Lecture 23: Male Reproductive Anatomy
M/O: Chapter 28
107.With respect to the gross anatomy, identify and describe the anatomy of the male and female
reproductive system, including the gonads, ducts, accessory glands, associated support structures, and
external genitalia.
108.Relate the general stages of meiosis to the specific processes of spermatogenesis and oogenesis.
109.Contrast the process and the final products of spermatogenesis and oogenesis.
110.Explain the role of the sustentacular cells and interstitial cells in sperm production.
111.Describe the pathway of sperm from the seminiferous tubules to the external urethral orifice of the penis.
112.Identify and describe the organs involved in semen production
113.Discuss the relationship between the location of the testes and sperm production.
Development of the reproductive system
Boys and girls begin life with bipotential gonads. It is only if the fetus has a Y chromosome that the bipotential gonad will
differentiate into male gonads, or testes.
1. 6 weeks in utero
A. Both XX and XY fetuses have identical physical features, including 2 sets of tubes and the bipotential gonads.
B. One set of tubes is associated with the developing kidney. The other set is NOT.
C. Dependant on the presence of the Y chromosome, one set of tubes begins to disintegrate, while the other continues
development.
2. 10-12 weeks in utero
A. Y: The tubes that continue development are linked to the testes and are associated with the developing bladder as well.
B. X: The tubes that continue to develop do not make direct contact with the bladder OR the ovaries!
3. Onward:
A. Y: The gubernaculum, a thin band of CT, attaches the testes to the scrotum. As the fetus grows, the gubernaculum doesn’t
change length, so the testes are pulled through the abdomen toward the scrotum. Eventually, it even dehydrates and shortens
(KZR notes), ultimately passing through the inguinal canal into the scrotum.
i. Your text says this is a slow process.
B. External genitalia differentiate by 20 weeks. Because structures originated from the same fetal structures, they are
considered “homologous structures”.
Summary of homologous structures found in male and female reproductive systems
Gonads
Female
Ovaries
Male
Testes
Gametes
Ova
Sperm
External genitalia
Clitoris
Labia majora
Glans of penis
Scrotum
Erectile genitalia
Corpora cavernosa
Vestibular bulb
Corpora cavernosa
Corpus spongiosum
Muscles of the genitalia Ischiocavernosus
Bulbospongiosus
Bio 6: Human Anatomy
Ischiocavernosus
Bulbospongiosus
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Gametogenesis
Gamete formation happens through the process of meiosis. Sperm are formed during spermatogenesis.
1. Spermatogonia are found on the basolateral edge of a seminiferous tubule.
2. Spermatogonia go through mitosis to form primary spermatocytes. These cells are found closer to the lumen of the seminiferous
tubule and they are DIPLOID.
3. Primary spermatocytes go through meiosis I to form secondary spermatocytes.
4. Secondary spermatocytes go through meiosis II to form spermatids.
5. Spermatids do not have a tail...when the tail gets added, they become mature sperm cells (via the process of spermiogenesis!)
6. Sustentacular cells (also called nurse cells!) are found within the seminiferous tubules and they take care of the sperm cells (at
all stages of production).
7. Interstitial cells are found between seminiferous tubules and they produce male hormones (androgens).
Sperm
Once the sperm are formed in the seminiferous tubules, they need to GET OUT! Let’s see how they do it!
1. Sperm are made in the seminiferous tubules which make up the bulk of the testes.
2. They are directed to the epididymis by ciliated epithelium in the efferent ductules.
3. While in the epididymis the sperm learn to swim! (Note: the epididymis is a long coiled tube- 4-5 feet long- that sits on top of
the testes).
4. If ejaculation occurs, the sperm in the epididymis are ejected into the ductus deferens (vas deferens)
5. At the end of the ductus deferens, it empties into the ejaculatory duct.
A. Both ejaculatory ducts empty into the prostatic urethra.
B. The seminal vesicles, which empty into the ejaculatory duct, secrete fructose (so the sperm have lunch on their journey),
bicarbonate (baking soda, so they don’t get fried by the acidic vagina), and prostaglandins (hormone-like chemicals that
open the cervix!)
6. The ejaculatory duct becomes the prostatic urethra when it passes through the prostate gland.
A. The prostate gland secretes citric acid (a delicious food for the journey)
B. It also secretes an antibiotic to keep the urethra healthy
C. It also secretes PSA, which helps liquify the semen once it enters the vagina (so the little fellas can swim).
7. Now the sperm go through the membranous urethra, which passes through the urogenital diaphragm.
A. Here the bulbourethral glands squirt in some mucus, just for fun.
8. FYI: The semen from one ejaculation contains 200-500 MILLION sperm.
The Penis
The penis is the organ of copulation. Otherwise, it would be difficult to make babies. (Though maybe we could do it “squid-style”...
the male squids have a specialized tentacle that they use to grab their own sperm and then put it into the lady squids...)
1. The penis attaches to the body at the root (which apparently consists of both the bulb and the crura (singular: crus) of the penis).
2. Within the shaft of the penis, there are 3 erectile bodies:
A. One corpus spongiosum surrounds the urethra (the spongy urethra) and enters the glans, or head of the penis.
B. Two corpora cavernosa (singular: corpus cavernosum) stay within the shaft of the penis.
C. These guys are spongy, and there is a LOT of space for BLOOD.
D. As the spaces fill with blood, the penis becomes erect and this actually cuts off the blood’s exit route...the blood gets
STUCK in the penis, until “sexual excitement ceases”.
3. Arousal is controlled by the parasympathetic NS...but ejaculation is stimulated by the sympathetic NS. Hmmmm...
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Lab 23: Male Reproductive Anatomy
Reading: M&O Ch. 28, E Ch. 18-1
I. Gross Anatomy
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
scrotum
scrotal raphe
cremaster muscle
scrotal cavity
tunica vaginalis (parietal and visceral layers)
testis
gubernaculum testis
epididymis (head, body, tail)
ductus (vas) deferens
spermatic cord
A. testicular (spermatic) artery and vein (don’t try to find, but know that they’re here)
B. testicular nerve (don’t try to find, but know that it’s here)
C. ductus deferens
D. cremaster muscle
inguinal canal
seminal vesicles
prostate gland
A. prostatic urethra
bulbourethral (Cowper’s) glands
urogenital diaphragm
membranous urethra
penis
A. root
B. body
C. glans
D. prepuce (foreskin)
E. erectile tissue
i. corpora cavernosa
a. crura of penis
b. ischiocavernosus muscle
ii. corpus spongiosum
a. bulbospongiosus muscle
F. penile urethra
G. external urethral meatus (orifice)
II. Histology
Examine the following slide: Spermatogenesis (HM 1-2). Identify all of the following structures:
1. tunica albuginea
2. septa
3. seminiferous tubules
A. supporting (sertoli) cells
B. spermatogonia
C. spermatocytes (primary and secondary)
D. spermatids
4. interstitial cells
5. efferent ductules
Bio 6: Human Anatomy
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Fall 2013: Riggs
External Brain 23: Male Reproduction
107.With respect to the gross anatomy, identify and describe the anatomy of the male and female
reproductive system, including the gonads, ducts, accessory glands, associated support structures, and
external genitalia.
108.Relate the general stages of meiosis to the specific processes of spermatogenesis and oogenesis.
109.Contrast the process and the final products of spermatogenesis and oogenesis.
110.Explain the role of the sustentacular cells and interstitial cells in sperm production.
111.Describe the pathway of sperm from the seminiferous tubules to the external urethral orifice of the penis.
112.Identify and describe the organs involved in semen production
113.Discuss the relationship between the location of the testes and sperm production.
Your Task
Study Questions
1. What is the function of the interstitial cells? Of the Sertoli cells? Of the spermatogonia?
2. Do all seminiferous tubules show the same stage of spermatogenesis at one time?
3. Trace the pathway of a spermatogonium from the seminiferous tubules to the outside world.
4. Which of the above structures carry urine? Which carry sperm? Which carry both?
5. Which of the above structures are secretory? What do they secrete?
Bio 6: Human Anatomy
117
Fall 2013: Riggs