The testis is primary sex organ in males. Each testis has 250 testicular lobules. Each lobule has 1-3 highly coiled seminiferous tubules. These seminiferous tubules open into vasa efferentia through rete testis. The vasa efferentia opens into epididymis which continues to form vas deferens. 

• The heart is first functional organ to develop and starts to beat and pump blood at around 21 or 22 days in human beings. 
• Cardiac myoblasts and blood islands in splanchnopleuric mesenchyme on each side of  neural plate, give rise to cardiogenic region. 
• This is a horseshoe-shaped area near head of embryo. 
• By day 19, following cell signaling, two strands begin to form as tubes in this region, as a lumen develops within m. 
• These two endocardial tubes grow and by day 21 have migrated towards each or and fused to form a single primitive heart tube,  tubular heart. 
• By end of second month of pregnancy limbs and digits are developed. By end of weeks (first trimester), most of major organ systems are formed. 

The secretion of seminal vesicles constitutes bulk of seminal fluid (semen). It is a thick fluid that contains sugar fructose, proteins, citric acid, inorganic phosphorus, potassium, and prostaglandins.