Chapter 6: Nutrition in Humans. A balanced diet is a diet which contains all the essential nutrients...
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Transcript of Chapter 6: Nutrition in Humans. A balanced diet is a diet which contains all the essential nutrients...
Chapter 6: Chapter 6: Nutrition in Nutrition in
HumansHumans
Chapter 6: Chapter 6: Nutrition in Nutrition in
HumansHumans
• A balanced diet is a diet which contains all the essential nutrients (carbohydrates, fats, proteins, vitiamins, minerals, water and dietary fibre) in the right proportions.
I need more proteins to synthesize new cells so
that I can grow big and tall.
• The nutrients required vary among individuals. For example, a growing child requires more protein than an older person to make new cells and teenagers require more carbohydrates for energy than an older person.
Nutrition• Nutrition is the process of taking in food and
converting it into living matter.
• In animals, nutrition consists of:
Ingestion (Taking in food)Digestion (Breaking down food)Absorption (Absorbing digested food into cells)Assimilation (Making use of absorbed food)Egestion (Removing undigested food)
INGESTION
DIGESTION
ABSORPTION
ASSIMILATION
EGESTION
Taking in food
Breakdown of complex food substances into smaller
soluble food substances
Digested food is absorbed Into body cells
Absorbed food is use to provide energy or form
new protoplasm
Removal of undigested food
Case Study 2:• The burger you ate yesterday
would like to travel from your stomach to your muscles. How would it go about
doing so?
The Digestive System
Consists of:
1) The gut or alimentary canal (9 m) from mouth to anus.
2) Glands (A cell, tissue, or organ that secretes a chemical substance).
3) Associated organs.
MOUTH(Buccal Cavity) PHARYNX
OESOPHAGUS(GULLET)
STOMACH
RECTUMANUS
ALIMENTARY CANAL
LARGEINTESTINE
SMALLINTESTINE
The Alimentary Canal
Overview
• Mouth & Buccal Cavity → Pharynx →
Oesophagus → Stomach → Small Intestine
→ Large Intestine → Anus.
LIVERGALL
BLADDERPANCREAS
THE ASSOCIATED ORGANS
Mouth & Buccal Cavity
The Mouth & Buccal Cavity
Buccal Cavity
The Mouth & Buccal Cavity
• Food enters through the mouth. This process is called ingestion.
• Teeth cuts food into small pieces. This increases surface area to volume ratio for enzyme to act more efficiently.
The Mouth & Buccal Cavity
• Salivary glands produce saliva to moisten food.
• Saliva also contains salivary amylase to break down starch to maltose.
• pH of saliva is neutral (around pH 7).
The Mouth & Buccal Cavity
Salivary Glands
The Mouth & Buccal Cavity
Starch Maltose Salivary Amylase
Salivary amylase is active at pH 7.
The Mouth & Buccal Cavity
• Tongue rolls food into boli.
• Food is swallowed and enters the pharynx.
Pharynx
Pharynx & Oesophagus
Pharynx
A common passage
for food & air.
Pharynx
• Connects buccal cavity to oesophagus.
• When swallowing, epiglottis (a flap-like tissue) covers wind pipe preventing entry of food into wind pipe.
Oesophagus
• 2 layers of muscles:
• Outer layer: Longitudinal muscles
• Inner layer: Circular muscles
• Longitudinal and circular muscles present throughout the wall of alimentary canal from oesophagus to rectum.
• Food moves along the alimentary canal by peristalsis.
Peristalsis
• A rhythmic, wave-like contractions of the gut wall.
• Caused by alternate contractions of the longitudinal & circular muscles.
• It helps to move food along the gut & mix food with digestive juices.
Peristalsis
• A muscular bag that can be stretched or expanded.
The Stomach
Walls of Stomach
Gastric Glands
Gastric Glands
•Walls of stomach contain gastric glands which secrete gastric juice.
•Food in stomach stimulates gastric glands to produce gastric juice.
The Stomach
• Peristalsis mixed food with gastric juice.
• Gastric juice contains:
1) Proteases (Pepsin & Rennin)
2) Dilute hydrochloric acid
Protein Digestion in Stomach
• Pepsin digests proteins to polypeptides.
Proteins PolypeptidesPepsin
Digestion of Milk Proteins
• Milk contains soluble protein caseinogen.
• Caseinogen passed through stomach too quickly for pepsin to digest.
• The protease, rennin curdles milk by converting soluble caseinogen to insoluble casein.
Caseinogen Casein (Soluble) (Insoluble)
Rennin
Casein Polypeptides(Insoluble)
Pepsin
The Stomach
Insoluble casein stays in stomach long enough for pepsin to act on.
The Stomach
• Peristalsis mixed food with gastric juice.
• Gastric juice contains:
1) Proteases (Pepsin & Rennin)
2) Dilute hydrochloric acid
Dilute Hydrochloric Acid
• Create pH 2 environment in stomach.
• Stops activity of salivary amylase.
• Activate proteases pepsin and rennin.
• Provide pepsin with a suitable pH environment to work in.
• Kills bacteria in food.
The Stomach
Oesophagus
Pyloric Sphincter
Partially digested food in stomach is called chyme. (acidic)
Small Intestine
Small Intestine
• Around 6 m long.
• Divided into 3 parts:
- Beginning part: duodenum
- Middle part: jejunum
- Last part: ileum
• Presence of chyme in duodenum stimulates release of 3 substances:
- Pancreatic juice
- Intestinal juice
- Bile
• All these fluids are alkaline. They neutralise the acidic chyme.
Pancreatic Juice
• Produced by pancreas.
• Passed through pancreatic duct into duodenum.
Pancreatic Juice
Contains the following enzymes:
• Pancreatic amylase
(Digests starch to maltose)
• Trypsin
(Digests proteins to polypeptides)
• Lipase
(Digests fats to fatty acids & glycerol)
Pancreatic Juice In Duodenum
Starch Maltose Pancreatic Amylase
Proteins PolypeptidesTrypsin
Fats Fatty acids + GlycerolLipase
Intestinal Wall
Intestinal glands
Intestinal Juice
• Intestinal glands produce intestinal juice, which contains:
• Maltase (Digests maltose to glucose)
• Erepsin (Digests polypeptides to
amino acids)
• Lipase (Digest fats to fatty acids & glycerol)
Intestinal Juice In Duodenum
Maltose Glucose Maltase
Polypeptides Amino acids
Fats Fatty acids + GlycerolLipase
Erepsin
Intestinal juice also contains sucrase and lactase.
Bile
An alkaline greenish-yellow fluid.
Bile• Bile is produced
by liver cells.
• It is stored in the gall bladder.
Liver
• Bile passed through the bile duct into duodenum.
Bile
Bile
• Bile does not contain enzymes.
• Bile is made up of bile pigments and bile salts. Bile pigments give bile its colour.
• Bile salts help in the digestion of fats.
Bile Salts Emulsify Fats
Large fat drop
+ Bile Salts
Tinyfat droplets
• By breaking fats into smaller droplets (Emulsification), bile salts increase surface area to volume ratio of fats for digestion by lipase.
Tinyfat droplets
Bile Salts Emulsify Fats
MOUTH(Buccal Cavity) PHARYNX
OESOPHAGUS(GULLET)
STOMACH
RECTUMANUS
ALIMENTARY CANAL
LARGEINTESTINE
SMALLINTESTINE
1. MOUTH•MASTICATION•SALIVARY GLANDS secrete saliva (ph 7) - MUCIN MOISTEN FOOD - Salivary amylase : Starch MALTOSE
2. OESOPHAGUS•No digestion
3. STOMACH ( acidic pH)• gastric Glands produce gastric juice - Hydrochloric Acid : kills bacteria, activate protease - Pepsin : - Renin :
Protein Polypeptide
Caseinogen Casein (Insoluble) (soluble)
INTESTINAL GLANDS
4. SMALL INTESTINE
BILEPANCREATIC
JUICEINTESTINAL
JUICE
PANCREAS LIVER via Bile duct
Pancreatic Amylase
Trypsin
Pancreatic Lipase
Maltase, Sucrase, Lactase
Erepsin (Peptidase)
Intestinal Lipase
Quiz on Digestion
• 1. Involuntary muscle contractions which
move a bolus through the gastrointestinal
tract are called ____________________
• 2. Hydrochloric acid is secreted in the
_____________________.
• 3. Polypeptides is broken down into amino
acids by the enzyme ___________ found in
intestinal juice.
• 4. Name the 2 proteases found in the
stomach.
• 5. Which organ produces bile?
• 6. How does bile aids in digestion of food?
INGESTION
DIGESTION
ABSORPTION
ASSIMILATION
EGESTION
Taking in food
Breakdown of complex food substances into smaller
soluble food substances
Digested food is absorbed Into body cells
Absorbed food is use to provide energy or form
new protoplasm
Removal of undigested food
Absorption of digested food substances
• End products of digestion are simple molecules
-Simple sugars (glucose, fructose and galactose)
-Amino acids -fatty acids & glycerol.
• Main site of absorption – ileum of small intestine
How is the small intestine adapted for absorption?
VIDEO
To increase the surface area for absorption:
• The inner walls of the small intestine have numerous foldings.
Villi
• Inner walls of small intestine is lined with finger-like projections called villi.
• Villi help to increase surface area for absorption of digested food substances.
One-cell Thick Epithelium
• Epithelium – The surface layer
• The villi have epithelium that is very thin (only one-cell thick).
• This allows digested food substances to pass through easily.
Microvilli
• The epithelial cells (cells on the surface) of the villi have microvilli.
• This further increases surface area for absorption.
Figure 14.9Slide 14.10ACopyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
The Wall of the Small Intestine
The small intestine is well supplied with blood capillaries and lacteals to carry the absorbed food substances.
This helps maintain the concentration gradientfor absorption of digested food substances.
Amino acids and glucose enters blood capillaries of the villi.
Fatty acids and glycerol diffuses into villi and enter lacteals as fat molecules.
Blood capillaries
Lacteal
Small intestine is long enough ( 6 m ) to provide sufficient time for absorption.
The Large Intestine
Most water is absorbed in ileum.
Colon absorbs water and mineral salts.
Egestion
• Undigested materials are stored temporarily in rectum and will be egested through the anus.
Transport and Assimilation of Food Substances
Hepatic Portal Vein
• Sugars and amino acids absorbed into small intestine will be transported to the liver via the hepatic portal vein.
Functions of The Liver
In Liver,
• Liver converts Excess Sugar to glycogen for storage.
• Some of the glucose leave the liver and distributed around the body.
•
• When concentration of glucose in blood is high,
Pancreas will produce the hormone insulin: causes the liver to convert glucose to glycogen.
• Blood glucose concentration returns to normal.
• When the concentration of glucose in blood is low,
Pancreas will produce the hormone glucagon which causes the liver to convert glycogen to glucose.
• Glucose enters blood, blood glucose concentration returns to normal.
1) Liver regulates the concentration of glucose in blood.
AMINO ACID
NH2 COOH
R
C
H
Amino group
Acidic group
Hydrocarbon side chain
2) Deamination of Amino Acids
• Excess amino acids are broken down in liver.
• Amino group → ammonia (toxic to cells) → Urea (non-toxic, removed in urine).
• This process is called deamination.
• Remaining amino acid molecule is converted into glucose and stored as glycogen in the liver and muscles.
Functions of Liver
3) Produces bile for the emulsification of fats.
4) Worn out red blood cells are destroyed in spleen and the haemoglobin is transported to the liver. Liver breaks down haemoglobin and stores the iron released.
5) Detoxification - Breaks down alcohol.
Effects of excessive alcohol consumption:
• Alcohol stimulates acid production in stomach, increasing risk of gastric ulcers.
• Alcoholic cirrhosisCirrhosis is a condition where normal liver tissue is replaced by scar (fibrous) tissue. The scar tissue affects the normal structure and re-growth of liver cells. Liver cells become damaged and die as scar tissue gradually develops. So, the liver gradually loses its ability to function. Prolonged alcohol abuse destroys liver cells, causing bleeding in liver resulting in liver failure and death.
Jigsaw Puzzle