- The human heart is situated behind and slightly to the left of the sternum, between the lungs (breastbone).
- The left side of the chest contains two-thirds of the heart, with the right side holding the remaining third in balance.
- The human heart is about the size of a human first and is divided into four chambers, namely two ventricles and two atria.
- The ventricles are the chambers that pump blood and atrium are the chambers that receive blood.
- Among which both right atrium and ventricle mark up the “right heart” and the left atrium and ventricle mark up the “left heart”.
- The structure of the heart also houses the biggest artery in the body the aorta.
- The right and the left region of the heart are separated by a wall of muscle called the septum.
- The right ventricle pumps the blood to the lungs for re-oxygenation through the pulmonary arteries.
- The right semilunar valves close and prevent the blood from flowing back into the heart.
- Then, the oxygenated blood is received by the left atrium from the lungs via the pulmonary veins.
External structure of the heart
- The human heart is situated to the left of the chest and is enclosed within a fluid-filled cavity known as the pericardial cavity.
- The walls and lining of the pericardial cavity are made up of a membrane known as the pericardium.
- The pericardium is a fibrous membrane found as an external covering around the heart.'
- It protects the heart by producing a serous fluid, which serves to lubricate the heart and prevent friction between the surrounding organs.
- Apart from the lubrication, the pericardium also helps by holding the heart in its position and by maintaining a hollow space for the heart to expand itself when it is full.
- Visceral Layer: It directly covers the outside of the heart.
- Parietal Layer: It forms a sac around the outer region of the heart that contains the fluid in the pericardial cavity.
Internal Structure of the heart
1. Left
atrium
2. Right
atrium
3. Left
ventricle
4. Right
ventricle
- Atria: atria are thin less muscular walk
and smaller than ventricle these are the blood-receiving chamber that are fed
by the large veins.
- Ventricles: ventricles are larger and more
muscular chambers responsible for pimping and pushing blood out to the circulation.
These are connected to larger arteries that deliver blood for circulation.
The right ventricle and right atrium
are comparatively smaller than the left chamber.
The walls consist of fewer muscle
compared to the left portion and the size difference is based on their
function.
The blood origination from the right ride flows through the pulmonary circulation, while blood arising from the left chamber is pumped throughout the body
Valves
- Valves are flops of fibrous tissues located in the cardiac chamber blur the veins
- They ensure that the blood from flows in a single direction.
- Flaps also prevent the blood from flowing backward
- Based on their function, values are of types.
- Veins: veins supply deoxygenated blood to the heart via inferior and superior vena cava, and it eventually drains into the right atrium.
- Capillaries: capillaries are tiny, tube-like vessels, which form a network between the arteries to veins.
- Arteries: arteries are muscular – walled tubes mainly involved in supplying oxygenated blood away from the heart in all other parts of the body. Aorta is the largest of the arteries, and it branches off into various smaller arteries throughout the body.
Structure of the heart wall
The heart wall is made up of 3 layers, namely
1. Epicardium: epicardium is the outermost layer of the heart.
It is composed of a thin-layers the outer section.
2. Myocardium: this is a layer of muscle tissue, and it constitutes the middle layer wall of the hear.
It contributes to the thickness and responsible for the pumping action.
3. Endocardium: It is the innermost layer that lines the inner Peart chambers and covers the heart values.
Furthermore, it prevents the blood from sticking to the inner walls, thereby preventing potentially total blood clots.
Hyper of
circulation
1. Pulmonary circulation: pulmonary circulation is a portion of circulation responsible for carrying deoxygenated blood away from the heart, to the lungs and them brings oxygenated blood back to the heart.
2. Systemic
circulation: systemic circulation is another portion of circulation where the
oxygenated blood is pumped from the heart to every organ and tissue in the
body, them back again to the heart.
3. Coronary
circulation: coronary circulation is an essential portion of the circulation,
where oxygenated blood is supplied to the heart. This is important, as the
heart is responsible for supplying Blood throughout the body. The circulation
system plays a vital role in supplying oxygen, nutrients and removing carbon
dioxide and other waster from the body.
The function
of heart
- The function of the heart in any organism is to maintain a constant flow of blood throughout the body.
- This replenishes oxygen and circulation nutrients among the cells and tissues.
✔ Following are the main functions of
the heart:
- One of the primary function of human heart is to pump blood throughout the body.
- Blood delivers oxygen, hormones, glucose and other components to various heart.
- The heart also ensures that adequate blood pressure is maintained in the body
The Aorta
the aorta is the largest artery of the body which carries the oxygenated blood from the left ventricle and supplies it to all the parts of the body.
- The aorta initially is one inch wide in diameter.
- The aorta is classifies as a large elastic artery.
1. The ascending aorta
2. The aortic arch
3. The thoracic
(descending) aorta.
4. The abdominal aorta.
- The first 3 parts are confined to the thoracic cavity and together create the thoracic aorta.
- Common Carotid Artery: The common carotid artery is a paired structure that supplies blood to the head and neck.
- Subclavian Artery: Paired major arteries of the upper thorax, below clavicle. The receive blood from the aortic arch.
- Axillary Artery: Large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla (armpit) and the upper limb.
- Brachial Artery: Major blood vessel of the (upper) arm.
- Superficial Palmar Arch: The superficial and deep palmar arches (serve as a network of arteries inside the palm).
- Femoral Artery: Large artery in the thigh and the main arterial supply to the thigh and leg.
- Internal iliac Artery: Runs downward along the lateral wall of the pelvis.
- Inferior Vena cava (IVC): Large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. Its walls are rigid and it has valves so the blood does not flow down via gravity.
- Hepatic Portal Vein: Blood vessel that carries blood from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver. This blood contains nutrients and toxins extracted from digested contents.
- Portosystemic Anastomoses: The importance is to provide alternative routes of circulation when there is a blockage in the liver or portal vein. These routes ensure that venous blood from gastrointestinal tract still reaches the heart through inferior vena cava (IVC) without going through the liver.
- Great Saphenous Vein (GSV)/ Long Saphenous Vein: A large, subcutaneous, superficial vein of the leg. It is the longest vein in the body, running along the length of the lower limb, returning blood form foot, leg and thigh to the deep femoral vein at the femoral triangle.
- Dural Venous Sinuses: The spaces between the endosteal and meningeal layers of the dura. They contain venous blood that originates for the most part from the brain or cranial cavity.
Peripheral Pulse
It refers to the palpation of the high-pressure wave of blood moving away from the heart through vessels in the extremities following systolic ejection.
Palpation occurs at various locations of the upper and lower extremities including the radial, brachial, femoral, popliteal, posterior tibial and dorsalis pedis arteries.
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