Histology of the Male Reproductive System 4

Question 1

Describe the sertoli cells in the seminiferous tubules and their functions.

Answer 1

• Cells interconnect with each other and surround developing gametes
• Functions:​
  
  • formation of blood-testis barrier
    
    • regulates transport of steroids and spermatogenic factors
    • protects sperm from immune system
  • metabolic support
    
    • regulation of movement of spermatogenic cells through the seminiferous epithelium
  • production of seminiferous tubule fluid
  • phagocytosis of shed cytoplasm during spermatogeneis and defectie/dead cells

Question 2

What are some of the major synthesis and secretion products of Sertolic cells?

Answer 2

• Anti-mullerian hormone
  
  • substance that inhibits development of female sexual development in the embryo/fetus
  • also inhibits acrosomal reaction in the adult
• Antigen-binding protein
  
  • concentrates testosterone in the seminiferous epithelium
    
    • creates a favorable environment for Leydig cell function
• Cytokines that regulate Leydig cell function
• Substances that feed back to adenohypophysis
  
  • regulates release of gonadotropin

Question 3

What are some important features regarding the structure of sperm cells?

Answer 3

• Head/nucleus is flattened and surrounded by enzyme-staining acrosome
• Core of the flagellum consists of axoneme with microtubules arranged as a cilium (central pair and outer doublets)
• Mitochondria surrounds the middle piece and power movement

Question 4

What is the time span of spermatogenesis and how is this clinically relevant?

Answer 4

• In humans, duration is of approximately 74 days followed by 12days of maturation in the epididymis
  
  • Developing sperm cells are part of the stratified epithelium
• Clinical relevance: any drug therapy for male infertility involving the initial phases of spermatogenesis may take 86 days to determine the effect

Question 5

Describe the process of spermatogenesis.

Answer 5

• Spermatocytogenesis (primordial spermatogonia cell division)
  
  • spermatogonia undergo mitosis
    
    • peripheral and in contact with basal lamina
• Meiosis of spermatocytes​
  
  • primary spermatocytes undergo the first meiotic division
  • from here, dividing cells retain cytoplasmic bridges with each other
  • further development occurs in clonal clusters with varying stages among clusters
  • secondary spermatocytes undergo the second meiotic division
• Spermiogenesis (morphological transformation of spermatids)
  
  • spermatids undergo a complex morphological transformation into spermatozoa
  • spermatozoa are released into the seminiferous tubule lumn, but they are not yet motile and are incapable of pertilizing and ovum
    
    • requires further maturation in epididymis and cpacitation in female reproductive tract

Question 6

What are the major changes that spermatids undergo to become spermatazoa?

Answer 6

• Elaboration of the acrosome from the Golgi complex
• Condensation of the nuclear chromatin into a highly insoluble, electron dense masss
• Wrapping of many mitochondria in the middle piece around the upper 1/3 of the developing tail
• Formation of 50 micrometer long motile flagellum
• Extensive shedding of cytoplasm that is taken up

Question 7

What is the epidydimis, and what are some important histological features?

Answer 7

• Structure with a head, body, and tail where the maturation of sperm occurs
  
  • sperm attain motility and undergo final morphological and biochemical changes here
  • takes two weeks to ass through the 15 feet of epididymis
  • stored at distal end (tail) until ejaculation
• Epithelium is pseudostratified columnar with stereocilia

Question 8

What is the structure and function of the ductus (vas) deferens?

Answer 8

• Continuation of the tail of the epididymus
• Three thick layers of smooth muscle (inner and outer longitudinal, middle circular) that have strong peristaltic contractions during ejaculation
• Epithelium is pseudostratified columnar with long microvilli (stereocilia) similar to epididymis epithelium
  
  • unlike the epididymis, the lumen of the ductus deferens does not appear circular because of the contracted state during fixation
• The ejaculatory duct forms after the terminal ampulla of the ductus deferens joins the duct of the seminal vesicles on the back of the prostate

Question 9

What is the makeup of semen?

Answer 9

• 2-6 mL
• 10% sperm
  
  • 20-100 million/mL
• 70% seminal vesicle secretions
• 20% prostate
• 25-50% of sperm are immotile and 20-40% are morphologically abnormal

Question 10

What is the structure and function of the seminal vesicles?

Answer 10

• Paired, highly, coiled tubular glands posterior to the urinary bladder and parallel to the ampulla of the ductus deferens
• Develop as evaginations of the mesonephric duct that gives rise to the ductus deferens and ejaculatory ducts
• Epithelium is pseudostratified columnar
  
  • mucosa elaborates into primary, secondary, and teriary folds like the uterine tubes
• Secretory product provides metabolic substrate for sperm
  
  • contains fructose and other simple sugars, amino acid, and prostaglandins

Question 11

What are the origins of the prostate gland and what is the makeup of its secretions?

Answer 11

• Develops from the splanchoplere of the urogenital sinus (which comes from the hindgut cloaca)
• Secretions contain enzymes that liquefy the viscous semen shortly after ejaculation
  
  • prostate specific antigen (PSA) - serine protease that is an important serum indicator of prostate cancer
    
    • increased production by cancer cells raises serum PSA levels, which are normally very low
  • serum prostatic acid phosphatase (PAP) is another postatic tumor