One-way molecules move is by diffusion but it alone cannot supply the need. It takes much time for materials in solution to diffuse even a few inches Diffusion can work only in unicellular and simple multicellular organisms because every corner of their body is in close and direct contact with the environment. In complex multicellular bodies, cells are far apart from the environment and such bodies need a comprehensive system for the transport of materials. 

Water is vital to plant life. It is necessary not just for photosynthesis and turgor, but much of the cellular activities occur in the presence of water molecules and the internal temperature of the plant is also regulated by water. Land plants get water and minerals from the soil. After absorption by the roots, these water and minerals have to be transported to the aerial parts of the body.

The function of Xylem Tissue:

Xylem tissue is responsible for the transport of water and dissolved substances from roots to the aerial parts. It consists of two types of cells i.e. vessel elements and tracheids.

The function of Phloem Tissue:

Phloem tissue is responsible for the conduction of dissolved organic matter (food) between different parts of the plant body. It consists of sieve tube cells and companion cells.

During photosynthesis, food is manufactured in leaves. This food is transported to the other parts of the body for utilization and storage. All land plants (except for mosses and liverworts) have developed complex vascular systems that move water and food throughout the plant body. These vascular tissues are called xylem and phloem.

Water and Ion Uptake:

In addition to anchoring the plant, roots perform two other vital functions

1. First they absorb water and salts from the soil.
2. ii. Second, they provide conducting tissues for distributing these substances to the tissues of the stem. Root hairs provide a large surface area for absorption. They grow out into the spaces between soil particles where they are in direct contact with the water. The cytoplasm of the root hairs has a higher concentration of salts than the soil water, so water moves by sis into the root hairs. Salts also enter root hairs by diffusion or active transport. After they enter into the root hairs, water and salts must move through the epidermis and cortex of the root, and then into the xylem tissue in the center of the root

Pathways through which water travels from the outside of the root to the inside:

There are two pathways through which water travels from the outside of the root to the inside

1. The first of these pathways is the apoplast pathway, in which water travels along cell walls and through intercellular spaces to reach the core of the root.
2. the Second route for water is the symplast pathway, in which water moves across the root hair membrane and through the cells themselves, via channels (plasmodesmata) that connect their contents.

Note:

Once in the xylem, the water can be carried to all the aerial parts of the plant.

Internal Structure of Root:

The conducting tissues (xylem and phloem) of the root are grouped in the center to form a rod-shaped core, which extends throughout the length of the root.

Pericycle:

Outside the conducting tissues, there is a narrow layer of thin-walled cells, the pericycle. A single layer of cells, the endodermis, surrounds the pericycle layer. The remaining tissues of the root consist of a broad zone of large, thin-walled cells making up the cortex.

Cortex:

The cortex is bounded on the outside by a single layer of epidermal cells. Roots also have clusters of tiny root hairs, which are the extensions of epidermal cells.

Root hairs:

Root hairs provide a large surface area for absorption. They grow out into the spaces between soil particles where they are in direct contact with the water. The cytoplasm of the root hairs has a higher concentration of salts than the soil water, so water moves by osmosis into the root hairs. Salts also enter root hairs by diffusion or active transport. After they enter the root hairs, water and salts must move through the epidermis and cortex of the root, and then into the xylem tissue in the center of the root.

Water always moves from an area of higher water potential to an area of lower water potential. The difference in the water potentials depends upon the differences in the concentrations of solute and the amounts of water. The relationship between the concentration of solute and water potential is inverse i.e. where there are a lot of solutes the water potential is low. 

Plants also form beneficial relationships with soil bacteria and fungi to increase the absorption of minerals. 

Transpiration:

Transpiration is the loss of water from the plant surface through evaporation.

Opening and closing of stomata:

Most plants keep their stomata open during the day and close them at night.

Functions of guard cells:

It is the responsibility of the stomata to regulate transpiration via guard cells. The two guard cells of a stoma are attached at their ends. The inner concave sides of guard cells that enclose a stoma are thicker than the outer convex sides. When these guard cells get water and become turgid, their shapes are like two beans and the stoma between them opens. When the guard cells lose water and become flaccid, their inner sides touch each other, and the stoma closes.

The function of Potassium ions in opening and closing of stomata:

Recent studies have revealed that stomata open and close due to the movement of potassium ions in and out of guard cells. According to blue wavelengths of daylight open stomata by allowing K to flow into the guard cells, from the surrounding epidermal cells. Water passively follows these ions into the guard cells, and as their turgidity increases the stoma opens. As the day progresses, guard cells make glucose. Due to a higher concentration of glucose, their water potential decreases and water stays in them. At the end of the day, the K' flows back from guard cells to the epidermal cells, and the concentration of glucose also falls. This initiates the loss of water and reduced turgor pressure in guard cells, which causes the closure of the stoma.

Transpiration:

Transpiration is the loss of water from the plant surface through evaporation.

Functions of cuticle and lenticels:

This loss may occur through stomata in leaves, through the cuticle present on leaf epidermis, or through special openings called lenticels present in the stems of some plants.

Stomatal Transpiration:

Most of the transpiration occurs through stomata and is called stomatal transpiration.

The function of Mesophyll Cell in Transpiration:

The mesophyll cells of the leaf provide enormous surface area for the evaporation of water. Water is drawn from the xylem into mesophyll cells, from where it comes out and makes a water film on the cell walls of the mesophyll. From here water evaporates into the air spaces of the leaf. By diffusion, water vapors then move from the air spaces towards the stomata and then pass to the outside air.

Note:

Roughly 90% of the water that enters a plant is lost via transpiration.

Factors affecting the rate of transpiration:

1. The rate of transpiration is directly controlled bythe opening and closing of stomataand it is under the influence of light. In strong light, the rate of transpiration is very high as compared to dim light or no light. Other factors which affect the rate of transpiration are given below.
2. Higher temperature reduces the humidity of the surroundings and also increases the kinetic energy of water molecules. In this way, it increases the rate of transpiration. The rate of transpiration doubles with every rise of 10°C in temperature. But very high temperatures i.e., 40-45°C cause closure of stomata, so that transpiration stops, and the plant does not lose the much-needed water.
3. When air is dry, water vapors diffuse more quickly from the surface of mesophyll cells into leaf air spaces and then from air spaces to outside. This increases the rate of transpiration. In humid air, the rate of the diffusion of water vapors is reduced and the rate of transpiration is low.
4. Wind (air in motion) carries the evaporated water from leaves, and it causes an increase in the rate of evaporation from the surfaces of mesophyll. When air is still, the rate of transpiration is reduced.
5. The rate of transpiration also depends upon the surface area of the leaf. More surface area provides more stomata and there is more transpiration.

Drop in the pressure at the Sink end. 

Significance of Transpiration:

Transpiration is called a necessary evil. It means that transpiration is a potentially harmful process but is unavoidable too.

1. Transpiration may be a harmful process in the sense that it There is strong and requires wet surfaces from which evaporation can occur evidence that even during the conditions of drought loss of water from the plant mild water stress results in wilting, serious desiccation, and often the death of the plant, results in reduced This is the reason that at high temperatures, plants close their growth rate, stomata and reduce transpiration rate to prevent wilting.
2. On the other hand, transpiration is necessary too. It creates a pulling force called transpirational pull which is principally responsible for the conduction of water and salts from roots to the aerial parts of the plant body. When water transpires from the surfaces of the plant, it leaves a cooling effect on the plant. This is especially important in warmer environments. Moreover, the wet surfaces of leave cells allow gaseous exchange.

Note:

There is strong evidence that even mild water stress results in a reduced growth rate.

Xylem is one way street from the roots to the leaves for water and salts. Phloem is a two-way street for food. The direction of the movement is decided by supply and demand in the sources and sinks. 

Transportation of water in terms of transpirational pull:

Cohesion-tension Theory:

1. According to this theory the mechanism by which water (along with dissolved materials) is carried upward through the xylem is transpirational pull.
2. Transpiration creates a pressure difference that pulls water and salts up from their roots.

Mechanism of transpiration pull:

When a leaf transpires (loses water), the water potential of its mesophyll cells drops. This drop causes water to move by osmosis from the xylem cells of the leaf into the mesophyll cells. When one water molecule moves up by the xylem of the leaf, it creates a pulling force that continues to the root. This pulling force created by the transpiration of water is called transpirational pull. It also causes water to move transversely (from root epidermis to cortex and pericycle).

Reasons for the creation of transpirational pull:

Following are the reasons for the creation of transpirational pull.

1. Water is held in a tube (xylem) that has a small diameter.
2. Water molecules adhere to the walls of the xylem tube (adhesion).
3. Water molecules cohere to each other (cohesion) and do not contain dissolved gases (which would otherwise come out of water and form bubbles).

Note:

These attractions allow an overall tension among water molecules and form 'columns' of water. The columns of water move from root to shoot and the water content of the soil supplies water to the ‘columns.

1. The blood circulatory system.
2. The lymphatic system.

Transportation of Food:

Phloem is responsible for transporting food substances throughout the plant. The glucose formed during photosynthesis in mesophyll cells is used in respiration and the excess of it is converted into sucrose. In most plants, the food is transported in the form of sucrose.

Pressure flow mechanism:

The currently accepted hypothesis states that the transport of food is through the pressure-flow mechanism. In the pressure-flow mechanism, the food is moved from sources to sinks.

Source:

The sources include any exporting organs typically a mature leaf or storage organ.

Sinks:

Sinks are the areas of active metabolism or storage, for example, roots, tubers, developing fruits and leaves, and the growing regions. A storage organ is capable of storing food and exporting stored materials. For example, the root of beet is a sink in the first growing season, but becomes a source in the next growing season, when sugars are utilized in the growth of new shoots.

Mechanism of Source:

At the source, the food (sugars) is moved by active transport into the sieve tubes of the smallest veins. Due to the presence of sugar in sieve tubes, their solute concentration increases, and water enters them from the xylem via osmosis. This results in higher pressure in these tubes, which drives the solution towards the sink.

Mechanism of Sink:

At the sink end, the food is unloaded by active transport. Water also exits from the sieve tubes. The exit of water decreases the pressure in sieve tubes, which causes a mass flow from the higher pressure at the source to the now lowered pressure at the sink. In other words, the mass flow is caused by drops in pressure at the sink as the food and water molecules are removed.

Functions of Human Blood Circulatory System (cardiovascular system):

It transports nutrients, gases, hormones, and wastes to and from cells, helps fight diseases, and helps stabilize body temperature and pH to maintain homeostasis. Like other vertebrates, humans have a closed blood circulatory system (meaning that the blood never leaves the network of arteries, veins, and capillaries). The main components of the human blood circulatory system are the blood, the heart, and the blood vessels.

Composition of blood:

Blood is a specialized bodily fluid (considered a specialized form of connective tissue) that is composed of a liquid called blood plasma and blood cells suspended within the plasma. The weight of the blood in our body is about 1/12th of our body. The average adult has a blood volume of roughly 5 liters.

In a healthy person, plasma constitutes about 55% of the volume of the blood, and cells or cell-like bodies about 45% of the volume of the blood.

Separation of Plasma from blood:

Blood is taken from an artery and an anticoagulant (a chemical that inhibits blood clotting) is mixed with it. After about 5 minutes, plasma separates from blood cells, which settle down.

In a normal person, about 2-10 million red blood cells are formed and destroyed every second.

Macrophages (produced by monocytes) and neutrophils die in the process of killing the germs. Their dead cells accumulate and make the white substance called pus, seen at infection sites. 

Red blood cells. 

There are about 60-80 million people in the world who carry the beta-thalassemia, India, Pakistan, and Iran are seeing a large increase in thalassemia patients. To give an example, Pakistan alone has 250000 thalassemia patients that require blood transfusions for a lifetime.

(Source: The thalassemia International Foundation)

A total of 29 human blood group systems are now recognized by the International Society of Blood Transfusion (ISBT).

Several infectious diseases (such as AIDS, hepatitis B, hepatitis C, etc) can be passed from the affected donor to the recipient. Strict blood transfusion standards are observed e.g. Screening of donors' blood for the presence of germs etc.

Cardiac muscles are involuntary in action and are composed of branched striated cells, each with a single nucleus.

The heart is usually felt to be on the left side because the left chamber of the heart i.e. (the left ventricle) is stronger (it pumps blood to all body parts). 

The walls of the left ventricle are the thickest ones. These are about a half-inch thick. They have enough force to push blood into the body. This gives evidence that the structures of the parts of the heart are adaptive to their functions.

O-negative blood group.

Both atria are filled simultaneously. The contract together to pump the blood to both the ventricles. Similarly, both ventricles contract simultaneously to pump the blood out of the heart.

The blood in the pulmonary circulation is at a lower pressure than the blood in the systemic circulation. It gives sufficient time for gaseous exchange to occur in the lungs. 

Never.

The average human heart beats 70 times per minute. So, it would be at approximately 2.5 billion times during a lifetime of 66 years. In normal adults, the mass of the heart is 250-350 g, and the size is equal to a clenched fist.

Capillaries are so small that the red blood cells need to partially fold into bullet-like shapes in order to pass through them in single file.

The function of blood plasma:

Plasma is primarily water in which proteins, salts, ions, metabolites, and wastes are dissolved. Water constitutes about 90-92% of plasma, and 8-10% are dissolved substances.

Materials present in the water of plasma:

The materials present in the water of plasma can be divided into the following six categories.

1. The salts make up 0.9% of the plasma, by weight. More than two-thirds of this amount are sodium chloride (the table salt). Salts of bicarbonate are also present in considerable amounts. Ca, Mg, Cu, K and Zn are found in trace amounts. Changes in the concentration of a particular ion can create serious disturbances e.g. change in the pH of the blood. The normal pH of human blood is 7.4 and it is maintained within narrow limits. Any change in blood pH affects the reactions of the body.
2. Proteins constitute 7-9 % by weight of the plasma. Antibodies are produced by lymphocytes (a type of white blood cell), in response to antigens and then passed to plasma and lymph. They are a part of the body's immune system. Fibrinogen is a plasma protein that takes part in the blood clotting process. The protein prothrombin acts as a catalyst in the blood clotting process. Albumin proteins circulate in the blood and maintain the water balance of the blood. They do not let the water go out of their blood.
3. Organic nutrients in the blood include glucose, lipids, amino acids, etc. They enter the blood after being absorbed from the digestive system.
4. Plasma also contains nitrogenous waste products formed as a result of cellular metabolism. In cells, they are produced in the form of ammonia. Plasma carries ammonia to the liver where it is converted into different (less toxic) forms, which are then carried to the kidneys for removal.
5. Hormones, which work as an important part of the body's coordination system, are carried by blood plasma.
6. Respiratory gases CO₂ and O₂ are present in the plasma of the blood. O₂ is primarily carried by RBCs but small amounts of it are also carried as dissolved in plasma. Most of the CO₂ is carried by plasma. 

Types of Blood Cells:

1. Red blood cells (erythrocytes),
2. white blood cells (leukocytes)
3. platelets (thrombocytes)

Red Blood Cells (Erythrocytes):

These are the most numerous blood cells.

Amount of Red Blood Cells:

A cubic millimeter of blood contains 5 to 5.5 million of them in males and 4 to 4.5 million in females. These cells, when formed, have a nucleus.

Structure of Red Blood Cells (Erythrocytes):

In the RBCs of mammals, the nucleus, mitochondria, endoplasmic reticulum, etc, are lost when they get mature and before they enter the blood. About 95% of the cytoplasm of red blood cells is filled with hemoglobin, which transports O₂ and small amounts of CO₂. The remaining 5% consists of enzymes, salts, and other proteins. These cells once mature, do not divide. RBCs are biconcave and have an elastic cell membrane.

Size of Red Blood Cells:

The average diameter of erythrocytes is 08 µm.

Formation of Red Blood Cells:

In the embryonic and fetal life, they are formed in the liver and spleen. In adults, they are formed principally in the red bone marrow of short and flat bones, such as the sternum, ribs, and vertebrae.

The average life span of a red blood cell:

The average life span of a red blood cell is about four months (120 days) after which it breaks down in the liver and spleen by phagocytosis.

White Blood Cells (Leukocytes):

These blood cells are colorless, as they do not contain pigments. They are not confined to the bloodstream, as they also migrate out into the tissue fluid.

Amount of White Blood Cells:

There are 1 or 2 leukocytes for every 1000 RBCs. One cubic millimeter of blood contains 7000 to 8000 of them. They are much larger (two to three times) than the red blood cells.

The average life span of a white blood cell:

They have a life span of months or even years, but this depends on the body's needs.

Types of leukocytes:

There are 5 types of leukocytes which can be divided into 2 main types.

1. Granulocytes:

   Granulocytes are the leukocytes with granular cytoplasm. These include neutrophils, eosinophils, and basophils. They are formed in the red bone marrow.

   1. Neutrophils:

      Their nucleus is divided into 2-5 lobes. They destroy small particles by phagocytosis. They are 62% of the leukocytes and their average lifespan is 07 hours.

   2. Eosinophils:

      Their nucleus is bilobed and they provide defense against parasites: They are 2% of the leukocytes and their life span depends upon needs.

   3. Basophils:

      Their nucleus is bilobed and they prevent blood clotting by releasing an anticoagulant, heparin. They are also responsible for developing inflammatory responses when they rupture and release the inflammatory agent, the histamines. They are less than 1% of leukocytes and their life span depends upon needs.

2. Agranulocytes:

   Agranulocytes are leukocytes with clear cytoplasm. These include monocytes and lymphocytes (B & T lymphocytes). They are formed in the lymphoid tissue of the lymphatic system i.e. in lymph nodes, spleen, tonsils, adenoids, and thymus.

   1. Monocytes:

      Their nucleus may be rounded or lobe. They are 3% of leukocytes with a life span of 3 days.

   2. Lymphocytes:

      They have a large nucleus and are are responsible for the production of antibodies which target specific antigens present on pathogens. They are 32% of the Leukocytes and are the major component of the immune system. Lymphocytes include B cells (which become antibody-secreting plasma cells) and T cells (which mediate B cell activity)

Platelets (Thrombocytes):

They are not cells but are fragments of large cells of bone marrow, called megakaryocytes. They do not have any nucleus or any pigment.

Number of Platelets (Thrombocytes):

One cubic millimeter of blood contains 250,000 platelets. The average life span of a blood platelet is about 7 to 8 days.

Functions of Platelets (Thrombocytes):

Platelets help in the conversion of fibrinogen, a soluble plasma protein, into an insoluble form, fibrin. The fibrin threads entangle with the red blood cells and other platelets in the area of damaged tissue ultimately forming a blood clot.

Functions of human blood:

1. Blood is the major agent for the transport of materials in the body including nutrients, water, salts, and waste products. Hormones are also transported by the blood from the endocrine tissues to the target sites.
2. Respiratory gases; O₂ and CO₂ are transported by blood.
3. Blood helps in the body's defense against diseases.
4. Blood has particular proteins e.g. interferon (produced by the liver) and antitoxins (produced by blood cells). Such chemicals protect the body from nucleic acids and toxins from invading organisms.
5. Blood acts as a buffer to maintain the acid-base balance i.e. concentration of hydrogen and hydroxyl ions in the body.
6. Blood helps in maintaining the body's temperature and concentration of water and salts. Blood is also responsible for maintaining the amounts of chemicals in the body to constant or nearly constant levels. It thus helps in homeostasis.
7. Blood helps in the exchange of materials between blood and body tissue through blood capillaries.

Leukemia (blood cancer):

We know that cancer means the uncontrolled production of cells.

Signs and Symptoms of Leukemia (blood cancer):

Leukemia is characterized by the appearance of a great number of immature and abnormal white blood cells in the bone marrow and often in the spleen and liver.

Causes of Leukemia (blood cancer):

This is caused by a cancerous mutation in bone marrow cells or the lymph tissue cells and results in the uncontrolled production of white blood cells (leukocytes). The mutated bone marrow cells may spread throughout the body, so that white blood cells are produced in many other organs. These white blood cells are not completely differentiated and so are defective.

Types of Leukemia (blood cancer):

This disease may be of different kinds depending on the type of white blood cells, which are being produced at a faster than normal rate. There may be Neutrophilic leukemia, Eosinophilic leukemia, Basophilic leukemia, Monocytic leukemia, or Lymphocytic leukemia.

Treatment of Leukemia (blood cancer):

It is a very serious disorder, and the patient needs to change the blood regularly with the normal blood, got from donors. It can be cured by bone marrow transplant, which is in most cases effective, very expensive treatment.

Thalassemia (g. thalassa = sea; haem = blood):

It is also called Cooley's anemia by the name of Thomas B. Cooley, an American pediatrician (the physician who treats children).

Causes of Thalassemia:

It is a genetic problem due to mutations in the gene of hemoglobin.

Signs and Symptoms of Thalassemia:

The hemoglobin molecule in most cases of thalassemia does not have ß-chains in it. instead, F-chain is present (F: fetal hemoglobin). This is called ß-thalassemia and the patient cannot transport oxygen properly.

Treatment of Thalassemia:

The blood of these patients is to be replaced regularly, with normal blood. It can be cured by bone marrow transplant which is very expensive and does not give a 100% cure rate.

Capillaries. 

Functions of the components of blood:

Vascular surgery:

Vascular surgery is a field of surgery in which diseases of arteries and veins (like thrombosis etc) are managed by surgical methods.

Vascular surgeon:

The avascular surgeon treats diseases of all parts of the vascular system except that of the heart and brain.

Even though the heart chambers are continually bathed with blood, this does not nourish the heart muscles. The blood supply to the heart muscles is provided by the coronary arteries, which emerge from the base of the aorta. The heart muscles are drained by the coronary veins, which empty into the right atrium. The coronary arteries and veins are collectively called coronary circulation and it is a part of the systemic circulation. 

Aorta 

it was been …. major cause of sudden non-accidental deaths developing countries. 

Angina pectoris:

Angina pectoris, which means "chest pain occurs for reasons similar to those which cause a heart attack. But it is not as severe. The pain may occur in the heart left arm and shoulder. It is a warning sign that the blood supply to the heart muscles is not sufficient but the shortage is not enough to cause tissue death.

Approximately one-fourth of all myocardial infarctions are silent, without chest pain or other symptoms. A silent heart attack is more common in the elderly, in patients with diabetes mellitus, and after heart transplantation. 

Blood group systems:

Blood group systems are a classification of blood-based on the presence or absence of antigens on the surface of red blood cells.

Antigen:

An antigen is a molecule that can stimulate an immune response (antibody production etc). These antigens may be proteins or polysaccharides, depending on the blood group system.

Note:

A total of 29 human blood group sisters are now recognized by the International Society of Blood Transfusion (ISBT).

World Heart Day is held on 28th September every year throughout the world, its objective is to help people better understand the Risks of cardiovascular disorders. 

ABO Blood Group System:

It is the most important blood group system in humans. It was discovered by the Austrian scientist Karl Landsteiner, who found four different blood groups (blood types) in 1900. He was awarded the Nobel Prize in Medicine for his work.

Classification of ABO Blood Group System:

In this system, four different blood groups are distinct from each other based on specific antigens (antigen A and B) present on the surface of RBCs.

• Group A:

A person having antigen A has blood group A.

• Group B:

A person having antigen B has blood group B.

• Group AB:

A person having both antigens has the blood group AB.

• Group O:

A person having none of the A and B antigens has blood group O.

Rh Blood Group System (+ve & -ve blood group system):

In the 1930s, Karl Landsteiner discovered the Rh-blood group system. In this system, there are two blood groups i.e., Rh⁺ and Rh^- which are distinct from each other based on antigens called Rh factors (first discovered in Rhesus monkey), present on the surface of RBCs.

• Rh-positive:

A person having Rh factors has blood group Rh-positive.

• Rh-negative:

A person not having Rh factors has blood group Rh-negative.

Note:

Unlike the naturally occurring anti-A & anti-B antibodies of the ABO system, an Rh-negative person does not produce anti-Rh antibodies unless he or she is exposed to Rh-factor.

Blood transfusions in the ABO blood group system:

Blood transfusion is the process of transferring blood or blood-based products from one person into the circulatory system of another.

Requirement of Blood transfusions:

Blood transfusions can be life-saving in some situations, such as massive blood loss due to injury, or can be used to replace blood lost during surgery. People suffering from anemia, hemophilia, thalassemia, or sickle-cell disease may require frequent blood transfusions.

Cross Matching for Blood transfusions:

Transfusion of blood is done after confirming that no agglutination results in the blood of the recipient.

Agglutination:

Agglutination leads to the clumping of cells and clumped cells cannot pass through capillaries. For the confirmation of no agglutination, blood samples of donor and recipient are crossed-matched for compatibility. Antibodies of the recipient's blood may destroy the corresponding antigen-containing RBCes of the donor or the antibodies of the donor's blood may destroy the antigen-containing RBCes of the recipient.

Universal donors:

O blood group individuals are called universal donors because they can donate blood to the recipients of every other blood group.

Universal recipients:

AB blood group individuals are called universal recipients because they can receive transfusions from the donors of every other blood group

Blood transfusions in the Rh blood group system:

Rh-positive blood group can be transfused to the Rh-positive recipient because the recipient's blood already has Rh-antigens and it will not produce anti-Rh antibodies Rh-negative blood group can be transfused to Rh-negative because the donor's blood does not have Rh-antigen and the so recipient's blood will not produce anti-Rh antibody If an Rh-negative person receives Rh-positive blood, he she will produce antibodies against Rh-factors. Rh-negative blood can be transfused to an Rh-positive recipient, only if the donor's blood (Rh-negative) has never been exposed to Rh-antigens….

O-negative blood group. 

Human Heart:

The heart is a muscular organ responsible for pumping blood through the blood vessels by repeated contractions. The term cardiac means "related to the heart" The bulk of the walls of the heart chambers is made of cardiac muscles. In the human body, the heart is situated between the lungs, in the middle of the chest cavity (thorax) underneath the breastbone.

Pericardium:

The heart is enclosed in a sac known as the pericardium. There is a fluid, known as pericardial fluid, between the pericardium and the heart walls. It reduces friction between the pericardium and the heart, during heart contractions. Like birds and other mammals, the human heart consists of four chambers. The upper thin-wallet chambers are called the left and right atria (singular 'atrium'), and the lower thick-walled chambers are called the left and right ventricles. The left ventricle is the largest and strongest chamber in the heart.

chambers in the human heart: The human heart consists of four chambers.

Left and right atria: The upper thin-walled chambers are called the left and right atria (singular 'atrium').

Left and right ventricles:

The lower thick-walled chambers are called the left and right ventricles. The left ventricle is the largest and strongest chamber in the heart.

Blood flow through the chambers:

The human heart works as a double pump i.e., it receives deoxygenated (with less oxygen) blood from the body and pumps it to the lungs and, at the same time, it receives oxygenated (with more oxygen) blood from the lungs and pumps it to all the body. Inside heart chambers, the deoxygenated and oxygenated blood are kept separated. Here is a brief description of the circulation of blood inside the heart to show its double-pump mechanism.

Function of the right atrium:

The right atrium receives deoxygenated blood from the body via the main veins i.e., superior and inferior vena cava. When the right atrium contracts it passes the deoxygenated blood to the right ventricle.

The opening between the right atrium and the right ventricle is guarded by a valve known as the Tricuspid valve

Tricuspid valve:

Tricuspid valve (because it has 3 flaps). When the right ventricle contracts, the blood is passed to the pulmonary trunk, which carries blood to the lungs. The tricuspid valve prevents the backflow of blood from the right ventricle to the right atrium.

Semilunar valve:

At the base of the pulmonary trunk, the pulmonary semilunar valve is present which prevents the backflow of blood from the pulmonary trunk to the right ventricle.

The function of the left atrium:

The oxygenated blood from the lungs is brought by pulmonary veins to the left atrium. The left atrium contracts and pumps this blood to the left ventricle.

Bicuspid valve:

The opening between the left atrium and the left ventricle is guarded by a valve known as a bicuspid valve (because it has two flaps). When the left ventricle contracts, it pumps the oxygenated blood into the aorta, which carries the blood to all parts of the body (except the lungs). The bicuspid valve prevents the backflow of blood from the left ventricle to the left atrium. At the base of the aorta, the aortic semilunar valve is present which prevents the backflow of blood from the aorta to the left ventricle.

Collection of deoxygenated blood:

We see the right side of the heart collects the deoxygenated blood from the body and distributes it to the lungs.

Collection of oxygenated blood:

while the left side collects the oxygenated blood from the lungs and distributes it to the body.

Pulmonary circulation or circuit:

The pathway on which deoxygenated blood is carried from the heart to the lungs and in return oxygenated blood is carried from the lungs to the heart is called pulmonary circulation or circuit.

Systemic circulation or circuit:

Similarly, the pathway on which oxygenated blood is carried from the heart to the body tissues and in return deoxygenated blood is carried from the body tissues to the heart is called systemic circulation or circuit.

Heartbeat:

The relaxation of heart chambers fills them with blood and the contraction of chambers propels the blood out of them. The alternating relaxations and contractions make up the cardiac cycle and one complete cardiac cycle makes one heartbeat.

Steps involved in the complete cardiac cycle:

The complete cardiac cycle consists of the following steps.

Cardiac diastole:

The atria and ventricles relax and blood is filled in the aria This …. is called cardiac diastole

Atrial systole:

….

Ventricular Systole:

Now both ventricles contract and pump the blood towards …. and lungs. The period of ventricular contraction is called …. Systole.

The duration of one heartbeat:

In one heartbeat, diastole lasts about 0.4 sec, atrial systole …. about 0.1 sec, and ventricular systole lasts about 0.3 sec.

Lubb-dubb:

When ventricles contract the tricuspid and bicuspid valves …. "lubb" sound is produced. Similarly, when ventricles relax, the semilunar …. closes, and a "dubb” sound is produced. "Lubb-dubb" can be heard with the help of a stethoscope.

Heart rate and Pulse rate:

The heart rate is the number of times the heartbeats per minute. A resting heart rate anywhere between 60 and 90 (70 is average) is considered in the normal range. The heart rate fluctuates a lot depending on factors such as activity level and stress level.

Measurement of Heart rate and Pulse rate:

The heart rate can be measured by feeling the pulse. Pulse is the rhythmic expansion and contraction of an artery as blood is forced through it by the regular contractions of the heart. The pulse can be felt in the areas where the to the skin for example at the wrist, neck, groin, or top of the foot. Most commonly, people measure their pulse on their wrist.

Blood vessels:

The third part of the blood circulatory system is the blood vessels, which function to transport blood throughout the body. The most important vessels in the system are the arteries, veins, and capillaries.

The function of Arteries:

Arteries are the blood vessels that carry blood away from the heart. In adults, all arteries except the pulmonary arteries, carry oxygenated blood.

 Structure of an artery:

Their structure shows that arteries are well adapted to their function Layers of an artery: The walls of an artery are composed of three layers.

1. Tunica externa:

The outermost layer is known as the tunica externa and it is composed of connective tissue.

2. Tunica media:

The middle layer is the tunica media and is made up of smooth muscles and elastic tissue.

3. Tunica intima:

The innermost layer is the tunica intima and is made up of mainly endothelial cells

The function of Lumen:

The hollow internal cavity in which the blood flows is called the lumen.

Arterioles:

When arteries enter body organs, they divide into smaller vessels known as arterioles. The arterioles enter tissues and divide into capillaries.

The function of Capillaries:

Capillaries are the smallest blood vessels, which are formed by the divisions of arterioles. The exchange of materials between blood and tissue fluid is carried out through the capillaries.

Structure of Capillaries:

The walls of capillaries are composed of only a single layer of cells, the endothelium. This layer is so thin that molecules such as oxygen, water, and lipids can pass through them and enter the tissue fluid. Waste products such as carbon dioxide and urea can diffuse from tissue fluid into the blood.

Note:

Capillaries are so small that the red blood cells need to partially fold into bullet-like shapes to pass through them in a single file.

The function of Veins:

A vein is a blood vessel that carries blood toward the heart. In adults, all veins except the pulmonary veins, carry deoxygenated blood. Veins are also well adapted to their function.

Structure of Veins:

The walls of the vein are composed of the same three layers as are present in the artery wall. The tunica externa and the tunica intima have the same composition, but the tunica media of a vein is comparatively thin as compared to that of an artery. It has fewer smooth muscles and elastic tissue. The lumen of the veins is broader than that of arteries.

The function of Valves:

In a tissue, capillaries join to form small venules, which join to form veins. Most veins have flaps called valves that prevent the backflow of blood.

Vascular surgery:

Vascular surgery is a field of surgery in which diseases of arteries and veins (like thrombosis etc) are managed by surgical methods. Avascular Surgeon treats the diseases of all parts of the vascular system except that of the heart and brain.

Comparison of arteries, capillaries, and veins:

The general plan of human blood circulatory system:

Many scientists worked for discovering the facts about the circulation of blood in the human body. Two important scientists who revealed much knowledge of the blood circulatory system were Ibn-e-Nafees and William Harvey. Ibn-e-Nafees (1210-1286) was a physician and he is honored as the first scientist who described the pathway of blood circulation. William Harvey (1578. 1657) discovered the pumping action of the heart and the pathway of blood in major arteries and veins.

The Arterial System:

Functions of pulmonary arteries:

The large pulmonary trunk emerges from the right ventricle and divides into the night and left pulmonary arteries, which carry the deoxygenated blood to the right and the left lungs.

Functions of the aorta:

The oxygenated blood leaving the left ventricle of the heart is carried in a large artery, the aorta. The aorta ascends and forms an aortic arch. The arch curves left and descend interiorly into the body. From the upper surface of the aortic arch, three arteries emerge, which supply blood to the head, shoulders, and arms. As the aorta passes down through the thorax, it becomes the dorsal aorta. The dorsal aorta gives off many branches and the important ones are listed here.

The function of intercostal arteries:

Several intercostal arteries supply blood to the ribs.

The function of celiac artery and the superior mesenteric artery:

The celiac artery and the superior mesenteric artery supply blood to the digestive tract.

The function of the hepatic artery:

The hepatic artery supplies blood to the liver.

The function of renal arteries:

Inferior to these are a pair of renal arteries that supply the kidneys.

The function of gonadal arteries:

The gonadal arteries serve the gonads.

The function of inferior mesenteric artery:

Just below the gonadal arteries is the inferior mesenteric artery, which serves a part of the large intestine and rectum.

The function of iliac arteries:

Then the aorta divides into two common iliac arteries, each of which divides into an internal iliac artery, and an external iliac artery. Each external iliac becomes the femoral artery in the upper thigh. It gives branches to the thigh, knee, shank, ankle, and foot.

The Venous System:

The function of pulmonary veins:

The veins from the lungs, called pulmonary veins return the oxygenated blood to the left atrium of the heart.

The function of superior vena cava and the inferior vena cava:

Two major veins i.e. the superior vena cava and the inferior vena cava, carrying the deoxygenated blood from the rest of the body, empty into the right atrium. The superior vena cava forms when different veins from the head, shoulders, and arms join together. From the legs, the deoxygenated blood is returned to the heart by many veins which empty into the inferior vena cava.

The function of femoral vein:

Veins carrying blood from the calf, foot, and knee join together to form the femoral vein It empties into the external iliac vein which joins with the internal iliac, and both empty into the common iliac vein. The right and left common iliac veins to join to form the inferior vena cava. Many short veins empty into the inferior vena cava, among these are the hepatic, renal veins, and gonadal veins.

The function of the hepatic portal vein:

All the veins coming from the stomach, spleen, pancreas, and intestine drain into the hepatic portal vein, which carries the blood to the liver. From the liver, a hepatic vein carries blood and empties into the inferior vena cava, Function of renal veins: The two renal veins carry blood from the kidneys while the two gonadal veins carry blood from gonads to the inferior vena cava. In the thoracic cavity, the inferior vena cava also receives veins from thoracic walls and ribs.

Difference between Atherosclerosis and arteriosclerosis:

Atherosclerosis:

Atherosclerosis is a disease affecting arteries. It is commonly referred to as a "narrowing" of the arteries. It is a chronic disease in which there is an accumulation of fatty materials, abnormal amounts of smooth muscles, cholesterol, or fibrin in the arteries. When this condition is severe, the arteries can no longer expand and contract properly, and the blood moves through them with difficulty. The accumulation of cholesterol is the prime contributor to atherosclerosis. It results in the formation of multiple deposits called plaques within the arteries. Plaques can form blood clots called thrombi within arteries. If a thrombus dislodges and becomes free-floating, it is called an embolus.

Arteriosclerosis:

Arteriosclerosis is a general term describing any hardening of arteries. It occurs when calcium is deposited in the walls of arteries. It can happen when atherosclerosis is severe. 

Cardiovascular disorder:

The diseases that involve the heart or blood vessels (arteries and veins) are collectively called cardiovascular disorders. These diseases have similar causes, mechanisms, and treatments.

Risk factors that lead to cardiovascular disorders:

The risk factors that lead to cardiovascular disorders include advanced age, diabetes, high blood concentration of low-density lipids (e.g. cholesterol) and triglycerides, tobacco smoking, high blood pressure (hypertension), obesity, and a sedentary lifestyle.

Preventing cardiovascular disorders:

There is therefore increased emphasis on preventing cardiovascular disorders by modifying risk factors, such as healthy eating, exercise, and avoidance of smoking.

Myocardial Infarction (heart attack):

It is more commonly known as a heart attack and is a medical condition that occurs when the blood supply to a part of the heart is interrupted and leads to the death of some cells of the heart muscles.

Causes of Myocardial Infarction (heart attack):

A heart attack may be caused by a blood clot in coronary arteries. It is a medical emergency and the leading cause of death for both men and women all over the world. The term myocardial infarction is derived from myocardium (the heart muscle) and infarction (tissue death).

Symptoms of Myocardial Infarction (heart attack):

Severe chest pain is the most common symptom of myocardial infarction and is often described as a sensation of tightness, pressure, or squeezing. Pain radiates most often to the left arm, but may also radiate to the lower jaw, neck, right arm, and back Loss of consciousness and even sudden death can occur in myocardial infarction.

Treatments of Myocardial Infarction (heart attack):

Immediate treatment for suspected acute myocardial infarction includes oxygen supply, aspirin, and a sublingual tablet of glyceryl trinitrate. Most cases of myocardial infarction are treated with angioplasty (mechanical widening of a narrowed or obstructed blood vessel) or bypass surgery (surgery in which arteries or veins from elsewhere in the patient's body are grafted to the coronary arteries to improve the blood supply to heart muscles).

Prevention of Myocardial Infarction (heart attack):

There is therefore increased emphasis on preventing cardiovascular disorders by modifying risk factors, such as healthy eating, exercise, and avoidance of smoking.

Myocardial infarction in Pakistan:

According to a survey cardiovascular disorders were reported as the cause of 12% of the adult deaths in Pakistan (Source: Federal Bureau of Statistics of Pakistan) Hypertension (blood pressure higher than normal) is the most common risk factor for cardiovascular disorders in Pakistan and there are over 12 million hypertension patients in Pakistan. Furthermore, 85% of patients in rural areas are unaware of their hypertension. Pakistan is among the top 10 world nations for high numbers of people with diabetes. About 10% of our population is diabetic. According to the World Health Organization, in Pakistan 1 in 7 urban adult males is obese. Among obese people, 22% are male, 38% are females (24-44 years) and 40% are females (45-64 years).