Cardiovascular System

• The cardiovascular system consists of the heart and blood vessels.

Cardiovascular System Function

• Transports oxygen and nutrients to tissues
• Eliminates metabolic waste products

Lymphatic Vessels Function

• Act as drainage, moving lymph from cellular interstice to the cranial vena cava

Blood Vessel Function

• Transport blood which carries oxygen and essential substances to tissues

Blood's Role in Metabolic Waste

• Transports waste to the liver, kidneys, and lungs for breakdown and excretion

Blood Volume in Mammals

• Accounts for 6-8% of body weight in domestic mammals

Heart's Role

• Pumps blood throughout life

Types of Circulation in Mammals

• Systemic (major)
• Pulmonary (minor)

Circulation Intersection

• Occurs in the heart

Systemic Circulation Start

• Initiates in the left atrium

Post Left Ventricle

• During systole, blood is propelled into the aorta

Blood Flow to Tissues/Organs

• Flows through arteries and arterioles to capillaries

Systemic Circulation Venous Return

• From the head, neck, and thoracic limbs via the cranial vena cava
• From the trunk, pelvis, and pelvic limbs via the caudal vena cava

Vena Cava Termination

• Both venae cavae empty into the right atrium

Blood Flow from Abdominal Organs to Liver

• Through the portal vein to the hepatic capillary bed

Post Liver Blood Flow

• Flows into the caudal vena cava

Pulmonary Circulation Start

• Begins in the right atrium

Blood Flow from Right Atrium

• Flows into the right ventricle

Pulmonary Circulation During Contraction

• The right ventricle pumps blood into the pulmonary trunk

Blood Transport to Lungs

• Via the pulmonary trunk and pulmonary arteries

Gas Exchange Location

• Occurs in the pulmonary capillary beds

Oxygenated Blood Return

• Returns to the heart through the pulmonary veins

Pulmonary Circulation End

• Oxygenated blood empties into the left atrium

Heart Structure

• Is a four-chambered hollow organ

Heart Tissue

• Composed of striated involuntary muscle fibers known as myocardium

Heart Covering

• Pericardium

Heart Location

• In the thoracic cavity, within the middle mediastinum (cardiac mediastinum)

Pericardium

• Is a fibroserous membrane covering the heart

Pericardial Cavity

• Is formed within the pericardium

Pericardial Fluid

• Found within the pericardial cavity

Pericardium Layers

• Fibrous pericardium
• Serous pericardium (visceral and parietal layers)

Visceral Pericardium Layer

• Forms the epicardium

Epicardium Covering

• Covers cardiac muscle, coronary vessels, surface fat, atria, and the base of main blood vessels

Transverse Pericardial Sinus

• Is an opening at the heart base connecting the right and left sides of the pericardial cavity

Oblique Pericardial Sinus

• Is an invagination formed by serous pericardium reflection between the heart's major veins

Parietal Pericardium Connection

• Is connected to the fibrous pericardium

Fibrous Pericardium Composition

• Composed of a meshwork of interwoven collagen fibers

Fibrous Pericardium Connection

• Continuous with the outer layers of the major arteries and veins

Ventral Fibrous Pericardium

• In dogs, it continues as the sternopericardial ligament, which anchors to the sternum
• In herbivores, it continues as the phrenicopericardial ligament, attaching to the diaphragm

External Covering of Fibrous Pericardium

• Covered by the pericardial pleura (mediastinal pleura)

Heart Location

• Located in the thoracic cavity within the middle mediastinum, towards the left of the median plane

Heart Location Between Ribs

• Situated between the 3rd and 6th ribs in most domestic mammals, extending to the 7th rib in carnivores

Heart Shape

• Conical, with the base oriented upwards and the apex towards the sternum

Cardiac Axis Inclination

• In dogs and cats, it's inclined with the base craniodorsal and the apex caudoventral

Heart Base Location

• Located in the middle of the thorax, surrounded by the lungs

Heart Location Between Intercostal Spaces

• In dogs, between the 4th and 6th intercostal spaces, towards the left, between the sternum and costal cartilage

Heart Location in Horses

• At the height of the elbow, between the 3rd and 5th intercostal spaces

Heart Location in Cattle

• On both sides of the thoracic wall, between the 3rd and 4th intercostal spaces

Heart Formation

• Formed into an arterial (left) and a venous (right) half

Heart Chamber Composition

• Each half contains an atrium and a ventricle

Heart Chamber Separation

• Divided by septa

Atrial Location

• Located at the heart base

Structures Surrounding Atria

• Auricles, which encircle the initial parts of the aorta and pulmonary trunk

Heart Shape Towards the Apex

• Is conical and flattened on each side

Heart Borders

• Cranial border is related to the thymus in young animals
• Caudal border rests on the diaphragm

Heart Surfaces

• Right surface features the coronary groove and the subsinual interventricular groove
• Left surface features the coronary groove and the paraconal interventricular groove

Grooves on Heart Exterior

• Grooves mark the position of the interventricular septum

Left Side Structures

• Both atria, pulmonary trunk and aorta

Right Side Structures

• Major veins and atria

Heart Border with Greatest Resistance

• Caudal border

Cranial Border Less Resistant

• Due to withstanding less pressure and being more distensible

Ventricle with Thinnest Wall

• Right ventricle

Structures Covering Coronary Vessels

• Covered by subepicardial fat within the coronary groove

Coronary Groove Indicator

• Indicates the position of the cardiac valves (valve plane).

Right Atrium Drainage

• Drains both vena cavae and the coronary sinus

Interatrial Septum Feature

• Near the caudal vena cava opening, you'll find the fossa ovalis (foramen ovale)

Intervenous Tubercle

• Is a prominent muscle bridge between the vena cava openings

Internal Surface of Right Atrium

• Displays pectinate muscles arranged irregularly towards the interior

Left Atrium Blood

• Receives oxygen-rich blood from the pulmonary veins

Left & Right Atria Similarities

• Similar in structure
• Differ as the left atrium receives oxygenated blood

Right Ventricle Structure

• Is crescent shaped

Right Ventricle Location

• Cranial to the left ventricle

Right Ventricle Extent

• Does not reach the heart apex

Right Ventricle Blood Intake

• Blood is received from the right atrium through the atrioventricular orifice

Right Ventricle Blood Output

• Pumps blood toward the pulmonary trunk and lungs

Separation of Conus Arteriosus

• Is separated from the main chamber of the right ventricle by the supraventricular crest

Supraventricular Crest Structure

• Is a muscular bridge projecting ventrally from the cranial region of the roof of the right ventricle

Atrioventricular Valve Location

• Located in the atrioventricular orifice

Atrioventricular Valve Cusps

• Has three cusps

Atrioventricular Valve Cusp Attachment

• Cusps attach to the cardiac skeleton and are tethered to papillary muscles by chordae tendineae

Papillary Muscle Function

• Maintain the atrioventricular valves in place via chordae tendineae

Largest Papillary Muscle

• Is the major papillary muscle located on the ventricle wall

Structures Crossing the Right Ventricle

• One or more trabeculae carneae extending from the interventricular septum to the ventricle wall

Trabeculae Carneae Function

• Aid in blood distribution and improve ventricular contraction efficiency

Location of Muscular Bundles

• Found in the lower section of the right ventricle

Muscular Bundles Function

• Reduce blood flow turbulence inside the ventricle

Pulmonary Valve Structure

• Exhibits a slight thickening along the free margin of its cusps, along with a small nodule at their midpoint

Pulmonary Nodule Role

• Aided in rapid valve closure

Left Ventricle Connection

• Connects with the left atrium through the left atrioventricular orifice

Left Ventricle Wall vs Right Ventricle Wall

• The left ventricle wall is thicker

Volume Variance

• Both left and right ventricles feature comparable volumes

Left Atrioventricular Valve Cusps

• Contains two cusps

Aortic Valve Position

• Centrally located in relation to the entire heart

Aortic Valve Characteristics

• Presents a slight thickening along its free border and a centered nodule

Comparison of Aortic Valve Nodule

• The aortic valve's nodule is more prominent than those of the semilunar valves

Aortic Bulb

• Is an expansion above the aortic valves

Aortic Bulb Formation

• Formed from three aortic sinuses

Origin of Coronary Arteries

• Originate from the right and left aortic sinuses

Endocardium

• Is a flat, thin layer covering the heart's inner space

Endocardium Covering

• It also covers cardiac valves and is continuous with the intima of blood vessels

Myocardium

• Is the heart's muscular layer, composed of involuntary striated muscle

Arrangement of Myocardial Cells

• Are connected via intercalated discs, forming a continuous network

Location of Myocardial Cell Nuclei

• Located in the central area of cells

Non-Fatigue of Myocardial Cells

• Governed by the "all or nothing" principle

Myocardial Arrangement in Atria

• Arranged in an arch form

Myocardial Organization at Venous Openings

• Arranged circularly

Myocardial Arrangement in Cardiac Chambers

• The myocardium is formed by three layers:
  • External muscle layer: Longitudinal.
  • Middle muscle layer: Annular.
  • Internal muscle layer: Longitudinal.

Orientation of Muscle Bundles

• Muscle bundles in the external longitudinal layer of the myocardium in both ventricular chambers run spirally towards the left
• In the ventral direction toward the apex of the heart, they ascend on the opposite side

Muscle Bundles Reaching the Heart Apex

• Some muscle bundles separate and form the innermost longitudinal layer

Termination of Muscle Strands

• Some strands end in the papillary muscles

Dominance of Annular Layer

• Predominates in the left ventricle and at the outflow regions

Muscle Layer Development

• Muscle development depends on functional requirements
• Atrial walls are thinner and the right ventricle thinner than the left

Structures Around Aorta, etc.

• The aorta, pulmonary trunk, and atrioventricular openings are surrounded by collagen fiber bundles
• They form rings constituting the cardiac skeleton (connective tissue)

Ossification in Bovine

• Bony deposits called ossa cordis are present

Ring Presence in Cats

• Cartilaginous

Function of Cardiac Skeleton

• Separates atrial musculature from ventricular musculature

Epicardium External Covering

• Covers the external wall of the heart

Tissue Forming Epicardium

• Formed by a thin, flat layer of outer fibrous tissue and serous tissue

Layers of Heart Wall (Outside to Inside)

• Epicardium
• Myocardium
• Endocardium

Origin of Left Coronary Artery

• Originates in the left sinus of the aortic bulb

Course of Left Coronary Artery

• Courses between the left auricle and pulmonary trunk
• Reaches the coronary groove

Branches of Left Coronary Artery

• Divides into an ascending branch and a branch that travels along the coronary groove

Function of Descending Branch

• The descending branch, known as the paraconal interventricular branch, travels down the interventricular groove
• Irrigates the left heart wall and a large portion of the interventricular septum

Circumflex Artery

• Arises from the left coronary artery
• Encircles the heart caudally and ends in the right interventricular grooves or subsinual regions
• Extends towards the heart apex

Origin of Right Coronary Artery

• Originates from the cranial sinus of the aortic bulb

Course of Right Coronary Artery

• Courses between the right auricle and pulmonary trunk
• Extends to the coronary groove and terminates in the interventricular groove

Characteristics of Coronary Arteries

• Terminal arteries; their larger branches do not form interconnections

Great Cardiac Vein

• The vein where the heart veins converge, located near the left coronary artery

Great Cardiac Vein Blood Source

• Collects blood from the middle portion of the heart, ascending through the right interventricular sulcus

Smallest Vein Drainage

• Empties directly into the cardiac chamber

Sinoatrial Node Location

• Located in the right atrium

Function of Sinoatrial Node

• Functions as the heart's »pacemaker«, generating electrical impulses rhythmically
• Sends these impulses to neighboring myocardial cells, beginning cardiac contraction in the atria

Post Nodal Electrical Impulses

• Three bundles of fibers extend from the node, coursing through the atrial myocardium

Location of Atrioventricular Node

• Located at the junction of the right atrium and ventricle

Atrioventricular Node Function

• Receives electrical impulses from the sinoatrial node through fiber bundles
• Transmits them to the right ventricle

Myocardial Cell Characteristics

• Exhibit membrane instability, allowing rapid electrical current generation/transmission throughout the myocardium

Coordination of Contraction

• Is coordinated via the conduction system, ensuring effective blood pumping

Origin Of His Bundle

• Originates from the atrioventricular node
• Passes through the atrioventricular septum to the interventricular septum

Division of His Bundle

• Divides into two branches that descend through the interventricular septum towards the heart apex

Left Bundle Branch Division

• Subdivides into two additional branches, anterior and posterior

Why Left Branch Divides

• Ensures all myocardial cells are stimulated

Purkinje Fiber Function

• Transfers electrical impulses to all myocardial cells
• Ensure coordinated contraction

Origin of Purkinje Fibers

• Originate from the ventricular branches of the His bundle

Nervous Control of Heart

• Controlled by the autonomic nervous system

Nerve Fiber Types

• Sympathetic fibers
• Parasympathetic fibers (vagus nerves)

Sympathetic Stimulation Effect

• Increases the heart rate and contraction strength

Why Sympathetic System Increases Activity

• Responds to stressful conditions or high energy demands
• Is akin to exercise or a fight-or-flight response

Parasympathetic Stimulation Effect

• Decreases heart rate and contraction strength

Parasympathetic Nerves

• Vagus nerves (one right and one left)

Central Nervous System Heart Adaption

• Modifies sympathetic and parasympathetic stimulation as needed

Blood Vessel Network Name

• Cardiovascular system

Main Vessel Types

• Arteries, arterioles, metaarterioles, capillaries, venules, and veins

Arterial Function

• To transport blood from the heart toward tissues

Arteriole Origin

• Arise from arterial branches

Metaarteriole Formation

• Formed by the diameter reduction of arterioles.

Capillary Function

• Enabling substance exchange with tissues

Capillary Structure

• Thin vessels lacking a muscle layer, formed by a sole endothelial layer supported by a basement membrane

Venules & Origin

• Vessels with a larger diameter than capillaries, formed via the reunion of the latter

Vein Formation

• Formed from the confluence of the venules.

Vein Function

• Transport of blood towards the heart

Vessel Wall Layer

• Intima (internal)
• Media
• Adventitia (external)

Lumen

• Interior space through which blood flows

Inner Layer Name

• Tunica intima, also known as endothelium

Intima Continuity

• Continuous with endocardium

Intima Composition

• Tissue that is in contact with blood

Intima Tissue Type

• simple squamous epithelium

Intima Support

• Supported on a thin basal lamina

Tissue Beneath Basal Lamina

• Fine connective tissue called the subendothelium

Layers of Subendothelium

• Contains substantial elastin fibers which impart elasticity to blood vessels

Protein in Subendothelium

• Elastin
• Offers elasticity and enables blood volume adaptation

Capillary Endothelial Cells

• Are slightly separated to allow small intercellular gaps through which leukocytes can pass
• Allows due to their ability to change shape

Intima Layer Facilitation

• Intima facilitates leukocyte mobility.

Media Composition

• Is composed of smooth muscle tissue encircled by a coating of elastic connective tissue.

Media Contraction Regulation

• Through the autonomic nervous system

Media Main Function

• Sustains adequate vessel diameter in response to the needs of a bodily region

Adventitia Tissue

• Connective tissue with abundant elastin and collagen fibers.

Adventitia's Function

• Offers resistance to blood vessels and isolates them from other tissues

Special Structure in Veins

• Valves.

Valves are Formed By

• Endothelial expansions located towards the vessel lumen

Valves in Vein Function

• Stops the backflow of venous blood
• Aids blood flow

Minior/Pulmonary Circulation Start

• Starts in the right ventricle

Primary Minior Circulation Function

• Transporting deoxygenated blood to the lungs to convert CO2 to 02

Vessels that Carry Deoxygenated Blood

• Upper/Inferior vena cava

Deoxygenated Blood Entry Point

• Right auricle

Deoxygenated Blood Valve

• Tricuspid valve

Artery that Discharges Blood

• Pulmonary artery

How Pulmonary Arteries Divide

• Into right and left which branch out into capillaries

Where Does the Exchange of Gas Occur

• At the level of the pulmonary alveoli vessels

C02/02 Exchange

• Red cells release CO2 and grab 02

How Does Oxygenated Blood go Back to the Heart?

• Through four pulmonary veins

Oxygenated Blood Entry Point in the Heart

• Enters the left Auricle

Where Does the Minor Circulation End?

• Terminates in the left auricle, completing the circuit

The Sistemic/Superior Circulation

• Begins in the left ventricle

Most Important Function of the Greater Blood Flow

• Moving oxygenated blood, collects deoxygenated blood

What Blood Vessel Does the Blood Exit Through?

• Through the Aorta

The first segment of the Aorta

• Ascendent Aorta

What is the Name of of the Curvy Part of the Way

• Through the curvy path of the Aorta

Why is the Part Called that that Goes to the Abdomen?

• Called Descending

Which are the Two Pieces of the of Aorta Descendent?

• Toracic Aorta and Abdominal Aorta

What vertebral level is the abdominal aorta divided at?

• Vertebra L4.

What arteries does the aorta divide into at level L4?

• Into right and left common iliac arteries.

How are the common iliac arteries divided?

• Into the external and internal iliac arteries.

What terminal artery arises at the bifurcation of the aorta?

• The medial sacral artery.

What structures does the aorta irrigate from its origin to its end in the abdomen?

• The neck, skull, upper limbs, thoracic organs, abdominal organs, and lower limbs.

What are the main divisions of the aorta?

• Ascending aorta, aortic arch, thoracic aorta, and abdominal aorta.

What are the main branches of the aortic arch?

• Brachiocephalic trunk, left common carotid artery, and left subclavian artery.

What arteries irrigate the brain?

• The internal carotid arteries and vertebral arteries.

What arteries irrigate the upper limbs?

• The subclavian arteries, which give rise to the axillary, brachial, radial, and cubital arteries.

What are the main arteries that irrigate the abdominal organs?

• Celiac trunk, superior mesenteric artery, and inferior mesenteric artery.

What arteries irrigate the lower limbs?

• The external iliac arteries, which continue as femoral arteries and then divide into popliteal, tibial, and peroneal arteries.

What veins reach the right atrium?

• The superior vena cava and the inferior vena cava.

Where does the superior vena cava collect blood from?

• From the upper limbs, thorax, neck, skull, and face.

Where does the inferior vena cava collect blood from?

• From the abdomen and lower limbs.

What veins drain into the inferior vena cava?

• The splenic, renal, superior mesenteric, and inferior mesenteric veins, among others.

What function does the hepatic portal system have?

• To transport nutrient-rich blood from the digestive tract and other abdominal organs to the liver.

What organs drain their blood into the hepatic portal vein?

• The stomach, small intestine, large intestine, spleen, pancreas, and gallbladder.

How does the liver receive blood?

• Through the hepatic artery (oxygenated blood) and the portal vein (nutrient-rich blood).

Where does the blood leave the liver?

• Through the hepatic vein, which drains into the inferior vena cava.