?
- Which components are involved in:
- sperm nourishment?
- fertilization assistance?
- channel lubricant?
- transport?
- sperm production?
- sperm lubrication?
Where in the testes are sperm produced?
Seminiferous tubules (produce sperm & testosterone) → Straight tubule → Rete testes → ductus epididymis (storage) → ductus deferens
Describe the development of the seminiferous tubules - 2 distinct phases?
Seminiferous Tubules
-
SEMINIFEROUS CORDS (BIRTH TO PUBERTY)
- no lumen
- large gonocytes
- support cells
-
SEMINIFEROUS TUBULES (PUBERTY TO OLD AGE)
- obvious lumen
- multilayer of cells
- sperm formation
- different stages
- Sertoli cells
- smooth muscle
- extra-tubular tissue
- Leydig cells
What are the 4 progressive layers of Spermatogenesis?
Progressive Layers
- Stem cells / spermatogonia (base)
- Early meiosis beneath late meiosis (middle)
- Immature & maturing spermatids (luminal)
- Fully formed non-motile sperm (in the lumen)
Describe the Sperm Form in Developmental Segments Along the Tubule?
What are the steps in Clonal Amplification and Synchronisation?
- What are the products of mitosis?
- What are Type A dark cells?
- What are Type A pale cells?
- What are Type B dark cells?
- What are the products of meiosis?
- What happens after Spermatogenesis?
What are the 3 phases of spermatogenesis?
- How long does spermatogenesis take?
- How long does it take sperm to move pass through the epididymis?
- Ideal body temperature for spermatogenesis?
- Spermatogonia phase – mitosis (basal compartment)
- Spermatocyte phase – meiosis (luminal compartment).
- Spermatid phase – spermiogenesis (luminal compartment).
Spermatogenesis takes ~74 days, passing through the epididymis takes ~12 days, most effective 2-3° < body T.
What happens during the Spermatid phase?
- What are the products?
- What are the 4 phases?
- Which cells phagocytose residual bodies?
- How many non-motile sperm are released into the lumen per day?
- Where does it go for storage?
Spermatid phase – spermiogenesis (luminal compartment).
- Spermatids (haploid: single chromatids) differentiate into spermatozoa (sperm).
- 4 phases:
- golgi
- cap
- acrosome
- maturation phase.
- Residual bodies phagocytosed by Sertoli cells.
- ~300million non-motile sperm released into the lumen (per day) & propelled to the epididymis for storage & maturation into motile sperm.
What are Spermatogonia?
Where are they located?
Staining?
Spermatogonia = Ovoid nuclei with finely granular chromatin (Type A) or clumped chromatin (Type B).
Located near BM, stain dark or light.
What are the 2 types of Spermatocytes? When are they usually seen?
Spermatocytes
- Primary: large, usually seen in prophase 1.
- Secondary: rarely seen since 2nd meiotic division is very rapid.
- Nucleus takes up a large portion of the cell.
What are Spermatids?
Spermatids
- Smaller cells, closer to lumen.
- Various stages: transition from round to elongated spermatids to sperm w/ tails in the lumen.
What are Sertoli cells?
- What type of epithelial cells are they?
- Where do they reside?
- Function - what barrier do they form?
- What do they secrete?
Sertoli cells = support (sustentacular) cells.
- Columnar epithelial cells with oval nucleus & obvious nucleolus.
- Span the full thickness of the wall & provide structural organisation to the tubule.
- Regulate sperm production, don’t divide after puberty.
- Junctions bind cells forming the blood-testis barrier, extensive apical & lateral processes surround adjacent spermatogenic cells.
- Secrete androgen binding protein (ABP) – concentrates T to (+) spermatogenesis, inhibin, plasminogen activator, transferrin, fluid to promote sperm expulsion etc.
What are Leydig cells?
- What do they secrete?
- Morphology?
- When do they reactivate?
- What happens to Sertoli cells with age?
Leydig cells = interstitial cells that secrete testosterone.
- Large polygonal, eosinophilic cells with lipid droplets, crystals of Reinke & lots of sER.
- Reactivate at puberty (anterior pituitary GH): sperm production, accessory sex gland activity, male 2° sex characteristics.
- ↓ T in old age can cause cessation of spermatogenesis & atrophy of Sertoli cells – become cuboidal or squamous & non-functional.
What is the histology of the semineferous tubules?
Seminiferous Tubules (sperm formation)
- Long, tightly coiled, horseshoe-shaped tubules, 30-80cm long, 150-250um diameter.
- Enclosed by a thick basal lamina & 3-4 layers of SMC, lined by Sertoli cells (columnar epithelial cells), which surround spermatogenic cells, with Leydig cells in the interstitium.
- 1-4 tubules/ lobule in the testis, enclosed by CT septa (extensions of tunica albuginea).
Describe the Transport of Sperm from the seminiferous tubules to the outside world.
- Which cells line the straight tubules?
- What type of epithelium is rete testis?
- What type of epithelium lines the efferent ductules?
- Where is most/the remaining fluid reabsorbed?
- What is seminal fluid rich in?
- What do the bulbourethral glands add?
- Multicellular seminiferous tubules →
- straight tubules lined by Sertoli cells →
- Rete testis (simple cuboidal) →
- efferent ductules (Pseudostratified columnar epithelium) reabsorbs most fluid →
- epididymis* reabsorbs the remaining fluid →
- vas deferens* →
- through seminal vesicles (60% seminal fluid, rich in fructose) →
- ejaculatory duct →
- through prostate gland (30% milky seminal fluid with enzymes) →
- urethra →
- bulbourethral glands add preseminal fluid with mucous.
What is the Histology of the Epidydmis?
- length?
- epithelium?
- feature?
- functions?
- Change in structure through the tube?
Epididymis:
- highly coiled tube 4-6 m in length
- pseudostratified columnar epithelium
- long microvilli (stereocilia) [small arrows] get shorter from head to tail
- reabsorbtion of remainder of fluid, phagocytosis of remaining residual bodies
- maturation of new sperm and phagocytosis of damaged sperm
- sperm acquire motility and the ability to fertilise an egg
- muscle coat thickens along its length to become three layered in the tail
What is the structure of the vas deferens?
What does it travel with (7) and in?
Vas deferens (ductus deferens)
- 3 layers of smooth muscle (inner + outer longitudinal, middle circular).
- Travels in spermatic cord with:
- Testicular artery.
- Artery of the ductus deferens.
- Cremasteric artery.
- Pampiniform plexus = a heat exchanger artery → veins
- Genital branch of the genitofemoral nerve.
- Parasympathetic and sympathetic nerves.
- Lymphatic vessels.
What is the Histology of the efferent ductules of the epididymis?
- how many ducts?
- length?
- epithelium?
- histo appearance of lumen?
- Function?
EFFERENT DUCTULES
- ~ 20 ducts join rete testis to head of epididymis
- each duct is 15-20 cm in length
- pseudostratified columnar epithelium
- sawtooth appearance of lumen
- clumps of tall ciliated cells
- clumps of short pinocytotic cells with microvilli
- resorbs most of the fluid from the seminiferous tubules
- thin layer of circular smooth muscle
What is the histology of the seminal vesicle?
- what type of gland?
- epithelium?
- What percentage of the seminal fluid does it produce?
- Which macromolecule is it rich in?
SEMINAL VESICLE
- convoluted tubular gland
- single lumen
- extensively folded mucosa (→ in LP)
- pseudostratified epithelium (basal cells marked by → in HP view)
- inner circular, outer longitudinal smooth muscle (SM)
- produces ~ 60% of seminal fluid
- fructose-rich fluid to nourish sperm
- forced fluid expulsion flushes sperm away from bladder and down urethra
What is the histology of the seminal vesicle?
- what type of gland?
- epithelium?
- What percentage of the seminal fluid does it produce?
- Which macromolecule is it rich in?
SEMINAL VESICLE
- convoluted tubular gland
- single lumen
- extensively folded mucosa (→ in LP)
- pseudostratified epithelium (basal cells marked by → in HP view)
- inner circular, outer longitudinal smooth muscle (SM)
- produces ~ 60% of seminal fluid
- fructose-rich fluid to nourish sperm
- forced fluid expulsion flushes sperm away from bladder and down urethra
What is the histology of the prostate gland?
- type/no. of glands?
- epithelium?
- What percentage of the seminal fluid does it produce?
- Contents of fluid?
PROSTATE GLAND
- 30-50 tubuloalveolar glands (Gl)
- simple or pseudostratified columnar to cuboidal or squamous epithelium showing terminal bars (arrows HP)
- fibromuscular stroma (collagen stained blue / muscle stained red)
- various sized concretions which are precipitations of secretory material
- produces ~30% of seminal fluid
- milky secretion contains enzymes to keep semen fluid and assist sperm forced expulsion flushes sperm
What is the histology of the bulbourethral gland?
- type of gland?
- cell type?
- ducts lined by which epithelium?
- function?
BULBOURETHRAL GLAND
- compound tubuloalveolar gland
- columnar mucous secreting cells
- ducts (D) lined by simple columnar epithelium
- Flushes & lubricates penile urethra with preseminal fluid
