Name: how platelets help blood clot
Uploaded: 2025-05-22T09:06:15.000Z
Duration: 1 min 18 s
Channel: JoVE

K12 Standards

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

9-12

Human Anatomy and Physiology

Transport

Blood

Structure and Function of Platelets

A microliter of blood contains 150,000 to 400,000 small, disc-shaped cell fragments called platelets or thrombocytes.
These fragments originate in the bone marrow from the myeloid stem cell, which forms the megakaryoblast.
Hormones like thrombopoietin and interleukin-6 influence the megakaryoblast to enlarge and replicate its DNA without cell division, producing megakaryocytes.
These large cells extend multiple cytoplasmic extensions through the sinusoid wall &#8212; specialized red marrow capillaries.
As the ends of the extensions rupture, a large number of cell fragments are released into the bloodstream.
These fragments quickly seal their membranes, packaging the cytoplasm into platelets with a 2-4 micrometer diameter.
Platelets lack a nucleus but possess cytoplasmic granules containing clotting factors, enzymes, and growth factors crucial for clotting and wound healing.
When any blood vessel is damaged, platelets rush to the injury site. Their granules release enzymes and growth factors to initiate the clotting process.
They adhere to the damaged walls, forming a temporary plug to prevent further blood loss.

structure and function of platelets

The cell fragments known as platelets are disc-shaped, with an average diameter of about 3 &#956;m and a thickness of roughly 1 &#956;m. They play a crucial role in the body&#39;s vascular clotting system, which also involves plasma proteins, blood cells, and blood vessel tissues.
Platelets are continually replenished, circulating in the bloodstream for 9-12 days before being removed by phagocytes, primarily in the spleen. A microliter of circulating blood contains between 150,000 and 450,000 platelets, with an average concentration of 350,000/&#956;L. Approximately one-third of the body&#39;s platelets are present in the spleen and other vascular organs at any given time instead of circulating in the bloodstream. These reserves can be mobilized during a circulatory crisis, such as severe bleeding.
Platelet production, or thrombocytopoiesis, occurs in the red bone marrow. Megakaryocytes, large cells with giant nuclei, are responsible for producing platelets. These cells manufacture various proteins, enzymes, and membranes during their development. Eventually, they release platelets into the bloodstream. A mature megakaryocyte can generate approximately 4,000 platelets before its nucleus is broken down and recycled by phagocytes.
Megakaryocyte activity and platelet formation are influenced by three substances: thrombopoietin (TPO), interleukin-6 (IL-6), and multi-CSF. Thrombopoietin, a hormone produced in the kidneys, stimulates platelet formation and the production of megakaryocytes. Interleukin-6 also stimulates platelet formation, while multi-CSF promotes the growth and formation of megakaryocytes, thereby increasing platelet production.
Platelets have several functions, including releasing chemicals that are vital in clotting. By releasing enzymes and other factors, platelets help initiate and control clotting. They can also form a temporary patch in the walls of damaged blood vessels by clumping together at the injury site, creating a platelet plug that can slow blood loss while clotting occurs. Finally, platelets contain filaments of actin and myosin, which can contract to reduce the size of the break in the vessel wall after a blood clot has formed.

The cell fragments known as platelets are disc-shaped, with an average diameter of about 3 &#956;m and a thickness of roughly 1 &#956;m. They play a ...

Education

JoVE Core

Anatomy and Physiology

Unit 1

KEY TERMS AND CONCEPTS

how platelets help blood clot

Platelets help blood clot and stop bleeding after a blood vessel is damaged. These cell fragments are disc-shaped and are about 3 bcm wide and 1 bcm thick. They work with plasma proteins, blood cells, and blood vessel tissues in the bodys vascular clotting system.

Platelets are constantly replaced in the bloodstream. They usually circulate for 9 to 12 days before phagocytes, mainly in the spleen, remove them. A microliter of blood contains about 150,000 to 450,000 platelets, with an average of 350,000/bcL. About one-third of the bodys platelets stay in the spleen and other vascular organs instead of moving through the blood. These stored platelets can be released during a circulatory crisis, such as severe bleeding.

Platelet production, called thrombocytopoiesis, happens in the red bone marrow. Large cells called megakaryocytes make the platelets. As they develop, they produce proteins, enzymes, and membranes. A mature megakaryocyte can release about 4,000 platelets before its nucleus is broken down and recycled by phagocytes.

Three substances help control megakaryocyte activity and platelet formation. Thrombopoietin, or TPO, is a hormone made in the kidneys that stimulates platelet formation and megakaryocyte production. Interleukin-6, or IL-6, also stimulates platelet formation. Multi-CSF supports the growth and formation of megakaryocytes, which increases platelet production.

Platelets have several jobs in clotting. They release chemicals, including enzymes and other factors, that help start and control clotting. They also clump together at an injury site to form a temporary platelet plug. This plug helps slow blood loss while a clot forms. Platelets also contain actin and myosin filaments, which can contract after a blood clot forms and reduce the size of the break in the vessel wall.

How Platelets Help Blood Clot

overview of the cardiovascular system

Cardiac Pumping and Blood Flow Paths

The cardiovascular system moves blood through the heart and blood vessels. It is the body’s transportation system for gases, nutrients, and waste products. The heart is the central pump in this system. It has two atria, which receive blood, and two ventricles, which pump blood out of the heart. Its rhythmic contractions, called heartbeats, keep blood moving continuously. Blood vessels carry blood to the body’s tissues and organs. Arteries are muscular, elastic vessels that move oxygenated...

characteristics and functions of blood

Blood as a Transport and Defense Tissue

Blood is a specialized connective tissue that helps the body transport materials, regulate conditions, and protect against harm. It makes up about 8% of body mass. Its extracellular matrix is thick and liquid. It contains cells, dissolved proteins, and electrolytes, which makes blood about five times more viscous than water. Blood is warm, with a temperature of about 38°C, and it has an alkaline pH between 7.35 and 7.45. Its main job is to carry oxygen and carbon dioxide between tissues and...

composition of blood

Blood Plasma and Formed Elements

Blood plasma and formed elements make up whole blood. Plasma is the yellowish fluid part and accounts for about 55% of blood volume. It is mostly water, with electrolytes and proteins mixed in. Plasma also carries blood cells and transports nutrients, enzymes, hormones, antibodies, and gases. The formed elements make up the remaining 45% of blood volume. These include red blood cells, white blood cells, and platelets. Red blood cells, also called erythrocytes, are the most common formed...

composition of blood plasma

Blood Plasma Proteins and Their Functions

Blood plasma contains water, proteins, and other dissolved solutes that help blood do its job. It is about 92% water and 8% solutes. The solutes include proteins, which make up about 7% of the total plasma solutes. The major plasma proteins are albumins, globulins, and fibrinogen. These high-molecular-weight proteins are essential to plasma function. Albumins make up about 60% of the plasma proteins. They help maintain osmotic balance in blood vessels by limiting water loss. Albumins also act...

overview of hematopoiesis

Hematopoiesis in Embryo, Bone Marrow, and Adults

Hematopoiesis is the process that makes blood cells throughout life. It produces red blood cells, white blood cells, and platelets from hematopoietic stem cells, or HSCs. The first HSCs form in the embryonic yolk sac, which is an early site of blood cell production. These stem cells then move to fetal tissues such as the liver, spleen, thymus, and lymph nodes. During this stage, the liver becomes the main site of hematopoiesis and greatly increases the number and variety of blood cells made. <br...

production of formed elements

Blood Cell Formation from Stem Cells

Blood cell formation begins with hemangioblasts and hematopoietic stem cells, or HSCs. Hemangioblasts are multipotent stem cells that come from the mesoderm, the middle embryonic layer. They give rise to HSCs, which start hematopoiesis, the process that makes the formed elements of blood. Hematopoiesis is controlled by a network of hematopoietic growth factors. These include transcription factors, growth factors, and cytokines. They signal HSCs to divide and specialize, but some HSCs stay...

role of hematopoietic growth factors

Signals That Guide Blood Cell Growth

Hematopoietic growth factors guide blood cell growth by controlling how hematopoietic stem cells, or HSCs, differentiate. These signaling molecules help direct the formation of red blood cells, platelets, and other blood cells in the bone marrow. Erythropoietin, or EPO, is mainly produced by the kidneys. When blood oxygen levels are low, EPO enters the bloodstream and reaches the bone marrow. There, it stimulates HSCs to mature into erythrocytes, the red blood cells that carry oxygen. <br...

erythropoiesis

Erythropoiesis and Red Blood Cell Formation

Erythropoiesis is the process that makes red blood cells. Red blood cells carry oxygen throughout the body, so this process is essential for normal blood function. The process begins in the bone marrow. There, blood-forming stem cells develop through several stages until they become mature red blood cells. As they mature, these cells change shape and prepare for their role in oxygen transport. Erythropoiesis helps maintain a steady supply of red blood cells. The body must replace these cells...

factors affecting erythropoiesis

How EPO Controls Red Blood Cell Levels

The body controls red blood cell levels through erythropoiesis, the process of making new erythrocytes. This helps keep oxygen transport efficient. It also prevents too many erythrocytes from building up, which would raise blood viscosity and slow flow. Low tissue oxygen is one of the strongest signals for this process. Intense exercise and high altitudes can both cause tissue hypoxia, which means too little oxygen reaches the tissues. In response, the kidneys release more erythropoietin, or...

structure and function of erythrocytes

How Red Blood Cells Carry Oxygen

Red blood cells, or erythrocytes, carry oxygen through the blood. There are about 4.2 to 6 million erythrocytes in every microliter of blood. Their small, flattened biconcave shape helps them move through the body efficiently. The center of each erythrocyte is depressed, which gives the cell its disc-like form. The plasma membrane is linked to proteins such as spectrin. Spectrin forms a flexible meshwork that lets the cell twist, turn, become cup-shaped, and then return to its biconcave shape...

hemoglobin

Hemoglobin and Blood Gas Transport

Hemoglobin is a globular protein that helps blood carry oxygen and other gases. It has four subunits. Two subunits are alpha chains, and two are beta chains. Each subunit contains a heme group with an iron atom that can bind oxygen. Oxygen binding changes hemoglobin’s shape. When one oxygen molecule binds to a heme group, the other heme groups bind oxygen more easily. When all four heme groups are bound, the molecule is called oxyhemoglobin. This form gives arterial blood its bright red color.<br...

lifecycle of erythrocytes

How Red Blood Cells Are Recycled

Red blood cells, or erythrocytes, are constantly moving through tiny blood capillaries. This movement creates friction that wears down the plasma membrane. Over about 100 to 120 days, the cells become rigid and fragile. Old erythrocytes often get trapped as they pass through small vessels in the spleen and liver. There, they can break into fragments. Resident phagocytic macrophages then engulf the damaged cells and separate the globin and heme parts. The globin chains are broken down into...

disorders of erythrocytes

Red Blood Cell Disorders and Blood Counts

Red blood cell disorders change the number, shape, or function of erythrocytes. Erythrocytes are red blood cells, and they help carry oxygen in the blood. These disorders are often grouped into two main types: anemic conditions and polycythemic conditions. Anemia happens when blood has a low oxygen-carrying capacity because erythrocytes are lost, made too slowly, or destroyed too early. Hemorrhagic anemia can develop after bleeding from an external wound or an internal ulcer. Iron deficiency...

structure and function of leukocytes

How White Blood Cells Defend the Body

White blood cells, also called leukocytes, help protect the body from toxins, pathogens, and abnormal cells. In a healthy adult, blood usually contains about 4,500 to 11,000 leukocytes per microliter. That is about 1% of total blood volume. Leukocytes differ from red blood cells in an important way. They have a nucleus and other cell organelles, but they do not contain hemoglobin. Most white blood cells are found in connective tissues, especially in lymphatic organs such as the lymph nodes,...

classification of leukocytes

Leukocyte Types and Immune Roles

Leukocytes are grouped by whether they have cytoplasmic granules. Granular leukocytes contain granules and belong to the myeloid lineage. They include neutrophils, eosinophils, and basophils, which are all roughly spherical cells with visible granules in the cytoplasm. Neutrophils are the most common granular leukocytes and make up about 50-70% of all leukocytes. They have small, evenly spread granules and a polymorphonuclear shape with two to five lobes in the nucleus. Their main role is...

disorders of leukocytes

Leukocyte Counts in Disease

Leukocyte disorders can change the number of white blood cells in the blood. A low leukocyte count is called leukopenia, and a high leukocyte count is called leukocytosis. These changes can help show whether the body is struggling to make leukocytes or responding to a problem. Leukopenia can result from bone marrow disorders, autoimmune disease, and infectious disease. Multiple myeloma and aplastic anemia can damage the bone marrow’s ability to produce enough leukocytes. Lupus and HIV can also...

Platelets help blood clot and stop bleeding after a blood vessel is damaged. These cell fragments are disc-shaped and are about 3 bcm wide and 1 bcm thick. They work with plasma proteins, blood cells, and blood vessel tissues in the bodys vascular clotting system. Platelets are constantly replaced in the bloodstream. They usually circulate for 9 to 12 days before phagocytes, mainly in the spleen, remove them. A microliter of blood contains about 150,000 to 450,000 platelets, with an average...

introduction to hemostasis

Three Stages of Blood Clotting

Hemostasis is the body’s way of stopping bleeding after a blood vessel is injured. It keeps blood fluid inside the circulatory system, but it also allows blood to clot when a vessel is damaged. This fast response depends on clotting factors in plasma, platelets, and substances released by injured tissue cells. The first stage is the vascular phase. Blood vessels narrow in a process called vasoconstriction, which reduces blood flow to the injury site and limits blood loss. This early step helps...

vascular spasm

Blood Vessel Constriction in Hemostasis

Blood vessel constriction is the first step of hemostasis, the process that helps stop bleeding after an injury. Also called vascular spasm, this response begins when a vessel is cut and nerves in the damaged area send pain and other sensory signals. At the same time, the smooth muscle in the vessel wall contracts and narrows the opening at the injury site. This slowing of blood flow helps reduce blood loss through the damaged vessel wall. The spasm usually lasts about 30 minutes. It becomes...

formation of the platelet plug

Platelet Adhesion and Aggregation in Hemostasis

Platelet adhesion and aggregation are key steps in hemostasis after a blood vessel is injured. This platelet phase is the second stage of hemostasis and begins about 15-20 seconds after the injury. It follows the vascular phase, when the blood vessel constricts to reduce blood loss, and the two phases overlap. As the injured vessel contracts, endothelial cells also contract. This exposes collagen fibers in the basement membrane and the tissue below it. The endothelial cell surface also becomes...

coagulation

Blood Clot Formation After Injury

Blood clot formation helps stop blood loss after a blood vessel is injured. It is the final stage of hemostasis, the body’s process for stopping bleeding. This stage uses a series of chemical reactions to seal the damaged area with a clot. Clotting starts soon after injury. In severe damage, it can begin within 15 to 20 seconds. With minor injuries, it often begins within 1 to 2 minutes. Clotting factors, also called procoagulants, start and carry forward the coagulation cascade. This cascade...

extrinsic and intrinsic pathways of hemostasis

extrinsic-and-intrinsic-pathways-of-hemostasis

How Blood Clots Form: Coagulation Pathways

Blood clotting, also called coagulation, happens through the extrinsic and intrinsic pathways. These two pathways end by joining the common pathway, which forms a fibrin clot. Both pathways are activated after a blood vessel is injured, but they begin in different ways. The extrinsic pathway starts when tissue damage exposes tissue factor, or TF. TF is released by damaged cells outside the blood vessels. When TF interacts with activated Factor VII, the TF-Factor VIIa complex forms and...

clot retraction and fibrinolysis

How Blood Clots Shrink and Break Down

Blood clots shrink and break down through clot retraction and fibrinolysis. After a fibrin clot forms, platelet contractile proteins such as actin and myosin pull the fibrin strands closer together. This condenses the clot into a smaller, denser mass that helps seal the damaged vessel. Clot retraction also supports wound healing. As the clot tightens, it brings the edges of the injured blood vessel closer together. Platelets also release growth factors that help repair the injury.

disorders of hemostasis

Blood Clots and Bleeding Disorders

Disorders of hemostasis can cause blood to clot too much or clot too little. Hemostasis is the process that stops bleeding after a blood vessel is injured. When this balance fails, the result may be a thromboembolic disorder or a bleeding disorder. Thromboembolic disorders involve a clot, or thrombus, forming inside a blood vessel. They can be linked to irregular vessel texture, such as from arteriosclerosis, infection, or injury. Slow blood flow through vessels can also promote thrombin...

the abo blood group

ABO Blood Types and Compatibility

The ABO blood group system explains how blood types are matched for transfusions and organ transplants. It depends on specific antigens, also called agglutinogens, on the surface of red blood cells, or RBCs. It also depends on antibodies, called agglutinins, in the blood plasma. Antigens are substances that can trigger an immune response and lead to the production of antibodies. In the ABO system, antigen A and antigen B are the two main antigens. These protein molecules are genetically...

rh blood group

Rh Factor in Blood Transfusions

The Rh factor is a protein on the surface of red blood cells and is an important part of blood typing. If the Rh antigen is present, a person is Rh-positive. If it is absent, the person is Rh-negative. For example, someone with type A blood can be A positive or A negative depending on whether the Rh antigen is found on their red blood cells. Rh status matters in blood transfusions because donor and recipient blood must be compatible. If Rh factors do not match, the immune system can react...

blood typing

Blood Grouping with ABO and Rh

Blood grouping with the ABO and Rh systems identifies the antigens on red blood cells. These surface antigens help determine a person's blood type. They are also important for transfusion medicine, organ transplants, and pregnancy, where compatibility matters. The main antigens used in this process are A, B, and D, which is the Rh antigen. Antigens are protein molecules on the surface of red blood cells. Blood groups are identified by testing these antigens with specific anti-sera. <br...

blood transfusion

Matching Blood Types for Transfusion

Blood transfusion depends on matching blood types to keep the procedure safe. A transfusion is a medical treatment that moves blood from a donor to a recipient. It can replace blood lost from injury or surgery, and it can also help treat conditions such as anemia or cancer. The ABO blood group system is the key part of this matching process. It classifies blood by the antigens, which are surface markers, on red blood cells. The four ABO blood types are A, B, AB, and O. Compatibility matters...

bone marrow sampling and transplants

Bone Marrow Transplants for Disease Treatment

Bone marrow transplants can treat serious diseases by replacing damaged red bone marrow with healthy stem cells. Doctors use this procedure for patients with aplastic anemia, certain leukemias, severe combined immunodeficiency disease (SCID), Hodgkin's disease, non-Hodgkin's lymphoma, multiple myeloma, thalassemia, sickle-cell disease, and some cancers. The process begins with high doses of chemotherapy and radiation. These treatments destroy the cancerous or defective red bone marrow and help...

key terms and concepts

Learn how platelets are made, stored, and activated to form a platelet plug and help blood clot after blood vessel injury.

How Platelets Help Blood Clot | JoVE K12

anatomy and physiology

JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.34

Overview of the Cardiovascular System

The cardiovascular or circulatory system comprises the blood, the heart, and the blood vessels.
Blood is a specialized fluid comprising cells in a liquid ...

Characteristics and Functions of Blood

Approximately 8% of the body mass comprises whole blood, a specialized connective tissue vital for transportation, regulation, and protection.
The ...

Composition of Blood

Whole blood consists of the blood plasma, a fluid extracellular matrix, and formed elements, including cells and cell fragments.
Blood plasma, which makes ...

Composition of Blood Plasma

Blood plasma is a fluid that contains approximately 92% water and 8% solutes. The solutes include various types of proteins, which constitute about 7% of ...

Overview of Hematopoiesis

Hematopoiesis, or hemopoiesis, is the production of the formed elements in blood from common progenitors, called hematopoietic stem cells, or HSCs.
During ...

Production of Formed Elements

Hemangioblasts, the multipotent stem cells of mesodermal origin, give rise to hematopoietic stem cells or HSCs.
The HSCs undergo hematopoiesis to produce ...

Role of Hematopoietic Growth Factors

Hematopoietic growth factors are a group of regulatory and signaling molecules that influence the differentiation of hematopoietic stem cells, or HSCs.
...

Erythropoiesis

Factors Affecting Erythropoiesis

The cardiovascular system regulates erythrocyte numbers for optimal oxygen transport. It also prevents erythrocyte over-proliferation, maintaining blood ...

Structure and Function of Erythrocytes

There are 4.2 to 6 million erythrocytes, or red blood cells, per microliter of blood. These small cells are flattened biconcave discs with depressed ...

Hemoglobin

Hemoglobin is a tetrameric globular protein consisting of two alpha and two beta polypeptide chains.
Each of these chains has an iron-containing heme ...

Lifecycle of Erythrocytes

The circulating erythrocytes frequently squeeze through blood capillaries, damaging their plasma membrane due to constant friction.
After about 100 to 120 ...

Disorders of Erythrocytes

Erythrocyte disorders are broadly categorized into anemic and polycythemic conditions.
Anemia develops due to the low oxygen-carrying capacity of the ...

Structure and Function of Leukocytes

A healthy individual has about 4,500 to 11,000 leukocytes or white blood cells per microliter of blood, accounting for about 1% of blood volume.
Unlike ...

Classification of Leukocytes

Leukocytes are classified into two groups based on the presence or absence of cytoplasmic granules. Granular leukocytes, which contain granules, belong to ...

Disorders of Leukocytes

Leukocyte disorders are characterized by either leukopenia, an abnormally low leukocyte count, or leukocytosis, a very high leukocyte number.
Bone marrow ...

Introduction to Hemostasis

Hemostasis is a series of rapid, defensive reactions triggered to stop excessive bleeding and promote healing after a vascular injury.
It is a highly ...

Vascular Spasm

The vascular phase, also known as vasospasm, is the initial stage of hemostasis, crucial for preventing excessive bleeding when a blood vessel is injured. ...

Formation of the Platelet Plug

In an injured blood vessel, the platelet phase - which overlaps with the vascular phase - begins about 15-20 seconds after the onset of vascular spasm.
As ...

Coagulation

Coagulation or clotting is the last hemostasis phase. It involves a series of chemical reactions to form a blood clot, reinforcing the initial platelet ...

Extrinsic and Intrinsic Pathways of Hemostasis

The extrinsic and intrinsic pathways of coagulation involve reaction cascades of clotting factors. They merge into the common pathway, eventually forming ...

Clot Retraction and Fibrinolysis

The activated platelets in a blood clot extend projections and interact with other platelets and fibrin fibers.
Within 30 to 60 minutes, the contractile ...

Disorders of Hemostasis

Thromboembolic disorders and bleeding disorders are two types of disruptions in hemostasis.
The thromboembolic disorders are characterized by the ...

The ABO Blood Group

The ABO blood group system is based on the presence of specific antigens or agglutinogens on the red blood cells, or RBCs, and antibodies or agglutinins ...

Rh Blood Group

The Rhesus or Rh antigen is a class of agglutinogen on the red blood cells or RBCs. Its presence or absence categorizes a person as Rh-positive or ...

Blood Typing

The antigens A, B, and Rh on the surface of red blood cells serve as the foundation for blood grouping.
When these antigens come in contact with their ...

Blood Transfusion

A blood transfusion is a medical procedure to replace lost whole blood or its components due to injury, surgery, or treatment for conditions like anemia ...

Bone Marrow Sampling and Transplants

Bone marrow transplants replace diseased marrow with healthy marrow from a compatible host. It can cure several cancers and genetic disorders like ...

Blood

Content elaboration: Blood is composed of plasma and the formed elements: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). The primary functions of blood are transportation, protection and regulation. Plasma, the most abundant component of blood, is the liquid portion that transports dissolved nutrients, waste, hormones, antibodies and proteins throughout the body. Red blood cells carry oxygen used during cellular processes throughout the body. White blood cells identify and protect the body against infectious disease and foreign cells. Platelets bind together when a blood vessel is damaged resulting in blood clot formation. The major ABO blood types, A, B, AB and O, are determined by the presence or absence of antigens on the surface of red blood cells. An additional antigen is present or absent on the surface of red blood cells determining Rh factor. Blood type antibodies are found in plasma. Processes related to blood include the production of blood cells and platelets, and hemostasis. Homeostatic imbalances are explored. These include, but are not limited to, sickle cell anemia, hemophilia, deep vein thrombosis, leukemia and lymphoma. Investigations are used to understand and explain blood in a variety of inquiry and design scenarios that can incorporate evolutionary concepts, scientific reasoning, comparative analysis, communication skills and real-world applications.

Overview of the Heart

The heart is a hollow muscular organ that pumps blood through the body.
It is cone-shaped and weighs about 250 to 300 grams on average.
The heart is ...

Location and Orientation of the Heart

The heart is located in the mediastinum and spans from the first rib to the diaphragm. It lies anterior to the vertebral column, posterior to the sternum, ...

Layers of the Heart Wall

The heart wall has three layers&#8212;the epicardium, the myocardium, and the endocardium.
The outermost layer, the epicardium, is the visceral layer of ...

Chambers of the Heart

The heart has four chambers&#8212;the right atrium, right ventricle, left atrium, and left ventricle.
Externally, the coronary sulcus separates the atria ...

Heart Valves

The heart valves open and close in response to the pressure gradients created by the contracting heart chambers.
These valves regulate the blood flow by ...

overview-of-systemic-and-pulmonary-circulation

Overview of Systemic and Pulmonary Circulation

The pulmonary and systemic circuits work sequentially to move blood between the heart, lungs, and peripheral tissues.
Pulmonary circulation transports ...

Coronary Circulation

The myocardium has its own network of blood vessels, separate from the systemic and pulmonary circuits, called the coronary circulation.
The left and ...

Conduction System of the Heart

Autorhythmicity refers to the innate ability of the heart to initiate electrical signals and trigger muscle contractions.
This intrinsic conduction system ...

Electrocardiogram

An electrocardiogram, abbreviated as ECG, or EKG, is a test that captures a record of the heart&#39;s electrical activity.
It is performed by placing ...

Cardiac Cycle

The cardiac cycle comprises the contraction, or systole, and relaxation, or diastole, during one heartbeat.
During atrial systole, cardiac action ...

correlation-between-ecg-and-cardiac-cycle

Correlation between ECG and Cardiac Cycle

The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac ...

Disturbances in Heart Rhythm

Disturbances in the heart rhythm, or arrhythmia, can cause irregular heartbeats.
If the heart rate falls below fifty beats per minute, it is called ...

Heart Sounds

Heart sounds are mainly produced when valve closures cause turbulence in the blood.
These are best heard at chest locations slightly away from the valves ...

Cardiac Output and Stroke Volume

Cardiac output is the blood volume ejected from the ventricles into the blood vessels each minute. It is calculated by multiplying the stroke volume by ...

Cardiovascular System

Content elaboration: The cardiovascular system consists of the heart and blood vessels. The heart is mostly comprised of cardiac muscle which is supplied with oxygenated blood by coronary arteries. The structure of the heart includes four chambers, four valves and major vessels leading to and from the heart. The flow of blood through the heart, pulmonary and systemic circuits should be explored. Blood flows from arteries, to arterioles, to capillaries, to venules, then to veins. In the capillaries, oxygen, nutrients, and chemical messengers diffuse out (leave) and carbon dioxide and other waste products diffuse in (enter). Veins have valves that keep the blood flowing toward the heart. The primary function of the cardiovascular system is the transport of oxygen, carbon dioxide, hormones, nutrients, waste products and chemical messengers. Processes involved in the cardiovascular system include the cardiac cycle and cardiac and conductive pathway which is measured by electrocardiograms and blood pressure. Homeostatic imbalances are explored. These include, but are not limited to, a variety of cardiovascular diseases and structural imperfections of the heart, valves and vessels. Examples include, but are not limited to, myocardial infarction, aneurysm, atherosclerosis, hypertrophic cardiomyopathy, hypo/hypertension and arrhythmias. Investigations are used to understand and explain the cardiovascular system in a variety of inquiry and design scenarios that can incorporate evolutionary concepts, scientific reasoning, comparative analysis, communication skills and real-world applications.

Cardiovascular System

How Platelets Help Blood Clot

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