Cardiovascular System (cvs): Cardiovascular System (cvs)

Cardiovascular System (CVS):

• Cardiovascular System (CVS):

• Heart
• Blood vessels

• Lymphatic System:

Cardiac

• Cardiac

• (heart)

1. Transportation:

• 1. Transportation:

•  O2 & CO2.

•  digestion products.

•  wastes.

•  distribution of body fluids.

• 2. Regulation:

•  Hormonal.

•  Immune.

•  Protection.

•  Temperature.

■ Walls composed of 3 “tunicas:”

• ■ Walls composed of 3 “tunicas:”

• Tunica externa:
• Outer layer of connective tissue.
• Tunica media:
• Middle layer of smooth muscle.
• Tunica interna:
• Innermost simple squamous endothelium.
• Layer of elastin.

1. Aorta … (elastic recoil)

• 1. Aorta … (elastic recoil)

• ■ Numerous layers of elastin fibers b/w smooth ms.

• Expand when the pressure of the bl rises.
• Act as recoil system when ventricles relax.

• 2. Arteries … (muscular, low resistance vessels)

• Less elastic & have a thicker layer of smooth ms.
• Diameter changes slightly as BP raises & falls.

• 3. Arterioles … (high resistance vessels)

• Contain highest % smooth muscle.
• Expand less under pressure (less compliance).
• Called resistance vessels (greatest resistance to flow).

Capillaries … (exchange vessels)

• Capillaries … (exchange vessels)

• Smallest blood vessels.
• 1 endothelial cell thick.
• Provide direct access to cells.
• Permits exchange of nutrients & wastes.

• Venules

• Formed when capillaries unite.
• Very porous.

6. Veins … (capacitance vessels)

• 6. Veins … (capacitance vessels)

• ■ Contain little smooth muscle or elastin.

• Capacitance vessels (blood reservoirs).
• Contain 1-way valves that ensure blood flow to the heart.

• ■  2/3 of total blood volume is located in veins ( 70%).

■ Mean arterial pressure:

• ■ Mean arterial pressure:

• = 90 – 100 mmHg.

• ■ Mean venous pressure:

• Is only 2 mmHg (low).
• Due to:
• 1. Pressure drop b/w arteries & capillaries.
• 2. High venous compliance.
• N.B. Venous pressure is highest in venules (10 mmHg), & lowest at junction of venae cavae w Rt atrium (0 mmHg).

■ Distribution of ECF between plasma and interstitial compartments is in state of dynamic equilibrium.

• ■ Distribution of ECF between plasma and interstitial compartments is in state of dynamic equilibrium.

• Balance between tissue fluid and blood plasma.

• ■ Hydrostatic pressure:

• Exerted against the inner capillary wall.
• Promotes formation of tissue fluid.
• Net filtration pressure.

• ■ Colloid osmotic pressure:

• Exerted by plasma proteins.
• Promotes fluid reabsorption into circulatory system.

■ Hydrostatic pressure of blood capillaries minus the hydrostatic pressure in the interstitial fluid.

• ■ Hydrostatic pressure of blood capillaries minus the hydrostatic pressure in the interstitial fluid.

• Blood hydrostatic pressure (arteriolar pressure) = 37 mm Hg.
• Blood hydrostatic pressure (venular end) = 17 mm Hg.
• Interstitial hydrostatic pressure = 1 mm Hg.

■ Pressure exerted by plasma proteins or interstitial proteins.

• ■ Pressure exerted by plasma proteins or interstitial proteins.

• ■ Difference between plasma osmotic pressure and interstitial osmotic pressure is called oncotic pressure.

• Plasma osmotic pressure = 25 mm Hg.
• Interstitial osmotic pressure = 0 mm Hg.

■ Lymphatic vessels present b/w capillaries.

• ■ Lymphatic vessels present b/w capillaries.

• ■ 3 basic functions:

• Drain excess interstitial (tissue) fluid back to the bl, in order to maintain original bl volume.
• Transports absorbed fat from small intestine to the bl.
• Helps provide immunological defenses against pathogens.

■ Lymphatic capillaries:

• ■ Lymphatic capillaries:

• Closed-end tubules that form vast networks in intercellular spaces.

• ■ Lymph:

• Fluid that enters the lymphatic capillaries.
• Lymph carried from lymph capillaries, to lymph ducts, and then to lymph nodes.
• Lymph nodes filter the lymph before returning it to the veins.