Session 1 Flashcards
Intro to CVS, anatomy of the heart in situ and major blood vessels
Describe the factors influencing the exchange of substances between blood in capillaries and the surrounding tissue (5)
Area Diffusion path length Nature of molecule Size of pore Concentration gradient
What cells make up a capillary?
Single layer of endothelial cells surrounded by a basal lamina
How do larger/hydrophilic molecules diffuse out of the capillary?
Glucose, Amino acids and lactate diffuse through pores in the endothelium
what increases the rate of diffusion?
A larger concentration gradient
How will capillary concentration of a substance used by tissues be different to arterial concentration?
It will be lower, how much lower depends on the rate tissues use the substance and the rate of blood flow through the capillary bed
How is the concentration gradient maintained?
The rate of blood flow must be high enough to maintain a sufficient concentration
What is the rate of blood flow known as?
The perfusion rate
What blood flow does the brain need? /ml.min-1.g-1
High constant flow. 0.5ml.min-1.g-1
What blood flow does the heart need?
High flow, increasing during exercise. 0.9-3.6ml.min-1.g-1
What blood flow does the kidney need?
High constant flow 3.5ml.min-1.g-1
Any special circumstances of high blood flow to organs?
Blood flow to skeletal muscle is high during exercise and gut blood flow is high after a meal
What is the minimum flow /l.min-1 for a 70kg man
5l
What is the maximum flow /l.min-1 for a 70kg man
24.5l
What are the components of the cardiovascular system? (4)
Pump - the heart Distribution system - vessels & blood Exchange mechanisms - capillaries Flow controls - arterioles and pre-capillary sphincters
How is blood flow distributed across the body?
To regulate blood flow resistance is needed -> increasing resistance to normally easily perfused regions will increase flow to more difficult to perfuse regions. Arterioles are the resistance vessels
How is the total flow in the system able to change?
A temporary store of blood which can be returned to the heart at a different rate. The veins have thin walls that can distend or collapse -> store of blood (capacitance of the veins)
How much of blood is in the veins?
2/3rds
Where does blood flow fastest?
Where the total cross-sectional area is the least (therefore is slowest at capillaries)
Which major vessels leave the heart?
Aorta -brachiocephalic artery -left common carotid artery -left subclavian artery Pulmonary artery
What does the pulmonary trunk bifurcate into?
Right and left pulmonary arteries -> lungs
What does the abdominal aorta bifurcate into?
Left and right common iliac arteries (pelvis)
What is the systolic blood pressure in the aorta?
120mmHg
What is the diastolic blood pressure in the aorta?
70-80mmHg (the aortic semilunar valve closes, walls of aorta recoil, maintaining blood pressure)
Where is blood pressure most pulsatile?
In the arteries near the heart
What classifications of artery are there? (3)
Elastic conducting arteries Muscular distributing arteries Arterioles
What are the names of the layers of elastic arteries? (3)
Tunica intima (involved in atherosclerosis) -> endothelial cells with subendothelium of connective tissue + elastic lamina Tunica media -> 40-70 fenestrated elastic membranes Tunica adventitia -> thin layer of fibroelastic connective tissue
Features of muscular arteries?
Tunica intima -> normal Tunica media -> 40 layers of smooth muscle cells Tunica adventitia -> normal
- tunica intima 2. tunica media 3. tunica adventitia
What is special about the tunica adventitia (vasa vasorum)?
Many unmyelinated nerve endings for vasoconstriction (sympathetic). Noradrenaline released at nerve endings diffuse to smooth muscle cells in tunica media-> propagated by gap junctions
What happens to the number of smooth muscle layers in TM as arteries diminish?
decrease
Name 5 examples of end arteries
Coronary artery, Splenic artery, Renal artery, Central artery to retina, Labyrynthine artery of internal ear
What is an end artery?
A terminal artery supplying all or most of the blood to a body part without significant collateral circulation
What is an arteriole?
Arteries with a diameter less than 0.1mm
How many smooth muscle layers are in an ateriole tunica media?
1-3
What elastic lamina are present in arterioles?
Internal elastic lamina (IEL) only present in larger arterioles. No external elastic lamina.
What are metarterioles?
Arteries that supply blood to capillary beds. Smooth muscle layer is not continous -> each muscle forms a precapillary sphincter
What drains excess extracellular fluid?
Lymphatic capillaries
Where do lymphatic vessels drain tissue fluid?
junctions of internal jugular and subclavian veins
Diameter and length of a capillary?
7-10um diameter, 1mm long
What types of capillary are there? (3)
Continuous - most common Fenestrated - gut, endocrine glands and renal glomerulus - have many gaps (pores) Sinusoidal (discontinuous) - liver, spleen and bone marrow - have gaps allowing whole cells to move
What are pericytes?
These form a branching network on the outer surface of endothelium -> can divide into muscle cells or fibroblasts, during angiogenesis, tumour growth and wound healing
Why are postcapillary venules important in immunity?
These venules are the preferred location for emigration of leukocytes (more permeable than capillaries)
Which have larger diameters, veins or accompanying artery?
Veins
Describe the structure of cardiac muscle
Striations
Branching
Centrally positioned nuclei
Intercalated disks
Adherens-type junctions (anchorage)
Gap junctions (electrical coupling
T tubules are inline with Z band
