Nutrition in Humans Flashcards
define nutrition
- the process by which organisms obtain food&energy
- needed for growth, repair and maintenance of body
state the 5 processes (in order)
- feeding/ingestion
- digestion
- absorption
- assimilation
- egestion
define feeding/ingestion
food taken into body
define digestion
large insoluble food molecules broken down into smaller soluble molecules
define absorption
digested food molecules absorbed into cells
define assimilation
food molecules converted into new protoplasm to provide energy
define egestion
undigested food removed from body
the mouth and buccal cavity
-food enters body thru the mouth which leads to the buccal cavity
teeth (physical digestion)
2 pts
- chewing action breaks down large food molecules into smaller food molecules
- increases SA:V allowing enzymes to act on food molecules more efficiently
salivary glands (chemical digestion) (3 pts)
- secretes saliva into mouth
- saliva flows into buccal cavity via tubes called salivary ducts
- saliva contains salivary amylase (starch to maltose)
tongue
2 pts
- taste buds help identify and select suitable foods
- mix food with saliva, rolls food into bolus
define the pharynx and where it leads to
4 pts
- connects the buccal cavity to oesophagus and larynx
- also lead to trachea (windpipe), to lungs
- part of both respiratory and digestive system
- food&air pass thru
If both food and air must pass thru the pharynx to enter the oesophagus and trachea, how is food prevented from entering the trachea when swallowing?
epiglottis, opens and closes the glottis
what happens during breathing and swallowing?
3 pts
- larynx has a slit-like opening (glottis), covered by a flap-like tissue (epiglottis)
- breathing: air passes thru trachea, larynx moves downwards, glottis is open
- swallowing: larynx moves upwards, epiglottis covers glottis, preventing food particle from entering trachea
define the oesophagus and gullet and what it is made of
3 pts
- narrow, muscular tube passes thru thorax (chest) and diaphragm to join stomach
- wall made up of 2 layers of muscles: longitudinal (outer) & circular (inner)
- muscles present along the whole gut from the oesophagus to rectum
define longitudinal &circular muscles and what it does
3 pts
- antagonistic muscles (pair of muscles where movements oppose each other)
- produces long slow contractions
- these contractions move food along gut via peristalsis
define peristalsis and what it does
3 pts
- the rhythmic, wave-like muscular contractions in the wall of the alimentary canal
- enables food to be mixed with digestive juices
- pushes/propels food along gut
define the stomach
3 pts
- a distensible muscular bag
- thick and well-developed walls
- when it is fully distended, it sends signals to the brain that it is full
gastric glands
3 pts
- the stomach wall has numerous pits that lead to gastric glands
- gastric glands secrete gastric juice into stomach cavity
- gastric juice digests food
sphincters
-rings of muscles that contract to retain food in stomach for digestion
cardiac sphincter
entrance, relaxes to allow food to enter stomach
pyloric sphincter
exit, relaxes to allow chyme (semi-digested food) to leave stomach
what is the small intestine made up of?
duodenum, jejunum and ileum
define the small intestine
4 pts
- abt 6m long
- absorbs more water than large intestine
- lining of small intestine walls contain glands which secrete digestive enzymes
- adapted to absorb digested food and water
what is the large intestine made up of?
- consists of the colon and rectum
- abt 1.5m long
state the other glands associated with the gut
liver, pancreas, gall bladder
define physical digestion and where it occurs
3 pts
- involves mechanical break-up of food into smaller pieces
- chewing, churning or peristalsis
- occurs in mouth and stomach
define chemical digestion and which reaction/s are involved
- involves break-down of large complex molecules into small simple molecules that can be absorbed
- involves hydrolytic reactions catalysed by digestive enzymes
digestion in the mouth
5 pts
- chewing action by teeth breaks up large pieces of food into smaller pieces, increasing SA:V for amylase to work on
- tongue rolls food into small, slippery round masses called boli
- salivary glands in mouth secrete saliva, mixed with food by tongue
- saliva contains mucin which softens food
- salivary amylase breaks down starch into maltose
digestion in oesophagus
3 pts
- boli are swallowed and passed down into oesophagus via the pharynx
- peristalsis in walls of oesophagus and gravity push bolus into stomach (physical)
- amylase in saliva continue to break down starch (chemical)
digestion in stomach
2 pts
- when bolus enters stomach, stimulates the release of gastric juice by gastric glands (chemical)
- peristalsis in walls of stomach churns and breaks down food, mixing food with gastric juice (physical)
define gastric juice
2 pts
- dilute solution of hydrochloric acid (pH2), mucus and 2 enzymes (pepsin and rennin)
- mucus protects stomach lining from hydrochloric acid (absence can result in stomach ulcers)
role of hydrochloric acid
4 pts
- denature salivary amylase
- converts pepsinogen and prorennin into pepsin and rennin respectively
- provides an acidic medium for action of pepsin and rennin (optimum pH:2)
- kills harmful microorganisms in food
state the actions of pepsin and rennin
2 pts
- pepsin digests proteins into polypeptides
- rennin converts soluble caseinogen into insoluble casein
digestion in small intestine
4 pts
chyme(semi-digested food) enters duodenum, stimulating the release of:
- intestinal juice by intestinal glands
- pancreatic juice by pancreas
- bile by gall bladder
pH level in small intestine
2 pts
- alkaline fluids neutralize the acidic chyme
- alkaline medium needed for the action of intestinal and pancreatic enzyme
Gall bladder and bile (Small intestine)
3 pts
- gall bladder releases its stored bile
- bile passes thru bile duct into duodenum
- bile salts speed up digestion of fats
Pancreas and pancreatic juice
2 pts
- pancreas secretes pancreatic juice
- contains pancreatic amylase, pancreatic lipase and trypsinogen (inactive trypsin)
Intestinal juice
2 pts
- secreted by intestinal glands
- contains peptidases, maltase, sucrase, lactase and intestinal lipase
how are different foods digested
3 pts
- amylase act on carbohydrates
- proteases work on protein
- lipases work on fats
how are carbohydrates digested
6 pts
mouth: starch to maltose (salivary amylase)
small intestine:
-starch to maltose (pancreatic amylase)
-maltose to glucose (maltase)
-lactose to glucose+galactose (lactase)
-sucrose to glucose+fructose (sucrase)
(end products are simple sugars that can be absorbed into bloodstream)
how are proteins are digested
4 pts
stomach:
-protein to polypeptides(pepsin)
small intestine:
-trypsinogen to trypsin (enterokinase)
-proteins to polypeptides (trypsin)
-polypeptides to amino acids (peptidases)
how are fats digested
5 pts
- bile salts emulsify fats
- reduce attractive force between fat molecules
- break down fat into small fat droplets that are suspended in water to form an emulsion
- increase SA:V of fat molecules, speeding up digestion by lipase
- fats broken down into fatty acids+glycerol (pancreatic and intestinal lipase)
where is the site of absorption?
small intestine
how is the rate of absorption influenced?
3 pts
- surface area
- thickness of membrane that separates food substances from blood capillaries
- concentration gradient of individual food substances
3 adaptions that makes absorption more efficient in the small intestine
(3 pts)
- large surface area
- thin separating membrane
- steep concentration gradient (diff in conc must be large)
how is the small intestine adapted for absorption? (villi)
2 pts
- SA:V ratio increased
- thin walls of villi (1 cell thick), easy for nutrients to pass thru to bloodstream
how is the small intestine adapted for absorption? (length of small intestine)
(2 pts)
- length of small intestine (6m) increase time for absorption
- more time for more nutrients to be absorbed
how is the small intestine adapted for absorption? (lacteal/lymphatic capillary)
(3 pts)
- in each villus is a lacteal/lymphatic capillary surrounded by blood capillaries
- many capillaries present to help carry away absorbed nutrients quickly
- continual transport of nutrients by capillaries maintain the concentration gradient required for absorption
what does the blood capillaries network transport?
2 pts
amino acids and glucose to body
what does the lacteal/lymphatic capillary transport?
1 pt
fats to body
how are nutrients absorbed in small and large intestine?
2 pts
diffusion and active transport
diffusion in small and large intestine
2 pts
- glucose, other monosaccharides and amino acids diffuse into blood capillaries
- glycerol and fatty acids diffuse into epithelium combined to form minute fat globules which enter the lymphatic capillary
what happens to undigested and unabsorbed matter and what is the process called?
(2 pts)
- stored temporarily in rectum and discharged as faeces thru anus
- discharging of faeces from body is known as egestion (undigested matter) or defecation, not excretion (metabolic waste like urea/CO2)
how are nutrients absorbed and utilized?
hepatic portal vein and lymphatic capillaries
- blood capillaries that supply small intestine untie to form hepatic portal vein
- the vein transports sugars and amino acids to liver
- lymphatic capillaries join to form larger lymphatic vessels, which discharge fats into bloodstream
state the absorbed food products
3 pts
glucose, fats, amino acids
how is glucose utilised?
used for respiration to produce energy for cellular activities
what happens to excess glucose?
converted to glycogen and stored in liver and muscles
how is amino acids utilised?
synthesis of proteins and protoplasm for growth and repair of cells
what happens to excess amino acids?
cannot be stored and is deaminated in liver to form urea
how is fats utilised?
synthesis of cell membrane
what happens to excess fat?
stored in fat tissues or adipose tissues
state the functions of the liver
5 pts
- regulation of blood glucose concentration
- production of bile
- deamination of amino acids
- storage of iron
- detoxification
regulation of blood glucose concentration (liver)
3 pts
- keeps blood glucose conc constant (70-90mg/100ml og blood)
- liver stimulated by insulin(lowers bg) and glucagon(increase bg) to store and release glucose respectively
- regulates metabolism of carbohydrates
how does insulin control carbohydrate metabolism?
3 pts
- too much glucose in blood, islets of Langerhans (pancreas) secrete insulin
- liver converts excess glucose into glycogen
- bg level decreases
how does glucagon control carbohydrate metabolism?
3 pts
- too little glucose in blood, islets of Langerhans (pancreas) secrete glucagon
- liver converts glycogen into glucose
- bg level increase
why do we experience hunger pangs? (regulation of blood glucose concentration)
(3 pts)
- when brain receives blood low in glucose, sends impulses to stomach
- strong contractions of empty stomach occur (hunger pangs)
- when bg conc rise, strong contractions stop, hunger pangs disappear
production of bile (liver)
2 pts
- liver produces bile which emulsifies fats
- stored temporarily in gall bladder before use
deamination of amino acids (liver)
5 pts
- liver uses amino acids to synthesize proteins such as albumins, globulins, fibrinogen (major blood proteins)
- amino group of amino acids removed (deamination) and converted to urea in liver
- deamination is the process by which amino grps(NH2) are removed from amino acids and converted to urea
- carbon residues of amino acids from deamination converted to glucose in liver
- excess glucose formed in this way is converted to glycogen
storage of iron
3 pts
- when rbc wear out, destroyed in spleen, haemoglobin is sent to liver to be “recycled)
- breakdown of haemoglobin produces iron which is stored in the liver and used in the synthesis of new rbc
- breakdown of haemoglobin produces bile
detoxification of liver
2 pts
- process of converting harmful substances into harmless products to not poison our cells
- enzyme alcohol dehydrogenase converts alcohol into acetaldehyde which can be broken down during respiration to energy for cell activities
state the harmful effects of excessive alcohol consumption
4 pts
- symptoms of drunkenness
- stimulates acid secretion in the stomach, increased risk of stomach ulcer
- cause liver cirrhosis, liver cells are destroyed and replaced with fibrous tissue
- frequent intake may lead to addiction
