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Male Reproductive - Seminiferous Tubules

Testis. Each testis is composed of an exocrine part (seminiferous tubules) and an endocrine part

(interstitial or Leydig cells). The testis is divided into lobules by septa consisting of loose areolar

connective tissue. Several seminiferous tubules are found in each lobule, and interstitial cells are

found in the connective tissue septa surrounding the seminiferous tubules. The seminiferous tubules

are the exocrine portion of the testis producing and "excreting" spermatozoa. These tubules are

lined by a stratified epithelium that consists of the developing spermatozoa and supporting cells

(Sertoli cells). View the image below at increasing magnification to see the structure of the

seminiferous tubules and note the appearance of the stratified epithelium which lines them.

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1. + low power

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2. ++

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3. +++

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4. ++++

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5. +++++

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6. ++++++ high power

Seminiferous tubules. The stratified epithelium of the seminiferous tubules is composed of different

stages of developing sperm cells. Spermatogonia are stem cells located near the basement

membrane of the tubule which proliferate by mitosis. Some of the progeny cells differentiate into

sperm and move away from the basement membrane toward the lumen of the tubule. These

differentiating cells first undergo meiosis then undergo a morphological change to become

spermatozoa. Some of the progeny cells undergo mitosis again to produce more progeny cells

providing a continuous source of stem cells for the production of spermatozoa. This entire process is

described in more detail on the next page.

Examine the images below to see the following developing sperm cells: (1) spermatogonia, (2)

primary spermatocytes, (3) secondary spermatocytes, (4) spermatids and (5) spermatozoa. The third

and fourth images also show Sertoli cells.

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1. Spermatogonia, Primary Spermatocytes,Spermatid

2. Primary Spermatocytes, Early Spermatids,Spermatozoa

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3. Primary Spermatocytes, Secondary Spermatocytes, Spermatids, Sertoli Cells

4. Spermatozoa, Sertoli Cells

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Interstitium. The interstitial tissue of the testis consists of loose areolar connective tissue containing

numerous reticular fibers which serves to support the seminiferous tubules. The interstitial cells

(Leydig cells), located in this connective tissue, are responsible for the synthesis and secretion of the

steroid hormone testosterone. The following images show the appearance of the interstitium and

Leydig cells in histological slides.

1. Leydig cells - low power

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2. Leydig cells - high power

Quick checks (try these to check your understanding of the material on this page):

Which part of the testis excretes spermatozoa?

tunica albuginea

seminiferous tubules

interstitium

Sertoli cells

Which part of the testis secretes testosterone?

Sertoli cells

Primary spermatocytes

Leydig cells

Spermatids