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 6

Textbook Question

Large molecules such as peptides and proteins move into and out of the bloodstream by way of:
(a) Continuous capillaries
(b) Fenestrated capillaries
(c) Thoroughfare channels
(d) Venules

Verified step by step guidance

Step 1: Begin by understanding the structure and function of capillaries. Capillaries are the smallest blood vessels in the circulatory system, and they are responsible for the exchange of substances between the blood and surrounding tissues. There are three main types of capillaries: continuous, fenestrated, and sinusoidal.

Step 2: Examine the characteristics of continuous capillaries. These capillaries have a continuous endothelial lining with tight junctions between cells, allowing only small molecules like water and ions to pass through. Large molecules like peptides and proteins cannot pass through continuous capillaries.

Step 3: Investigate fenestrated capillaries. These capillaries have pores (fenestrations) in their endothelial lining, which allow for the movement of larger molecules such as peptides and proteins. Fenestrated capillaries are commonly found in areas of the body where rapid exchange of substances occurs, such as the kidneys and endocrine glands.

Step 4: Consider thoroughfare channels. These are direct pathways that connect arterioles to venules, bypassing capillary beds. They are not specialized for the exchange of large molecules like peptides and proteins.

Step 5: Evaluate venules. Venules are small veins that collect blood from capillaries and transport it to larger veins. While they play a role in blood transport, they are not specialized for the movement of large molecules into or out of the bloodstream.

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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 uninterrupted endothelial cells, fenestrated capillaries contain pores for increased permeability, and sinusoidal capillaries are larger and allow for the passage of larger molecules.

Molecular Transport

Molecular transport refers to the mechanisms by which substances, including large molecules like peptides and proteins, move across cell membranes and vascular barriers. This can occur through passive diffusion, facilitated diffusion, or active transport, depending on the size and nature of the molecules and the characteristics of the capillary type.

Bloodstream Dynamics

Bloodstream dynamics involve the flow and behavior of blood within the circulatory system. Understanding how blood flows through different types of vessels, including capillaries, is crucial for comprehending how nutrients, waste, and larger molecules are exchanged. Factors such as blood pressure, vessel diameter, and permeability influence these dynamics.

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