Month: December 2021

A letter of thanks

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Gametogenesis (part – 1)

to watch video on this topic click on : https://youtu.be/8GiT1WUjqiE

It is the process of gamete formation in sexually reproducing organism. Sexually reproducing organism has two types of cell somatic cell and germinal cell. Both have diploid number of chromosomes. Somatic cell forms various body organs and always multiplies by mitotic division. Germinal cell form gamete in animal body by successive mitotic and meiotic division.

Process of gametogenesis is of two types: spermatogenesis and oogenesis     

Spermatogenesis

It is the formation of haploid microscopic and functional male gametes called spermatozoa from diploid reproductive cell spermatogonia (2n) that present in the testis of male body.

Process of spermatogenesis is divided into two parts:

  1. Formation of spermatid

It is further divided into three processes.

Multiplicative phase: it involve the rapid mitotic division of diploid primary germ cells that called gonocytes present in germinal epithelium of the seminiferous tubules of testis this form large number of sperm mother cells that are called spermatogonia. Some spermatogonia act as stem cells, while some other spermatogonia enter the growth phase.    

Growth phase: in this spermatogonium first increase in size by accumulation of nutritive material and called primary spermatocyte.

Maturation phase: in this diploid primary spermatocyte undergoes meiosis 1 and forms two haploid cells called secondary spermatocyte each have 23 chromosome immediately followed by meiosis 2 in each secondary spermatocyte to form two haploid spermatids each have 23 chromosome in it. Each spermatogonium produces 4 haploid spermatids.

  1. Spermiogenesis

The transformation of non-motile, rounded and haploid spermatids into functional and motile spermatozoa is called Spermiogenesis. It involve following changes:


·       Nucleus becomes condensed, narrow and anteriorly pointed due to loss of material like RNA and most of proteins.
·       Mature spermatozoa are released into lumen of seminiferous tubules. Two testis of young adult form about 120 million sperm each day.
·       Process of spermatogenesis start at the stage of puberty due to increase secretion of gonadotropin releasing hormone (GnRH) form hypothalamus of brain. GnRH stimulates the adinohypophysis to secrete two gonadotropin FSH and ICSH. FSH stimulate sertoli cell of testis to secrete certain factors that help in spermatogenesis. ICSH stimulate leydig cells of testis to secrete male sex hormone testosterone.
·       A part of Golgi body of spermatids forms the acrosome.
·       Centrioles of spermatids form the neck of sperm.
·       Mitochondria form a spiral ring behind the neck around distal Centrioles.

class 10 and 12th, biology, Female reproductive system

to watch video click on https://youtu.be/3cESkAlRa_g

Accessory glands of female body

  1. Bartholin’s glands (bulbo-vestibular gland): these are one pair, small size gland and present behind labia minora, one on either side of vaginal orifice. This secretes mucus to lubricate the vagina at the time of mating and parturition.
  2. Breast these are one pair rounded structure that present on ventral thoracic wall. Each is convex and has an erectile nipple in its middle. The nipple has 25 opening of lactiferous ducts which carry milk from mammary gland to nipple. Lactiferous duct dilates and form lactiferous ampullae just beneath the nipple to store the milk. Breasts are small sized up to puberty. Their size increases after puberty under the stimulation of estrogen secreted by follicular cells of graffian follicle of ovary. Size of ovary further increased during pregnancy and after child birth under stimulation of prolactin.

Hormonal control

  • FSH of pituitary control transformation of primary follicle into graffian follicle, maturation of ovum and secretion of estrogen by its follicular cell.
  • LH regulates ovulation from follicle, transformation of follicle into corpus leutium and secretion of progesterone from leutium.
  • Growth and functioning of secondary sex organ controlled by progesterone and estrogen. Progesterone promotes implantation and also helps in development of foetus. At the end of pregnancy relexin released from corpus albican and help to broaden the pelvis for easy parturition.

Characterstics

  1. Enlargement of breast
  2. Ovulation and menstrual cycle begin.
  3. Broadening of hip region due to widening of pelvis.
  4. Stoppage of growth of long bones.
  5. Increase in subcutaneous fat in thighs, face and buttocks.

class 12th, chapter 3, Female productive system

To watch video on this topic click on https://youtu.be/3cESkAlRa_g

It is concerned with the formation of ova, fertilization, foetal development and child birth. It is located in pelvis region. It consists of following parts:

Ovaries

these are the primary sex organs of female. These are small sized structure that remains suspended in abdominal cavity by mesentery called mesovarium. Each ovary lined by cuboidal germinal epithelium. There is weakly developed connective tissue layer, called tunica albugenia. There are number of small, oval or rounded ovarian follicle in different stage of oogenesis in region of ovary. Every month primary follicle transformed into mature follicle under stimulation of FSH.

Graffian follicle has a secondary oocyte surrounded by few layer of follicular cells. Ovaries are concerned with the formation of ova and secretion of female sex hormones.


Fallopian tube
it is one paired long, ciliated, muscular tube that extends from periphery of ovary to uterus. Each tube divided into three parts: ampula, isthmus and uterine part. Fallopian tube concerned with the conduction of ovum or zygote towards the uterus by peristaltic and cilliary action. It is the site of fertilization.
Uterus
It is hollow muscular, highly vascularised and innervated pear shaped structure that present in the pelvis region.
Vagina
It is long fibro muscular tube that lined by the non-keratinized stratified squamous epithelium. It finally opens into vaginal orifice. Vagina acts as both copulation canals as it receives the sperms from penis during copulation and birth canal during parturition.
Vulva
it is external genetalia of female. The vestibular (region) part has two apertures upper external uretheral orifice and lower vaginal orifice. Vaginal orifice is partially covered by membranous fold, called hymen. It is often torn during the first intercourse. Vestibule is covered by two pairs of moist skin folds with sebaceous glands. Inner small pair called labia minora and outer larger pair called labia majora. Labia minora anteriorly fuses to form a skin fold called prepuce present in front of clitoris. Clitoris is a sensitive portion which is homologous to penis. Labia minora posteriorly fuses to form a membranous fold that called forchette.                    

Hormonal control (animal hormones), class 10 and 11th

For video on animal hormones click on : https://youtu.be/9pLRiWNnL1c

Growth, maintenance and functioning of secondary sex organs (epididymis, penis, and vasa deference) are under the control of testosterone hormone secreted by leydig cell of testis. While seminiferous tubules and leydig cells are under control of FSH and ICSH. Sertoli cell secrete protein inhibin that suppress the action of FSH.

  • Puberty in male is controlled by testosterone that secreted from leydig cell of testis these cells are stimulated by ICSH.

Characteristics

  • Increase in height due to rapid growth of muscles.
  • Seminiferous tubules start to produce sperm.

Male reproductive system, class 10 and 12th, Biology

To watch video on this topic click on : https://youtu.be/vzrR5xI2FeM

It is located in the pelvic region. It has following parts:

Testis

these are one pair small sized, oval shaped, pinkished colored primary sex organ of male system. These are present in a pouch like structure that called scrotum. Cavity of scrotum remains connected with the cavity of abdomen by inguinal canal. Scrotum acts as the thermo- regulator and helps to maintain testicular temperature 20C lower than body.

Each testis is covered by white fibrous layer called tunica albugenia. There is septa that divide testis into lobules. Each lobule has 1 to 3 seminiferous tubules. Each seminiferous tubule is lined by germinal epithelium and formed two types of cells: germ cell and sertoli cells.

Germ cell undergoes spermatogenesis and form haploid and motile male gamete called spermatozoa. Sertoli cells provide nutrition to sperm. There are group of interstitial cells (leydig cell) outside the tubules. These cells secrete the male sex hormone testosterone. It control development of sexual characters in male body and show spermatogenesis.

Epididymis

it is an elongated structure on each testis. Its function is to provide food and physiological maturation of sperm. It shows peristaltic and segmented movement for sperm.

Vas deference

it is a long muscular tube that starts from lower portion of epididymis and passes over urinary bladder and finally dilates to form ampullae which join the duct of seminal vessicle to form ejaculatory duct. It passes through prostate gland and joins urethra.

Urethra

it arises from urinary bladder and join the ejaculatory duct to form urinogenital tract or canal as it carries urine, sperms and secretion of seminal vessicle, prostrate and Cowper’s gland.

Penis

it is cylindrical erectile and copulatory organ it forms the external genetalia of male. It is supported by three erectile tissues. Two posterior corpora cavernosa and one anterior corpus spongiosum (it surrounds the urinogenital canal). Tip of the penis is highly sensitive and is known as glans penis. It is covered by retractile skin fold called prepuce.

Penis help in copulation. Errection of penis is due to rush of arterial blood into the sinuses of corpus spongiosum aided by the contraction of erector of penis muscles.

T. S. OF PENIS

Accessory genital gland of male

  1. Seminal vesicles: these are one pair of structure that presents b/w the bladder and rectum. Its secretion contains 60% of semen and is mainly composed of citrate, fructose, several proteins and prostaglandins which activate the spermatozoa and stimulate vaginal contractions that help in copulation.
  2. Prostate gland: it pours its alkaline secretion in urethra. It composed of some lipid, small amount of citric acid, bicarbonate ion and few enzymes. Prostrate secretion forms 30% part of semen. It activate sperm and also neutralizes acidity of urine which may kill the sperm.
  3. Cowper’s gland: there are one pair, white pea shaped gland present at the base of penis. It secretes a mucous like substance that lubricates the penis for frictionless movement of penis during copulation.

Secretion of accessory sex gland is called seminal plasma. It is rich in fructose, calcium and certain enzymes. Seminal fluid along with sperm is called semen. It provides proper pH and ionic strength.

Function of male reproductive system

  • Spermatogenesis by germ cells of seminiferous tubules.
  • Secretion of male hormone, testosterone.
  • Transfer of sperm into vagina of female body during copulation.