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Friday, 25 September 2015

FSc Notes Biology Part 2 Chapter 18 Reproduction Notes

FSc Notes Biology Part 2 Chapter 18 Reproduction Notes


A process in which living organisms produce offspring of their own kinds is called Reproduction.
  • To maintain their own species.
  • For continuation of life generation after generation.
  • To transfer the hereditary characters to the new generation.
  • Introduction of new characters which help in evolution.

Asexual Reproduction: 

The production of new genetically identical offspring from a single parent without fusion of gametes is called Asexual reproduction. In this process only mitosis is involved. It occurs mostly in plants and lower animals.
It is a fast and shortcut method of reproduction which results in rapid increase in the number of organisms.
The new organism resemble to their parents physically and genetically. There is no need of fertilization. No new variety is produced. There are different types of asexual reproduction: Budding, Grafting, Spore formation, Binary fission, apomixes, parthneocarpy, Cloning, Tissue

Sexual Reproduction: 

In this process two haploid gametes unit together forming a diploid zygote. This zygote develops into new organisms. In the formation of gametes meiosis takes place. These gametes may come from a single parent or from separate male and female parents. Sexual reproduction occurs in many higher animals and plants.


The production of embryo or seeds without meiosis and fertilization is called apomixes. Apomixes is a type of asexual reproduction and naturally occurs in some plants. Those plants which are reproduces by Apomixes are called “Apomicts” in apomixes fertilization and meiosis fails to occur. Apomixes occurs by following different methods.
  • Development of somatic cell into a diploid embryo.
  • Direct development of unreduced megaspore (by suppression of meiosis) into a diploid embryo.
  • Development of embryo from haploid synergids or antipodal cells. 
Plants develop from such embryos are haploid and sterile. There are two types of apomicts

Facultative Apomicts: These plants can reproduce both sexually and ampomictically e.g. Potentilla.
Obligate Apomicts: These plants can reproduce only by apomixes.

Impotance and Application of Asexual Reproduction

It requires only one parent.
It produces exact individuals of parental variety.
It is a quick method to grow plants on large surface area.
It is economical method of reproduction.

Tissue Culture:

Artificial method in which a complete organism is produce from a tissue fragment by treating with hormones in a growth medium is called Tissue Culture. Tissue culture was first introduced by F.C Steward and his student in 1950. He regenerated a whole plant from somatic cells of a carrot mature and specialized plant cells’ nucleus retain the ability to grow into a new plant under suitable condition. Two methods are used in tissue culture:
  1. A small piece of plant tissue is taken from root or stem. This tissue is separated into individual cells by treating it with enzyme. These cells are then treated with specific plant hormones. This hormone induce cell division and differentiation. Thus a complete plant is produced from a single cell.
  2. A small piece of plant tissue is placed in a nutrient medium. The cells start division and produce a shapeless mass called “Callus”. This callus produces a completed plant in the presence of specific hormone.
Tissue culture plants are stronger than plants produced by seeds. Plants with desirable character are developed. These plants have resistance against disease. By plant culture useful chemicals are obtained such as shikonin which is used: 
In Chemical silk industry.
Treatment of injuries caused by burning.

These plants are sterile which do not reproduce by sexual method.
This technique may cause change in structure or number of chromosomes.


The artificial technique of asexual reproduction in which genetically identical individual are produced from a single parents’ cells is called Cloning. Cloning is a Greek word which means ‘twig’ Organism produced by cloning are called “clones”. Clones are genetically duplicate copies of their own and single parent. Clones show little genotypic differences from their parent due to mutation. Sea urchin was the first animal cloned in 1800. In November 2001 the first human embryo was cloned.

This method is used in orchards and pinus trees to obtain wood. Cloning is used for preservation of best quality genes, e.g. In 2001 an endangered wild sheep named “Mouflon” was cloned.
Cloning also help to increase the agricultural output.

Clones have short life span. Clones are less resistant to diseases and environmental stresses.

Sexual Reproduction in Plants:

Sexual reproduction occurs in both lower and higher plants. but sexual reproduction is differ in different plants. This variation enabled the plants to migrate from water and spread in different land habitats. Sexual reproduction in different plants are as under:
Sexual Reproduction in Algae: Algae have flagellated sperm which fertilizes egg in water. After fertilization zygote develop into new plant without any protection.
Sexual Reproduction in Bryophyt: Bryophytes are first land plants and grow in damp and shady places. Because they have flagellated sperm and less protected sex organs.
Sexual Reproduction in Pterdophytes: They also grow in damp and shady places. Their gametophyte produces flagellated male gamete which moves toward the egg in the presence of moisture.
Sexual Reproduction in Higher vascular plants: In higher vascular plants sexual reproduction is more developed. Their seeds provide protection and stored food to the embryo. These plants do not require water for sexual reproduction. Higher vascular plants are divided into two groups:
Gymnosperm: with naked seeds.
Angiosperms: with seeds enclosed inside fruits.

Gymnosperm: Gymnosperms are cone producing plants. Male cone produce pollen grain and female cone produces megaspore. Pollen grains transfer from male cone to female cone by air. After transfer, pollen grains form pollen tube containing two sperm. Megaspore develops into female gametophyte containing an egg. Fertilization occur with the help of pollen tube.
Angiosperm: Angiosperms are flower producing plants. Pollen grains produce in another of stamen while megaspore produce in the ovary of carpel. Pollination occurs with the help of winds, water or insects. Pollen grain form pollen tube having two sperms. Megaspore develops into female gametophyte containing an egg. Pollen tube helps in fertilization.


The group of flower developed on one common axis is called inflorescence. Inflorescence is a Latin word means “Flower cluster” the axis of an inflorescence is called “peduncle”. Large flower develop singly on pedicels and are called solitary flowers form clusters to attract insects for pollination. There are two types of inflorescence:
  1. Recemose inflorescence.
  2. Cymose inflorescence.

Recemose Inflorescence: 

The inflorescence in which the main axis (peduncle) continues to grow and produces flowers from the sides until the last flower is formed at its apex is called Recemose. Younger flowers are present at the apex and older at the base. This is called acropetal succession.
Recemose inflorescence consists of following types:
Typical Receme: In this case the main axis is elongated. It produces many lateral (side) pedicellate or stalk flower example, Amaltas.
Spike: The main axis is elongated. It produces many lateral sessile or stalkless flowers. Example spinach, bottle brush.
Catkin: Main axis is elongated having unisexual sessile flowers. Example Mulberry, willow, poplar.
Corymb: The main axis is short having flowers of unequal stalks. Stalks of lower flowers are longer than upper younger flowers. Thus all the flowers come at the same level. Example; Candytuft (Iberis)
Umbel: The main axis is shortened producing pedicel late flowers. All flowers arise from a common point or tip of main axis. Younger flowers are present in the center while older towards the periphery (sides) example – Hydrocotyle. When a number of umbels are present on the tip of main axis this is called compound umbel.
Panicle: A much branched receme is called panicle. Example; Grapes, Mango.
Capitulum: The main axis becomes a flat disk called Receptacle, on which small sessile flowers are grouped together. The outer flowers are older than the inner ones. The whole inflorescence look like a single flower. Example- sunflower.

Cymose Inflorescence: 

That inflorescence in which the main axis soon ends in a flower and produces one or more branches which also terminate in a flower is called cymose inflorescence. Flower developed in two ways.
Basipetal Succession: older flowers are present at the apex and younger at the base.
Centripetal Succession: younger flowers in the center and older towards the sides.
There are three main types of cymose:
Uniparous or Monochasial Cymose: The main axis ends in a flower below which one daughter axis is produced. The daughter axis also ends in a flower and again produces one daughter axis. Example – Begonia, Tradescontia.
Biparous or Dichasial Cyme: The main axis ends in a flower and produces two daughter axis below. Each daughter axis ends in a flower and produces two daughter axis again. Such daughter axis show similar branching manner.Example – Night Jasmine, Ipomea.
Multiparous or Polychasial Cyme: The main axis ends in a flower and produces three or more daughter axis below. Each daughter axis again terminates in a flower and repeat this process. Example - Euphorbia.

Parthenocarpic Fruits

The formation of seedless fruits without fertilization is called partenocarpic fruit while the process is called parthenocarpy. In some plants pollination and fertilization do not occur. Such plants produce seedless fruits.
Cause: This ovary is then changed into fruit directly without pollination and fertilization. Example: Banana, Pineapple, Grapes.
Benefit: Parthenocarpy is sometime artificially induced for commercial purposes by adding auxins as in tomato, pepper etc.


The inactive or sleeping stage of bud or seed before germination is called Dormancy. In dormancy the viable seeds or bud fail to germinate even under favorable condition. Dormancy is a temporary arrest in growth.
Duration: In different plants the period of dormancy is different. The seeds any remain inactive for few days or 1 – 2 years. Naturally the length of dormancy period is equal to the length of unfavorable time period. Thus breakage of dormancy and completion of unfavorable conditions occur at the same time.
Cause: Main reasons seed dormancy is:
  1. Hard seeds coat
  2. immature embryo
  3. chemical inhibitors
  4. Light sensitive seeds.
Methods of Breaking Dormancy
Pressure: A pressure of 2000 atm 18oC for about 5 – 20 minutes can break seed dormancy.
Low Temperature: If seeds are treated in moist medium at 5 – 20 degree Celsius for sometime can also break seed dormancy.
Plant Hormone: Seed dormancy is also artificially broken by using different plant hormones.

Advantage of Dormancy:
Dormancy increases the chances of survival. Dormancy help the plants to overcome unfavorable condition which may be harmful for their vegetative and reproductive growth. Without dormancy if the seeds germinate under all conditions then they will become useless to human for consumption as food.


The conversion of winter variety into spring variety by low temperature treatment is called Vernalization. (OR) The production of early flowering in plants by chilling treatment is called Vernalization.
Vernalization is Latin word means “springificaiton or spring”.
Discovery: The idea of Vernalizaiton was first presented by Gassner in 1918. The term Vernalization was used by Lysenko in 1928.

Site of Vernalizaiton: It has been experimentally proved that all dividing cells are the potential site of Vernalization. Low temperature stimulus is received by;
Mature stem tip or embryo of the seed.

Stage of cold treatment: The stage of cold treatment vary in different plants. Some plants require cold treatment at the seed stage. Some plants can be vernalized when they become at least 10days old.

Duration of low temperature: Duration of chilling treatment varies from 4 days to 3 months.

There are two theories to explain the mechanism of Vernalization.
Thermal Theory: Plant passes through tow phases of development thermo phase and photo phase. But thermo phase completed before photo phase during which plant separes itself for flowering. Verna line hormone which induces flowering. But according to some scientists Gibberellins hormone is involved in Vernalizaiton.

Conditions for Vernalizaiton:
Water: Dry seeds cannot be vernalized.
Oxygen: Vernalizaiton is an aerobic process and need energy.
Temperature: Suitable temperature of Vernalization ranges between 1 – 7 degree Celsius Temperature around 4 degree Celsius is most effective in Vernalization.

Significance: Vernalization shortens the vegetative period of plants. It increases the cold resistance of plants. Out of season flowers can be produced by Vernalizaiton. It also increases the resistance of plants to fungal diseases. It can be also used to increase the yield of crops.


The response of plants to a change in the relative length of daylight and darkness in 24 hours cycle is called photoperiodism. OR The response of plants to the photoperiod in the form of flowering is called photoperiodism.

Discovery: Klebs 1918 observed that the duration of light controls flowering of plants. Photperiodism was first discovered by Garner and Allard in 1920. They showed experimentally that flowering of plants can be controlled by controlling the length of light duration that falls on the plants.

Effects of photoperiod: The relative length of day and night is called photoperiod. In some plants flowering is affected by the day length. These plants require certain day length to produce flowers.

Classification of plants on the basis of photoperiodism

According to photoperiod response, the plants are classified into three groups:
Short Day Plants: They are also called long night plants. These plants require a relatively short day light period for flowering. They need a light period of usually 8 – 10 hours and a dark period of about 14 – 16 hours for flowering. Example: Tobacco, Soyabean, Gul-e-daudi, etc.
Long day Plants: These plants require a longer day light period for flowering. In these plants the light period is critical (11 – 16 hours). Example: Spinach, Sugar beet, potatoes etc.
Day Neutral plants: These plants are independent of day length and can flower both in long and short days. These plants produce flower whenever they become mature. Example: Cotton, tomato, Sunflower, cucumber.


Plants contain a light sensitive protein called phytochrome. Phytochrome detect the time of flowering in plants. These light receptors are discovered in 1960. Location: Phytochrome is present in the leaves. (cell membrane) Type: Phytochrome exists in two forms.
Pr: it absorb red light. Pr is inactive form
PFr: it absorbs far red light. PFr is active form.

Both these forms are internconvertable. There are two methods of Interconversion.
  1. Photo conversion
  2. Thermal conversion
When PFr form absorbs red light, it is converted into PFr. When PFr form absorbs far red light, it is converted into Pr. This is known as photo conversion It is very rapid and complete within 1 – 4 minutes. PFr form also converted into Pr during dark. This is thermal conversion and dependent upon temperature. Thermal conversion is very slow and takes few hours.
Pr ------------------------>PFr
       Thermal Conversion

Role of phytochrome in short Day Plants:
Short day plants require high quantity of Pr for flowering. These plants grow in winter. At the end of the day the quantity of PFr is high than Pr. But short days are followed by long night in winter. During long night more PF4 converts in Pr. This high ratio of Pr stimulate flowering in short day plants.

Role of Phytochrome in long day plants:

Long day plants require a high quantity of PFr for flowering. At the end of the day the quantity
of PFr converts into Pr. This high ratio of PFr promotes flowering in long day plants.

Flowering Stimulus (Florigen):

Flowering in plants is controlled by a hormone called Florigen. Florigen is also called flowering stimulus.

Site of formation: Florigen is produced in the leaves under the influence of phytochrome. It was experimentally proved by Chailakhain in 1936.

Transport: Florigen moves from the leaves to the buds through the phloem. It can also move from one plant to another through the graft union. Florigen could not be isolated and remain a hypothetical hormone.

Experiments of Chailakhain: Chailakhain performed experiments on short day plant Chrysanthemum.
Experiment No#1: He took some chrysanthemum plants and removed the leaves from the upper half and left the leaves on lower half. He exposed the upper half of the plants to long days light and lower half to short days light.
Result: All plants produced flowers.
Experiment No#2: In this experiment he exposed the upper half of plants to short days and lower half to long days.
Result: plants did no produce flower.

From these experiments he concluded that:
  1. Length of the day is detected by the leaves in both short day and long day plants.
  2. Florigen is produced in the leaves.
  3. From leaves Florigen moves to the buds and initiate flowering.

Reproduction in Animal

The ability of living organisms to produce individual of their own kinds is called Reproduction.

Asexual Reproduction:

The production/development of new offspring from a single parent without fusion of two gametes is called Asexual reproduction. In this process, No gametes are produced, No formation of zygote. Offspring identical or similar to parents.
Asexual reproduction is of the following types:
Binary Fission: In this process the parental organism divides into two daughter animals. First the parent nucleus divides into two daughter nuclei. Then cytoplasm also divides forming two new organisms. Binary fission occurs during favorable condition. Example; Amoeba, Paramecium, Euglena etc.
Multiple Fission: The formation of many daughter organisms from a single parent organism is called multiple fission. In this process the parental cell form a cyst around itself. The parental nucleus divides into many nuclei. Cytoplasm also divides and surround each nucleus. Thus many daughter organism are formed within the cyst. In favorable conditions the cyst breaks and releases the daughter organisms. Multiple fission occur during unfavorable condition. Example: Amoeba, Plasmodium.
Budding: In this process a small outgrowth develop on the parent body called bud. This bud gradually increases in size and may separate or remain attached to the parent. This bud develops into new individual. Bud may be of two types: The formation of bud from external body surface is called exogenous bud. The formation of bud from internal body cells is called endogenous buds. These internal buds disintegrates the parent body and form new individuals.

Regeneration: The ability of organism to replace or repair their lost or damaged body part is called regeneration. Examples: Salamander can regenerate their limbs and tail. In human damaged part of liver is regenerated again. Planaria, Earthworm.


 The development of egg without fertilization to form a new individual is called parthenogenesis. It is a Greek word parthenos means “Virgin” and genesis means “origin” Parthenogenesis literally means the birth of an individual from virgin. The individual reproducing by parthenogenesis are called parthenotes. Parthenogenesis occurs naturally but can also be induced artificially by certain chemicals. Some organism reproduces only be parthenogenesis. e.g. some wasp. But some animal show alternation of parthenogenesis and sexual reproduction e.g. Apid, hone bee. Parthenogenesis is of two types:
  1. Haploid Parthenogenesis: in which haploid egg develops into haploid male. For example in honey bee male (drone) develops parthenogenetically from unfertilized egg. While fertilized egg develop into a female.
  2. Diploid parthenogenesis: in which diploid egg develops into a diploid female. Example: Apid. In summer Apid s egg parthenogenetically develop into female. In winter male appear by sexual reproduction.


Twins is a type of multiple birth in which a female give birth to two babies at the same time. There are two types of twins:
  1. Identical Twins: These twins developed from a single zygote. This zygote separate at 2 cells into tow embryos. Each embryo gives rise to a new individual. They are produced mitotically (asexually) and identical. They have same genetic make up. They are of the same sex i.e. both male and female.
  2. Fraternal Twins: These twins are developed from two different zygotes. Eggs. Each egg is fertilized by separate sperm forming two zygotes. These zygotes develop into new offspring. Such twins are genetically different. They may be of same or different sexes. They are produced sexually and non identical.

Sexual Reproduction

The fusion of two male and female gametes to form new individual is called sexual reproduction. As a result of union a zygote is formed which develop into a new individual. Sexual reproduction is found in higher animals. Such type of reproduction needs tow types of individual i.e. male and female.
  • In male testes are present which produces sperm by spermatogenesis.
  • In female ovaries are present which produces ova or egg.

Hermaphrodite Animals

Those animals in which both testes and ovaries are present in the same body are called hermaphrodite animals. In some hermaphrodite animals cross fertilization occur because sperms and ova mature at different time (earthworm). But in some self fertilization occur e.g. Tapeworm.


The fusion of male and female gametes to form zygote is called fertilization. In this process the haploid gametes unite to form a diploid zygote. Fertilization is necessary step in sexual reproduction. Because without fertilization sexual reproduction is impossible. Both gametes are either provided by tow different sexes or by the same individual (hermaphrodite). Fertilization is of two types:
  1. External Fertilization: The fusion of male and female gametes outside the female body is called external fertilization. It occurs in aquatic environment where male gamete swim towards the female gamete. Development is also external due to stable condition of water. Example: Frog, Fishes, etc.
  2. Internal fertilization: The fusion of male and female gametes inside the female body is called internal fertilization. It occur in all land animals. Development may be within female body or outside the female body in a shelled egg. According to the site of fertilization and way of development animals are placed into three major groups.

Oviparous Animal

Those animals which lay eggs and in which the whole development of new individual occur outside the mother body are called oviparous. Example; fishes, Birds, Reptile, Amphibian etc. In these animals fertilization is internal or external. Their egg contain large amount of yolk which act as food for developing embryo till hatching. If the egg contain less yolk then zygote will hatch into a large e.g. egg of frog. If the egg contains more yolk then young one will hatch e.g. Birds, reptiles.

Viviparous Animal

This condition is known as viviparity. Example; Cow, Goat, Sheep, Human etc. In these animals fertilization is internal. Their eggs contain less amount of yolk for the development of embryo. Embryo get food from mother body through a connection called placenta.

Ovo – vivparous Animal

Those animals which lay eggs but retain them in their body till hatching are called ovoviviparous animals. Fertilization is internal in such animals. Example: Duck – billed platypus, spiny ant eater.

Male Reproductive System

Male reproductive system consists of three parts:
  1. Testes
  2. Duct System
  3. External Genitalia

(1) Testes:

Testes are the factories for the formation of male gametes called sperm.
Number – Testes are two in number.
Shape – Testes are oval in shape.
Size – Testes are two inches long.
Location – Testes are presents outside the body in a sac – like structure called scrotum. In foetal stage testes are present in the abdomen. If the testes remain inside the abdomen the individual will be sterile. In scrotum temperature is slightly cooler than the body temperature. Because the optimum temperature for sperm production is 35 degree Celsius.
Structure: Each testis composed of interstitial cells and somniferous tubules. Each seminiferous tubule is about 5 meter long. Seminiferous tubules are highly coiled tubes. Each testis consists of about 900 seminiferous tubules. Seminiferous tubules open into a system of spaces called rate tests. Seminiferous epithelium consists of two types of cells.
  1. Germ Cells: These cells produce sperm by spermatogenesis. Sperms produced continuously from puberty until 70 years of age.
  2. Sertoli Cells: These cells also secrete a fluid which helps in sperm transport in duct. These cells provide protection and nourishment to the developing sperms.

(2) Duct System:

The duct system consist of following parts:
  1. Epididyuis
  2. Vas deferns
  3. Urethra
Epididmus: Seminiferous tubules opens into a single coiled duct called Epididmus through vas efference. Epididmus is about 6 – 7 meter long. Epididmus help in:
  • Maturation and Storage of sperms.
  • While reabsorption of incomplete sperms

Vas Defrens: From Epididmus a duct arises called Vas deferens. It collects sperms from the Epididmus.

Urethra: The two vas deferens unite to form a single duct called urethra. In this duct sperm and urine come at spate time. There are three glands located in the duct system. Seminal vesicle: It open into vas deferens and produces a secretion. Prostate gland: It opens into the urethra and secretes a milky secretion. This secretion neutralized the acidity of urethra. Cowper s gland: These glands also open into the urethra. It secretion provides lubrication to the urethra. The sperms plus secretions of seminal vesicles, prostate and Cowper s gland make a milky fluid called semen.

(3) External Genitalia (Penis)

It is a muscular organ contains sponge like spaces. It transfers the sperms into the vagina of female during copulation.

Female Reproductive System

The female reproductive system consists of three main parts.
  1. Ovaries
  2. Duct system
  3. External Genitalia

(1) Ovaries:

Number – There are two ovaries in human female.
Shape – Ovaries are oval shaped structure.
Size – Each ovary is about one and half inches in length.
Location – Ovaries are located in the lower region of abdomen called pelvic cavity. Each ovary consists of two types of cells:
  1. Germ Cells: These cells produce ova or egg by the process of oogenesis.
  2. Follicle Cells: These cells give protection and nutrition to the developing eggs. The ova develop within these follicle cells. When an ovum is mature the follicle cells wall rupture and the ovum is released. This release of ovum is called ovulation. Normally only one ovum mature in each ovary alternately during one month.

(2) Duct system:

The duct system consists of:
  1. Oviducts
  2. uterus
  3. Vagina
Oviducts: The mature ovum is released from the ovary into a duct called oviduct. In this duct the ovum is fertilized by sperms. In the oviduct cilia are present which help in the movement of ovum.
Uterus: The two oviducts open into a large pear shaped structure called uterus. In the uterus development of embryo takes place. The muscular part of uterus is called myometrium. While spongy an vascular tissues of uterus is called endometrium.
Vagina: the lower part of uterus opens into vagina in the form of a narrow tube called cervix.

(3) External Genitalia:

The external female reproductive organs are collectively called vulva. Vulva consists of:
  1. Labia majora
  2. Labia minora.
Clitoris – which help in sexual excitation of female. In virgins the vagina is covered by a thin layer called hymen.

Reproductive Cycle in Female

In female production of egg is a cyclic activity as compared to males. In mammals the female reproductive cycles are as follows:
(1) Oestrus Cycle: In some animals the female mate with a male at regular intervals. This desire to mate at a specific time is called oestrous or heat period. This cycle is found in all female mammals except human female. During this cycle structural and physiological changes occur in the reproductive tract of female. These changes are due to the secretions of estrogen hormone. In the female body a special kind of heat is produced and become ready for mating. Release of egg occur during the period of oestrus. This cycle take place during breeding season.
  • Duration – Oestrous cycle varies in length in different animals.
  • Laboratory rat – Oestrous cycle is of five days.
  • In Bitch – It occur after every six months.
  • In sheep – it is 16 days.
  • In cows – it is of 20 days.
  • In bat – It occur once in a year.
  • Example: Rat, Cats, Dogs, Mammals, etc.

(2) Menstrual Cycle:
The periodic discharge of blood, broken tissues and unfertilized egg through vagina is called menstrual cycle. During one cycle only one egg is released. The first menstrual cycle is called Menarche. It starts at the age of 12, 13, 14 years. The stoppage of menstrual cycle at old age (45 – 55) is called Menopause.
Duration: Normal average duration is 28 days. But it may very from 20 – 45 days. Menstrual fluid is about 70 ml in volume.


There are four stages in menstrual cycle.
Follicular Stage: (1 – 5 day) This stage starts from the end of the previous menstruation till the beginning of ovulation. Duration this stage one or more ova or egg start to develop. Follicle cells around the developing egg are arranges in layers forming a cavity. Some follicle cells starts secretion of a hormone called estrogen. Estrogen causes the thickness and vascularization of uterus. Thus uterus becomes soft and spongy because of increase blood supply.
Ovulation: The release of mature ovum from Graafian follicle is called ovulation. The ovum enters the oviduct for fertilization. This release of egg occurs on the 14th day of menstrual cycle. Pituitary gland secretes luteinizing hormone which helps in the release of egg from the follicle.
Luteal stage: This stage continues from the 14th – 28th days of the cycle. After ovulation graafian follicles are converted into a yellow body called corpus lustrum. This corpus lustrum secretes a hormone called progesterone.
  • Progesterone perform the following functions.
  • Progesterone increase thickness of uterus.
  • It prepare the uterus for implantation of zygote.
  • Prevent contraction of uterine wall
  • Suppresses ovulation.
Menstrual Stage
When ovum is not fertilized, corpus lustrum degenerates and stops progesterone secretion. It results in the breakdown of thickened spongy part of the uterus. The broken tissues along with blood and unfertilized egg are discharged. This is called menstruation.


The period from implantation of zygote in the uterus till birth of baby is called pregnancy or gestation period. OR the period of development between fertilization and birth is called pregnancy.
Duration: Pregnancy duration is usually 9 months or 280 days. The time of pregnancy is divided into 3 periods or trimesters.
  • Beginning
  • Middle
  • Final stage
Each trimester consists of 3 months.
By repeated cell division the zygote change into an embryo. The embryo is then carried toward the uterus and implanted there. A connection is form between embryo and mother called placenta. This placenta help in the exchange of food, O2, hormones, wastes. Cell division and growth continue and different organs are formed. Heart is the first organ to form. After 8 weeks all organs are formed and embryo is now called fetus. The structure that connects the fetus with placenta is called umbilical cord.
Abortion or Miscarriage: If fetus is lost in the first or second trimester, it is called abortion.
Pre-mature Birth: If a baby born before 32 weeks of pregnancy is called Pre-mature birth.
Still birth: If a baby born dead before 24 weeks of pregnancy is called still birth.

Labour or Delivery

All those changes which cause birth of the baby are called labour.
Birth occurs in three stages:
  • Dilation of cervix: A few days before birth the baby’s head turned down in the uterus and points towards the cervix. Baby’s head help in the dilation of cervix.
  • Expulsion or Delivery: In this stage pituitary gland secrete a hormone called oxytocin. The muscles of uterus start periodic contraction and relation. This contraction causes labour pain. Eventually the contractions push the baby out of the mother’s body.
  • Delivery of placenta: Further contractions of uterus push the placenta and umbilical cord (after birth) out of the mother’s body.


The secretion of milk is called lactation. Lactation is under the control of hormones such as:
  • Lactogen
  • Lutetorophic hormone
Daily secretion of milk is 1.5 liters. The milk produced initially by the mammary gland is called colostrums. This colostrum is rich in antibodies. Mother’s milk should continue till two years. Menstrual cycle may not occur during nursing of baby. But in some cases cycle starts even during her breast feeding.

Invitro Fertilization

The process of artificial of egg outside the female body in a test tube is called invitro fertilization. Body born by this method is called test tube baby. This technology has open a new clinical research work in the field of infertility.
History: Dr. Petrucci made the first attempt to produce a test tube baby in 1959. First test tube baby was Louis Joy Brown, born on 25th July 1978. Today more than 25000 test tube babies have been produced by this process.
Following are the main steps in Invitro fertilization.
Ova Collection: The women is given with infertility drugs. This drug causes the release of many eggs at one time. These eggs are sucked by a fine needle inserted through the abdominal wall.
Invitro Fertilization: These ova are then mixed with husband sperm in a test tube. As a rest of fertilization zygote is formed.
Embryo Implementation: Embryo at 16 – cells stage is then introduced back to the women’s uterus where it develops Birth of baby occurs in the normal way.

Sexually Transmitted Diseases

Those diseases which transmit from affected person to a healthy person by sex are called sexually transmitted diseases.

(1) Gonorrhea

Gonorrhea is one of the top five SID s in the world. Most cases occur in young people (18 – 24 years) with multiple sex partners. Causative agent: This disease is caused by bacterium Neisseria gonorrhea. This bacterium was first observed by Albert Neisser in 1879.
Effect: This bacteria damage the mucus membrane of urine genital tract. Infection male causes: Urethritis, painful urination, discharges of pus, blockage of spermatic duct causing sterility.
Infection in female: Painful urination. Pelvic inflammation, blockage of oviduct causing sterility and ectopic pregnancy. In newborn cause an eye infection leading to blindness. It can also infect heart, joint, brain etc.
Treatment: It is treated by combined drug therapy of cephalosporin and tetracycline.


Causative agent: It is caused by a bacterium called Treponema palladium.
Effects: There are three stages in syphilis:
Primary Stage: In this stage small painless ulcer called chancre appear at the site of infection. These change disappear after a month.
Secondary Stage: In this stage the bacterium infects many organs. Main Symptoms are sin rash, fever, headache,
Tertiary Stage: In this stage painful tumors called gummas develop in tissues e.g. liver, skin, eyes, bones, reproductive organs, spleen. It can also damage brain and heart.
Treatment: Penicillin is the drug of choice for treating syphilis.

(3) Pathogenesis:

In this disease small painful blisters appear on genitals ant itching sensation occur. These blisters may develop into ulcers. Swollen lymph nodes. Painful urination. Fever, Cervical cancer in female. From mother the disease is also transferred to her baby during birth causing damage to eye and CNS of baby.
Treatment: No complete cure of syphilis.

Written by Asad Hussain

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