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 13

Textbook Question

Which of the following structures is the 'leakiest'?
a. Continuous capillary
b. Sinusoidal capillary
c. Precapillary sphincter
d. Fenestrated capillary

Verified step by step guidance

Understand the types of capillaries: Capillaries are small blood vessels that facilitate the exchange of substances between blood and tissues. There are three main types: continuous, fenestrated, and sinusoidal capillaries, each with varying permeability levels.

Define continuous capillaries: These capillaries have tightly joined endothelial cells with minimal gaps, making them the least permeable. They are found in areas like the brain (blood-brain barrier) and muscles.

Define fenestrated capillaries: These capillaries have small pores (fenestrations) in their endothelial cells, allowing for moderate permeability. They are commonly found in organs involved in filtration, such as the kidneys and intestines.

Define sinusoidal capillaries: These capillaries have large gaps between endothelial cells and an incomplete basement membrane, making them the 'leakiest' type. They are found in organs like the liver, spleen, and bone marrow, where extensive exchange of large molecules and cells occurs.

Clarify the role of precapillary sphincters: These are muscular structures that regulate blood flow into capillary beds but do not directly influence permeability. Therefore, they are not considered 'leaky' structures.

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Key Concepts

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

Capillary Types

Capillaries are small blood vessels that facilitate the exchange of substances between blood and tissues. There are three main types: continuous, fenestrated, and sinusoidal. Continuous capillaries have tight junctions and are least permeable, fenestrated capillaries have pores for increased permeability, and sinusoidal capillaries have larger openings, allowing for the passage of larger molecules and cells.

Permeability

Permeability refers to the ability of substances to pass through a barrier, such as the walls of capillaries. Different types of capillaries exhibit varying levels of permeability based on their structural characteristics. Understanding permeability is crucial for determining how easily fluids and solutes can move between the bloodstream and surrounding tissues.

Sinusoidal Capillaries

Sinusoidal capillaries are specialized blood vessels found in certain organs, such as the liver and spleen. They have a discontinuous endothelium, allowing for the free exchange of larger molecules and even cells between the blood and surrounding tissues. This makes them the 'leakiest' type of capillary, facilitating significant transport of substances.