Chapter 20 - Cardiovascular System: Vessels & Circulation Flashcards
What are tunics?
Layers of blood vessel walls
What is the Lumen of a blood vessel?
Inside space of vessel through which blood flows (surrounded by tunics)
What is the tunica intima?
Innermost layer of blood vessel
- composed of endothelium
- thin subendothelial layer of areolar connective tissue
What is the tunica media?
Middle layer of blood vessel wall
- composed primarily of circularly arranged layers of smooth muscle cells supported by elastic fibers
What is the tunica externa (“tunica adventitia”)?
outermost layer of blood vessel wall
- composed of areolar connective tissue that has elastic and collagen fibers
- helps anchor vessel to other structures
What is the vasa vasorum?
a network of small arteries that supply blood to the tunica externa
What are companion vessels?
arteries and veins that supply the same body region and typically lie next to each other
Elastic arteries (“conducting arteries”)
- largest type
- conduct blood from the heart to smaller muscular arteries
- large amount of elastic fibers
Muscular arteries (“distributing arteries”)
- medium sized arteries
- distribute blood to specific regions and organs
- elastic fibers are confined to internal elastic lamina (btwn media & intima) and external elastic lamina (btwn media & externa)
What are arterioles?
- smallest arteries
Vasomotor tone
contracted state of blood vessels (regulated by medulla oblongata)
Sympathetic motor tone
- results in vasoconstriction
Capillaries
- smallest blood vessels
- connect arterioles to venules (smallest veins)
- consist solely of endothelium
What are continuous capillaries?
- most common type
- continuous endothelial lining around lumen that rests on complete basement membrane
- found in muscle, skin, thymus, lungs, brain, spinal cord
What are fenestrated capillaries?
- composed of continuous lining of endothelial and complete basement membrane
- small regions of endothelial cells are extremely thin to prevent formed elements from passing through
- found in small intestine, eye, choroid plexus of brain
What are sinusoids (“discontinuous capillaries”)?
- more permeable
- incomplete lining of endothelial cells with large gaps and either an absent of discontinuous basement membrane
- allows transport of large substances
- found in red bone marrow, spleen, some endocrine glands
What are capillary beds?
- group of capillaries
- blood delivered by a metarteriole
- thoroughfare channels of metarteriole connects to postcapillary venule
What are true capillaries?
- branch from metarteriole and make up most of capillary bed
What is the precapillary sphincter?
controls blood flow into true capillaries
What are venules?
- smallest veins
- companion vessels to arterioles
What is a simple pathway?
one major artery delivers blood to a region or organ and then branches into smaller arteries to become arterioles.
What are alternative pathways>
- anastomosis (joining of two blood vessels to supply blood to same region)
- arterial: 2+ arteries supply
- venous: 2+ veins drain
- arteriovenous (“shunt”): transports blood from an artery directly into a vein (bypasses capillary bed)
What is a portal system?
blood flows through 2 capillary beds, separated by a portal vein (delivers blood to another organ first before being sent back to heart)
What is blood flow velocity?
Rate of blood transported per unit time (usually measured in cm/sec)
What is vesicular transport?
endothelial cells use pinocytosis to form fluid-filled vesicles which transport to other side of cell and released by exocytosis
What is bulk flow?
movement of large amounts of fluids/dissolved substances in a direction down pressure gradient
What is hydrostatic pressure (HP)?
physical force exerted by fluid on a structure
What is colloid osmotic pressure?
pull of water back into a tissue by the tissue’s concentration of proteins (colloids)
What is net filtration pressure (NFP)?
difference between the net hydrostatic pressure and the net colloid osmotic pressure
What is local blood flow?
blood delivered locally to capillaries of a specific tissue and is measured in mL/min
What is perfusion?
amount of blood entering capillaries per unit time per gram of tissue
Degree of vascularization
extent of blood vessel distribution within a tissue
- determines potential ability of blood delivery
- active organs like brain and heart are generally highly vascularized
Angiogenesis
formation of new blood vessels in tissues that require them
- amount of vascularization in given tissue may change over time via this process
Myogenic response
contraction and relaxation of smooth muscle within blood vessels in response to changes in stretch of vessel
What are vasodilators?
substances that cause smooth muscle relaxation which opens arterioles and precapillary sphincters
What are vasoconstrictors?
substances that cause smooth muscle contraction which close arterioles and precapillary sphincters
What is autoregulation?
process in which tissue regulates or controls its local blood flow in response to changes in metabolic needs
- typically initiated due to inadequate perfusion due to increased tissue metabolic activity
What is total blood flow?
amount of blood transported throughout the entire vasculature in a given period of time (usually L/min)
- equals cardiac output
What is blood pressure>
the force per unit area that blood exerts against the inside wall of vessels
What is a blood pressure gradient?
the change in blood pressure from one end of the vessel to the other
- highest in the arteries as the heart contracts and lowest in the veins
- propels blood through the vessels
Pulse pressure
additional pressure placed on arteries from when the heart is resting (diastolic pressure) to when the heart is contracting (systolic pressure)
- measure of eleasticity and recoil of arteries
Mean arterial pressure (MAP)
measure of blood pressure on arteries
Capillary blood pressure
- pulse pressure disappears by time it reaches arteries
- must be sufficient for exchange of substances
Venous blood pressure
movement of blood from capillaries back to the heart via veins: venous return
- veins also have no pulse pressure
What is a skeletal muscle pump?
assist movement of blood primarily in limbs
- blood propelled via muscles contracting around veins
Respiratory pump
assists movement of blood in thoracic cavity
- diaphragm contracts and flattens, pressure on vessels
What is resistance?
amount of friction the blood experiences as it is transported through blood vessels
