General Anatomy of Cardiovascular System. By Dr. Suhail Ahmad.

Blood Vascular System. One of the major and more important systems of the body. Consists of heart and blood vessels

Blood Vascular System. An efficient mode of transport for oxygen, nutrients, and waste products to and from body tissues. Heart is the mechanical pump that propels the blood through the vessels. Heart and blood vessels form a closed-loop system.

Blood vessels A closed system of tubes in which the blood circulates. Arteries Veins capillaries Blood vessels are not rigid and immobile. Can pulsate and change shape in accordance with the body’s needs.

Blood Vessels: Did you know…. Humans have about 60,000 miles of vessels Vessels reach every millimeter of tissue We have at least two veins for every artery in our extremities We have 200 miles of vessels in every pound of adipose tissue

Blood vessels Naming: Often share names with either the body region they traverse or the bone next to them. Some are named for the structure they supply. Arteries and veins that travel together sometimes share the same name.

Three Main Classes of Blood Vessels Arteries convey blood away from the heart to the body tissues. Arteries branch, or bifurcate, into smaller and smaller vessels (arterioles) until they feed into the capillaries, where gas and nutrient exchange occurs. From the capillaries, veins return blood to the heart.

Three Main Classes of Blood Vessels Arteries become progressively smaller as they divide and get further from the heart. Veins become progressively larger as they merge and get closer to the heart.

Blood Vessel Tunics Tunica Intima Tunica Media innermost layer composed of: an endothelium (simple squamous epithelium) subendothelial layer (areolar CT) Tunica Media middle layer of the vessel wall circularly arranged smooth muscle cells

Blood Vessel Tunics Tunica Externa, or Tunica Adventitia outermost layer composed of: areolar connective tissue that contains elastic and collagen fibers helps anchor the vessel to other tissues Term adventitia is used to specify outer layer in blood vessels that are buried in CT Vasa vasorum : blood vessels that supply large blood vessels In the externa

Arteries In the systemic circulation, carry oxygenated blood to the body tissues. Pulmonary arteries carry deoxygenated blood to the lungs. Three basic types of arteries: elastic arteries, muscular arteries, and arterioles as an artery’s diameter decreases corresponding decrease in the amount of elastic fibers relative increase in the amount of smooth muscle

Arteries Types of arteries Elastic arteries Contain elastic fibers in the tunica media and interna Largest arteries

Arteries Elastic arteries: act as conduits 1-2.5 cm diameter Expand with surge of blood from heart Recoil and continue the propagation of blood Elastin is thick in media: dampens the surge of blood pressure Aorta and its branches

Arteries

Arteries Muscular arteries Little elasticity Abundant smooth muscle in tunica media

Arteries 2. Muscular arteries: act as distributing arteries Middle sized .3mm-1cm Changes diameter to differentially regulate flow to organs as needed Internal as well as external elastic lamina Most of what we see as “arteries” Tunica media larger in proportion to the lumen, thus “muscular”

Arteries

Arterioles < 1mm in diameter Endothelium and smooth muscle Metarterioles regulate flow of blood into capillaries Help regulate blood pressure

Capillaries Contain only the tunica intima. Allow gas and nutrient exchange between the blood and the body tissues to occur rapidly. Smallest blood vessels, connect arterioles to venules(5-10 micrometer). Are called the functional units of the cardiovascular system. A group of capillaries (10–100) functions together and forms a capillary bed.

The Three Basic Kinds of Capillaries Continuous capillaries the most common type Fenestrated capillaries Extensive molecular exchange(kidney, endocrine glands, intestines) Sinusoids, or discontinuous capillaries Liver, spleen

Veins Drain capillaries and return the blood to the heart. Walls are relatively thin and the vein lumen is larger. Systemic veins carry deoxygenated blood to the right atrium of the heart, while pulmonary veins carry oxygenated blood to the left atrium of the heart.

Veins Blood pressure is substantially reduced by the time blood reaches the veins. Hold about 60% of the body’s blood at rest. Veins function as blood reservoirs Venae comitantes Venous plexuses(Pampiniform)

From Venules to Veins Venules merge to form veins. Venule becomes a “vein” when its diameter is greater than 100 micrometers. Blood pressure in veins is too low to overcome the forces of gravity. Veins contain one-way numerous valves to prevent blood backflow in the veins. To assist in moving blood back to the heart.

Veins

From Venules to Veins Many deep veins pass between skeletal muscle groups. As the skeletal muscles contract, veins are squeezed to help pump the blood toward the heart. This process is called the skeletal muscle pump.

Small sized veins Medium sized veins Large veins

Artery/Vein differences Arteries (aa.) Veins (vv.) Direction of flow Blood Away from Heart Blood to Heart Pressure Higher Lower Walls THICKER: Tunica media thicker than tunica externa THINNER: Tunica externa thicker than tunica media Lumen Smaller Larger Valves No valves

Sympathetic innervation: Increase: vasoconstriction (narrowing of the blood vessel lumen) Decrease: vasodilation (widening of the blood vessel lumen)

Vascular Anastomoses Vessels unite and connect Anastomosis: Site where two or more vessels communicate to supply the same body region. Arterial Venous Arteriovenous

Vascular Anastomoses Arterial Anastomoses Communication between arteries Joints, Abdominal Organs, Brain alternate route Types of arterial anastomosis: Heterocladic & homocladic End to end, convergence, transverse

Vascular Anastomoses Functional end arteries(potential anastomosis) Have small anastomoses at capillary level E.g.: coronary arteries End arteries Arteries that do not form anastomoses Only one route E.g.: renal artery, splenic artery, central artery of retina.

Vascular Anastomoses Venous Anastomoses Communication between veins More common (eg) back of hand Veins tend to form many more anastomoses than do arteries.

Vascular Anastomoses Arterio-venous anatomoses: blood flows directly from arteries to veins without passing through capillary bed. Simple A-V anastomosis Between branches of small arteries and their corresponding veins(skin of nose, lips, external ear) Preferential thoroughfare channels Arteriolo-venular with capillaries as side branches(almost everywhere)

Complex A-V anastomosis(glomera) Coiled vessels Regulate temperature & regional blood flow Corium of hands, digital pads, nail beds

Circulatory systems of the body. Systemic circulation consists of the blood vessels that extend to and from the body tissues. Pulmonary circulation consists of the vessels that take the blood to the lungs for gas exchange. Coronary Circulation Blood flow to and from the myocardial capillaries Portal circulation

Portal System Special vascular circulation where blood goes through 2 capillary beds before returning to the heart . Venous portal systems Hepatic portal Hypothalamo- hypophyseal Arterial portal system Renal

Hepatic portal system Picks up digested nutrients from stomach & intestines and delivers them to liver for processing and storage Storage of nutrients Detoxification of toxins, drugs, etc. Two capillary beds Route: artery to capillaries of gut to hepatic portal vein to liver’s capillaries to hepatic vein to IVC

Renal portal system.

Arteriosclerosis Atherosclerosis Varicose veins