LECTURE 7 Flashcards
Location of the heart
In the mediastinum with the lungs
Level of the 2nd rib
Roughly central, but with the base pointing towards the right and the apex towards the left.
What is the pericardium
The heart sits in a “bag”: pericardium
Lubrication (serous)
Mechanical protections
Ie protects it and allows it to move smoothly
3 main layers of pericardium
Pericardium has 3 main layers:
Fibrous pericardium
Serous pericardium
Epicardium
What is pericarditis
Problems with the pericardium, which impact the movement and function of the heart.
3 main muscle layers of the heart wall
Epicardium
Myocardium
Endocardium
Purpose of atrioventricular valves
prevent back flow from Atria to Ventricles
Purpose of semilunar valves
prevent backflow from Aorta/Pulmonary artery into the Ventricles
Purpose of chordae tendinae
stop valves acting like a swing door in both directions
Heart valve problems - incompetent valves
Valves (leaflets) do not fully close so there is regurgitant flow i.e. the same blood is pumped around repeatedly (leaky)
Heart valve problems - valvular stenosis
stiffened valves caused by repeated infection, congenital disease or calcium deposits. Opening is narrowed so insufficient blood gets through.
3 layers of arteries and veins
Tunica adventitia/externa:
supportive outer. Nerves and blood vessels
Tunica media:
muscular middle, affects resistance to blood flow (ie involved in control of blood pressure)
Tunica intima:
endothelial, inner, layer creates a smooth surface and involved in communication
Why is the tunica media the most important layer
Helps move blood along the arteries
Vasoconstriction of smooth muscle decreases lumen size
Vasodilation of smooth muscle increases lumen size
Large arteries
More muscular walls push blood along to organs.
Distribution role.
Renal, carotid, mesenteric.
Don’t affect BP.
Elastic to absorb high volume and pressure from heart
Small arteries
Distribution and resistance.
Highly innervated.
Regulate arterial Pressures.
Receptors for circulating hormones and locally produced signals ie K+ and NO
Arterioles
smaller; when constricted, blood flow to organs can be bypassed.
Resistance vessels.
Same as small arteries
Capillaries
small and thin to allow for exchange of materials.
No smooth muscle.
Types of capillaries
Continuous capillaries
Fenestrated capillaries
Sinusoid capillaries
Continuous capillaries
Most common
Continuous. Gaps only between endothelial cells (tight junctions)
CNS, lungs, muscle tissue, skin
Fenestrated capillaries
Pores of 70-100nm in the capillary wall
Choroid plexus, kidneys, endocrine glands, villi and ciliary processes of the eye
Sinusoid capillaries
Wider gaps in the vessel walls (Lets blood cells through)
Bone marrow, endocrine glands, placenta
2 vessels in venous system
veins and venules
Veins
Under less pressure
Less smooth muscle (less resistance)
Stretchy (high capacitance vessels)
Larger veins have valves to prevent blood flowing backwards.
Venules
8-100µm in diameter, more porous than arterioles.
Capillaries drain into venules
Continued loss of BP, almost 0 by the time it gets to the vena cava
Where can the blood go when it exists the heart
Pulmonary Circulation (RHS)
Systemic Circulation (LHS)
Coronary Circulation (from aorta)
Pulmonary circulation
Positioned towards back of the heart.
Crescent shaped
Blood in through Venae cavae
Back out through pulmonary artery
Systemic circulation
At front and apex
More circular (thicker walls)
In through pulmonary veins
Out through Aorta to aortic arch
CORONARY CIRCULATION
L and R Coronary arteries from the base of the aorta. Shut during contraction
Coronary arteries branch to supply the heart
Arteries supply the capillaries for gas and nutrient transfer before draining into the veins
What is ABO blood type determined by
different alleles
What happens when a blood transfusion occurs with the wrong blood type
the antibodies bind to the RBCs expressing the different antigen. This causes clumping of the RBCs and antibodies (agglutination) and causes severe problems.
Universal donors
type O blood
do not have A or B antigens
Make antibodies to A and B
cannot receive blood from any other blood type.
Universal receivers
type AB blood
have A and B antigens
do not make any A or B antibodies
Won’t agglutinate donor blood
their blood can only be given to AB recipients
Others have antibodies to A, B or both
Which blood type alleles are dominant/recessive
Both A and B alleles are dominant over O
ABO INCOMPATIBILITY IN BABIES
Can occur during pregnancy if mother and baby’s blood types are incompatible
e.g. mother has blood type O and baby is either A or B, and their blood comes into contact or antibodies passed to fetus
RBCs are broken down causing jaundice, anaemia, and death if severe
Mother’s antibodies linger after birth and destroy RBC of baby, causing an increase in bilirubin, a neurotoxic yellow waste product
Babies with high levels of bilirubin may need phototherapy (oxidises bilirubin and facilitates its removal by the liver) or a blood transfusion
More severe outcome: (haemolytic disease of newborn) more common in subsequent pregnancies
