Cardiovascular System: Anatomy and Function

Cardiovascular System Overview

• The cardiovascular system is composed of the heart, which is cardio, and blood vessels, which are vascular.

Anatomy of the Heart

• The heart is a muscular organ, about the size of a closed fist.
• It is located in the chest cavity.
• The heart resides posterior to the breastbone.
• The heart positioned superior to the diaphragm and is situated between the lungs.
• Located between the 2nd and 6th ribs, it extends from the T5 to T8 vertebrae.
• Two-thirds of the heart lies left of the sternum.
• Structures associated with it include the trachea and oesophagus.
• The heart is enclosed in a fluid filled sac known as the pericardium.
• The primary function is to pump blood to all areas of the body.
• It consists of four chambers: the right atrium, left atrium, right ventricle, and left ventricle.

External Features of the Heart

• Apex
• Base
• Three surfaces: sternocostal, diaphragmatic, and left
• Four borders: right, left, superior, and inferior.
• The apex of the heart is formed by the left ventricle, shaped round and pointed.
• The apex directs downward, forward, and to the left.
• The base of the heart is mainly formed by the left atrium.
• The base is directed posteriorly and slightly superiorly.
• The sternocostal surface is formed anteriorly by the right and left ventricles, mainly the right one.
• The diaphragmatic surface is formed inferiorly by the right and left ventricles, mainly the left one.

Coverings of the Heart

• The heart is covered by a double-layered structure called the pericardium.
• The pericardium consists of two layers: an outer fibrous pericardium and an inner serous pericardium.
• The serous pericardium is divided into two layers: the parietal and the visceral.
• The parietal layer lines the internal surface of the fibrous pericardium.
• The visceral layer lines the surface of the heart.
• Between the parietal and visceral layers is the pericardial cavity, which contains a small amount of fluid to prevent friction.

Heart Wall Layers

• Epicardium (outer)
• Myocardium (middle muscular layer)
• Endocardium (inner)

Chambers of the Heart

• The two atria are superior chambers that receive blood from veins.
• The two ventricles are inferior "pumping chambers" with thick muscular walls.
• Ventricles are separated by the interventricular septum.

Right Atrium

• The right auricle contains pectinate muscles.
• It features a depression called the fossa ovalis, a remnant of the foramen ovale in the embryo.
• It includes part of the interatrial septum.
• Includes four openings: superior vena cava, inferior vena cava, coronary sinus, and anterior cardiac vein.

Right Ventricle

• The tricuspid valve is located between the right atrium and the right ventricle.
• The right ventricle pumps blood through the pulmonary trunk to the lungs for oxygenation.
• It carries deoxygenated blood.
• Includes papillary muscles
• The type of blood in the right side of the heart is deoxygenated.

Left Atrium

• This chamber receives oxygenated blood from the lungs via four pulmonary veins, two from the right side and two from the left side.

Left Ventricle

• It is the largest of the four chambers.
• Its walls are typically three times thicker than those of the right ventricle.
• Blood is transported from the left atrium to the left ventricle through either the mitral or bicuspid valve.
• The type of blood in the left side of the heart is oxygenated.
• Blood goes from the left ventricle through the aorta to the entire body

Heart Valves

• Atrioventricular valves include the right AV Tricuspid which lies between the right atrium and right ventricle, and the Left AV Bicuspid which lies between the left atrium and left ventricle
• Semilunar valves; the Pulmonary valve lies between the right ventricle and the pulmonary trunk, the Aortic valve lies between the left ventricle and aorta
• Valves prevent backflow of blood.

Circulation Overview

• Systemic circulation is the pathway between the left ventricle and all body parts, then to the right atrium.
• Pulmonary circulation describes the blood pathway, where blood leaves the right ventricle, goes to the lungs, and returns to the left atrium.

Arterial Supply of the Heart

• Supplying the heart, the coronary arteries are the main arteries.
• There are two branches from the ascending aorta (aortic sinus).
• Both coronary arteries run within the coronary sulcus.
• The right and left coronary arteries serve this system.
• Their function is to carry oxygenated blood and nutrients to the heart muscle.

Venous Drainage of the Heart

• Most venous blood from the heart drains into the right atrium.
• The coronary sinus is part of the drainage system.
• The anterior cardiac veins also contribute to the drainage.
• Several small veins called Thebesian veins exist.

Conducting System of the Heart

• Sinoatrial Node (SA Node)
  • Pacemaker of the heart in the right atrium near the superior vena cava
• Atrioventricular Node (AV Node)
  • In the left lower border of the right atrium
• Bundle of His (Atrioventricular Bundle)
  • Branches into Right and Left branches
• Purkinje Fibers
  • Smallest unit extends into the walls of the ventricles.

Vascular System Overview

• Consists of there types of blood vessels: arteries, capillaries, vains

Arteries

• Transport blood away from the heart to other organs.
• They carry oxygenated blood.
• Arteries have thick walls.
• Arteries do not have valves.
• The largest artery is the aorta.
• The middle layer of an artery wall consists of smooth muscle that can constrict to regulate blood flow and blood pressure.
• Arterioles can constrict or dilate, changing blood pressure.

Veins

• These carry blood from other organs back to the heart.
• They usually carry deoxygenated blood.
• Typically comprised of thinner walls.
• They contain valves.
• Venules drain blood from capillaries, then join to form veins that take blood to the heart.
• Veins have much less smooth muscle and connective tissue than arteries.
• Valves often exist to prevent the backward flow of blood when closed.
• They carry about 70% of the body's blood and act as a reservoir during hemorrhage.

Aorta

• Ascending aorta
• Arch of the aorta
• Descending thoracic
• In the abdomen called aortic

Aorta Arch Branches

• Left subclavian
• Left common carotid
• Brachiocephalic trunk divides into right subclavian artery and right common carotid artery.

Subclavian

• The subclavian artery supplies the upper limbs.
• In the axilla, it becomes the axillary artery.
• In the arm, it becomes the brachial artery.
• In the forearm, it divides into the radial and ulnar arteries.

Carotid Artery

• Supplies to the head and neck
• External carotid artery for supply to the neck
• Internal carotid artery for supply to the brain

Iliac Artery

• Right and left common iliac arteries.
• External iliac artery.
• Internal iliac artery (supplies pelvis and perineum).

Lower Limbs Arteries

• The external iliac artery continues into the lower limb.
• It becomes the femoral artery in the thigh.
• It continues as the popliteal artery at the popliteal fossa.
• The popliteal artery divides into the anterior tibial artery for the anterior leg and the posterior tibial artery for the posterior and lateral leg.
• In the dorsum of the foot, it becomes the dorsalis pedis artery.
• In the sole of the foot, it becomes the medial and lateral plantar artery.

Venous Drainage

• In the brain, found sinuses: transverse sinus, straight sinus, superior, and inferior sagittal sinus.
• In the neck, found internal jugular vein.
• Cephalic (lateral) and basilic (medial), median cubital vein, axillary, then subclavian vein.
• In the brain, found sinuses: Transeverse sinus, straight sinus, superior and inferior sagittal sinus
• In the neck, found internal jugular vein

Veins of the Upper Limb

• Cephalic (lateral) and basilic (medial), median cubital vein, axillary, then subclavian vein

Subclavian Veins

• Connects with internal jugular vein drain in brachiocephalic vein in both side then drain in superior vena cava then to right atrium. In lower limb dorsal venous arch, anterior tibial vein, posterior tibial vein in the leg:
• Popliteal Vein in the popliteal fossa.
• Found femoral vein in the thigh then external iliac vein and internal iliac vein, common iliac vein then inferior vena cava then to the right atrium.

Hepatic Portal Circulation

• The flow of blood through the portal vein from the stomach, intestine, pancreas, and spleen to liver
• From the liver through the hepatic portal vein for processing and from the liver to the heart through the hepatic vessels

Lymphatic System Functions

• Transports fluids from body tissues back to bloodstream.
• Plays essential roles in body defense and resistance to disease.
• It consists of three parts: lymph, lymphatic vessels, and lymphoid tissues and organs.

Lymphatic Characteristics

• Lymph
  • Excess tissue fluid carried by lymphatic vessels
  • Pale white fluid, similar composition to blood plasma, but with no erythrocyte
• Lymphatic vessels:
  • Carry lymph toward the heart, never away
  • No pump, moved by "milking” action of muscles

Lymphatic Vessels

• Fluid leaks here from the body tissue
• Lymphatic vessels collect fluid from lymph capillaries
• Lymphatic vessels carry lymph away from lymph nodes
• Returns fluid to circulatory veins near the heart

Lymphatic Ducts

• The thoracic duct is the largest and most important lymphatic channel of the body.
• The thoracic duct drains the lower extremities, pelvis, abdomen, left side of the thorax, left upper extremity, and left side of the head and neck.
• The thoracic duct continues superiorly to empty into the junction of the left subclavian and internal jugular veins.
• The cisterna chyli is a large midline lymphatic collecting structure located just inferior to the aortic hiatus of the diaphragm.
• The cisterna chyli collects lymphatics from the lower extremities via left and right lateral branches and from the intestinal tract via an intestinal branch.
• The right lymphatic duct drains the right side of the thorax, the right upper extremity, and the right side of the neck and head.
• It usually empties into the right subclavian vein, the internal jugular vein, or the union of the two.

Lymph Nodes

• Lymph nodes filter lymph before it is returned to the blood.

Spleen

• Filters out and destroys worn-out blood cells.
• Acts as a blood reservoir, while synthesizing antibodies.

Thymus Gland

• Location: behind the sternum in the mediastinum
• The capsule divide it into two lobes
• Function: different and maturation of T cells

Tonsils

• Small masses of lymphoid tissue around the pharynx
  • Pharyngeal tonsil
  • Palatine tonsils
  • Lingual tonsils

Peyer's Patches

• Found in the wall of the ileum
• Capture and destroy bacteria in the intestine

Overview of the cardiovascular system, including the anatomy of the heart, its location in the chest cavity, and its primary function of pumping blood throughout the body. It consists of four chambers: the right atrium, left atrium, right ventricle, and left ventricle.