Human responsibility for the protection of earth
The earth provides habitat, shelter , food and water for all the animals and plants living on this earth. This earth provides very good environment so that living organisms are surviving and will survive in the future also. Among all the animals, man is on the top of the living beings. Yet, man can not think of his own survival without other animals and plants. The existence of life is interlinked. Plants can trap the solar energy and provide Oxygen needed for all the animals. There is transfer of energy from plants to animals and other animals which are carnivores. Man is dominating all the living organisms on this earth. As man is on the top dominating all the living organisms, it becomes responsibility of man to protect all the living organisms and this earth together.
The Zoological name of man is Homo sapiens. Genus Homo means wise. Man is the most intelligent creature of all living organisms on this earth. Man has utilized all the natural resources of the earth the most. Besides, man has utilized the renewable natural resources faster than that can be regenerated naturally. The various activities of man (Anthropogenic) has led to the destruction of naturally growing forests, polluted the water bodies as well the air and surrounding. The establishment of the various industries with their wastes degraded the environment and made less suitable for the living organisms. Also, because of unlimited need of man, industrialization and agriculture have left no space on earth. As man has contributed to the degradation of natural resources, it is the man’s responsibility to protect the earth.
Ways to protect the earth
• Afforestaion and reforestation - plantation of trees and take care of all these plants.
• Control of population of man
• Pollution control
• Conservation of wild life and forest
• Sustainable development not destroying nature
• Use of clean energy like solar energy, wind energy
• Keep in mind that this earth also belongs to all living beings
• Think that by protecting earth and nature, man is protecting himself
Thursday, March 24, 2011
Monday, March 7, 2011
for class XII
Human ear
Ear is stato acoustic organ. It is responsible for sensations of equilibrium and hearing. It is sensitive to frequencies of sound waves and to change in relation with gravity. There are two ears and are situated one on either side of head.
Each ear consists of three main parts.
External ear
Middle ear
Internal ear
External ear -- it consists of pinna, auditory canal and tympanic membrane or ear drum. It is air filled cavity. It receives or collects sound waves and directs he sound waves to middle ear.
Pinnae-- these are flap of tissue supported by cartilages. These are found one on either side of head. these are immovable. Thee is presence of small opening that leads into auditory canal. It collects the sound waves and sends it to auditory canal.
Autitory canal -- it is also known as ear tube or external auditory meatus. It is lined by skin which has hairs for protection. Glands are preset to secret brown wax. If more and more wax is collected, it may cause deafness. It ends in eardrum.
Tympanic membrane-- it is also known as ear drum. It is thin sheet of tissue. it is delicate, membranous structure. It vibrates in response to the sound waves. It transmits sound waves to middle ear.
Middle ear - - it is also air filled cavity. It consist of three tiny bones called ear ossicles . thjey are malleus, incus and stapes, ear ossicles move forward and backward in resplonse to vibrations of ear drum.
Malllleus -- it is hammer shaped and articulate with incus on the other side.
Incus-- it is anvil like structure articulating with malleus on one side and stapes on other side.
Stapes -- it is stirrup like. Its foot plate or base is attached to oval window called fenestra ovalis or fenestra vestibule. These three ear ossicles are arranged in lever like action. They magnify and transfer the vibrations from ear drum to cochlea of inner ear through oval window.
Eustachian tube – it is a tube that leads from pharynx to middle ear. It helps in equalizing air pressure on both sides of ear drum. When air pressure is unequal, the ear drum becomes more stretched and can cause pain.
Inner ear -- it is fluid filled chamber it consists of complex system of canals and cavities. It basically consists of cochlea (associated with hearing) and vestibular apparatus( associated with balance)
Cochlea -- it is a highly coiled tube about 35 mm in length. It has got three canals inside, the vestibular canal, middle canal and tympanic canal. The reissner’s membrane separates the vestibular and middle canal. Similarly basilar membrane separates middle and tympanic canal. Both vestibular and tympanic canal are filled with fluid called perilymph. The vestibular canal is connected to oval window on the other side of which stapes is attached. The tympanic canal is connected to round window. The middle canal is filled with endolymph. There is basilar membrane on one side. The sensory hair cells rest on this basilar membrane. These cells are in contact with tectorial membrane above . the tectorial membrane, sensory hair cells and basilar membrane together form the organ of corti. The organ of corti can generate the sound impulse and send it to brain through auditory nerve.
Mechanism of hearing
As the sound waves enter the external ear, they pass through canal and strike the ear drum. The vibrations of ear drum are transmitted to three ear ossicles which magnify them 20 to 25 times. As stapes fits into the oval window, when it vibrates, the fluid perilymph in the vestibular canal vibrates. These vibrations cause the movement of the basilar membranes which in turn moves the sensory hair cells attached to it creating the nerve impulse. The sound waves transmitted to nerve impulse travel through auditory nerve to auditory cortex in brain. If the vibrations in perilymph are more than needed to stimulate the sensory hair cells, then they can be dissipated through round window into the middle ear and into the pharynx. The variations in the intensity and pitch are determined by the amplitude by which the basilar membrane vibrates and region of the organ of corti that gets stimulated.
Mechanism of balance
The vestibular apparatus of inner ear consist of utriculus, sacculus and semicircular canals. All of them are filled with endolymph. The three semicircular canals are at right angle to each other. Each one has a swelling at one end called ampulla. The semicircular canals open into utriculus where it is connected to the sacculus. The balance receptors are present in the utriculus, sacculus and the ampullae of the semicircular canals. These receptors contain the sensory hair cells which are very sensitive to the position of head with respect to gravity. The three semicircular canals are so arranged that the movement in any plane can be detected by these cells and generate impulse. The impulses are passed on to brain through the auditory nerves. Then we know that the body is not in balance and keep it in balance.
Eye
Eye is photoreceptor organ. Two eyes are situated at the front in the orbital fossae of skull. Eyes are very much important, so they are protected by eye brows and eye lids. Eyes can be moved within the orbit in different directions. The movement of eyes is due to six sets of muscles attached to outer surface of eye ball. They are superior, inferior , medial and lateral rectal muscles and superior and inferior oblique muscles. Eye lashes protect eyes from entering dust particles and germs.
There are presence of glands like meiobomian and lachrymal or tear gland. Meiobomian gland is found at upper inner corner of eye. It secretes oily secretion. This oil holds little tear for lubrication. Lachrymal glands are found at outer corner of eye. Lachrymal glands secrete watery fluid called tear. Tear is salty fluid which keeps conjunctiva moist. Tear is drained into nose through nasolacrimal duct at inner corner of conjunctiva.
Eyes are spherical structure. The diameter is about 2.5 cm. Eyes consist of tissues arranged in three concentric layers.
o Outer layer consists of sclerotic or sclera and cornea
o Middle layer consists of choroids, ciliary body and iris
o Inner layer consists of retina
Sclerotic layer -- it is made up of tough connective tissue. it is white in color and opaque. It forms about 5/6 part of eye ball. Most of its part lies at back. It provides surface for attachment of muscles. It maintains shape and protects inner part.
Cornea -- it is elevated part at the front. It is thin and transparent. It forms about 1/5 part of eye ball. It allows light to pass into eye. Due to curvature, it helps in focusing a real inverted image on retina.
Conjunctiva -- it is very much thin transparent membrane covering the cornea and sclera. It is having blood supply. If injured, it gives red color to the eye.
Choroids-- it is vascularised and pigmented layer. So it provides nourishment to retina. Due to pigmentation, it reduces the reflection of light inside eye.
Ciliary body – it is found at the junction of sclera and cornea. It is also vascularised. There are presence of ciliary muscles. These muscles change shape of lens. Contraction results in more spherical shape and relaxation results in flattened shape. From ciliary body, there arises suspensory ligaments. Suspensory ligaments hold lens in position.
Iris -- it is separated from cornea and forms muscular diaphragm just in front of lens. It is also vascularised. It gives color to eye like black, brown, blue etc.
Pupil -- iris is perforated and the opening is called pupil. The dilated muscle present in iris can control the size of pupil. It controls the amount of light entering the eye. In the bright light the size of pupil becomes smaller and in dim light it becomes larger.
Retina -- it consists of two sub layers, outer pigmented and inner photoreceptor layer. In the photoreceptor layer, there are two types of photosensitive cells, cones and rods. The cones are for discrimination of color hence gives sharp vision. The rods are for formation of image at dim light. Three types of cones are there. One type is stimulated by red end of spectrum, the second one by middle green region and third one by blue violet end. The normal color blind is inability to distinguish between red and green.
Fovea -- it is also known as yellow spot. It is slightly depressed area at middle part of retina. It contains only cones. It forms sharpest image.
Blind spot—at the back of eye, from where the optic nerve enters into the eye is called blind spot. It does not contain cones and rods. If image is formed at blind spot, it can not be seen. No image is formed here.
Lens – it is transparent, biconvex structure held in position by suspensory ligaments. It focuses light on the retina for image formation.
Aqueous chamber -- it is space behind cornea and in front of lens. It is filled with watery fluid called aqueous humour. It nourishes cornea and support lens by its pressure. Behind the lens is large space called vitreous chamber filled with jelly like space called vitreous humour. It supports lens and retina.
Working of eye -- light rays fall on cornea. The light rays pass through pupil, lens. The rays are converged by cornea, aqueous humour lens and vitreous humour. They focus the rays at retina. So a small inverted image of object is formed. The convexity of lens can be changed to bring a sharp focus on retina. The eyes are able to focus distant object as well as near by objects. It is known as accommodation. The eyes are suited for viewing distant objects. To see nearer objects, the lens becomes thicker by contraction of ciliary muscles.
Defects of eyes
Defects of eyes are due to curvature of cornea, change in curvature of lens, size of eye ball and opacity of lens etc.
Normal vision is called emmetropia
Myopia or near sightedness
Nearer objects can be seen clearly but objects at about the distance of 6 meters can not be seen clearly. It is due to large eye ball or high curvature of lens. The rays coming fro distant object are focused in front of retina. It can be corrected by biconcave lens.
Hypermetropia
In this distant objects can be seen but near objects are not seen clearly. It is either due to small eye ball, or low convexity of lens. The rays coming from near objects are focused beyond the retina. Use of biconvex lens can correct it.
Presbyopia
It is also long sightedness. It is developed after the age of 40. It is due to loss of flexibility of lens. It is corrected by use of convex lens.
Astigmatism
The vertical and horizontal bars can not be focused at the same time. It is due to uneven curvature of cornea. For correction, cylindrical lens is used.
Cataract
It is developed after about the age of 60. The lens becomes less transparent. Light rays can not pass and person losses ability to see. No treatment for this, the lens should be removed surgically. The artificial lens should be implanted or spectacles with convex lens should be used.
Glaucoma
If the aqueous humour is secreted more, the intra ocular pressure increases which can cause blindness. If it is detected in time it can be cured.
Night blindness
It is due to deficiency of vitamin A in diet. Vitamin A forms Rhodopsin. It is needed for working of rods in the retina.
Color blindness
It takes place due to absence of certain cone cells. The normal colorblindness is that in which red and green can not be differentiated.
Human reproductive system
The reproductive system in and are distinctly different both in structure and fuction. There are some common terms applied to both.
Primary sex organs or gonads
Testis in
Ovaries in
These organs under go number of changes during development and perform basic functions
1. produce gametes testis -sperms
ovaries -ova
2. as ductless glands secrete hormones
testis - testosterone
ovary - estrogen and progesterone
the development of both of these organs is under the control of gonadotropins FSH and LH from anterior pituitary gland
secondary sex organs
in male, prostate gland, seminal vesicle, vas deferens and penis etc
in female, fallopian tubes, uterus, vagina and mammary glands etc
These organs perform important functions but do not produce gametes. These are associated with primary sex organs. The development growth maintenance is under the control of sex hormones produced by ovaries and testis. Sex hormones responsible for sexual behavior and drives influence development of many other organs and tissues of body.
Accessory or external sex characters
They do not play any direct role in reproduction but are distinct and help to distinguish both sexes.
In male, low pitch voice and distribution of pattern of body hair
In female, high pitch voice and distribution pattern of body hair.
Male reproductive system
The male reproductive system consists of testis, epididymus, duct system and accessory glands.
Testis
These are paired gonads. They produce male gametes sperms and secrete male sex hormones testosterone. These are present or enclosed in a loose fold of skin called scrotum. They are found out side the abdominal cavity, where temp remains 2- 3 C below body temperature that is essential for sperm formation. Each testis is enclosed in a tough capsule known as tunica albugenia and testis consists of large no. of seminiferous tubules. In between the tubules there are specialized cells known as Leydig cells. Seminiferous tubules open into a space inside the testis called rete testis. From this space a no. of small, very fine tubules called vasa efferentia arise. These vasa efferentia fuse in the head of epididymus.
Epididymus
Single highly coiled tube about 5 meters long. Sperms formed in the seminiferous tubules pass through vasa efferentia and they are stored in the epididymus. Sperms get concentrated and maturity and mobility in epididymus. Epididymus leads into vas deferens.
Vas deferens
It is short straight tube. It ascends into abdominal cavity. It loops over the urinary bladder and opens into common urethra. Urethra passes through penis and opens at tip of penis.
Penis
It is made up of spongy muscular tissue. This tissue when filled with blood causes erection and enlargement of the organ. The tip of penis (glans) is highly sensitive. Sexual excitement can cause the erection of penis. Vessels are dilated to collect blood in spongy tissue. As tissue become distended, it compresses the vein so as to inhibit flow of blood out of tissue. With continued stimulation the penis and underlying bulb become hard and enlarged.
The penis consists of 3 columns of spongy tissue, 2 columns of corpora cavernosa above and 1 column of corpus spongiosum below. Corpus spongiosum includes the urethra. The tip of glans is slightly enlarge. It is covered by fold of skin called prepuce. The function of penis is to deposit semen in the genital tract of female.
Female reproductive system
Consists of ovary, oviducts, uterus, vagina, vulva and accessory glands.
Ovary -- paired structure, dark coloured and held in position by ligaments( mesovarium. Situated in abdominal cavity, one on either side of vertebral coloumn behind kidneys.
Each ovary is lined by germinal epithelium. The inner mass of fibrous connective tissue is called stroma. Stroma contains blood capillaries and nerve fibers and ovarian follicles etc. ovarian follicles develop from germinal epithelial cells. A marured follicle is called Graafian follicle. Outer membrane of Graafian follicle is membrane granulose. There is fluid filled cavity called antrum. In this cavity there lies ovum. The ovum is surrounded by Zona pellucida or zona radiata
The Graafian follicle finally ruptures to release mature egg into surrounding peritoneal cavity. It is picked up by fimbriated opening of fallopian tube. The follicle cells with blood clot forms corpus luteum.
The duct system-- consists of 2 fallopian tubes, uterus and vagina.
Fallopian tubes or oviducts. These ducts have a funnel shaped fimbriated opening to receive eggs as they mature. The ciliated funnel leads distally into a long narrow and convoluted tubule called fallopian tube. It has infundibulum which is fimbriated, ampulla, wide part where fertilization takes place, isthimus, narrow and straight part. Its walls are contractile and lined internally with ciliated epithelium. These cilia help egg to move towards uterus.
Uterus – 2, fallopian tube open into a thick walled muscular organ called uterus. The inner wall of uterus is called endometrium. Endometrium is richly supplied with blood vessels and glands. Upper dome shaped part is Fundus, broad above and narrow below is body, The lower tip of uterus is called cervix where there is opening internal os and opening below external os opens to vagina
Vagina -- it is a large fibromuscular chamber ( tube) that runs from uterus to outside. The fibro muscular chamber is lined by stratified epithelium. It opens outside by vulva.
Females have separate urethral and vaginal openings unlike males. At vaginal orifice, partially covered membrane in vergin called hymen. Epithelial cells produce glycogen, anaerobic oxidation of which produce lactic acid for protection from infection.
Vulva is guarded by two folds of tissue labia majora and labia minora.
Clitoris present analogous to penis in male.
Glands
bertholin’s gland one pair,similar to cowper’s gland
The secretion of bertholin’s gland is viscid fluid that makes the vaginal passage slippery needed at the time of intercourse.
Mammary gland one pair, located at chest region. The development of mammary gland is influenced by female sex hormone. The production of milk is due to another hormone called prolactin. The release of milk is due to oxytocin hormone soon after the birth of child.
Process of fertilization
During the sexual intercourse, ejaculation takes place in which semen is deposited in the vagina of female called orgasm. Due to the contraction of vaginal passage, sperms move up into the uterus and fallopian tube. If they find the ovum, the wall of ovum dissolved by the sperm lysine of large no. of sperms. Then one sperm pierces the ovum and fuses with the ovum. It results into the formation of zygote. It is implanted into the wall of uterus known as endometrium.
Menstrual cycle
Cyclic changes occur with periodicity of 28 days. Starts about the age of 9- 10, continues to about the age of 50. No cycle during pregnancy. Starts again after few months of child birth. Stoppage of cycle at old age menopause, which shows incapability of woman of reproduction.
Menstrual phase
o lasts for about first 3- 5 days.
o Breaking down of endometrium , epithelium lining, connective tissue blood vessels slashed off and discharge as menstruation.
o Estrogen and progesterone very low.
o Weeping of uterus
Proliferative phase
o it remains for 5th to 14th day, it lasts for about 9 or 10 days till ovulation.
o Begins with repair of damaged endometrium
o Induced by FSH, also follicular phase – one egg matures in each cycle.
o Primary oocyte undergoes first meiotic div, and changed into sec oocyte forms Graafian follicle.
o Estrogen secreted by Graafian follicle, its level increases, becomes maximum about 3 days before ovulation.
o Estrogen causes thickening of endometrium and develop blood vessels in it.
o Uterine movement increase due to contraction of uterine muscles.
Ovulation phase
o One matured egg is released from the Graafian follicle on the 14th day.
o Corpus luteum is formed by ruptured follicle also called yellow body.
Secretory phase
o Lasts for 12 -14 days, from 15th to 28th day.
o Induced by LH also called Luteal phase.
o Corpus luteum releases Progesterone, causes further thickenings of endometrium for implantation.
o Under its influence, tubular glands secrete mucus, uterus becomes fluid filled and glandular.
o Uterine movement decrease considerably.
o Progesterone inhibits further maturation of any follicle or ovulation from ovary.
o If ovum is not fertilized, corpus luteum degenerates, level of both estrogen and progesterone decrease at about 28th day.
Ear is stato acoustic organ. It is responsible for sensations of equilibrium and hearing. It is sensitive to frequencies of sound waves and to change in relation with gravity. There are two ears and are situated one on either side of head.
Each ear consists of three main parts.
External ear
Middle ear
Internal ear
External ear -- it consists of pinna, auditory canal and tympanic membrane or ear drum. It is air filled cavity. It receives or collects sound waves and directs he sound waves to middle ear.
Pinnae-- these are flap of tissue supported by cartilages. These are found one on either side of head. these are immovable. Thee is presence of small opening that leads into auditory canal. It collects the sound waves and sends it to auditory canal.
Autitory canal -- it is also known as ear tube or external auditory meatus. It is lined by skin which has hairs for protection. Glands are preset to secret brown wax. If more and more wax is collected, it may cause deafness. It ends in eardrum.
Tympanic membrane-- it is also known as ear drum. It is thin sheet of tissue. it is delicate, membranous structure. It vibrates in response to the sound waves. It transmits sound waves to middle ear.
Middle ear - - it is also air filled cavity. It consist of three tiny bones called ear ossicles . thjey are malleus, incus and stapes, ear ossicles move forward and backward in resplonse to vibrations of ear drum.
Malllleus -- it is hammer shaped and articulate with incus on the other side.
Incus-- it is anvil like structure articulating with malleus on one side and stapes on other side.
Stapes -- it is stirrup like. Its foot plate or base is attached to oval window called fenestra ovalis or fenestra vestibule. These three ear ossicles are arranged in lever like action. They magnify and transfer the vibrations from ear drum to cochlea of inner ear through oval window.
Eustachian tube – it is a tube that leads from pharynx to middle ear. It helps in equalizing air pressure on both sides of ear drum. When air pressure is unequal, the ear drum becomes more stretched and can cause pain.
Inner ear -- it is fluid filled chamber it consists of complex system of canals and cavities. It basically consists of cochlea (associated with hearing) and vestibular apparatus( associated with balance)
Cochlea -- it is a highly coiled tube about 35 mm in length. It has got three canals inside, the vestibular canal, middle canal and tympanic canal. The reissner’s membrane separates the vestibular and middle canal. Similarly basilar membrane separates middle and tympanic canal. Both vestibular and tympanic canal are filled with fluid called perilymph. The vestibular canal is connected to oval window on the other side of which stapes is attached. The tympanic canal is connected to round window. The middle canal is filled with endolymph. There is basilar membrane on one side. The sensory hair cells rest on this basilar membrane. These cells are in contact with tectorial membrane above . the tectorial membrane, sensory hair cells and basilar membrane together form the organ of corti. The organ of corti can generate the sound impulse and send it to brain through auditory nerve.
Mechanism of hearing
As the sound waves enter the external ear, they pass through canal and strike the ear drum. The vibrations of ear drum are transmitted to three ear ossicles which magnify them 20 to 25 times. As stapes fits into the oval window, when it vibrates, the fluid perilymph in the vestibular canal vibrates. These vibrations cause the movement of the basilar membranes which in turn moves the sensory hair cells attached to it creating the nerve impulse. The sound waves transmitted to nerve impulse travel through auditory nerve to auditory cortex in brain. If the vibrations in perilymph are more than needed to stimulate the sensory hair cells, then they can be dissipated through round window into the middle ear and into the pharynx. The variations in the intensity and pitch are determined by the amplitude by which the basilar membrane vibrates and region of the organ of corti that gets stimulated.
Mechanism of balance
The vestibular apparatus of inner ear consist of utriculus, sacculus and semicircular canals. All of them are filled with endolymph. The three semicircular canals are at right angle to each other. Each one has a swelling at one end called ampulla. The semicircular canals open into utriculus where it is connected to the sacculus. The balance receptors are present in the utriculus, sacculus and the ampullae of the semicircular canals. These receptors contain the sensory hair cells which are very sensitive to the position of head with respect to gravity. The three semicircular canals are so arranged that the movement in any plane can be detected by these cells and generate impulse. The impulses are passed on to brain through the auditory nerves. Then we know that the body is not in balance and keep it in balance.
Eye
Eye is photoreceptor organ. Two eyes are situated at the front in the orbital fossae of skull. Eyes are very much important, so they are protected by eye brows and eye lids. Eyes can be moved within the orbit in different directions. The movement of eyes is due to six sets of muscles attached to outer surface of eye ball. They are superior, inferior , medial and lateral rectal muscles and superior and inferior oblique muscles. Eye lashes protect eyes from entering dust particles and germs.
There are presence of glands like meiobomian and lachrymal or tear gland. Meiobomian gland is found at upper inner corner of eye. It secretes oily secretion. This oil holds little tear for lubrication. Lachrymal glands are found at outer corner of eye. Lachrymal glands secrete watery fluid called tear. Tear is salty fluid which keeps conjunctiva moist. Tear is drained into nose through nasolacrimal duct at inner corner of conjunctiva.
Eyes are spherical structure. The diameter is about 2.5 cm. Eyes consist of tissues arranged in three concentric layers.
o Outer layer consists of sclerotic or sclera and cornea
o Middle layer consists of choroids, ciliary body and iris
o Inner layer consists of retina
Sclerotic layer -- it is made up of tough connective tissue. it is white in color and opaque. It forms about 5/6 part of eye ball. Most of its part lies at back. It provides surface for attachment of muscles. It maintains shape and protects inner part.
Cornea -- it is elevated part at the front. It is thin and transparent. It forms about 1/5 part of eye ball. It allows light to pass into eye. Due to curvature, it helps in focusing a real inverted image on retina.
Conjunctiva -- it is very much thin transparent membrane covering the cornea and sclera. It is having blood supply. If injured, it gives red color to the eye.
Choroids-- it is vascularised and pigmented layer. So it provides nourishment to retina. Due to pigmentation, it reduces the reflection of light inside eye.
Ciliary body – it is found at the junction of sclera and cornea. It is also vascularised. There are presence of ciliary muscles. These muscles change shape of lens. Contraction results in more spherical shape and relaxation results in flattened shape. From ciliary body, there arises suspensory ligaments. Suspensory ligaments hold lens in position.
Iris -- it is separated from cornea and forms muscular diaphragm just in front of lens. It is also vascularised. It gives color to eye like black, brown, blue etc.
Pupil -- iris is perforated and the opening is called pupil. The dilated muscle present in iris can control the size of pupil. It controls the amount of light entering the eye. In the bright light the size of pupil becomes smaller and in dim light it becomes larger.
Retina -- it consists of two sub layers, outer pigmented and inner photoreceptor layer. In the photoreceptor layer, there are two types of photosensitive cells, cones and rods. The cones are for discrimination of color hence gives sharp vision. The rods are for formation of image at dim light. Three types of cones are there. One type is stimulated by red end of spectrum, the second one by middle green region and third one by blue violet end. The normal color blind is inability to distinguish between red and green.
Fovea -- it is also known as yellow spot. It is slightly depressed area at middle part of retina. It contains only cones. It forms sharpest image.
Blind spot—at the back of eye, from where the optic nerve enters into the eye is called blind spot. It does not contain cones and rods. If image is formed at blind spot, it can not be seen. No image is formed here.
Lens – it is transparent, biconvex structure held in position by suspensory ligaments. It focuses light on the retina for image formation.
Aqueous chamber -- it is space behind cornea and in front of lens. It is filled with watery fluid called aqueous humour. It nourishes cornea and support lens by its pressure. Behind the lens is large space called vitreous chamber filled with jelly like space called vitreous humour. It supports lens and retina.
Working of eye -- light rays fall on cornea. The light rays pass through pupil, lens. The rays are converged by cornea, aqueous humour lens and vitreous humour. They focus the rays at retina. So a small inverted image of object is formed. The convexity of lens can be changed to bring a sharp focus on retina. The eyes are able to focus distant object as well as near by objects. It is known as accommodation. The eyes are suited for viewing distant objects. To see nearer objects, the lens becomes thicker by contraction of ciliary muscles.
Defects of eyes
Defects of eyes are due to curvature of cornea, change in curvature of lens, size of eye ball and opacity of lens etc.
Normal vision is called emmetropia
Myopia or near sightedness
Nearer objects can be seen clearly but objects at about the distance of 6 meters can not be seen clearly. It is due to large eye ball or high curvature of lens. The rays coming fro distant object are focused in front of retina. It can be corrected by biconcave lens.
Hypermetropia
In this distant objects can be seen but near objects are not seen clearly. It is either due to small eye ball, or low convexity of lens. The rays coming from near objects are focused beyond the retina. Use of biconvex lens can correct it.
Presbyopia
It is also long sightedness. It is developed after the age of 40. It is due to loss of flexibility of lens. It is corrected by use of convex lens.
Astigmatism
The vertical and horizontal bars can not be focused at the same time. It is due to uneven curvature of cornea. For correction, cylindrical lens is used.
Cataract
It is developed after about the age of 60. The lens becomes less transparent. Light rays can not pass and person losses ability to see. No treatment for this, the lens should be removed surgically. The artificial lens should be implanted or spectacles with convex lens should be used.
Glaucoma
If the aqueous humour is secreted more, the intra ocular pressure increases which can cause blindness. If it is detected in time it can be cured.
Night blindness
It is due to deficiency of vitamin A in diet. Vitamin A forms Rhodopsin. It is needed for working of rods in the retina.
Color blindness
It takes place due to absence of certain cone cells. The normal colorblindness is that in which red and green can not be differentiated.
Human reproductive system
The reproductive system in and are distinctly different both in structure and fuction. There are some common terms applied to both.
Primary sex organs or gonads
Testis in
Ovaries in
These organs under go number of changes during development and perform basic functions
1. produce gametes testis -sperms
ovaries -ova
2. as ductless glands secrete hormones
testis - testosterone
ovary - estrogen and progesterone
the development of both of these organs is under the control of gonadotropins FSH and LH from anterior pituitary gland
secondary sex organs
in male, prostate gland, seminal vesicle, vas deferens and penis etc
in female, fallopian tubes, uterus, vagina and mammary glands etc
These organs perform important functions but do not produce gametes. These are associated with primary sex organs. The development growth maintenance is under the control of sex hormones produced by ovaries and testis. Sex hormones responsible for sexual behavior and drives influence development of many other organs and tissues of body.
Accessory or external sex characters
They do not play any direct role in reproduction but are distinct and help to distinguish both sexes.
In male, low pitch voice and distribution of pattern of body hair
In female, high pitch voice and distribution pattern of body hair.
Male reproductive system
The male reproductive system consists of testis, epididymus, duct system and accessory glands.
Testis
These are paired gonads. They produce male gametes sperms and secrete male sex hormones testosterone. These are present or enclosed in a loose fold of skin called scrotum. They are found out side the abdominal cavity, where temp remains 2- 3 C below body temperature that is essential for sperm formation. Each testis is enclosed in a tough capsule known as tunica albugenia and testis consists of large no. of seminiferous tubules. In between the tubules there are specialized cells known as Leydig cells. Seminiferous tubules open into a space inside the testis called rete testis. From this space a no. of small, very fine tubules called vasa efferentia arise. These vasa efferentia fuse in the head of epididymus.
Epididymus
Single highly coiled tube about 5 meters long. Sperms formed in the seminiferous tubules pass through vasa efferentia and they are stored in the epididymus. Sperms get concentrated and maturity and mobility in epididymus. Epididymus leads into vas deferens.
Vas deferens
It is short straight tube. It ascends into abdominal cavity. It loops over the urinary bladder and opens into common urethra. Urethra passes through penis and opens at tip of penis.
Penis
It is made up of spongy muscular tissue. This tissue when filled with blood causes erection and enlargement of the organ. The tip of penis (glans) is highly sensitive. Sexual excitement can cause the erection of penis. Vessels are dilated to collect blood in spongy tissue. As tissue become distended, it compresses the vein so as to inhibit flow of blood out of tissue. With continued stimulation the penis and underlying bulb become hard and enlarged.
The penis consists of 3 columns of spongy tissue, 2 columns of corpora cavernosa above and 1 column of corpus spongiosum below. Corpus spongiosum includes the urethra. The tip of glans is slightly enlarge. It is covered by fold of skin called prepuce. The function of penis is to deposit semen in the genital tract of female.
Female reproductive system
Consists of ovary, oviducts, uterus, vagina, vulva and accessory glands.
Ovary -- paired structure, dark coloured and held in position by ligaments( mesovarium. Situated in abdominal cavity, one on either side of vertebral coloumn behind kidneys.
Each ovary is lined by germinal epithelium. The inner mass of fibrous connective tissue is called stroma. Stroma contains blood capillaries and nerve fibers and ovarian follicles etc. ovarian follicles develop from germinal epithelial cells. A marured follicle is called Graafian follicle. Outer membrane of Graafian follicle is membrane granulose. There is fluid filled cavity called antrum. In this cavity there lies ovum. The ovum is surrounded by Zona pellucida or zona radiata
The Graafian follicle finally ruptures to release mature egg into surrounding peritoneal cavity. It is picked up by fimbriated opening of fallopian tube. The follicle cells with blood clot forms corpus luteum.
The duct system-- consists of 2 fallopian tubes, uterus and vagina.
Fallopian tubes or oviducts. These ducts have a funnel shaped fimbriated opening to receive eggs as they mature. The ciliated funnel leads distally into a long narrow and convoluted tubule called fallopian tube. It has infundibulum which is fimbriated, ampulla, wide part where fertilization takes place, isthimus, narrow and straight part. Its walls are contractile and lined internally with ciliated epithelium. These cilia help egg to move towards uterus.
Uterus – 2, fallopian tube open into a thick walled muscular organ called uterus. The inner wall of uterus is called endometrium. Endometrium is richly supplied with blood vessels and glands. Upper dome shaped part is Fundus, broad above and narrow below is body, The lower tip of uterus is called cervix where there is opening internal os and opening below external os opens to vagina
Vagina -- it is a large fibromuscular chamber ( tube) that runs from uterus to outside. The fibro muscular chamber is lined by stratified epithelium. It opens outside by vulva.
Females have separate urethral and vaginal openings unlike males. At vaginal orifice, partially covered membrane in vergin called hymen. Epithelial cells produce glycogen, anaerobic oxidation of which produce lactic acid for protection from infection.
Vulva is guarded by two folds of tissue labia majora and labia minora.
Clitoris present analogous to penis in male.
Glands
bertholin’s gland one pair,similar to cowper’s gland
The secretion of bertholin’s gland is viscid fluid that makes the vaginal passage slippery needed at the time of intercourse.
Mammary gland one pair, located at chest region. The development of mammary gland is influenced by female sex hormone. The production of milk is due to another hormone called prolactin. The release of milk is due to oxytocin hormone soon after the birth of child.
Process of fertilization
During the sexual intercourse, ejaculation takes place in which semen is deposited in the vagina of female called orgasm. Due to the contraction of vaginal passage, sperms move up into the uterus and fallopian tube. If they find the ovum, the wall of ovum dissolved by the sperm lysine of large no. of sperms. Then one sperm pierces the ovum and fuses with the ovum. It results into the formation of zygote. It is implanted into the wall of uterus known as endometrium.
Menstrual cycle
Cyclic changes occur with periodicity of 28 days. Starts about the age of 9- 10, continues to about the age of 50. No cycle during pregnancy. Starts again after few months of child birth. Stoppage of cycle at old age menopause, which shows incapability of woman of reproduction.
Menstrual phase
o lasts for about first 3- 5 days.
o Breaking down of endometrium , epithelium lining, connective tissue blood vessels slashed off and discharge as menstruation.
o Estrogen and progesterone very low.
o Weeping of uterus
Proliferative phase
o it remains for 5th to 14th day, it lasts for about 9 or 10 days till ovulation.
o Begins with repair of damaged endometrium
o Induced by FSH, also follicular phase – one egg matures in each cycle.
o Primary oocyte undergoes first meiotic div, and changed into sec oocyte forms Graafian follicle.
o Estrogen secreted by Graafian follicle, its level increases, becomes maximum about 3 days before ovulation.
o Estrogen causes thickening of endometrium and develop blood vessels in it.
o Uterine movement increase due to contraction of uterine muscles.
Ovulation phase
o One matured egg is released from the Graafian follicle on the 14th day.
o Corpus luteum is formed by ruptured follicle also called yellow body.
Secretory phase
o Lasts for 12 -14 days, from 15th to 28th day.
o Induced by LH also called Luteal phase.
o Corpus luteum releases Progesterone, causes further thickenings of endometrium for implantation.
o Under its influence, tubular glands secrete mucus, uterus becomes fluid filled and glandular.
o Uterine movement decrease considerably.
o Progesterone inhibits further maturation of any follicle or ovulation from ovary.
o If ovum is not fertilized, corpus luteum degenerates, level of both estrogen and progesterone decrease at about 28th day.
Sunday, March 6, 2011
for touchstone 2011
The Living World
Raghubar Shrestha
Associate Prof. of Zoology,
HoD, Biology Department
Plants and animals have been surviving on this earth for time immemorial. They had different forms, shapes and structures. They are all, the part of the living world. They are all living a life and one question is often asked. What is life? It’s very difficult to answer. However, biologists have come across the suitable answer to this question. Life can generate energy within its body, use energy for carrying out various activities. Living things move about except the developed plants. They grow in size, take food, respire, excrete, undergo reproduction, and respond to the external stimuli. The use of energy within their body is in various forms like heat energy to keep their body warm. Certain fire worms can produce light, certain fishes can produce electric current. Most of the vertebrates can produce sound energy. On the other hands, non living things cannot use energy. Still it cannot be said that, non living things do not have energy. We have the example from the ancient period. Just by striking two stones, the ancestors of man produced fire. The stone at the top of the mountain has the potential energy. Similarly , the water in the pond has potential energy. Any time, the stone and water can go into movement and potential energy is changed into kinetic energy. The non living things move on and on until a force is applied to stop them.
When living things move, they can stop by themselves. They have internal force which can stop them from moving ahead. The life can be compared with some sort of movement. To remain idle is nearly death. The young children move here and there the whole day. More the movements, there is more life, many years to live. As we grow, movements slow down and down. At the very old age, the movement is very less and it means the death is very much near.
Before we born, or say, before we start our life, the sperms swim around the relatively stationary ovum. The sperms are always in movement. It is due to movement that the sperms find ovum and one of the sperms quickly fertilizes it. After the fertilization, the zygote is formed in all sexually reproducing organisms. This is the beginning of the life. Not only living things, the stars, the planets, the moons in the space are all the time in movement. In the smallest particle, the atom, we can see the electrons are in movements. The electrons are moving around the nucleus in their own orbit. The water, the air what are not in movement?
Inside the body of living organisms, the heart is pumping blood twenty-four hours a day. The circulation of blood is associated with life. Once the circulation of blood is ceased, there is no life. Similarly, the breathing movements are continuous process. At different parts of body, muscles are present. They can contract and expand. Actually, these muscles help in the movements of fluid and waste materials from one part to another part of the body. Because of such movements, urine and undigested wastes etc can be discharged from the body. Similarly, the sperms and ova in male and female are carried down the duct system for fertilization. The muscles contract and expand to secrete the juices and enzymes in the body so that foods can be digested properly. During the proliferative phase in the menstrual cycle in females, there is contraction in the wall of uterus which can help in the ascending movement of the sperms to find the ova. In the working of nervous system, the impulses are carried at the faster rate along the nerve fiber to the brain and various information from brain to the target organ. All these are one or other form of movements.
Again, not only the movements in side body, the muscles help in the movement of parts of the body or whole body, which is the external movement. The movement or locomotion of these animals are needed to find their food, to protect themselves from various types of enemies, to move to suitable environment as well as to find the sexual partner and to find the safer place to rear their young ones. They cannot remain moving here and there. In wild animals, they need certain area to move about for their reproduction. Still, many fishes and birds migrate for months and to a longer distances. Such migration in these animals are of great importance to get all the available facilities for proliferation of their race.
Besides, in the birds and mammals, there are movements used for communication among the members of various animals. In the Primates of Class Mammalia like monkeys, apes and man, facial expressions are seen. They can actively show the expression of happiness or sorrow by facial expression. For this, there are number of muscles in their face. By the movements of these muscle, the facial expression is possible. The eye movements are so important in communication that one can read the eyes to know many things. The blinking of eye is necessary for proper functioning of eye. Inside the ear of animal, there are three ear ossicles namely malleus, incus and stapes. They are heavily built and joined like in the lever. By their movements, magnify the sound waves and pass to the internal ear. Such movements help in the process of hearing. The movements in the parts of our body can help a great in the non verbal communication.
Though, we cannot see the locomotion in higher plants like the trees, bushes and herbs, there are the movements of water as well as of food they prepare in their leaves from one part to another part of their body. Transpiration is a continuous process, in which plants absorb water from the soil and excess water is lost from the leaves in the form of vapor. Most of the plants usually move towards the source of light. They need the light for manufacturing their food. Photosynthesis is the process in which plants absorb CO2 from atmosphere and water from soil and then in the presence of light chlorophyll can manufacture food.
In case of plants, the movement or transfer of pollen grains into the stigma of gynoeceium in the same flower or to the other flower in the another plant, is assisted by air, water, honey bees or other animals. There will be no fertilization and growth in plants without such movements.
In the non living things also, there are movements. The electric current moves from higher potential to lower potential. The air is always moving from higher pressure to lower pressure. The moving air takes the clouds from one part to another part. There is the water cycle. The water evaporates from the sea, clouds taken to the mountains by air and causes rainfall. The water in the brooks, rivers etc are always running which can support various lives at different parts of the world. Not only these, there are Carbon cycle, Nitrogen cycle, Phosphorus cycle etc. all these chemicals are moving from one part to another part helping all the living animals and plants in their survival.
Speed of some of the living and non living objects
Light 299792.458 Kilometer/second
Concord jet 594.44 meter/second
Sound 340.29 meter/second at sea level
Nerve impulse 120 meter/second
Fast train 111.1 meter/second
Cheetah 31.1 meter/second
Usual speed of running being 22.2 meter/second
Motor cycle 11.1 meter/second
A brisk walk of man 1.1 meter/second
A Rocket needs a velocity of 11.2 Kilometer/second to leave the earth if projected directly at perpendicular to the earth surface. From the above table, it seems that light travels the fastest of all, far more than that of Rocket. But still, the human mind can travel faster than the light.
The Sun, the various planets like Earth, Jupiter and Saturn etc are moving in their own orbit to balance the gravitational force. As the Earth goes round the Sun, there are the days and nights and different seasons throughout the year. The plants and animals have various activities according to the day length and different seasons like winter, spring, summer and autumn etc. They become inactive during winter and summer and active during spring, rainy season and autumn.
From all the things above, it is obvious that the life and movements are so much associated that there will be no life without movements in living as well as non living things. The movement is a kind of kinetic energy. All the living organism live using one or another form of energy and the movement or locomotion is of great importance in the act of living in this world.
Raghubar Shrestha
Associate Prof. of Zoology,
HoD, Biology Department
Plants and animals have been surviving on this earth for time immemorial. They had different forms, shapes and structures. They are all, the part of the living world. They are all living a life and one question is often asked. What is life? It’s very difficult to answer. However, biologists have come across the suitable answer to this question. Life can generate energy within its body, use energy for carrying out various activities. Living things move about except the developed plants. They grow in size, take food, respire, excrete, undergo reproduction, and respond to the external stimuli. The use of energy within their body is in various forms like heat energy to keep their body warm. Certain fire worms can produce light, certain fishes can produce electric current. Most of the vertebrates can produce sound energy. On the other hands, non living things cannot use energy. Still it cannot be said that, non living things do not have energy. We have the example from the ancient period. Just by striking two stones, the ancestors of man produced fire. The stone at the top of the mountain has the potential energy. Similarly , the water in the pond has potential energy. Any time, the stone and water can go into movement and potential energy is changed into kinetic energy. The non living things move on and on until a force is applied to stop them.
When living things move, they can stop by themselves. They have internal force which can stop them from moving ahead. The life can be compared with some sort of movement. To remain idle is nearly death. The young children move here and there the whole day. More the movements, there is more life, many years to live. As we grow, movements slow down and down. At the very old age, the movement is very less and it means the death is very much near.
Before we born, or say, before we start our life, the sperms swim around the relatively stationary ovum. The sperms are always in movement. It is due to movement that the sperms find ovum and one of the sperms quickly fertilizes it. After the fertilization, the zygote is formed in all sexually reproducing organisms. This is the beginning of the life. Not only living things, the stars, the planets, the moons in the space are all the time in movement. In the smallest particle, the atom, we can see the electrons are in movements. The electrons are moving around the nucleus in their own orbit. The water, the air what are not in movement?
Inside the body of living organisms, the heart is pumping blood twenty-four hours a day. The circulation of blood is associated with life. Once the circulation of blood is ceased, there is no life. Similarly, the breathing movements are continuous process. At different parts of body, muscles are present. They can contract and expand. Actually, these muscles help in the movements of fluid and waste materials from one part to another part of the body. Because of such movements, urine and undigested wastes etc can be discharged from the body. Similarly, the sperms and ova in male and female are carried down the duct system for fertilization. The muscles contract and expand to secrete the juices and enzymes in the body so that foods can be digested properly. During the proliferative phase in the menstrual cycle in females, there is contraction in the wall of uterus which can help in the ascending movement of the sperms to find the ova. In the working of nervous system, the impulses are carried at the faster rate along the nerve fiber to the brain and various information from brain to the target organ. All these are one or other form of movements.
Again, not only the movements in side body, the muscles help in the movement of parts of the body or whole body, which is the external movement. The movement or locomotion of these animals are needed to find their food, to protect themselves from various types of enemies, to move to suitable environment as well as to find the sexual partner and to find the safer place to rear their young ones. They cannot remain moving here and there. In wild animals, they need certain area to move about for their reproduction. Still, many fishes and birds migrate for months and to a longer distances. Such migration in these animals are of great importance to get all the available facilities for proliferation of their race.
Besides, in the birds and mammals, there are movements used for communication among the members of various animals. In the Primates of Class Mammalia like monkeys, apes and man, facial expressions are seen. They can actively show the expression of happiness or sorrow by facial expression. For this, there are number of muscles in their face. By the movements of these muscle, the facial expression is possible. The eye movements are so important in communication that one can read the eyes to know many things. The blinking of eye is necessary for proper functioning of eye. Inside the ear of animal, there are three ear ossicles namely malleus, incus and stapes. They are heavily built and joined like in the lever. By their movements, magnify the sound waves and pass to the internal ear. Such movements help in the process of hearing. The movements in the parts of our body can help a great in the non verbal communication.
Though, we cannot see the locomotion in higher plants like the trees, bushes and herbs, there are the movements of water as well as of food they prepare in their leaves from one part to another part of their body. Transpiration is a continuous process, in which plants absorb water from the soil and excess water is lost from the leaves in the form of vapor. Most of the plants usually move towards the source of light. They need the light for manufacturing their food. Photosynthesis is the process in which plants absorb CO2 from atmosphere and water from soil and then in the presence of light chlorophyll can manufacture food.
In case of plants, the movement or transfer of pollen grains into the stigma of gynoeceium in the same flower or to the other flower in the another plant, is assisted by air, water, honey bees or other animals. There will be no fertilization and growth in plants without such movements.
In the non living things also, there are movements. The electric current moves from higher potential to lower potential. The air is always moving from higher pressure to lower pressure. The moving air takes the clouds from one part to another part. There is the water cycle. The water evaporates from the sea, clouds taken to the mountains by air and causes rainfall. The water in the brooks, rivers etc are always running which can support various lives at different parts of the world. Not only these, there are Carbon cycle, Nitrogen cycle, Phosphorus cycle etc. all these chemicals are moving from one part to another part helping all the living animals and plants in their survival.
Speed of some of the living and non living objects
Light 299792.458 Kilometer/second
Concord jet 594.44 meter/second
Sound 340.29 meter/second at sea level
Nerve impulse 120 meter/second
Fast train 111.1 meter/second
Cheetah 31.1 meter/second
Usual speed of running being 22.2 meter/second
Motor cycle 11.1 meter/second
A brisk walk of man 1.1 meter/second
A Rocket needs a velocity of 11.2 Kilometer/second to leave the earth if projected directly at perpendicular to the earth surface. From the above table, it seems that light travels the fastest of all, far more than that of Rocket. But still, the human mind can travel faster than the light.
The Sun, the various planets like Earth, Jupiter and Saturn etc are moving in their own orbit to balance the gravitational force. As the Earth goes round the Sun, there are the days and nights and different seasons throughout the year. The plants and animals have various activities according to the day length and different seasons like winter, spring, summer and autumn etc. They become inactive during winter and summer and active during spring, rainy season and autumn.
From all the things above, it is obvious that the life and movements are so much associated that there will be no life without movements in living as well as non living things. The movement is a kind of kinetic energy. All the living organism live using one or another form of energy and the movement or locomotion is of great importance in the act of living in this world.
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