Type of circulation
- Closed circulation
- Double circulation
- Systemic circulation
- Pulmonary circulation
Closed Circulation
Blood always remain within blood vessels
Double circulation
Blood travels through the heart on one complete circuit; Has deoxygenated and oxygenated flows : systemic + pulmonary
Systemic circulation
The oxygenated blood from the left ventricle is pumped to all body tissues. After exchange of substances occurs in body tissues, the blood becomes deoxygenated. This deoxygenated blood is returned to the right atrium.
Pulmonary Circulation
The deoxygenated blood from the right ventricle is pumped to the lungs. After exchanges of gases, the blood becomes oxygenated. This oxygenated blood is then returned to the left atrium of the heart.
Three main types of blood vessels
- Arteries
- Capillaries
- Veins
Wall of each artery consist of :
3 layers,
- Tunica Interna/ Tunica Intima / Inner endothelium
- Tunica Media
- Tunica Externa
Blood Plasma
- Pale yellow liquid
- Mostly water (90% water, 10% of plasma protein)
Plasma protein including antibodies (for immunity), fibrinogen (acts as clotting proteins) and albumin (for maintaining osmotic pressure of blood).
- Contains solutes ( glucose, amino acids, fatty acids, waste products - urea, gases - CO2 & O2)
Red Blood Cells are also called
Erythrocytes, which simply means ‘red cells’.
Red Blood Cells
- Contain haemoglobin : red pigment; 4 haem group; carries 8 oxygen molecules
- Transport oxygen to respiring tissues
- Produced in the bone marrow
- Short lifespan (for about 4 months) because lack of nucleus & other organelles needed to maintain the cells.
Structure of RBC
- Biconcave Disc Shape
- Small
- Contains Haemoglobin
- No nucleus, no mitochondria & no endoplasmic reticulum
How structure of RBC is adapted to function
- Biconcave disc shape
1. Increases SA : V ratio; oxygen can diffuse into & out of the cell rapidly
2. This shape enables RBCs to squeeze through the narrow lumen of blood capillaries - Small
1. 7 micrometre, can fit in capillaries, hb are close to membrane ; oxygen is brought as close as possible to the respiring cells - Contains Hb
1. Hb combines with oxygen to form oxyhaemoglobin readily at the lungs & releases oxygen readily at the respiring tissues. - No nucles/mitochondria/er
1. absence of these organelles means that there is more space for Hb thus increasing the oxygen carrying capacity of the cell.
2. Lack of mitochondria forces RBCs to respire anaerobically so they do not consume the oxygen that they are carrying.
Function of arteries
Carry blood away from the heart
Function of veins
Return blood back towards the heart
Function of capillaries
- Link arteries to veins
2. Site of exchange of substances between the blood and the cells.
Condition of blood in arteries, veins & capillaries
Arteries
- HIGH PRESSURE
- Blood flow very rapidly
- Blood flow in pulses
Veins
- LOWEST PRESSURE
- Blood flows slowly
- Blood does not flow in pulses
Capillaries
- Pressure in the blood is intermediate between thatbpf arteries & veins
- Blood flows more slowly
- Blood does not flow in pulses
Function of Tunica Interna/ Tunica Intima/ Inner Endothelium
Minimises friction with moving blood
Function of Tunica Media
Allows wall to stretch as pulses of blood surge through at high pressure
Valves in artery
Valves are absent except aorta & pulmonary artery
Valves in veins
Valves are present at intervals along the length of veins
Valves in capillaries
Valves are absent
White blood cells are also called
Leucocytes which simply means ‘white cells’
White blood cells
- Part of body immune system & play a role in protecting the body from disease-causing organisms.
- It has a short lifespan (of few days, 5-21 days) so they are constantly made in the bone marrow
Structure of WBC
- Have nucleus (but different shapes in different kinds of WBC)
- Larger than RBC (except lymphocytes)
- Spherical/irregular in shape
