How can we help?

You can also find more resources in our Help Center.

67 terms

A&P CH21 Blood Vessels

What are the three classifications of arteries?
1) Elastic
2) Muscular
3) Arterioles
What is the most common blood vessel type?
What are the three classifications of veins?
1) Venules
2) Small Veins
3) Medium or Large Veins
Simple squamous internal lining of all blood vessels is called _____ ?
Endothelium (epithelium)
The endothelium of blood vessels are continuous with the _____ of the heart
Interior space of a vessel through which blood flows is called _____ ?
What are the three tunics that make up the wall of a blood vessel (from inner to outer)?
1) Tunica Intima
2) Tunica Media
3) Tunica Adventitia
What is the layer of elastic fibers on the tunica intima called?
Internal elastic membrane
What blood vessel layer consists primarily of smooth muscle cells?
Tunica Media
What is vasoconstriction?
Contraction of smooth muscle that decreases diameter of a vessel
What is vasolidation?
Relaxation of smooth muscle that increases diameter of a vessel
The network of small blood vessels that supply nutrients to wall of large blood vessels is called?
vasa vasorum
Neural innervation of blood vessels is responsible for what action(s)
Vasoconstriction (sympathetic) and vasodilatation (parasympathetic)
What layers are found in a capillary wall?
Endothelium (tunica intima) only
Diameter of a capillary
7-10 μm
What makes for the easy exchange of gases and molecules in capillaries?
Single-layered, permeable wall of endothelium and fenestrae (windows)
What are the three classifications of capillaries?
1) Continuous
2) Fenestrated
3) Sinusoidal
What are the characteristics and permeability of a continuous capillary?
No fenestrae, Low permeability.
Continuous capillaries are found in?
Muscle and nervous tissue
What are the characteristics and permeability of a fenestrated capillary?
Contain fenestrae, usually with diaphragm. Highly permeable
Fenestrated capillaries are found in
Most endocrine glands, kidney and small intestine
What are the characteristics and permeability of a sinusoidal capillary?
Larger in diameter. Contain large fenestrae with no diaphragm. Highly permeable to larger molecules
Sinusoidal capillaries are found in:
Bone marrow, liver, spleen, thyroid and anterior pituitary
What is sinusoid?
An incomplete base membrane with large holes in endothelium
What is the use of sinusoid in the liver and spleen?
Large holes allows for filtration of the blood
What is the use of sinusoid in the thyroid and anterior pituitary gland?
Large holes allows for movement of hormones to blood
What are the smooth muscle cells that regulate blood flow through the capillaries?
Precapillary sphincters
How do capillary beds control heat (thermoregulation)?
By opening or closing precapillary sphinters
Path of blood flow through a capillary bed (starting with arteriole)
Arteriole → Metarteriole → Thoroughfare channel → Precapillary sphincter → Arterial capillaries → Venous capillaries → Thoroughfare channel → Venule
What happens to path of blood when precapillary sphincters close?
Blood passes directly from arteriole to venule, through thoroughfare channel, by-passing the capillary network/tissues.
Direct connections between arterioles and venules which allow blood to bypass capillary beds
arteriovenous anastomoses
Describe the portal system.
Blood passes through two capillary networks before returning to the heart (i.e., hepatic portal system, for filtration of blood)
Which arteries are also known as conducting arteries?
Elastic arteries
What are the characteristics of elastic arteries (diameter, vessel wall)?
Largest in diameter (1 - 2.5 cm); walls contain less smooth muscle but more elastic fibers
ex. aorta, subclavian
Which arteries are also known as distributing arteries?
Muscular arteries
What are the characteristics of muscular arteries (diameter, vessel wall)?
Include medium and small arteries; walls are comprised of thicker smooth muscle layer and thick internal elastic membrane
How is an elastic artery different from a muscular artery?
Has larger amount of elastic tissue and less smooth muscle
What are the characteristics of arterioles (diameter, vessel wall)?
Smallest in diameter (9-40 μm); all three tunics observable but no internal elastic membrane
What is the function of arterioles?
To deliver oxygenated blood to the capillaries
What are the characteristics of venules and small veins (diameter, vessel wall)?
Diameter of 50 μm up to 0.3mm; vessel wall structure similar to capillaries
What is the function of venules?
Collect deoxygenated blood from the capillaries and transport it to the small veins; some nutrient exchange occurs in smallest venules
Which veins are also known as capacitance vessels and why?
medium veins; because they contain 65% of blood volume, as blood is held here while waiting to be transported back to the heart (via vasoconstriction)
Where are blood vessel valves found?
In veins of more than 2mm in diameter
Why are venous valves important?
To prevent back flow of blood
What happens when a vein's walls are stretched to the point that the valves fail?
Varicose veins can develop
Arterial walls are thicker/thinner than vein walls.
Vein walls are thicker/thinner than artery walls?
Arterial lumen is smaller/larger than vein lumen?
Why are arterial walls thicker than venous walls?
Arterial walls endure a higher pressure
What is the term for "hardening of the arteries"?
In arteriosclerosis, what happens to the: 1) tunica intima, and 2) tunica media and what does it lead to?
Tunica intima thickens and permeability is compromised; tunica media loses elasticity; leads to calcium buildup in vessel wall and increased resistance to blood flow
What is the condition in which fatty deposits called plaque build up on the inner walls of the arteries?
What are the 3 parts of the aorta
1) ascending aorta
2) aortic arch
3) descending aorta
What arteries branch off the ascending aorta?
the coronary arteries
What arteries branch off the aortic arch?
1) brachiocephalic artery
2) left common carotid artery
3) left subclavian artery
What are the 2 parts of the descending aorta?
1) thoracic aorta
2) abdominal aorta
What two arterial branches does the abdominal aorta give rise to?
1) left common iliac artery
2) right common iliac artery
What three main veins return blood to the heart?
Superior & inferior vena cava, and coronary sinus
Where do the coronary veins drain into?
Into the coronary sinus, in the right atrium
What tributaries drain directly into the superior vena cava?
1) Right brachiocephalic vein
2) Left brachiocephalic vein
3) Azygos vein
What tributaries drain directly into the right brachiocephalic vein?
1) Right internal jugular vein
2) Right subclavian vein
3) Right internal thoracic vein
What does the ductus arteriosus turn into after birth?
Ligamentum arteriosum
What does the foramen ovale become after birth?
Fossa ovalis
What vessel is used to take blood pressure readings?
The brachial artery
What vessel is a common site of blood draw?
The median cubital vein
Path of pulmonary blood circulation
Heart (right side) → Pulmonary trunk → Pulmonary arteries → (Lungs) → Pulmonary vein → Heart (left side)
Path of systemic blood circulation
Heart (left side) → Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → Vena cava → Heart (right side)