HUMAN HEART

HUMAN HEART ANATOMY AND PHYSIOLOGY

INTRODUCTION TO THE CIRCULATORY SYSTEM BLOOD Is a fluid connective tissue a specialized body fluid Blood is a mixture of about 55 percent plasma and 45 percent blood cells About 7 to 8 percent of total body weight is blood It has four main components Plasma Red blood cells White blood cells Platelets

Functions Transport oxygen and nutrients to the lungs and tissues Form blood clots to prevent excess blood loss Carry cells and antibodies that fight infection Bring waste products to the kidneys and liver to filter blood Regulate body temperature

PLASMA

The liquid component of blood Mixture of water sugar fat protein and salts Transports blood cells throughout the body Besides nutrients waste products antibodies clotting proteins Chemical messengers such as hormones and proteins That help maintain body fluid balance

RED BLOOD CELLS ( Erythrocytes)

Bright red coloured cells The most abundant cell in the blood The shape of a red blood cell is a biconcave disc (looks like a donut)

Small size- Helps red blood cells pass through narrow capillaries Flattened disc shape- Provides a large surface area, allowing rapid diffusion of oxygenContainsspecial protein haemoglobin- Itabsorbs oxygen in the lungs and releases oxygen in the rest of the body Does not contain a nucleus-Increases amount of space inside the cell for haemoglobin Production of red blood cells is controlled by erythropoietin ( a hormone produced primarily by the kidneys)

White Blood Cells (Leukocytes)

White blood cells protect the body from infection Much fewer in number than red blood cells (about 1 percent of blood) The most common type of white blood cell is the neutrophil Account for 55 to 70 percent of the total WBC count Each neutrophil lives less than a day So bone marrow constantly makes new neutrophils

COMPONENTS OF BLOOD

Platelets (thrombocytes)

Unlike red and white blood cells platelets are not actually cells Rather small fragments of cellsPlatelets help the blood clotting (coagulation) Assemble at the site of an injury Stick to the lining of the injured blood vessel Form a platform on which blood coagulation can take place

MAJOR ARTERIES AND VEINS

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ARTERIES AND VEINS Arteries Red blood vessels that carry blood away from the heart Arteries carry oxygenated blood with the exception of (pulmonary artery and umbilical artery) Blood flows from the heart to various parts of the body Thick, elastic muscle layer that can handle high pressure of the blood Located deeper in the body walls Arterial walls are more rigid Valves aren't present Except for semi-lunar valves

Veins

Blue blood vessels that carry blood towards the heart Veins carry deoxygenated blood with the exception of (pulmonary veins and umbilical veins) Blood flows from various parts of the body to the heart Thin elastic muscle layer with semi lunar valves that prevent Blood from flowing in opposite direction Located closer to the skin Veins have collapsible walls ( Present mainly in limbs)

PRESSURE OF BLOOD IN ARTERIES AND VEINS Blood is pumped at high pressure away from the heart inarteries It travels through networks of thincapillaries Where it canexchangematerials with the tissues It's then collected up and returned to the heart at low pressure in veins

ARTERIES

The blood in the arteries is under high pressure generated by the heart therefore The arteries have Thick outer walls Thick layers of muscle and elastic fibers

DIAGRAM SHOWING ARTERIES AND VEINS

Veins

The blood in veins is under lower pressure than the blood in the arteries therefore The veins have Thin walls Thin layers of muscle and elastic fibers

THE HUMAN HEART

SIZE AND LOCATION OF THE HEARTHeart is a hollow conical muscular organIt is situated in the middle of the thoracic cavity above the diaphragm Under the rib cage, under and to the left of the breastbone (sternum) between the lungsIt is of the size of a fist measuring 12cm from base to apex 8cm broad and 6cm anterio posteriorlyAn adult human heart weighs between 250-350 gramsIt is the most important muscle in the bodyIt beats more than a 100,000 times a dayIt pumps about 2000 gallons of blood through a 60,000 times network of vessels in our body

BASIC ANATOMY OF HUMAN HEART

Human heart is a four chambered structureTwo upper chambers called the auricles (Pl: atria )Two lower chambers called the ventriclesThe four chambers of the heart are separated by means of a partition called the septumIn auricles this partition is called inter auricular septumIn ventricles it is called inter ventricular septum

THE TWO CHAMBERS OF THE HEART

The chambers on the left are the left auricle (atrium) and the left ventricle The chambers on the right are called the right auricle(atrium) and the right ventricleThe right atrium and right ventricle are often referred to as theright heartsimilarly the left atrium and left ventricle are often referred to as theleft heart

BLOOD VESSELS OF THE HEART

BLOOD VESSELS OF THE HEART

Aorta It is a largest artery in the human body .It leaves the left side of the heart and supplies oxygenated blood to the body tissues (Systemic Circulation) Pulmonary Veins - They are the blood vessels that deliver oxygenated blood from the lungs to heart. Two pulmonary veins enter the left side of the heart from each lung Pulmonary Artery - It is a blood vessel that carries deoxygenated blood from right side of the heart to the lungs (Pulmonary Circulation) Venacavae - (Latin :hollow veins) These are two large veins that return deoxygenated blood from body tissues to the right side of the heart

Inferior Venacava (IV) - It is the largest vein in the human body It carries deoxygenated blood from lower and middle body into the right atriumIt is formed by joining of the right and left Iliac veins The Iliac veins drain blood from the pelvis and the lower limbs and come together in the abdomen Superior venacava(SVC) - Returns deoxygenated blood from the systemic circulation to right atrium of the heart It has a large diameter 24mm It receives blood from the upper half of the body (upper limbs eyes neck and head) Large valveless venous channel formed by the union of the brachiocephalic veins (internal jugular and subclavian veins) Coronary sinus- Is a collection of veins joined together to form a large vessel It collects blood from myocardium (the heart muscle) Delivers blood to the right atrium as do the IVC and SVC

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DOUBLE CIRCULATION

Mammals have adouble circulatory system which means One circuit links the heart and lungs The other circuit links the heart with the rest of the body During a single cycle blood goes twice in the heart This means that there are two loops in our body in which blood circulates One isoxygenated blood ( oxygen rich) The other isdeoxygenated blood (it has little or no oxygen but a lot of carbon dioxide)

IMPORTANCE OF DOUBLE CIRCULATIONIt is necessaryto separate oxygenated and de-oxygenated bloodIt makes thecirculatory system more efficient Higher blood pressure so a greater flow of blood to the tissuesHelps to maintain a constant body temperature

WALLS OF AURICLES AND VENTRICLES The myocardium has four chambers two atria superiorly two ventricles inferiorly

Theatria areblood collection chambers The ventricles are blood pumping chambers

The right hand side of the heart is smaller than the left The muscle of the left ventricle is 2-3 times thicker than that of the rightAlthough the size of the cavity is about the same as the right

The ventricles have thicker muscular walls than the atria Because blood is pumped out of the heart at greater pressure from the ventricles compared to the atria

The left ventricle also has a thicker muscular wall than the right ventricle Because the left ventricle has to pump blood all around the body But the right ventricle has to pump blood only to the lungs Higher force is needed to pump blood through the systemic circuit compared to the pulmonary circuit

VALVES OF THE HEART

There are two types of valves in the heart

THE ATRIOVENTRICULAR VALVES Separate the atria from the ventricles

tricuspid valve (right atrioventricular valve) bicuspidormitral valve ( left atrioventricular valve)

THESEMI LUNAR VALVEFound at the base of the aorta and the pulmonary arteryAlso called the aortic semi lunar valve and the pulmonary semi lunar valve

Leaflets of the mitral and tricuspid valves Are attached to and supported By a ring of tough fibrous tissue (Annulus) Annulus helps to maintain the proper shape of the valve Also Supported by tough fibrous string (chordae tendenae) Which extend from valve leaflets to small muscle (papillary muscles) Papillary muscles are part of the inside walls of ventricles

Each valve has a set of flaps called leaflets or cusps Bicuspid valve- Mitral valve has two cusps flaps or leaflets Tricuspid valves- Tricuspid, Pulmonary and Aortic valve have three cusps

OUTER COVERING OF THE HEART The heartis a large muscular organ comprised of four different layers (from the outside to the inside) thePericardium the Epicardium the Myocardium the Endocardium

Pericardium A tough double layered fibro serous sac Contain the heartand the roots of thegreat vessels The pericardial sac has two layers serous layer fibrous layerThe space between the two layers of serous pericardium isPericardial cavity which is filled with serous fluid The pericardial fluidIt protects the heart from any kind of external jerk or shock

Fibrous Pericardium- It is the most external layer made of dense connective tissue Functions It protects the heart Anchor it to the surrounding walls Prevent it from over filling with blood

Serous Pericardium- It has two layers parietal pericardium (combined to and inseparable from the fibrous pericardium)

visceral pericardium (part of the epicardium)

The visceral layer extends till the opening of the great vessels It joins with the parietal layer where theaortaand pulmonary arteries leave the heart thevenacavaeand pulmonary veins enter the heart

FUNCTIONHelp to lubricate heart to avoid friction during heart activity

EPICARDIUM A thin layer ofconnective tissueand fat Provide an extra layer of protection for the heart It is considered an extension of serous pericardium

MYOCARDIUM Muscletissue of the heart Composed ofcardiac muscle cells (cardiomyocytes) Receives nervous stimulation from the sinoatrial node (SA) and atrioventricular (AV) node via purkinje fibres

WALLS OF THE HEART

ENDOCARDIUM Innermost layer of tissue Simple squamous endothelial Is continuous with Endothelial lining of great blood vessels

FUNCTION Lines the inside of the heart Offer a smooth lining for chambers of the heart Cover the valves

A SECTION OF THE HEART WALL

STRUCTURE OF THE CARDIAC MUSCLE Cardiac muscles are Involuntary and striated The cells that make up the cardiac muscle arecardiomyocytes Muscle fibers are shorter in length and larger in diameter Show branching therefore individual fibre looks Y-shaped A typical fibre is 50-100m long Has a diameter of about 14m Usually mononucleated Rarely two or four nuclei can be present Cells are interconnected by intercalated discs The sarcoplasm(the cytoplasm of striated muscles) is abundant Mitochondria are large and numerous Actin filaments are thin and myosin filaments are thick Cardiac muscle does not fatigue Cannot be repaired when damaged Regulated by the Autonomic Nervous System

Intercalated discs Are located betweencardiac musclescells

Anchoring structures of cardiac muscle cells

Hold gap junctions

Which allow cells to contract as a unit(synchronized contraction)

BLOOD FLOW THROUGH THE HEART The right and left sides of the heart work together causing blood to flow continuously to the heart lungs and body Right side of the heartBlood enters the heart through two large veinsThe inferior and superior vena cava emptying oxygen-poor blood (from the body) into the right atriumAs the right atrium contracts blood flows into right ventricle (through the open tricuspid valve)When the ventricle is full the tricuspid valve shuts Prevents blood from flowing backward into the right atrium while the right ventricle contractsAs the ventricle contracts blood leaves the heart (through the pulmonic valve)Into the pulmonary artery and to the lungs where it is oxygenated

The oxygenated blood then returns to the heart through thepulmonary veins Leftsideof the heart Pulmonary veins empty Oxygen-rich blood from the lungs into the left atrium As the atrium contracts Blood flows from atrium into the ventricle (through the open mitral valve)

When the ventricle is full (the mitral valve shuts) Prevents blood from flowing backward into the atrium (while the ventricle contracts) As the ventricle contracts Blood leaves the heart (through the aortic valve) Into the aorta and to the body

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BLOOD FLOW THROUGH THE HEART

Blood Flow Through Lungs Blood travels through the pulmonic valve enters the lungs (pulmonary circulation) From the pulmonary valve Blood travels to the pulmonary arteries Finally to small capillary vessels in the lungs Oxygen passes into the blood through Capillaries located in the walls Of tiny air sacs in the lungs (alveoli) At the same time Carbon dioxide (waste product ofmetabolism) Passes from the blood into the alveoli Carbon dioxide leaves the body as we exhale As the blood is oxygenated It travels back to the left atrium through the pulmonary veins Lastly from left ventricle to the body tissues through aorta (Systemic circulation)

THANK YOUPrepared byRitu sharma

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