ANATOMY - Blood Vessel Histology Flashcards
What are the three histological layers of a typical blood vessel?
Tunica adventitia
Tunica media
Tunica intima
What kind of tissue makes up the tunica adventitia?
Connective tissue
What is the functional significance of the connective tissue which makes up the tunica adventitia?
Protection and the prevention of over-extension of the blood vessel
What kind of tissue makes up the tunica media?
Fenestrated elastic fibres and smooth muscle
Which dye can be used to highlight the fenestrated elastic fibres in the tunica media?
Millers stain
What is the functional significance of the fenestrated elastic fibres and smooth muscle which make up the tunica media?
Fenestrated elastic fibres allow for shock absorption, the fenestrae allow for diffusion and smooth muscle allows for vasoconstriction and vasodilation
What kind of epithelium lines the tunica intima?
Endothelium (simple, squamous epithelium)
What is the functional significance of the endothelium which lines the tunica intima?
Endothelium provides low frictional resistance to allow for smooth blood flow
What are the three main anatomical classifications of arteries?
Elastic arteries
Muscular arteries
Arterioles
What is the function of elastic arteries?
Elastic arteries conduct blood at high pressures
How does the structure of elastic arteries accommodate their function?
Elastic arteries contain more elastic fibres within their tunica media which allows for extra shock absorption when conducting blood at such high pressure
Give two examples of elastic arteries
Aorta
Pulmonary trunk
What are vasa varosum?
Vasa varosum are small blood vessels within the tunica adventitia of large arteries which provide nutrients to the tunica adventitia and tunica media
What is the function of muscular arteries?
Muscular arteries regulate the blood flow to different tissues through vasodilation and vasoconstriction based on the body’s level of activity
How does the structure of muscular arteries accommodate their function?
Muscular arteries contain more smooth muscle in their tunica media for vasoconstriction and vasodilation to control blood flow to different tissues based on the body’s level of activity
What is the extra layer found between the tunica intima and tunica media in muscular arteries?
Internal elastic lamina
What classifies an artery as an arteriole?
An artery is classified as an arteriole if it has less than five layers of smooth muscle in its tunica media
What is the function of arterioles?
Arterioles provide resistance to blood flow to decrease the blood pressure in order to regulate the volume of blood entering the capillaries
What are metarterioles?
Metarterioles are arterioles which have only one layer of smooth muscle in their tunica media
What is a pre-capillary arteriovenous shunt?
A pre-capillary arteriovenous shunt is a connection between an arteriole and venule which bypasses the capillary bed
What is an arterial portal shunt?
A connection between two arterioles which allows blood to pass through one capillary bed followed by another capillary bed before entering the venous system
What is a venous portal shunt?
A connection between two venules which allows blood to pass through one capillary bed followed by another capillary bed before entering the arterial system
What are the functions of capillaries?
Capillaries are tiny blood vessels which connect arterioles and venules to allow for the exchange of oxygen, nutrients and waste materials between blood and tissues
What is the general structure of a capillary?
A capillary consists of a tunica intima layer with associated pericytes
What are the functions of pericytes?
Pericytes are undifferentiated cells which can differentiate into any other cell type and contribute to capillary repair
What are the three anatomical classifications of capillaries?
Continuous capillaries
Fenestrated capillaries
Sinusoids
How does the structure of continuous capillaries accommodate their function?
The endothelium lining of continuous capillaries has junctional complexes which allow for a varying degrees of permeability depending on which tissue type the capillaries are located in
How does the structure of fenestrated capillaries accommodate their function?
Fenestrated capillaries have openings within their endothelial lining called fenestrae which allow for increased permeability
What is the difference between open and closed fenestrated capillaries?
In open fenestrated capillaries, the fenestrae are uncovered however closed fenestrated capillaries have a diaphragm covering their fenestrae
Give an example of an organ that contains open fenestrated capillaries
Kidneys
Give an example of an organ that contains closed fenestrated capillaries
Intestines
How does the structure of sinusoids accommodate their function?
Sinusoids have a discontinuous endothelium with no basal lamina, creating large gaps for high permeability
Give two example of organs which contain sinusoids
Liver
Spleen
What is the main function of the venous system?
Capacitance (storage) of blood
What are the two anatomical classifications of venules?
Post capillary venules
Muscular venules
What is the main function of post capillary venules?
Post capillary venules allow for diapedesis to occur
How does the structure of post capillary venules accommodate their role in diapedesis?
Post capillary venules only have an tunica intima layer with endothelial cells which have junctional complexes to allow white blood cells to move from the bloodstream into surrounding tissues
(T/F) Post capillary venules are surrounded by pericytes
TRUE.
What is the function of muscular venules?
Muscular venules are capacitance (storage) blood vessels
What is the distinguishing feature of large peripheral veins?
Large peripheral veins have valves
What is the function of valves in large peripheral veins?
Valves prevent the backflow of blood
What is the thickest histological layer of large central veins?
Tunica adventitia
What is unique about the tunica media layer of large central veins?
As large central veins approach the heart, the smooth muscle within the tunica media layer transitions to cardiac muscle
Give two examples of large central veins
Cranial vena cava
Caudal vena cava
How do you differentiate veins and arteries in histology?
Veins:
Thin walls
Larger lumen
Valves
Arteries:
Thick walls
Smaller lumen
Internal elastic lamina
What are the four histological features of lymphatic vessels?
Tunica intima
Valves
Thinner walls than veins
Contain lymph
