1. Digestion
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2. The Digestive System’s 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

3. 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

4. Figure 38–10 The Digestive System
Mouth
Salivary glands
Stomach
Pancreas (behind stomach)
Large intestine
Small intestine
Rectum
Gallbladder (behind liver)
Liver
Esophagus
Pharynx

5. 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

6. 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

7. 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)

8. 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

9. 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)

10. 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

11. Liver Produces bile = “detergent” dissolving fat droplets
Bile is stored in the gallbladder

12. Figure 38–13 The Liver and the Pancreas
Section 38-2
Liver
Gallbladder
Duodenum
Bile duct
Pancreas
Pancreatic duct
To small intestine

13. 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

14. Figure 38–14 The Small Intestine
Section 38-2
Small Intestine
Villus
Circular folds
Villi
Epithelial cells
Capillaries
Lacteal
Vein
Artery

15. The Digestive Enzymes KNOW 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.

16. 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

17. Excretion
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18. 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

19. 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

20. The Urinary System DRAW & LABEL THIS
Section 38-3
Vein
Artery
Kidney (Cross Section)
Kidney
Cortex
Medulla
Ureter
Urinary bladder
Urethra

21. 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

22. 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

23. Figure 38–17 Structure of the Kidneys
Section 38-3
Kidney
Nephron
Cortex
Medulla
Renal artery
Renal vein
Ureter
To the bladder
Bowman’s capsule
Glomerulus
Capillaries
Collecting duct
To the ureter
Loop of Henle
Artery
Vein
FILTRATION…REABSORBTION…SECRETION

24. 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

25. 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