Cardiovascular System: Heart Anatomy and Position

• Cardiovascular system consists of the heart and blood vessels.

Heart Anatomy and Position

• The heart is a muscular organ, about the size of a closed fist.
• It is located in the chest cavity.
• It's just posterior to the breastbone.
• It's positioned between the lungs and superior to the diaphragm.
• Extends from the 2nd to the 6th rib, corresponding to the T5-T8 vertebrae.
• Approximately two-thirds of the heart lies to the left of the sternum.
• Associated structures of the heart include the trachea and oesophagus.
• The heart is surrounded by a fluid-filled sac called the pericardium.
• The heart is responsible for pumping blood to all parts of the body

Heart Chambers

• The heart consists of four chambers
• Right Atrium
• Left Atrium
• Right ventricle
• Left ventricle

External Features of the Heart

• Apex: Formed by the left ventricle, round and pointed, directed downwards, forwards, and to the left.
• Base: Formed mainly by the left atrium, directed posteriorly and slightly superiorly.
• Three Surfaces Sternocostal diaphragmatic and left
• Four Borders: right, left, superior, and inferior.

Heart Coverings

• The heart is covered outside by a double-layered sac called the pericardium.
• The pericardium is composed of:
• Outer Fibrous Pericardium
• Inner Serous Pericardium
• Parietal Layer: Lines the internal surface of the fibrous pericardium.
• Visceral Layer: Lines the surface of the heart.
• The pericardial cavity is located between the parietal and visceral layers; it contains a small amount of fluid to prevent friction.
• The function of the pericardium:
• Protects the heart.
• Prevents overfilling of the heart with blood.

Heart Wall Layers

• Epicardium (Outer layer)
• Myocardium (Middle, muscular layer)
• Endocardium (Inner layer)

Heart Chambers

• Atria (superior chambers)
• Referred to as "receiving chambers" because they receive blood from veins.
• Ventricles (inferior chambers)
• Referred to as "pumping chambers"
  • Thick muscular walls to increase force of pumping
  • Separated by the interventricular septum.

Right Atrium

• Has a right auricle, which includes pectinate muscles.
• Features a depression called the fossa ovalis, which is remnant of the foramen ovale in the embryo and interatrial septum.
• Has four openings
• Superior vena cava
• Inferior vena cava
• Coronary sinus
• Anterior cardiac vein

Right Ventricle

• Located between the right atrium and right ventricle is the tricuspid valve
• Pumps blood through the pulmonary trunk into the lungs for oxygenation (deoxygenated blood).
• Includes papillary muscles
• Are located in the ventricles.
• They are attached to the cusps of the atrioventricular valves via the chordae tendineae. The papillary muscles contract to prevent inversion or prolapse of these valves during systole.
• The right side of the heart contains deoxygenated blood.

Left Atrium

• Receives four pulmonary veins (two from the right side and two from the left side) carrying oxygenated blood from the lungs.

Left Ventricle

• It has the largest chamber of the heart.
• Has a wall that is typically three times thicker than that of the right ventricle.
• Blood is transported from the left atrium to the left ventricle through the mitral or bicuspid valve.
• The left side of the heart contains oxygenated blood.
• Then, blood goes from the left ventricle through the aorta to all parts of the body.

Valves of the Heart

• Atrioventricular Valves:
• Right AV (Tricuspid): Located between the right atrium and right ventricle.
• Left AV (Bicuspid): Located between the left atrium and left ventricle.
• Semilunar Valves: Pulmonary Valve: Lies between the right ventricle and pulmonary trunk.
• Aortic Valve: Lies between the left ventricle and aorta.
• Function of valves: Prevent backflow of blood.

Circulation

• Systemic Circulation
• Pathway between the left ventricle and all parts of the body, then to the right atrium.
• Pulmonary Circulation
• The blood pathway between the right ventricle to the lungs and back to the left atrium.

Arterial Supply of the Heart

• Coronary arteries are the main arteries of the heart.
• There are two coronary arteries, originating from the ascending aorta (aortic sinus).
• Both coronary arteries run in the coronary sulcus.
• Right Coronary Artery
• Left Coronary Artery
• Function: Carry oxygenated blood and nutrients to the heart muscle.

Venous Drainage

• Most of the venous blood from the heart drains into the right atrium.
• Coronary Sinus
• Anterior Cardiac Veins
• Several Small Veins: Also known as the Besian veins.

Conducting System of the Heart

• The conducting system consists of:
• Sinoatrial Node (SA Node): Pacemaker of the heart, located in the right atrium near the opening of the superior vena cava.
• Atrioventricular Node (AV Node): Located 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

• The vascular system is composed of three types of blood vessels.
• Arteries
• Capillaries
• Veins

Blood Vessel Differences

• Arteries
• Carry blood from the heart to other organs.
• Carry oxygenated blood (except for the pulmonary artery).
• Have thick walls.
• Do not have valves.
• The Arteries and Arterioles: Take blood away from the heart
• 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.
• Capillaries: They have walls of one cell thick to allow for gas exchange and the passage of nutrients with tissue fluid.
• Veins
• Carry blood from other organs to the heart.
• Carry deoxygenated blood (except for the pulmonary vein).
• Have thin walls.
• Presence of valves.
• Venules drain blood from capillaries and then join to form veins that take blood to the heart.
• Veins have less smooth muscle and connective tissue than arteries.
• Veins often have valves that prevent the backward flow of blood when closed.
• They carry ~70% of the body's blood and act as a reservoir during hemorrhage

Aorta

• It has three parts
  • Ascending Aorta
  • Arch of the Aorta Descendin Thoracic
• Abdominal Aorta: Located in the abdomen.

Arch of the Aorta

• Three direct branches

  • Left Subclavian

• Left Common Carotid

• Brachiocephalic Trunk

  • Right Subclavian Artery
  • Right Common Carotid Artery

• The subclavian artery supplies toward 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.

• The common carotid artery supplies blood to the head and neck

• External Carotid Artery: Supplies blood to the neck.

• Internal Carotid Artery: Supplies blood to the brain. Abdominal Aorta: It divides into

• Right Common Iliac Artery

• Left Common Iliac Artery

Common Iliac Artery

• Divides into
  • External Iliac Artery
  • Internal Iliac Artery: Supplies blood to the pelvis and perineum.

External Iliac Artery

• It continues into the lower limb as
  • Femoral Artery: In the thigh.
• Popliteal Artery: At the popliteal fossa.
• Popliteal Artery: It divides in the leg.
  • Anterior Tibial Artery: Supplies the anterior leg.
  • Posterior Tibial Artery: Supplies the posterior and lateral leg.
• Dorsalis Pedis Artery: In the dorsum of the foot
• Medial and Lateral Plantar Artery: In the sole of the foot

Venous Drainage

• Venous drainage of the brain: Transverse sinus, straight sinus, superior and inferior sagittal sinuses
• Found in the neck: Internal jugular vein
• It consists of
• Veins of the Upper Limb: Cephalic (lateral) and basilic (medial) veins, the median cubital vein, axillary vein, and subclavian vein
• Superficial veins consist of
  • Cephalic vein
• Basilic vein
• Median vein
• Median cubital vein
• The subclavian vein connects with the internal jugular vein and drains into the brachiocephalic vein on both sides, then drains into the superior vena cava, and finally to the right atrium.
• The lower limb consists of
• Dorsal venous arch
• Anterior tibial vein
• Posterior tibial vein
• Popliteal vein: Found in the popliteal fossa Femoral vein: in the Thigh
• External iliac vein
• Internal iliac vein
• Common iliac vein Inferior vena cava
• Right atrium

Hepatic Portal Circulation

• It describes the flow of blood through the portal vein from the stomach, intestine, pancreas, and spleen to the liver for processing. Blood returns from the liver to the heart through the hepatic vessels.

Lymphatic System

• Functions of the Lymphatic System:
• Transports fluids from body tissues back to the bloodstream.
• Plays a crucial role in body defense and resistance to disease.
• Consists of three parts:
  • Lymph: Excess tissue fluid carried by lymphatic vessels. It's a pale white fluid with a similar composition to blood plasma but without erythrocytes.
• Lymphatic Vessels: Carry lymph towards the heart and never away No pump is involved; movement is facilitated by the "milking" action of muscles
• Lymphoid Tissues and Organs.
• Returns fluid to the circulatory veins near the heart

Lymphatic Ducts

• Thoracic Duct:
  • The largest and most important lymphatic channel of the body.
• Drains the lower extremities, pelvis, abdomen, left side of the thorax, the left upper extremity, and the left side of the head and neck.
• Continues superiorly to empty into the junction of the left subclavian and internal jugular veins.
• Cisterna Chyli:
  • A large midline lymphatic collecting structure located just inferior to the aortic hiatus of the diaphragm
  • Collects lymphatics from the lower extremities via left and right lateral branches and from the intestinal tract via an intestinal branch.
• Right Lymphatic Duct:
  • Drains the right side of the thorax, the right upper extremity, and the right side of the neck and head.
  • Empties into the right subclavian vein, internal jugular vein, or the union of the two.
• Lymph Nodes: Filter * via* lymph before it is returned to the blood
• Spleen: Filters out and destroys worn out blood cells, acts as a blood reservoir, and synthesizes antibodies.
• Thymus Gland: Located behind the sternum in the mediastinum. The capsule divides it into two lobes, it functions and to differentiate and mature T cells.
• Tonsils: Small masses of lymphoid tissue around the pharynx. Pharyngeal tonsils, palatine tonsils, lingual tonsils
• Peyer's Patches: Are found in the wall of the ileum and capture and destroy bacteria in the intestine.

Explore the anatomy and position of the human heart within the cardiovascular system. This includes its location in the chest cavity, its relation to the breastbone, lungs, and diaphragm, and the heart's four chambers and fluid-filled sac called the pericardium. Heart is responsible for pumping blood to all parts of the body