Blood Vessels Flashcards
The tunica media is a continuation of what layer of the heart?
Myocardium
The tunica adventitia is a continuation of what layer of the heart?
Epicardium (visceral pericardium)
What are three categories of arteries?
Elastic, muscular, and arterioles
What is another name for elastic arteries?
Conducting arteries
What is the tunica intima structure of elastic arteries?
Attenuated endothelium
Thin/incomplete internal elastic lamina
Thicker connective tissue with elastic fibers, collagen type I, fibroblasts, and smooth muscle
What is the tunica media structure of elastic arteries?
Fenestrated sheets of elastic fibers with some collagen type I and smooth muscle
Thin external elastic lamina is possible
Outer portion typically contains vasa vasorum
What is vasa vasorum?
Small blood vessels supplying the large blood vessel
What is the tunica adventitia structure of elastic arteries?
Loose fibroelastic connective tissue
Numerous vasa vasorum
What is the thickest/most dominant layer of an elastic artery?
Tunica media
What is another term for muscular arteries?
Distributing arteries
What is the tunica intima structure in muscular arteries?
Endothelium
Very thin
Some connective tissue (few smooth muscle cells possible)
Internal elastic lamina
What type of artery has a uniquely thin tunica intima?
Muscular arteries
What is the tunica media structure of muscular arteries?
Circular smooth muscle
Gap junctions between smooth muscle cells
Elastic and reticular fibers, chondroitin sulfate
External elastic lamina possible
Richly innervated with sympathetics (strong contraction over a small area)
What is the thickest and most dominant layer of the muscular artery?
Tunica media
What is the tunica adventitia structure of muscular arteries?
Fibroelastic connective tissue with sulfated GAGs
Fibroblasts
Vasa vasorum present
What is the tunica media of muscular arteries primarily made of?
Smooth muscle
What are the smallest arteries?
Arterioles
Overall, arterioles are very structurally similar to what kind of artery?
Muscular
What is the tunica adventitia of arterioles primarily made of?
Connective tissue
What is the tunica media of arterioles primarily made of?
Smooth muscle
What is significant about the lumen size of arterioles?
Usually about the same width as the vessel wall
Is the tunica media the thickest and most dominant layer of all types of arteries?
Yes
What type of artery has the most developed internal elastic lamina?
Muscular artery
Which is the thinnest of the major luminal wall layers in arteries?
Tunica intima
What effect does aging have on elastic arteries?
Width increases into your 20s
Number of elastic laminae increase in the tunica media
What effect does aging have on muscular arteries?
Collagen and proteoglycans increase after middle age so there is a decrease in flexibility
Which specific muscular arteries are largely affected by aging leading to decreased flexibility?
Coronary arteries
What is the artery-based reason for increased systolic blood pressure around the age of 50?
Decreased elastic fibers and increased collagen type I
What arteries are usually affected by arteriosclerosis?
The largest ones
What happens to the tunica intima during arteriosclerosis?
Becomes infiltrated with soft lipid causing lumen diameter to decrease
What happens to the tunica media during arteriosclerosis?
Accumulation of collagen type I and sulfated GAGs
The tunica intima is a continuation of what layer of the heart?
Endocardium
What part of the artery increases in width and results in a decreased lumen size during atherosclerosis?
Tunica intima
What is a short terminal arteriole branch that lacks a true tunica media?
Metarteriole
Metarterioles lead to what other vessels?
Capillaries and a thoroughfare channel that leads to venules
What structures control blood flow into the capillaries?
Pre-capillary sphincters
What is the purpose of pre-capillary sphincters?
Allow blood to pulse through true capillaries
Where are metarterioles found?
In all capillary beds
How are the vessel walls different in the arteriovenous anastomoses?
Thicker tunica media and tunica adventitia
What innervates the AVA?
Many ANS nerves (sympathetic and parasympathetic)
What is the function of the arteriovenous anastomoses?
To control the lumen size and therefore the amount of blood in the capillaries
What are the major locations of AVAs?
Skin and stomach (also erectile tissues)
What is the activity of the AVA when blood flow into the capillary bed is normal?
AVA is “closed”
What is the activity of the AVA when most of the blood bypasses the capillary bed?
AVA is opened
What is the activity of AVAs when less blood is being sent to erectile tissue capillaries?
AVA is “open”
What is the activity of the AVAs when blood is sent into erectile tissue capillaries?
AVAs are closed
What things control/influence blood flow into capillaries?
Metarterioles, AVAs, lumen size of terminal arteriole, pre capillary sphincters
What cells make up the general capillary structure?
Single layer of flattened endothelial cells
What is the function of capillaries?
Movement of large molecules
What is the function of pinocytotic vesicles seen with capillaries?
Form transient channels through cytoplasm to allow transfer of large molecules
What cell junctions are located between the endothelial cells of capillaries?
Fasciae occludens (discontinuous attachment)
What are the functions of the cell junctions of capillaries?
Exchange of macromolecules, allow cell movement
What is the most common capillary type?
Continuous capillaries
Where can continuous capillaries be found?
Muscle, connective tissue, many organs
Pericytes are considered to be what kind of cell?
Residual mesenchyme cells
Pericytes are numerous on what kinds of vessels?
Capillaries and venules
What can pericytes secrete?
Basement membrane and matrix (ECM) components
What cell types can pericytes change into?
Smooth muscle, endothelial cells, and fibroblasts
Do pericytes have the ability to divide?
Yes
What are the two functions of pericytes?
Healing and possibly regulating blood flow too
Where are fenestrated capillaries located?
Pancreas, intestines, endocrine organs, kidneys
What is the structure of fenestrated capillaries?
Pores with thin protein diaphragm containing 8 fibrils
What is the function of fenestrated capillaries?
To allow greater movement of molecules and cells
What are the locations of sinusoidal capillaries?
Bone marrow, liver, spleen, lymphatic organs, and certain endocrine organs
What is the structure of sinusoidal capillaries?
Enlarged diameter, many large fenestrae with no protein diaphragm
Which has no protein diaphragm: fenestrated or sinusoidal capillaries?
Sinusoidal capillaries
Which lacks a true tunica media: metarterioles or AVAs?
Metarterioles
Which has a thicker tunica media and tunica adventitia: metarticles or AVAs?
AVAs
Which cell type, with reparative potential, is found exterior to the capillaries?
Pericytes
How are veins similar to arteries?
Also have three tunics
How are veins different than arteries?
Not as uniform in structure, often larger in diameter, higher number
What is the structure of the valves of veins?
Two flaps of tunica intima and fibroelastic connective tissue
What are the functions of the valves of veins?
Protection by preventing back-flow, works with skeletal muscle to keep blood moving
What type of venules is the smallest and has the thinnest walls?
Postcapillary venules
Which type of venule has the most pericytes?
Postcapillary venules
What is unique about the layers of the postcapillary venules?
No tunica media nor tunica adventitia
What makes up the tunica intima of postcapillary venules?
Endothelium, small amount of connective tissue, numerous pericytes
What makes up the tunica intima of collecting venules?
Endothelium and small amounts of connective tissue
What makes up the tunica adventitia of collecting venules?
Connective tissues, fibroblasts, some pericytes
Is there a tunica media present in collecting venules?
No
What is unique about the tunica media of muscular venules?
Incomplete smooth muscle layer
What type of venules have the fewest pericytes in their tunica adventitia?
Muscular venules
What is the effect of an incomplete tunica media in muscular venules?
Leaky venules due to inflammatory products leaking through endothelial cell junctions
What is the difference between small veins and venules?
Small veins have a complete tunica media
What is usually the thickest/most dominant layer in a vein?
Tunica adventitia
Vasa vasorum is possible to be seen in what layer of medium veins?
Tunica adventitia
What is different between the tunica intima of veins and muscular arteries?
Veins would not have an internal elastic lamina
What is the structural exception involved with the superficial veins of the legs?
Tunica media is actually well-developed
What are some examples of veins in the legs with well-developed tunica medias?
Great and lesser saphenous veins
What is the structural exception involving pulmonary veins?
Well-developed tunica media, some cardiac muscle seen in the tunica adventitia near the heart
What large and important veins also exhibit structural exceptions by having some cardiac muscle in the tunica adventitia near the heart?
Superior and inferior cavae
What are the causes of varicose veins?
- Loss of skeletal muscle tone around the veins
- Degeneration of vessel wall
- Valve incompetence
What are varicose veins?
Enlarged and winding superficial veins of the legs
What are esophageal varices?
Varicose veins in the lower esophagus
Esophageal varices are commonly seen among what group of people?
Alcoholics
What is the cause of esophageal varices?
Portal hypertension
What are hemorrhoids?
Varicose veins at the end of the anal canal
What are the functions of the lymphatic system?
Drain excess interstitial fluid
Transport lymph to lymph nodes
Transport lymph to blood stream
What vascular structures do the lymphatic capillaries resemble?
Blood capillaries
Which has no pericytes: blood or lymphatic capillaries?
Lymphatic capillaries
What in the lymphatic capillaries allows for easy movement of materials into and out of the vessels that is different than blood capillaries?
Endothelial cells can overlap but create clefts between cells
What structure is in the lymphatic capillaries that supports endothelial walls so they capillaries stay open?
Lymphatic anchoring filaments
What kind of fibers make up the anchoring filaments of lymphatic capillaries?
Elastic
What vascular structures do small lymphatic vessels resemble?
Venules
The lymphatic ducts empty into the venous system at the junction of which veins?
Right internal jugular and subclavian veins
What specific ducts are included in the lymphatic duct system?
Short right lymphatic duct and the thoracic duct
What is the pattern of the tunica media of the lymphatic ducts?
Regular: made of longitudinal and circular layers of smooth muscle