Chapter 20 - Section 20.1 - General Anatomy of the Blood Vessels - Before You Go On - Page 752: 3

Continuous Capillary: - **Structure:** Continuous capillaries have a continuous endothelial lining without gaps. The endothelial cells are tightly connected by tight junctions, forming a continuous and uninterrupted barrier. - **Permeability:** They have limited permeability to large molecules and cells due to the tight junctions between endothelial cells. - **Function:** Continuous capillaries are found in tissues where there is a need for controlled substance exchange. They are common in muscle, nervous tissue, and connective tissue. - **Examples:** Skin, skeletal muscle, brain. Fenestrated Capillary: - **Structure:** Fenestrated capillaries have pores (fenestrations) in their endothelial cells. These pores allow for increased permeability to small molecules and fluids. - **Permeability:** They are more permeable than continuous capillaries due to the presence of fenestrations, but they still have some level of selectivity. - **Function:** Fenestrated capillaries are found in organs with rapid filtration or absorption processes, such as the kidneys, small intestine, and endocrine glands. - **Examples:** Kidneys, endocrine glands, small intestine. Sinusoid (Discontinuous Capillary): - **Structure:** Sinusoids are the most permeable type of capillaries. They have large gaps between their endothelial cells, often lacking tight junctions and a complete basement membrane. This creates large intercellular spaces. - **Permeability:** Sinusoids are highly permeable, allowing the passage of large molecules, cells, and even blood cells. - **Function:** Sinusoids are found in organs where there is a need for extensive exchange between blood and tissue, such as the liver, bone marrow, and spleen. - **Examples:** Liver, bone marrow, spleen. In summary, the differences between these types of capillaries primarily lie in their structural characteristics and permeability. Continuous capillaries have a continuous endothelial lining and limited permeability, fenestrated capillaries have pores for increased permeability to small molecules, and sinusoids have large gaps and high permeability, allowing the passage of larger molecules and cells. These differences reflect the diverse roles these capillary types play in various tissues and organs within the body.

Continuous Capillary: - **Structure:** Continuous capillaries have a continuous endothelial lining without gaps. The endothelial cells are tightly connected by tight junctions, forming a continuous and uninterrupted barrier. - **Permeability:** They have limited permeability to large molecules and cells due to the tight junctions between endothelial cells. - **Function:** Continuous capillaries are found in tissues where there is a need for controlled substance exchange. They are common in muscle, nervous tissue, and connective tissue. - **Examples:** Skin, skeletal muscle, brain. Fenestrated Capillary: - **Structure:** Fenestrated capillaries have pores (fenestrations) in their endothelial cells. These pores allow for increased permeability to small molecules and fluids. - **Permeability:** They are more permeable than continuous capillaries due to the presence of fenestrations, but they still have some level of selectivity. - **Function:** Fenestrated capillaries are found in organs with rapid filtration or absorption processes, such as the kidneys, small intestine, and endocrine glands. - **Examples:** Kidneys, endocrine glands, small intestine. Sinusoid (Discontinuous Capillary): - **Structure:** Sinusoids are the most permeable type of capillaries. They have large gaps between their endothelial cells, often lacking tight junctions and a complete basement membrane. This creates large intercellular spaces. - **Permeability:** Sinusoids are highly permeable, allowing the passage of large molecules, cells, and even blood cells. - **Function:** Sinusoids are found in organs where there is a need for extensive exchange between blood and tissue, such as the liver, bone marrow, and spleen. - **Examples:** Liver, bone marrow, spleen. In summary, the differences between these types of capillaries primarily lie in their structural characteristics and permeability. Continuous capillaries have a continuous endothelial lining and limited permeability, fenestrated capillaries have pores for increased permeability to small molecules, and sinusoids have large gaps and high permeability, allowing the passage of larger molecules and cells. These differences reflect the diverse roles these capillary types play in various tissues and organs within the body.