Human Reproduction class 12th with handwritten notes



By now we all know what reproduction is and how humans reproduce but our knowledge is limited. So today, I'm going to be giving briefs about the chapter Human Reproduction which is in NCERT as well as in state board textbooks. 

I have also attached my in-depth handwritten notes at the end of this article. Do give a look at it. 

Male reproductive system:


The human male reproductive system consist of a pair of testes, accessory ducts, glands and external genitalia. It is situated in the pelvis region. The male reproductive system consist of primary sex organs and the accessory sex organs

Primary sex organs are the ones which are present from birth in the body and accessory sex organs are the ones which develop later after birth. 

The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens. The male accessory glands include paired seminal vesicles, a prostate and paired bulbourethral glands which is also known as the Cowper's gland

The external genitalia or the external structure consist of penis, scrotum and testes. The male reproductive system is specialised for three primary functions, which are as follows:
  • For the production of sperms and to transport it along with nourishing it. 
  • To discharge sperm within the female reproductive tract. 
  • To produce and secrete male sex hormones. 
Each testis includes lobules, these lobules include seminiferous tubules. This seminiferous tubule opens in the vasa efferentia and each tubule is lined by two types of cells - male germ cells and sertoli cells. The region present outside of seminiferous tubules contains Leydig cells or interstitial cells. Testis is connected to the wall of the scrotum by a short fibromuscular band called gubernaculum

The penis is a part of the external genitalia. The penis has an enlarged end which is called the glans penis and this glans penis is covered by a loose fold of skin called the foreskin. The bulbourethral glands helps in lubricating the penis. 

Semen and urine both leave the penis through urethra. Gonads produce gametes and are a part of the endocrine system. 

The growth of secondary characters in males is due to puberty which is attained between 13 to 14 years of age. Puberty is triggered by secretion of the hormone testosterone which plays the key role in maturation and growth of the secondary sex characters.

Disorders of the male reproductive system:

The disorders of the male reproductive system are as follows:

1. Benign Prostate Hypertrophy (BPH):

BPH causes the prostate glands to enlarge. BPH is commonly known as prostate cancer. It often occurs at old age and is common in men. It can be treated surgically or by medications. 

2. Impotence:

This happens when a man is unable to achieve or hold onto an erection for longer during the time of sexual intercourse. 

3. Sterility:

A man is said to be sterile when the sperms cannot fertilise the ovum of the female. This may or may not be associated with impotency. 

Here I have only given a brief explanation about the male reproductive system. If you want a detailed explanation about this topic I have another post you can read. Click here to read that article. 

Female reproductive system:

The female reproductive system is complex yet it is important. To make it easy I'm going to be dividing it into the internal and the external organs so that it will be easier to memorise that way. 




We'll first start by the internal organs of the female reproductive system. Internal organs of the female reproductive system consists of ovaries, fallopian tubes, uterus, cervix and vagina

Ovaries are the primary female sex organ that means it is present at the time of birth in the female body. They are almond shaped and produce the female gamete i.e ovum and also secretes ovarian hormones (oestrogen and progesterone) which controls menstrual cycle and secondary sexual characters in females.

Just like the ovaries produce the female gamete the same way the testes of the male produces the male gametes. Hence, ovaries are said to be homologous to testes. 

The ovaries are located on each side of the lower abdomen. It is connected to the walls of the pelvic and uterus through ligaments. Each ovary is covered by a thin epithelium which includes ovarian stroma. The stroma is divided into two zones - peripheral cortex and inner medulla

Fallopian tubes are also known as oviducts or uterine ducts and they are a part of female accessory ducts. They come out of the periphery of the ovary and they extend towards the uterus. Fallopian tubes divided into three regions which are as follows:
  1. Infundibulum - This is the extended outer end of the fallopian which is a funnel shaped.
  2. Ampulla - This part is present next to infundibulum and is slightly larger in shape. 
  3. Isthmus - This is a short narrow thick walled portion which joins the uterus. 
Uterus is not present in pair but instead it is single in nature and it is also called the womb, where the baby develops. It has a shape like an inverted pear which is supported by ligaments. Uterus opens into vagina through the cervix. The cavity of cervix is called the cervical canal

Uterus is a part of the female accessory ducts and is made of three layers of wall - Perimetrium (external thin layer), myometrium (middle thick layer) and endometrium (inner glandular layer). 

Vagina is a tubular muscular organ which receives the penis during sexual intercourse. The vagina lies between the urinary bladder and the rectum. The internal lining of the vagina is formed by Bartholin's gland which is a glycogen rich muscous membrane and muscous gland. 

Bartholin's gland produces a fluid which maintains the pH and also nourishes the sperms. Vagina is also a part of the female accessory duct and serves as a passage for the entry of sperms, for childbirth and menstrual flow. 

With this we have completed the internal organs of the female reproductive system and now we head onto the external organs. The external organs of the female reproductive system consist of labia majora, labia minora, mons pubis, clitoris, vestibule, hymen, greater vestibular glands and breast. The labia majora, labia minora, mons pubis and the clitoris forms a vulva

Labia majora is a fold of tissue which is fleshy in nature and it extends from mons pubis. It forms the boundary of vulva. It consist of adipose tissue, sebaceous glands, sweat glands is covered by hair. Labia minora is a paired fold of tissues which lies under the labia majora and is the inner lining of the vulva. Hair is absent in labia minora. 

Mons pubis is like a cushion of fatty tissues which covered by skin and pubic hair. It is formed by adipose tissue. Clitoris lies above the junction of labia minora and urethral opening. It is erectile in nature and is made up of cavernous tissue. 

The hymen is a membrane which partially covers the opening of the vagina. Hymen can not only be ruptured during first intercourse but also can be ruptured due to heavy activity sports like cycling, swimming, etc.. So, it is not a reliable source to find out if a female has had sexual activity or not

In some cases the hymen is not present at all from the time of birth that doesn't mean that the female has had many sexual partners and the presence of hymen doesn't indicate that the female has less sexual activity. 

Mammary glands are a paired structure containing glandular tissue and fat. The amount of fat can vary from person to person. They are commonly known as breast. Each glandular tissue in each breast is divided into 15-20 mammary lobes which contains the alveoli cells. These cells secrete milk. 

Each tubules further join to make a mammary duct and these mammary ducts join to form mammary ampulla which is connected to the lactiferous duct which opens in the nipple of the female from where the milk is sucked out by the baby. 

Lactiferous ducts form lactiferous sinuses to store milk in it. The hormones prolactin and oxytocin which is secreted by the pituitary gland controls the release of the milk from the breast.

Puberty in females can be attained between 10 to 14 years of age where the internal reproductive organs reach a stage of maturity. This stage is called menarche which means that its the beginning of the child bearing period. 

With this we have covered the key points of the female reproductive system and let's head onto the functions of the female reproductive system:
  • For the production of the egg in the ovary and this process is called oogenesis
  • To accept the sperms during intercourse. 
  • Providing an environment to carry out the process of fertilization. 
  • Supplying nutrition or nourishment to the baby in prenatal stage (when the baby is in the womb) and postnatal stage (when the baby had been delivered). 
Related articles: Female Reproductive System

Disorders of the female reproductive system:

The disorders of the female reproductive system are as follows:

1. Sterility:

Inability of the female to get pregnant due to lack of quality in a structure or function of the genital organs which are required for the nourishment of the baby. 

2. Menstrual irregularity:

When the menstrual cycle is not regular or is coming in between break then it can be amenorrhea (absence of menstruation), hypermenorrhea (uncontrollable bleeding or continuous bleeding of the uterus) or dysmenorrhea (painful menstruation). 

3. Infertility:

Inability of a female to get pregnant due to failure in production of eggs or due to some anatomical factors that stops the union of the sperm with the ovum. 

Menstrual cycle:

Menstruation is repeated after every 28 to 29 days and there are a lot of events taking place in between this time which is completed when the vagina starts to bleed. This cycle keeps going on every month. Hence, this is called menstrual cycle

Menstrual cycle is a characteristics of the primates. Primates include monkeys, apes and humans. This cycle does not take place in vertebrates but the in some mammals other than primates this cycle is called as oestrous cycle

The females of the other mammals apart from primates permit sexual intercourse only during a particular phase and this particular phase is called the fertile period, oestrous or heat. In primates such a period does not occur. 

Menstruation begins about 15 days after ovulation. Ovulation is when the ovary of the female releases an egg every month as it awaits for fertilization and this ovulation takes place in mid way between two menstrual periods. 

Puberty in females can be attained between 10 to 14 years of age where the internal reproductive organs reach a stage of maturity. This stage is called menarche which means that its the beginning of the child bearing period and it lasts up 40 to 50 years of age. This is called menopause

Every month the female body forms an extra wall which is the endometrial lining in the uterus for pregnancy. When the egg which was released from the ovary does not fertilise it results in the shredding of the wall which results to bleeding. Bleeding can also be caused due to ruptured blood vessels. 

This endometrial wall rebuilds by the help of the Follicle Stimulating Hormone (FSH). The ovum and the follicle matures which secretes increased amount of oestrogen which gives a boost to the growth of the endometrial wall again once the menstrual flow has ended. 

Once the egg is fertilised the menstrual cycle stops and there is no bleeding taking place. A normal cyclic menstrual cycle indicates a normal reproductive phase in females. A menstrual cycle is counted from day 1 of bleeding until the day 1 of bleeding of the next month. 

Phases of menstrual cycle:

Menstrual cycle is divided into 4 phases, which are as follows:

1. Menstrual phase (Bleeding phase):

Menstrual phase is when the vagina starts bleeding due to the shredding of the endometrial lining and ruptured blood vessels. This phase can lasts from 3 to 5 days. This phase only takes place when the egg is not fertilised. 

In this phase, corpus luteum which is a mass of cell in the ovary which has to be sent out with the menstrual flow is replaced by a scar tissue called corpus albicans.

2. Proliferative phase:

This phase is also known as follicular stage of stage of repair and proliferation. In this phase, there is regrowth of the endometrial lining in the uterus and is under the influence of the hormones oestrogen which is secreted by follicular cells. This stage extends from the end of menstrual phase to ovulation

3. Ovulatory phase:

No changes take place during this phase in the endometrium of the uterus. This is the phase where an egg is released form the ovary and is called ovulation. This phase takes place midway in between two menstrual flow. 

While the process of ovulation takes place, the body temperature rises and remains high until the menstrual phase which is the bleeding phase starts. 

4. Secretory phase:

The hormones progesterone and oestrogen which are secreted by corpus luteum takes control over this phase. Hence, this phase is also called as progestational phase or luteal phase. As this phase prepares the endometrium for pregnancy as well as implantation it can also be known as progravid phase     

Down I have created a pie chart showing the duration of each phase in menstrual cycle. 


Fertilization:

Fertilization is a huge topic and this post is already got this long so I have tried my best to at least make you explain what the term fertilization means and the what actually happens in fertilization. 

Fertilization is a process where there is fusion of the two haploid gametes i.e the male haploid gamete and the female haploid gamete. This fusion of both the gametes give rise to a diploid zygote. This process is also known as Syngamy

Fertilization is an internal process in mammals which takes place in the ampulla isthmus junction of the fallopian tube. The sperms swim towards the fallopian tube in search of the egg to fertilise it. Only one out of million sperms fertilises the egg. 

The process of fertilization can only occur if the ovum and sperm transports simultaneously to the ampullary-isthmic junction of the fallopian tube. The egg gets fertilised without 6 hours of fertilization. 

Once the sperm touches the vitelline membrane, the membrane undergoes physicochemical changes and converts into fertilization membrane. Once it converts into fertilization membrane the entry of other sperms are stopped in order to avoid polyspermy

Here, I have just explained the tip of an ice berg, if you want to know more about fertilization and implantation, click here to read that article. 

Related article: Gastrulation 

Handwritten notes:

Below I have embedded my handwritten notes which would help you in revision and understanding any topic as I have covered very few topics in this post which are the main ones. 

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