Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

19. The Blood Vessels

Capillaries

Anatomy & Physiology

19. The Blood Vessels

Capillaries

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Problem 12

Textbook Question

List three ways in which substances can cross the capillary wall.

Verified step by step guidance

Understand that capillary walls are composed of a single layer of endothelial cells, which allow for the exchange of substances between blood and surrounding tissues.

Learn about diffusion, which is the movement of substances from an area of higher concentration to an area of lower concentration. Small, nonpolar molecules like oxygen (O₂) and carbon dioxide (CO₂) can cross the capillary wall via simple diffusion.

Explore filtration, which occurs due to hydrostatic pressure. This process pushes water and small solutes through gaps or fenestrations in the capillary wall, typically at the arterial end of the capillary.

Examine vesicular transport, which involves endocytosis and exocytosis. Larger molecules, such as proteins, can cross the capillary wall by being enclosed in vesicles and transported across the endothelial cells.

Recognize the role of active transport for substances that require energy to move against their concentration gradient. This mechanism is less common in capillaries but can occur for specific molecules like ions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Diffusion

Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In the context of capillary walls, small, non-polar molecules, such as oxygen and carbon dioxide, can easily diffuse through the lipid bilayer of endothelial cells, allowing for gas exchange between blood and surrounding tissues.

Filtration

Filtration is the movement of water and solutes through a membrane due to hydrostatic pressure. In capillaries, this process occurs primarily at the arterial end, where blood pressure forces fluid and small solutes out of the capillaries into the interstitial space, facilitating nutrient delivery and waste removal.

Transcytosis

Transcytosis is a cellular process that involves the transport of molecules across the interior of a cell via vesicles. In capillaries, larger molecules, such as proteins, can be engulfed by endothelial cells on one side and released on the other side, allowing for selective transport across the capillary wall.

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