nutrition in human

• Ingestion is the process where food is ingested into the mouth.
• Reduced self-control as alcohol takes away inhibitions
• Digestion is the process where large food molecules are broken down into smaller, soluble molecules that can be absorbed into the body cells.
• Digestion involves physical break up of large pieces into smaller pieces and chemical breakdown of bonds (enzymes).
• Absorption is the process where the digested food substances are absorbed into the body cells.
• The small intestine absorbs basic units (glucose, amino acids, fatty acids and glycerol) into the bloodstream.
• Assimilation is the process where some of the absorbed nutrients are converted into new cytoplasm or used to provide energy.
• Egestion is the process where undigested food is removed from the body.
• The mouth involves ingestion and digestion (physical and chemical), teeth (physical) which breaks large pieces of food into smaller pieces to increase SAVR for the digestion of starch by salivary amylase, tongue which mixes the food with saliva and rolls the food into a bolus, and pushes the bolus into oesophagus during swallowing, and salivary amylase (chemical) which breaks down starch in food into maltose.
• The salivary glands produce saliva which contains mucus and salivary amylase, softens food, and is alkaline.
• The oesophagus involves peristalsis, a process whereby the digested food substances are pushed or squeezed forward by the circular and longitudinal muscles.
• The stomach involves digestion, peristalsis, and the production of gastric juice which contains pepsin, hydrochloric acid and mucus.
• The duodenum involves digestion, absorption, and peristalsis, and emulsification where pancreatic amylase breaks down starch into maltose, maltase breaks down maltose into glucose, protease breaks down proteins into short polypeptide chains, and peptidase further digests short polypeptide chains into amino acids.
• Fats are transported and utilised by absorption into lymphatic capillaries, and joining to form larger lymphatic vessels, which discharge fats into the bloodstream.
• Alcohol increases the risk of liver cirrhosis, gastric ulcers, and slows down brain function.
• Glucagon stimulates the liver to convert glycogen into glucose to be released into the bloodstream, causing the blood glucose concentration to increase to normal level.
• Hormones, fats, and toxic substances are broken down and detoxified by liver cells.
• The colon absorbs the remaining water and mineral salts from the undigested food.
• Glucose and amino acids are absorbed by diffusion and active transport into the blood capillaries of the villi, glycerol and fatty acids diffuse into the epithelium, and combine to form minute fat globules that enter the lacteals.
• Deamination of amino acids involves deaminating excess amino acids, removing the amino groups and converting them into urea, and converting the remains of the deaminated amino acids into glucose.
• Insulin stimulates the liver to convert excess glucose into glycogen for storage, causing the blood glucose concentration to decrease to normal level.
• Faeces are stored temporarily in the rectum and expelled through the anus when the rectum contracts.
• Bile is stored temporarily in the gall bladder.
• Intoxication increases reaction time observed through slurred speech, blurred vision and poor muscular coordination.
• The small intestine is adapted for its function by being relatively long and its inner surface highly folded to increase the surface area for absorption, having one-cell thick epithelium to provide a short diffusion distance for diffusion and active transport, and having epithelial cells with many microvilli to further increase the surface area for absorption.
• When the blood glucose concentration drops below normal level, the islets of Langerhans in the pancreas is stimulated to secrete more glucagon into the bloodstream.
• Liver cells produce and secrete bile which does not contain enzymes.
• The pancreas produces and secretes pancreatic juice which contains pancreatic amylase, protease and pancreatic lipase, and islets of Langerhans which secrete hormones insulin and glucagon into the bloodstream.
• The gall bladder stores and releases bile, stores bile temporarily, and when gall bladder contracts, bile flows into the duodenum via the bile duct.
• The liver involves hepatic portal vein which transports glucose and amino acids from small intestine to the liver, hepatic vein to the heart, and hepatic artery away from the heart.
• The liver is involved in the production of bile and assimilation.