Circulatory System Flashcards
Endocardium contains:
- Endothelium
- Supporting CT
- Some adipose tissue
Myocardium contains:
- Cardiac myocytes
2. Purkinje fibers
Epicardium AKA:
Adventitia
Pericardium AKA:
Outer membrane
Purkinje fibers
Conduction system of heart
Cardiac skeleton
Fibrous skeleton of the heart → structure of dense CT which separates atria from ventricles
Annulus
Cardiac skeleton (CT) surrounding valves
Trigone
Cardiac skeleton (CT) → triangular area between 2 AV canals and aortic valve
2 parts of cardiac skeleton
- Annulus
2. Trigone
Heart valves are made of?
Folds of endocardium
Heart valves are supported by?
Cardiac skeleton (dense CT)
Edges of cusps of valves are anchored by?
Chordae tendinae
3 layers in blood or lymph vessel
- Tunica intima
- Tunica media
- Tunica adventitia
Epicardium contains?
- Mesothelium → secretes serous fluid
- Supporting CT
- Broad adipost tissue
Purkinje fibers derived from?
Cardiac muscle
Purkinje fiber cells
Cells larger than muscle fiber → no T-tubules
3 layers of tunica intima
- Endothelium (always)
- Subendothelial CT (sometimes)
- Internal elastic lamina (sometimes)
Tunica media
Smooth m. with varying amounts of elastic lamina
External elastic lamina is in what layer?
Tunica media
Tunica adventitia
CT of vessel wall
Tunica adventitia CT
Dense or loose irregular
In larger vessels, the tunia adventitia carries?
Blood and nerve supply for that vessel:
- Vasa vasorum
- Nervi vasorum
Vasa vasorum
Blood supply for vessel
Nervi vasorum
Nerve supply for vessel
Examples of elastic aa.
- Aorta
- Pulmonary
- Carotid
Tunica intima is found where?
Innermost layer, just inside endothelium
Tunica intima of elastic aa.
Very thin → internal elastic lamina difficult to observe
Tunica intima of elastic aa. contains?
- Fibroblasts
2. Myointimal cells
Atherosclerosis caused by?
Myointimal cells deposit lipid and thicken with age
Tunica media of elastic aa.
Thickest layer → external elastic lamina not readily apparent
Tunica media composition in elastic aa.
Concentric layers of elastin with smooth m. cells and reticular fibers between layers
Tunica adventitia in elastic aa.
Thin compared to tunica media
Muscular aa. found where?
Peripheral aa.
Tunica intima of muscular aa. contains?
- Endothelium
- CT
- Internal elastic lamina
Tunica intima of muscular aa. appearnce
Difficult to see → only visible in pathological conditions (ex: atherosclerosis)
What layer of muscular aa. thickens to increase peripheral blood pressure?
Tunica intima
Thickening of tunica intima (high blood pressure) can cause?
- Hypertension
- Coronary artery disease
- Stroke
- Aneurysm
Tunica media in muscular aa.
Thick layer of smooth m., contains fibers and proteoglycans
External elastic lamina
Made of elastin fibers → divide tunica media and adventitia
Tunica adventitia of muscular aa.
Very thick external CT layer
Artery lumen diameter
> 0.3 mm
Artery must have ___ layers of muscle cells
> 3
Arteriole elastic lamina
No external, diminishing internal
Arteriole must have ___ layers of muscle cells
Smallest branch of arterial system
Arterioles
Arteriole function
Delivers and regulates floor blood to capillary bed
How do arterioles regulate systemic blood pressure?
Arteriole constriction increases resistance to peripheral blood floow
NO produced by?
Vascular endothelial cells and macrophages
NO function
Vasodilation (very potent)
NO is synthesized from?
L-arginine
Tunica intima of arterioles
Internal elastic lamina disappearing
Tunica media of arterioles
1-3 layers of smooth muscle cells
Tunica adventitia of arterioles
Narrow layer of CT
Capillaries consist of?
Only endothelium and basement membrane
4 types of capillaries?
- Continuous
- Fenestrated
- Discontinuous
- Sinusoidal
Continuous capillaries have?
No pores in endothelial cells
Continuous capillaries most commonly found in?
- Muscle
- Brain
- Thymus
- Bone
- Lung
Fenestrated means?
Windowed
Fenestrated capillaries have?
Pores in endothelial cells (+/- diaphragm)
Fenestrated capillaries most commonly found in?
Tissues with substantial fluid transport:
- Intestine
- Kidney
- Endocrine
Discontinuous capillaries
Gaps between cells
Discontinuous capillaries are found in?
Liver and spleen sinusoids
Sinusoidal capillaries are?
Special
Sinusoidal capillaries are found in?
- Liver
- Spleen
- Bone marrow
- Lymph nodes
Sinuisodal capillary appearance
- Wide lumen
2. Incomplete basal lamina
Capillary diameter
Same as RBC (7-9 um)
Sinusoid diameter
30-40 um
What allows for capillary function?
Very thin endothelial cell layer
Capillary function in tissue beds
Allow for exchange of water and solutes between blood and tissue
Capillary function in lung
Allow for exchange of water and solutes between blood and environment
4 cells in capillaries
- Pericytes
- Pericyte derivatives
- Mast cell
- Scattered smooth muscle cells
What is a pericyte?
Residual mesenchymal / stem cell
Example of pericyte derivative in capillaries
Mesangial cells of glomerulus
Meangial cell function?
Controls blood flow
How is blood flow controlled?
What tells capillaries to constrict or dilate?
- ANS
2. Circulating hormones
Microcirculation is the?
Interaction of arterioles and venules through capillaries at peripheral tissues
4 things microcirculation exchanges
- Gas
- Nutrient
- Fluid
- Metabolic waste
Variables in microcirculation
- Capillary diameter
- Capillary endothelium
- Arteriovenous shunts
- Capillary network abundance
Microcirculation blood flow
Arteriole → Capillaries → Post-capillary venule → Collecting venule → Muscular venule
Venules are?
Similar to capillaries with a larger diameter
Tunica intima of venules
Endothelium only
Tunica media of venules
Thin layer or not present
Tunica adventitia of venules
Present
How do you distinguish between venules and small veins?
If it’s next to an arteriole, call it a venule
Tunica intima of veins
Present
Tunica media of veins
Few layers of irregularly arranged smooth muscle (may be discontinuous)
Tunica adventitia of veins
Thickest part of wal
3 ways to differentiate arteries from veins
- Veins/venules have thinner wall
- Arteries and veins or arterioles and venules are found side-by-side
- Arteries don’t have valves; many veins do
Vein appearance
- Thin muscular wall
- No internal elastic lamina
- Wide lumen (compared to wall thickness)
- Packed with RBCs
What veins do have internal elastic lamina?
Large veins
What is a neurovascular bundle?
Similar sized vessels, nerves and lymphatics travel together
What is the lymphatic circulation?
One-way tissue fluid drainage system
Lymphatic circulation is associated with?
Venous system
Function of valves in the lymphatic circulation system?
Ensure fluid moves toward large veins cranial to heart
Pressure of lymphatic circulation
Very low
Very low pressure in lymphatic circulation pathology
Easily occluded, obstructed or overwhelmed → edema
Lymph capillaries
Blind-ended
Lymp capillaries begin in?
Perivascular spaces of tissue beds
Lymph vessel function
Transport excess interstitial fluid, proteins, solutes and macromolecules through lymph nodes and back to venous system
Lymph vessel safety valves are located between?
Extravascular and intravascular fluid pools
Function of lymph vessel filtering system
Impedes MOs and cancer cells
Lymphatic capillary contains
Extremely thin endothelium only → no basement membrane
How do you find lymphatic capillaries?
Look like a space in the tissue → look for endothelium
How do you distinguish between large lymph vessels and veins?
- Lymph vessels have thinner walls
- More numerous valves (lymph > veins)
- No RBCs in lymph vessels
Lymph vessels contain?
WBCs (no RBCs) and precipitated protein
Circulatory shock is?
Life-threatening acute symptom
Circulatory shock occurs when?
Hypovolemia of >35%
Hypovolemia can be caused by?
- Blood loss
2. Extreme vasodilation by endotoxin
How does hypovolemia lead to circulatory shock?
Widespread inadequacy of tissue perfusion
Widspread inadequacy of tissue perfusion leads to?
On a cellular level, don’t say hypovolemia or circulatory shock
- Cellular hypoxia
- Cellular injury / organ damage
- Lactic acidosis
How does hypovolemia cause lactic acidosis?
Lactic acid is released from damaged cells
What is peripheral vasoconstriction?
Compensation for circulatory shock
Peripheral vasoconstriction function
Preserve blood flow to vital organs
How does peripheral vasoconstriction preserve blood flow to vital organs?
Decreases capillary hydrostatic pressure
How does peripheral vasoconstriction decrease capillary hydrostatic pressure?
Facilitates flow of interstitial fluid into circulation
Arteries can be either?
Elastic or muscular
Main difference between elastic and muscular aa.
Tunica media in elastic arteries contains concentric sheets of elastin
