Transcript Digestion and Excretion ppt

Digestive System
The Digestive System
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Digestion: mechanical and chemical
breakdown of food and absorption of
nutrients
Anatomy of the digestive system:
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Alimentary canal: 8 meter long muscular tube
from mouth to anus (mouth, throat,
esophagus, stomach, intestines)
Accessory organs that aid in digestion
(pancreas, liver, gallbladder, salivary glands)
Mouth
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Tongue: skeletal muscle, mixes food with
saliva, aids in swallowing, has taste buds
Teeth: 32 in adult, breaks food into
smaller pieces
Salivary glands: secrete saliva to moisten
food and start chemical process of
digestion; contains amylase- enzyme that
breaks down carbohydrates
Pharynx and Esophagus
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Muscular tubes that propel food to
stomach but do not digest food
Esophagus- 25 cm long, has esophageal
sphincter at entrance to stomach to
prevent food from coming back up
Stomach
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Receives food from esophagus, mixes with
gastric juice, begins protein digestion
Gastric juice: mix of hydrochloric acid,
pepsin (digests protein), mucus
Mucus lining prevents stomach from
digesting itself (acid eating through
stomach wall)
Chyme- product of food mixing with
gastric juice, sent to small intestine
Small Intestine
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Receives secretions from pancreas and
liver, digests chyme from stomach,
absorbs nutrients, transports residue to
large intestine
Intestinal villi- fingerlike projections that
line wall of small intestine, increase
surface area for absorption
Intestinal enzymes:
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Peptidase- protein digestion
Sucrase, maltase, lactase- sugar digestion
Intestinal lipase- fat digestion
Pancreas
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Secretes mix of digestive enzymespancreatic juice
Enzymes in pancreatic juice:
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Pancreatic amylase- breaks carbohydrates into
sugars
Pancreatic lipase- digests fat
Trypsin, chymotrypsin, carboxypeptidaseprotein-splitting enzymes
Liver
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High rate of fatty acid metabolism
Formation of glucose
Very important role in protein metabolism
Removes toxins, filters blood for damaged
RBCs and foreign substances
Secretes bile- helps digest lipids
Excess bile stored in the gallbladder
Large Intestine
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Absorbs water and electrolytes, forms and
stores feces
Appendix- small projection with no
function
Intestinal bacteria break down cellulose
(plant carbohydrates) and synthesize
some vitamins
Rectum- temporary storage for feces at
end of large intestine
Anus- opening at end of large intestine
Vitamins and Minerals
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Vitamins: organic compounds needed in
small amounts for metabolism
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Fat Soluble Vitamins: stored in fat, so overdose
is possible; Vitamins A, D, E, K
Water Soluble Vitamins: dissolve in water, so any
extra is excreted, not stored; B Vitamins,
Vitamin C
Minerals: small amounts of elements needed
in metabolism; Calcium, Phosphorus,
Potassium, Sodium, Magnesium
Digestive System Review
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Besides fat and protein digestion, what
other important function does the liver
perform?
In what digestive organ do most of the
nutrients get fully digested and
absorbed?
What organs play no role in digestion but
are merely used for transport?
Urinary System
The Urinary System
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Functions:
Remove salt and nitrogenous waste
from blood
 Maintain water/electrolyte balance in
body
 Regulates volume of body fluids
 Help control RBC production
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Organs of Urinary System
4 main organs in urinary system:
1. Kidney- filters waste out of blood and
controls how much water is excreted
2. Ureters- transport waste from kidneys to
bladder
3. Bladder- stores waste (urine)
4. Urethra- transports urine from bladder to
outside
The Kidney
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Nephron: site of
blood filtration in
kidney, about 1
million contained in
kidney
Urine Formation
3 Steps:
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Glomerular Filtration: Water, ions, and other
plasma substances are filtered out of blood
and into glomerular capsule
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Tubular Reabsorption: certain substances from
filtrate are reabsorbed (glucose, amino acids,
water, some ions)
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Tubular Secretion: Waste substances missed in
glomerular filtration are removed from blood
(ammonia, hydrogen ions, potassium ions,
penicillin, histamine)
Urine Composition
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Volume of urine related to fluid intake
(drinking more fluids produces more
urine), between 0.6 and 2.5 L per day
About 95% water, with urea, uric acid,
some amino acids and salts
Urea and uric acid: by-products of
metabolism of amino and nucleic acids
Urine Elimination
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Travel from kidney to bladder through
ureters
Bladder holds ~600 mL urine, urge to
urinate comes from bladder contractions
which start around 150 mL full
Sphincter at bladder opening keep bladder
closed, urination occurs when muscles
relax and sphincter open