Anatomy of the CVS 2 Flashcards
What makes up the endocardium and epicardium?
Simple Squamous Epithelium + Basement Membrane + Connective Tissue
The heart is essentially a twisted blood vessel. What are the comparable layers between the heart wall and vessel’s walls?
Endocardium - Tunica Intima
Myocardium - Tunica Media
Epicardium - Tunica Adventitia
The epicardium is slightly different to the tunica adventitia, what is the difference?
The tunica adventitia lacks epithelium and a basement membrane.
Whats the difference between the myocardium and tunica media?
Myocardium = Cardiac Muscle
Tunica Media = Smooth Muscle & Elastic Tissue
What are the visible differences between arteries and the accompanying vein (histologically)?
Diameter: Vein > Artery
Thickness of Wall: Artery > Vein
Thickness of Tunica Media: Artery > Vein
Thickness of Tunica Adventitia: Vein > Artery
Which level of vessel have the greatest individual diameter and total cross-sectional area?
Arteries/Veins have the biggest individual diameter
Capillaries have the largest total cross-sectional area
Look at histology images in lecture of arteries etc.
Remember Tunica Intima is fucking tiny in an artery and Tunica Media is pretty Phat.
Name 3 types of arteries + their function and examples
Elastic - Large Conducting - Aorta, Common Carotid, Pulmonary Trunk
Muscular - Distributing to regions - Coronary, Radial & Femoral
Arterioles - Terminal branches supplying capillary bed.
The aorta is an elastic artery, during which stage of the cardiac cycle is it stretched?
During Systole
How do elastic arteries maintain the pressure during dystole?
The arteries recoil in order to maintain pressure even when the heart relaxes.
What allows the elastic arteries to recoil and stretch?
Extensive amounts of elastic fibres in the Tunica Media arranged into layers or laminae.
How are elastic fibres produced?
They’re secreted by smooth muscle
How do you differentiate between veins and arteries histologically?
Generally:
Arteries are smaller in diameter and have a thicker wall
Veins have a thicker Adventitia but a thinner Media
How do you tell between an elastic and muscular artery?
A muscular artery only has elastic fibres in 2 laminae, one at each edge of the T. Media.
An elastic artery has a T. Media full of dark blue elastic fibres
What do we call the two elastic laminae in a muscular artery?
Just under the epithelium (T. Intima) is the Internal Elastic Lamina (IEL)
Between the T. Media & T. Adventitia is the External/Outer Elastic Lamina (OEL)
Whats differnt about an arteriole to larger arteries histlogically?
Arterioles lack a Tunica Adventitia
The T. Media is only a couple layers of muscle thick
There is no elastic Laminae
What are the functions of arterioles?
Controlling Blood Pressure
Controlling blood flow to capillary beds
What nervous system innervates the arterioles?
Sympathetic Nervous System
What layers are present in a capillary wall?
Just the Tunica Intima. So it can exchange nutrients and gases easily
What are pericytes?
Pericytes are an incomplete layer of cells around the basement membrane of capillaries.
What do pericytes do?
They contract to control the flow of blood in capillaries.
Why is the BP of capillaries lower than that of the Aorta?
Because theyre cross sectional area is larger overall than that of the aorta.
What are the 3 types of capillary?
Continuous - Complete endothelial & basal lamina layers
Fenestrated - Complete basal lamina but fenestrated endothelial lining
Discontinuous - Incomplete basal lamina and fenestrated endothelial lining.
What is the function of continuous capillaries?
They can control what is exchanged because it must pass through the cell or junctions to get in/out. (i.e. selective transport)
What tissue are continuous capillaries found in?
Muscle
What are fenestrations?
Pores
Where are fenestrated capillaries found?
In endocrine glands and kidney renal corpuscles
Some fenestrated capillaries have protein diaphragms over the pores, what do they do/
Protein diaphragms filter the molecules attempting to pass through by molecular weight and/or charge
What do discontinuous capillaries do?
Allow free passage of any fluid, molecule or cell.
Where are discontinuous capillaries found?
Liver
Spleen
Bone Marrow
What are sinusoids?
A type of discontinuous capillary with a large diameter and phagocytic cells in its T. Intima
Where do you find sinusoids?
Wherever larger amounts of exchange take place.
Specifically:
- liver
- Some endocrine glands
What does an arteriovenous (AV) shunt do and where would you find one?
Its a vessel enabling blood to bypass the capillary beds.
Theyre found in the skin for thermoregulation
How do arterioles control which capillaries/shunts receive blood?
Precapillary sphincters can control what capillaries or shunts are open.
Describe the structure of veins?
The T. Intima is thin
The IEL & OEL are thin or absent
The T Media are thin or absent
T. Adventitia is made of collagenous tissue
What prevents backflow out of veins?
Valves projecting from the endothelium (T. Intima)
Which is thicker a deep or superficial vein?
Deep veins are thick walled and superficial veins are thin walled.
The superficial vein has no support, what supports the deep vein?
The deep fascia and muscle
In what tissue are superficial veins found?
Inside the superficial fascia
Where do we most commonly find lymph nodes?
Alongside major veins
Around the origins of major arteries
How is flow kept in the right direction in the lymphatic system?
VALVES
Are lymph capillaries fenestrated?
Ye….NO
What lines the blind ended lymphatic capillaries?
A rudimentary basal lamina (often absent)
Very thin endothelium
The lymph capillaries are kept at the -ve hydrostatic pressure so they can drain fluid from the tissues. How are they kept open (instead of being flattened by the higher pressure outside.)
Anchoring filaments
They’re fine collagenous filaments that link the endothelial cells to the surrounding tissue.
How do we easily tell a lymph capillary from venules and arterioles?
Lymph capillaries lack any RBCs in they’re lumen, it should be clear.
What supplies blood to the blood vessels themselves?
The Vasa Vasorum (“vessels of the vessels)
Some blood vessels contain lymphatics, what layer are these found in?
The T. Adventitia
What nerves supply blood vessels?
Sympathetic and parasympathetic.
