[4]
Embedded Files
Heart
Heart
A heart is the main organ of the circulatory system in animals, pumping blood through blood vessels. [1] Pumped blood carries oxygen and nutrients to tissue with metabolic waste like carbon dioxide to the lungs to oxygenate the blood--to receiving oxygen.
metabolic waste: substances made during metabolism unusable by a body
metabolism: process when body converts food/drinks to energy
oxygenate: to receive oxygen
Humans' heart are roughly a closed fist's size, located between the lungs, in the middle compartment of the chest, called the mediastinum (image [4.1]).
compartment: a structure's section with some parts separated from others
mediastinum (etm): Latin 'medius' means ‘middle’
the anterior view of a human heart
Structure
Structure
A human heart divides into 4 chambers: upper left and right atria (pl. atrium) and lower left and right ventricles.
atrium (etm): 'atrium' (original word) means 'central room/main hall' (since blood enters both deoxygenated/oxygenated blood enters the heart from both atria); where blood is received
[1] A human heart is in the mediastinum, at the level of thoracic vertebrae T5–T8 ([5] image).
thoracic vertebrate T5-T8: 4 of the 12 thoracic vertebrae comprising the vertebral column's middle section
thoracic: anything related to the thorax or the chest
vertebrae: individual bones making up the spine; not confused to vertebrate for animals with backones
A double-membraned sac called the pericardium surrounds the heart and attaches to the mediastinum.[16] The back surface of the heart lies near the vertebral column, and the front surface, known as the sternocostal surface, sits behind the sternum and rib cartilages.[8] The upper part of the heart is the attachment point for several large blood vessels—the venae cavae, aorta and pulmonary trunk. The upper part of the heart is located at the level of the third costal cartilage.[8] The lower tip of the heart, the apex, lies to the left of the sternum (8 to 9 cm from the midsternal line) between the junction of the fourth and fifth ribs near their articulation with the costal cartilages.[8]
[5]
[4.1]
X2Download.com-The Heart and Circulatory System - How They Work-(480p) (online-video-cutter.com).mp4The heart is one of the circulatory system's main element (alongside blood,and blood vessels). It's an organ about size of a fist, located at left lung (which makes left lung smaller as it takes more place), pumps 5 quarts/minute around the body, beats around 100k times/day, and 35m times/year.
It's made of 4 chambers' contractions that make the sound of heartbeats with blood flowing according to its valves and is made of 3 different types of tissue:
Nerve tissue
Cardiac muscle tissue
Connective tissue
Valves
Valves
Valves are door-like muscles controlling fluids' blood by opening, closing, or partially obstructing various passageways.
There are 4 valves:
Tricuspid valve - where deoxygenated blood enters the heart.
Pulmonary/Semilunar valve: ensures that no blood flows backward.
Mitral valve ensure blood flows through from the left atrium to the left ventricle.
Aorta valve has 3 cusps and ensures that blood flows through to the aorta from the left ventricle.
Atria and Ventricles
Atria and Ventricles
Atria (plural of atrium) are always on the top of the heart.
Ventricles are always on the bottom of the heart.
recalling tip: 'A' and 'V' are on top of each other to help recall which is on top and which is at the bottom of the heart.
The heart pumps one of the body's main cells; red blood cells that mainly carries oxygen to cells across the body and contains a substance called hemogolin.
Human heart anatomy is observed into 2 separated sections:
Oxygenated section
Deoxygenated section
Deoxygenated blood
→
Oxygenated blood
←
(Any pulmonary part are always involved with the lungs)
Blood circulation
Blood circulation
Heart rate's beats changes depending on physical activities, stressful situations, or general health.
Muscle nerves are covered by smooth layers of epithelial tissues, protecting the heart from damage when the lungs expand and contract.
A heart's inner surface is also lined with smooth epithelial tissue and endocardium for blood to flow. If hardened, it can cause health problems.
The numbers in this section indicate the order in the blood flow across the heart.
1-2. Inferior and superior vena cava
1-2. Inferior and superior vena cava
The inferior (IVC) and Superior Vena Cava (SVC) are the two veins receiving deoxygenated blood after moving across the body.
IVC receives blood from the body's lower half.
SVC is for the body's upper half.
3. Right atrium
3. Right atrium
The right atrium receives deoxygenated blood from the superior and inferior vena cava and pumps blood to through the tricuspid valve.
4. Tricuspid valve
4. Tricuspid valve
The tricuspid valve ensures that blood pass from the right atrium to the right ventricle. It's called tricuspid as it has three cusps.
The valves
6-7. Pulmonary/Semilunar valve and arteries
6-7. Pulmonary/Semilunar valve and arteries
Pulmonary/Semilunar valve ensures that no blood flows backward. Papillary muscles and their shape helps them to stay close when needed, which is an inverted gate. Papillary muscles are connected to the valve with tiny attachments called chordae tendini
5. Right ventricle
5. Right ventricle
From the right atrium, through the tricuspid valve, blood flows into the right ventricle, which has thicker walls as it needs more force to pump blood up into the pulmonary artery to the lungs for oxygen, unlike the right atrium only needs to pump blood down to the ventricle.
The heart's right side is for pulmonary circulation, the circulation of blood between the heart and lungs.
8. Pulmonary vein
8. Pulmonary vein
There are two pulmonary veins.
Right lung blood enters the right pulmonary artery. Left lung blood enters the left one.
9. Left atrium
9. Left atrium
The left atrium receives blood through the pulmonary vein
10. Mitral/Bicuspid valve
10. Mitral/Bicuspid valve
The mitral/bicuspid/left atrial ventricular valve ensure blood flows through from the left atrium to the left ventricle. Like the tricuspid valve, the mitral valve has also papillary muscles.
11. Left ventricle
11. Left ventricle
The left ventricle receives blood through the bicuspid valve from the left atrium and sends it through the aortic valve to the aorta.
It's the most muscular chamber as it needs to send blood to the systematic circuit, which has a lot of resistance.
12. Aortic valve
12. Aortic valve
The aortic valve ensures that blood flows through to the aorta from the left ventricle. It has three cusps.
13. Aorta
13. Aorta
Main section: Aorta
The aorta receives and transports oxygenated blood from the aortic valve to the rest of the body, and is the largest vessel in the body.
Septum
Septum
The septum plays a crucial role in keeping the blood flow, preventing the mixing of oxygen-rich and oxygen-poor blood, allowing the heart to efficiently pump blood to both the systemic and pulmonary circulations. The septum are also crucial to maintain the heart's rhythm and function, as it helps coordinate the electrical signals that regulate the heart's contractions.
The septum is the wall that divides the left and right side of the heart. It helps maintain the efficient and separate circulation of oxygenated and deoxygenated blood.
Aorta
Aorta
The largest vein has the role of transporting oxygenated blood, starting with three arteries from the heart's left side, extending up to the chest, separating to the neck, arms, and across the stomach to the legs.
[2] a real aorta
The aortic root is attached to the heart with a major part that's part of the aortic valve.
The sinotubular junction is where the aortic valve meets the start of the main aorta.
It has three cusps:
left coronary cusp
non-coronary cusp
right coronary cusp
Above the sinotubular junction are the right and left coronary arteries, supplying oxygen-rich blood to the heart muscle
Next, is the ascending aorta, going up and connects the aortic arch.
Note: "ascends" means going up, like ascending aorta.
An arc
The aortic arch is an arch-shaped section that meets the descending aorta.
It's divided into three arteries:
The brachiocephalic artery carries blood to the right arm and the brain's right side. It's divided into two arteries:
etymology: (Lat.) brachiocephalic = "branchio" means "upper arm" + "cephalic" means "relating to the head"
The right subclavian artery goes to the right arm.
The right common carotid artery
etymology: (Gr.) "carotid" means "deep sleep"
It's named so as issues in carotid arteries can cause sleeping symptoms
The left common carotid artery
The left subclavian artery goes to the left arm.
etymology: (Lat.) subclavian = "sub" means "under" + "clavium" refers to the clavicles/collar bone
right↔left
Many other human parts' names (including the aorta) are divided into a person's left and right perspectives.
The descending aorta is the longest aorta tube, starting after aorta arch and down to the abdomen.
It's divided into two arteries:
right iliac arteries
left common iliac arteries
The abdominal aorta goes from the diaphragm to above the pelvis, dividing into the iliac arteries.
There are five arteries that branch from the abdominal aorta:
celiac artery
superior mesenteric artery
inferior mesenteric artery
renal arteries
iliac arteries
The celiac artery gives blood to the stomach, liver and pancreas; the superior mesenteric artery supplies blood to the small intestine; the inferior mesenteric artery supplies blood to the large intestine; and the renal arteries provide blood to the kidneys as well as the muscles of the abdominal wall and the lower spinal cord. The end of the abdominal aorta branches into the iliac arteries, which supply blood to the legs and the organs in the pelvis.
Heart layers
Heart layers
The heart is mainly divided into three layers: endocardium, myocardium, and pericardium
Their prefixes indicate their respective location.
- Endocardium
Endocardiums ("endo" means inner/within) are made of endothelial cells, which form water-type barrier, making no blood to seep into the endocardium
seep: enter/penetrate
2. Myocardium
2. Myocardium
Myocardium ("myo" means muscle) is the main layer of the heart, made up of cells called cardiomyocytes/cardiac muscle cells. Although the endocardium blocks any blood from penetrating to the myocardium, the heart has a circuit called the "coronary circuit" (because there's a ring of vessels at the top of the heart resembling a crown) to send oxygen-rich blood to its tissues and return the oxygen-poor blood to the right atrium. It's made up of by coronary arteries and cardiac veins. In the right picture, the aorta has cardiac veins (red ones) wrapped around the heart to deliver blood. Cardiac veins (blue ones) carry back oxygen-pure blood to a part called the coronary sinus, which is where all blood is drained back to the right atrium
3. Pericardium
3. Pericardium
Pericardium ("parry" means around) are the surrounding layers on the outside. It has its own two layers: first the the parietal pericardium and under is the visceral pericardium.
Pericardium is known as a serous membrane as it create a fluid called serous fluid.
Parietal and visceral pericardium
We can vizualize the pericardium's two layers and the heart as a hand (heart) pushing down a balloon (pericardium).
The visceral layer is attached to the heart.
In between is he parietal cavity/space. It's made of proteins making it very slippery.
The pericardium acts as a sac holding the heart in place. Its serous fluid reduces how much friction the heart will experience as it beats.
Cardiac Conduction Cycle
Cardiac Conduction Cycle
The heart is like the active muscles when we exercise.
The heart's muscle cells are called cardiomyocytes ("cardio" means heart "myo", muscles, "cytes", cells).
Unlike other muscle cells, cardiomyocytes have a property called automaticity: They can generate acts without being notified by external nerves.
Muscle cells moving the body need to be notified by nerves to move. The heart doesn't need to be in a body to continue beating.
To understand the cardiac conduction, sinoatrial node need to be first explored.
Sinoatrial node
Sinoatrial node
The sinoatrial (SA) node, sometimes called the heart's pacemaker because it has the best automaticity. Though all cardiac cells have automaticity, in the right atrium (1 in the right picture), the SA note fires first and sets the rhythm for the rest of the heart.
Though the heart functions by itself, it's influenced by the autonomic nervous system to either speed up or slow down its heart rate using the parasympathetic nervous.
Normal heart rate is still fast as the SA node has fast automaticity.
But the parasympathetic vague nerve needs to extend from the medulla oblongata to innervate the SA node, before inhibiting the SA node and slows it down to the normal heart rate of 60 to 100 bpm: beats per minute.
Tachycardia and Bradicardia
Tachycardia and Bradicardia
Tachycardia is a fast heart rate, over 100 bpm.
Recall tip: our heart rate increase ("tach"ycardia) when we seat on a tack.
tackle: pin
Bradiycardia refers to the a slow heart rate, under 60 bpm.
The SA node is the first to reach its minimum requirement, sending a wave of depolarization through both atria and ventricles, causing both to contract, making all blood in the atria end up feeling the ventricles.
depolarization: change in a cell when it undergoes a shift in electric charge distribution, causing negative charge in the cell unlike the outside
Once this depolarization wave reaches the bottom of the right atrium, it encounters a structure called the atrioventricular (AV) node. Its role is to add a short delay between the Atria's contraction and the ventricle's contraction.
If the atriums and ventricles contract simultaneously, the ventricles can't fill.
After the delay, the AV node sends an electrical signal to the "his bundle"/bundle of his, at the interventricular septum.
The interventricular septum is named so as it's a wall separating the two ventricles.
The his bundle then sends a signal to to the right and left bundle branches, which then pass signals onto the Purkinje fibers, located at the walls in the ventricles with the job to ensure that ventricles both contract at once.
Systole and Diastole
Systole and Diastole
Although atria and ventricles have different systole phases, the overall cardiac cycle is mostly defined by ventricular contraction, meaning that the overall cardiac is said to be constant.
Systole occurs when the ventricle eject blood into the arteries they're connected to, when the artery pressure is the greatest.
Diastole occurs after ventricular contraction, when the myocardiuma and ventricles are completely relaxed.
References
References
Quizzes
Quizzes
Page updated
Google Sites
Report abuse