SISTEM VASKULAR DAN
SIRKULASI DARAH
Sistem vaskular merupakan komponen esensial
pada sistem sirkulasi
Komponen esensial pada sistem sirkulasi sbb:
Jantung: merupakan organ jaringan otot
yang menghasilkan gerakan (memompa darah)
Arteri: merupakan jalan pengangkutan
darah ke organ-organ dan ke jaringan-jaraingan
Kapiler: merupakan saluran-saluran kecil
yang beranastomosis, yang membagi dan melakukan pertukaran bermacam-macam substrat antara darah dan cairan jaringan
Vena: merupakan jalan pengangkutan darah
Struktur Jantung
Endocardium. Merupakan lapisan yang paling dalam, terdiri atas jaringan Endothel
Myocardium. Merupakan lapisan di tengah, terdiri atas jaringan otot. Jaringan
ototnya tipis di bagian atrium dan tebal di bagian ventrikel.
Pericardium. Merupakan
lapisan yang paling luar,
terdiri atas jaringan ikat dan epithel.
Jantung dipisahkan dari organ-organ dalam
toraks lainnya oleh pericardium
Epicardium merupakan jaringan fibrosa yang
menutupi myocardium
Ruang antara pericardium dengan epicardium
disebut ruang pericardium atau kantung pericardium
Ruang pericardium secara normal berisi 5-30
mL cairan jernih, yang melumaskan jantung dan memungkinkannya berkontraksi tanpa banyak mengalami gesekan
Jantung terdiri atas 4 ruang, yaitu 2 atrium
(kiri dan kanan) dan 2 ventrikel (kiri dan kanan).
Heart Pumping Action
Deoxygenated blood (blood low
in oxygen content) from various parts of the body first returns to the right atrium through the two venae cavae
Blood from the head, neck and
arm goes to anterior (upper) vena cava and blood from the lower parts of the body is brought back by the posterior (lower) vena cava. From the venae cavae open into the right atrium
The right atrium contracts, blood flows into the right ventricle.
The contraction of the right atrium does not causes the blood to flow down into the ventricle. The ventricle first relaxes, creating an empty cavity for blood to flow into the ventricle. The right atrium then contracts, forcing the remaining blood in it to go down into the right ventricle.
As the right ventricle contracts, blood in it is forced out into the
pulmonary artery. There is a valve separating the atrium and ventricle, that prevents blood from flowing back into the atrium as ventricle contracts. This valve is known as the Tricuspid valve, because it has three flaps. These flaps are attached to cord-like tendons called chordae tendineae. As the ventricle contracts, the blood pressure forces the flaps to close. The tendons prevent the flaps from being turned back into the atrium.
Similarly, there is a valve in the pulmonary artery just as it
leaves the heart. When the right ventricle relaxes, the valves are forced close to prevent back-flow of blood.
The pulmonary artery then carries the deoxygenated blood to
the two lungs, where the blood becomes oxygenated again and returns the heart via the pulmonary vein.
Now the blood comes to the right side of the heart. The left
side of the heart works much like the right side.
Blood from the pulmonary vein flows into the left atrium,
and enters the left ventricle. Between the left atrium and the left ventricle is the bicuspid valve. This is similar in structure and function to the tricuspid valve but as the name suggests, it has only two flaps instead of three. When the left ventricle contracts, blood leaves by way of a large artery, the aortic arch. From the aortic arch blood is distributed to all parts of the body. The aortic arch curves upwards from the left ventricle as a U-shaped tube and it also possesses valves to prevent the back-flow of blood.
The heart muscle of the left ventricle is thicker than muscle
of the right ventricle. This is because, the right ventricle only needs to pump blood to the lungs, which are not far away from the heart. Less force is required to send the blood to the lungs. However, the left ventricle has a much harder job of pumping blood to the rest of the body.
The Valves in The Heart
Valves in the heart plays a significant part in
helping the heart to pump the blood around the body efficiently. A valve is just like a door. However, a valve opens only into one direction and only allow the passage of one way
There are four valves in the heart:
the tricuspid valve between the right auricle and right ventricle,
the bicuspid valve between the left auricle and left ventricle, and
the two pulmonary valves, one each at between the right ventricle and the pulmonary artery and at between the left ventricle and the aorta
Siklus Jantung
Bagian-bagian jantung secara normal berdenyut
dengan urutan teratur. Pada saat jantung berdenyut terjadi 2 fase, yaitu:
Systole. Merupakan fase kontraksi, yang meliputi
kontraksi atrium (atrium systole) dan kontraksi ventrikel (ventricle systole).
Diastole. Merupakan fase relaksasi. Selama fase
ini semua empat rongga jantung dalam keadaan relaksasi.
Pada saat atrium berkontraksi (atrium systole) darah
mengalir ke ventrikel. Sedangkan pada saat ventrikel berkontraksi (ventricle systole) darah mengalir ke arteria pulmonalis dan ke aorta. Kemudian atrium dan ventrikel relaks untuk sementara waktu. Periode relaksasi ini disebut Diastole.
Otot jantung memiliki sifat unik yaitu berkontraksi
dan mengalami repolisasi lebih cepat saat kecepatan denyut jantung tinggi, dan durasi sistolik menurun dari 0,3 detik pada kecepatan denyut jantung 65 menjadi 0,16 pada kecepatan 200 denyut/menit
Pemendekan ini terutama disebabkan oleh
penurunan durasi semprotan sistolik. Namun durasi sistolik lebih konstan daripada durasi diastolik, dan apabila kecepatan denyut jantung meningkat, distolik mengalami pemendekan lebih besar. Hal ini memiliki dampak fisiologis dan klinis yang penting
Selama distolik (diastole) lah otot jantung
beristirahat, dan darah koroner mengalir ke bagian subendocardium ventrikel kiri terjadi hanya selama distolik. Selain itu sebagian besar pengisian ventrikel terjadi selama distolik.
Bunyi Jantung (Heart Sound)
Dalam keadaan normal terdengar dua bunyi
jantung melalui stetoskop selama setiap siklus jantung.
Bunyi pertama berbunyi "lub”: bernada rendah, sedikit lama atau sedikit memanjang, disebabkan oleh getaran yang ditimbulkan oleh penutupan mendadak katup mitral dan trikuspidalis pada permulaan sistolik ventrikel. Memiliki durasi sekitar 0,15 detik dan frekuensi 25-45 Hz. Bunyi ini lembut saat kecepatan denyut jantung lambat karena ventrikel terisi penuh oleh darah dan daun-daun katup AV mengapung bersama sebelum sistolik.
Bunyi kedua adalah "dub”: lebih singkat dan bernada tinggi yang disebabkan oleh getaran penutupan katup aorta dan pulmonaris tepat setelah akhir sistolik ventrikel. Bunyi kedua berlangsung sekitar 0,12 detik dengan frekuensi 50 Hz. Bunyi ini keras dan tajam apabila tekanan distolik di aorta atau arteri pulmonalis meningkat, yang menyebabkan katup-katup menutup dengan cepat pada akhir sistolik. Interval antara penutupan katup aorta dan pulmonaris selama inspirasi sering cukup panjang sehingga bunyi kedua mengalami reduplikasi (pemisahan fisiologis bunyi jantung ke dua). Pemisahan juga terjadi pada berbagai penyakit.
Pada orang dewasa muda, terdengar bunyi ketiga
yang lembut dan bernada rendah di dengar kira-kira pada 1/3 jalan diastolik. Bunyi ini bersamaan dengan masa pengisian cepat ventrikel dan mungkin disebabkan oleh getaran yang ditimbulkan oleh aliran darah masuk.
Kadang-kadang terdengar bunyi keempat sesaat
sebelum bunyi pertama saat tekanan atrium tinggi atau ventrikel kaku pada keadaan seperti hipertropi ventrikel. Ini disebabkan karena pengisian cepat ventrikel dan jarang didengar pada individu dewasa normal
Selain bunyi tersebut diatas, sering juga muncul
Murmur
A heart murmur is a swishing or a whistling sound
that the doctor hears when he listens to your heart. The doctor uses a tool called a stethoscope to listen to the heart.
A murmur is usually present when there is a heart
valve problem. The doctor will perform a variety of tests to determine what kind of valve problem you have and if the valve problem is serious. Some of the tests performed are: an echocardiogram, an electrocardiogram, a chest x-ray, or cardiac catheterization.
What Causes a Heart Murmur?
There are many different causes of heart
murmurs. They can be caused by a heart attack, high blood pressure, rheumatic fever, pregnancy, fever, thyrotoxicosis or anemia. Thyrotoxicosis is a condition caused by an overactive thyroid gland.
Blood pressure is the force created by the heart
as it pushes blood into the arteries and the circulatory system. When the heart pumps, it causes blood to flow through the arteries and into the arterioles. As the blood goes through the arterioles, the arterioles either contract or expand altering both the amount of blood flow and the resistance to blood flow. If the arterioles remain in a contracted form, they create high blood pressure. The heart must then pump harder because the arterioles are exerting a greater resistance to blood flow. High blood pressure is often called the "silent killer".
A fever is defined as a temperature 1° or more
above the normal 98.6 degrees Fahrenheight (F) or 37 degrees Celsius (C). Mild or short-term elevations in body temperature are common with minor infections. High fevers, with temperatures of 103° and above, can signal a potentially
dangerous infection. Fever is a symptom of a disease or infection. It is not a disease. Fever helps the body fight infections by making the body's defense systems work more efficiently. Bacteria and viruses cannot live at higher temperatures and are killed by fever.
Iron Deficiency Anemia (also called IDA) is a
condition where a person has inadequate amounts of iron to meet body demands. It is a decrease in the amount of red cells in the blood caused by having too little iron. IDA is usually caused by a diet insufficient in iron or from blood loss. Blood loss can be acute as in hemorrhage or trauma or long term as in heavy menstruation. Iron deficiency anemia is the most common form of anemia. About 20% of women, 50% of pregnant women, and 3% of men are iron deficient.
What is the Thyroid?
The thyroid produces hormones that influence every organ, tissue and cell in the body. The hormones also control heart rate, body weight, body temperature, energy level, muscle strength and menstrual regularity. When the thyroid becomes faulty or malfunctions, metabolic disorders occur. There are two main types of thyroid malfunctions: hypothyroidism and hyperthyroidism.
Hypothyroidism
Hypothyroidism occurs when the thyroid gland produces too little amounts of thyroid hormone, causes the body to function at a lower rate. Hypothyroidism can contribute to heart disease. It can contribute to heart disease because one of the side effects is an increased amount of LDL (bad) cholesterol circulating in the blood.
Hyperthyroidism
Hyperthyroidism occurs when the thyroid gland produces too much hormone. Hyperthyroidism increases the rate at which each cell functions, increasing all the reactions that occur in the body. Some of the symptoms of hyperthyroidism are: nervousness, decreased menstrual flow, weight loss, and irregular heartbeat.
Types of Heart Murmurs?
There are two main types of heart murmurs: diastolic and systolic. A diastolic murmur occurs when the heart muscle relaxes between beats. It occurs after the second heart sound. A systolic murmur occurs between the first and second heart sounds.
Heart Valve Problems
Heart Valve disease occurs when a valve doesn't work properly. If a valve doesn't open all the way, less blood can move through the smaller opening. If a valve doesn't close tightly, blood may leak backward. These problems can cause the heart to work harder to pump the same amount of blood. Or blood may back up in the lungs or body because it's not moving efficiently through the heart.
When the valve doesn't open completely, it is called Stenosis. When it doesn't close completely it is called Insufficiency or Regurgitation.
