blood vessels & blood components Flashcards
What is the structure of blood vessels?
contain a central lumen lined with endothelium, a single layer of flattened epithelial cells that minimizes resistance to blood flow.
How do capillaries differ from arteries and veins?
Capillaries: Thin, leaky walls consisting of an endothelium and basal lamina. only site of exchange between blood and interstitial fluid.
Arteries & Veins: smooth muscle and connective tissue.
Arteries have thicker walls due to high hydrostatic pressure.
Veins have a larger lumen and thinner walls
What are the functions of arteries, veins, and capillaries?
Arteries: Carry oxygen-rich blood away from the heart under high pressure.
Veins: Carry oxygen-poor blood toward the heart with lower pressure.
Capillaries: Exchange oxygen, nutrients, and waste between blood and tissues.
What happens to blood pressure during systole and diastole?
Systolic pressure: Highest when the heart contracts (ventricular systole).
Diastolic pressure: Lower when the ventricles relax (diastole).
How do vasoconstriction and vasodilation affect blood pressure?
Vasoconstriction: Narrowing of arterioles due to smooth muscle contraction, increasing blood pressure.
Vasodilation: Widening of arterioles, decreasing blood pressure.
What two opposing forces control capillary function?
Blood pressure (BP) – Pushes fluid out of capillaries.
Osmotic pressure – Pulls fluid back into capillaries due to blood proteins.
💡 BP is higher at the arteriole end than the venous end, leading to net fluid loss from capillaries.
What are the main components of blood?
Plasma (55% of blood volume)
Erythrocytes (Red Blood Cells) – Transport oxygen using hemoglobin.
Leukocytes (White Blood Cells) – Fight infections.
Platelets – Help in blood clotting.
How do red blood cells (erythrocytes) transport oxygen efficiently?
Biconcave shape increases surface area for O₂ exchange.
No nucleus or mitochondria, allowing more space for hemoglobin.
Hemoglobin binds O₂ using iron and has 4 subunits.
What is the function of white blood cells (leukocytes)?
Fight infections.
Some leukocytes are phagocytic
What is the function of platelets in blood clotting?
Platelets are cell fragments (no nucleus).
They initiate clotting by releasing fibrin, which holds clotting agents together.
