Important terminology

Autotrophic nutrition: Green plants can utilize the energy of sunlight to synthesize their own organic molecules.

Heterotrophic nutrition:   Animals derive their food by consuming plants or their products .Types of Heterotrophic nutrition

                                       
Holozoic (Gr. holo, whole + zoikos, of animals) in this  type of nutrition there is  ingestion of liquid or solid organic material.

Saprozoic in this type of nutrition organic material of plant or animal origin is consumed, eg fungi, bacteria, some protozoan.

Parasitic if one living organism feeds on other living organism and causes harm e.g. tapeworm, malarial parasite etc.

Scavengers ………….Feeding on carrions e.g. vultures

Cannibals ……………Feeding on member of same species

                  .
Digestion:-
The chemical and biological process of converting   insoluble and large
molecules are into smaller and soluble molecules with the help of
enzymes this process is called digestion,

Removal of undigested food is called Egestion.

(Both the process completes the digestion activity)


Digestive system of mammals

1)    Buccophrangeal cavity:
Vestibule is the space between lips and teeth  The roof consist of hard
and soft palate ,hard palate has maxilla ,premaxilla and palatine bones
.Terminal part of soft palate hangs in the throat called Uvula ,on both
sides tonsils are present which are made of lymphatic tissue. The
tongue is attached at base by a fold called Frenulum.

2) Papillae of tongue: Filiform most abundant have no taste buds.

Fungi these have abundant taste buds and appear as red colored dots on the tongue 

Foliate absent in man.

Circumvallate largest in size also has taste buds.

The taste of tongue   tip--------Sweet
Tips and sides………… Salt
Sides……….. Sour
Base ………Bitter

Tongue of dog also used as thermoregulation.


Teeth man has four types of teeth

Incisors
Canines
Premolar
Molar.


 


Dental formula  

UPPER JAW 2123(I C PM M)

LOWER JAW 2123 (I C PM M)

Dental formula for milk teeth 2102(I C PM M)

Interesting facts about dentition

Number of teeth that erupts only once in humans are 12.


In elephant two incisors keep growing called Tusks

Largest numbers of teeth are present in horse and pig

Enamel hardest substance of the body is ectodermal in origin

Dentine main part of tooth is mesodermal in origin.

Pyorrhoea is condition of infection of gums and tooth sockets.

Salivary glands :four pairs of salivary glands are found in man.



Infraorbital …..Absent in man present in rabbit.


These glands secrete secretion which aids in digestion of food; daily secretion is about 1.5 liters’

APPLIED -Mumps is viral infection of salivary glands mainly parotid .Pharynx has two openings one in esophagus and one in larynx.

An elastic cartilage plate called Epiglottis covers the glottis at the time of swallowing.

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Esophagus:
long it is a tube whose length is about 25 cm. it Peirces the diaphragm
and enters the abdominal cavity   Food is passed through the esophagus
by using the process of peristalsis. The layers of the esophagus are as
follows:

•    mucosa

o    Nonkeratinized
stratified squamous epithelium: it serves a protective effect due to the
high volume transit of food, saliva and mucus.

o    Lamina propria: sparse.

o    muscularis mucosae: smooth muscle

•    Submucosa: Contains the mucous secreting glands 

•   
Muscularis externa : composition varies in different parts of the
esophagus, to correspond with the conscious control over swallowing in
the upper portions and the autonomic control in the lower portions.

Stomach
In most mammals, the stomach is a hollow muscular organ of the
gastrointestinal tract involved in the second phase of digestion,
following mastication. The stomach is a highly acidic environment due to
hydrochloric acid production and secretion the stomach the stomach and
duodenum are divided by a thickened circular muscle layer called
pylorus.

When stomach is empty then its walls are in apposition
and when food reaches the walls starts separating giving passage to the
food
Image taken from  www.daviddarling.info

 

The stomach is divided into four sections, each of which has different cells and functions. The sections are:

Cardia    Where the contents of the esophagus empty into the stomach.

Fundus    Formed by the upper curvature of the organ.

Body or corpus    The main, central region.

Semisolid food mixed with gastric juice in stomach known ac Chyme.

Small intestine
it   is the main site for digestion and absorption of food the
intestinal contents are mixed with the intestinal juices, which is about
9litres/day of this 9litres 2 litres is derived from dietary sources
and remaining 7 litres is from GIT secretions only .

First part is Duodenum it is 25 cm long .it is C Shaped and has opening for bile and pancreatic ducts .Their opening is guarded by Sphincter of oddi.

Next part is jejunum
upper 40%of small intestine is called jejunum .there are more number of
goblet cells in this part and simultaneously more number of lymphoid
cells are also present the mucosal folds of this part are known as plicae circularis

Last part is Ilium
is about 1.8—2.5 m long it literally means rolls or coli it compromises
lower 60%of the small intestine .its main features are presence of
Crypts of Leiberkuhn which has epithelial cells which secretes mucus.
Digestion in small intestine

Carbohydrate digestion

1) Sucrose gets converted to glucose into fructose with the help of enzyme invertase
2) Maltose gets converted to two molecules of glucose with the help of enzyme maltase
3) Lactose gets converted to glucose and galactose with the help of enzyme lactase.

Fat digestion

Intestinal lipase is the main enzyme which converts fats to monoglycerides

Protein digestion

Peptones and polypeptides are converted to amino acids with the help of erypsins

Large intestine
it is about 1.5 m long consists of three parts Caecum, Colon, and
Rectum .A blind pouch of Caecum called Vermiform appendix .These parts
help in digestion of cellulose in herbivores histologically wall of
colon has three bands of longitudinal muscles called Taeniae coli. Last part of rectum is anal canal having a strong sphincter, it opens outside by anus.only absorption of water occurs here.

Liver
Largest digestive gland .It has four lobes .Surrounded by Glisson
capsule. The adult human liver normally weighs between 1.4 - 1.6
kilograms it is located on the right side of the upper abdomen below the
diaphragm anatomy. The liver lies to the right of the stomach and
overlies the gall bladder.

It consists of lobes which are further subdivided into lobules .

Portal
vein supplies the liver and gets divided into many branches .from these
vessels the blood passes between the hepatic cells in sinusoids and
ultimately reaches to the centre of the lobule

In similar fashion hepatic artery supplies the liver .

Kupffer
cells are present in the livers which are part of macrophage system
which lies along the endothelium. The falciform ligament is visible on
the front (anterior side) of the liver. This divides the liver into a
left anatomical lobe, and a right anatomical lobe From behind, the lobes
are divided up by the ligamentum venosum and ligamentum teres , the
transverse fissure (or porta hepatis) divides the caudate from the
quadrate lobe, and the right sagittal fossa, which the inferior vena
cava runs over, separates these two lobes from the right lobe.

Functions

1 Secretion of bile daily secretion is about 700—1000ml
2 Storage of fat
3 Urea syntheses
4 Erythropoisis (during embryonic life)
5 Breakdown of RBC
6 Iron is stored as ferritin

Pancreas image taken from www.gopetsamerica.com/






It
is situated between stomach and duodenum Pancreas consists of acini
(secrete digestive enzymes) and islets of langerhans (which secrete
insulin and glucagon).pancreatic juice also called complete digestive
juice, so it has double functions exocrine as well as endocrine function
.

Absorption No absorption takes place in mouth and
oesophgus .it takes place in small intestine by active passive and
facilitatd transport. Glucose, sodium and amino acid are absorbed
actively. In large intestine only water is absorbed.  Absorption of
vitamin b12 in man requires a glycoprotein, called intrinsic factor
which is secreted by parietal cells of the stomach. Failure of absorb of
cobalalmine called pernicious anaemia.

Carbohydrates Main
function is production of energy. These are compounds of C, H and O
.calorific value is 4.1 K Cal. Normal level of blood glucose is 80-120
mg/dl.daily requirement is 400-500gm, chief sources are floor, rice,
potato, milk, fruits, and vegetable end product of digestion is glucose
which is directly in the blood.diatary intake is about 60%of total
ammount of fat .

Classification of Carbohydrates

Monosaccharides they are called Simple sugars with 3—7 carbons e.g. glucose, fructose, and hexose

Disaccharides Formed by condensation of two molecules of Monosaccharides e.g. Maltose, sucrose, lactose

Polysaccharides Formed by condensation of a large number of Monosaccharides
E.g. starch, cellulose, glycogen.

Fats
Essential fatty acid are Linoleic acid, linolenic acid, arachidonic
acid, they are thus called because they cannot be synthesized in body.

End product of digestion is fatty acid and glycerol which are directly absorbed in blood.

Classification of fats
Simple lipids each molecule is made of one glycerol and three fatty
acid molecules .the are of two types 1) Saturated  e.g. palmitic acid
,stearic acid .

2)    Unsaturated fatty acid e.g. oleic acid, linoleic acid.

Compound lipids when fats are conjugated with some other substances.

Fats with phosphoric acid…… Phospholipids e.g. Cephalin, lecithin
Fats and carbohydrates…. Glycolipid.
Fused hydrocarbon rings and a long hydrocarbon side chain ….Sterol e.g. cholesterol

Proteins  
Main building blocks as 75% of our body consists of  proteins Proteins
are organic compounds made of amino acids arranged in a linear chain and
joined together by peptide bonds between the carboxyl and amino groups
of adjacent amino acid residues. All enzymes, o2 carrying pigments,
antibodies, most hormones are protein.Cheif sources are milk, egg, fish,
meat, pulses, and cereals.

Its requirement is more in Lactating
mothers, growing children and pregnant females .Caloric value of
proteins is 5.65Kcaland 20 amino acids make all different proteins .10
of them are essential (which cannot be synthesized in the body)

Simplest amino acid ………….Glycine

Longest chain amino acid is ………….Arginine

Minerals
these are essential components of cells as they regulate different
metabolic activities. Some of them required in large amounts
.Macroelements and those in very small amount …Microelements

Summary of digestion






Nutritional deficiency

Nutritional Deficiency and Its Symptoms:

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