Blood, Heart, and Blood Vessels ANAT 2

Three interrelated components of the cardiovascular system…

The blood, heart, and blood vessels

How does blood contribute to homeostasis?

By transporting respiratory gases, nutrients, and hormones to and from your body’s cells. It helps regulate body pH and temp, and provides protection through it’s clotting mechanisms and immune defenses.

How thick is blood?

Blood is thicker than water

What is blood?

5 quarts or 5 liters of specialized fluid, CT composed of cells (45%) suspended in a salt-water and protein solution called blood plasma (55%). Temperature is slightly warmer than core body temp

How much plasma is in a tube of centrifuged blood?

55%

What is the “Buffy coat” composed of?

White blood cells(leukocytes) and platelets

How much red blood cells (RBCs) are in tube of centrifuged blood?

45%

What is plasma?

It is 92% water, with dissolved solutes consisting mostly of various proteins, electrolytes, and gases

What is hemocrit or Hct?

It is the normal red blood cell (RBC) mass which is inbetween 40-45% by volume and corresponds to 4-6X10^6/mm³

What’s the ratio between the difference of RBCs compared to WBCs?

700:1

What are megakaryocytes?

They are huge cells that spliter into 2000 to 3000 fragments while still in the red bone marrow.

What is a platelet?

Each fragment is enclosed by a piece of the plasma membrane. They are more numerous than WBCs, but have a shorter life span (5-9 days) and they don’t have much mass. They appear as little specks interspersed amoung the many red cells

What is hematopoiesis?

The process by which the formed elements of blood develop

What is erythropoiesis?

A part of hematopoiesis that deals with the production of RBCs. Erythropoiesis increases when states of hypoxia (O2 defincieny) stimulates the kidneys to release the hormone erythropoietin (EPO)

Mature RBS dont have what?

A nucleus or any protein making machinery and are destined to die in about 120 days. In a sense they are not really cells, but remnants of cells with a very specific purpose to carry O2 to the tissues of the body.

Red blood cells (RBCs) shape

Bi-concave disc, helps increase cell surface area and gives them a high oxygen carrying capacity; because they lack mitochondria, they don’t use any of the oxygen they carry. Allows them to deform and fit in small capillary beds

The rate of erythropoiesis is measured by the number of immature RBCs called…

Reticulocytes or retics

What is hemoglobin (Hgb)?

A protein molecule adapted to carry O2 (CO2 as well) and each RBC contains 280 million molecules of Hgb. A Hgb molecule consists of 4 large globin proteins (2 alpha and beta chains), each embedded an iron-containing heme center

What is anemia?

A condition of insufficient RBC’s or hemoglobin (quality or quantity). Most often results of low iron intake, hemolysis, autoimmune disease, blood loss, or lack of production in bone marrow

What is polycythemia?

A condition of excess numbers of RBCs. It occurs in response to hypoxia(natural “blood doping” is training at high altitude), shots of EPO (illegal “doping”), smoking (COPD), or dehydration

Iron deficiency anemia

Most common anemia in the US and affects primarily menstruating women

Hemorrhagic anemia

Result of precipitous blood loss, and results in an equal decrease in Hct, Hgb content, and RBC count

What is Sickle-cell disease (SCD)?

It is an autosomal recessive disorder. A genetic defect in the primary DNA sequence leads to production of a faulty Hgb chain, and the RBCs that take on a rigid sickle-shape. Sickling decreases the cell’s flexibility and results in a variety of complications; life expectancy is shortened

Unlike RBCs what do white blood cells (WBCS or leukocytes) have…

A nuclei and a full complement of other organells- but they do not contain the protein Hgb

Neutrophils

60-70% of all leukocytes, they are phagocytic cells and destroy bacteria

Eosinophils

2-4% of all leukocytes. They are characterized by their large red granules. phagocytize antigen- antibody complexes. Also destroy some types of parasitic worms. Their numbers increase slightly with parasitic infection and they have also been associated with the development of allergies.

Basophils

1/2 -1% of all leukocytes. They are the third type of granulocyte; they contain a large, dark blue, histamine-containing granules. Normally play a role in inflammatory responses. Release histamine and other chemical defenses, play a role in allergic reactions. When basophils leave the bloodstream and enter the tissues, they are called MAST cells.

Lymphocytes

20-25% of all leukocytes. The last of the 5 types of WBCs and quite different. They don’t have granules or phagocytize, their cytoplasm is sparse compared to their very large nucleus, and they develop from a different precursor stem cell. Several subtypes exist, two subtypes, B cells and T cells, make antibodies as part of the specific immune response. Other subtypes kill a wide variety of microbes. Others are helper cells, aiding in antibody production. They act as responders to very specific foreign antigens.

Monocytes

3-8% of all leukocytes. They are NOT granulocytes, they come from the same immediate precursor cell as the 3 granulocytes (the myeloid stem cell). They are more numerous in the peripheral tissues where they act as “fixed” phagocytes. They leave the bloodstream and enter the tissues, where they are called macrophages. Primarily act as phagocytic cells.

Granulocytes include…

neutrophils, eosinophils, and basophils

Agranulocytes include…

monocytes and lymphocytes

What is phagocytes main role in the body?

To fight bacterial infections

What is a polymorphonucleocyte or PMN?

A neutrophil, they are granulocytes with a pinkish cytoplasm, and they are one of the two major phagocytes in the body

What is chemotaxis?

Chemicals released by microbes and inflamed tissues attract phagocytes

Lymphocytosis

An increased number of circulating white cells (normal range 20-30%) often represents an acute viral infection.

Leukocytosis

Any WBC count > 10,000/mm³ and usually can indicate an infectious process or a cancer

Leukopenia

Any WBC count < 5,00/mm³ and usually indicates a severe disease (AIDS, bone marrow failure, severe malnutrition, or chemotherapy)

What is the major protein in plasma?

It is albumin; also has many clotting proteins, antibodies, and enzymes.

What is the other important group of plasma proteins?

Globulins, there is several types: a (alpha) they carry bilirubin and steroids, b (beta) they carry copper and iron, and g (gamma) they are immunoglobulins (antibodies) made by activated B lymphocytes called plasma cells. Globulins control blood osmotic pressure and act as carrier molecules.

Three mechanism to reduce blood loss

Vascular spasm, formation of a platelet plug, blood clotting (coagulation)

Hemostasis is…

A sequence of responses that stops bleeding

A vascular spasm occurs when

Damaged blood vessels constrict

To form a platelet plug

Platelets adhere to damaged endothelium

2 Pathways to activate the system

Extrinsic pathway and intrinsic pathway

The extrinsic pathway…

Has few steps and occurs rapidly, often within seconds, once the protein “tissue factor” (TF) leaks into the blood

The intrinsic pathway…

More complex and occurs more slowly in response to damage to endothelial cells or phospholipids released by activated platelets

Universal blood recipients…

Type AB because they have neither anti- A nor anti-B antibodies in their serum that would destroy transfused RBCs

Universal blood donors…

Type O individuals because their RBCs have no antigens on the cell surface that can potentially react with the recipient’s serum

Blood serum

the liquid part of the blood is allowed to coagulate

Where is the heart located?

In the mediastinum and lies medially between the two lungs and the pleural membranes that cover them.

Position of the hearts base and apex

The base of the heart is tipped medially and posteriorly, while the apex projects inferiorally and laterally

Fibrous pericardium

is very dense and non-flexible connective tissue that helps protect and anchor the heart

Inner serous pericardium

is subdivided into a parietal layer which adheres to the outermost fibrous layer and a visceral layer which is also view as the outer surface of the heart wall.

Thin fluid around heart

Pericardial fluid is the space between the visceral and parietal pericardium

The superifical epicardium layer of the heart…

the thin, transparent outer layer of the heart wall, is also called the visceral layer of the serous pericardium

The middle myocardium layer of the heart…

the thick, middle layer is composed of cardiac muscle

The deep endocardium layer of the heart…

is a simple squamous epithelium (known throughout the circulatory system as “endothelium”)

How many chambers does the heart have?

The heart has 4 chambers.

2 upper chambers, right and left atria

2 lower chambers, right and left ventricles

The right side of heart…

Consists of right atrium and right ventricle, taking venous (non-oxygenated) blood from the body and pumps it to the lungs for oxygenation

The left side of the heart…

Consists of the left atrium and left ventricle, taking freshly oxygenated pulmonary blood and pumping it systemically (to the body)

How does blood always flow in the heart?

From a high pressure area to a low pressure area.

Atrioventricular Valve (AV)

opens to allow blood flow from the atria into the ventricles

The right AV valve (also called the tricuspid valve because of its three leaflets or cusps)

opens into the right ventricle (right lower chamber)

The left AV valve (also called the bicuspid or mitral valve)

opens into the right ventricle (right lower chamber)

Outflow (semilunar-SL) valves

opens to allow blood to flow from the ventricles into the outflow vessels. these are positioned at the entrance to the outflow vessels leading into the pulmonary and systemic circulation.

The right outflow valve (pulmonary valve)

opens into the pulmonary trunk

The left outflow valve (aortic valve)

opens into the aortic arch

What do chordae tendinae do?

They anchor the valves and prevent the reversal of AV valves into the atria during strong ventricular contractions

Systemic circuit

ejects blood into the aorta, systemic arteries, and arterioles and is powered by the left side of the heart

Pulmonary circuit

ejects blood into the pulmonary trunk and is preferred by the right side of the heart

Where do coronary veins connect?

All collect into the coronary sinus on the back of the heart

How do cardiac muscle cells connect and communicate?

They connect and communicate with neighboring cells through gap junctions in intercalated discs

Sinoatrial (SA) node location and function

Present in the right atrium(upper right side), close to the superior vena cava opening, sends impulses

Atrioventricular (AV) node

Located closer to the AV valve, contains the atrioventricular (AV) Bundle (BUNDLE OF HIS)

Atria contraction

Both contract simutaneously

Ventricle contraction

Both contract together

Atria and ventricle contractions

Never contract at the same time

Cardioacceleratory center

Found in the medulla of the brain, sympathetic active increases HR and the strength of myocardiac contraction to increase blood flow out of the heart (ejection fraction).

Cardioinhibitory center

Also found in the medulla of the brain, parasympathetic fibers in the vagus nerve (CN X) release acetylcholine that decreases the heart rate and strength of the contraction.

Arteries

carry blood away from the heart

Capillaries

site of nutrient and gas exchange

Veins

carry blood towards the heart

Venules

they are small veins

Tunica interna (intima)

It is also named the endothelium and is made up of simple squamous epithelium. It rests on the basement membrane and separated from the next layer by internal elastic lamina.

Tunica media

is chiefly composed of smooth muscle that regulates the diameter of the vessel lumen. it separated from the next layer by external elastic lamina

Tunica externa

the tunica externa helps anchor vessel to surrounding tissue through use of elastic and collagen fibers. it contains vasa vasorum.

Elastic arteries

these are the largest arteries, and their functional name is conducting arteries; best exemplified by the garden hose-sized aorta

Muscular arteries

medium-sized, also known as distributing arteries and have more smooth muscle in their tunica media.

Arterioles

known as resistance vessels, deliver blood to capillaries and have the greatest collective influence on both local blood flow and on overall blood pressure. by changing the diameter these can impact blood pressure

Capillaries

exchange vessels are the only sites in the entire vasculature where gases, water and other nutrients are exchanged

Venules and veins

capacitance vessels have much thinner walls than corresponding arterioles and arteries of similar size

Continous capillaries

the most common with endothelial cells forming a continous tube, interrupted only by small intercellular clefts.

Fenestrated capillaries(fenestra=windows)

found in the kidneys, villi of small intestines, and endocrine glands are much more porous

Sinusoids

form very porous channels through which blood can percolate, e.g., in the liver and spleen

Thoroughfare channel

directly connects arteriole to a venule. when precapillary sphincters are closed, it delivers blood directly to venous end without exchange, when tissues do not require much nutrients

Precapillary sphincters

At the metarteriole-capillary junction, the distal-most muscle cells form these, and they monitor and regulate blood flow into the capillary bed

Vein structure

have thinner walls, less muscle and elastic tissue, and are designed to operate at much lower pressure

Skeletal muscle pump

uses the action of muscles to milk blood in one direction(due to valves)

Respiratory pump

uses the negative pressures in the thoaracic and abdominal cavities generated during inspiration to pull venous blood towards the heart

Blood reservoirs

systemic veins and venules contain a large percentage of the blood volume, they function as blood reservoirs from which blood can be diverted quickly if needed