Insights of Sperm Pathology and Its Association with Infertility

*Mohd Sajad and Sonu Chand Thakur*

## **Abstract**

This section considers the structural characteristics of spermatozoon, its assembly, composition, and mechanism behind regulation of their peculiar function. The spermatozoon is tremendously peculiar cell with an arrangement of structural characteristics which furnish it with remarkable capability of carrying the genome of male to the egg. A variety of genes are only expressed in spermatids and result in the formation of proteins that are very crucial and distinctive to spermatozoa. These proteins package the DNA, form the head of sperm, account the component of matrix and enzymes of acrosome, construct the flagellar structure, and work as ion channels that are associated in modulating the motility of sperm and also become adenylyl cyclase which yields cyclic adenosine monophosphate (cAMP) to induce signaling effect which regulates the function of spermatozoon. These proteins are critical essential to sperm and, sometimes, mutation inhibits their synthesis or disrupts their function which leads to male infertility. Researchers are trying to identify those proteins that are significant for proper function of sperm through gene knockout approach in mice that are probable to be necessary in humans as well. However, various questions still persist regarding the spermatozoon composition, organization, and function and need to be answered.

**Keywords:** sperm, spermatogenesis, ROS, infertility, oxidative stress, motility

### **1. Introduction**

Male reproductive function can be divided into three subdivision: (i) hormonal balance of male reproductive function (ii) spermatogenesis, development of sperm; and (iii) fulfill of male sexual act.

Spermatogenesis begins within the seminiferous tubules of testis through the successive mitotic, meiotic and post meiotic phases which results in the formation of spermatozoon, the end product of this process. To expand the spermatogonial population, the germ line stem cell during the mitotic phase undergo a series of division which culminates into two meiotic division and formation of haploid spermatids without the replication of DNA. For the development of male gametes these two phases are very significant. During this phase the remodeling of spermatids occurs extensively into sperm by acrosome formation, condensation of nucleus, development of flagella and loss of cytoplasm. The head and flagellum are the two-substantial component of sperm. These two components are joined together by a connective piece. The head carries the nucleus, cytoskeleton element and cytoplasm. It comprises various types of enzymes homogeneous to

lysosomes of a typical cell, including hyaluronidase (having the ability to digest proteoglycan filaments of tissue) and powerful proteolytic enzymes which can digest proteins having an important role in the process of oocyte fertilization. The flagellum is divided into three regions: mid piece, principle piece and terminal piece. A central complex of microtubules covered by outer dense forms the axoneme. Mitochondria are present in the mid piece which surrounds the outer dense fibers and neighboring axoneme. The principle part of the flagellum is mostly comprised by the existence of fibrous sheath which surrounds the dense fibers and axoneme. In higher vertebrates these dense fibers and fibrous sheath are developed due to internal fertilization and these are cytoskeletal material of sperm flagellum [1]. The plasma membrane as in sperm head surrounds the flagellum tightly and contains scattered cytoplasm. Invertebrate's sperm usually have an acrosome in the head region and mitochondria and an axoneme in the flagellar region but the accessory or additional cytoskeletal elements are absent [2]. To achieve the fertilization the acrosome, have an enzyme which plays a key role to penetrate into egg. The flagellum of the sperm contains the source of energy that generates sperm motility required to reach the egg. All these characteristics of sperm are necessary to deliver the genetic material exists in sperm nucleus to egg. After that, zygote is formed by the fusion of haploid pronuclei of male and female, and thus development initiates. In most mammals, the nucleus of haploid sperm carries the sex chromosome decides the sex of resulting animals [3]. The genome of both maternal and paternal parents is essentially required to proceed the normal development, generally due to distinctive genes imprinting in males and females during gametogenesis [4, 5].

This chapter gives center of attention on the unique features of mammalian spermatozoa with especial consideration to molecules presently known that enrich to the structure and function of sperm. The main topics contemplated are; physiology of male sexual organ, spermatogenesis, sperm count, heritable effect on human sperm structure, regulation of sperm motility, effect of oxidative stress on male reproductive system, sources of reactive oxygen species in seminal plasma, physiological role of ROS in seminal plasma, consequence of Oxidative Stress on male Reproductive System, management and prevention of oxidative stress, correlation between biology of male reproduction and sleep and role of inflammation in infertility.
