REPRODUCTIVE SYSTEM: MALE

I.   INTRODUCTION
–  both male and female reproductive systems consist of:

1)  gonads (primary sex organs):  testes in the male, ovaries in the female

*  functions: 

1) produce gametes (sex cells): sperm or oocytes
2) produce sex hormones

2)  accessory reproductive organs:  include “ducts” that transport/store the gametes, glands that secrete substances for the gametes’ well-being, and the external genitalia              

–  the reproductive system is not fully functional until puberty

--  at puberty, hypothalamus secretes hormones that tell anterior pituitary to release FSH (follicle stimulating hormone) and LH (luteinizing hormone), which act on ovaries and testes

--  so you need FSH and LH to start gamete maturation and increased sex hormone production by the gonads

II.  TESTIS (Plural: testes, testicles)
–  functions: 

A.  External Anatomy:
–  testes suspended in scrotum

*  function of scrotum:

–  a spermatic cord runs from each testis to the abdomen
*  contains blood vessels and nerves and the ductus (vas) deferens

B.  Internal Anatomy:
–  each testis divided into a series of internal compartments called lobules

--  each lobule contains up to 4 seminiferous tubules (a tightly coiled structure, where sperm are produced)
–  within the seminiferous tubules are:

1)  spermatogonia:

2)  developing sperm

3)  Sustentacular cells:

–  between seminiferous tubules is some connective tissue, with interstitial cells

*  function of these cells:

III. SPERM PRODUCTION

–  sex cells (gametes) created by MEIOSIS
*  review your meiosis notes!

*  end result of meiosis: 4 cells produced, each w/23 chromosomes only!

–  start off with spermatogonia (each contains 23 pairs of chromosomes)

–    spermatogonia divide by MITOSIS and produce spermatocytes

–  primary spermatocytes contain 23 pairs of chromosomes (46 chromosomes)

*  these cells divide by MEIOSIS
*  when they finish the 1st meiotic division, they form secondary spermatocytes

--  secondary spermatocytes contain 23 chromosomes only

*  they finish the 2nd meiotic division
*  they produce spermatids

–  spermatids: immature sperm - contain 23 chromosomes only

–  spermatids develop into sperm (spermatozoa)

*  sperm will “shed” the cytoplasm from the spermatid, and develop:

1) head:  contains DNA

*  on head is an acrosome cap

2) midpiece:

3)  tail:

–  sperm are then released from the sustentacular cell cytoplasm, and enter the lumen of seminiferous tubule

IV.  SPERMATIC DUCT SYSTEM

A.  Epididymis: comma-shaped organ, located posterior to and on top of testis
*  receive sperm from testis

*  functions: 

B.  Ductus (Vas) Deferens:  18 inch long tube that runs from testis to prostate gland
*  part of its travel is within the spermatic cord
*  then it enters the abdominopelvic cavity, winds around the bladder, and is found near the prostate gland
*  ductus deferens will “merge” with the duct in the seminal vesicle to form the:

C.  Ejaculatory Duct: each one will empty its contents into the urethra

V.   ACCESSORY REPRODUCTIVE GLANDS
–  function of these glands: to produce a nutritive, alkaline fluid (seminal fluid) to the sperm

sperm + seminal fluid = semen

A.  Seminal Vesicles: (2)  each lies on posterior wall of bladder
*  each has a “duct” that merges with the ductus deferens, to form ejaculatory duct

B.  Prostate:  single, chestnut-shaped organ
*  inferior to bladder
*  contains the 1st part of the urethra (prostatic urethra)

C.  Bulbourethral Glands: (2)
*  each gland is pea-shaped
*  lies within urogenital diaphragm

VI.  PENIS
–  is part of the external genitalia
–  two main functions:

–  3 parts:

1)  root:  “fixed” end of penis

2)  body (shaft):  moveable end

*  3 columns of erectile tissue:

*  (2) corpora cavernosa: two masses of tissue on the top (dorsum) of penis
*  (1) corpus spongiosum:  underneath corpora cavernosa, contains spongy (penile) urethra

 

3)  glans: enlarged tip of penis
* has corpus spongiosum only

–  erection:  penis becoming “rigid”

–  ejaculation:  expulsion of semen from penis

Which structure is responsible for producting a portion of seminal fluid?

a. bulbourethral gland

b. ductus deferens

c. epididymis

d. corpus cavernosum

e. glans

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