22.0, 23.0 MALE REPRODUCTION
Reproduction I: Testis
Upon completion of this lecture, students will be able to:
a) Define and use properly the following words: Testis, Tunica Albuginea, Connective
tissue septa, Seminiferous tubules, Peritubular (myoid) cells, Interstitial tissue,
Seminiferous tubule, Seminiferous epithelium, Sertoli Cell, Blood testis barrier, Germ
cells, Spermatogonia, Syncytium, Spermatocytes, Meiosis, Round Spermatids,
Elongated spermatids, Spermatozoa, Spermiation, Interstitial or Leydig cell, Lipid
droplets, Cholesterol, Steroid biosynthesis, Spermatogenesis wave, Stages of
spermatogenesis, Acrosome, Sperm flagella, Sperm head, Sperm tail.
b) Describe and associate basic structure/function for the following: all structures listed
above.
c) Identify by microscopy: Acrosome, blood-testis barrier, Elongated spermatids, germinal
cells, Interstitial tissue, Leydig cells (Interstitial cells), Meiosis, mitosis, nucleolus,
peritubular (myoid) cells, Round spermatids, Seminiferous tubules, septa, Sertoli
(sustentacular) cell, sperm flagella, sperm head, sperm tail, Spermatids, Spermatocytes,
Spermatogenic cells, Spermatogonia, Spermatozoa, Tunica Albuginea.
Reproduction II: Male tract
Upon completion of this lecture, students will be able to:
a) Define and use properly the following words: Excretory Ducts, Rete testis, Mediastinum
rete testis, Efferent ductules, Ciliated, Nonciliated, Estrogen receptors, Epididymis, head
(caput), body (corpus), tail (cauda), Pseudostratified columnar epithelium, Principal cells,
Long microvilli (stereocilia), Apical cells, Clear cells, Basal cells, Ductus deferens,
Ampullary gland, Seminal vesicle, Prostate, Central urethra, Benign prostate
hyperplasia, Bulbourethral glands, Cowper’s glands, Tubuloalveolar glands, Penis,
Tunica albuginea, Corpus cavernosa penis, Corpus spongiosum, Erectile tissue, Os
penis, Fibrocartilaginous, Prepuce.
b) Describe and associate basic structure/function for the following: 1) all structures listed
above; 2) the path of sperm from testis to ejaculate.
c) Identify by microscopy: Basal cells, blood sinuses, Bulbourethral gland, Caput (head),
Cauda (tail), central urethra, Clear cells, Corpus cavernosa penis, corpus cavernosa
urethra, Corpus spongiosum, Ductus deferens, Efferent ductules, Epididymis, erectile
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tissue, Mediastinum rete testis, Motile cilia, mucosal folding, Os penis, Penis, Prostate
gland, Rete testis, Seminal Vesicle (vesicular gland), stereocilia, tunica albuginea,
tubuloalveolar gland.
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MALE REPRODUCTION-TESTIS
I.
HISTOLOGICAL STRUCTURE OF THE TESTIS
A. Connective tissue components
1. Tunica Albuginea
a. Tough fibrous CT capsule.
b. Protects the testis.
2. Connective tissue septa
a. Radiate off from the tunica albuginea and partition the testis into lobules.
b. Consist of fibroblasts, collagen, etc.
B. Seminiferous tubules
1. Surrounded by Peritubular cells and basement membrane
a. Flattened and attached to the periphery of the tubule
b. These peritubular (myoid) cells contract
c. Help to move the contents of the tubule toward rete testis
d. Like the basket cell in the salivary gland in terms of appearance and
function.
e. Basal lamina goes around the periphery of the tubule.
2. Complex stratified epithelial
a. The cells are not homogeneous.
b. Types of cells found there.
i. Sertoli (sustentacular) cell (Somatic)
ii. Spermatogenic cells (germinal cells)
3. Interstitial tissue (‘space’ between the tubules).
a. Blood vessels.
b. Lymphatics and nerves
c. Leydig cells (Interstitial cells).
i. Endocrine role
ii. Produce testosterone and other androgens.
iii. Responsible for spermatogenesis, puberty, affect accessory sex
organs, body composition, brain development, and behavior
iv. Acidophilic and polyhedral shape.
d. Other cells
i. Macrophages (most important)
e. Species differences
i. Dogs, cats, bulls, sheep, large mammals
a. Much more connective tissues fibers in interstitial space
b. Can slice with a knife blade
ii. Rodents
a. Very little connective tissue fibers
b. Cannot cut even with razor blade; like spaghetti
II.
SEMINIFEROUS TUBULE
A. Sertoli Cells.
1. Structure and Location
a. Lie on the basal lamina.
b. Cytoplasm extends to the lumen
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c. very thin cytoplasm surrounds germ cells
d. difficult to see with light microscopy
e. To identify them:
i. Large pale staining nuclei (euchromatic)
ii. located near the basal lamina
iii. Nucleus is ovoid to triangular in appearance
iv. Nucleolus is prominent; often seen as tripartite (3 parts)
f. Form the blood testis barrier
i. Tight junction between sertoli cells
2. Function of the Sertoli cells
a. Mechanically support the germ cells. Form the framework of the
seminiferous epithelium
b. Form the blood-testis barrier
i. Helps to provide immune privilege for germ cells
c. Sustentacular, nurturing, ‘Mother’ cell
i. Provide nutrients to the germ cells.
ii. The germ cells receive nutrients from Sertoli cells until they are
released into the real world.
d. Control the movement of the germ cells throughout the epithelium and the
developmental process.
i. Synchronizes clonal development of germ cells
e. Determine the ultimate size of testis
i. Divide only during development and prepubertal
ii. Support a finite number of germ cells
f. Endocrine role
i. produce Mullarian Inhibiting Substance
ii. during development, makes female structures go away
iii. Make some estrogen and testosterone before puberty
3. Clinical significance
a. Dogs can get Sertoli cell tumors (developmental problem)
B. Germ cells
1. Spermatogonia
a. Small darker staining cells.
b. Closest to the basement membrane.
c. Gives rise to all other cell types
d. Stem cells and committed cells
e. Divide by MITOSIS
f. Form syncytium
i. Incomplete cytokinesis during mitosis
ii. Cytoplasm does not split
iii. Cells all connected in one clone
2. Spermatocytes
a. More central in the seminiferous epithelium
b. Largest cell in the seminiferous epithelium
c. Large, intensely stained nucleus (unlike the Sertoli cell).
d. easily identifiable heterochromatin.
e. Divide by MEIOSIS
i. Duplicate chromosomes; become 4N
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ii. Reduction division to form 1N spermatids (1/2 chromosomes in
somatic cells)
f. Found in every seminiferous tubule cross section
3. Round Spermatids
a. Round and small compared to the spermatocytes.
b. Forms acrosome cap over nucleus
c. Grows tail (flagella)
4. Elongated spermatids
a. Closest to the lumen
b. Begin when nucleus changes shape and elongates
c. Chromatin begins to condense and stain more intensely
5. Spermatozoa
a. Most specialized germ cell
b. Highly packed DNA with a tail (flagella)
6. Clinical significance
a. Dogs get seminomas (germ cell tumors)
b. Probably developmental problem or exposure to environmental toxicants
that act like estrogens
7. Species differences
a. Rodents have lancet shaped sperm heads
b. Large mammals have spatula shaped sperm heads
III.
INTERSTITIAL OR LEYDIG CELL
A. Structure
1. Foamy like cells between seminiferous tubules
2. Large round nucleus, similar to plasma cell
3. Lipid droplets common
a. Storage of cholesterol for steroid biosynthesis
4. Species differences
a. Pig has large number of Leydig cells and they are filled with lipid
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IV.
BASIC FEATURES OF SPERMATOGENESIS
A. Prepubertal period
1. No spermatogonia, but Sertoli cells and early germ cells present
2. spermatogenesis only in the adult after testosterone production
B. Spermatogenesis proceeds in waves
1. Permits continuous production of sperm
2. Results in seminiferous tubules that are in different stages of spermatogenesis
(identified by careful analysis)
C. Stages formed
1. Each species has different number of identifiable stages
a. Rat = 14
b. Dog = 8
D. Primate testis is unique
1. Cross section of tubules contains more than one stage of spermatogenesis
2. Clones are spiraled in the tubules
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MALE REPRODUCTION-TRACT
I.
ANATOMY
A. Excretory Ducts
1. Transport sperm to external environment
2. Reabsorb fluid and modify the secretions
B. Accessory reproductive glands.
1. Ampullary gland
2. Seminal Vesicle (also called the vesicular gland)
3. Prostate
4. Bulbourethral gland.
C. Penis
1. Copulatory organ
2. Involved in both the urinary and reproductive system.
II.
RETE TESTIS
A. Anastomosing series of channels.
B. lined by simple cuboidal to squamous epithelium
C. Species differences
1. Dog, large mammals
a. Mediastinum rete testis; located in center of testis or toward one pole
b. This is important because blockage will cause more problems in rodents
than in larger mammals. But partial blockage in dogs can induce
inflammation that affects spermatogenesis.
2. Rodents
a. Extra-testicular location starting in the tunica albuginea
III.
EFFERENT DUCTULES
A. Structure
1. Small diameter tubules connecting rete testis to epididymis
2. Histologically, see tubules cut in cross section.
3. Embedded in epididymal fat pad
B. Species differences
1. Dog, cats, large mammals
a. 10-20 ductules; few merge
b. multiple entry sites into epididymis
2. Rodents
a. 2-8 ductules
b. all merge into a single smaller duct
c. single entrance into epididymis
C. Epithelium
1. simple columnar and of two types
2. Ciliated
a. Motile cilia
b. Stir fluids for homogeneous resorption
3. Nonciliated
a. Microvillus brush border
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b. Endocytotic apparatus
c. Abundance of lysosomal granules
d. Estrogen receptors
D. Function
1. 80-90% of the fluid from the testes is reabsorbed
2. concentrates sperm before it enters epididymis
3. ion channels, ion pumps, water channels
IV.
EPIDIDYMIS
A. Structure
1. It is one long coiled structure
2. many tubules in cross-section.
3. Different regions have different histological appearance.
4. Regions include
a. head (caput),
b. body (corpus),
c. tail (cauda)
B. Epithelium
1. Pseudostratified columnar epithelium
2. Principal cells with long microvilli (stereocilia)
a. Nonmotile cilia
b. Highly resorptive
3. Apical cells
a. Ion transporting
4. Clear cells
a. Phagocytotic
b. Found only in body and tail of some species
5. Basal cells
a. Small lymphocyte appearing
C. Submucosa
1. Peritubular smooth muscle cell
2. Abundant connective tissue between ducts
D. Function.
1. Sperm maturation, storage, and transport
2. Secretions add proteins and lipids to sperm membrane
3. By the time sperm leave the epididymis, they become capable of fertilizing the
egg
V.
DUCTUS DEFERENS AND AMPULLARY GLAND
A. Receives sperm from the epididymis
B. Transports into the ejaculatory duct and penis
C. Similar histologically to the epididymis.
1. lined by a pseudostratified columnar epithelium.
2. beginning portion will have short microvilli
D. abundance of smooth muscle arranged in different orientations
E. primarily for storage
F. Ampullary gland
1. In the distal portion in some species (dog, stallion, and bull, birds)
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2. dilatation of the distal portion of the ductus deferens
VI.
SEMINAL VESICLE
A. Structure
1. a dilated highly folded sac.
2. In histological sections, due to the mucosal folding, looks like a lot of ducts cut in
cross section.
3. Glands will be filled with fluid
a. looks similar to thyroid colloid (a look alike)
a. lined by simple columnar epithelium
b. may be pseudostratified columnar epithelium in certain species
c. vacuolations within the seminal fluid (like that seen in colloid)
B. Function
1. an accessory sex organ that adds secretions to the semen
C. How to distinguish seminal vesicle versus thyroid gland
1. The thyroid gland is composed solely of rounded follicles.
2. The seminal vesicles are highly folded and will have mucosal projections
3. Thus, if one is seeing glandular structures that are in many different shapes with
some of the glands having indentations, then one is viewing the seminal vesicles.
VII.
PROSTATE
A. Structure
1. Extensive species variations
2. To identify it, look for the central urethra within the prostate
a. The prostate will form an elaborate network of ducts (epithelial elements)
b. Surrounding the urethra
c. within the connective tissue of the urethra
d. It will be lined by simple columnar (sometimes cuboidal) epithelium
B. Function
1. Adds secretions to the ejaculate.
C. Clinical significance
1. Benign prostate hyperplasia.
a. It is one of the most common diseases in dogs and man.
b. The prostate begins to grow, i.e., there is actually an increase in the
number of cells (hyperplasia).
c. This proliferation of epithelium and associated connective tissue elements
is not cancerous.
d. Since the prostate surrounds the urethra, this benign growth results in
the prostatic tissue compressing the urethra, and consequent difficulty in
urinating.
e. The treatment in dogs is castration (this option is not so popular in
humans!) because these growths are hormone (androgen) dependent.
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VIII.
A.
B.
C.
D.
E.
IX.
BULBOURETHRAL GLANDS
Also called Cowper’s glands
Pea-sized structures with tubuloalveolar glands
lined by simple columnar epithelium with basal nuclei
glands produce a clear, mucus secretion into the urethra
lubricates the urethra and to neutralize any acidity
PENIS
A. Structure.
1. Tunica albuginea is the white matter connective tissue covering similar to the testis
B. Tissue
1. Corpus cavernosa penis paired.
a. Caverns where the blood can go when the penis becomes erect
b. It is located dorsally.
c. The two cavernosa usually are individual entities but may appear as
adjoining structures in some histological sections.
2. Corpus spongiosum.
a. Body through which the urethra runs through in the center
b. It is located ventrally.
c. It is composed of an abundance of erectile tissue
d. blood sinuses are usually not engorged but when the penis is erect the
blood sinuses become engorged.
C. Function
1. The penis is involved in copulation.
2. Also functions in urination
D. Species differences
1. Dog
a. Os penis
i. Connective tissue septum continues cranially as os penis
ii. Fibrocartilaginous tip
iii. Surrounded by the corpus spongiosum
2. Cat
a. Small os penis
3. Horse
a. No os penis, but more elastic fibers and smooth muscle in cavernosum
4. Boar
a. Corkscrew appearance of the cranial 1/3, not os penis
5. Prepuce
a. Differs by species
b. Outside area is typical skin
c. Inside area may have lymphatic nodules
d. Cat has keratinized papillae that are sharp and grab attention
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