W9 | Cardiovascular System: The Heart, Blood System, & Circulation

1. Pulmonary Circulation

2. Systemic Circulation

Two side divisions of the Heart

Pulmonary Circulation

• Right side pumps blood to the lungs, where CO2 is exchanged for O2.

Systemic Circulation

• The left side pumps oxygenated blood to the rest of the body

Mediastinum

• Situated in the ____, between the lungs, in the thoracic cavity.

• Location of the heart

Apex

• Location of the heart

• Pointed end directed anteriorly, inferiorly, and to the left.

Base

• Flat part directed posteriorly and superiorly.

• Location of the heart

Heart

Functions:

• Generating blood pressure

• Routing blood

• Ensuring one-way flow

• Regulating blood supply

Size and Shape:

• Shaped like a blunt cone, roughly the size of a closed fist

• Average mass: 250g in females, 300g in males; larger in active adults, decreases after age 65.

Pericardium

• A double-layered sac surrounding the heart.

1. Fibrous Pericardium
   
   

2. Serous Pericardium

2 Parts of Pericardium

Fibrous Pericardium

• Outer tough layer preventing over-distension and anchoring the heart.

Serous Pericardium

Inner layer is divided into:

a. Parietal Pericardium

b. Visceral Pericardium (epicardium)

Parietal Pericardium

• Lines the fibrous pericardium

Visceral Pericardium (Epicardium)

• Covers the heart surface.

Pericardial Cavity

• Between the layers is a fluid that reduces friction during heart movement.

1. Epicardium

2. Myocardium

3. Endocardium

Three Layers of the Heart Wall

Epicardium

• Outer layer, same as visceral pericardium.

Myocardium

• Thick middle layer of cardiac muscle is responsible for contraction.

Endocardium

• Inner layer, smooth lining for chambers.

1. Right Atrium

2. Left Atrium

Two Atria of the Heart Chambers

Right Atrium

• Receives deoxygenated blood from the body.

Left Atrium

• Receives oxygenated blood from the lungs.

1. Right Ventricle

2. Left Ventricle

Two Ventricles of the Heart Chamber

Right Ventricle

• Pumps blood to the lungs via the pulmonary trunk.

Left Ventricle

• Pumps blood to the body via the aorta.

Atrioventricular (AV) Valves

• Prevent backflow from ventricles to atria.

1. Tricuspid Valve

2. Bicuspid (mitral) Valve

3. Chordae Tendineae & Papillary Muscles

Parts of Atrioventricular (AV) Valves

Tricuspid Valve

• Between the right atrium and ventricle.

Bicuspid (Mitral) Valve

• Between left atrium and ventricle.

Chordae Tendineae & Papillary Muscles

• Prevent valve inversion during contraction.

Semilunar Valve

• Prevents backflow from arteries into ventricles.

1. Pulmonary Valve

2. Aortic Valve

Parts of the Semilunar Valve

Pulmonary Valve

• Between right ventricle and pulmonary trunk

Aortic Valve

Between the left ventricle and the aorta.

Coronary Arteries

• Supply blood to the heart wall.

Left Coronary Artery

• Branches include the anterior interventricular, left marginal, and circumflex.

Right Coronary Artery

• Branches including right marginal and posterior interventricular arteries.

Coronary Veins

• Return blood to the right atrium via the coronary sinus.

Circulatory System

• Carries blood: blood vessels transport blood from the heart to body tissues and back.

1. Arteries

2. Capillaries

3. Veins

Types of Blood Vessels

Arteries

• Carry blood away from the heart

• Classified into elastic arteries, muscular arteries, and arterioles based on size and wall composition.

Capillaries

• The smallest blood vessels are where nutrient and gas exchange occurs.

• Can be continuous capillaries, fenestrated capillaries, or sinusoidal capillaries, depending on permeability

Veins

• Carry blood back to the heart.

• Have thinner walls than arteries and are classified as venules, small veins, medium veins, and large veins

1. Tunica intima

2. Tunica media

3. Tunica externa

Structure of Blood Vessel

Tunica Intima

• Innermost layer consisting of endothelium and a basement membrane.

Tunica Media

• Middle layer composed of smooth muscle responsible for vasoconstriction and vasodilation

Tunica Externa

• Outer connective tissue layer that provides structural support.

1. Portal Veins
   
   

2. Arteriovenous Anastomoses

Specialized Vessels

Portal Veins

• Unique veins that connect two capillary networks, such as the hepatic portal system.

Arteriovenous Anastomoses

• Direct connections between arterioles and veins, regulating temperature by controlling blood flow.

Blood Vessel Valves

• Valves in veins prevent backflow and ensure one-way blood toward the heart, especially in veins larger than 2mm in diameter.

Aorta

• The main artery from the heart.

Ascending Aorta

• Supplies blood to the heart via the right and left coronary arteries.

Aortic Arch

Branches into three major arteries:

1. Brachiocephalic Artery

2. Left Common Carotid Artery

3. Left Subclavian Artery

Descending Aorta

Supplies thoracic and abdominal organs and walls, dividing into the thoracic aorta and abdominal aorta.

Vertebral Arteries

• From the subclavian arteries, join to form the basilar artery, which supplies the brainstem and cerebellum.

Basilar Artery

• Supplies the brainstem and cerebellum

Circle of Willis

• A circular arrangement of arteries at the base of the brain, important for collateral blood flow.

Brachial Artery

• Divides into radial and ulnar arteries.

Radial& Ulnar Arteries

• Branch from the brachial artery and form the palmar arches in the hand.

Palmar Arches

• Formed by radial and ulnar arteries in the hand.

Thoracic Aorta

• Divides into visceral (supplying lungs, bronchi, esophagus) and parietal branches (supplying thoracic wall and diaphragm).

Abdominal Aorta

• Divides into unpaired visceral branches (e.g., celiac trunk, superior, and inferior mesenteric arteries) and paired branches (e.g., to kidneys and gonads).

Coronary Sinus

• This vein drains deoxygenated blood from the walls of the heart into the right atrium.

Superior Vena Cava

• It returns blood from the head, neck, thorax, and upper limbs to the right atrium.

Inferior Vena Cava

• It returns blood from the abdomen, pelvis, and lower limbs to the right atrium.

Cephalic Vein

• Drain the lateral side of the arm and empties into the axillary vein.

Basilic Vein

• Becomes the axillary vein as it passes through the axillary region.

Median Cubital Vein

• Connects the cephalic and basilic veins, typically used for drawing blood.

Deep Veins

• These follow the path of the arteries and are paired (one on each side of the artery).

Radial and Ulnar Veins

• These drain the forearm and empty into the brachial veins.

Brachial

• Drain into the axillary vein

Right and Left Brachiocephalic Veins

• These veins return blood from the thorax to the superior vena cava.

Azygos Vein

• Drains blood from the right posterior thoracic wall and empties into the superior vena cava.

Hemiazygos Veins

• These drain the left side of the thoracic wall and empty into the azygos vein.

Hepatic Portal System

• This system transports blood from the digestive organs to the liver for detoxification and nutrient processing.

Hepatic Portal Vein

• Formed by the union of the superior mesenteric vein (drains the small intestine) and the splenic vein (drains the spleen).

Superior Mesenteric Vein

• Drains the small intestine

Splenic Vein

• Drains the spleen.

Inferior Mesenteric Vein

• Drains part of the large intestine and joins the splenic vein.

Liver Sinusoidal Capillaries

• Blood from the digestive organs is processed in these capillaries before being collected by central veins and drained into the hepatic veins, which empty into the inferior vena cava.

Anterior and Posterior Tibial Veins

• Drain the lower leg and unite to form the popliteal vein, which becomes the femoral vein.

Fibular Veins

• Empty into the posterior tibial veins.

Great Saphenous Vein

• The longest vein in the body, it ascends the medial side of the leg and thigh to drain into the femoral vein.

Small Saphenous Vein

• Drains the lateral side of the foot and ascends the posterior leg, emptying into the popliteal vein.