I. Blood vessels
a. Types
i. Arteries carry blood away from the heart
ii. Veins carry blood toward the heart
iii. Capillaries carry blood from the arterioles to the venules
b. Structure
i. Arteries
1. Tunica interna inner layer of endothelial cells
2. Tunica media smooth muscle, thick in arteries; important in blood pressure regulation
3. Tunica externa thin outer layer of elastic tissue
ii. Capillaries microscopic vessels
1. Only layer is the Tunica interna
iii. Veins
1. Tunica interna inner layer; valves prevent retrograde movement
2. Tunica media smooth muscle; thin in veins
3. Tunica externa heavy layer in many veins
c. Functions
i. Arteries distribution of nutrients, gasses, etc., with movement of blood under high pressure; assit in maintaining the arterial blood pressure
ii. Capillaries serve as exchange vessels for nutrients, wastes, and fluids
iii. Veins collect blood for return to the heart; low pressure vessels
II. Disorders of blood vessels
a. Disorders of arteries arteries must withstand high pressure and remain free of blockage
i. Arteriosclerosis hardening of arteries
1. Reduces flow of blood, possibly causing ischemia that may progress to necrosis
2. Atherosclerosis disorder in which lipids and other matter blocks arteries
3. May be corrected with vasodilators, angioplasty, or surgical replacement
ii. Aneurysm abnormal widening of arterial wall
1. Aneurysms promote formation of thrombi that may obstruct vital tissues
2. Aneurysms may burst, resulting in life-threatening hemorrhage
3. Cerebrovascular accident (CVA) or stroke ischemia of brain tissue caused by embolism or hemorrhage
b. Disorders of veins veins are low pressure vessels
i. Varicose veins (varices) enlarged veins in which blood pools
1. Hemorrhoids are varicose veins in the rectum
2. Treatments include supporting affected veins and surgical removal
ii. Thrombophlebitis vein inflammation (phlebitis) accompanied by clot (thrombus) formation; may result in fatal pulmonary embolism
III. Circulation of blood
a. Plan of circulation refers to the blood flow through the vessels arranged to form a circuit or circular pattern
b. Types of circulation
i. Systemic circulation
1. Carries blood throughout the body
2. Path goes from left ventricle through aorta, smaller arteries, arterioles, capillaries, venules, veins, venae cavae, to right atrium
ii. Pulmonary circulation
1. Carries blood to and from the lungs; arteries deliver oxygenated blood to the lungs for gas exchange
2. Path goes from right ventricle through pulmonary arteries, lungs, pulmonary veins, to left atrium
iii. Hepatic portal circulation
1. Unique blood route through the liver
2. Vein (hepatic portal vein) exists between two capillary beds
3. Assists with homeostasis of blood glucose levels
iv. Fetal circulation
1. Refers to circulation before birth
2. Modifications required for fetus to efficiently secure oxygen and nutrients from the maternal blood
3. Unique structures include the placenta, umbilical arteries and vein, ductus venosus, ductus arteriosus, and foramen ovale
IV. Blood pressure
a. Blood pressure is push or force of blood in the blood vessels
b. Highest in arteries, lowest in veins
c. Blood pressure gradient causes blood to circulate liquids can only flow from the area where pressure is higher to where it is lower.
d. Blood volume, heartbeat, and blood viscosity are main factors that produce blood pressure
e. Blood pressure varies within the normal range from time to time
f. Venous return of blood to the heart depends on five mechanisms: a strongly beating heart, an adequate arterial blood pressure, valves in the veins, the milking action of skeletal muscles as they contract, and changing pressure is the chest cavity caused by breathing.
V. Pulse
a. Definition alternate expansion and recoil of the blood vessel wall
b. Places you can count the pulse easily
i. Superficial temporal artery
ii. Facial artery
iii. Carotid artery
iv. Axillary artery
v. Brachial artery
vi. Radial artery
vii. Femoral artery
viii. Popliteal artery
ix. Dorsalis pedis
VI. Circulatory shock
a. Circulatory shock failure of the circulatory system to deliver oxygen to the tissues adequately, resulting in cell impairment
b. When the cause is known, shock can be classified as follows:
i. Cardiogenic shock caused by heart failure
ii. Hypovolemic shock caused by volume depletion that causes blood pressure (and blood flow) to drop
iii. Neurogenic shock caused by nerve condition that relaxes (dilates) blood vessels and thus reduces blood flow
iv. Anaphylactic shock caused by a type of severe allergic reaction characterized by blood vessel dilation
v. Septic shock results from complications of septicemia toxins in the blood resulting from infection
vi.