Components of the cardiovascular system
Heart Arteries Veins Capillaries Lymphatic vessels
Layers of the heart
Epicardium
Myocardium
Endocardium
Components of Epicardium
Mesothelial lining
Connective Tissue Underlying the mesothelium
Mesothelial Lining of the epicardium
covers the external surface of the heart
Connective tissue underlying mesothelium of the epicardium
Loose connective tissue, adipose tissue
Nerves pass through this layer
Blood vessels travel to the myocardium through this layer
Principle component of heart wall
Myocardium (thickest layer)
Thickness of myocardium in the atria vs ventricles
Thicker in the ventricles
Most internal layer of the heart
Endocardium
Components of endocardium
endothelium
subendothelial connective tissue
impulse conducting system
Describe the internal skeleton of the heart
Four fibrous rings that surround the valve orifeces
All within the atrioventricular plane (one continuous sheet)
Purpose of a trigone
to connect fibrous tissue rings surrounding valves together
left atrioventricular rings surrounds what valve
Mitral valve
Right atrioventricular ring surrounds what valve
Tricuspid
Left trigone connects what?
left atrioventricular ring (mitral) and aortic fibrous rings
Right trigone connects what?
left (mitral) and right (tricuspid) atrioventricular rings
Membranous Part of the interventricular septum
Devoid of cardiac muscle
Composed of dense irregular connective tissue
Contains part of the AV bundle
Where dies Ventricular Septal Defect occur
in the membranous portion of the IV septum
layers of valves
1: Fibrosa
2: Spongiosa
3: Atrialis
Fibrosa
formed of DICT connected to corresponding fibrous ring
Extends form the base along the ventricular side of atrioventricular valves
Which layer of the valve faces the ventricular side of the atrioventricular valve
fibrosa
Spongiosa
Formed of loose connective tissue
large amounts of elastic fibers
Most prominent on free edges of the valve
Where do you find the spongiosa layer of the valve, what is the purpose of this layer
most prominent on the free edges
Purpose: shock absorption (dampens vibrations as the valve closes)
Atrialis
covers the atrial aspect of spongiosa
Rich in proteoglycans
Contains elastic fibers and occasional smooth muscle cells
What layers of the valve contain elastic fibers
Spongiosa
Atrialis
Which layer(s) of the valve (may) contains some smooth muscle cells?
Atrialis
Mirtal Valve stenosis
inflammation of valve leaflets that promotes angiogenesis leading to formation of fibrotic tissue resulting in stenosis of the valve
Rheumatic fever can be a cause
Describe the ANS and heartbeat
ANS can REGULATE the heart beat but it does not INITIATE heartbeat
Parasympathetic - HR
Decrease HR
Sympathetic- HR
Increases HR
Effect of hormones and other substances on HR
can change the rate and force of contraction
ex: Epinephrine, thyroid hormones, caffeine
What are cardiac conducting cells called
Purkinje Fibers
Describe Purkinje fibers
modified cardiac myocyte (modified to conduct electrical impulses)
contain a lot of glycogen
can transmit faster than myocytes
still have intercalated discs
What do Purkinje fibers form
Nodes and bundles
including the sinoatrial and atreoventricular node and bindle of His
Myocardial infaction
caused by obstruction of coronary arteries and loss of blood supply to the cardiac muscle for more than 20 minutes
Is MI reversible? Why
No- Nuclei get spit out (cell death)
myocytes are unable to regenerate/ proliferate and get replaced by a scar
Atherosclerosis involves what layer of the vessel
Tunica intima thickening- narrows the lumen eventually causing rupture- clot will form due to exposed collagen
Most common benign tumor of the heart
Myxoma (bunch of loose connective tissue)
Commonly found in the left atrium
Angiosarcoma
rare tumor that originates in the heart (1/3 of all tumors that originate in the heart)
One of the most common tumors to spread to the heart
Metastatic Melanoma
Layers of blood vessels
Tunica intima
Tunica media
Tunica Adventitia
Components of tunica intima
endothelium
subendthelial connective tissue
internal elastic lamina
What lines the luminal surface
Endothelium of the tunica intima
Functions of Endothelium
1: Selective permeability (transcellular, paracellular, fenestrations)
2: Non-Thrombogenic factor
3: Modulation of blood flow
4: Regulation/Modulation of Immune Responses
5: Hormonal Synthesis
6: Metabolic activity
Endothelium
Transcellular pathway
allows active transport across the plasma membrane
Clatherin- independent pathway is used to transport material from blood into the cell
Clatherin- DEpenent pathway is used to transport LDL and cholesterol
Endothelium
Paracellular Pathway
Passive transport across zonula occuludens
Normally blocked by zonula occludens but in the case of inflammation the immune cells need to get out of the blood(causes edema and allows extravagation)
Endothelium
Fenestrations
Endothelial cells have holes in them that allow for the passage of fairly large molecules
(kidney and endocrine glands)
Endothelium
Non-Thrombogenic Barrier
Produce/ Secrete
- Anticoagulants (thrombomodulin) - Antithrombogenic substances
In situations when the endothelium becomes damaged it secretes Thrombogenic agensts such as von Willebrand factor (triggers the clotting cascade)
Endothelium
Modulation of blood flow
Vasoconstrictors
- ACE (increase BP through Angiotensin) - Endothelian - Thromboxane
Vasodialators
- NO - Prostacyclin
Endothelium
Regulation/Modulation of Immune Responses
control of leukocyte adhesion (movement of wbc into blood)
Secretion of interleukins and cytokines (IL-1, IL-6, IL-8)
Endothelium
Hormonal synthesis
Growth factors
- Colony stimulating factor (CSF)
- Fibroblast growth factor (FGF)
- Platelet derived growth factor (PDGF)
Growth factor inhibitors
- Tranforming growth factor B (TGF-B)
Endothelium
Metabolic activity
Angiotensin I –> Angiotensin II
through ACE to increase blood pressure
Subendothelial layer of tunica intima
Loose connective tissue
Internal Elastic Lamina of tunica intima
flattened fenestered sheet of elastin
separates tunica intima from tunica media
Tunica Media
middle layer of blood vessels
mostly smooth muscle (circularly arranged)
External elastic lamina
Where is external elastic lamina located
tunica media
where is internal elastic lamina located
tunica intima
What is the purpose of tunica media
maintain the architecture of the vessel
Tunica Adventitia
Most external layer composed of mostly connective tissue smooth muscle fibers (longitudinally arranged) Small blood vessesl (vasa vasorum) small nerves (nervi vasorum)
Which layer of blood vessels contains longitudinally arranged smooth muscle?
Tunica adventitia
Which layer of blood vessels contain circularly arranged smooth muscle?
Tunica media
Which blood vessel layer contains small blood vessels and veins
Tunica media
Three major types of arteries
Large elastic (conducting)
Muscular arteries
Small arteries and arterioles
Which type of arteries controls resistance
Small arteries and arterioles
Purpose of Arterioles
control blood flow to capillary network
Contracting smooth muscle cells
Depending on the type of activity the arterioles direct the blood to the organs that need it most
Do capillaries contain three tunics in their walls?
No- walls are made up of single layer of epithelium and their basal lamina
Types of capillaries
Continuous Capillaries
Fenestrated Capillaries
Discontinuous Capillaries
Continuous Capillaries
Continuous basal lamina
tight occluding junctions
Where are continuous capillaries found
muscles, lungs, CNS
Fenestrated capillaries
small holes in the endothelial cells (10-100 mm)
** basal lamina remains intact (acts as a filter)
Where are fenestrated capillaries found
in tissues where there is substantial fluid transport
intestinal villi, choroid plexus, renal glomeruli, endocrine organs
Discontinuous capillaries
endothelial cells separated by larger gaps (150-175 mm)
** holes extend into the basal lamina
Where are discontinuous capillaries found
Liver (sinusoids), spleen, bone marrow
Three major types of veins
Small veins (venules) Medium veins (less than 1 cm) Large veins (greater than 1 cm)
Divisions of small veins
Postcapillary venules
Muscular venules
Postcapillary venules
receive blood from capillaries
What layer is missing in postcapillary venules
tunic media
Principle site of immigration of WBC
Postcapillary venules - High endothelial venules
High endothelial venules
postcapillary venules of lymph organs
have columnar endothelium
Muscular Venules
collect blood from postcapillary venules
have a tunica media - VERY thin
order of venous blood flow
1: Post capillary venule
2: Muscular venules
3: Medium veins
4: Large veins
5: Heart
purpose of venous and lymphatic valves
ensure unidirectional flow
Permeability of lymphatic capillaries compared to blood capillaries
Greater permeability of lymphatic capillaries