Biology 242 – Lab
LAB #15
(15th/19 Lab Sessions for Winter Quarter, 2008)
TOPICS TO BE COVERED:
»Male Reproductive System
»Structures of the Male Tubular Reproductive System
»Accessory Glands of the Male Reproductive System »External Genitalia
DESIRED OUTCOMES:
After completing the activities described for this lab session, students should:
»Identify the three portions of the male urethra.
»Identify/describe the series of tubes (ducts) involved in sperm formation and transport.
»Identify/describe the accessory glands: seminal vesicles, prostate gland, Cowper’s glands.
»Trace the formation and transport of semen in the male reproductive tract.
»Describe the contents of the spermatic cord and its anatomical positioning.
»Recognize the layers surrounding each testicle, including the scrotum and its partitions.
»Describe the organization of each testicle and its histology.
»Describe the location and structure of the male external genitalia, including the scrotum,
penis (three masses of erectile tissue), membranous urethra, spongy urethra, and testes.
MATERIALS NEEDED:
»Male pelvic models
»Male Urinary Apparatus model
»Photographic Atlas, Ch.17 and Ch. 10
»Wall Charts
Activity #1: Structures of the Male Reproductive System
All of the organ-systems in the human body studied thus far function in some manner to help maintain homeostasis of the body. The reproductive system is unique, however, in that it plays little role in maintenance of
homeostasis; instead, it functions to perpetuate the species. The main organs of the reproductive systems for
both males and females are the gonads (the testes in males and the ovaries in females), which produce gametes,
(aka: sex cells) for reproduction.
The exercises in this Lab relate to the structures of the male reproductive anatomy.
A generalized statement about the Male Reproductive System is that it is a “tubular system”; that is, it consists of a series of progressively larger and larger “tubes” starting from the microscopic seminiferous tubules in
each testis (where it starts) to the spongy urethra in the penis (where it ends). Along the route of these “tubes”,
there are also several accessory glands of the male reproductive system including the paired seminal vesicles,
the single prostate gland, and the paired bulbourethral glands (aka Cowper’s glands), each of which secretes
fluid that, along with male gametes (spermatozoa) forms semen. Two supporting male reproductive structures
are the scrotum (that houses the testes) and the penis that transfers semen (spermatozoa plus other fluids) into
the female vagina.
Scrotum and Testes: The scrotum (aka scrotal sac) is a pouch of loose skin that is suspended from the root of the
penis outside the abdominopelvic cavity. The scrotum is internally divided into a right and left portion by the
central scrotal septum made up mostly of a reflection of the dartos muscle. The dartos muscle is known as the
“muscle of the scrotum” and it is this thin sheet of smooth muscle that gives the wrinkled appearance to the skin
of the scrotum. When contracted, it also functions to raise the scrotum. The cremaster muscles are continuations of the internal oblique muscles, and are located in the spermatic cords superior to the testes, one on each
side of the inguinal region. The contraction or relaxation of the cremaster muscles occurs when it is cold or hot,
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respectively, to adjust the distance of the testes from the body wall. Being on the exterioer of the body, the scrotum is provided with a cooler temperature, some 2 to 3º C lower than body temperature for normal sperm development.
The testes (testicles or male gonads) are oval-shaped glands that are covered with a white fibrous capsule called
the tunica albuginea. The tunica albuginea is dense fibrous connective tissue that extends into the testis to form
septa, partitions that divide the testis into small compartments called lobules. External to this coat is an extension of the peritoneum called the tunica vaginalis, and spermatic fascia composed of loose connective tissue.
The testes, the gamete-producing organs of the male, are situated outside the body in a sac of skin and connective tissue called the scrotum. (Recall from our study of the Endocrine System, that the testes are endocrine
organs in addition to producing gametes and produce the hormones testosterone and inhibin. The testes lie outside the body because sperm production (spermatogenesis) and maturation will not take place normally at body
temperature; instead these are processes that require a temperature some three full degrees C lower than body
temperature: about 34ºC (or about 94º F).
The testes are surrounded by a connective tissue sheath called the tunica albuginea, which dives into the
interior of the testes to form approximately 250 lobules, each of which contains one to four tightly coiled
seminiferous tubules. These are the sites of spermatogenesis (Although microscopic in size, each seminiferous
tubule is approximately one meter in length if it were straightened out. ) Each seminiferous tubule straightens out just
before converging to form a structure called the rete testis. The rete testis then exits the testis to joing the first
segment of the duct system of the male reproductive tract, the epididmis. The immature sperm migrate to the
epididymis to finish their maturations, and then exit via a long tube called the vas (or ductus) deferens. The vas
deferens travels superiorly through the spermatic cord, a structure that also carries the testicular artery, testicular
veins (the pampiniform plexus), and nerves.
One the vas deferens enters the pelvic cavity, it crosses superiorly and posteriorly over the bladder, where it
joins with a gland called the seminal vesicle and forms the ejaculatory ducts. (There are two of these: both a R
and a L). This duct passes through the prostate gland, where it joins with the prostatic urethra. The prostatis
urethra becomes sthe membranous urethra as it exits the prostate, and then becomes the spongy urethra as it
enters the corpus spongiosum of the penis.
The male reproductive tract consists of three exocrine glands: the prostate, seminal vesicles, and the bulbourethral glands. Both the seminal vesicles and the prostate produce about 90% of the volume of semen, a fluid
that contains chemicals to nourish and activate the sperm. The smaller bulbourethral glands produce an alkaline
secretion that is released prior to the release of sperm during an ejaculation. Because the urethra also transports
urine, the pH in the urethra is generally acidic. The alkaline fluid neutralizes the acid in the urethra, which
would inactivate the sperm.
The penis is composed of three erectile tissue bodies: the single, ventral-lying corpus spongiosum and the
paired, dorsal-lying corpora cavernosa. The corpus spongiosum, which surrounds the spongy urethra, enlarges
distally to form the glans penis. (All three bodies consist of vascular spaces that fill with blood during an erec-tion.)
Be able to identify the following structures of male reproductive anatomy on models and/or diagrams. Most
of these structures you will be able to view in the cat specimens as well. Use Figures 17.3 – 17.5, 17.17, and
17.18 in the Photographic Atlas for help in locating:
1. Scrotum
2. Testes (2)
a. Tunica albuginea
b. Tunica vaginalis
c. Seminiferous tubules
d. Straight tubules
e. Rete testis
f. Efferent ducts
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3. Epididymis (2)
a. Head
b. Body
c. Tail
4. Vas Deferens (aka: Ductus Deferens) (2)
a. Scrotal portion
b. Inguinal portion
c. Abdominal portion
5. Seminal Vesicle (2)
a. Gland
b. Duct
6. Ejaculatory duct (2)
7. Prostate (1)
a. Gland
b. Multiple “ducts” (30 or so “openings”)
8. Bulbourethral glands (aka: Cowper’s glands) (2)
a. Gland
b. Duct
9. Urethra (1)
a. Prostatic urethra
b. Membranous urethra
c. Spongy portion (aka: Penile urethra)
d. External urethral meatus
10. Other structures “along this tubular pathway”:
a. Spermatic cord (2)
1. Testicular arteries
2. Testicular veins (aka: Pampiniform plexus)
3. Nerves and lymphatics
4. Cremaster muscle (continuations of the internal oblique abdominal muscle from when
each testis descended into the scotum via the medial inquinal canal)
b. Penis (1)
1. Corpora cavernosa (2) – dorsally lying masses of erectile tissue
2. Corpus spongiosum (1) – ventrally lying mass of erectile tissue
a. Corona
b. Glans penis
c. Prepuce (aka: “foreskin”) – absent when male is circumcised
Be able to identify these structures on the various models and diagrams used in lab, and to the greatest extent
possible, in the cat when we do dissection of reproductive structures.