Biology Today — January 2018

(Jacob Rumans) #1
Semen
Secretion of the male accessory glands, i.e., seminal vesicles, prostate gland and Cowper’s glands and sperms from testes
collectively constitute the semen. The pH of semen varies between 7.35 to 7.50. It is rich in fructose, citric acid, prostaglandins,
clotting proteins and certain enzymes. It is ejected from the penis during ejaculation. A single ejaculation may contain 200-
300 million sperms, of which 60% should have normal shape and size while rest 40% must show vigorous motility for normal
fertility. The fluid part of semen is called seminal plasma. It maintains the viability and motility of sperms and provides proper
pH and ionic strength.

Functions of Male Reproductive System

Spermatogenesis Secretion of male sex hormones

Production of sperms by germinal epithelial
cells of seminiferous tubules.

Hormones, like testosterone, are
produced by Leydig’s cells.

Copulatory organ transfers sperms into
the vagina of female during copulation.

Transfer of sperms

Spermatogenesis


This refers to the formation of haploid functional male gametes (spermatozoa) from the diploid reproductive cells (spermatogonia).
It occurs in the seminiferous tubules of the testes.


Basement membrane

Spermatids

Primordial germ cells
An outer layer called germinal epithelium cells
(2n) divide endlessly by mitosis to produce
more diploid cells called spermatogonium.
Type B spermatogonium
Acts as precursors of sperms.
Primary spermatocyte
Each primary spermatocyte carries out the first
division of meiosis to produce two secondary
spermatocytes (n).

Spermiation
Sperms detach from Sertoli cells and
eventually are carried out of the testis by the
fluid in the centre of the seminiferous tubule.

Type A spermatogonium
Act as stem cells which divide to form additional
spermatogonia.

Each type B spermatogonium actively grows
to a larger primary spermatocyte by obtaining
nourishment from nurse cells.

Secondary spermatocyte (undergoing
2 nd meiotic division)
Each secondary spermatocyte carries out the
second division of meiosis to produce two
spermatids (n).

Spermiogenesis or spermateliosis
Spermatids become associated with nurse cells, called Sertoli cells which
help the spermatids to develop and transform into spermatozoa (n). This
is an example of cell differentiation. They are later known as sperms.
Fig.: Cells of seminiferous tubules undergoing spermatogenesis

NOVEMBER 2017
1-i- LEPTOCEPHALUS 2-e- TOTIPOTENCY
3-a- INVOLUCRE 4-j- PERICHONDRIUM
5-b- PHYTOALEXINS 6-g- ISCHAEMIA
7-f- MALACOPHILY 8-d- DIAPHRAGM
9-h- CYCLOSPORIN 10-c- NOSEMA
Winners : Ananda Lekshmi T (Vellore), Kelvin Joseph (Mumbai), Meenakshi Sharma
(Himachal Pradesh), Anchitha Palleri (Kerala), Manisha Singh (Varanasi)


  1. Prabhukalyan Mohapatra

    • Bhubaneshwar



  2. Tanvi Salins - Udupi, Karnataka


November-2017


Winners

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