Download Circulatory System

Unit 4 Circulatory System
4.1 Circulatory System
Functions
a) Major:
o Moves nutrients from intestine (digestive system) to all body cells.
 The nutrients are absorbed into the blood vessels surrounding the intestine and
transported throughout the body.
 Arteries (red) bring the blood towards the organ and veins (blue) carry blood out of
the digestive system.
o Blood flowing through the lungs picks up oxygen which is transported to the cells.
 Blood vessels (capillaries) surround the alveoli.
o Carries wastes (ex. excess water) from body tissues for disposal.
 Carbon dioxide to the lungs (exhale).
 Blood to kidneys for filtering out water, ions, wastes, etc. (urine  then stored in
the urinary bladder to be excreted).
b) Minor:
o Regulates body temperature.
 When too hot, the heat can radiate out when the blood flows to our extremities (ex.
fingers, toes).
 When too cold, you can control how much blood goes to the extremities so that
you don’t lose too much heat (so that cold blood doesn’t go back to the heart and
cause problems).
 Sweating & shivering (contraction & relaxation of muscles to generate heat) is
other ways to regulate body temperature.
o Transports WBC’s to areas of the body where there are viruses or bacteria.
o Transports hormones, ions, glucose, water, other blood cells, etc.
Parts of the Circulatory System
Three major parts (of humans) include:
o Blood: a type of connective tissue that travels around the body. It is composed of:
 Red Blood Cells (RBC’s) (45%):
 Are most abundant and are bi-concave in shape. (lose nucleus at maturity to carry
more oxygen)
 Carry O2 on a protein called hemoglobin which makes them appear red.
 White Blood Cells (WBC’s) (<1%):
 Fight infection.

Make up less than 1% of blood but many different kinds (neutrophil, basophil,
eosinophil, monocyte & lymphocyte)
 Only blood cells with a nucleus.
 Platelets (<1%):
 Help with blood clotting to prevent bleeding.
 They are the smallest of blood cells and are actually fragments of cells.
 In a disorder called hemophilia, platelets fail to clot blood.
 Plasma (55%):
 The liquid that carries blood cells and makes up over half of blood’s volume.
o Heart
o Vessels
4.2 Blood Vessels
Artery
3 major layers:
o Lumen in centre (blood flow channel)
o Thick tunica media containing muscle
o Roughly circular in shape (due, in part, to the thick tunica
media  ring muscle)
o Carry oxygenated blood away from heart
o Coloured red in illustrations
o The squiggly inner line is called the internal elastic membrane
(part of the tunica intima)
o Note the circular muscle in the TM (tunica media)  arteries
can contract to push & pump blood in addition to the push
created by the heart
Vein
3 major layers:
o Lumen in centre (blood flow channel)
o Thin tunica media with little/no muscle
o Irregular shape (due to the thinner tunica media  not a lot
of muscle)
o Carry de-oxygenated blood towards heart
o Coloured blue in illustrations
o Note the irregular shape of the vein compared to the artery
o Thinner tunica media in vein, therefore veins cannot contract to push blood (instead
surrounding muscles do this)
o Veins are not always smaller than arteries
o Veins have valves (flaps of muscular tissue) that
help blood travel in one direction (back to heart) 
these valves exist every couple millimeters
o Muscles around vein contract, pushing blood
upwards
o When muscle relaxes, the valves close to prevent
blood from falling back down
o Veins have thinner walls than arteries 
contraction of surrounding muscles can squeeze
them
o Varicose veins: a disorder that tends to develop as people age.
 The valves get worn out (due to high blood pressure all the time) and let the
blood come back down  the thin-walled veins bulge out (visible in the skin)
Capillary
o 1 layer (very thin tunica intima)
o Smallest & thinnest blood vessel
o Gases & nutrients diffuse across the tunica intima
Villus Blood Supply
o Arteriole carries blood into villus
o Capillary network absorbs nutrients
o Venule carries blood out of villus
Comparison of Blood Vessels
Artery
Vein
3 layers
Thick walls
Muscular
Somewhat circular shape
3 layers
Thinner walls
Not muscular
Distorted shape
Carry oxygenated blood
Carry deoxygenated blood
No valves
Venous valves (ensure blood
flow back to heart)
Capillary
1 layer
Thinnest walls
Not muscular
Circular shape
Site of gas exchange to/from
cells
No valves
4.3 Mammalian Heart
1) Superior vena cava
o Very large vein
o Blood from upper body to right atrium
o Low O2/high CO2
2) Inferior vena cava
o Very large vein
o Blood from lower body to right atrium
o Low O2/high CO2
3) Right atrium
o Receives deoxygenated blood from vena cava (body)
4) & 5) Atrioventricular valves (A-V valve)
o Tricuspid (right) & bicuspid (left)
o Between atrium and ventricle
o Prevents backflow of blood when ventricle contracts (works only one-way)
o Have fibers
6) Right ventricle
o Receives blood from right atrium
o Low O2/high CO2
7) & 8) Pulmonary/Aortic semilunar valve
o Between ventricle and pulmonary trunk/arteries OR aorta
o Do not have fibers
9) Pulmonary artery
o Blood from right ventricle to lungs to get O2
10) Pulmonary vein
o Blood from lungs to left atrium
o High O2/low CO2
11) Left atrium
o Receives blood from lungs
o High O2/low CO2
12) Left ventricle
o Receives blood from left atrium
o High O2/low CO2
o Thicker walls (blood has to be pushed all the way up to aorta)
13) Aorta
o Largest artery
o Oxygenated blood from left ventricle to upper & lower body
14) Septum
o Separates left & right sides of heart to prevent mixing of oxygenated/deoxygenated
blood
15) Chordae tendineae
o Fibers that secure A-V valves
16) Myocardium
o Muscle of heart
17) Coronary vessels
o Blood vessels that serve the heart
4.4 Major Arteries of the Body
1. Pulmonary artery: blood out of heart
to lungs to pick up oxygen
(exception: the only artery carrying
deoxygenated blood)
2. Aorta: out of left ventricle
3. Bracheocephalic artery: a common
trunk before it splits & goes down to arm
and up to head (only on right side)
4. Carotid artery: the blood vessel that
does go up into the head
5. Subclavian artery: below a bone called
clavicle (collarbone) in the shoulder region
6. Brachial artery: blood from shoulder to
arm
7. Brachial artery (cont.): splits into 2
major arteries in around the elbow region
8. Radial artery: on the side of your
thumb (the artery you feel when you take
your pulse at wrist)
9. Ulnar artery
10. Descending aorta: part of aorta that
curves under the heart, travelling down
through thorax into abdomen
11. Renal artery: leads to one of the 2
kidneys for blood to be filtered
12. Gonadal artery: in the area where the gonads are located (ex. testes, ovaries)
13. Iliac artery: around the pelvic region (The aorta split into this on the left & right)
14. External iliac artery
15. Femoral artery: blood vessel that goes down into the leg (around the bond called femur)
16. Coronary artery: provide oxygen & nutrients to the heart muscle