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ASC 309
Endocrinology of the Male and Spermatogenesis
Chapter 10 – Student Outline
Male Endocrine Control/Regulation
o Different than in the female
Endocrine requirements
 1)
 2)
 3)
Male hypothalamus
Release of GnRH
Endocrine Control/Regulation (Figure 10-1)
Burst of GnRH
LH episode time period
FSH concentrations:
Leydig Cells
Luteinizing hormone
Analogous to
Contain:
Cells produce
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Progesterone is converted to:
Response by Leydig cells (Figure 10-3)
o Short, pulsatile secretions of testosterone
Pulsatile discharge of LH
o Leydig cells become refractory
Refractory condition caused by
Marked reduction in progesterone and testosterone secretion
Intratesticular levels of testosterone
FSH
High levels of testosterone
Sertoli cell function
Reduction of testosterone allows negative feedback
Cells also produce estradiol and other estrogens.
•Stallion / boar
Sertoli Cells (Figure 10 -3)
Convert testosterone to:
Role of estradiol
Testosterone, DHT and estradiol exert negative feedback on
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LH and FSH
High estradiol
Cells also produce inhibin
Spermatogenesis (Figure 10-5)
Takes place in the seminiferous tubules
Consists of the sum of all cellular transformations in developing germ cells
–Consist of:
Proliferation phase
Meiotic phase
Differentiation phase (spermiogenesis)
Consists of mitotic divisions involving
Stem cell renewal
Spermatogonia providing a continual renewal of stem cells.
Meiosis involves the following cells:
1)
2)
3)
Morphologic transformation of spermatids to spermatozoa
(spermiogenesis).
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Proliferation (Figure 10-5)
Generates spermatogonia to become more advanced cell types.
–Spermatogonia
Specialized diploid cells (2N) (location)
Undergo several mitotic divisions
Three types of Spermatogonia
1.
2.
3.
Undergo several mitotic divisions progressing from
•Maintain
continual source of:
Meiotic Division (Figure 10-5)
Forms haploid germ cell
Goal:
Mitotic divisions of B-spermatogonia result in the formation of:
1)
2)
3)
Differentiation
Production of self-propelled package of enzymes and DNA
Spherical spermatids must undergo a series of changes
Consists of the following phases:
1.
2.
3.
4.
Golgi phase
Cap phase
Acrosomal phase
Maturation phase
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1. Golgi phase (Figure 10-6)
Characterized by initial development of acrosome
Golgi apparatus
 Proacrosomic vesicles
 Centrioles migrate
Proximal centriole
Distal centriole
2. Cap phase (Figure 10-7)
 Acrosome
 Primitive flagellum
3. Acrosomal phase (Figure 10-7)
 Continues to spread
 Nucleus and cytoplasm
 Manchette extends
 Some of the microtubules of the manchette
4. Maturation phase (Figure 10-9)
 Manchette portions migrate
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 Mitochondria migrate
•Assembled in a helical fashion
•Dense outer fibers of the flagellum and the fibrous sheath
Sperm cells are released into the lumen of the seminiferous tubules.
Spermiation
 Release is referred
Head - Acrosome
 Mammalian spermatozoon has a shape characteristic for each species.
Food producing mammals
Anterior 2/3 is covered
Membrane-bound lysosome that contains hydrolytic enzymes which
include:
1)
2)
3)
4)
5)
Acrosome Reaction
Exocytosis
Tail (Fig. 10-9)
Self-powered flagellum
Composed of:



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
Capitulum
Laminated columns
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Axonemal component
Composed of microtubules
9 pairs around 2 filaments
9 dense pairs
Mitochondrial sheath
Arranged in a helical pattern
Principal piece
Makes up the majority of the tail
Sperm Production (Table 10-2)
Production
Man
Strong correlation between
Measure of scrotal circumference
Circumference-Bull, ram (Figure 10-13)
Width-Stallion, boar
Daily sperm output (DSP)
-Defined as
Spermatogenic efficiency
Relationship between output and Sertoli cells
Spermatozoal Viability
Motility commonly used as an assessment of viability.
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Types of Abnormal Spermatozoa (Figure 10-14)
Defined as any shape characteristic deviating from normal.
Per ejaculate - _____________abnormal considered acceptable.
Reduced fertility may occur when
Abnormalities originate in the testes due to:
Artificial Insemination
 Single most important technology for accelerating genetic improvement
Dairy Cows
Beef cows
Turkeys
Sows
Horses
Other uses
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