Human Physiology(Digestive system)

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Human Digestive System(भानव ऩाचन तॊत्र)

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1) Human Digestive System(मानव पाचन तंत्र )- Thealimentary canal and the glands associated with digestion

constitute the human digestive system.

Alimentary canal(आहारनाऱ): The alimentary canal inhuman beings measures about 8 to 10 meters in length.

It extends from the mouth to the anus. It has the following

parts.

Mouth(मुह): The mouth consists of the oral cavity, throughwhich food is ingested. It is bounded by lips and cheeks. It

contains gums, teeth, a tongue and muscles.

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The tongue tastes food and moves it into the pharynx.

Teeth help in biting, cutting and chewing food. Teeth

masticate the food. This makes it easier to swallow food and

increases its surface area for various digestive secretions to

act on. The four types of teeth are incisors, canines,

premolars and molars. Our teeth are covered with a hard

protective covering of enamel.

The enamel covers the dentine, which is a yellowish

substance forming the bulk of the tooth. When we eat

sweets, chocolates and ice creams, bacteria act on sugars

and produce acids which soften the protective covering.

This causes dental caries. Bacterial cells and food particles

stick to the teeth and form dental plaque. If the teeth are not

brushed properly after meals, bacteria may invade deeper

into the teeth. This leads to infection and toothache.

The presence of food in the mouth stimulates the three

pairs of salivary glands to secrete saliva. Saliva has mucin,

which lubricates the mouth and food. Saliva also has salivary

amylase, a digestive enzyme that breaks down starch and

glycogen to maltose (a simpler sugar).

Pharynx(ग्रसनी): The oral cavity opens into the pharynx.The swallowing mechanism guides the masticated food

through the pharynx, into a tube called oesophagus.

Oesophagus(ग्रासनऱी): It is a muscular, tubular part of thealimentary canal. The muscular walls of the oesophagus

move in a rhythmic wavelike manner, which carries the

food down to the stomach. This muscular movement is

called peristalsis. Here also salivary amylase acts on starch

and glycogen in the chewed food.

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(A) Alimentary Canal and Digestive Glands of Man (B)

Food Passes Down the Alimentary Canal by Peristalsis

Stomach(उदर): It is located below the diaphragm (themuscular partition between the chest cavity and abdominal

cavity). It is a saclike muscular structure. It serves as a

storehouse of food where partial digestion takes place. The

stomach has an anterior cardiac and a posterior pyloric

part. As in other parts of the alimentary canal, columnar

cells line the inner wall of the stomach. The inner lining has

sunken pits. Each pit constitutes a gastric gland.

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About 3 L of gastric juice is produced per day. Excess secretion of

gastric juice, particularly in an empty stomach, erodes the inner

lining of the stomach. This erosion causes lesions or round

depressions called peptic ulcer in the stomach walls. Digestion of

protein begins in the stomach. Pepsin breaks down proteins into

peptones. Gastric lipase partially breaks down lipids.

Small intestine(छोटी आतं): The small intestine is about 6 meters inlength and 2.5 centimeters in thickness. There are three divisions of

the small intestine: duodenum, jejunum and ileum. Duodenum is

the first part. It begins from the pyloric stomach, and is C-shaped.

In the middle of the duodenum two different ducts open through a

common aperture.

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One of the ducts is the common bile duct and the other is

the pancreatic duct. Bile, a yellowish green alkaline juice, is

poured into the duodenum through the common bile duct.

Liver: It is the largest gland of the body. It performs many

functions. It secretes bile, which helps indigestion. Bile juice

produced by the liver is stored in the gall bladder.

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There are two main functions of bile:

1. It emulsifies fats, by rendering them soluble and breaking them

into small globules. In this form, fats are better exposed to the

action of fat-hydrolyzing enzymes. (All digestive enzymes

catalyze by breaking water molecules, and are hence called

hydrolyzing enzymes.)

2. The acidic food (chyme) coming from the stomach becomes

alkaline (chyle) when it is mixed with bile. This is important as

the intestinal enzymes catalyze the breakdown of food only in an

alkaline medium.

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Pancreas(अग्न्याशय): It secretes pancreatic juice, which is carriedby the pancreatic duct into the duodenum. Pancreatic juice

contains a number of digestive enzymes such as amylase for the

splitting of polysaccharides, lipase for the breakdown of fats, and

trypsin and chymotrypsin for the breakdown of proteins. These

enzymes catalyze the breakdown of their substrates in an alkaline

medium. But the catalysis does not completely break all the

substrates into their simplest units.

Jejunum is the middle part of the small intestine. It is found

only in man. Ileum is the last and main part of the small intestine.

The major part of digestion and absorption takes place here.

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Intestinal glands(आंतों की ग्रंथिया ं): The complete digestionof the remaining food material takes place in the ileum.

There are numerous small glands in the walls of the small

intestine. These glands secrete intestinal juice. The digestive

enzymes in the intestinal juice break small peptides into

amino acids, disaccharides into monosaccharide’s, lipids

into fatty acids and glycerol, and nucleic acids into

nucleotides.

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Large intestine(बड़ी आंत): The ileum passes into the large intestine.The large intestine can be divided into two parts: anterior (colon)

and posterior (rectum). At the junction of ileum and colon, there is

a blind (one end closed) outgrowth called caecum. The caecum ends

in the vermiform appendix (Latin vermis = worm; vermiform =

worm-shaped). In man, the vermiform appendix has outlived its

usefulness; it is a vestigial organ. It is an 8-cm-long blind tube,

which sometimes becomes a source of trouble.

The colon has an ascending part, a transverse part and a

descending part. The last part, or the descending part, opens into the

rectum. The terminal part of the rectum is called anal canal. It opens

through the anus, guarded by the sphincter muscles. The large

intestine allows the passage of residual food mass (faucal matter),

which is egested through the anus.

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As the residue of the food mass passes along the large intestine, a considerable

amount of water contained in the residue is absorbed into the blood through

the intestinal walls. The specialized longitudinal muscles present in the colon

wall regulate the passage of the faucal matter along the colon.

Take two clean test tubes. Pour 1 mL starch solution (1%) In each of

them. Add 1 mL saliva in one test tube only and keep both the test tubes in a

test tube holder undisturbed for half an hour. Now add a few drops of iodine

solution in both the test tubes.

You will observe that the saliva-containing test tube shows no blue-

black colour, while the other test tube does. What does it indicate? It shows

that saliva contains some enzyme which has converted starch into some

simpler compounds. In fact, salivary amylase present in saliva breaks down

starch into maltose.

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Absorption of Digested Food: Absorption of completely

digested food takes place in the ileum. The wall of the ileum has

finger-like projections called villi that increase the surface area for

absorption of digested food. The villi are richly supplied with blood

vessels to carry the absorbed food

You will observe that the saliva-containing test tube shows no blue-

black colour, while the other test tube does. What does it indicate?

It shows that saliva contains some enzyme which has converted

starch into some simpler compounds. In fact, salivary amylase

present in saliva breaks down starch into maltose.

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Absorption of Digested Food: Absorption of completely digested

food takes place in the ileum. The wall of the ileum has finger-like

projections called villi that increase the surface area for absorption

of digested food. The villi are richly supplied with blood vessels to

carry the absorbed food

The absorbed food is then brought into the blood capillaries. From

the blood capillaries, absorbed materials are transported by veins to

the liver and then to the heart for distribution to different parts of

the body.

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Assimilation of Digested Food: Intake of digested food by

cells of the body is called assimilation. Digested food is

utilized by the body in many ways. It is used to obtain energy

through the process of respiration. Excess monosaccharide’s

are stored as glycogen. Amino acids are used in the synthesis

of proteins.

The glycerol and fatty acids either provide energy or get

reconverted into fats. These fats are accumulated in different

organs below the skin. The absorbed food is also utilized for

the formation of new cells and tissues, leading to the growth

and development of the body.

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10. NUTRITIONAL AND DIGESTIVE

DISORDERS A. Protein Energy Malnutrition (PEM)

- Protein energy malnutrition refers to the disorders

arising from dietary deficiencies of proteins and total

food calories.

- PEM manifests as two disorders,

(i) Kwashiorkar and (ii) Marasmus.

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(i) KwashiorkarIt is casused by dietary deficiency of only protein, in children.

Its main cause is replacement of mother's milk by a low-protein but

high calorie food.

Its main symptoms include:

i. Oedema (water retention) and swelling of body parts.

ii. Wasting of muscles.

iii. Thinning of limbs.

iv. Retarded growth.

v. Impairment of brain development.

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(ii) MarasmusIt arises due to dietary deficiencies of both proteins and calories,

when the mother’s milk is replaced too early by other low protein

and energy foods.

It is common in infants, who are less than a year of age.

Its symptoms include.

(i) Retarded growth

(ii) Extreme emaciation of the body

(iii) Thinning of limbs

(iv) Skin becomes dry and wrinkled

(v) Growth rate and body weight decline considerably.

(vi) Impairment of development of brain and mental faculties.

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B. Inflammation of Intestinal Tract- This is the most common disorder of the digestive system.

- It is caused by infections by bacteria or viruses and also by

parasites like round worm, hook worm, pin worm, etc.

C. Jaundice(पीलऱया)- It is the infection and inflammation of the liver.

- Bile pigments are present in the blood and cause

yellowing of eyes, skin, etc.

D. Vomiting

- It is the egestion of contents of the stomach through

the mouth.

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Hindi notes

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ऩाचन अॊग

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भुख गहुा शयीय ऩाचन तॊत्र भे भुख गुहा भें ननम्न सॊयचनाएॊ होती है। (a)दाॊत शयीय ऩाचन तॊत्र भे भनुष्म के एक जफड ेभें 16 दाॊत व दानों जफडों भें 32 दाॊत होते है। दधुधमा(अस्थाई) दाॊत 20 होते है। भनुष्म भें चाय प्रकाय के दाॊत ऩामे जाते है। (1) क ॊ तक – सफसे आगे के दाॊत बोजन को कुतयने व काटने का कामय कयते है। प्रत्मेक जफड ेभें 4-4 होते है। एक औय 2 दाॊत होते है। (2)यदनक – मे बोजन को धचयने पाडने कामय कयते है। भासाहायीमों भें अधधक ववकसीत होते है। प्रत्मेंक जफड ेभें 2-2 होते है। (3)चवर्यक -मे बोजन चफाने कामय कयते है। प्रत्मेक जफड ेभें 4-4 होते है। (4)अग्र चवर्यक – मे बी बोजन चफाने का कामय कयते है। प्रत्मेक जफड ेभें 6-6 होते है।

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राय मह भनुष्म भें तीन जोडी राय ग्रॊन्थथमाॊ ऩाई जाती है। राय की प्रक नत हल्की अम्रीम होती है। राय भें टामलरन एथजाइभ ऩामा जाता है। मह एथजाइभ स्टाचय का ऩाचन कयता है।

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बोजन का ऩाचन भुॊह से शरुू हो जाता है।

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ग्रसनी इसकी ऩाइऩ के सभान सॊयचना होती है। ओय इसभें कोई ऩाचन ग्रॊन्थथ नहीॊ होती है। मह बोजन को भुख गुहहका से अभाशम तक ऩहुॊचाती है। अभाशम मह शयीय भें बोजन का अस्थाई अण्डाय होता है। इसभें बोजन रगबग 3-4 घण्टे तक रूकता है। इसभें जठय यस स्त्राववत होता है।

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मक त मक त शयीय भें न्स्थत, सफसे फडी ग्रॊधथ है। इसका अधधकाॊश उदयीम कोटय के ऊऩयी दाएॉ बाग भें न्स्थत है। इसका बाय 1.2 से 1.4 ककरोग्राभ के रगबग होता है। मह शयीय भें वऩत्तयस का ननभायर् औय वऩत्ताशम भें सॊग्रह कामय कयती है। ओय वऩत्तयस भें कोई बी एथजाइभ नहीॊ ऩामा जाता है। ऩयथतु मह बोजन के अम्रीम भाध्मभ को उदासीन फनाकय ऺायीम भें ऩरयवतीत का कामय कयती है ताकक अग्नाश्म यस भें उऩन्स्थत एथजाइभ कामय कय सके।

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अग्नाशमी यस के एथजाइभ हिऩसीन – प्रोटीन अऩघटन होतीहै । एभाइरेज – काफोहाइड्रटे अऩघटनकायी होतीहै । राइऩेज – वसा अऩघटनकायी होतीहै ।

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छोटी आॊत छोटी आॊत के तीन बाग होते हैं- ‘J’ आकाय की ग्रहर्ी, कुॊ डलरत भध्मबाग अग्रऺुद्ाॊत्र औय रॊफी कुॊ डलरत ऺुद्ाॊत्र। आभाशम का ग्रहर्ी भें ननकास जठयननगयभ अवयोधधनी द्वाया ननमॊत्रत्रत होता है। ऺुद्ाॊत्र फडी आॊत भें खुरती है जो अॊधनार, व हदाॊत्र औय भराशम से फनी होती है। अॊधनार एक छोटा थैरा है न्जसभें कुछ सहजीवीम सूक्ष्भजीव यहते हैं। अॊधनार से एक अॊगुरी जसैा प्रवयध,् ऩरयशवेषका ननकरता है जो एक अवशषेी अॊग है। अॊधनार, फडी आॊत भें खुरती है।छोटी आॊत एक रॊफी, ऩतरी ट्मूफ है। न्जसका व्मास 1 इॊच का है औय रगबग 10 पीट रॊफी है। मह ऩेट से ननचरी ओय न्स्थत है।

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फडी आॊत तीन बागों भें ववबान्जत होता है- आयोही, अनुप्रस्थ एवॊ अवयोही बाग। अवयोही बाग भराशम भें खरुता है जो भरद्वाय द्वाया फाहय खरुता है। आहाय नार की दीवाय भें ग्रलसका से भराशम तक, चाय स्तय होते हैं| जसेै लसयोसा, भस्कुरेरयस, सफम्मूकोसा औय म्मुकोसा। लसयोसा सफसे फाहयी ऩयत है औय एक ऩतरी भेजोधथलरमभ ;अॊतयॊग अॊगों की उऩकरा औय कुछ सॊमोजी ऊ…तकों से फनी होती है। भस्कुरेरयस प्राम: आॊतरयक वतुयर ऩेलशमों एवॊ फाईँ अनुदैर्घमय ऩेलशमों की फनी होती है। कुछ बागों भें एक नतमयक ऩेशी स्तय होता है। सफम्मूकोसा स्तय रुधधय, रसीका व तॊत्रत्रकाओॊ मुक्त भुरामभ सॊमोजी ई…तक की फनी होती है। ग्रहर्ी भें, कुछ ग्रॊधथमाॉ बी सफम्मूकोसा भें ऩाई जाती हैं। आहाय नार की ल्मूभेन की सफसे बीतयी ऩयत म्मूकोसा है। मह स्तय आभाशम भें अननमलभत वरम एवॊ छोटी आॊत भें अॊगुरीनुभा प्रवध ्य फनाता है न्जसे अॊकुय कहते हैं । अॊकुय की सतह ऩय न्स्थत कोलशकाओॊ से असॊख्म सूक्ष्भ प्रवध ्य ननकरते हैं न्जथहें सूक्ष्भ अॊकुय कहते हैं, न्जससे ब्रस-फाडयय जसैा रगता है। मह रूऩाॊतयर् सतही ऺेत्र को अत्मधधक फढ़ा देता है।

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फडी आॊत एक रॊफी, भोटी ट्मूफ है जो व्मास भें 2.5 इॊच औय रगबग 5 पीट रॊफी है. मह ऩेट से नीचे की तयप न्स्थत है औय छोटी आॊत के आसऩास लरऩटी हुई होती है

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इसके अरावा, तीन ग्रॊधथ ऩाचन की प्रकिमा भें सहामक होती हैं: अग्नाशम (Pancreas), न्जगय (Liver) औय वऩत्ताशम (Gallbladder).अग्थमाशम (Pancreas) : मह इॊसुलरन के उत्ऩादन के साथ यक्त शकय या ननमाभक कामय के लरए जाना जाता है. ऩाचन एॊजाइभ, अग्थमाशम द्वाया स्राववत होत ेहै, जो कक छोटी आॊत भें जात ेहै. मे एॊजाइभ वसा, प्रोटीन औय काफोहाइड्रटे के ऩाचन भें भदद कयत ेहैं. मक त (Liver) : मह वऩत्त स्राव कयता है न्जसभें एॊजाइभ होता है औय वसा (fat) के ऩाचन भें भदद कयता है. वऩत्ताशम (Gallbladder) : जफ वसा से बया बोजन छोटी आॊत भें प्रवेश कयता है तो वऩत्त की थैरी लसकुड जाती है औय सॊग्रहीत वऩत्त को स्राववत कयती है.

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ऩाचन तॊत्र के प्रभखु योग

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