Vertebrate Hearts

Differences and Similarities.

FISH NON-CROCODILE REPTILE

HUMAN

• 4 chambered heart arranged in series :- 1 atria, 1 ventricle, sinus venosus, bulbus arteriosus.

• 5 chambered :- 2 atria (left atrium an right atrium) and 1 ventricle with 3 interconnected compartements (cavum venusum, cavum palmonale, cavum arteriosum)

• 4 chambered heart :- 2 atria and 2 ventricle.

• a single circulatory system. • double circulatory system with incompletely divided heart.

• Double circulatory system with completely divided ventricle and atrium

• Blood flows from heart through gills to body tissues then back to the heart.

• Oxygenated blood enters left atrium and flow into cavum venosum and flow out to right and left aortas.• Deoxygenated blood enters right atrium and flow into cavum venosum and across cavum palmonale, flow out the pulmonary artery.

• Oxygenated blood flow from lungs to the left atrium of heart which then pumped to the body.• Deoxygenated blood from the body flow into right atrium of heart which then pumped into lungs.

Differences of Heart Chambers

FISH NON-CROCODILIAN REPTILE

HUMAN

• Some fish have accessory heart (caudal heart) in the tail to assits blood flow back to the heart.

• No accessory heart. • No accessory heart.

• Have gills. • Have incompletely separated pulmonary and systemic circuit (deoxygenated blood and oxygenated blood can mix)

• Have completely separated pulmonary and systemic circuit with different pressure.

Differences (cont.)

All cosists of 4 main parts :

Similarities of Vertebrate Hearts

i. Pericardium • Fluid filled sac that surrounds the heart.• Fluid acts as lubricant to reduce friction when the heart beats.• Elasmobranchs : pericardium is rigid.• Other species : pericardium is compliant and stretches easily as heart

beats.• Parietal pericardium (outer layer of pericardium) :

o Made of connective tissue.o Protects heart and anchors it to the surrounding structures.

ii. Epicardium • Outer connective tissue of heart which continuous to the inner layer of

pericardium (visceral pericardium).• Nerves and coronary arteries located in the epicardium.• Nerves :- regulate the heart.• Coronary artery :- supply blood to the heart.

iii. Myocardium• Layer of heart muscle.• Divided into several layers :- distinguished based on orientation

cardiomyocytes in each layer.• Cardiomyocytes is the cardiac muscle cells.(fish and reptiles have different myocardium structure compare to human)

iv. Endocardium• The innermost lining of the heart.• Composed of a layer of connective tissue covered by endothelium.• Endothelium connective tissue lines the chamber of the heart.

Compact myocardiumi. Outer layer : made of tightly

packed cells arranged in regular pattern.

ii. Usually in mammals.

iii. Contain blood vessels that supply oxygen by the coronary arteries.

Spongy myocardiumi. Inner layer : consist of meshwork

of loosely connected cells.

ii. Usually in fish and amphibians.

iii. Does not contain blood vessels.

iv. Takes up oxygen from deoxygenated blood in lumen of heart.

v. Arranged into trabeculae that extend into heart chambers.

Type of Myocardium

Blood Cell

Hemocytes

Hemocytes is divided into two :-

i. Erythocytes.ii. Leukocytes.• Lymphocytes • Monocytes• Granulocytes• Thrombocytes

Erythrocytes contain hemoglobin which function in storage and transport of oxygen.

Leukocytes lack of hemoglobin and performs specific immune functions :• Monocytes (develop into macrophage) and granulocytes have same

function which is to destroy the foreign particles and also damaged cells.

• Granulocytes divided into three :• Neurophils :- engulfed damaged cells, microorganisms and also foreign

phatogens by phagocytosis.• Eusinophils :- act as delivery vehicles to carry cytotoxic chemicals.• Basophils :- accumulate in the interstitial fluid and release cytotoxic

chemicals at the infected area, cytotoxic chemicals will kill the microorganisms and other phatogen.

Function of Hemocytes

• Lymphocytes divided into two type of cells :-• B lymphocytes (B cells) which function to make antibodies.• T lymphocytes (T cells) which help B cells to make antibodies and also

involved in taking macrophages and neutrophils to the infected site.

• Thrombocytes :- involve in blood clotting.