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MENSTRUAL CYCLE The reproductive cycle of females is called the menstrual cycle. The first menstruation begins at puberty and is called menarche. This cycle is repeated at an average interval of 28 days. During this cycle various changes occur simultaneously in the ovary and the uterus. This cycle consists of four phases. Menstrual Phase or Bleeding Phase Follicular Phase (Proliferative Phase) Ovulatory Phase Luteal Phase or Secretary Phase Menstrual Phase or Bleeding Phase The cycle starts with the menstrual phase. This phase lasts for about 3 – 5 days. During this cycle bleeding occurs from the uterus of the females. The bleeding occurs due to breakdown of endometrial lining of the uterus and it’s blood vessels which form liquid that comes out through vagina. Menstruation occurs only if the fertilization does not occur. The decreased LH production causes degeneration of corpus luteum which results in degeneration of uterine endometrium and the cycle star...

The human ovum is rounded, non-motile and alecithal. It has abundant cytoplasm called ooplasm. It has a large nucleus called germinal vesicle.  It also contains a nucleolus. The nucleus is covered by plasma membrane, has microvilli to get nutrition from the follicular cells. The side of the ovum which extrudes polar bodies is called animal pole and the opposite side is termed vegetal pole. The ovum is enclosed by two additional egg coats : Inner thin transparent, non cellular, zonapellucida, it is composed of glycoproteins, zona pellucida is secreted by the ovum itself and is called the primary egg membrane. The outer, thick corona radiata formed of radially elongated follicle cells. The space between zona pellucida and corona radiata is called pre-vitelline space.

The sperm or male gamete is a microscopic cell. It consists of four parts. Head  Neck Middle Piece Tail HEAD Human sperm has a flat and oval head. It has a large, compact nucleus and small acrosome at the tip of the nucleus. Acrosome is formed of Golgi apparatus. It contains hydrolytic enzymes. The nucleus contains haploid set of chromosomes. The head is covered by a fibrillar sheath. The nucleus consists of condensed DNA and basic proteins. NECK The neck is very short. It contains two centrioles – one proximal and one distal. The proximal centriole is towards nucleus and plays a key role in the first cleavage of the zygote. The distal centriole is towards tail and gives rise to axial filament of the sperm, which consists of 9 – sets of microtubules triplet arranged in ring. MIDDLE PIECE It is cylindrical. It contains many mitochondria coiled tightly around the axial filament, called mitochondrial spiral. The mitochondria provide energy for the...

Gametogenesis The process of formation of gametes i.e. sperms and ova in the primary sex organs i.e. Testes and Ovaries is called gametogenesis. It is of two types :- The   process of formation of sperms in the testes is called spermatogenesis. The process of formation of ovum inside   the ovary is called oogenesis. Spermatogenesis It is the process of formation of haploid male gametes (spermatozoa) from diploid spermatogonia. In humans, it starts at puberty.  This process is divided into two stages :- Formation of spermatids. Formation of spermatozoa from spermatids. Formation of spermatids The male germinal cells which produce sperms are called primary germinal cells or primordial cells. They are present inside seminiferous tubules. The process of spermatid formation occurs in 3 phases :- Multiplication phase Growth phase Maturation phase Multiplication phase The sperm mother cells or spermatogonia are form...

The human female reproductive system consists of  Two   ovaries  Two fallopian tubes  Uterus,  Vagina,  External genitalia or vulva Female accessory glands. (1) OVARY There is a pair of ovaries present in the abdominal region. They are attached with abdominal walls by an ovarian ligament called mesovarium. Each ovary is almond shaped, 2-4 cm long, 1-3 cm wide and abort 1 cm thick. It is attached to pelvic wall and uterus by ovarian ligament. Functions of Ovary The ovaries are primary sex organs.  They produce female gamete-egg. They also produxce some female hormones like progesterone. Anatomy of ovary: Anatomically each ovary is formed of 3 parts: Germinal epithelium Tunica albuginea Ovarion stroma Germinal epithelium: It is the outermost layer of the ovary.It is formed of squamous epithelium and cuboidal epithelium. It forms oogonia in the foetus. Tunica albuniea:  It is presen...

The male reproductive system of man is formed of the following parts: (1) Scrotum   (2) Testes  (3) Accessory ducts  (4) Glands  (5) External genitalia (1) SCROTUM: The testes are situated outside the abdominal cavity in a pouch called scrotum. It helps in maintaining the low temperature about 2 °  to 2.50 ° C  lower than   the body temperature. Hence it is a thermoregulator. Low temperature is necessary for the development of sperms. (2) TESTES : There is a pair of testes. Each testis is oval in shape.The size of the testis is (4.5*3*2.5)cms in length,width and thickness. They are pinkish in color. They are the primary sex organs in man. Each testis is attached to the scrotum by a thick band called gubernaculum.With the abdominal cavity the testes are connected by spermatic cord. The scrotum is attached to abdominal cavity by inguinal canal. Anotomy of Testis: Each testis is surrounded by the three ...

Humans show sexual dimorphism i.e males and females look different morphologically. They are viviparous i.e give birth to young ones. The males produce sperms and the females produce ova. The fertilization is internal. In humans the reproductive events start at puberty. The major reproductive events in human beings are as follows : Gametogenesis : It is the process of formation of haploid gametes i.e. sperm in males and egg or ovum in females. Insemination : It is the process of introducing sperms into the reproductive tract of female. Fertilization : It is the fusion of two types of gametes i.e. egg and sperm inside the female reproductive tract. It is also known as syngamy. Clevage : As a result of fertilization a single diploid cell is formed, it is called called zygote. The zygote undergoes repeated mitotic division called cleavage. Implantation : It is the process of fixation of blastula in the uterine wall at an appropriate site. Placentation : In order to supp...

Sexual reproduction Sexual reproduction is a type of reproduction in which there is formation and fusion of gametes. It mostly involves two parents. The male produces male gametes – Sperm and the female produces female gametes –Ova. When male and female gametes are produced by different organisms, they are called unisexual or dioecious e.g. frog, dog, man, cockroach etc. When male and female sex cells are present on the same individual, such animals are called bisexual or monoecious e.g. Leech (Hirudinaria), Earthworm, Taenia. Types of Sexual Reproduction Sexual reproduction may be of two types:  Amphigony and Parthenogenesis. Amphigony  : In this type of reproduction two gametes fuse to form a zygote. Parthenogenesis  : It is a type of monoparental reproduction in which an unfertilized egg develops into a fully formed haploid organism. It occurs in some insects e.g. honey bee, wasps. Processes involved in sexual reproduction Gametogenesi...

Asexual Reproduction It is a kind of reproduction in which new individuals are formed from a single parent. There may or may not be gamete formation but there is no fusion of gametes. It is also known as uniparental mode of reproduction. The young ones formed through this process are exact copies of their parents. So they are also called clones of their parents. The members of  the group of clones are called ramets. Types of asexual reproduction There are many types of asexual reproduction. These are: fission, sporulation, budding, fragmentation and regeneration. Fission It is a type of asexual reproduction in which an individual divides into two or more individuals. It may be binary fission or multiple fission. Binary Fission  :  It is a mode of asexual reproduction in which the parent body divides into two equal halves. It may be simple, longitudinal, transverse or oblique binary fission. Simple Binary Fission (irregular binary fission)  ...

Reproduction is defined as the property of all the living organisms to produce individuals of their own kind in order to continue their race.