Digestion and absorption class 11 notes for NEET
In this article, we are providing you Digestion and Absorption class 11 notes for NEET. This is an important chapter to pay attention from the Unit Human Physiology as a certain number of questions are asked from this chapter in NEET, AIIMS, JIPMER, and other medical entrances. The content deals with the important points on the Digestive system and Digestive Glands. Let's begin with the brief introduction of the Digestive system. Moreover, you can download the Digestion and Absorption class 11 NEET topper notes(710/720) pdf , we have shared at the end and digestion and absorption class 11 mind maps too.
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Introduction
- Food is one of the basic requirements of all living organisms.
- Animals are not able to synthesise their own food, therefore
they depend on ready-made food for their nutritional
requirements.
- Nutrition is the process by which an organism derives
energy to work and other materials, required for growth and
maintenance of the various activities of life.
- The major components of our food are carbohydrates, proteins
and fats. They are also known as biomacromolecules
- Vitamins and minerals are required in small quantities. Food
provides energy and organic materials for growth and repair
of tissues. They are also known as biomicromolecules.
- The water plays an important role in metabolic processes and
also prevents dehydration of the body.
- Biomacromolecules in food cannot be utilised by our body
in their original form. They have to be broken down and
converted into simple substances in the digestive system. This
process of conversion of complex food substances to simple
absorbable forms is called digestion and is carried out by our
digestive system by mechanical and biochemical methods.
|Types of Digestion
1. Intracellular: When the process of digestion occurs within
the cell in the food vacuole. Examples include Protozoa,
Porifera, Coelenterata and free living platyhelminthes.
2. Extracellular: When the process of digestion occurs outside
the cell. Examples include Coelenterates and phylum
platyhelminthes to phylum chordata.
|Digestive System
- Digestion in vertebrates occurs in the digestive tract or
alimentary canal.
- The various parts involved in digestion can be broadly
grouped in two groups :
1. Digestive tract or alimentary canal
2. Digestive glands
Alimentary canal
- The alimentary canal is tubular structure which extends from
mouth (anterior opening) to anus (posterior opening).
- The alimentary canal is divided into following parts:
(i) Mouth and Buccopharyngeal cavity
(ii) Oesophagus
(iii) Stomach
(iv) Intestine
Parts of alimentary canal
(i) Mouth
- The mouth is a transverse slit like aperture bounded by two
movable lips or labia, upper lip and lower lip.
- Mouth opens into buccopharyngeal cavity, this cavity is
divided into two parts namely buccal vestibule and oral cavity
Buccopharyngeal cavity
- It includes anterior buccal cavity is lined by stratified
squamous epithelial cells
- Pharynx is a vertical canal beyond the soft palate.
- Oral cavity leads into a short pharynx which serves as a
common passage for food and air. A cartilaginous flap called
epiglotis prevents the entry of food into glottis (opening of
wind pipe) during swallowing.
- Pharynx may be divided into three parts; nasopharynx,
oropharynx and laryngopharynx.
- Oral cavity is inner and central part which is surrounded
by upper and lower jaw. It is lined by stratified squamous
epithelium. Upper Jaw is fixed and lower Jaw is movable.
(iv) Tongue
- Freely movable muscular (mesodermal) organ and protrusible
present on the floor of buccopharyngeal cavity
- Stratified squamous epithelial cells are present.
- The upper surface of the tongue has small projects called
papillae. Some of which bears taste buds.
- Tongue is attached to the floor of the oral cavity by frenulum.
Functions of tongue
(i) Acts as universal toothbrush, as it helps in tooth cleaning.
(ii) Helps in speaking.
(iii) Helps in degglutition.
(iv) Helps in mixing saliva with food.
(v) Helps in taste detection.
Need to know:
Hard palate have transverse ridges called palatine rugae.
(v) Teeth
Structure of teeth
- Teeth divided into three parts:
(i) Root: Innermost, attached to the bone with the help of
cement (hyaluronic acid).
(ii) Neck: Middle, small, covered with gum. Gum provides
strength to the teeth.
(iii) Apex or crown: External exposed part of teeth. Longest
part, white in colour.
- The hard chewing surface of the teeth, made up of enamel,
helps in the mastication of food.
Š Thecodont: Each tooth is embedded in a socket of jaw bone.
This type of attachment is called thecodont.
Š Diphyodont: In most mammals teeth develop during life in two
successive sets, a condition known as diphyodont. Teeth of the
first set are known as deciduous teeth or milk teeth or lacteal
teeth whereas the second set is called permanent teeth.
Need to know:
The odontoblast cells are mesodermal in embryonic origin
forming immediate covering of the pulp cavity. The cells
secrete dentine.
Differentiation of teeth
Š Dentition is differentiated into two types:
(i) Homodont: When all the teeth are structurally and
functionally similar.
(ii) Heterodont: When the teeth are different in structure and
functions. They are distinguished into four types incisors,
canines, premolars and molars.
Types of teeth
(i) Incisor: These are long, chisel-like teeth for cutting and
chopping the food. They have one root
(ii) Canines: These are sharp pointed teeth meant for tearing and
shearing the food. Canines are most developed in carnivorous
animals and are absent in herbivorous animals. They have one
root
(iii) Premolars: These teeth are meant for chewing and crushing
of food. They are triangular in shape. The premolars of upper
jaw have two roots and lower jaw have one root
(iv) Molars (Cheek teeth): These also meant for chewing and
crushing of food. They are rectangular in shape. The molar of
upper jaw have 3 roots and lower jaw have 2 roots
KEY NOTE
Š Premolar and molar help in the mastication of food.
Š In mammals, except premolar and last molar, all type of
teeth appear twice in life.
Need to know:
Š Enamel, secreted by ameloblast or Enameloblast cells,
forms the outermost covering. It is ectodermal and made
up of 92% of inorganic substances, hence considered as
hardest part of the body.
Š The inorganic substances present are calcium phosphate
(85%), calcium hydroxide and calcium carbonate.
Š Ossein is a protein of bones.
- Dental formula: Each mammalian species is characterized
by its own specific dentition with a definite number and
arrangement of teeth.
- Arrangement of teeth in each half of the upper and lower jaw
in the order I, C, PM, M is represented by a dental formula
which in human is 2123/2123 .
Child = (2 1 0 2)×2 /(2 1 0 2)×2= 5×2/5×2= 20
17yr old= (2122)×2/(2122)×2=28
Adult= (2123)×2/(2123)×2=32
(ii) Oesophagus (food tube)
Morphology
- A thin, long tube which extends posteriorly passing through
the neck, thorax and diaphragm and leads to a ‘J’ shaped bag
like structure called stomach.
- Upper 1/3 of oesophagus is made up of skeletal muscles and
lower 2/3 is made up of smooth muscles.
- A muscular sphincter (gastro-oesophageal) regulates the
opening of oesophagus into the stomach.
Function: Conduction of food.
(iii) Stomach
Structure:
- Single oval, elongated, unilobed and J shaped bag like structure
and present in the upper left portion of the abdominal cavity
below diaphragm.
- It consists of four parts:
(i) Cardiac portion into which oesophagus opens
(ii) Fundic region
(iii) Pyloric portion which opens into the first part of small
intestine.
(iv) Body-Main central region.
- Two types of valves are present in the stomach viz. cardiac
sphincter valve between oesophagus and stomach and
pyloric sphincter valve between stomach and duodenum.
Need to know:
Inner surface of stomach is raised into numeros longitudinal
folds called gastric rugae.
Parts of stomach
Gastric glands in human has four distinct types of cells:
(a) Peptic or zymogenic or chief or cells : Secretes two
digestive proenzymes pepsinogen and prorennin.
(b) Oxyntic or parietal cells : Secretes HCl and castle’s
intrinsic factor required for the absorption of vitamin B12.
Hyperacidity is abnormally high degree of acidity due to
the secretion of large quantity of HCl, i.e., gastric juice.
(c) Mucous neck cells: Secretes alkaline mucous.
(d) Argentaffin cells : Responsible for the secretion of
vasoconstrictor serotonin. It plays a role regulation of
muscular movements.
(e) “G” cells, secrete a hormone, named gastrin, which
increases the motility of gastric wall and stimulates gastric glands for active secretion.
Functions:
- Storage of food.
- Churning of food to mix with gastric juice.
(iv) Small intestine
Structure: It is distinguishable into three regions:
(i) a ‘C’ shaped duodenum,
(ii) a long coiled middle portion jejunum
(iii) a highly coiled ileum.
- Also numerous finger-like projection called villi project from
the wall of lumen, increasing internal surface area about ten
time.
- The distal end of ileum leads into the large intestine by ileo-caecal valve in man.
Function: Digestion and absorption of food.
(v) Large intestine
Structure: Endodermal, approximately 1.5-1.75 metre long.
It consists of following parts:
(i) Caecum: It is small blind sac which hosts some symbiotic
microorganism. Its posterior end is present as a blind sac in
abdominal cavity called vermiform appendix. Vermiform
appendix is narrow finger-like tubular projection and is a
vestigial organ.
(ii) Colon: In human, it is distinguished into four parts as
ascending, transverse, descending part and sigmoid
colon. Colon is concerned with absorption of water from
undigested food, 5% salts, vitamins, etc., hence concerned
with faeces formation.
(iii) Rectum: The descending part opens into the rectum
which opens out through the anus. Single small dilated
sac-like in human. It is concerned with storage of faeces.
Rectum has strong sphincter muscle in its wall. The
sphincter keeps the canal as well as anus, closed when
not used for defecation.
Function: Absorption of water from undigested food.
(vi) Anal canal and anus: Anal canal connects rectum with anus
and it is about 3 cm long. Anus is the terminal inferior opening
of alimentary canal.
Histology of alimentary canal
- The wall of alimentary canal from oesophagus to rectum
possesses four layers namely serosa, muscularis, sub-mucosa
and mucosa.
(i) Serosa is the outermost layer and is made up of a thin
mesothelium (epithelium of visceral organs) with some
connective tissues.
(ii) Muscularis is formed by smooth muscles usually arranged
into an inner circular and an outer longitudinal layer. An
oblique muscle layer may be present in some regions.
(iii) The sub-mucosal layer is formed of loose connective tissues
containing nerves, blood and lymph vessels. In duodenum,
glands are also present in sub-mucosa.
(iv) Mucosa is the innermost layer lining the lumen of the
alimentary canal. This layer forms irregular folds (rugae) in
the stomach and small finger-like foldings called villi in the
small intestine.
- The cells lining the villi produce numerous microscopic
projections called microvilli giving a brush border appearance.
- These modifications increase the surface area enormously.
- Villi are supplied with a network of capillaries and a large
lymph vessel called the lacteal.
- Mucosal epithelium has goblet cells which secrete mucus that
help in lubrication.
- Mucosa also forms glands in the stomach (gastric glands) and
crypts in between the bases of villi in the intestine (crypts
of Lieberkuhn). All the four layers show modifications in different parts of the alimentary canal.
|Digestive Giands
- The various types of digestive glands present in mammals are
salivary glands, gastric glands, intestinal glands, pancreas and
liver.
- The digestive glands secrete digestive juices.
- Parasympathetic nervous system increases the secretion of
digestive juice whereas sympathetic nervous system decreases
it.
Salivary glands
- Three pairs of salivary glands present in humans are as
follows:
1. Parotid (cheek): One-pair, largest salivary gland present.
2. Sub-mandibular / sub-maxillary (lower jaw): One-pair,
present at the junction of upper and lower jaw in cheek region.
3. Sub-lingual (below the tongue): One-pair, present in the
floor of buccopharyngeal cavity.
Need to know:
Š Parotids: Stenson’s duct
Š Sub-maxillary or sub-mandibular: Wharton duct
Š Sublingual’s: Duct of Rivinus
- The secretion of salivary glands is called saliva or salivary
juice. Some of the characteristics are as follows -
● Amount: 1.0-1.5 litre/day
● Chemical nature: Slightly acidic.
● pH : 6.3 - 6.8
● Control of secretion: Autonomic reflex (parasympathetic
nervous system increases salivation while sympathetic
nervous system inhibit secretion.)
● Chemical composition: Water (99.5%), mucous (acts as
lubricant), salts (NaCI, NaHCO3
etc.), enzymes (ptyalin,
lysozyme) etc..
- It is the largest gland of the body weighing about 1.2 to 1.5 kg
in an adult human.
- It is situated in the abdominal cavity, just below the diaphragm
and has two lobes.
- The hepatic lobules are the structural and functional units of
liver containing hepatic cells arranged in the form of cords.
- Each lobule is covered by a thin connective tissue sheath
called the Glisson’s capsule.
- The bile secreted by the hepatic cells passes through the
hepatic ducts and is stored and concentrated in a thin muscular
sac called the gall bladder.
- The duct of gall bladder (cystic duct) along with the hepatic
duct from the liver forms the common bile duct.
KEY NOTE
The bile duct and the pancreatic duct open together into the
duodenum as the common hepato-pancreatic duct which is
guarded by a sphincter called the sphincter of Oddi.
Pancreas
- The pancreas is a compound (both exocrine and endocrine)
elongated organ situated between the limbs of the ‘C’ shaped
duodenum.
- The exocrine portion secretes an alkaline pancreatic juice
containing enzymes and the endocrine portion secretes
hormones, insulin and glucagon.
|Digestion of Food
- Digestion is divided in two ways: Mechanical digestion and
Chemical digestion. Mechanical digestion takes place in
mouth and small intestine.
Digestion in oral cavity
- Food enters through mouth and mixed with saliva, tongue
mixes the food with saliva.
- Mucus in saliva helps in lubricating and adhering the
masticated food particles into a bolus. The bolus is then
conveyed into the pharynx and then into the oesophagus by
swallowing or deglutition.
- The bolus further passes down through the oesophagus by
successive waves of muscular contractions called peristalsis.
Mechanical digestion
- In mouth teeth, tongue and lips have important role in
mechanical digestion through the process of chewing or
mastication. They help in mixing up the food thoroughly.
Chemical digestion
- The saliva secreted into the oral cavity contains electrolytes
(Na+, K+, CI–
, HCO–3
) and enzymes, salivary amylase and
lysozyme.
- The chemical process of digestion is initiated in the oral
cavity by the hydrolytic action of the carbohydrate splitting
enzyme, the salivary amylase. About 30 per cent of starch
is hydrolysed here by this enzyme (optimum pH 6.8) into a
disaccharide – maltose.
-
Mucin: It is a glycoprotein. It lubricates the food particles and
helps in the swallowing of food.
- Lysozyme: It is an enzyme which kills the harmful bacteria. It
acts as an antibacterial agent that prevent infections.
- Thiocynate: It is a special salt which kills the harmful
bacteria. So it is called bacteriocidal salt.
Starch
Ptyalin, ph 6.8
→
Salivary amylase
Maltose
Need to know:
Ptyalin is found in human saliva because human food is
mainly made up of starch.
KEY NOTE
Š Peristalsis is progression of coordinated contraction of
involuntary circular muscles, which is preceded by a
simultaneous contraction of the longitudinal muscle and
relaxation of the circular muscle in the lining of gut.
Š Gastroesophageal sphincter or cardiac sphincter normaly
remains closed and does not allow food contents of the
stomach to move back.
Digestion of food in stomach
- When the food enters into stomach G-cells secrete gastrin
hormones which stimulate the secretion of gastric juice by
gastric glands.
- Secretion of gastric juice is controlled by nerve, hormones and
chemical substances.
Need to know:
Some drinking substances also stimulates the secretion of
gastric juice such a soup, alcohol, caffeine, histamine. These
drinking substance and gastric juice stimulate the desire of
appetite. So these substances are called appetiser juice.
Composition of Gastric juice
- Amount : 1-1.5 liters/day.
- Chemical nature: Highly acidic
- pH : 1.0 - 3.5 (due to presence of HCl)
- Control of secretion: By gastrin hormone.
- Chemical composition: Water (99%), mucous, inorganic
salts, castle’s intrinsic factor, HCI (0.5% conc) and enzymes
prorennin and pepsinogen and gastric lipase.
- The stomach stores the food for 4-5 hours. The food mixes
thoroughly with the acidic gastric juice of the stomach by the
churning movements of its muscular wall and is called the
chyme.
Functions of HCl
- The main function of HCl (activater) is to convert proenzyme
pepsinogen into active enzyme pepsin.
- Pepsin converts proteins into proteoses and peptones (peptides).
Pepsinogen →
HCl
Pepsin
Prorennin →
HCl
Rennin
- The mucus and bicarbonates present in the gastric juice play
an important role in lubrication and protection of the mucosal
epithelium from excoriation by the highly concentrated
hydrochloric acid.
- HCl provides the acidic pH (pH 1.8) optimal for pepsins.
KEY NOTE
Š Pepsinogen and prorennin are inactive enzymes.
Š Pepsin is the proteolytic enzyme of the stomach.
Digestion by Rennin
- Rennin (proteolytic enzyme) is active in the childhood stage
of mammals only. It converts milk into curd like substance
(clot the milk) and then digests it. In adult stages, it is inactive.
- Rennin acts on milk protein casein. Casein is a soluble protein.
- In presence of rennin, casein gets converted into insoluble Ca�paracaseinate. This process is termed as curdling of milk.
After becoming insoluble, milk can remain in the stomach for
a longer time. Rennin is absent in adult human (curdling of
milk is done by HCl, pepsin and chymotrypsin in human)
Digestion by Gastric Lipase
- It converts fats into fatty-acids and glycerols. It is secreted in a
less amount so less digestion of fats takes place here.
- This lipase acts on emulsified fat and convert it into fatty acid
and glycerol.
Digestion of Food in small intestine
- In small intestine mechanical and chemical digestion occurs.
- Various types of movements are generated by the muscularis
layer of the small intestine.
- These movements help in a thorough mixing up of the food with
various secretions in the intestine and thereby facilitate digestion.
- The bile, pancreatic juice and the intestinal juice are the
secretions released into the small intestine.
Pancreatic juice
- Pancreatic juice and bile are released through the hepato�pancreatic duct.
- The pancreatic juice contains inactive enzymes – trypsinogen,
chymotrypsinogen, procarboxypeptidases, amylases, lipases
and nucleases.
- Trypsinogen is activated by an enzyme, enterokinase, secreted
by the intestinal mucosa into active trypsin, which in turn
activates the other enzymes in the pancreatic juice.
Bile juice
- In the proximal-part of the duodenum bile-juice is secreted.
- The hepatocytes of the liver produce bile juice and it is stored
in the gall bladder.
- Bile juice does not contain any digestive enzyme. Therefore it
is not a true digestive juice (Pseudodigestive juice).
Compostion of Bile-juice
- The bile released into the duodenum contains bile pigments
(bilirubin and bili-verdin), bile salts, cholesterol and
phospholipids but no enzymes.
Function of bile juice
- Neutralization of HCl: Its sodium neutralizes HCl of chyme
(semifluid food found in the stomach).
- Emulsification: Sodium glycocholate and sodium
taurocholate are bile salts which break the large fat droplets
into the smaller micelles.
- Absorption of fat and fat-soluble vitamins: Bile salts help
in the absorption of fats (fatty acids and glycerol) and fat�soluble vitamin (A, D, E and K).
- Stimulation of peristalsis: Bile increases peristalsis of the
intestine.
- Activation of Lipase: Bile also activates the enzyme lipase.
Need to know:
Š Bile-pigments, cholesterol and lecithin are the excretory
substances found in bile juice.
Š Gall-Stone: Sometimes the passage inside the bile-duct
gets blocked or becomes narrow, so the cholesterol gets
deposited or precipitated in the gall-bladder. This is
termed as the gall-stone (cholelithiasis).
Š Obstructive Jaundice: If the passage of bile is blocked
then the amount of bilirubin increases in the blood. So the
yellowish colouration of body like skin, cornea and nails
appear yellow. Urine also becomes yellow.
Digestion in duodenum, jejunum and ileum
- These hormones stimulate the crypts of Leiberkuhn to secrete
succus entericus or intestinal juice. This succus entericus
mainly contains water (99%) and digestive enzymes (<1%).
Intestinal juice act on food.
- The intestinal mucosal epithelium has goblet cells which
secrete mucus.
- The secretions of the brush border cells of the mucosa
alongwith the secretions of the goblet cells constitute the
intestinal juice or succus entericus.
- This juice contains a variety of enzymes like disaccharidases
(e.g., maltase), dipeptidases, lipases, nucleosidases, etc. The
mucus alongwith the bicarbonates from the pancreas protects
the intestinal mucosa from acid as well as provide an alkaline
medium (pH 7.8) for enzymatic activities.
- Sub-mucosal glands (Brunner’s glands) also help in this.
Succus-entericus mainly contains the following enzymes:
- Peptidase or Erepsin: This is a type of exopeptidase. It
converts oligopeptides into amino-acids.
- Sucrase: It is also known as invertase. It converts sucrose into
glucose and fructose.
- Maltase: It converts maltose sugar into glucose molecules.
- Lactase: This enzyme is found only in mammals. It converts
milk sugar lactose into glucose and galactose.
- Intestinal Lipase: This fat-digesting enzyme converts fats
into fatty-acids and glycerol.
- Nucleotidase and Nucleosidase: These act on nucleotides
and nucleosides and convert them into sugars and bases.
Digestion in Large Intestine
- No significant digestive activity occurs in the large intestine.
- The functions of large intestine are:
(i) Absorption of some water, minerals and certain drugs
(ii) Secretion of mucus which helps in adhering the waste
(undigested) particles together and lubricating it for an
easy passage.
- The undigested, unabsorbed substances called faeces enters
into the caecum of the large intestine through ileo-caecal
valve, which prevents the back flow of the faecal matter. It is
temporarily stored in the rectum till defaecation.
- The activities of the gastro-intestinal tract are under neural and
hormonal control for proper coordination of different parts.
- The sight, smell and/or the presence of food in the oral cavity
can stimulate the secretion of saliva.
- Gastric and intestinal secretions are also, similarly, stimulated
by neural signals.
- The muscular activities of different parts of the alimentary
canal can also be moderated by neural mechanisms, both local
and through CNS.
- Hormonal control of the secretion of digestive juices is
carried out by the local hormones produced by the gastric and
intestinal mucosa.
Need to know:
In herbivores, the symbiotic bacteria and protozoans present
in the caecum help in digestion of cellulose into glucose.
So the digestion of cellulose takes place in caecum by the
process of decomposition. This decomposition process is
very slow. So very less amount of cellulose is digested at a
time in caecum.
KEY NOTE
Š Maximum digestion of food – Duodenum.
Š Digestion of food complete in – Jejunum.
Š Maximum absorption of food in – Jejunum.
Absorption of Digested Food
- Absorption is the process by which the end products of
digestion pass through the intestinal mucosa into the blood
or lymph.
- It is carried out by passive, active or facilitated transport
mechanisms.
Simple diffusion: It facilitates the absorption of small
amounts of monosacharides like glucose, amino acids and
some of electrolytes like chloride ions
● The passage of these substances into the blood depends
upon the concentration gradients.
Facilitated transport: Some of the substances like fructose
and some amino acids are absorbed with the help of the carrier
ions like Na+.
Active transport:
● Transport of water depends upon the osmotic gradient.
● Active transport occurs against the concentration gradient
and hence requires energy.
● Various nutrients like amino acids, monosacharides like
glucose, electrolytes like Na+ are absorbed into the blood
by this mechanism.
Table: Absorption in Different Parts of Digestive System
- Fatty acids and glycerol being insoluble, cannot be absorbed
into the blood.
- They are first incorporated into small droplets called micelles
which move into the intestinal mucosa.
- They are re-formed into very small protein coated fat globules
called the chylomicrons which are transported into the lymph
vessels (lacteals) in the villi. These lymph vessels ultimately
release the absorbed substances into the blood stream
- The absorbed substances finally reach the tissues which utilise
them for their activities. This process is called assimilation.
- The digestive wastes, solidified into coherent faeces in the
rectum initiate a neural reflex causing an urge or desire for
its removal. The egestion of faeces to the outside through
the anal opening (defaecation) is a voluntary process and is
carried out by a mass peristaltic movement.
Need to know:
Calorific value of protein, carbohydrate and fat
The energy requirements of animals, and the energy content
of food, are expressed in terms of measure of heat energy
because heat is the ultimate form of all energies. This is
often measured to as calorie (cal) or joule (J), which is the
amount of heat energy required to raise the temperature of 1
g of water by 1°C. Since this value is tiny amount of energy,
physiologists commonly use kilocalorie (kcal) or kilo joule
(kJ). One kilo calorie is the amount of energy required to
raise the temperature of 1 kg of water by 1°C. Nutritionists,
traditionally refer to kcal as the Calorie or Joule (always
capitalised). The amount of heat liberated from complete
combustion of 1 g food in a bomb calorimeter (a closed metal
chamber filled with O2
) is its gross calorific or gross energy
value. The actual amount of energy combustion of 1 g of
food is the physiologic value of food. Gross calorific values
of carbohydrates, proteins and fats are 4.1 kcal/g, 5.65 kcal/g
and 9.45 kcal/g, respectively, whereas their physiologic
values are 4.0 kcal/g, 4.0 kcal/g and 9.0 kcal/g, respectively.
|Disorders of Digestive System
- The inflammation of the intestinal tract is the most common
ailment due to bacterial or viral infections. The infections are
also caused by the parasites of the intestine like tape worm,
round worm, thread worm, hook worm, pin worm, etc.
- Jaundice: The liver is affected, skin and eyes turn yellow due
to the deposit of bile pigments.
- Vomiting: It is the ejection of stomach contents through the
mouth. This reflex action is controlled by the vomit centre in
the medulla. A feeling of nausea precedes vomiting.
- Diarrhoea: The abnormal frequency of bowel movement
and increased liquidity of the faecal discharge is known as
diarrhoea. It reduces the absorption of food.
- Constipation: In constipation, the faeces are retained within
the rectum as the bowel movements occur irregularly.
- Indigestion: In this condition, the food is not properly digested
leading to a feeling of fullness. The causes of indigestion are
inadequate enzyme secretion, anxiety, food poisoning, over
eating, and spicy food.
|Protein-Energy Mainutrition EPEMF
- Dietary deficiencies of proteins and total food calories are
widespread in many underdeveloped countries of South and
South-east Asia, South America, and West and Central Africa.
- Protein-energy malnutrition (PEM) may affect large sections
of the population during drought, famine and political
turmoil. This happened in Bangladesh during the liberation
war and in Ethiopia during the severe drought in mid-eighties.
- PEM affects infants and children to produce Marasmus and
Kwashiorkar.
Marasmus
- Marasmus is produced by a simultaneous deficiency of
proteins and calories.
- It is found in infants less than a year in age, if mother’s milk
is replaced too early by other foods which are poor in both
proteins and caloric value. This often happens if the mother
has second pregnancy or childbirth when the older infant is
still too young.
- In Marasmus, protein deficiency impairs growth and
replacement of tissue proteins; extreme emaciation of the
body and thinning of limbs results, the skin becomes dry, thin
and wrinkled.
- Growth rate and body weight decline considerably. Even
growth and development of brain and mental faculties are
impaired.
Kwashiorkar
- Kwashiorkar is produced by protein deficiency
unaccompanied by calorie deficiency.
- It results from the replacement of mother’s milk by a high
calorie-low protein diet in a child more than one year in age.
KEY NOTE
Like marasmus, kwashiorkor shows wasting of muscles,
thinning of limbs, failure of growth and brain development.
But unlike marasmus, some fat is still left under the skin;
moreover, extensive oedema and swelling of body parts
are seen.
This is the end of this chapter
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digestive system, gastric juice, pancreatic juice, abdominal cavity, gastric glands, amino acids, vermiform appendix, secrete mucus, intestinal glands, cystic duct, notes for neet, types of teeth, digestion of food, part of the alimentary, smooth muscles, bile duct, buccal cavity, large intestine, salivary amylase, digestive enzymes
Digestion and absorption class 11 mind maps
NEET topper (710/720) handwritten notes
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