Question

observation of internal structure of the mammalian heart​

Answer 1

Answer:

Explanation:The heart is divided into four parts by grooves. muscular partitions called septa. The openings between atria and ventricles are guarded by valves. After careful examination we can observe valves in the pulmonary artery and aorta as well.

Answer 2

Answer:                                              

The heart is the blood-pumping organ, mesodermally originated located in the thoracic cavity. The mammalian heart is quadri-chambered and is enclosed in a pericardium.    

Explanation:

The internal structure of the mammalian heart​

• In between the two layers of pericardium, a pericardial cavity is presently filled with pericardial fluid.

• The lumen of the heart is divided into two upper and two lower chambers by transverse and longitudinal septa.

• The heart has right and left atria with thin-walled chambers, divided by an interatrial or interauricular septum and, right and left ventricles separated by an interventricular septum.

• The right atrium receives the opening of the superior vena cava, the Inferior vena cava which is guarded by the eustachian valve and the coronary sinus by the Thebesian or Coronary valve.

• Fossa ovalis is a depression located on the interatrial septum. It represents the opening present in between two atrial during foetal life,

• Near the opening of the superior vena cava, the sinoatrial node (SA Node) is present.

• As it generates waves of contraction it is also called a Pacemaker.

• Near the tricuspid valve, the atrioventricular node (AV Node) is present on the interatrial septum.

• The atrioventricular bundle or "Bundle of His" starts from AVN and courses along the interventricular septum.

• The left ventricle receives the four pulmonary veins which are not guarded by any valve.

• The two ventricles are separated by the inter-ventricular septum.

• The right ventricle joins with the right auricle through the right atrioventricular aperture which is guarded by the tricuspid valve.

• This valve consists of three cusps or leaflets. Each cusp contains a nodule and lunule.

• These are attached to the papillary muscles, present in the inner wall of the ventricles, by chordae tendinae.

• The chordae tendinae are found extending from the valves to the columnar carneae, which are the muscular projections present on the walls of the ventricles.

• These ridges divide the cavity of the ventricles into small spaces called fissures. The pulmonary trunk arises from the right ventricle.

• The opening of this trunk is guarded by three half-moon-shaped valves, known as Semilunar valves.

• The left ventricle joins with the left atrium through the left atrioventricular aperture, guarded by a Bicuspid or Mitral valve.

• It consists of two cusps which are attached to papillary muscles by chordae tendinae.  The chordae tendinae extends into columnae carneae.

• The aorta arises from the left ventricle and is divided into ascending aorta, arch of the aorta and descending aorta. The left and right coronary arteries start from the ascending aorta.

• The opening of the aortic arch is also guarded by three semilunar valves.

• The valves allow the free, forward unidirectional flow of the blood and prevent the backward flow.

• The wall of the heart is made up of specialized muscular tissue, cardiac muscle.

• Three distinct layers are present in the wall of the heart out of which the outermost layer is called the pericardium. The second layer is the myocardium and is made of cardiac muscles.

• It is thin in the atrial region but thicker in the ventricular wall, being thickest in the wall of the left ventricle.

• The internal layer of the heart is the endocardium which is a thin layer of endothelium forming the wall of the lumen in the heart.

• Nerve Supply in the heart is controlled by the sympathetic and parasympathetic branches of the nervous system. The vagus nerve carries the impulses from the cardiac centre to the heart.

#SPJ3