Human heart

Human Heart.


Depending upon the mode of contraction there are two kinds of hearts:
Myogenic hearts: The hearts in which the wave of contraction starts in the muscle fibre of heart are said to be myogenic hearts. Eg. Human Heart.
Neurogenic Heart: The in which the contraction wave takes its origin from its nerve cells of group of such cells are said to be neurogenic hearts. Eg. Frog’s heart.
Structure if Human Heart.
A Human Heart is a triangular and muscular organ located in thoracic cavity between the lungs. The human heart is about 12 cm in length and 250gms in weight.
External structure of Human Heart
Human Heart is a conical muscular organ, enclosed and protected in a double chambered wall called pericardium. The cavity between two pericardial membrane s filled with pericardial fluid that prevents the heart from shocks, mechanical injury and also allows free movements of the heart.
Human Heart is a four chambered organ, having two auricles and two ventricles. Right auricles and right ventricles that deals with the impure blood whereas the left chamber is for pure blood. There is no mixing pure and impure blood inside or outside the heart.
The external structures of Human Heart are:
Auricles: Auricles are thin walled chambers. The left auricle is smaller than the right auricle, Right auricle receives impure blood from the superior venacava and inferior vanacava. Whereas the left auricle receives pure blood from the two pulmonary veins.
Ventricles: Ventricles are thick walled. The left ventricle is somewhat longer and about three times thicker than the right ventricle. Right ventricle receives impure blood from the right auricle and left ventricle receives pure blood from the left auricle.
Pulmonary trunk and aorta: The pulmonary trunk arises from the right ventricle. It divides into ledt and right pulmonary arteries that carry deoxygenated blood to the lungs. Similarly an aorta arises from the left auricle, This gives off three branches namely: Innominate, left common carotid and left subclavian.
Internal structure of Human Heart.
Auricle: Auricle are thin walled chambers separated by inter auricular septum.The opening of the venecave that provided impure blood to the right auricle is guided by Eustachian valve.
Bicuspid and tricuspid valves: The auricles and ventricles are separated by the auriculo-ventricular septum. Each auricle opens into its corresponding ventricle through an auriculo-ventriculo aperture. These apertures are guarded by flaps or valves which opens only in the ventricle and prevent the back flow of the blood . The left auriculo-ventricular aperture is guared by bicuspid valve or mitral valve. Similarly the right auricular structure is guared by tricuspid structure. These valves are attatched to the walls of the ventricles by the help of tendons of fibrous chords called chordae tendinae. Its main function is to hold the flaps.
Ventricles: Ventricles are thick walled, separated by thick and oblique inter-ventricular septum. The walls of ventricles have many muscular ridges or projections called columnae carnae. IT divides the cavity of ventricles into smaller spaces, known as fissures. Right ventricle receives the impure blood whereas the left ventricle receives pure blood. Due to the contraction of ventricles, the blood is pumped forcefully to the different parts of the body.

Circulatory system

Circulatory System.
Introduction
All the parts o the body needs constant supply of nutrients, oxygen etc. along with other required minerals for the metabolic activities to take place. For this purpose some extra cellular fluids are are continuously flowinf through the body all the time, this fluid is called blood. And the flow of blood is called circulation and the structures and organs which are involved in theis process are called circulatory system.
This helps in balancing a favourable internal environment inside the body, this process is called homeostatis.
Functions of Circulatory system:
Circulatory system helps in the transport of gases
Transportation of O2 from respiratory surface to tissues and CO2 from the tissues to the respiratory surfaces through circulatory system
Circulatory system transport of metabolic waste products
circulatory system transport various metabolic wastes produced from different tissues from which they are transported to arous organs so that they can be removed out of the body
Circulatory system transport of digested food substances
circulatory system absorps and transports digested food from the site of absorption to the different organs of the body of storage, oxidation or synthesis etc
Circulatory system transport of chemical messengers
circulatory system transports the chemical messengers like hormones from the site of their origin to the target organs
Circulatory system helps in tempreture regulation
circulatory system regulates the body tempreture by distributing the heat produced in one part of the body to different parts there by equalizing the body tempreture
Circulatory system helps in transport of metabolic intermediates
The fluid present in the circulatory system carries the various intermediate compounds produced in metabolic reactions from one tissues to another for further metabolism.
Circulatory system helps in protection against the diseases.
The circulatory system produced phagocytic leucocytes that engulf and kill harmful micro organisms.