Draw and describe the male reproductive system. Class 8

The male reproductive system has two parts i.e the reproductive organs and accessory glands. The main organ or male gonad is testis which is present in the scrotum.

(1) Scrotum: The scrotum is a pouch of pigmented skin arising from the lower abdominal wall. Scrotum protects the testes and acts as thermoregulator.

(2) Testes: Testes are primary sex organs that are extra-abdominal in position. There are about 200 to 300 lobules in each testis which are composed of germinal epithelial cells. Seminiferous tubules consist of spermatogonia (sperm mother cells) and nurse cells or cells of Sertoil. There are interstitial cells or cells of Leydig which secrete the hormone testosterone after puberty.

(3) Vasa efferentia: Vasa efferentia are a pair of ducts starting from the rete testis and entering in the epididymis.

(4) Epldidymis: Epididymis are paired structures showing about 6 m long highly coiled duct situated on the posterior border of each testis. It is differentiated into the following three regions. Caput epididymis which is upper wider head that receives vasa efferentia. The sperms undergo physiological maturation acquiring increased motility and fertilizing capacity. Corpus epididymis which is middle narrower body. Cauda epididymis which is a lower duct or tail. In the tail, sperms remain for short period and then enter the vas deferens.

(5) Vasa deferentia: A pair of tubular structures about 40 cm long arising from cauda epididymis are called vasa deferentia.

(6) Ejaculatory duct: Duct of vas deferens and a duct of seminal vesicle are the ejaculatory ducts. Both ejaculatory ducts open into urethra near the prostate gland. Seminal fluid containing sperms are carried by ejaculatory duct to the urethra.

(7) Urethra: The urethra has three parts, viz., prostatic urethra, membranous urethra and penile urethra. Urethra carries both urine and semen.

(8) Penis: Penis is the copulatory organ used for insemination or deposition of sperms in female genital tract. Through the length of penis passes the urethra.

Accessory sex glands:

(1) Seminal vesicles: The seminal vesicles are two small fibromuscular pouches present on the posterior side of the urinary bladder. They have seminal ducts which join with vas deferens and form ejaculatory ducts. Seminal fluids secreted by seminal vesicle which forms about 60% of the total volume of the semen.

(2) Prostate gland: It secretes prostatic fluid which is about 30% of total volume of semen. The prostatic fluid is a whitish and alkaline liquid. The prostatic secretion neutralizes the acidity of vaginal secretion.

(3) Caliper's glands (Bulbourethral-glands): Situated on either sides of membranous urethra are pea-sized Cowper's glands which secrete an alkaline viscous fluid.

the most common energy conversion is from kinetic energy to potential energy, and then from potential energy to kinetic energy.

later on comes the heat energy, mechanical energy, and other energy conversions.

this energy conversion is so common that we can find it in our day to day lives as well.

- one of the most common energy conversions involves the changing of potential energy to kinetic energy or kinetic energy to potential energy

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.