1)Describe the process of spermatogenesis. Also in your essay describe the struc
ID: 3519536 • Letter: 1
Question
1)Describe the process of spermatogenesis. Also in your essay describe the structure of the sperm and the function of each structure. Lastly describe the process of fertilization including how polyspermy is prevented
1)Describe the process of spermatogenesis. Also in your essay describe the structure of the sperm and the function of each structure. Lastly describe the process of fertilization including how polyspermy is prevented
1)Describe the process of spermatogenesis. Also in your essay describe the structure of the sperm and the function of each structure. Lastly describe the process of fertilization including how polyspermy is prevented 1)Describe the process of spermatogenesis. Also in your essay describe the structure of the sperm and the function of each structure. Lastly describe the process of fertilization including how polyspermy is prevented
Explanation / Answer
Spermatogenesis occur in four stages:
i. Stage of proliferation
ii. Stage of growth
iii. Stage of maturation
iv. Stage of transformation
i. Stage of proliferation: Each spermatogonium contains diploid number of chromosomes. In man, there are 23 pairs of chromosomes. One member of each pair is from maternal origin and the other one from paternal origin, The 23 pairs include 22 pairs of autosomal chormosomes and one pair of se_x chrmosomes. The se_x chromosomes are one X chromomsome and one Y chromosome. The spermatogonia near the basement membrane of seminiferoud tubule are larger in size. During the proloferative stage, spermatogonia divide by mitosis without any change in chromosomal number. In man, there are ususally seven generations of spermatogonia, The last generation enters the stage of growth as primary spermatocyte. During this stage, the spermatogonia migrate along with sertoli cells towards the lumen of seminiferous tubule
ii. Stage of growth: In this stage, the primary spermatocyte grows into a large cell. Apart from growth, there is no other change in spermatocyte during this stage
iii. Stage of maturation: After reaching the full size, each primary spermatocyte quickly undergoes meiotic and maturation division, that occurs in two phases:
First phase: In the first phase each primary spermatocyte divides into two secondary spermatocytes. The significance of the first meiotic division is that each secondary spermatocyte receives only the haploid or half the number of chromosomes. 23 chromosomes include 22 autosomes and a X or a Y chromosome
Second phase: During this phase, each secondary spermatocyte undergoes second meiotic divison resulting in two smaller cells called spermatids. Each spermatid has haploid number of chromosomes.
4. Stage of transformation: There is no further division. The spermatids are transformed into matured spermatozoa by means of spermeogenesis and released by seprmination
Spermeogenesis: It is the process by which spermatids become matured spermatozoa. The changes taking place during spermeogenesis are:
a. Condensation of nuclear material
b. Formation of acrosome, mitochondrial spiral filament and tail structures
c. Removal of extraneous cytoplasm
Spermination: Spermination is the process by which the matured sperm cells are released from Sertoli cells into thelumen of seminiferous tubules
Structure of Sperm:
Spermatozoon (Sperm) is the male reproductive cell developed in the testis. The matured sperm is 60 microns long. Each spermatozoon consists of:
1. Head: Head of sperm is oval in shape with a length of 3-5 microns and width of 3microns. The anterior portion of head is thin. The head is formed by a condensed nucleus, a thin cytoplasm and a thin cell membrane. The anterior two thirds of the head is like a thick cap and it is called acrosome (Galea capitis). Acrosome develops from Golgi apparatus and it is made up of mucopolysaccharide and acid phosphatases. It also contains hyaluronidase and proteolytic enzymes which are essential for the sperm to fertilize the ovym
2. Neck: The head is connected to the body by a short neck. It anterior end is formed by thick disc shaped anterior end knob, which is also called proximal centriole. The posterior end is formed by another similar structure known as posterior end knob. It gives rise to the axial filament of the body. Often, the nekc and body of sperm togeher called as midpiece
3. Body: It is cylindrical with a length of 5-9 microns and the thickness of 1 micron. The body of the sperm consists fo a central core called axial filament covered by thin cytoplasmic capsule. The axial filament covered by thin cytoplasmic capsule. The axial filament starts from posterior end knob of the neck. It passes thorugh the body and a perforatead disc called end disc or end ring centriole. Finally the axial filament reaches the tail as axial thread. In the body, the axial filament is surrounded by a closely wound spiral filament consisting of mitochondria
4. Tail: The tail of sperm consists of two segments:
i. The chief or main piece of tail: It is enclosed by cytoplasmic capsule and has an axial thread. It is 40-50 micron long.
ii. The terminal or end piece of tail: It has only the axial filament
Tail is helpful for the motility of sperms towards the ovum in the female genital tract
Process of fertilization: Fertilization refers to the fusion of male and female gametes to form a zygote. Among 200-300 milions of sperms entering the femal genital tract only a few thousand sperms reach the spot near the ovum and among the few thousand sperms only one succeeds in fertilizing the ovum.
During fertilization, the sperm enters the ovum by penetrating the multiple layers of granulosa cells known as corona radiata present around the ovum. It is facililated by hyaluronidase and proteolytic enzymes present in the acrosome of sperm. The proteolytic enzymes from the acrosome of the successful sperm diffuse through the structures of zona pellucida and inactivate the other sperms entering the ovum.
How polyspermy is prevented?
Fusion of the sperm and oocyte cell membranes initiates a wave of intracellular Calcium ions that passes through out the oocyte. THis results in a transient hyperpolarization of the oocyte plasma membrane which may represent a potential block to polyspermy.
The cortical reaction is triggered from the same wave of intracellular Calcium ions which releases hyrolytic and oxudative enzymes from the cortical granules into the perivetielline space killing off surrounding sperm and preventing polyspermy
The zona reaction in which the cortical granules enter the zona pellucida and crosslink with the Zona pellucida with the ZP glycoproteins. This forms a barrier to outside sperm.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.