Blood Vessels

1
Blood Vessels

• The roads around the body

2
Some basics

• Closed circuit of tubes that carries blood from
  the heart to the cells and back again
• The force of the heart beat (blood pressure)
  pushes blood through the first two types of blood
  vessels. Muscle contraction brings it back.
• 3 main types
• Arteries carries blood away from heart
• Capillaries delivers nutrients and other
  materials to the cells
• Veins carries blood to the heart

3
Arteries

• Arteries have strong elastic walls adapted to
  high pressure
• 3 layers
• Inner layer ( tunica interna) made of endothelium
  like the heart smooth to help prevent blood
  clots
• Middle layer (tunica media) smooth muscle fibers
  and a thick layer of elastic connective tissue,
  nerves connect here to help control vasodilation
  and vasoconstriction
• Outer layer (tunica externa) thin, connective
  tissue, attached artery to surrounding area.
• Branch into thinner vessels called arterioles

4
(No Transcript)
5
Capillaries

• Start at the end of the smallest arterioles and
  end at the venules
• Are the smallest diameter blood vessels
• Composed of the endothelium that is the inner
  lining of the arterioles
• Are semipermeable due to small slits where the
  endothelial cells overlap
• Size of the opening depends on the tissue,
  muscles less, organs more
• Precapillary sphincters control the blood flow
  into the capillary.

6
(No Transcript)
7
Veins

• Veins carries blood back to the artria. Venules
  are little veins that connect the capillaries to
  the veins.
• 3 layer walls once again, but this time the
  middle layer is not as developed.
• Therefore less elastic and muscular
• Many veins have valves
• 2 leaflets that close if the blood moves away
  from the heart
• Typically found in the limbs

8
(No Transcript)
9
Neat trick veins...

• Veins are the blood reservoirs
• If the blood pressure drops significantly due to
  blood loss, the veins will constrict and return
  more blood to the heart.
• Help to maintain normal blood pressure even loss
  is 25 of blood volume

10
Blood Pressure

• The force the blood exerts on the inner walls of
  the blood vessels
• Typically referring to the pressure in the
  arteries (Arterial blood pressure)
• Maximum pressure during ventricular constriction
  is called Systolic pressure
• 120 is average
• Lowest pressure when the ventricles relax is the
  Diastolic pressure
• 80 is average

11
(No Transcript)
12
Two pathways

• Systemic circuit left ventricle to the rest of
  the body and then to the right atrium
• Pulmonary circuit Right ventricle to the lungs
  and then to the left atrium

13
(No Transcript)
14
Increased pressure

• Varicose veins veins with abnormal dilations
• Results from increased blood pressure in the
  saphenous veins (found in the legs) due to
  gravity.
• Hypertension persistently elevated arterial
  pressure
• Can contribute to atherosclerosis

15
(No Transcript)