Transcript 0 - El Camino College

DIGESTION
• Food: source of energy
and essential molecules
• optimal diet: more
carbohydrates than fats
and significant of protein
• 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
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Obesity is a human health problem:
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– 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
•
•
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
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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
Teeth
Incisors
Canine
Premolars
Molars
Tongue
Salivary
glands
Opening of a
salivary gland duct
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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
Tongue
Bolus of food
Pharynx
Epiglottis
up
Esophageal
sphincter
Larynx
Trachea (windpipe)
Sphincter contracted
Epiglottis
down
Epiglottis
up
Larynx
up
Esophagus
Esophagus
Sphincter relaxed
Larynx
down
Sphincter contracted
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The esophagus squeezes food
along to the stomach by
peristalsis
Bolus of
food
food from the esophagus into
the stomach is controlled by
a ring of muscle, sphincter
Muscles contract
Muscles
contract,
constricting
passageway
and pushing
bolus down
Muscles relax
Muscles relax,
allowing
passageway
to open
Muscles contract
Muscles
relax
- when relaxed>>> stomach
contents can be brought
back out during vomiting and
lead to acid reflux or
heartburn
Stomach
The Heimlich maneuver can save lives: dislodge0
food from the pharynx or trachea during
choking
• 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
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Bacterial infections, Helicobacter pylori, in the
stomach and duodenum are associated with
ulcers
• 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, fingerlike0
villi: Increase the absorptive surface
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• 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 rectum
Large
intestine
(colon)
Small
intestine
Sphincter
End
of small
intestine
Rectum
Anus
Nutrient
flow
Appendix
Cecum
The small intestine is the major organ of chemical 0
digestion and nutrient absorption in which 2 major
organs secrete their content:
Liver
Bile
Gallbladder
Stomach
Bile
Acid chyme
Pancreas
Intestinal enzymes
Duodenum of
small intestine
Pancreatic
juice
• 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
– 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
Kidneys
Liver
Intestines
Hepatic
Por tal
vein
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
Renal cortex
Renal medulla
Aorta
Inferior
vena cava
Renal artery and vein
Renal pelvis
Kidney
Ureter
Ureter
Urinary bladder
Urethra
A The excretory system
Bowman’s capsule
Arteriole
from renal
artery
B The kidney
Glomerulus 1 Proximal tubule
Capillaries
Bowman’s
capsule
Arteriole
from
glomerulus
Branch of
renal vein
2 Loop of Henle
with capillary
network
3 Distal
Renal artery
tubule
From
another Renal vein
nephron
Nephron
tubule
Collecting
duct
Collecting
duct
D Detailed structure of a nephron
Renal cor
Renal me
To
renal
pelvis
C Orientation of a nephron within the kidney
– Major processes of the excretory system
Filtration
Reabsorption
Secretion
Excretion
Nephron tubule
H2O, other small molecules
Capillary
Urine
Interstitial fluid
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 artery
to apparatus
Pump
Line from
apparatus
to vein
Tubing made of a
selectively permeable
membrane
Dialyzing
solution
Fresh dialyzing
solution
Used dialyzing solution
(with urea and excess ions)