Structures of Blood vessels and Heart Flashcards
Order of blood vessels the blood passes through after the heart
Heart Elastic arteries Muscular arteries Arterioles Capillaries Venules VEins Muscular veins
What is the innermost layer of the blood vessels
Tunica intima
What is the middle layer of the blood vessels
Tunica media
What is the outermost layer of the blood vessels
Tunica adventitia
What does the tunica intima have lining the lumen
What does it have adjacent to this
Simple squamous epithelium lining the lumen
AN adjacent layer of connective tissue
What is the tunica media made of
- Smooth (or cardiac) muscle which is mainly circular
- Varying amounts of elastin, mainly in sheets in the interspersed connective tissue
What does the tunica adventitia consist of
-connective tissue with varying amounts of interspersed elastic fibres and smooth muscle cells (mainly longitudinal)
What layers does the heart have
Endocardium (tunica intima)
Myocardium (tunica media)
Epicardium (tunica adventitia)
What is the difference between the tunica media in the heart vs vessels
In the tunica media, it consist of cardiac and not smooth muscle
What is the squamous epithelium in the endocardium lined by
Thin band of relatively loose connective tissue
What is the myocardium supplied by
Coronary vessels
What is the epicardium like
Partially dense, partially loose connective tissue
What is the connective tissue in the epicardium bordered with
Simple squamous epithelium (visceral pericardium) which forms the inner lining of the pericardial sac
What is pulsating blood flow met by In elastic arteries
Lamellae of elastin woven into the media
What do muscular arteries do
Help distribute the bulk of blood to the site of need eg to the leg muscles when cycling
Using a histological stain and looking at the tunica media, what does collagen look like
Red with few thin interspersed elastin sheets
USing a histological stain and looking at the tunica media, what do the circular smooth muscle cells look like
Brown
Using a histological stain, what does the external elastic membrane look like in the tunica media
Black
What is a blood vessel with a perpendicular pattern most likely to be
Artery or arteriole
Which vessels are the main site of blood pressure regulation
Arterioles
How many smooth muscle cells would an arteriole have
1-3
Why are there no internal elastic membranes in small arteries and arterioles
Because flow is not pulsating anymore
Why do small arteries and arterioles not have vasa vasorum
Because their walls are small enough to be supplied by diffusion
What do capillaries not have
Media or adventitia
What do capillaries contain
One layer of endothelial cells
A few collagen fibres around it
How are larger molecules transported through capillary walls
IN small vesicles by pinocytosis
Difference between continuous capillaries and fenestrated capillaries
-Continuous= Lumen is lined by a continuous uninterrupted layer of single endothelial cells that are linked by cell-cell contacts containing tight and adherent junctions
Fenestrated= numerous pores in their endothelial cells. Therefore the barrier to the interstitial is the basement membrane
Where are sinusoids found
Liver and the spleen
What are sinusoids
Beds of wide capillaries with diameters of several erythrocytes. Their endothelial cells and basement membranes have holes which allow plasma to directly reach cells. This allows fast exchange of larger components
What are pericytes
cells that wrap around endothelial cells throughout the body. They are essential for the regulation of blood flow and maintenance of homeostasis within the body, such as the blood-brain barrier.
What do venules not have
No media and no or hardly any adventitia
In the extremities, what are muscular arteries often accompanied by and what does this do (vein-artery-vein triplets)
Accompanied by veins on either side so that the pulsations slightly compress the veins, driving the blood towards the heart due to the valves
What does the portal vein do
Links the capillary beds of the digestive system and spleen directly to the capillary bed (sinusoids) of the liver
What is an anastomosis
Direct link between an artery or vein without a capillary bed in between
How does fluid enter the lymphatic system
Blood circulation is slightly leaky and so fluid leaves mainly in the capillary beds.
Why does fluid leave the capillary beds
Because of blood pressure and osmotic differences between blood and interstitial fluid
Pathway of fluid before it goes into lymphatic vessels and back into the blood circulation
Fluid leaks out, and drains from the tissues as lymph via lymph vessels which feed as afferent lymphatics into lymph nodes. Lymph is checked for antigens in lymph nodes. After checks, the lymph enters the lymphatic ducts, which empty into the subclavian veins.
