Testis

• Testis

  • Paired ovoid reproductive glands responsible for spermatogenesis and testosterone production.
  • Are suspended in scrotum by spermatic cord (left testis is suspend more inferiorly than right)
  • 10-15g
  • lies obliquely so that upper pole is forward laterally and lower pole mediallly.

  
• Testis has

  • 2 poles: upper and lower pole: are convex and smooth
  • 2 border: anterior border: convex and smooth + fully covered by tunica vaginalis. Posterior border: partially covered by tunica vaginalis and epididimis lies along lateral part of posterior border.
  • 2 surfaces: medial and lateral. Medial surface is separated from testis by an extension of the cavity of tunica vaginalis called sinus of epididimis
• Coverings of testis

  1. SCROTUM: outermost pouch of skin that protects and supports tests + helps regulates temperature in testis which is essential for proper sperm productio.
  2. TUNICA VAGINALIS: beneath scrotum: double-layered serous membrane derived from peritoneum.

  Parietal layer: outer layer lining inside of scortal sac

  Viceral layer: inner layer covering anterior and lateral aspects of testis

  Cavity of tunica vaginalis: small space btw parietal and viceral layers that contains thin film of fluid that allow mov of testes within scrotum.

  
• Coverings of testis


  3. Tunica albuginea: dense, fibrous capsule that encases each testis. This capsule extends inwards to form selta, diving testis into lobules.

  
• • Tunical albuginea thickens into a ridge on its posterior aspect as mediastenum testis
  • From this ridges, fibrous septa extend inward dividing testis into 250 lobules. Each lobule consists of 1-4 seminiferous tubules (coiled tubules where sperm is produced) and connective tissue stroma in which testosterone producing leyding cells are in.
  • These tubules become straight tubules posteriorly and anastomose forming the rete testis (network of canals in the mediastinum testis) .From the rete testis, 12-14 efferent ductules arise, pierce the tunica albuginea and pass into the head of the epididymis

  
• Sperm pathway

  • Sperm cells are produced in seminiferous tubules at rate 280000 per day in young adult.
  • Seminiferous tubules consists of seminiferous epithelium + tunica propria
  • Then sperm travel into straight tubles into rete testis and from there inti efferent ductules that lead sperm into epididymis.

  
• Seminiferous tubules are lined

  • sertoli cells (supportive cells that nourish developing sperm cells, secrete testicular fluid and form blood-testis barrier.
  • Spermatogenic cells: germ cells that undergo mitosis and meiosis to form spermatozoa
• Scrotum external features

  • Sac-like structure that hangs bellow penis. Divided into 2 compartments by a visible ridge called scrotal raphe.
  • Outer skin is thin, pigmented and covered with hair. Contains sebaceous and sweat glands.

  
• Layers of scrotum

  1. skin
  2. Dartos muscle: contracts in response to cold causing scro to wrinkle and draw testes closer to body to warm
  3. Superficial fascia
  4. External spermatic fascia
  5. Cremaster muscle
  6. internal spermatic fascia
  7. Tunica vaginalis: serous membrane that oartially covers each testis. Parietal and viceral layers with small amount of fluid between them.
• Structural components of testis

  1. Tunica albuginea: thick, fibrous capsule surronding the testis. Provides protection and gives rise to septa that divided testis into lobules
  2. Lobules: approximately 250 lobules. Each housing 1-4 coiled seminiferous tubules
  3. Seminuferous tubules: coiled structures where sperm production occurs.
• Cells within seminiferous tubules

  Spermatic cells: ( spermatogonia, 1 and 2 spermatocytes, spermatids and spermatozoa).

  Sertoli cells: true epithelium of seminiferous tubules.

  • supports + nourishes developing sperm cells); blood-testis barrier (form tight junction, protecting sperm from immune attack); phagocytosis; inhibin production to regulate FSH secretion.

  Leyding cells: found in interstitial spaces btw seminiferous tubules; produce testosterone in response to LH

  Myoid cell: smooth muscle like cells surrounding seminiferous tubules. Helps propel sperm through tubules
• Testes diagram

  
• • Sertoli cells produce androgen-binding protein (ABP) in response to follicle-stimulating hormone (FSH). ABP binds to testosterone, concentrating it in the seminiferous tubules and facilitating spermatogenesis.
  • These cells form tight junctions with each other, creating the blood-testis barrier. This barrier protects developing germ cells from harmful substances and immune reactions.
  • Sertoli cells provide structural support and nourishment to developing sperm cells (spermatogenic cells) during the process of spermatogenesis.
• • Leydig cells are found in the interstitial tissue of the testes, between the seminiferous tubules
  • Leydig cells synthesize and secrete testosterone in response to luteinizing hormone (LH) from the pituitary gland.
  • Testosterone is essential for the development of male secondary sexual characteristics, maintenance of libido, and promotion of spermatogenesis within the seminiferous tubules.
  • Besides testosterone, Leydig cells also produce small amounts of other androgens and steroid hormones, such as androstenedione and dehydroepiandrosterone (DHEA).