Lecture 10 - Male Reproductive System: Physiology of Male Reproduction | Animal Physiology and Functional Histology- I - MBBS PDF Download

 Page 1


Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
 
 
 
 
 
 
Lesson: Male Reproductive System:   
Physiology of Male Reproduction 
Lesson Developer: Dr. Gayatri Prakash 
College/ Department: Department of Zoology, 
 Daulat Ram College, University of Delhi 
 
 
  
 
 
 
 
Page 2


Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
 
 
 
 
 
 
Lesson: Male Reproductive System:   
Physiology of Male Reproduction 
Lesson Developer: Dr. Gayatri Prakash 
College/ Department: Department of Zoology, 
 Daulat Ram College, University of Delhi 
 
 
  
 
 
 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
1 
 
Table of Contents 
? Introduction 
? Maturation of spermatozoa 
? Morphological Changes 
? Physiological and Biochemical Changes 
?  Biochemistry of semen 
? Composition of semen  
? Chemical Constituents of semen   
? Coagulation of Semen 
? Physiological Significance of the Seminal Plasma Scrotum 
? Summary  
? Glossary 
? Exercises 
? References  
 
 
 
 
 
 
 
 
 
 
 
Page 3


Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
 
 
 
 
 
 
Lesson: Male Reproductive System:   
Physiology of Male Reproduction 
Lesson Developer: Dr. Gayatri Prakash 
College/ Department: Department of Zoology, 
 Daulat Ram College, University of Delhi 
 
 
  
 
 
 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
1 
 
Table of Contents 
? Introduction 
? Maturation of spermatozoa 
? Morphological Changes 
? Physiological and Biochemical Changes 
?  Biochemistry of semen 
? Composition of semen  
? Chemical Constituents of semen   
? Coagulation of Semen 
? Physiological Significance of the Seminal Plasma Scrotum 
? Summary  
? Glossary 
? Exercises 
? References  
 
 
 
 
 
 
 
 
 
 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
2 
 
Introduction 
The transport of spermatozoa from the testis to the site of fertilization is indeed quite a 
journey.  After leaving the testis spermatozoa pass via the rete testis into the epididymis.  
The contents of the epididymis consist of large numbers of spermatozoa suspended in the 
secretions of testis and of epididymis.  This mixture moves slowly down the tube and takes 
many days to reach the vas deferens and then urethra (Figure 1).   Some of the suspending 
fluid is absorbed in the epididymis so that the mixture becomes somewhat concentrated by 
the time it reaches the end of the epididymis.  Also the concentration of spermatozoa 
becomes remarkably dense in the vas deferens. In urethra, the secretions of all the 
accessory glands of reproduction combine with the spermatozoa to produce a mixture called 
semen. The spermatozoa make up less than one-tenth of the total volume of semen and 
the bulk of the semen is contributed by the seminal vesicles, with smaller contributions from 
the prostate and the Cowper’s glands.  The journey through the epididymis helps the 
spermatozoa to acquire characteristic motility and fertilizing ability required for fertilization.  
Various biochemical constituents present in seminal plasma performs many other functions 
such as supplies energy for motility of spermatozoa, contribute to the viability of 
spermatozoa in the vagina, and help  spermatozoa to reach the fertilization site in the 
female reproductive tract thus increasing the probability of fertilization. Functions of the two 
components of the male reproductive system that is its ducts and accessory glands are 
given as: 
A. Maturation of spermatozoa, 
B. Biochemistry of semen 
C. Coagulation of Semen 
D.  Physiological Significance of the Seminal Plasma. 
 
Page 4


Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
 
 
 
 
 
 
Lesson: Male Reproductive System:   
Physiology of Male Reproduction 
Lesson Developer: Dr. Gayatri Prakash 
College/ Department: Department of Zoology, 
 Daulat Ram College, University of Delhi 
 
 
  
 
 
 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
1 
 
Table of Contents 
? Introduction 
? Maturation of spermatozoa 
? Morphological Changes 
? Physiological and Biochemical Changes 
?  Biochemistry of semen 
? Composition of semen  
? Chemical Constituents of semen   
? Coagulation of Semen 
? Physiological Significance of the Seminal Plasma Scrotum 
? Summary  
? Glossary 
? Exercises 
? References  
 
 
 
 
 
 
 
 
 
 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
2 
 
Introduction 
The transport of spermatozoa from the testis to the site of fertilization is indeed quite a 
journey.  After leaving the testis spermatozoa pass via the rete testis into the epididymis.  
The contents of the epididymis consist of large numbers of spermatozoa suspended in the 
secretions of testis and of epididymis.  This mixture moves slowly down the tube and takes 
many days to reach the vas deferens and then urethra (Figure 1).   Some of the suspending 
fluid is absorbed in the epididymis so that the mixture becomes somewhat concentrated by 
the time it reaches the end of the epididymis.  Also the concentration of spermatozoa 
becomes remarkably dense in the vas deferens. In urethra, the secretions of all the 
accessory glands of reproduction combine with the spermatozoa to produce a mixture called 
semen. The spermatozoa make up less than one-tenth of the total volume of semen and 
the bulk of the semen is contributed by the seminal vesicles, with smaller contributions from 
the prostate and the Cowper’s glands.  The journey through the epididymis helps the 
spermatozoa to acquire characteristic motility and fertilizing ability required for fertilization.  
Various biochemical constituents present in seminal plasma performs many other functions 
such as supplies energy for motility of spermatozoa, contribute to the viability of 
spermatozoa in the vagina, and help  spermatozoa to reach the fertilization site in the 
female reproductive tract thus increasing the probability of fertilization. Functions of the two 
components of the male reproductive system that is its ducts and accessory glands are 
given as: 
A. Maturation of spermatozoa, 
B. Biochemistry of semen 
C. Coagulation of Semen 
D.  Physiological Significance of the Seminal Plasma. 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
3 
 
Figure 1: Reproductive system of Man in sagittal view, testis and 
epididymis, are enlarged in comparison to other parts to show 
structural details. 
Source: Author 
A. Maturation of Spermatozoa 
When the spermatozoa leave the testis they are neither structurally nor functionally 
complete to perform their function. The testicular spermatozoa are incapable of fertilizing an 
ovum.  They do not show forward pattern of motility, which is a prerequisite in fertilization 
process.  The Spermatozoa undergo several changes as they move through the epididymis 
which render spermatozoa to acquire characteristic pattern of forward motility and full 
fertilizing ability.   
The epididymis provides a favorable internal milieu to spermatozoa in acquiring fertilizing 
ability and also for their storage until they are ejaculated or move down to the vas deferens.  
The duration for normal transport of spermatozoa through the epididymis is species 
dependent. It varies from 15 days in rat, 8 days in mouse, 14-18 days in guinea pig, 4-7 
Page 5


Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
 
 
 
 
 
 
Lesson: Male Reproductive System:   
Physiology of Male Reproduction 
Lesson Developer: Dr. Gayatri Prakash 
College/ Department: Department of Zoology, 
 Daulat Ram College, University of Delhi 
 
 
  
 
 
 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
1 
 
Table of Contents 
? Introduction 
? Maturation of spermatozoa 
? Morphological Changes 
? Physiological and Biochemical Changes 
?  Biochemistry of semen 
? Composition of semen  
? Chemical Constituents of semen   
? Coagulation of Semen 
? Physiological Significance of the Seminal Plasma Scrotum 
? Summary  
? Glossary 
? Exercises 
? References  
 
 
 
 
 
 
 
 
 
 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
2 
 
Introduction 
The transport of spermatozoa from the testis to the site of fertilization is indeed quite a 
journey.  After leaving the testis spermatozoa pass via the rete testis into the epididymis.  
The contents of the epididymis consist of large numbers of spermatozoa suspended in the 
secretions of testis and of epididymis.  This mixture moves slowly down the tube and takes 
many days to reach the vas deferens and then urethra (Figure 1).   Some of the suspending 
fluid is absorbed in the epididymis so that the mixture becomes somewhat concentrated by 
the time it reaches the end of the epididymis.  Also the concentration of spermatozoa 
becomes remarkably dense in the vas deferens. In urethra, the secretions of all the 
accessory glands of reproduction combine with the spermatozoa to produce a mixture called 
semen. The spermatozoa make up less than one-tenth of the total volume of semen and 
the bulk of the semen is contributed by the seminal vesicles, with smaller contributions from 
the prostate and the Cowper’s glands.  The journey through the epididymis helps the 
spermatozoa to acquire characteristic motility and fertilizing ability required for fertilization.  
Various biochemical constituents present in seminal plasma performs many other functions 
such as supplies energy for motility of spermatozoa, contribute to the viability of 
spermatozoa in the vagina, and help  spermatozoa to reach the fertilization site in the 
female reproductive tract thus increasing the probability of fertilization. Functions of the two 
components of the male reproductive system that is its ducts and accessory glands are 
given as: 
A. Maturation of spermatozoa, 
B. Biochemistry of semen 
C. Coagulation of Semen 
D.  Physiological Significance of the Seminal Plasma. 
 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
3 
 
Figure 1: Reproductive system of Man in sagittal view, testis and 
epididymis, are enlarged in comparison to other parts to show 
structural details. 
Source: Author 
A. Maturation of Spermatozoa 
When the spermatozoa leave the testis they are neither structurally nor functionally 
complete to perform their function. The testicular spermatozoa are incapable of fertilizing an 
ovum.  They do not show forward pattern of motility, which is a prerequisite in fertilization 
process.  The Spermatozoa undergo several changes as they move through the epididymis 
which render spermatozoa to acquire characteristic pattern of forward motility and full 
fertilizing ability.   
The epididymis provides a favorable internal milieu to spermatozoa in acquiring fertilizing 
ability and also for their storage until they are ejaculated or move down to the vas deferens.  
The duration for normal transport of spermatozoa through the epididymis is species 
dependent. It varies from 15 days in rat, 8 days in mouse, 14-18 days in guinea pig, 4-7 
Male Reproductive System: Physiology of Male Reproduction 
 
              Institute of Life Long Learning, University of Delhi  
 
4 
days in rabbit, 9-14 days in ram and 19-23 days in man.  During their transit through the 
epididymis the spermatozoa undergo a series of changes that are collectively called as 
maturational changes.   
Intrinsic factors alone are not sufficient for sperm maturation to occur, and the 
epididymal environment plays a decisive role in this process.  A period of retention in the 
epididymal canal seems to be a pre-requisite for the culmination of maturational changes in 
the spermatozoa. Spermatozoa acquire their full fertilizing ability gradually as they are 
transported from the caput to the cauda epididymides.  Orgebin and Crist have shown that 
in rat only 8 % of ova exposed to sperm suspensions from the caput epididymides were 
fertilized while spermatozoa from the cauda epididymides could fertilize 93 % of the ova.  
However, the exact region of the epididymis where maturation of spermatozoa occurs or is 
completed is variable in different species.   In rat, majority of spermatozoa attains fertilizing 
ability on reaching the cauda epididymides while in rabbit and hamster maturation of 
spermatozoa occurs in the lower half of the corpus epididymides and the proximal segment 
of the cauda epididymides respectively.  Changes in the spermatozoa during their 
maturation process can be classified as morphological, physiological and biochemical. 
 
1. Morphological Changes 
i) Migration and loss of the cytoplasmic droplet: The most noticeable morphological 
change that takes place, as spermatozoa progress through the epididymis is the migration 
of the cytoplasmic droplet that surrounds the connecting piece and first part of the middle 
piece.  The cytoplasmic droplet is gradually displaced caudally and is eventually discarded.   
ii) Structural changes or remodeling of the acrosome: The other well-documented 
morphological change during maturation of spermatozoa is the alteration in the shape and 
dimensions of the acrosome.  Size of the acrosome reduces and its remodeling (alteration of 
shape) occurs during epididymal transit of spermatozoa through the epididymis.   
iii) Establishment of disulfide linkages: Establishment of disulfide linkages appears to 
be an important event in the development of the fertilizing capacity of spermatozoa.  This 
was first revealed by reductive or oxidative cleavage of –s-s- (disulfide) linkages in the head 
of bovine spermatozoa.  It was noticed that spermatozoa of infertile animals stained either 
more or less intensely than normal spermatozoa.   A correlation was found between 
abnormal nuclear morphology and infertility in human spermatozoa.   
2. Physiological and Biochemical Changes