MMED1005 Lecture Notes - Lecture 22: Aorta, Polycythemia Vera, Fibroblast
7 Jun 2018
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Cardiovascular System III: blood and blood vessels
Learning objectives:
- Describe the function and components of the blood
- Describe the three layers that typically form the wall of a blood vessel
- Compare and contrast the structure and function of arteries, capillaries and veins
- Briefly describe the function of the lymphatic system
- Understand the role of the coronary arteries
Main points:
- Blood is made of plasma and formed elements
- All blood vessels have three tunics except for capillaries
- The arteries propel the blood forward, the arterioles are resistance vessels, the
capillaries are exchange vessels, and the veins are blood reservoirs
- The lymphatic system returns excess interstitial fluid to the blood
- The coronary circulation supplies oxygen and nutrients to the working heart
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mbl
Functions of blood:
- Distribution of:
o O2 and nutrients to body cells
o Metabolic wastes to the lungs and kidneys for elimination
o Hormones from endocrine organs to target organs
- Regulation of:
o Body temperature by absorbing and distributing heat
o Normal pH using buffers
o Adequate fluid volume in the circulatory system
- Protection against:
o Blood loss
▪ Plasma proteins and platelets initiate clot formation
o Infection
▪ Antibodies
▪ Complement proteins
▪ WBCs defend against foreign invaders
Blood characteristics and composition:
- Sticky, opaque fluid
- Colour scarlet to dark red
- pH ~7.4
- 38oC
- ~8% of body weight
- average volume 5-6L for males, 4-5L for females
- Blood is a fluid connective tissue composed of:
o Plasma (liquid component)
o Formed elements (not called cells because red blood cells are not functional
cells and platelets are just pieces of cells)
▪ Erythrocytes (red blood cells or RBCs)
▪ Leukocytes (white blood cells or WBCs)
▪ Platelets
If components of blood were separated through centrifuge:
- Erythrocytes settle at the bottom
- Buffy coat of leukocytes and platelets is very thin
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Plasma:
- 90% water
- Proteins:
o 60% albumin
o 35% globulin
o 4% fibrinogen
- nitrogenous by-products of metabolism:
o lactic acid, urea, creatinine
- nutrients:
o glucose, carbohydrates, amino acids
- electrolytes:
o Na+, K+, Ca2-, Cl-, HCO3-
- respiratory gases:
o O2 and CO2 (small amount is dissolved in the plasma)
- Hormones
Formed elements:
- Only WBCs are complete cells
- RBCs have no nuclei or organelles
- Platelets are cell fragments
- Most formed elements survive in the bloodstream for only a few days
- Most blood cells originate in bone marrow and do not divide
Erythrocytes (RBC):
- Biconcave discs, anucleate, no organelles, 8m in diameter
- contain the plasma membrane protein spectrin and other proteins
o provide flexibility to change shape as necessary (their shape also helps with
this. They need flexibility because capillaries are approx. the same diameter
as RBCs themselves)
- are the major factor contributing to blood viscosity
o change in percentage of RBCs would lead to change in viscosity of blood
- structural characteristics contribute to gas transport:
o biconcave shape – huge surface area relative to volume
o >97% haemoglobin (not counting water)
o no mitochondria (no organelles at all); ATP production is anaerobic
- main function: respiratory gas transport
- made in red bone marrow
Haemoglobin: (contained in RBCs)
- Protein globin: made up of two chains and two chains
- One heme pigment bonded to each globin chain (four total)
- Iron of each heme can bind one O2 moleculeeach Hb molecule can transport 4O2
- O2 and CO2:
o O2 loading in the lungs:
▪ Produces oxyhaemoglobin (bright ruby red)
o O2 unloading in the tissues:
▪ Producing deoxyhaemoglobin or reduced haemoglobin (dark red)
o CO2 loading in the tissues:
▪ Produces carbaminohaemoglobin (carries 20% of CO2 in the blood)
▪ Binds to amino acids of globin (NOT heme groupnot competing)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Describe the function and components of the blood. Describe the three layers that typically form the wall of a blood vessel. Compare and contrast the structure and function of arteries, capillaries and veins. Briefly describe the function of the lymphatic system. Understand the role of the coronary arteries. Blood is made of plasma and formed elements. All blood vessels have three tunics except for capillaries. The arteries propel the blood forward, the arterioles are resistance vessels, the capillaries are exchange vessels, and the veins are blood reservoirs. The lymphatic system returns excess interstitial fluid to the blood. The coronary circulation supplies oxygen and nutrients to the working heart mbl. Distribution of: o2 and nutrients to body cells, metabolic wastes to the lungs and kidneys for elimination, hormones from endocrine organs to target organs. Regulation of: body temperature by absorbing and distributing heat, normal ph using buffers, adequate fluid volume in the circulatory system.
