Nutrition in Humans (chap5) Flashcards
Ingestion
Food is taken into the body.
Digestion
Large food molecules are broken down into smaller, soluble molecules that can be absorbed by the body.
Assimilation
Nutrients are used by cells for maintenance of the body.
absorbed food substances are converted into new protoplasm.
For example: to provide energy or for making new protoplasm for growth
Egestion
Undigested matter is removed from the body.
Absorption
Nutrients are moved from the intestines into the bloodstream.
For example, to provide energy or for making new cytoplasm for growth.
nutrition
is the process by which organisms obtain food and energy for growth, repair & maintenance of the body.
human digestive system consists of;
gut or alimentary canal & organs (liver/gall bladder/pancreas) associated with it
alimentary canal
(from? to?)
mouth to anus
teeth
break up large pieces of food into smaller pieces.
chewing increases surface area to volume ratio of food so enzymes can act on it more efficiently.
salivary glands
secrete saliva into the mouth
Tongue
Helps in mixing of food with saliva and moving the food to the back of the mouth during swallowing
break up
physical process
eg: emulsidification/chewing
break down
digestion
chemical process involving enzymes
the Pharnyx
connects the buccal cavity to the oesophagus & the larynx (voice box)
the Pharnyx
connects the buccal cavity to the oesophagus & the larynx (voice box)
the Oesophagus
narrow, muscular tube that joins mouth to stomach.
muscle contact & relax to move food along the tube
the stomach
a distensible muscular bag.
Thick and well-developed muscular walls.
the inner surface if the stomach wall has numerous pits that open to gastric glands.
gastric glands
secrete gastric juice.
contains hydrochloric acid and protease.
pH 2, which gives an acidic environment that is optimal for protease to digest proteins.
the small intestine
absorbs water and nutrients from food.
lining of small intestine contains glands that secrete digestive enzymes such as maltase, lipase & intestinal protease.
constsists of: duodenum, illeum
ileum
inner surface of ileum is folded extensively & has numerous finger-like projections called villi. (singular villus)
this increases rate of absorption of digested food, mineral salts & most of the water into the bloodstream.
the large intestine
absorbs 90% of remaining water & remaining salts.
consists of: colon, rectum & anus
plays a role in the egestion of undigested & unabsorbed nutrients from the body
rectum
a short muscular tube.
temporary stores undigested food material as faeces.
when contracts, faeces are expelled through anus.
the Liver
largest gland in the body.
attached to 3 blood vessels: hepatic portal vein, hepatic vein, hepatic artery.
Liver cells produce & secrete bile.
bile
aids in the physical digestion of fats through emulsidification
alkaline, greenish-yellow liquid contaning bile salts.
does not contain enzymes
hepatic portal vein
carries blood containing absorbed nutrients from walls of small intestine, blood capillaries converge to form the hepatic portal vein, carries blood to liver
hepatic vein
carries deoxygenated blood away from liver (back to the heart)
hepatic artery
carries oxygenated blood from small intestine to liver
the gall bladder
temporarily stores bike after it is produced by the liver.
contacts to release bile into small intestine through bile duct, to aid in digestion of fats
the Pancreas
connects to the duodenum by the pancreatic duct.
produces pancreatic juice that contains digestive enzymes like amylase, lipase & protease.
secretes the hormones(from the islets of langerhans) , insulin & glucagon
physical digestion
increases surface area to volume ratio to i crease efficiency of chemical digestion.
releases nutrients from food during chewing.
breaks down food mechanically, from large pieces of food into smaller pieces of food
chemical digestion
break down of insoluble food molecules into smaller souble food molecules for easier absorption.
specific enzymes catalyse the chemical reactions.
processes that take place in the mouth
- ingested food stimulates salivary glands to secrete saliva.
- saliva mixed with food to soften it.
- tongue rolls food into small boli
- boli are swallowed - > oesophagus via pharynx
- push to stomach
physical digestion:
-teeth chew food into smaller pieces
chemical digestion:
-starch -(salivary amylase)-> maltose
processes that take place in the stomach
presence of food stimulates gastric glands to secrete gastric juice into stomach.
churning of the stomach helps to mix food with gastric juice
gastric acid contains;
dilute hydrochloric acid
mucus
enzyme pepsin (protease)
dilute hydrochloric acid
(found in gastric juice)
denatures salivary amylase present in food boli.
low pH environment (pH2) for enzyme.
kills certain potentially harmful microorganisms.
mucus (found in gastric acid)
protects stomach wall against being digested by enzymes.
allows easy movement by moistening food.
enzyme pepsin (found in gastric acid)
food remains stomach for 3-4hours.
becomes liquefied, formes chyme.
chyme passes in small amounts into duodenum, when phyloric sphincter relaxes & opens.
processes that take place in the small intestine
when chyme enters the duodenum, it stimulates:
secretion of pancreatic juice -> passes through pancreatic duct into duodenum.
contains amylase, lipase, protease.
epithelial cells also secrets maltase lipase & protease
carbohydrate digestion
food we eat may contain carbohydrates such as starch, sucrose & cellulose.
digested by carbohydrases such as amylase and maltase.
begins in mouth (little)
none in stomach (no carbohydrases)
fully digested in small intestine (into simple sugars - glucose-)
protein digestion
begins in stomach
Protein -> digested in the stomach / small intestine by protease -> linear polypeptides -> digested in small intestine (duodenum) by trypsin/erepsin -> amino acids
fat digestion
occurs in duodenum.
bile salts emulsify fats by reducing the attractive forces between the fat molecules.
this increases exposed surface area.
fats ->lipase(pH8) -> fatty acids + glycerol
what’s digested in small intestine?
starch
maltose
fats
proteins
polypeptides
which 3 organs produce enzymes that digests proteins
pancreas - pancreatic juice
stomach - gastric acid
small intestine - epithelial cells
name 2 glands that produce amylase
pancreas
salivary glands
name 3 glands involved in digestion
salivary glands
pancreas
gastric glands
insulin/glucagon is secreted by?
the islets of langerhans in the Pancreas
how are glucose & amino acids transported and utilised?
in the ileum, glucose & amino acids are absorbed into the blood capillaries.
hepatic portal vein transports the nutrients from the small intestine to the liver.
in the liver muscle, hormone insulin stimulates liver to convert excess glucose to glycogen.
glycogen is stored in liver.
Excess amino acids are deaminated into urea.
hepatic vein transport nutrients to the rest if the body.
Glucose is used as a substrate in cellular respiration to release energy for the cell.
amino acids are synthesised into new protoplasm for cell growth and repair.
amino acids are also used to synthesise enzymes & hormones.
how are fats transported and utilised?
fats are absorbed into the bloodstream. blood carries the fats to every part of the body, including the liver.
in liver, fats are converted into forms that can either be broken down or stored.
under normal conditions when there is a sufficient supply of glucose, fats are not utilised for respiration. instead, fats are used to build protoplasm. (eg. cell membranes)
when glucose is in short supply (eg. fasting) fats are broken down to provide the energy needed for vital activities for the body.
excess fats are stored special tissues called adipose tissues, which can be found beneath the skin, around the heart & kidneys.
adipose tissues protect these organs by acting as shock absorbers.
what happens when glucose level decreases below normal?
hormone glucagon stimulates liver to convert glycogen into glucose; to be released into the bloodstream.
blood glucose concentration goes back to normal
what is the role of the Liver?
- production of bile
- deamination of amino acids
- detoxification
- regulation of blood glucose concentration
-breakdown of hormones
production of bile
liver plays an important role in fat digestion.
helps by secreting bile which is temporarily stores in the gall bladder before use.
deamination
is the process by which amino groups are removed from amino acids and converted into urea.
deamination of amino acids
excess amino acids are transported to Liver.
Their amino groups are removed and converted to urea.
remains of the deamintaed amino acids are converted to glucose in the liver.
any access glucose formed is converted into glycogen.
urea is removed from the body through urine.
detoxification
harmful substances may be absorbed from the gut. (eg. Alcohol, which can cause damage to digestive system and slow down brain functions/increase reaction time)
these are made harmless by Liver cells.
Liver cells contain an enzyme which breaks down alcohol to compounds that can be used in respiration, providing energy for cell activities.
the process of converting harmful substances into harmless ones is known as detoxification.
regulation of blood glucose concentration
body cells need glucose for cellular respiration. (provides cells with energy to perform their vital activities)
drastic change in bllad glucose concentration can be dangerous.
normally about 70-90mg of glucose per 100cm3 of blood.
Glucose levels in blood rises after sugary meal, and fall during vigorous excersize or starvation.
Liver does this with the help of hormones
what is a hormone
a Hormone is a chemical substance produced in very small quantities by an endocrine gland. it is transported in the bloodstream to target organ(s) to exert its effect(s).
hormones can influence growth, development & activity of an organism.
they are chemical messengers that help the various parts of the body respond, develop & work together smoothly.
where are hormones produced?
hormones are produced & secreted by glands into the bloodstream
what happens when blood glucose concentration increases above normal?
pancreas detects this change and produces insulin. (transported in the blood to target organs; liver & muscle cells)
(state how insulin reduces blood glucose concentration)
how does insulin reduce blood glucose concentration?
making cell membranes more permeable to glucose, allowing more glucose to diffuse into liver & muscle cells.
stimulating liver & muscle cells to convert exve# glucose into glycogen for storage.
increasing use of glucose of respiration.
breakdown of hormones
after hormones served their purpose, it is broken down in the liver.
This is important to ensure hormone does not prolong their effects. (could be detrimental to health)
Diabetes
when body is unable to control its blood glucose concentration.
as a result, the blood glucose concentration can rise to a level that exceeds the kidney’s ability to completely reabsorb all the glucose. -> excreted in urine.
Type 1 diabetes
cells in pancreas that produced insulin are destroyed.
little to no insulin can be produced.
Type 2 diabetes
develops when target cells (eg. muscle cells) do not respond well to insulin -> insulin resistence.
or
when body is unable to produce enough insulin
what causes type 2 diabetes?
insulin resistence. blood sugar concentration remains high;
glucose is absorbed from small intestine into blood stream
or
pancreas does not produce enough insulin, less insulin is secreted into bloodstream.
muscle & liver cells are unresponsive to insulin. less glucose is taken into the cells. blood glucose concentration remains high
risk factors of type 2 diabetes
obesity
sedentary lifestyle
family history
blood lipid levels ( ‘bad’ cholesterol)
age
Explain how blockage of pancreatic duct can cause malnutrition
Digestion of fats/proteins/carbohydrates is affected.
Due to pancreatic enzymes not able to reach duodenum.
Lead to malabsorption.
Describe how glucose gets from the alimentary canal to the cells where it is used
Glucose is absorbed by the micro villis on the walls of the small intestine, into the bloodstream.
The blood, which is rich in glucose, flows through capillaries that converge into the hepatic portal vein. Glucose is then transported via the hepatic vein to the rest of the body and is taken up by the cells to be used for respiration.
Peristalsis
Muscles contract & relax to move food along the oesophagus
