Food: source of energy and essential molecules optimal diet: more carbohydrates than fats and...
-
Upload
cuthbert-parks -
Category
Documents
-
view
219 -
download
0
Transcript of Food: source of energy and essential molecules optimal diet: more carbohydrates than fats and...
• Food: source of energy and essential molecules
• optimal diet: more carbohydrates than fats and significant of protein
DIGESTION
• Carbohydrates: cereals, grains, breads– 4 calories per gram
• fats: oils, margarine, butter, fried foods, meats, snack foods– 9 cal/gram
• Proteins: poultry, fish, meat– 4 cal/gram
• Fiber: part of plant cannot be digested by humans– diets low in fiber result in a slow passage of food through
the colon, associated with colon cancer
• essential minerals: calcium, phosphorous, iron• Essential vitamins: vit A, B, D, C
A healthful diet satisfies three needs:
– Fuel for an organism’s activities
– Raw materials for biosynthesis
– Essential nutrients
– Vegetarians must be sure to obtain all eight essential amino acids
0
Obesity is a human health problem:
– usually caused by lack of exercise and abundance of fattening foods
– May partly stem from an evolutionary advantage of fat hoarding
• Research on mice: Has shown that a defect in the gene for leptin may cause obesity
0
• wealthy countries: overweight 65%• body mass index (BMI): estimate of body weight in kg, divided by height in meters2
DIGESTIVE SYSTEM
• alimentary canal: separate mouth and anus to transport of food is one way
• physical forces, chewing and grinding, first breaks the ingested food into smaller fragments
• chemical digestion, hydrolysis reactions that liberate the subunits
• products of digestion are transported by the blood• molecules not absorbed are excreted
• digestive system parts:– gastrointestinal
tract– accessory organs
Digestion begins in the oral cavity
• Teeth: break up food
• omnivores teeth are specialized for eating both plant and animal material: Carnivores: front of the mouth, Herbivores: in the back
• children have only 20 teeth/// Adults: 32 adult
• Saliva: moistens it
• salivary enzymes begin the hydrolysis of starch
• Tongue: pushes the bolus of food into the pharynx
0
Teeth
IncisorsCanine
PremolarsMolars
Tongue
Salivaryglands
Opening of asalivary gland duct
The food and breathing passages both open into the pharynx
– food is prevented from going into the respiratory tract by the epiglottis
The swallowing reflex: Moves food from the pharynx into the esophagus, while keeping it out of the trachea
0
Tongue
Pharynx
Larynx
Trachea (windpipe)Esophagus
Esophagealsphincter
Epiglottisup
Bolus of food
Sphincter contracted Sphincter relaxed Sphincter contracted
Epiglottisdown
Larynxup
Esophagus
Epiglottisup
Larynxdown
The esophagus squeezes food along to the stomach by peristalsis
food from the esophagus into the stomach is controlled by a ring of muscle, sphincter
- when relaxed>>> stomach contents can be brought back out during vomiting and lead to acid reflux or heartburn
0
Bolus offood
Muscles relax,allowing passagewayto open
Stomach
Musclescontract,constrictingpassagewayand pushingbolus down
Muscles contract
Muscles relax
Muscles contract
Musclesrelax
The Heimlich maneuver can save lives: dislodge food from the pharynx or trachea during choking
0
• Stomach:– saclike smooth muscle for churning food– Substances release:
• gastric juice • hydrochloric acid (HCl) with low pH to denature proteins and kill
bacteria• pepsin for digestion of proteins
Bacterial infections, Helicobacter pylori, in the stomach and duodenum are associated with ulcers
0
• Intestines– Types:
• Small: carbohydrates, protein, and lipids are broken down and absorbed into the bloodstream
• Large: production of waste or feces
• small intestine:– Parts:
• Duodenum: first part where “real” digestion and absorption of food is done
• Jejunem: digestion continues• Ileum: water and digested products
are absorbed
• Folds of the intestinal lining, and tiny, fingerlike villi: Increase the absorptive surface
0
1
• large intestine – wider diameter than the small intestine– no digestion takes place here– Main functions:
• fluid absorption from waste: water, Na, vitamin K• compact and store undigested material as feces in
the rectumLargeintestine(colon)
Sphincter
Endof smallintestine
Appendix
Cecum
Anus
Rectum
Smallintestine
Nutrientflow
The small intestine is the major organ of chemical digestion and nutrient absorption in which 2 major organs secrete their content:
0
Liver
Gall-bladder
Intestinal enzymes
Duodenum ofsmall intestine
Bile
Bile
Acid chyme
Pancreaticjuice
Stomach
Pancreas
• pancreas– Secretes bicarbonate
to neutralize the acid chyme
– And enzymes to digest food polymers
• trypsin, chymotrypsin digest proteins
• amylase digests starch• lipase digests fats
– Also produces hormones: insulin and glucagon to deal with glucose storage
Liver
Intestines
Kidneys
HepaticPor talvein
• liver – largest internal organ
– has a strategic location in the body: between the intestines and the hear
– Many functions:
• produces bile and stores it in the gallbladder for fat digestion
• removes toxins, pesticides, carcinogens and other poisons by converting them into less toxic forms
• produces urea
• Breaks down toxins
Alcohol consumption can damage the liver and liver function can be impaired, as well as hepatitis
EXCRETORY SYSTEM
Major parts:• Kidneys, 2 kidneys,
each of contains 1 mll nephrons
• ureter• urinary bladder• Urethra
Functions: major role in homeostasis>>> expels wastes and regulates water and ion balance
• Nephrons, the functional units of the kidneys>>> Extract a filtrate from the blood and refine it to urine>>>Urine leaves the kidneys via ureters>>>Is stored in the urinary bladder, and is expelled through the urethra
Aorta
Inferiorvena cavaRenal artery and vein
Ureter
Urinary bladderUrethra
A The excretory system
Kidney
Renal cortexRenal medulla
Renal pelvis
Ureter
B The kidney
Bowman’scapsule
C Orientation of a nephron within the kidney
Renal artery
Renal vein
Nephrontubule
Collectingduct
Torenalpelvis
Renal cortex
Renal medulla
Glomerulus 1 Proximal tubule
3 Distal tubule
Capillaries
Fromanothernephron
Collectingduct
Bowman’s capsule
Arteriolefrom renalartery
Arteriolefromglomerulus
Branch ofrenal vein
2 Loop of Henle with capillary network
D Detailed structure of a nephron
– Major processes of the excretory system
H2O, other small molecules Urine
ExcretionSecretionReabsorptionFiltration
CapillaryInterstitial fluid
Nephron tubule
The key processes of the excretory system are filtration, reabsorption, secretion, and excretion
• In filtration: Blood pressure forces water and many small solutes into the nephron
• In reabsorption: Valuable solutes are reclaimed from the filtrate
• In secretion: Excess H+ and toxins are added to the filtrate
• The product of all of the above processes is urine: Which is excreted
Kidney dialysis can be a lifesaver
– Compensating for kidney failure
– A dialysis machine removes wastes from the blood and maintains its solute concentration
Line from arteryto apparatus
Dialyzingsolution
Fresh dialyzingsolution
Used dialyzing solution(with urea and excess ions)
Tubing made of a selectively permeablemembrane
Pump
Line fromapparatusto vein