The Heart and Pericardium

• The cardiovascular system conducts oxygenated blood and nutrients to tissues and collects non-oxygenated blood.
• It consists of the heart, arteries, and veins.

The Heart (Cor)

• Hollow muscular organ
• Positioned in the middle (cardiac) mediastinal space, 2-3 cm dorsal to the sternum
• The right side of the median plane is in a 4:5 ratio
• Extends from the 2nd intercostal space to the 6th rib or intercostal space

Pericardium

• A fibroserous sac encloses the heart and part of the large vessels connected to its base
• Parts include the outer fibrous pericardium and the inner serous pericardium

Outer Fibrous Pericardium

• Attaches ventrally to the sternum via the sternopericardial ligament
• In dogs, it attaches to the diaphragm via the phrenicopericardial ligament

Inner Serous Pericardium

• A closed sac invaginated by the heart, formed of two layers:
• Outer parietal layer, which adheres to the fibrous pericardium
• Inner visceral layer called the epicardium, which covers the myocardium

Pericardial Cavity

• Space between the two layers and contains serous pericardial fluid

Heart Features

• Cone-shaped with an apex and a base

Surfaces

• Right (atrial) and left (auricular)

Borders

• Cranial (convex) and caudal (nearly straight)

Grooves

• Includes coronary, interventricular subsinosal (right longitudinal), and interventricular paraconal (left longitudinal) grooves.

Heart Chambers and Valves

• The heart has four chambers and four valves

Chambers

• Includes two atria (right and left) and two ventricles (right and left)

Valves

• There are two atrio-ventricular valves
• Tricuspid valve is between the right atrium and right ventricle
• Bicuspid (Mitral) valve is between the left atrium and left ventricle
• There are two semilunar valves: the aortic semilunar valve and the pulmonary semilunar valve

Right Atrium

• Is the cranial part of the heart base

Right Atrium Composition

• It is composed of the right auricle with the sinus venarum cavernum

Right Atrium Openings

• Includes the cranial vena cava, caudal vena cava, right Vena azygos, coronary sinus, right atrioventricular opening, and foramina venerum minimarum, which are openings of small veins

Right Atrium Structures

• The intervenous crest is a muscular ridge that projects cranially to the caudal vena cava and directs blood to the atrioventricular opening
• The fossa ovalis is a diverticulum in the wall between the two atria; it is a closed foramen oval

Left Atrium

• Forms the caudal part of the heart

Openings of Left Atrium

• Consists of 6-8 openings of pulmonary veins which collect oxygenated blood from the lungs
• It has a left atrioventricular opening guarded by the bicuspid valve (Mitral valve)
• The left auricle is on the left side of, and just caudal to, the conus arteriosus

Ventricles

• Right and Left Ventricles compared

Position

• The right ventricle is cranial, while the left is caudal

Length

• The right ventricle does not reach the apex, the left stretches further

Wall

• The right ventricle wall is thin while the left is thick

Cross Section

• The right ventricle is Cresenteric, whilst the left in circular

Lumen

• The right ventricle has a wide lumen, whilst the left has a narrow lumen

Shape

• The right ventricle has a triangle shape, whilst the left has a cone shape

Papillary Muscle

• The right ventricle has 3, whilst the left has 2.

Artery

• The right ventricle has a pulmonary trunk, whilst the left has the Aorta

Blood

• The right ventricle carries non-oxygenated blood, whilst the left carries oxygenated blood

Atrio-Ventricular Orifice

• The right ventricle is Tricuspid, the left is Bicuspid

Semilunar Valve

• The right ventricle has a pulmonary valve, the left as an aortic valve

Pulmonary Trunk

• Originates from the right ventricle through the conus arteriosus, guarded by the pulmonary semilunar valve
• Ascends between the right and left auricles and divides into right and left pulmonary arteries to enter the lung
• Pulmonary arteries follow the bronchial tree, carries non-oxygenated blood
• The pulmonary trunk connects with the Aorta via ligamentum arteriosus

Aorta

• Originates from the left ventricle through conus arteriosus, guarded by the aortic valve
• The Ascending Aorta gives rise to the right and left coronary arteries
• The Aortic Arch gives rise to the Brachiocephalic trunk
• Includes the Descending Aorta.

Coronary Arteries

• Nutritional blood supply to the heart
• Arises from the right and left coronary sinuses
• Passes in the coronary groove and the interventricular septum.

Abdominal Aorta Branches

• Includes three single branches and five paired branches

Single Branches

• Celiac trunk supplies the stomach, liver, and spleen
• Cranial Mesenteric artery supplies the small intestine, cecum, ascending and transverse colon
• Caudal Mesenteric artery supplies the descending colon and rectum

Paired Branches

• Lumbar arteries supply abdominal muscles
• Renal arteries supply kidneys and suprarenal gland
• Testicular (Male) / Ovarian arteries (Female) corresponds with the sex
• External iliac arteries supply hind limbs
• Internal iliac arteries supply pelvic organs and external genitalia