Question

Student to attempt either option (A) or (B):
(A) 
(i) Draw a diagrammatic sectional view of human seminiferous tubule (enlarged) and label the following: 
(a) Cell that undergoes spermiogenesis 
(b) Cell that nourish male gametes 
(c) Cell which undergoes meiosis I and meiosis II. 
(ii) State what is seminal plasma. Mention two constituents of seminal plasma. How is it different from semen? 
OR 
(B) 
(i) Mention the event that induces the completion of the meiotic division of the secondary oocyte in humans. 
(ii) Trace the journey of the zygote until its implantation inside the uterus.

Hint:

Sertoli cells support spermatogenesis, seminal plasma nourishes sperm, and the sperm's entry into the secondary oocyte is essential for completing meiosis II and initiating zygote development.

Answer 1

Option (A):
Step 1: The diagrammatic sectional view of a human seminiferous tubule should show: 
(a) Spermatids (undergoing spermiogenesis), 
(b) Sertoli cells (that nourish the male gametes), and 
(c) Primary and secondary spermatocytes (undergoing meiosis I and II). 
Step 2: Seminal plasma is the fluid part of semen secreted by accessory glands (seminal vesicles, prostate gland, and bulbourethral glands). 
Two constituents of seminal plasma are: 
(i) Fructose (provides energy to sperm), and 
(ii) Prostaglandins (aid in sperm motility and uterine contractions). 
Semen is the combination of seminal plasma and spermatozoa (sperms), whereas seminal plasma refers only to the fluid portion. 
OR 
Option (B): 
Step 3: The event that induces the completion of meiotic division of the secondary oocyte is the entry of the sperm into the ovum during fertilization. This triggers the secondary oocyte to complete meiosis II, forming the ovum and a second polar body. 
Step 4: Journey of the zygote: After fertilization in the ampullary region of the fallopian tube, the zygote undergoes repeated mitotic divisions (cleavage) forming a blastomere. It moves through the fallopian tube and becomes a morula, then a blastocyst. The blastocyst reaches the uterus and implants itself in the endometrial lining of the uterine wall, typically around the 7th day post-fertilization.