Tools Add-ons Help Normal textArial 12 B I 3. TOPIC: Sperm and Semen Semen is a

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Tools Add-ons Help Normal textArial 12 B I 3. TOPIC: Sperm and Semen Semen is a mix of sperm (from the testes) and secretions (produced by accessory glands). A. Describe what happens to a sperm cell during each of the 2 steps in sperm maturation and development: Spermatogenesis Spermiogenesis B. At about what age does a man start producing mature sperm cells? At what age does sperm cell production stop? C. For each of the 3 male accessory glands, provide the following information: Name of the gland Structural features (size, shape, location)

Explanation / Answer

A.Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. The process begin with mitotic division of the stem cells located close to the basement membrane of the tubules. These cells are known as spermatogonial stem cells. Mitotic division of these produces two types of cells. Type A cells which replenish the stem cells, another is type B cells which differentiate into spermatocytes. Primary spermatocyte divides meiotically (Meiosis I) into two secondary spermatocytes,each secondary spermatocyte divides into two equal haploid spermatids by Meiosis II.Spermatids are transformed into spermatozoa(sperm) by the Spermiogenesis process.These develop into mature spermatozoa, the sperm cells.Therefore , the primary spermatocyte gives rise to two cells, the secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa.

During Spermiogenesis, the spermatids begin to form a tail by growing microtubules on one of the centrioles, which turns into basal body. These microtubules form an axoneme. Later the centriole is modified in the process of centrosome reduction.Anterior part of the tail also called midpiece, thickens the reason is mitochondria are arranged around the axoneme to ensure energy supply. Spermatid DNA also undergoes packaging, becoming highly condensed. The DNA is packaged firstly with specific nuclear basic proteins, which are subsequently replaced with protamines during spermatid elongation. The resultant tightly packed chromatin is transcriptionally inactive. The Golgi apparatus surrounds the now condensed nucleus, becoming the acrosome.

The Maturation then occurs under the influence of testosterone, which removes the remaining unnecessary cytoplasm and organelles. Excess cytoplasm, also known as residual bodies, is phagocytosed by surrounding Sertoli cells in the testes. The remaining spermatozoa are now became mature but immobile , rendering them sterile.Mature spermatozoa are released from the protective Sertoli cells into the lumen of the seminiferous tubule in a process called spermiation.In The non-motile spermatozoa are transported to the epididymis in testicular fluid secreted by the Sertoli cells with the aid of peristaltic contraction. While in the epididymis the spermatozoa gain motility and become capable of fertilization. However, transport of the mature spermatozoa through the remainder of the male reproductive system is achieved via muscle contraction rather than the spermatozoon's recently acquired motility.

B. Male starts producing mature sperm cell in the age of 12 -13 years while this process is slowly get decline from the age of 35 years.

3.The three main accessory male reproductive organs comprises: the seminal vesicles,prostate gland, and the bulbourethral glands.:

Seminal vesicles it is the vesicular glands /seminal glands there are a pair of simple tubular glands posteroinferior to the urinary bladder of males . Vesicles are located within the pelvis. They secrete fluid that partly composes semen.

Prostate gland is walnut shaped gland which located between the bladder and penis. The gland is just in front of the rectum. Urethra runs through the center of the prostate, from the bladder to the penis, letting urine flow out of the body. The prostate secretes fluid that nourishes and protects sperm.

Bulbourethral gland, or the Cowper's Gland, are two pea-shaped glands in the male the gland is located beneath the prostate gland at the starting of the internal portion of the penis,they add fluids to semen during the process of ejaculation.

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