ISC 12>CONTENT>STRUCTURE AND FUNCTION OF ANIMALS>2. NUTRITION 

CLASS PRESENTATION

ANIMATIONS AND INFORMATION LINKS

digestionanimation 
organs_of_digestion
workingofdigestivesystem
DigestiveSystem 
thedigestivesystemproblems 
digestive-system-cleanse 
digestive-system-disorder-medication 
animal_nutritionppt.pdf
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SCOPE OF SYLLABUS
Structure and functions of the digestive organs and their associated glands; hormonal regulation of digestive juices; absorption of food; factors controlling the absorptive power and small intestine as principal site for absorption, assimilation of digested food; disorders of the digestive system – jaundice, constipation, diarrhoea, PEM and vomiting.

NUTRITION

PROCESS OF OBTAINING FOOD BY LIVING BEINGS, ITS DIGESTION AND  UTILIZATION FOR ENERGY.

AUTOTROPHS  

Organisms that synthesize organic substances from inorganic substances.
  • phototrophs
  • chemotrophs 

 HETEROTROPHS

Organisms that use chemical energy of organic compounds synthesized by other organisms. 
  • holozoic 
  • saprozoic
  • parasitic

Intracellular digestion

Food is digested inside the cell- eg. Amoeba, paramoecium.

Extracellular digestion

Food is digested in the alimentary canal- outside the cells.eg. earthworm, fishes, man

THE DIGESTIVE SYSTEM- ALIMENTARY CANAL PARTS

watch the video
the_stages_of_digestion.flv
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THE ORGANS AND THEIR FUNCTION

DRAW THE DIAGRAM

1. MOUTH AND BUCCAL CAVITY

The mouth is a transverse slit like opening bounded by two soft movable lips.

Buccal cavity is bound by-
1. Above- Palate
  • roof of the buccal cavity has two parts - hard palate with rugae and posterior part the soft palate that makes swallowing easier.
  • small flap the uvula or velum palati closes the internal nares during swallowing of food bolus.
2. Below- throat
3. Sides- jaws

Inside the buccal cavity is present a muscular tongue and teeth arranged on the jaws.

TONGUE 

Is a skeletal muscle, helps to moves food in mouth, and to taste.  
Taste buds- have papillae 
  • Fungiform - mushroom shaped
  • Filliform - thread like
  • Circumvalate - inverted V at the posterior
Taste regions 
  • Sweet-tip of the tongue
  • Salt- on the sides
  • Bitter- on the posterior part 
Functions-
  • Helps in ingestion and tasting food
  • For swallowing
  • Helps in speech
http://2.bp.blogspot.com/_CId289lYIdc/Sa8OEnlm9gI/AAAAAAAACAY/EWzLRV3uUZo/s400/Tongue2.jpg

TEETH

Picture
http://www.student.loretto.org/humanbiology/BioLinks/chp5/media/c236f1_0.gif
FOUR types of teeth- incisors, canines, premolars, molars 
The human teeth is 
  • Heterodont: four types present. 
  • Thecodont: neck and root are held in a socket. 
  • Diphyodont: milk teeth are replaced by permanent teeth.

L.S.of molar tooth

http://www.infovisual.info/03/img_en/034%20Tooth%20(section%20of%20a%20molar).jpg
Draw the diagram

Competitive focus-Dental formula

Representation of the arrangement of human teeth.
http://www.merriam-webster.com/art/med/dental.gif
dentalformulae
dentalanatomy 
http://media.tiscali.co.uk/images/feeds/hutchinson/ency/c00764.jpg

2. PHARYNX

It is a common passageway for air and food.
It participates in swallowing 
It has 
  • Two nasal openings 
  • Two openings for Eustachian tubes 
  • Gullet- the opening of the oesophagus 
  • Glottis opening of the larynx or trachea 
  • Opening of buccal cavity into the pharynx.

It has three parts-
  • Nasopharynx – nasal chamber  
  • Oropharynx – behind buccal cavity 
  • Laryngopharynx- lowest part with two openings- glottis and gullet.
http://www.drugs.com/health-guide/images/205299.jpg

3. OESOPHAGUS

It connects pharynx to stomach
  • Structure: mix of skeletal and smooth muscle 
  • Mucus secreting cells: assist passage of food
  • Food motility: gravity and peristalsis

Peristalsis- contraction and relaxation of muscles which propagates in a wave down the muscular tube.
http://images.tutorvista.com/content/nutrition/peristalsis.jpeg

4. STOMACH

Large, muscular, somewhat J shaped sac, occupying the upper left part of the abdominal cavity.
Two regions- Cardiac and Pyloric.
Shows the presence of longitudinal folds called rugae. 
Functions: 
Food storage, digestion, regulation of delivery. 
Produces gastric juice for digestion. 
  • Hydrochloric acid: produces a pH of about 2, breaks down large bits of food. 
  • Intrinsic factor; needed to absorb Vitamin B12 
  • Mucus: protects stomach lining from acid. 
  • Pepsinogen: with acid, begins protein breakdown.

Gastrin: hormone secreted for stimulating digestion.

Layers of the stomach wall

http://www.daviddarling.info/images/stomach.jpg
http://www.rivm.nl/interspeciesinfo/Images/stomach-figure-2_tcm75-26457.gif
Stomach-innerlayers

What is heartburn or acidity?

Heartburn or pyrosis

When the cardiac sphincter fails to close fully, the acidic chyme squeezes into the oesophagus.
This irritates the lining of oesophagus and causes heartburn.


CARDIAC SPHINCTER
It is less effective in infants hence regurgitation is more common among infants.

SMALL INTESTINE

Small intestine consists of 
  • Duodenum- 10 inches 
  • Jejunum- 8 feet 
  • Ileum- 12 feet



Duodenum- complete digestion takes place here.
  • Receives enzymes from the pancreas and bile from the liver.



Jejunum- No digestion takes place here.


Ileum- absorption of digested food takes place here.
  • Has villi and microvilli for increasing the surface area
Functions of the small intestine: 
Digestion: 
Neutralize acid from stomach,
Add digestive enzymes and bile, 
breaks down proteins, carbohydrates and lipids to absorbable materials 


Absorption: 95% of food is absorbed here.


Structure 
Mucosa adaptations: villi containing blood capillaries and lacteal. 
Cells of villi have small projections - microvilli.

Villi in the small intestine

Small Intestine as principle site for absorption

  • 5-6m long- enough time for digestion and absorption.
  • Inner wall thrown into folds - increases the surface area for absorption.
  • Villi and microvilli- further increase the surface area.
  • Lacteals and blood vessels- facilitates easy absorption and transportation. 
  • Single layered epithelium- for easy diffusion of digested substances.

LARGE INTESTINE

  • About 5-6 feet long and 6 cm diameter
  • Divided into caecum, colon and rectum
  • Opening of the small intestine inoto caecum has valve- ileocaecal valve

Functions-
  • Absorption of water in the food
  • Secretion of mucus
  • Egestion of undigested waste

ASSOCIATED GLANDS 

Salivary glands

  • Secretion-Saliva  
  • Source: Parotid, sub-maxillary, sub-lingual 
  • Composition: mucin, salivary amylase, bicarbonate, lysozyme. 

Functions: 
  • Ptyalin- starch splitting enzyme 
  • Mucus- mixes with food and makes it soft for easy digestion. 
  • Polysaccharidase- dissolves the bacterial cell wall.

Gastric glands

Simple or branched tubular glands are present in the mucosa of the stomach.-  
Gastric juice.  
Cardiac glands- secrete mucus 
Pyloric glands- secrete mucus 
Fundic glands four types of cells 
  • Chief cells or peptic cells- pepsinogen, prorennin and gastric lipase. 
  • Oxyntic cells- HCl 
  • Goblet cells- mucus  
  • Argentaffin cell- serotonin 
  • Endocrine cells- gastric hormone 
Gastric enzymes- pepsinogen, prorennin and gastric lipase

Intestinal glands

Microscopic glands present in the mucosa of small intestine. 

Crypts of Lieberkuhn- multicellular, straight, tubular glands present throughout the mucosa. Secrete digestive enzyme and mucus. 

Brunner’s glands- compound tubular glands, found in the duodenum. Secrete alkaline watery juice. 

Intestinal secretion- the secretions from the intestinal glands is called succus entericus
http://1.bp.blogspot.com/_qW0F6VNbvlM/TS09u0PKvaI/AAAAAAAAACY/RH1zN0JC10Y/s320/Intestinal+gland.png

Intestinal enzymes

Carbohydrate digesting enzymes 

Intestinal amylase 
Maltase 
Sucrase 
Isomaltase 
Lactase 
Limit dextrase

Protein digesting enzymes

Enterokinase 
Aminopeptidase 
Dipeptidase 
Tripeptidase 
Nuclease 

Fat digesting enzymes

Intestinal lipase 

Pancreas 

Pancreas is a diffused leaf shaped gland. 
It is formed of exocrine part and endocrine part. Exocrine part is made up of lobules or acini.
Acinus is formed of glandular acinous cells. 
These cells secrete pancreatic juice. 
Enzymes in the pancreatic juice-
  • Trypsinogen (for proteins)
  • Chymotrypsinogen (for proteins) 
  • Procarboxypeptidase (for proteins)
  • Pancreatic amylase (amylopsin) (for carbohydrates) 
  • Pancreatic lipase (steapsin) (for fats)
Endocrine part is represented by patches of cells called islets of Langerhans.
Two main type of cells are seen-  
Alpha cells- produces glucagon. 
Beta cells- produces insulin.
http://www.gopetsamerica.com/anatomy/illustrations/pancreas.jpg

LIVER

Liver has two main lobes:- large right lobe and small left lobe. 
In addition – quadrate lobe and caudate lobe are present. 
  • Liver cells secrete bile, and is stored in gall bladder. 
  • Bile is a yellowish green secretion.  
  • Pigments- bilirubin and biliverdin 
  • Salts- Na glycocholate, Na taurocholate and Na bicarbonate. 
  • Bile is carried from gall bladder to duodenum by bile duct.

The gallbladder is located beneath the right lobe of the liver. The primary function of the gallbladder is to store and concentrate bile. 

Liver - Functions

The primary functions of the liver are:
  • Bile production and excretion
  • Synthesis of urea
  • Excretion of bilirubin, cholesterol, hormones, and drugs
  • Metabolism of fats, proteins, and carbohydrates
  • Enzyme activation
  • Storage of glycogen, vitamins, and minerals
  • Synthesis of plasma proteins, such as albumin, and clotting factors
  • Blood detoxification and purification

Lipogenesis- excess of glucose is converted to fats 

Glucose metabolism in the liver

Glycogenesis
Excess glucose in the blood is converted into glycogen and stored.
Glycogenoglysis
When required glucose is obtained by hydrolysis of glycogen.
Glyconeogenesis
Glucose is synthesized from amino acids or fatty acids and glycerol. 

Bilary system

  • The biliary system consists of the organs and ducts that are involved in the production and transportation of bile. 
  • The liver cells secrete bile, it is collected by a system of ducts that flow from the liver through the right and left hepatic ducts into common hepatic duct.
  • The common hepatic duct joins the cystic duct from the gallbladder to form the common bile duct, which runs from the liver to the duodenum. About 50 percent of the bile produced by the liver is first stored in the gallbladder, a pear-shaped organ located directly below the liver.
  • The gallbladder contracts and releases stored bile into the duodenum to help break down the fats when food enters the duodenum.
  • The opening of the common bile duct is guarded by the sphincter of Boyden, that then joins the hepato-pancreatic duct to open into the duodenum. 
  • This opening is guarded by the sphincter of Oddi. 
Bile is the greenish-yellow fluid (consisting of waste products, cholesterol, and bile salts) that is secreted by the liver cells to perform two primary functions:
  • To carry away waste
  • To break down fats during digestion
Food by mastication is converted to bolus in the mouth. 
It is passed to the stomach where churning and action of enzymes lead to formation of chyme, the partially digested food. 
In the duodenum, complete digestion takes place forming the chyle.

Watch the videos showing the process of digestion.

Home work assignment

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PHYSIOLOGY OF DIGESTION >