blood vessels

Q: What are arteries

A: Vessels that carry blood away from the heart; thick walls, high pressure

Q: What are veins

A: Vessels that carry blood toward the heart; have valves to prevent backflow

Q: What are capillaries

A: Thin, one-cell-thick vessels where gas and nutrient exchange occurs

Q: What is the lumen of a blood vessel

A: The hollow central space through which blood flows

Q: What are metarterioles

A: Short vessels connecting arterioles to capillaries

Q: What do precapillary sphincters do

A: Regulate blood flow into capillaries

Q: What is autoregulation in blood flow

A: Local control of blood flow based on tissue needs (oxygen demand)

Q: What is blood pressure

A: The force exerted by blood on vessel walls

Q: What is systolic pressure

A: Pressure during heart contraction

Q: What is diastolic pressure

A: Pressure during heart relaxation

Q: What is pulse pressure and how is it calculated

A: Systolic – Diastolic; measures artery elasticity

Q: What is mean arterial pressure (MAP)

A: Diastolic + 1/3 Pulse Pressure; average arterial pressure

Q: What is the skeletal muscle pump

A: Muscle contractions push venous blood toward the heart

Q: What is the respiratory pump

A: Breathing movements that help draw blood toward the heart

Q: What is resistance in blood flow

A: Opposition to flow; influenced by vessel length, viscosity, and radius

Q: Why are capillaries exchange vessels, not arteries/veins

A: Capillaries are thin and permeable; arteries/veins are too thick

Q: Why do veins need valves

A: To prevent backflow due to low pressure in veins

Q: What is bulk flow in capillaries

A: Fluid movement driven by hydrostatic & osmotic pressures

Q: What is filtration in capillaries

A: Movement of fluid out of capillaries due to hydrostatic pressure

Q: What is reabsorption in capillaries

A: Fluid reentry due to higher colloid osmotic pressure in blood

Q: What helps venous return

A: Valves, skeletal muscle pump, and respiratory pump

Q: What are the three layers of blood vessels

A: Tunica intima (inner), tunica media (muscle), tunica externa (outer)

Q: Which vessel has a thicker tunica media

A: Arteries

Q: What are elastic arteries

A: Largest arteries; stretch & recoil (aorta)

Q: What are muscular arteries

A: Medium arteries that distribute blood (femoral artery)

Q: What are arterioles

A: Smallest arteries; control flow into capillaries

Q: What are the types of capillaries

A: Continuous, fenestrated, and sinusoidal

Q: Where are continuous capillaries found

A: Skin, muscles, CNS (least permeable)

Q: Where are fenestrated capillaries found

A: Kidneys, intestines (moderate permeability)

Q: Where are sinusoidal capillaries found

A: Liver, spleen, bone marrow (most permeable)

Q: What are venules

A: Small veins that collect blood from capillaries

Q: What are the largest veins

A: Vena cavae, subclavian, jugular

Q: What is the basic order of blood flow

A: Heart → arteries → arterioles → capillaries → venules → veins → heart

Q: What is a portal system

A: Blood flows through two capillary beds before returning to the heart

Q: What are anastomoses

A: Multiple vessels supplying the same area (circle of willis)

Q: What are the methods of capillary exchange

A: Diffusion, vesicular transport, bulk flow

Q: What does the lymphatic system do in blood flow

A: Returns excess fluid to the bloodstream

Q: How is local blood flow controlled

A: By local signals like low oxygen or high CO₂ (autoregulation)

Q: What affects resistance the most

A: Vessel radius (small change = big impact)

Q: How does the nervous system regulate BP

A: Through baroreceptors & brainstem centers; adjusts HR & vessel diameter

Q: What do baroreceptors detect

A: Changes in blood pressure

Q: Which hormones raise BP

A: Epinephrine, ADH, aldosterone

Q: Which hormone lowers BP

A: ANP (Atrial Natriuretic Peptide)

Q: How does the hepatic portal system work

A: Blood from digestive organs → liver → filtered → systemic circulation

Q: How do you calculate MAP

A: MAP = Diastolic + ⅓(Systolic – Diastolic)