Category: Biology Second Paper

The oval or oval part in front of the sperm is called the head. It is covered by a plasma screen. It has such a large nucleus. Nucleus contains 23 chromosomes. At the front of the head is the cap-like acrosome. Acrosome is composed of Golgibodies and filled with hydrolytic enzymes.

Human sperm consists of 4 parts. namely-
1. Head: The oval or oval part in front of the sperm is called the head. It is covered by a plasma screen. It has such a large nucleus. Nucleus contains 23 chromosomes. At the front of the head is the cap-like acrosome. Acrosome is composed of Golgibodies and filled with hydrolytic enzymes.
2. Neck: The narrow and constricted part behind the sperm head is called the neck. It has two centrioles. Proximal centriole and distal centriole.
3. Middle piece: The next widest part of the gribar is called the middle piece. It contains ring centrioles.
4. Tail : The next narrow and long part of the middle section is the tail. There are two centrioles at the front of the tail. Axial filaments arise from a centriole and extend to the tip of the tail. Mitochondria are present along the axial nucleus. The tail is covered by a sheath.

The shape of spermatozoa in animals is species specific. Human sperm are very small, narrow, long and frog-like. It is about 50 microns in length and 2.5 microns in diameter.

(i) Nucleus of spermatid shrinks to form sperm head.
(ii) Acrosome is formed from the glomerulus of spermatid and rests like a cap on the head of the spermatozoa.
(iii) Mitochondria of spermatids form the nucleus of the sperm.
(iv) Centriole of spermatids forms axial filament and tail of sperm.

The process of transformation of spermatids into spermatozoa is called spermiogenesis. Viable and motile sperm are called spermatozoa.

The term spermatogenesis is formed from the Greek words sperma meaning sperm and genesis meaning origin. It means sperm production. The process by which sperm are produced in the testicles of sexually fertile males is called spermatogenesis. Sperm arise from germinal epithelial cells located in the seminiferous tubules. Somatic or Sertli cells provide nutrients to the sperm. Spermatogenesis process takes 60-70 days.

The term spermatogenesis is formed from the Greek words sperma meaning sperm and genesis meaning origin. It means sperm production. The process by which sperm are produced in the testicles of sexually fertile males is called spermatogenesis. Sperm arise from germinal epithelial cells located in the seminiferous tubules. Somatic or Sertli cells provide nutrients to the sperm. Spermatogenesis process takes 60-70 days.
Spermatogenesis is a continuous process. It is described under 4 headings-
1. Multiplication phase: Spermatozoa contain primary germinal cells. Primary germinal cells divide repeatedly to form new cells in the process of mitosis. As a result, the number of cells increases. This is called the numerical growth phase. The resulting cells are called spermatogonia or sperm mother cells.
2. Growth phase: Each spermatogonium grows in size by receiving nutrients. Its nucleus is also enlarged in size. In this condition the cells are called primary spermatocytes.
3. Maturation phase: Primary spermatocytes divide by meiosis to form haploid cells. These are called secondary spermatocytes. Each secondary spermatocyte divides by meiosis to form two spermatids. As a result, 4 spermatids are produced from one primary spermatocyte.
4. Spermiogenesis: The process of transformation of spermatids into spermatozoa is called spermiogenesis. Viable and motile sperm are called spermatozoa. Changes in spermiogenesis are:
(i) Nucleus of spermatid shrinks to form sperm head.
(ii) Acrosome is formed from the glomerulus of spermatid and rests like a cap on the head of the spermatozoa.
(iii) Mitochondria of spermatids form the nucleus of the sperm.
(iv) Centriole of spermatids forms axial filament and tail of sperm.

The word gametogenesis is formed from the Greek words gamos meaning germ cell and genesis meaning origin. It means gamete or gamete formation. Gametogenesis is the process by which gametes or germ cells are produced in sexually fertile individuals. Gametogenesis is of two types. namely-
1. Spermatogenesis
2. oogenesis

In the phase in which blood, mucus, endometrium and unfertilized ovum are destroyed and released into the vagina is called menstruation. If the egg is not fertilized within 36 hours of ovulation, it is destroyed and menstruation occurs. Its shelf life is 4-5 days.

The phase in which the fully formed endometrium contains the blastocyst is called the premenstrual phase. Its shelf life is 15-28 days. During this time progesterone and estrogen hormones are secreted from corpus luteum, nutrients (glycogen, lipids) increase in endometrial cells, endometrium becomes 5-6 mm thick and contains blastocyst.