Lecture 7 Flashcards
Why do we have a circulatory system?
An evolutionary consequence of an increase in size and complexity of a multicellular organism
Provides a steep concentration gradient from the blood to cells for nutrients, and from cells to blood for waste products
What is the primary function of the circulatory system?
Distribution of gases and molecules for nutrition, growth and repair
What are the secondary functions of the circulatory system?
Enables hormonal signalling
Dissipates heat
Mediates inflammatory and host defence responses
What are the three basic functional parts?
a pump = the heart
a fluid = the blood
a set of containers = the blood vessels (and lymphatic system)
What nervous system mediates the circulatory system?
ANS
What can affect the ANS and be affected by the ANS?
Sleep/wake Body position Rest/exercise Digestion Emotional stress
How is the systemic circuit aligned?
Parallel pathways are from left to right
Usually flows through a single capillary bed
Can have two capillary beds in series
Can have capillary beds in parallel and series
What are the two capillary beds in series?
kidneys, hepatic systems
What are parallel series of capillary beds?
spleen, intestines, and liver
How is the pulmonary circuit aligned?
Single pathway from right to left side of heart
What structure does the microcirculation have?
Can include capillaries and smaller venules and arterioles
What are the number of vessels in the aorta, capillaries and vena cava?
Aorta: 1
Capillaries: 40 billion
Vena cava: 1
What is the cross sectional area in the aorta, capillaries and vena cava?
Aorta: 4cm2
Capillaries: 2.8 * 10(-7) cm2
Vena cava: 6cm2
What is the aggregate cross sectional area in the aorta, capillaries and vena cava?
Aorta: 4
Capillaries: 2827
Vena cava: 6
What are the velocities in the aorta, capillaries and vena cava?
Aorta: 21 cm/s
Capillaries: 0.03 cm/s
Vena cava: 14 cm/s
What are the three layers of the blood vessel?
Tunica intima Tunica media Tunica externa (adventita)
What is the structure of the tunica intima?
Endothelial cells resting on a basement membrane
Have junctions of 10-15nm
BM: keeps capillaries more structured
Has valves to prevent backflow of blood (located over heart)
What is the structure of the tunica media?
Smooth muscle cells
Elastic fibers: elastin core covered by microfibrils
Varies composition based on vessel
Allow vessels to stretch and recoil (elastin)
What is the structure of the tunica externa?
Collagen fibers
Elastic fibers
Vasa varosum = blood supply for vessels
Nerves = sympathetic nerves
What are elastic fibers useful for in large arteries?
High compliance: walls stretch easily without tearing in response to an increase in pressure
Enables vessels: aorta to cope with peak ejection pressures
Recoil of elastic fibers forces blood to keep moving even when the ventricles are relaxed
What are smooth muscle useful for in medium-sized arteries?
Smooth muscle cells are arranged circumferentially
Capable of greater vasoconstriction and vasodilation to adjust the rate of blood flow
Vascular tone - state of partial contraction maintains vessel pressure and efficient flow
What are terminal regions of arterioles known as?
Metarterioles
What do precapillary sphincters do?
Monitor blood flow into the capillary
How do precapillary sphincters conduct their function?
Locals regulations by metabolites; low oxygen, high CO2, low pH=vasodilation
What are extrinsic regulations by the ANS?
Vasoconstriction: nonadrenaline activates alpha-1 adrenoceptors
Vasodilation: reduced release of noradrenaline, increase of calcium activates smooth muscle
What are the capillaries composed of?
Endothelial cells and basement membrane
Continuous capillaries have interendothelial junctions 10-15nm wide. What are their functions?
Keeps many substances in the blood;
Amino acids that act as neurotransmitters from causing adverse neuronal effects
Where is fenestra found in?
Where extensive molecular exchange occurs
What are places where extensive molecular exchange occurs?
Small intestine
Kidneys
endocrine glands
What is the function of fenestra?
Allows larger molecules to pass
Where are sinusoidal found in?
Liver and bone marrow
What is the structure of postcapillary venules?
porous
What do postcapillary venules do?
Participate in exchange sites for nutrients and waste
Are muscular venules more muscular than arterioles?
no
What do the thin walls in venules allow?
Expansion ;
excellent reservoirs for blood
What do large veins have to prevent back flow?
valves
What to defective, leaky valves lead to?
Varicose veins
Where are varicose veins prominent in?
Legs
What can varicose veins lead to?
Big bulges
Can cause pain, especially after standing
Deep vein thrombosis
Why do we need a lymphatic system?
More filtration than absorption occurs, leaving 3L of fluid and 150g of protein per day in the interstitial fluid
What is the amount of flow of fluid in protein in the lymphs?
Fluid: 2-4 L/day
Protein: 95-195 g/day
What is the amount of fluid and protein that enters the capillary from the lymphs?
Fluid: 16-18 L/day
Protein: 5g/day
What is the amount of fluid and protein that leaves the capillary into the lymphs?
Fluid: 20 L/day
Protein: 100-200 g/day
What are the three primary functions of the lymphatic system?
- Drains excess interstitial fluid, maintaining the circulating volume of blood
- Transports dietary lipids
- Carries out immune responses
Where are lymphocytes produced?
lymphatic valves
What are the three basic functional parts of the lymphatic system?
- lymph
- lymphatic vessels
- lymphatic tissue containing lymphocytes, found in a number of structures and organs
What is the main organ of the lymphatic system?
spleen
What is the structure of the lymphatic capillaries (initial lymphatics)?
More leaky than blood capillaries
Possess interendothelial junctions called Primary Lymph Valves
What is the structure of lymphatic vessels (collecting lymphatics)?
Endothelium plus sparse smooth muscle
Similar to small veins
Possess secondary lymph valves that restrict backflow
Uses hydrostatic pressure which is lower than interstitial fluid: opened interendothelial junctions
Vessels compressed by muscles for higher pressure and junctions are shut
Is there communication between the blood vessels and the lymphatic vessels?
yes
Where does lymph drain?
subclavian
What is a disorder in the lymphatic system?
Lymphoedema
What can lymphoedema lead to?
Ineffective drainage and excessive fluid buildup
What can ineffective drainage and excessive fluid buildup caused by lymphoedema present as?
Balloon like limbs
compression
tissue loses elasticity
