CLASS X Biology CLASS X Biology BLOOD CIRCULATORY SYSTEM BLOOD CIRCULATORY SYSTEM (Transport System in Humans) (Blood Vascular System) - This system consists of 1) Muscular chambered HEART 2) A network of closed branching BLOOD VESSELS i) Arteries, ii) Veins, & iii) Capillaries. 3) The fluid tissue BLOOD i) RBC ii) WBC & iii) Platelets

HEART It is located right in the centre between two lungs in THORACIC CAVITY. Roughly triangular heart is pointed to the LEFT SIDE. Size is equal to closed FIST. (size is 12 cm in length and 9cm width).

- Protected by double walled membranous covering called Pericardium. - It is enclosing by lubricating fluid called Pericardial Fluid. - This fluid reduce friction and protect from mechanical injuries.

- Heart is divided into Four chambers. - Upper two chambers are called ATRIAS / AURICLES. Atria have thinner walls & main function is to receive blood. - Lower two chambers are called VENTRICLES. Ventricles have thick muscular walls because they have to pump the blood to all body parts.

Internal view Four Chambers: -Right ventricle pumps blood only up to the lungs for oxygenation. -But the left ventricle pumps it up to the farthest points in the body.

SEPTUM -Both atria divided by a fibrous tissue called INTER-ATRIAL SEPTUM. -Both ventricles are divided by thick fibrous tissue called INTER-VENTRICULAR SEPTUM. -The atrium and the ventricle of the same side are also separated by ATRIO-VENTRICULAR SEPTUM.

Major blood vessels connected to heart 1 – superior/anterior & inferior/posterior vena cava (2) enter into right atrium. (anterior vena cava brigs DOB from upper regions like head, chest, and arms. posterior vena cava brigs DOB from lower regions like abdomen and lungs.) 2 - pulmonary vein (4) enter in to left atrium and brings OB from lungs. 3 - pulmonary artery (2) arises from right ventricle & carries DOB to lungs for oxygenation 4 – aorta (1) arises from left ventricle & carries OB to supply it to all parts of the body

Coronary Arteries : These two small blood vessels are arising from the base of aorta And supply the blood to the heart muscles. Coronary Veins : Collect blood from heart walls and pour it into the right auricle.

-Heart Attack: The blockage in any coronary arteries is a deadening of the corresponding area of heart muscles leading to “Myocardial infarction” or heart attack. -Chest Pain: It is due to insufficient supply of blood to the heart muscles, and this pain is also called as ‘Angina pectoris’

VALVES -The opening between right atrium and right ventricle is guarded by a valve called Right atrio-ventricular valve or Tricuspid Valve. (3 flaps=cusps) - The opening between left atrium and left ventricle is guarded by a valve called Left atrio-ventricular valve or Bicuspid Valve Or Mitral Valve. - The pulmonary artery and aorta respectively are provided with the Semilunar Valves. Chordae tendinea Papillary muscles

Internal View Three kinds of valves

T.S of Human heart – Valves Valves prevent any backward flow of blood, facilitates single direction Tricuspid valve is formed by three muscular flaps or cusps. Bicuspid valve is formed by two muscular flaps or cusps. Semilunar valves are formed by three half-moon shaped cusps. (pocket-shaped)

CLOSED AND OPEN POSITONS OF VALVES Chordae tendinea Papillary muscles

DOUBLE CIRCULATION: In this circulation blood passes through the heart twice before completing a full circuit of the body. These two are… 1. Pulmonary circulation: carries DOB away from the right ventricle to the lungs through pulmonary artery, and returns OB to the left atrium of the heart through pulmonary vein 2. Systemic circulation: carries OB blood from the left ventricle, to the tissues of the all body parts through aorta. From the tissues the DOB returns to the right atrium of the heart through anterior vena cava & posterior vena cava.

TWO MAIN PHASES OF HEART BEAT: (1) ATRIAL SYSTOLE AND VENTRICULAR DIASTOLE: (Diastole) - Atrial muscles contract - Opening of vena cava and pulmonary vein close -Blood enters ventricles by crossing through tricuspid valve (1) and bicuspid valve (2) - Semilunar valves at the roots of pulmonary artery 3 and 4 are closed producing the sound ‘DUP’ to prevent flow of blood back in ventricles

(2) VENTRICULAR SYSTOLE AND ATRIAL DIASTOLE: (Systole) - Ventricular muscles contract -Tricuspid valve (1) and bicuspid valve (2) close with a jerk producing the Sound “LUBB” -Blood passes into aorta and pulmonary artery through semilunar valves(2) -Atria draw in blood through the opening of vena cava and pulmonary vein - Chordae tendinae hold the valves in position preventing their upturning due to pressure exerted by the contracting ventricles. 12

NODES & NODAL FIBRES IN HEART - A special cardiac musculature called the nodal tissue distributed in heart. - A patch of this tissue is present in the right upper corner of the right atrium called the sino-atrial node (SAN) - Another patch is seen in the lower left corner of the right close to the atrio-ventricular septum called the atrio-ventricular node (AVN)

-Minute nodal fibres along with right and left bundles from AVN are known as BUNDLE OF HIS - The minute nodal fibres throughout the ventricular musculature of the respective sides are called PURKINJE FIBRES. - The nodal tissue has ability to generate action potentials without any external stimuli, so we can call it is AUTOEXITABLE. - The SAN can generate maximum number of action potentials ( / min). It is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore SAN is called the PACEMAKER.

CLASS - 10