Lecture 5: Male Reproduction Flashcards
What is the function of the testes?
Produces gametes (exocrine) (spermatozoa) and steroids (endocrine)
What is the function of the duct system?
Transport of gametes
What is the function of the accessory glands?
Produce additional additives to the semen
Additives
- fructose → seminal vesicles
- citric acid, fibrinolysin, PSA → prostate
Where does the production of sperm occur? Where does it travel after this?
Produced in the testis → carried externally through the duct system → exits through the penis
Testes (produce sperm) → epididymis (duct system) → vas deferens (duct system) → seminal vesicles (accessory gland) → prostate gland (accessory galnd) → urethra (penis)
What are the layers of the scrotum (4)?
- Skin
- Dartos muscle (from the membranous layer of superficial fascia)
- Colles’ fascia (CT)
- Parietal tunica vaginalis (from peritoneum)
Skin → dartos → colles fascia → parietal tunica vaginalis → visceral tunica vaginalis → tunica albuginea → testis
What are the layers of the testis (2)?
- visceral tunica vaginalis
- tunica albuginea
Skin → dartos → colles fascia → parietal tunica vaginalis → visceral tunica vaginalis → tunica albuginea → testis
Where is the testis located?
in the scrotum
Where are Leydig cells located within the testis? What is their function?
- within interstitial space of testis
- produce testosterone
Where does gametogenesis occur within the testis?
- Occurs within the seminiferous tubules
- Also contain supporting Sertoli cells
What structure divides the testis into lobules?
septum from the tunica albuginea
What two structures make up the tunica albuginea?
mediastinum + septum
Mediastinum → thickened area of posterior aspect of testis = vessels, nerves, and ducts enter and leave here
What are the 2 compartments of the testis? What does each contain?
- interstitial compartment → contain vasculature, lymphatics, and Leydig cells
- seminiferous tubule compartment → divided into basal and adluminal compartments by Sertoli - Sertoli cell tight junctions
Tubular wall → made of fibroblasts + CT
What compartment is the largest in the fetal testis? What does this compartment contain?
- interstitial comparment is the largest
- Leydig cells are indistinct and mostly nonfunctional
- Tubules contain supportive cells and gonocytes but lack a lumen
Gonocytes → pale staining precursors to the germ cells
Supportive cells → early Sertoli cells
What is the tunica vaginalis?
- layer of the scrotum
- thin layer of CT covered by mesothelium
What is the tunica albuginea?
- layer of the testis
- thick layer of CT which contains the functional parts of the testis
Which cells are the primary producers of testosterone? Where are they located?
- Leydig cells
- Interstistial space of testis
Has round nucleus often seen with a ring of heterochromatin
Cells that produce steroids are characterized by an abundance of certain organelles. These include which organelles (3)?
- Golgi → lipid transport
- sER → steroid hormone synthesis
- Mitochondria with tubular cristae
What is testosterone derived from? What stimulates its secretion?
- Derived from cholesterol
- Stimulated by the action of luteinizing hormone (LH) from the anterior pituitary
LH secreted by basophils
What are the functions (2) of inhibin (from Sertoli cells)?
- inhibits activation of LH release = prevents testosterone production
- inhibits FSH + LH in the anterior pituitary
- Negative feedback loop
What is the function of the androgen-binding protein (ABP)?
Binds testosterone to keep it in the tubules = ↑ testosterone
What 4 cells increase testosterone?
- LH
- FSH
- Leydig cells
- ABP (sertoli)
What separates the seminiferous tubule from the interstitium? What is it made up of?
- Separated by tubular wall → made up of CT layers → layers of fibroblasts and a distinct basement membrane
What are the supporting cells aka “nurse cells” of the seminiferous epithelium (simple columnar)?
Sertoli cells
Rests on the basement membrane and reaches to the luminal surface
One of the primary functions of the Sertoli cell is the formation of speciliazed junctions. What are the 2 most important?
- Sertoli-Sertoli junction → divides epithelium into a basal & adluminal compartment
- Sertoli-Spermatid junction → forms as the spermatid reaches the luminal edge
Sertoli-Sertoli junction → in basal compartment
Sertoli-Spermatid → in adluminal compartment
What are the functions of the Sertoli-Sertoli junction (2)?
- Excludes most substances from reaching the adluminal compartment forming a blood-testis barrier
- Important in protecting the developing germ cells
What are the functions of the blood testis barrier (2)?
Sertoli-Sertoli junction
- Protects the germ cells from autoimmune destruction
- Prevent nutritional components from reaching the later stages of the germ cells
What is the result of the blood-testis barrier being broken down?
Destruction of the germ cells and infertility → immune cells see sperm as non-self and attack the cells
What is the function of the antimullerian hormone?
Only in females
prevents development of the mullerian duct
What cell produces the androgen binding protein, antimullerian hormone, inhibin and transferrin?
Transferrin → transfers iron
Sertoli cell
Where does spermatogenesis begin? What is the result?
In the basal compartment with the mitotic division of dark A spermatogonia → results in the production of Type A pale and dark
Spermatogonia → Type A (diploid) → Type B (diploid) → 1° spermatocyte (diploid) → 2° spermatocyte (haploid) → spermatid (haploid) → sperm (haploid)
What does the Type B spermatogonia divide mitotically to form?
primary spermatocytes
After formation of primary spermatocytes, meiosis begins in the ______ compartment.
adluminal
What is the result of the first meiotic division in spermatogenesis?
Results in secondary spermatocytes and these divide in the second division to form spermatids
What do the early spermatids in spermiogenesis differentiate into?
elongated spermatids and the mature sperm (aka spermatozoa) in lumen
Why is the development of germ cells in spermatogenesis not synchronized throughout the tubule?
Allows for constant production of sperm
Different from females who are born with a set number of eggs
What is 1 important factor that can cause the degradation of the seminiferous epithelium?
increased temperature such as occurs in cryptorchidism
cryptorchidism = a condition in which one or both of the testes fail to descend from the abdomen into the scrotum
Explain the flow of sperm
seminiferous tubule → tubulus rectus → rete testis → ductuli efferentes → epididymis → vas deferens
What makes up the epithelium of the tubuli recti?
Sertoli cells → become more cuboidal as you move towards the rete testis