Passive Transport in the Body

1. Passive Transport in the Body Includes material from chapters 30 and 32

2. In the Digestive System… • Most nutrient absorption occurs within the small intestine • Specifically, most nutrients are absorbed within the jejunum • Chemical digestion wraps up in the duodenum

3. In the Digestive System… • The small intestine is lined with villi (which have microvilli) – this increases the surface area to maximize nutrient absorption

4. In the Digestive System… • Water-soluble substances, including vitamin C, are absorbed along with water • By osmosis, these substances move from the intestines to the bloodstream • Small lipids also diffuse into blood

5. In the Digestive System… • Some substances, including the sugar fructose, need transport proteins to get across the cell membrane • These substances still travel down the concentration gradient – so the process is facilitated diffusion

6. In the Digestive System… • Some disorders of the digestive system can interfere with nutrient absorption. • Hemochromatosis is a condition, typically hereditary, that leads to increased iron absorption

7. In the Digestive System… • Whipple’s disease is a rare condition caused by a bacterial infection that prevents the small intestine from properly absorbing nutrients – it causes irregular fold patterns in the small intestine and thickened walls

8. In the Circulatory System… • Once nutrients have been absorbed by the intestines, the next step is to get these nutrients to the cells • Cells need nutrients for cellular respiration, growth, repair, and other activities

9. In the Circulatory System… • Nutrients are dissolved in the plasma (liquid portion) of the blood • Plasma is mostly water, but also contains blood proteins • In addition to transporting nutrients, plasma also carries hormones and electrolytes • The other components of blood are cellular: red blood cells, white blood cells, and platelets

10. In the Circulatory System… • Most nutrients are sent to the liver first for processing and storage of excess nutrients • The hepatic artery takes blood to the liver • The hepatic vein returns blood from the liver to the heart

11. In the Circulatory System… • The heart is responsible for pumping blood throughout the body • The pumping chambers of the heart are the ventricles

12. In the Circulatory System… • Blood leaving the heart to go to the body – not the lungs! – is pumped out the left ventricle and into the aorta

13. In the Circulatory System… • The blood vessels carry the blood – and the nutrients it holds – throughout the body

14. In the Circulatory System… • There are three major types of blood vessels: • Arteries carry blood away from the heart; the largest artery is the aorta; small arteries are called arterioles • Veins carry blood toward the heart; the largest artery is the vena cava; small veins are called venules Capillaries link arteries to veins; these blood vessels are so narrow that blood cells have to pass through them single file

15. In the Circulatory System… • At the capillaries, nutrients diffuse from bloodstream to body cells – and wastes diffuse from the body cells into the bloodstream

16. In the Circulatory System… • Many wastes will eventually be carried through the renal artery to the kidney, which will purify the blood • Some of these wastes diffuse into the kidney; others are pulled from the bloodstream by active transport

17. In Gas Exchange… • In addition to nutrients and wastes from food, the blood also transports oxygen and carbon dioxide • Red blood cells carry oxygen on hemoglobin

18. In Gas Exchange… • Oxygen enters the body through the respiratory system • Air travels from the nose  pharynx  trachea  bronchi  bronchioles  alveoli

19. In Gas Exchange… • Each alveolus is an air sac surrounded by a network of capillaries • The pulmonary arteriole brings blood from the heart while the pulmonary venule carries blood back to the heart

20. In Gas Exchange… • Oxygen diffuses from the alveolus into the capillary; it will then travel back to the heart to be pumped out to the body • Carbon dioxide and water diffuse from the capillary into the alveolus; it will then be exhaled

21. In Gas Exchange… • Certain conditions can impair gas exchange • In pneumonia, an infection causes an inflammation of the lungs; the lungs often become filled with fluid

22. In Gas Exchange… • In asthma, the airways of the lungs swell and narrow

23. In Gas Exchange… • In emphysema, the alveoli (air sacs) are damaged -- their walls break down and the sacs become larger. • These larger air sacs move less oxygen into the blood. • This causes difficulty breathing or shortness of breath that gets worse over time.

24. In Gas Exchange… • In anemia, a person has fewer red blood cells • Remember, red blood cells are responsible for transporting oxygen to the body cells • There are multiple types and causes of anemia