Biology [2 Mark Question Answer]

A- Muscular wall of uterus,
B - Oviduct,
C - Ovary,
D – Vagina

1 - umbilical cord,
2 - placenta,
3 - amnion,
4 - mouth of uterus,
5 - muscular wall of uterus

Accessory glands:

• Seminal vesicle - Seminal fluid
• Prostate gland - Alkaline secretion
• Bulbo-urethral gland - Lubricant

A - ovum
B - sperm

If fertilization fails to take place, the endometrial lining of the uterus starts shedding on the 28th day of the menstrual cycle. Finally it is discharged out along with the unfertilised ovum as the menstrual flow.

Oestrogen secreted by the corpus luteum secrets oestrogen. Oestrogen stimulates the thickening of the endometrial wall of the uterus. The uterine wall becomes thickened and is supplied with a lot of blood to receive the fertilized egg.

The accessory reproductive organs include all those structures which help in the transfer and meeting of two kinds of sex cells leading to fertilization and growth and development of egg up to the birth of the baby. For example: uterus in females, penis in males.

Placenta:
Placenta is formed by two sets of minute finger like processes called the villi. One set of villi is from the uterine wall and the other set is from the allantois. Oxygen and amino acids. Progesterone and oestrogen.

Foetus:
It is contained in the uterus.
In foetus, limbs have appeared and resembles the humans unlike the embryo which is a growing or dividing zygote.

Hymen is a thin membrane that partially covers the opening of vagina in young females whereas clitoris is a small erectile structure located in the uppermost angle of vulva in front of the urethral opening.

Cowper's gland opens into urethra in human males and its secretion serves as a lubricant whereas the prostate gland surrounds the urethra in males and its alkaline secretion neutralizes acid in female's vagina.

Changes in human male:
1. Development of Beard and moustache
2. Voice becomes deeper Changes in human female:
1. Development of Breasts in females
2. Development of high pitched voice

Testosterone is the male reproductive hormone produced by the interstitial cells or the Leydig cells. These cells are located in the testes. They serve as a packing tissue between the coils of the seminiferous tubules. Therefore, it can be said that the testes produce the male hormone testosterone.

Placenta:
The placenta allows the diffusion of oxygen and nutrients such as glucose, vitamins and amino acids from mother to foetus.
Similarly, it also allows the diffusion of carbon dioxide, urea and waste products from foetus to mother.
Placenta also acts as an endocrine tissue. It secretes oestrogen and progesterone.

Amnion: Amnion contains the amniotic fluid which surrounds the embryo.
This fluid protects the embryo from physical damage.
It maintains even pressure all around the embryo.
It also prevents sticking of foetus to amnion.

Identical twins are produced from one ovum i.e. one developing zygote splits and grows into two foetuses whereas fraternal twins are produced when two ova get fertilized at a time.

Sperm is the male gamete produced by the testes. Semen on the other hand is the mixture of sperms and alkaline secretions from the seminal vesicle, prostate gland and Cowper's gland.

Semen : Fluid that contains sperm and secretions from the male reproductive organs. It nourishes and transports sperm during ejaculation.

Parturition or birth : It is the expelling of the foetus from the body of the mother. It begins by the contraction of the uterine walls resulting in labor pains.

Foetus: Foetus is a fertilised zygote that gets implanted in the endometrial lining of the uterus after undergoing cell division.

Gametogenesis: Gametogenesis is a process by which gametes (sex cells) are produced through meiosis. Formation of sperms in testes is called spermatogenesis and formation of ova in ovary is called oognesis.

Graafian follicle : This is a fluid-filled sac in the ovaries that contains an immature egg (oocyte). During the menstrual cycle, the follicle matures, and the egg is released in the process known as ovulation.

Secondary sexual characters: These are features that distinguish the two sexes of a species, but are not directly part of the reproductive system, develop at the time of puberty due to hormonal activity. In a female, there is development of breasts and change in body shape and size of hips. In a male, there is development of a beard and moustache and deepening of the voice.

Androgens : These are the male sex hormones such as testosterone, that have been produced by the interstitial cells of the testes. The androgens are essential for the maturation of sex organs, development of the sperm and for promoting secondary sexual characters.

Scrotum: A sac of skin and muscle that houses the testes in males. It acts to regulate the temperature of the testes, which is essential for sperm production.

Cowper's gland : Also known as Bulbourethral glands, these are small glands located on the sides of the urethra in males. They secrete a clear fluid that lubricates and neutralises any acidic urine in the urethra during sexual arousal.

Penis : The penis is a muscular and highly vascular copulatory organ composed of erectile tissue which serves to deposit the semen of the male into the vagina of the female during copulation or mating and also serves for purpose excretion of urine in males.

Vas deferens: The vas deferens also known as the sperm duct, is a duct which receives the sperms from the epididymis and passes it to the urethra after receiving the secretions from the seminal vesicles, prostate gland and Cowper's gland at the time of ejaculation.