Digestion

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Digestion

• Copy everything in red

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The Digestive Systems Function

• As food passes through the digestive system, it
  gets broken down distributing its nutrient value
  to the body
• The function of each organ of the digestive
  system is to help convert foods into simpler
  molecules that can be absorbed and used by the
  cells of the body

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The Digestive System Structures

• The digestive system includes
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Major accessory structures that add secretions to
  the digestive system include
• Salivary glands
• Pancreas
• Liver

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Figure 3810 The Digestive System
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Mouth Salivary Glands

• Teeth
• Protected by enamel
• Chewing begins the process of mechanical
  digestion physical breakdown of large pieces of
  food into smaller pieces (cutting, tearing,
  crushing)
• Saliva
• Secreted by salivary glands
• Moisten food making it easier to chew
• Begins the process of chemical digestion
  Amylase (digestive enzyme) chemically breakdown
  large starch molecules into smaller sugar
  molecules
• Lysozyme enzyme fights infection

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Pharynx

• Remember from the Respiratory System
• The pharynx (throat) is a tube in the back of the
  mouth that passes both air and food
• Epiglottis (flap of tissue) covers the trachea to
  ensure food continue to move along digestive tract

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Esophagus

• Food tube
• Bolus (chewed clump of food) moves along by
  contractions of smooth muscle surrounding the
  esophagus peristalsis
• Cardiac sphincter closes esophagus after food has
  passed into the stomach preventing stomach
  contents from moving back into the esophagus
  (heart burn occurs when stomach acid splashing
  into the esophagus)

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Stomach

• A large muscular sac made of smooth muscle that
  mechanically and chemically digests food
• Chemical digestion occurs as gastric glands in
  the stomach lining secrete mucus to protect the
  inner wall while pepsin and hydrochloric acid
  break down protein
• Ulcers a hole in the stomach wall caused by a
  bacterial infection that eats away at the lining
  of the stomach
• Mechanical digestions occurs as the stomach
  muscles contract to churn and mix stomach fluids
  producing a mixture chyme
• Pyloric valve opens allowing chyme to flow from
  the stomach into the small intestine

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Duodenum

• More chemical digestion of chyme occurs in the
  duodenum (the first part of the small intestines)
  
• Chyme mixes with enzymes and digestive fluids
  from the pancreas and the liver (accessory
  structures)

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Pancreas

• A gland that produces hormones that regulate
  blood sugar levels
• Produces enzymes that break down carbohydrates,
  proteins, lipids, and nucleic acids
• Produces sodium bicarbonates (a base) that
  neutralizes stomach acid

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Liver

• Produces bile detergent dissolving fat
  droplets
• Bile is stored in the gallbladder

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Figure 3813 The Liver and the Pancreas
Section 38-2
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Small Intestine

• Made of three parts duodenum, jejunum, and ileum
• Where chemical digestion is completed
• The folded surfaces are covered with villi
  small fingerlike projections that increase the
  surface area of the small intestines for greater
  absorption of nutrients
• The products of carbohydrate or protein digestion
  are absorbed into capillaries in the villi and
  microvilli
• Undigested fats are absorbed by lymph vessels
  lacteals

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Figure 3814 The Small Intestine
Section 38-2
Small Intestine
Villus
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The Digestive EnzymesKNOW THIS CHART
Section 38-2
Site Mouth Stomach Small intestine(from
pancreas) Small intestine
Enzyme
Role in Digestion
Salivary amylase Pepsin Amylase Trypsin Lipase
Maltase, sucrase, lactase Peptidase
Breaks down starches into disaccharides Breaks
down proteins into large peptides Continues the
breakdown of starch Continues the breakdown of
protein Breaks down fat Breaks down remaining
disaccharides into monosaccharides Breaks down
dipeptides into amino acids.
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Large Intestine

• Food entering large intestine is basically
  nutrient-free, mainly made of water, cellulose
  (fiber), and other indigestible substances
• Removes water left in the chyme by absorbing it
  across the large intestine wall
• If water removal is inefficient, diarrhea occurs
  and can be dangerous due to the loss of salts and
  water
• Intestinal bacteria help with digestion
• The appendix is believed to have formerly stored
  bacteria to assist with cellulose digestion
• Solid concentrated waste (feces) is excreted
  through the rectum

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Excretion

• Copy everything in red

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Excretion

• Excretion the process by which wastes are
  eliminated from the body
• The excretory system includes
• Lungs excrete gaseous carbon dioxide from
  cellular respiration
• Rectum excrete solid undigested remains from
  food
• Skin excretes excess water, salts, urea
• Kidneys and accessory organs

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The Urinary System

• The urinary system rids the blood of wastes
  produced by the metabolism of nutrients and
  controls blood volume by removing excess water
  produced by body cells.
• The urinary system includes
• Kidneys
• Urinary bladder
• Connecting tubules
• Ureter
• Urethra

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The Urinary SystemDRAW LABEL THIS
Section 38-3
Artery
Vein
Kidney (Cross Section)
Kidney
Cortex
Medulla
Ureter
Urinary bladder
Urethra
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Kidneys

• Most people have 2 kidneys located on either side
  of the spinal column on your lower back
• Ureters tubes that carry urine from each kidney
  to the urinary bladder
• Urinary bladder saclike organ that stores urine
  until it can be excreted
• The kidneys filter blood by removing urea, excess
  water and other wastes collected as urine and the
  clean filtered blood returns to circulation

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Kidney Structure

• Inner part renal medulla
• Outer part renal cortex
• Functional units of the kidney nephrons
• About 1 million nephrons in each kidney
• Each nephron has its own arteriole (small
  artery), venule (small vein), and network of
  capillaries to filter blood

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Figure 3817 Structure of the Kidneys
Section 38-3
Kidney
Nephron
FILTRATIONREABSORBTIONSECRETION
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Urine

• The material that remains urine containing
  urea, salts, water and other substances
• The loop of Henle conserves water and minimizes
  the volume of urine
• Urine is stored in the urinary bladder until it
  can be released from the body through a tube
  urethra

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Kidney Function

• The kidneys maintain homeostasis by
• Regulating the water content of the blood (blood
  volume)
• Maintaining blood pH
• Removing waste products from the blood