Heart

ElasticArteries

MuscularArteries

Arterioles

Capillaries

Veins

1) Arteries (away)

2) Capillaries

3) Veins (toward)

Vessel Types:

Blood Vessel - Anatomy:

Venules

Structure and function - arterial system.

• 1/3 Conducting– The aorta & major branches

• Thickest• Largest• Elastic tubes

– Arteriosclerosis – Atherosclerosis (thickening) = turbulent flow– Balloon or burst (aneurysm)

Arterial System

• 2/3 Distributing – Delivery to organs – More active constriction – Less distensible

• Renal/urine - NFP

• 3/3 Arterioles• Flow determined by arteriole diameter• Constricted = bypassed• Dilated = local flow

Capillary Flow Control

• Precapillary sphincter– Cuff of smooth muscle fibers

» Open = flow

» Closed = shunt

Venous System.

– ↑ diameter– walls gradually ↔

• Venules→Veins– Larger lumens than corresponding

arteries» Reservoirs » 65% body’s blood supply

– VALVES for backflow» Most abundant in limbs - gravity

Vein Valve:

Blood Vessels:

Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Carry blood away from heart

• Thick-walled:

• Smooth muscle / elastic fibers

• Withstand high pressure

Arteries

Blood Vessels:

Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Control distribution of blood flow

• Smooth muscle expands / contracts

• Under hormone / NS control

Arterioles

Blood Vessels:

Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Nutrients / waste exchanged with cells:

• Vessel wall one-cell thick

• Blood flow very slow

• Materials exit / enter via diffusion

Capillaries

Blood Vessels:

Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Carry blood towards the heart

• Thin-walled; large diameter

• 65% blood volume in veins

Veins

Blood Vessels:

Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Carry blood towards the heart

• Thin-walled; large diameter

• 65% blood volume in veins

Veins

• Low pressure system

• Blood return to heart assisted by:

1) Valves

2) Skeletal muscle pumps

Blood Vessels• Major arteries.

• Aorta – Ascending, arch, thoracic, abdominal

• Brachiocephalic• Ext. & Int. carotid• Pulmonary• Axillary, brachial, radial, ulnar • Femoral, post. tibial

– Major veins• Superior VC• Ext. & int. jugular• Pulmonary• Brachiocephalics• Internal & external iliac• Femoral..

Heart - Flow Through Heart:

Myocardial Infarction::

• Prolonged blockage of coronary vessels

Circuitsof the

CirculatorySystem:

Major branches - coronary

Coronary Vessels

Step 1:

• Depolarization wave initiated by sinoatrial node (SA Node)

Sequence of ExcitationHeart Physiology:

• Impulse to atrioventricular node (AV Node) where briefly delayed

Step 2:

Sequence of ExcitationHeart Physiology:

Step 3:

• Impulse to atrioventricular bundle and into bundle branches

Step 4:

• Impulse spreads throughout ventricles along Purkinje fibers

IntrinsicConduction

System:

Controlof heart rate: