Tissues in Action: Class 9 Science Chapter 3 Hinglish mein

Kuch bhige hue moong ke daane geele kapde par chhod do, aur do din ke andar har daane se ek safed root bahar nikal aati hai. Ek naya paida hua baby lagbhag 3 kg ka hota hai, aur uska har gram, palkon se lekar pair ke naakhoon tak, ek hi fertilised cell se bana hai. Ek cell arabon cells ban jaata hai. Phir yeh arabon cells ek doosre se itne alag kaise ho jaate hain?

Do cheezein saath-saath hoti hain. Cells baar-baar divide hote hain, isliye unki ginti badhti hai. Phir naye cells ke groups badal jaate hain: woh khaas shapes le lete hain aur khaas kaamon mein lag jaate hain. Apne muh ki lining ke chapte cells, jaangh ki haddi ke sakht walls wale cells aur nerves ke dhaage jaise cells ke baare mein socho. Yeh sab usi pehle cell se aaye hain, phir bhi ek doosre se bilkul alag dikhte hain. Cells kaise specialise hote hain, yeh jaanne se doctors jale hue patients ke liye skin uga paate hain aur farmers kuch hi cells se hazaaron healthy plants ugaa paate hain.

Chapter 2 mein tumne cell padha tha, jo life ki basic unit hai. Amoeba ek single cell hai jo apna sab kaam khud karta hai: khaana leta hai, chalta hai, saans leta hai, waste bahar nikaalta hai aur divide hota hai. Ek many-celled organism yeh kaam baant deta hai. Structure mein milte-julte cells groups mein ikatthe hote hain, aur har group ek kaam sambhalta hai. Aise group ko tissue (ऊतक) kehte hain.

Tissues ek seedhi ka sirf ek paayadaan hain (Fig. 3.1). Kai tissues milkar ek organ banate hain, jaise leaf ya stomach. Ek hi kaam karne wale organs ek organ system banate hain, jaise plant ka shoot ya hamara digestive system. Saare organ systems milkar organism banate hain.

Kaam ko is tarah baantna division of labour kehlata hai, aur iska fayda hota hai. Jis tissue ka sirf ek kaam ho, use us kaam ke liye perfect banaya ja sakta hai, isliye poori body zyada efficiently chalti hai. Messages nervous tissue ke through tumhari body mein tezi se daudte hain, jabki muscle tissue kheechne ka kaam karta hai. Plant apna transport do tissues mein baant deta hai: paani aur minerals ke liye xylem aur khaane ke liye phloem.

3.1 Plant aur Animal Tissues Alag Kyun Hote Hain?

Ek neem ke tree aur uske neeche ghaas charti ek bakri ke baare mein socho. Tree apni poori zindagi ek hi jagah bitata hai. Use hawa aur monsoon ki baarish ke saamne seedha khada rehna hai aur apni leaves ko roshni ki taraf upar uthaye rakhna hai. Chapter 2 mein tumne dekha tha ki plant cells mein ek sakht cell wall hoti hai, jo yahan madad karti hai. Plant ki body ka bada hissa supporting tissue hota hai, aur us tissue ka bada hissa moti walls wale dead cells se bana hota hai. Wood iska sabse jaana-maana example hai.

Bakri alag tarah se jeeti hai. Woh ghaas dhoondhne ke liye chalti hai, khatre se bhaagti hai aur idhar-udhar dekhne ke liye sir ghumati hai. Uske cells mein wall nahi hoti, isliye woh apni shape badal sakte hain, aur uske tissues stretch ho sakte hain, mud sakte hain aur contract ho sakte hain (Fig. 3.2). Zyadatar animal tissues living hote hain. Haan, har animal ghoomta-phirta nahi: sponge apni adult life ek chattaan se chipak kar bitata hai.

Unki growth ke rules bhi alag hain. Neem jab tak jeeta hai, height aur motaai badhata rehta hai, lekin sirf kuch khaas growing regions se. Bakri adult size tak pahunchne tak poori body mein badhti hai, aur phir zyadatar badhna band kar deti hai. Unka khaana alag jagahon se aata hai, isliye unke tissues phir alag hote hain: leaves mein aise tissues hote hain jo sunlight pakad kar khaana banate hain, jabki bakri ke gut mein aise tissues hote hain jo ghaas digest karte hain. Dono ko andar paani aur khaana idhar-udhar le jaana padta hai, lekin har ek apni tarah ka transport tissue use karta hai.

3.2 Plants mein Growth ke Tissues

Deewar ki daraar mein ugne wala peepal ka seedling saalon mein aisa tree ban sakta hai jiski roots deewar ko tod deti hain. Ek saal tak plants ko dhyaan se dekho, to tum unhe teen alag tareekon se badhte hue paoge:

• length mein: bean ka shoot apne dande par upar chadhta hai aur uski root mitti mein aur gehri jaati hai;
• girth mein: banyan ka tana saal dar saal chauda hota jaata hai;
• damage ke baad: hedge katne ke baad phir se ugti hai, aur bakriyon ke charne ke baad ghaas ka maidaan phir hara ho jaata hai.

Naye cells ke bina inmein se kuch nahi ho sakta, aur naye cells sirf divide hone wale cells se aate hain. Plants aise cells ko meristematic tissue (विभज्योतक ऊतक), ya short mein meristems, ke khaas patches mein rakhte hain. Meristem teen tarah ke hote hain, har tarah ki growth ke liye ek.

3.2.1 Apical meristem — Plants length mein kaise badhte hain?

Kya root apni poori length mein ek jaisi lambi hoti hai, ya sirf ek end par? Paani ke upar rakha onion achha test hai, kyunki uski roots tezi se badhti hain aur naapna aasaan hai.

Shoots ke saath bhi yahi hota hai. Har shoot aur har root ki tip mein divide hone wale cells ka ek chhota cluster hota hai, apical meristem (apex ka matlab hai tip). Jab yeh cells divide hote hain, to apne peeche naye cells chhod jaate hain; naye cells phir lambe hote hain aur tip ko aage dhakelte hain. Badhti root par barabar gaps par ink ke dots lagao. Ek-do din mein tip ke paas wale gaps chaude ho jaate hain, jabki peeche wale gaps waise hi rehte hain (Fig. 3.3).

3.2.2 Lateral meristem — Plants girth mein kaise badhte hain?

Ek chhote gulmohar ke paudhe ko baahon mein bharo, to tumhare haath aasaani se mil jaate hain. Bees saal baad nahi milenge. Kai plants, khaaskar dicots, lambe hone ke saath-saath chaude bhi hote hain. Lakdi ka gol coaster, ya kate hue log ka sira, is chaudaai ka record rakhta hai: rings ka ek set, ek ke andar doosri.

Yeh chaudaai ek meristem se aati hai jo stem ke andar, wood aur bark ke beech, ek patli ring ki tarah chalta hai (Fig. 3.5). Kyunki yeh tip par nahi balki stem ke sides ke saath hota hai, ise lateral meristem kehte hain. Iske cells do directions mein divide hote hain. Andar ki taraf bane naye cells wood bante hain, jo zyadatar xylem hota hai; bahar ki taraf bane cells bark ka hissa bante hain, jismein phloem hota hai. Layer par layer, stem mota hota jaata hai.

Rings kyun? India ke zyadatar hisson mein tree monsoon ke dauraan aur uske baad tezi se badhta hai, aur sookhe ya thande mahino mein dheere. Achhe season mein bani wood mein bade cells hote hain aur woh halki dikhti hai; kharab season mein bani wood mein chhote, kas kar packed cells hote hain aur woh gehri dikhti hai. Ek halki band aur ek gehri band milkar ek saal ki growth hai, ek annual ring. Rings ginne se tree ki age pata chalti hai. Har ring ki chaudaai bhi kahani batati hai: chaudi ring ka matlab us saal kaafi paani, aur patli ring sookhe ki taraf ishara karti hai. Scientists purane tanon ko is tarah padh kar pichhli sadiyon ke climate ke baare mein jaante hain.

3.2.3 Intercalary meristem — Katne ke baad plants kaise badhte hain?

Ek maali mehendi ki hedge ko shears se barabar kaat deta hai. Teen hafte baad hedge pehle se zyada ghani aur jhaadidaar ho jaati hai. Gaayein ek khet ki ghaas ko jad tak char jaati hain, phir bhi do hafte baad ghaas wapas aa jaati hai. Yeh kaise hota hai, yeh samajhne ke liye dekho ki leaves kahan lagi hain. Woh kahin bhi nahi judi hotin: woh stem par thode phoole hue points se ugti hain jinhe nodes kehte hain. Ek node se agle node tak stem ka har khaali hissa ek internode hai (Fig. 3.6).

Young stem ki tip kaat do to uska apical meristem hat jaata hai, isliye woh stem apni tip se aur lamba nahi ho sakta. Uski jagah kuch aur hota hai. Har node par chhote buds hote hain, jinhe badhti tip rok kar rakhti thi. Tip hatne par upar ke nodes ke buds jaag jaate hain aur side branches ban jaate hain. Isiliye kati hui hedge ghani ho jaati hai, aur isiliye maali tulsi ke plants ki tips todte hain.

Grasses ke paas ek aur tarkeeb hai. Woh apne internodes ke base ke paas, nodes ke theek upar, aur har leaf blade ke base par dividing cells ke patches rakhti hain. Yeh patches intercalary meristem hain (intercalary ka matlab hai 'beech mein daala hua'). Jab mower ya gaay grass blade ka upar wala hissa hata deti hai, to yeh cells divide hote rehte hain aur blade ko neeche se phir upar dhakelte hain. Isiliye lawn ko har hafte mow karna padta hai, aur isiliye charne se pasture marta nahi. Bamboo aur sugarcane, jo bahut badi grasses hain, unmein bhi intercalary meristems hote hain.

Saare meristems ek hi tarah ke cell se bane hote hain. Meristematic cells divide karne wali chhoti machines hain, aur unki structure is kaam ke hisaab se hai:

• woh chhote hote hain, unki cell walls patli aur lachiili hoti hain;
• har ek mein organelles se bhara dense cytoplasm aur ek bada, prominent nucleus hota hai;
• vacuoles nahi hote ya bahut chhote hote hain;
• woh kas kar packed hote hain, unke beech lagbhag koi jagah nahi hoti.

Vacuole kyun nahi? Jo cell lagbhag roz divide hota hai, use lagatar naya cytoplasm banana aur apni copy banani padti hai. Bada vacuole cell ka zyadatar hissa stored sap se bhar deta, jo koi building ka kaam nahi karta. Storage doosre cells ke zimme chhoda jaata hai.

Meristem cells ki nursery ki tarah kaam karta hai, aur uske zyadatar young cells zyada der young nahi rehte. Kuch dinon mein woh divide hona band kar dete hain, phool jaate hain, apni walls ki shape badalte hain aur hamesha ke liye ek kaam mein lag jaate hain. Root tip ke theek peeche ka ek cell lambi water pipe ban sakta hai, jabki uska padosi stored starch se bhar jaata hai. Is tarah settle hona differentiation (विभेदन) hai, aur isse bane mature tissues permanent tissues kehlate hain (Fig. 3.7). Kuch cells hamesha bina badle rakhe jaate hain, isliye meristem kabhi khatam nahi hota.

3.2.4 Permanent tissues

Ek young kaddu ya balsam ke stem ko jitna patla ho sake utna aada kaato, aur slice ko microscope ke neeche rakho. Tumhe ek tarah ka cell nahi, balki kai tarah ke cells dikhenge: bahar ki ek saaf row, bade gol cells, moti walls wale cells, aur bundles mein grouped cells. Har group ek permanent tissue hai jo apna kaam karta hai (Fig. 3.8). Kuch permanent tissues mein sirf ek tarah ka cell hota hai; yeh simple tissues hain. Doosre, complex tissues, kai tarah ke cells ko ek working unit mein jodte hain.

Protective tissue: epidermis

May ki dhoop mein leaf ko sookhne se kaun bachata hai, ya germs ko seedhe stem mein ghusne se kaun rokta hai? Har young plant part ek skin pehenta hai, epidermis, aur is skin ke teen kaam hain. Pehla, yeh ek barrier hai. Iski bahar ki walls par ek waxy parat hoti hai, cuticle, jo cutin naam ke substance se bani hoti hai. Wax paani ko andar aur fungi ko bahar rakhta hai aur hawa se udti ret ki maar jhelta hai. Aloe aur cactus jaise desert plants ki cuticle moti hoti hai, isiliye unki leaves chamde jaisi lagti hain.

Doosra, ismein darwaze hote hain. Leaf ki epidermis par chhote-chhote pores hote hain, stomata, har ek do guard cells ke beech. Photosynthesis ke liye carbon dioxide inse andar aati hai aur oxygen bahar jaati hai. Water vapour bhi isi raaste se nikalta hai; yeh loss, transpiration, ek pull banata hai jo roots se xylem mein paani upar kheenchta hai, aur kuch wastes bhi saath le jaata hai. Teesra, zameen ke neeche yeh sponge ki tarah kaam karti hai. Root ke kai epidermal cells bahar ki taraf lambe, patle root hairs ban jaate hain, jo milkar root ko paani aur minerals sokhne ke liye bahut bada surface dete hain. Structure mein epidermis simple hai: aam taur par chapte cells ki ek layer jo bina gaps ke judi hoti hai.

Supporting tissue: simple permanent tissues

Amrood khaate waqt kabhi chhote kirkire daane daanton mein aate hain. Kaddu ki leaf stalk ko modo to woh bina toote mud jaati hai. Water hyacinth ki phooli hui leaf stalk dabao to woh float jaisi spongy lagti hai. Iske peeche teen simple permanent tissues hain: parenchyma, collenchyma aur sclerenchyma (Fig. 3.9).

Aloo kaato to jo kuch dikhta hai woh lagbhag sab parenchyma hai, jiske cells starch se thase hote hain. Yeh plant ka har kaam ka tissue hai. Leaves aur young stems mein isi tarah ke cell mein chloroplasts hote hain aur woh khaana banata hai. Water hyacinth aur lotus mein ismein bade-bade air spaces hote hain, isiliye woh plants tairte hain. Parenchyma cells living hote hain, unki walls patli hoti hain, aur woh beech mein chhote gaps ke saath dheele-dheele judte hain.

Kaddu ki leaf stalk ki lachiili taakat collenchyma se aati hai, jo young stems aur leaf stalks ki epidermis ke theek neeche tissue ki ek band hai. Iske cells dekho to raaz samajh aata hai: unki walls sirf corners par extra moti hoti hain, jahan pectin, ek rubber jaisa material, jama hota hai. Mote corners support dete hain, jabki beech ki patli wall thoda lachak deti hai. Isliye stalk hawa mein jhoomti hai aur wapas seedhi ho jaati hai, aur tendril dande ke chaaron taraf lipat sakta hai. Collenchyma cells living hote hain.

Amrood ke kirkire daane sclerenchyma ke hain, jo plant ka sakht tissue hai. Iske cells apni walls lignin se itni moti bana lete hain, wahi substance jo wood ko lakdi jaisa banata hai, ki andar mushkil se koi jagah bachti hai. Wall poori hone ke baad zyadatar cells mar jaate hain. Lambe sclerenchyma fibres stems mein aur leaf veins ke chaaron taraf rigid sahaaron ki tarah chalte hain. Chhote, pathar jaise cells mango ki guthli ke aas-paas ka sakht hissa aur kai nuts ke chhilke banate hain.

Conducting tissue: complex permanent tissues

Nariyal ka ped 25 m lamba ho sakta hai. Uski roots ka liya paani sabse upar ki leaves tak pahunchna chahiye, aur un leaves mein bani sugar roots aur pakte nariyalon tak pahunchni chahiye. Yeh do-taraf traffic plant ke transport tissues, xylem (जाइलम) aur phloem (फ्लोएम), se chalta hai. Dono mein se koi bhi ek tarah ka cell nahi hai: har ek chaar ki team hai, isliye dono complex tissues hain (Fig. 3.10).

Xylem ko plant ki plumbing samjho, jo paani aur ghule hue minerals sirf ek taraf, upar ki taraf, roots se leaves tak le jaata hai. Pipes hain vessels aur tracheids: lambe, moti walls wale cells jo kaam shuru karte waqt dead aur khaali hote hain. Vessel cells ek ke upar ek judte hain aur beech ki walls kho dete hain, jisse khuli tubes banti hain jo door tak ja sakti hain. Xylem fibres, ek tarah ka sclerenchyma, sahaare ka kaam karte hain. Isiliye wood, jo zyadatar xylem hai, itni strong hoti hai. Inke beech kuch living helpers bhi bikhre hote hain, xylem parenchyma cells, jo khaana store karte hain aur paani ko side mein aage badhate hain.

Phloem delivery service hai. Yeh khaana, zyadatar sugar, leaves se wahan le jaata hai jahan zaroorat ho: neeche roots tak, upar badhti bud tak, ya pakte mango mein. Iske main channels sieve tubes hain, lambe cells ki chains jinki end walls mein chhalni jaise chhed hote hain, taaki meetha sap ek cell se doosre mein beh sake. Har sieve tube cell ke paas ek patla partner hota hai, companion cell. Yeh specialised parenchyma cell sieve tube ko zinda rakhta hai aur control karta hai ki kitni sugar andar daali ya bahar nikaali jaaye. Phloem parenchyma khaana store karta hai, saath mein resins, tannins aur latex bhi, aur phloem fibres taakat dete hain. Fibres ko chhod kar yeh saare cells living hain.

Tissue systems

Living plant mein yeh tissues kabhi akele kaam nahi karte. Yeh teen tissue systems mein organised hote hain, jo roots, stems aur leaves mein lagatar chalte hain (Fig. 3.8 ke steps 2 se 4):

1. Dermal ('skin') tissue system: epidermis, aur purane stems par cork. Yeh plant ka protective coat hai aur paani ko andar bhi rakhta hai.
2. Ground tissue system: coat aur transport tissues ke beech bhara sab kuch, yaani parenchyma, collenchyma aur sclerenchyma. Yeh khaana store karta hai, hare hisson mein khaana banata hai aur plant ko khada rakhta hai.
3. Vascular tissue system: xylem aur phloem, paani, minerals aur khaane ke liye plant ka transport network.

3.3 Animal Tissues

Abhi yeh chaar cheezein karke dekho:

• apne pair ki ungliyan hilao;
• tulsi ya mint ki ek leaf ragdo aur use soongho;
• dheere se saans andar lo aur paanch second rok kar rakho;
• ek naakhoon ko itna dabao ki woh safed pad jaaye, phir chhod do aur gulaabi rang wapas aate dekho.

Chaar chhote kaam, aur har ek mein alag tissue ka main role. Muscle tissue ne tumhare pair ki ungliyan mod di. Naak ke andar ki ek khaas lining ne smell pakdi. Lungs mein cells ki ek bahut hi patli layer ne oxygen ko blood mein jaane diya, aur blood khud, jo ek tissue bhi hai, naakhoon ke neeche wapas beh aaya. In sabke peeche nerves messages le ja rahi thi. Animal tissues chaar main families mein aate hain: epithelial, connective, muscular aur nervous tissue, aur har ek mein cells ki banawat kaam ke hisaab se hoti hai.

3.3.1 Epithelial tissues — Structure aur functions

Tumhari body ki har surface, bahar ho ya andar, epithelial tissue (एपिथीलियमी ऊतक) se dhaki hoti hai. Yeh bahar ki skin banata hai, aur muh se intestine tak gut, air passages, lungs ke air sacs aur har blood vessel ke andar ki lining banata hai. Iske cells ek patli base layer par baithe hote hain aur kinare se kinara milakar bina gaps ke jude hote hain. Isliye koi germ, paani ki boond ya khaane ka molecule cells ke beech se nahi nikal sakta; andar ya bahar jaane ke liye use unke through jaana padta hai. Isse epithelium control karta hai ki kya absorb hoga, kya secrete hoga aur kya bahar rakha jaayega.

Epithelial cells alag-alag shapes ke hote hain, aur har shape alag kaam ke liye theek hoti hai (table aur Fig. 3.11 dekho).

3.3.2 Hamari body mein alag-alag parts kaise jude hain?

Ek paheli: blood ki ek boond aur chicken ki haddi ke tukde mein kya common ho sakta hai? Ek behta hai, doosra goli jitne pathar ko rok sakta hai. Phir bhi biologists inhe ek hi family mein rakhte hain, connective tissue (संयोजी ऊतक). Inhe jodta hai inka kaam: dono body ke doosre tissues ko jodte, sahaara dete ya link karte hain. Blood har organ ko har doosre organ se jodta hai, unke beech khaana, oxygen, hormones aur wastes le jaakar, aur bone poori body ko ek dhaancha deti hai jis par sab tika rahe.

Epithelial cells ke ulat, connective tissue ke cells paas-paas packed nahi hote. Woh ek matrix mein bikhre hote hain, yaani woh material jo unke beech ki jagah bharta hai, aur matrix hi har tissue ko uski pehchaan deta hai. Blood ka matrix plasma hai, ek paani jaisa liquid, isliye blood beh sakta hai. Bone ka matrix minerals, yaani calcium aur phosphorus ke compounds, se sakht hota hai, isliye bone tumhara wazan utha sakti hai.

Blood ka sample rakha rehne do (doctors ise jaldi karne ke liye machine mein ghumate hain) aur woh alag ho jaata hai (Fig. 3.12). Upar ka bhoose ke rang ka liquid, volume ka lagbhag 55%, plasma hai, jismein ghula hua khaana, salts, proteins, hormones aur wastes hote hain. Baaki, lagbhag 45%, cells aur cells ke tukde hain. Red blood cells (RBCs) haemoglobin se bhare hote hain, ek oxygen le jaane wala protein jismein iron hota hai aur jo blood ko laal banata hai. Ek RBC lagbhag 120 din mein ghis jaata hai, aur body lagatar naye banati rehti hai. White blood cells (WBCs) body ko germs se bachate hain. Platelets, cells ke chhote tukde, clotting shuru karte hain jo ghaav ko band kar deti hai.

Blood aur bone hi connective tissues nahi hain. Agli activity karke apni body par aur bhi dhoondho.

Cartilage dhoondhna aasaan hai: yeh tumhare kaan ke flap aur naak ki tip ko shape deta hai, joints ke andar haddiyon ke siron ko dhakta hai, aur backbone ki discs banata hai. Iska matrix majboot lekin rubber jaisa hota hai, bone ki tarah minerals se sakht nahi, isliye ise dabaya ya moda ja sakta hai aur yeh wapas aa jaata hai. Tendons aur ligaments dono mazboot bands hain, aur inhe pehchanne ka sabse aasaan tareeka hai ki yeh kise jodte hain. Tendon (कंडरा) muscle se bone tak jaata hai. Ligament (स्नायु) ek bone se doosri bone tak jaata hai aur joint ko jode rakhta hai.

3.3.3 Kya hum apni body mein movement control kar sakte hain?

Tumhari body mein teen tarah ka muscle tissue hai, aur har ek ke baare mein pehla achha sawaal hai: kya yeh mere control mein hai? Haath hilao, aankh maaro, ya gaane par pair thapthapao: yeh sab tumne khud chuna, isliye yeh voluntary movements hain. Inke peeche ki muscles haddiyon se judi hoti hain, isliye inhe skeletal muscles kehte hain. Microscope mein skeletal muscle bahut lambe, cylindrical cells ke bundles nikalti hai, jinhe muscle fibres kehte hain. Har fibre mein kai nuclei hote hain, koi branches nahi hoti aur uske aar-paar halki aur gehri bands ka pattern hota hai. In bands ki wajah se ise striated (dhaaridaar) muscle bhi kehte hain.

Kuch aur movements chalti rehti hain, chahe tum unke baare mein socho ya nahi. Light jaane par tumhari aankhon ki pupils chaudi ho jaati hain, tumhara heart raat bhar taal mein dhadakta hai, aur tumhara pichhla khaana abhi gut mein aage dabaya ja raha hai. Yeh involuntary movements hain, aur do tarah ki muscles inhe karti hain:

• Smooth muscle khokhle organs ki walls ka hissa hoti hai: stomach aur intestines, blood vessels, bladder. Har cell spindle jaisa hota hai, dono siron par nukeela, ismein ek nucleus hota hai aur koi dhaariyan nahi hoti. Yeh dheere aur lagatar kaam karti hai, khaane ko gut mein halki lehron mein aage dhakelti hai.
• Cardiac muscle sirf heart mein hoti hai. Iske cells cylindrical lekin branched hote hain, jo judkar ek network banate hain; har ek mein aam taur par ek nucleus hota hai aur dhaariyan halki hoti hain. Aaraam ke waqt yeh lagbhag 70 baar per minute dhadakti hai, aur bina thake poori zindagi chalti rehti hai.

3.3.4 Body kaise mehsoos karti, sandesh bhejti aur respond karti hai?

Ek cricket ball tumhari taraf aati hai. Second ke chhote se hisse mein tumhari aankhein use dekhti hain, tumhara brain hisaab lagata hai ki woh kahan giregi, aur tumhare haath use pakadne badhte hain. Dekhna, tay karna aur karna, yeh sab nervous tissue ka kaam hai, jo brain, spinal cord aur body ke har hisse mein jaati nerves banata hai. Brain headquarters hai, jo reports ikatthi karta, yaadein store karta aur orders deta hai. Koi bhi muscle, voluntary ho ya involuntary, apne aap kaam nahi karti: har ek nerve signals ka intezaar karti hai. Jaise, achanak dar lagne par signals jaate hain jo pal bhar mein tumhara heart tez kar dete hain.

Nervous tissue neurons (तंत्रिका कोशिका), yaani nerve cells, se bana hota hai, aur inke parts seekhne ka sabse aasaan tareeka hai ek message ko ek neuron ke andar follow karna (Fig. 3.14). Message dendrites par pahunchta hai, jo chhote, shaakhaon wale extensions hain aur doosre cells se signals ikatthe karte hain. Phir woh cell body mein jaata hai, jismein nucleus hota hai aur jo cell ko chalata hai. Phir woh axon ke saath bahar nikalta hai, jo ek lamba fibre hai, aur doosre sire par axon terminals use doosre neuron, muscle ya gland ko de dete hain. Kuch axons bahut hi lambe hote hain: neeche ki spinal cord se pair ki muscles tak jaane wale lagbhag ek metre ke ho sakte hain.

3.4 Musculoskeletal System

Ab tum parts se ek-ek karke mil chuke ho: bones, cartilage, ligaments, tendons aur skeletal muscles, aur woh joints jahan haddiyan milti hain. Body mein yeh ek team ki tarah kaam karte hain, musculoskeletal system. Yeh team tumhe gravity ke khilaaf khada rakhti hai, tumhara posture banaye rakhti hai, tumhe idhar-udhar le jaati hai aur tumhare brain, heart aur lungs ki raksha karti hai. Nervous system iska boss hai: nerve ke signal ke bina koi skeletal muscle contract nahi hoti.

Muscles ke baare mein key fact yeh hai: muscle sirf pull kar sakti hai, contract hokar aur chhoti hokar; woh kabhi push nahi kar sakti. Jab muscle contract hoti hai, to uska tendon yeh kheenchav bone tak pahunchata hai, aur bone ek joint par ghoomti hai (Fig. 3.15). Bone ko wapas laane ke liye joint ki doosri taraf ki ek alag muscle ko pull karna padta hai. Isliye muscles pairs mein kaam karti hain: upper arm ke aage ki biceps elbow ko modti hai, aur peeche ki triceps use phir seedha karti hai.

Bone zyadatar logon ke andaaze se halki hoti hai: adult mein poora skeleton body ke mass ka sirf lagbhag aathvaan hissa hota hai, lagbhag 12–15%. Muscle ka hissa isse kaafi bada hota hai. Yeh figures age, sex, body ki banawat aur koi kitna active hai, iske hisaab se har insaan mein alag hote hain.

3.4.1 Kaam karta musculoskeletal system

Tumhari table ek pattern dikhati hai: shoulder aur hip lagbhag kahin bhi ja sakte hain, jabki elbow aur ghutna sirf mudte aur khulte hain. Yeh tay karta hai joint, yaani do ya zyada haddiyon ke milne ki jagah, aur khaaskar wahan haddiyon ke siron ki shape. Lekin joint sirf milne ki jagah hai. Haddiyon ko ghumane wala force hamesha muscles se aata hai, jo apne tendons ke through kheenchti hain.

3.5 Joints ke Types

Joint par haddiyon ke siron ki shape, aur uske aas-paas ke ligaments, tay karte hain ki woh kitna aur kin directions mein hil sakta hai (Fig. 3.16).

3.5.1 Ball and socket joint

Ek fast bowler ko dekho: haath poore gol ghere mein ghoomta hai. Shoulder ke andar upper arm ki haddi ka upar wala sira ball jaisa hota hai aur shoulder blade par ek uthle cup mein tika hota hai. Isliye woh kisi bhi direction mein ghoom sakta hai: aage, peeche, side mein ya gol. Yeh ball and socket joint hai. Shoulder blade aur collarbone milkar shoulder girdle banate hain, woh dhaancha jo har haath ko dhad se jodta hai. Tumhara hip bhi isi tarah bana hai, lekin uska cup zyada gehra hai: woh thodi aazaadi chhod kar wazan uthane ke liye zaroori sthirta paata hai.

3.5.2 Hinge joint

Darwaza khulta aur band hota hai lekin kabhi upar ya neeche nahi jaata. Tumhari elbow bhi isi tarah kaam karti hai, ek hi plane mein mudti aur khulti hai, isliye ise hinge joint kehte hain. Ghutne bhi hinges hain, jinke aage ek chhoti, chapti haddi, kneecap, pehra deti hai. Tumhari ungliyon aur pair ki ungliyon ke kai chhote joints bhi aise hi hain.

3.5.3 Pivot joint

Apne shoulders ko sthir rakho aur pehle apne left shoulder ke upar se dekho, phir right ke. Yeh ghoomna backbone ke bilkul upar hota hai. Pehli vertebra, jo skull ko uthati hai, ring jaisi hoti hai. Woh neeche wali vertebra se upar nikle ek khade khoonte ke chaaron taraf ghoomti hai, bilkul jaise ungli par ring ghoomti hai. Jo joint ek haddi ko doosri ke chaaron taraf is tarah ghoomne deta hai, woh pivot joint hai.

3.5.4 Fixed joints

Har joint hilta nahi. Tumhara skull haddi ki kai mudi hui plates se bana hai, jo lehardaar silaaiyon par itni kas kar judi hain ki bilkul hil nahi sakti. Aise joints fixed joints hain. Yeh skull ko brain ke chaaron taraf ek rigid helmet bana dete hain. Naye paida hue baby ki skull plates abhi aapas mein nahi judi hoti, isliye sir par naram jagahein hoti hain; yeh pehle do saalon mein band ho jaati hain.

3.6 Skeletal System

Adult ke skeletal system mein lagbhag 206 haddiyan hoti hain. Milkar yeh body ko shape deti hain, uska wazan uthati hain, naram organs ki raksha karti hain aur muscles ko kheenchne ke liye kuch deti hain. Yeh section do parts dekhta hai jinhe tum khud chhoo kar mehsoos kar sakte ho, backbone aur rib cage (Fig. 3.17); teesre bade rakshak, skull, se tum fixed joints mein mil chuke ho.

Dost ki peeth ke beech mein ungli neeche le jao, to tumhe ubhaaron ki ek line mehsoos hogi. Har ubhaar ek vertebra ka hai, un chhoti haddiyon mein se ek jo ek ke upar ek rakhi hokar backbone, yaani vertebral column, banati hain. Yeh dher upper body ko uthaye aur seedha rakhta hai, aur spinal cord iske andar ek surang se neeche jaati hai. Ek thos rod mazboot to hoti lekin mud nahi paati. Iske bajaye har vertebra aur agli ke beech cartilage ki ek disc hoti hai, rubber washer ki tarah. Isse column mud aur ghoom sakta hai, jabki haddiyon ko gaddi milti rehti hai aur spinal cord surakshit rehti hai.

Ab apne haath chhaati ke dono taraf rakho aur dheere se gehri saans lo. Tumhe hatheliyon ke neeche rib cage upar uthti aur chaudi hoti mehsoos hogi. Yeh backbone se mud kar aati ribs ke 12 jodon se bani hai, aur heart aur lungs ki raksha karti hai. Phir bhi yeh rigid nahi ho sakti, warna tum saans nahi le paate. Tarkeeb aage hai, jahan zyadatar ribs mudne wale cartilage ki pattiyon se breastbone (sternum) tak pahunchti hain. Saans andar lete waqt ribs ke beech ki muscles unhe upar aur bahar jhulati hain, chhaati mein zyada jagah banti hai aur hawa tezi se lungs mein bhar jaati hai. Saans chhodte waqt ribs wapas baith jaati hain.

Scientist ki tarah socho: ek cell, poora plant

Kya ek poori tarah bada, specialised plant cell wapas beginner ban sakta hai? 1958 mein American plant scientist F. C. Steward ne dikhaya ki haan, ban sakta hai.

Yeh itna hairaan karne wala kyun tha? Phloem cell ek poora bana, specialised cell hai jo aam taur par phir kabhi divide nahi hota. Steward ke flasks mein aisa tha jaise koi retired specialist wapas school chala gaya ho. Cells pehle dedifferentiate hue, apne special features chhod kar phir se divide hone lage aur unspecialised cells ka dher ban gaye. Phir nutrients aur growth substances ke guide karne par yeh dher redifferentiate hua, aur roots, shoots aur aakhir mein poora plant bana. Jo cell is tarah poora organism dobara bana sake, uske baare mein kehte hain ki usmein totipotency hai. Tumhari zindagi bhi aise hi ek cell se shuru hui thi: ek fertilised egg, yaani zygote, jo divide aur differentiate hokar tumhari poori body bana.

Yeh discovery plant tissue culture ka aadhaar hai. Aaj laboratories ek achhe plant ke chhote tukdon se hazaaron ek jaise, disease-free banana, potato, sugarcane aur orchid plantlets ugaati hain. Inhe bas thodi jagah chahiye aur yeh saal ke kisi bhi samay kaam kar sakti hain. Yahi method durlabh plants ko extinct hone se bachane mein bhi madad karta hai.