The Digestive System Chapter 23 OVERVIEW .
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Transcript of The Digestive System Chapter 23 OVERVIEW .
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The Digestive SystemChapter 23
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• Mechanical Digestion – breaks down food into smaller pieces
Digestion is the mechanical and chemical breakdown of food into forms that cells can absorb.
INTRODUCTION
• Chemical Digestion – decomposes food into smaller molecules
Add these terms to vocabulary list…
The digestive system consists of:• The alimentary canal – extends from mouth to anus
• Accessory glands –secrete chemicals into the alimentary canal.
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HUMAN DIGESTIVE
SYSTEM
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If stretched out, the alimentary canal is about 8 meters long. That’s 26 feet!
THE ALIMENTARY CANAL
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STRUCTURE OF THE WALLMucosa – mucous membrane• Epithelial tissues on a bed of connective tissue• This layer absorb nutrients, secrete chemicals, and
protect the underlying layers.Submucosa – Beneath the mucosa• Loose connective tissue• Blood vessels, nerves, and lymphatic vessels• This layer nourishes the surrounding tissues, and
carries away nutrients.Muscular – • Decrease and increase the diameter of the
A.C. to push food throughSerosa – serous membrane• Secretes serous fluid, which lubricates the A.C.
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MOVEMENTS OF THE ALIMENTARY CANALMuscles of the A.C. provide two basic
movements:
Segmentation – mixing movement• Smooth muscles contract
and relax, mixing foods with digestive juices
Peristalsis – propelling movement• Smooth muscles contract in a
wave-like motion pushing food through the alimentary canal
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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.
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• Secrete salivaSaliva moistens the food, and
begins the digestion of carbohydrates
SALIVARY GLANDS
Three pairs of major salivary glands, include:
• Parotid glands • Submandibular
• Sublingual
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SALIVA = water + mucus + amylase
Parotid glands • Secrete clear watery fluid• Rich in salivary amylase – begins the chemical digestion of
carbohydrates
Submandibular glands• Secretes a mixed saliva with both watery fluid
and mucus
Sublingual glands• Secrete primarily mucus
SALIVARY GLANDS
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THE PALATE AND UVULA• The palate forms the roof of the oral cavityHard Palate - bony roof of the mouth• Formed by the palatine bones and portions of the maxilla
Soft Palate - Muscular arch
Uvula – cone-shaped projection
During swallowing, muscles draw the soft palate and the uvula upward preventing food from entering the nasal cavity.
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Teeth are the hardest structures in the body
THE TEETH
•primary (deciduous) teeth numbering 20• Usually erupt through the
gums from age of 6 months to 2 years
•secondary (permanent) teeth numbering 32• Usually begin to erupt at 6
years• 3rd molars = wisdom teeth,
which may erupt between 17-25 years of age
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TYPES OF TEETHIncisors- blade shaped teeth that bite or cut off large pieces of food
Canines- cone shaped teeth that grasp and tear food
Adult – 8 Child – 8
Adult – 4Child – 4
Premolars – flattened surface for grinding food
Adult – 8 Child – 0
Molars – flattened surface for grinding food
Adult – 12 Child – 8
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THE TONGUE• Thick, muscular organ• Manipulate foods and aids in swallowing
Mucous Membrane
Frenulum
Root• Anchored to the hyoid bone.• Covered with lingual tonsils
Papillae – projections on the surface of the tongue.• Some provide friction, others house taste buds.
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PHARYNX• The back of the
throat.
• Deglutition (swallowing)
• 3 parts
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SWALLOWING
• Epiglottis • flap of cartilage• closes trachea (windpipe) when swallowing• food travels down esophagus
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ESOPHAGUS• Peristalsis • involuntary muscle
contractions to move food along
• Esophageal Hiatus – opening in the diaphragm, passage for esophagus
• Hiatal hernia – part of the stomach protrudes through the hiatus.
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STOMACH• 2 sphincters (valves)
• 3 layers of muscle
• Secretes gastric juices
(enzymes + HCl)
• Mechanically and chemically breaks down food
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STOMACH
• Fundus = top portion
• Pyloris = funnel-shaped lower portion
• Rugae – gastric folds line the stomach
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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.
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ACCESSORY ORGANS
•Pancreas•Gall Bladder•Liver
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PANCREAS
• An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine)
• Pancreatic juice digests all major nutrient types. • “ENZYME COCKTAIL” includes enzymes top break down all
compounds: proteins, lipids and carbohydrates• Alkaline (base) neutralizes acidic chyme coming from stomach.
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PANCREAS
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LIVER
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LIVER FUNCTIONS• The liver carries on many important metabolic activities, including:
• Glycogenesis: producing glycogen from glucose
• Glycolysis: breakdown of glycogen into glucose
• Gluconeogenesis: converts non-carbohydrates to glucose
• Oxidizes fatty acids
• Synthesizes phospholipids and cholesterol
• Forms urea
• Synthesizes plasma proteins
• Stores glycogen, iron, and vitamins A, D, and B12
• Phagocytosis of worn out RBCs and foreign substances
• Removes toxins such as alcohol and certain drugs from the blood
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LIVER • Function: produces bile
• BILE breaks up fats
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GALL BLADDER
• It stores bile between meals• It concentrates bile by reabsorbing water• The gall bladder itself does not produce bile
• Bile duct – • a long tube that carries BILE • Connects the liver, pancreas, and gall bladder to the
duodenum (small intestine)
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GALLSTONES
• GALLSTONES – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder• Can either be “passed” (OUCH!!) or surgically
removed
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SMALL INTESTINE• Function• chemical digestion• major organ of digestion &
absorption• absorption through lining• over 6 meters! • small intestine has huge
surface area = 300m2
(~size of tennis court) • Structure• 3 sections• duodenum = most
digestion• jejunum = absorption of
nutrients & water• ileum = absorption of
nutrients & water
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DUODENUM
• 1st section of small intestines• acid food from stomach • mixes with digestive juices from:
pancreas liver gall
bladder
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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
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Villi increase surface area. More surface area = More absorption
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APPENDIX
Vestigial organVestigial organ
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APPENDICITIS
• inflammation of the appendix due to infection• Common treatment is removal of the appendix
via surgery
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THE LARGE INTESTINE The large intestine is named because of its diameter
It has four parts:
1. Cecum – blind pouch• Ileocecal sphincter • The appendix projects from the cecum.
2. Colon (ascending, transverse, descending, sigmoid)
3. Rectum - straight
4. Anal canal• The anus – is guarded by two sphincter muscles• external anal sphincter – composed of skeletal muscle• internal anal sphincter – composed of smooth muscle
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LARGE INTESTINES (COLON)
• Function
• re-absorb water• use ~9 liters of water every
day in digestive juices• > 90% of water reabsorbed
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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.
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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
.
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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
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• a condition in which the large intestine is emptied with difficulty. • Too much water is
reabsorbed• Solid waste hardens
CONSTIPATION
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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
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RECTUM • Last section of colon
(large intestines)• eliminate feces
• undigested materials• extracellular
waste• mainly
cellulose from plants
• roughage or fiber
• masses of bacteria
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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
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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
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EPISIOTOMY
This…
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NOTEBOOKS
Due Monday, April 14
Must include:• RESPIRATORY SYSTEM• DIGESTIVE SYSTEM• URINARY SYSTEM
See website for DIGESTIVE SYSTEM powerpoint to help finish notes on chart.