The Digestive System Chapter 48 Digestion is the mechanical and chemical breakdown of food into...
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Transcript of The Digestive System Chapter 48 Digestion is the mechanical and chemical breakdown of food into...
The Digestive SystemChapter 48
Digestion is the mechanical and chemical breakdown of food into forms that cells can absorb.
The FUNCTIONs of the Digestive System include1. Breakdown food 2. Convert it into a usable form3. Form and expel solid wastes
INTRODUCTION
HUMAN DIGESTIVE
SYSTEM
If stretched out, the alimentary canal is about 8 meters long. That’s 26 feet!
THE ALIMENTARY CANAL
OVERVIEW• https://www.youtube.com/watch?v=nM5kMSjBrmw
THE MOUTH (ORAL CAVITY)• The mouth:
• Receives food• Mechanically breaks up solid particles using TEETH &
TONGUE• Chemically digest food using saliva.
• This action is called mastication
• Makes a BOLUS (wet ball of food)
• The mouth also functions as an organ of speech, and sensory reception.
TEETH & TONGUE
TEETHIncisors- bite or cut offCanines- grasp and tearPremolars – grinding foodMolars – grinding food
TONGUE• Position food between
teeth• Push food back to pharynx
• Secrete salivaSaliva moistens the food, and
begins the digestion of carbohydrates
SALIVARY GLANDS
Three pairs of major salivary glands.
THE PALATE AND UVULA
During swallowing, muscles draw the soft palate and the uvula upward preventing food from entering the nasal cavity.
PHARYNX• The back of the
throat.
• Deglutition (swallowing)
SWALLOWING
• Epiglottis • flap of cartilage• closes trachea (windpipe) when swallowing• food travels down esophagus
ESOPHAGUS
• Moves food down to stomach by PERISTALSIS • involuntary
muscle contractions to move food along
STOMACH• 2 sphincters (valves)
• 3 layers of muscle
• Secretes gastric juices
(enzymes + HCl)
• Mechanically and chemically breaks down food
GASTRIC JUICE• Acidic (pH 1.5-2.5)
(HCl)
• Pepsin- an enzyme that breaks down large proteins into amino acids.
• HCl activates pepsin
• BOLUS + GASTRIC JUICE = chyme.
• Heartburn
• Acid Reflux
ACCESSORY ORGANS
ACCESSORY ORGANS
•Pancreas•Gall Bladder•Liver
PANCREAS
Secretes PANCREATIC JUICE which contains enzymes to digest all major nutrient types.
• Alkaline (base) neutralizes acidic chyme coming from stomach.
LIVER
LIVER • Function: produces bile
• BILE breaks up fats
GALL BLADDER
• It stores bile between meals
• Bile duct – • Connects the liver, pancreas, and gall bladder to the
duodenum (small intestine)
GALLSTONES
• GALLSTONES – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder• Can either be “passed” (OUCH!!) or surgically
removed
SMALL INTESTINE• Function• Digestion & absorption• over 6 meters! • small intestine has huge
surface area ~size of tennis court
• Structure• 3 sections• duodenum = most
digestion• jejunum = absorption of
nutrients & water• ileum = absorption of
nutrients & water
ABSORPTION IN THE SI
• Much absorption is thought to occur directly through the wall without the need for special adaptations
• Almost 90% of our daily fluid intake is absorbed in the small intestine.
• Villi - increase the surface area of the small intestines, thus providing better absorption of materials
Villi increase surface area. More surface area = More absorption
LARGE INTESTINES (COLON)
• Function
• re-absorb water• use ~9 liters of water every
day in digestive juices• > 90% of water reabsorbed
LARGE INTESTINE• Solid materials pass
through the large intestine.• These are undigestible
solids (fibers).• Water is absorbed.• Vitamins K and B are
reabsorbed with the water.• Rectum- solid wastes exit the
body.
BACTERIAL FLORA
• Living in the large intestine is a community of helpful bacteria
• Escherichia coli (E. coli)• produce vitamins • vitamin K; B vitamins
• generate gases• by-product of bacterial
metabolism • methane, hydrogen
sulfide
FECES
• Poop, excrement, solid waste, etc…
• Feces is composed of materials not digested or absorbed, and include: Water, Electrolytes, Mucus, Bacteria, and Bile pigments
• Approximately 1/3 of the dry weight of feces is bacteria.
• The color of feces is provided by bile pigments altered by bacteria
.
DIARRHEA• a gastrointestinal
disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine.
• This results in increased, multiple, watery feces.
• This condition may result in severe dehydration, especially in infants
• a condition in which the large intestine is emptied with difficulty
• Too much water is reabsorbed
• Solid waste hardens
CONSTIPATION
RECTUM • Last section of colon
(large intestines)• eliminate feces
• undigested materials• extracellular
waste• mainly
cellulose from plants
• roughage or fiber
• masses of bacteria
ANAL CANAL / ANUS… LAST STOP
• Exit or opening for solid wastes• Regulated by anal
sphincter (valve)• Anal sphincter surrounded
by muscles• Elimination aided by
abdominal muscles
HEMORRHOIDS
Symptoms• Anal itching • Anal ache or pain, especially while
sitting • Bright red blood on toilet tissue, stool, or in the toilet bowl
•Very common, especially during pregnancy and after childbirth. •Result from increased pressure in the veins of the anus. The pressure causes the veins to bulge and expand, making them painful, particularly when you are sitting..
Pain during bowel movements One or more hard tender lumps near the anus