Chapter 12

Circulatory system

Heart, blood vessels, and blood

Cardiovascular System

Heart & blood vessels

Hematology

Study of blood

• Plays numerous roles in maintaining homeostasis

• Excessive loss of blood is fatal

Functions of Blood

1. Transport

• Carries oxygen from the lungs to the tissues

  • Picks up carbon dioxide from the tissues → lungs for removal

• Picks up nutrients from the digestive tract, distributes
  them to all tissues

• Carries metabolic waste to the kidneys for removal

• Carries hormones to target cells

• Transports stem cells to their destination

2. Protection

• White blood cells destroy microorganisms & cancer cells

• Antibodies & other blood proteins neutralize toxins & help destroy pathogens

• Plays a role in inflammation, limiting the spread of
  infection & promotes repair

• Platelets initiate blood clotting to minimize blood loss

3. Regulation

• Helps maintain optimal fluid balance; it absorbs or
  exudes fluid

• Blood proteins stabilize the pH of extracellular fluid by
  buffering acids & bases

• Helps regulate body temp through shifts in blood flow

  • routes blood to the skin for heat loss

Blood

a liquid connective tissue composed of plasma and
formed elements

Plasma

clear, light-yellow fluid
• Forms the extracellular matrix
• 55% of blood by volume

A mixture of

• Water, proteins, and nutrients

• Nitrogenous wastes, hormones, and gases

Formed Elements

Membrane-enclosed cells and cell fragments

• EX: red blood cells (RBC), white blood cells (WBC),platelets

Blood measurements

Most adults have 4 to 6 L
• When spun in a centrifuge, dense formed elements
are forced to the bottom, plasma rises to the top
• Red blood cells are the densest
• Hematocrit – percentage of RBCs to total blood volume; typically
35 to 50%
• White blood cells and platelets are in the middle buffy
coat

Serum

Fluid remaining when blood clots and solids are removed

Plasma Proteins

most abundant of the solutes in plasma

Roles:

• Clotting and immune defense

• Transport of other solutes

  • iron, lipids, hormones

3 major categories of plasma proteins:

1. albumin

2. globulins

3. fibrinogen

Albumin

Smallest and most abundant plasma protein
• Transports various solutes
• Buffers the pH of the plasma
• Maintains optimal viscosity and osmolarity of the blood

viscosity - thickness

osmolarity- Concentration of particles in the blood that cannot pass
through the vessel walls

Globulins

Roles in immunity, clotting, and transport

Fibrinogen

a soluble precursor of fibrin, which is a sticky protein that forms the framework of a blood clot

• The liver makes almost all of the plasma proteins

  • Exception: the antibodies

How is the blood produced?

Blood must be continually replaced
• continually lost from bleeding and as blood cells grow old
and die
• Plasma components are consumed or excreted from the body.

Hemopoiesis

the production of the formed elements of
blood
• Occurs in the red bone marrow
• Hematopoietic stem cells (HSCs) can give rise to all formed
elements

Erythrocytes

(red blood cells, RBCs)

Functions:

1. Pick up oxygen from the lungs & transport it to the
   tissues

2. Pick up carbon dioxide from the tissues and unload it in
   the lungs

Severe deficiency can be fatal within minutes

• EX: massive hemorrhaging

Most abundant of the formed elements
• Determines amount of oxygen the blood can carry

Hematocrit (packed cell volume, PCV)

Percentage of blood volume of RBCs
• Higher in men

• Men: 45 to 52%;

• women: 37 to 48%
  • Androgens stimulate RBC production
  • Blood loss during menstruation

Hemoglobin

Reason blood is red

• Red, iron-containing protein

Consists of four polypeptide chains called globins

• 2 alpha (α) chains

• 2 beta (β) chains

• Each has a nonprotein component called heme

  • Carbon-nitrogen ring with iron atom at the center

Hb concentration is normally 13 to 18 g/dL in men, and
12-16 g/dL in women

Sickle-cell disease

Must inherit two defective copies of the Hb gene called
hemoglobin S (HbS)

Erythropoiesis

Production of RBCs

• Is one aspect of hemopoiesis (production of all formed elements)

• Originate from hematopoietic stem cells (HSCs) in the bone marrow

  • HSCs give rise to more specialized cells, colony-forming units (CFUs)

Bilirubin

a yellow-green pigment

• jaundice

Hemolysis

pass through small blood vessels, often in the spleen

Antigens

Occur on the surface of cells
• Enable the body to distinguish ‘self’ from ‘foreign’
• If the body detects an antigen of foreign origin, it activates
an immune response
• Includes the production of antibodies, which cause agglutination
– the clumping of antibody and antigen molecules

Blood Types

1. Type A person has anti-B antibodies

2. Type B has anti-A antibodies

3. Type O has both antibodies

4. Type AB has neither anti-A nor anti-B antibodies

Rh blood group

• Rh-positive people have Rh antigens on their RBCs
• Rh-negative people have no Rh antigens on their RBCs

Hemolytic disease of the newborn (erythroblastosis fetalis)

During future pregnancies with an Rh+ fetus, antibodies diffuse through placenta and attack RBCs in fetal blood

• In severe cases, baby is given an exchange transfusion to
  replace all of its blood

Leukocytes

(white blood cells, WBCs)
• Protect us from pathogens
• Spend only a few hours in the bloodstream;

they migrate through capillary walls

spend the rest of their lives in connective tissue

Vary in form and function
• Retain organelles throughout their life
• Include structures involved in protein synthesis
• Proteins are needed for a wide variety of functions
EX: lysosomal enzymes that enable pathogen digestion

Leukocytes are distinguished by?

Relative size and abundance
• Size and shape of nuclei
• Presence or absence of cytoplasmic granules and the
staining properties of the granules
• Their functions

Leukocyte granules

Some lysosomes are called nonspecific granules

• Some granules are called specific granules

  • neutrophils, eosinophils, and basophils

  • AKA granulocytes

• Monocytes and lymphocytes are called agranulocytes

Neutrophils

Granulocyte
• Most abundant of the WBCs
• 60 to 70% of the circulating WBCs
• Violet-staining, multilobed nucleus
• Usually 3 to 4 lobes connected by thin strands
• Cytoplasm has pale granules
• Attracted to areas of infection or inflammation
• Phagocytize and digest bacteria

Release toxic chemicals that kill bacteria
• The chemicals kill the neutrophils, too, so they have a
short lifespan
• Produce webs called neutrophil extracellular traps (NET)
that consist of proteins and threads of DNA.
• Pathogen presence triggers extrusion of NET, which traps
and kills the invaders.
• Dead neutrophils are the main component of pus
• Elevated count may indicate an infection

Eosinophils

Granulocytes
• Make up only 2 to 4% of circulating WBCs
• Large bilobed nucleus
• Cytoplasm has large pink-orange specific granules

Secrete chemicals that destroy large parasites
• EX: hookworms
• Dispose of antigen-antibody complexes
• Their numbers rise in:
• Parasitic infections, allergies and diseases of the spleen and nervous system

Basophils

Granulocytes
• The rarest of the WBCs
• Make up 0.5 to 1% of circulating WBCs
• Dark violet granules
• Large, pale U- or S-shaped nucleus

Secrete

• histamine, a vasodilator

• heparin, an anticoagulant (inhibits blood clotting)

Important in:
• Allergy and inflammation
• Attracting neutrophils to infection sites

Lymphocytes

Agranulocytes
• Second most common WBC
• Make up 25 to 33% of circulating WBCs
• Their dark violet nucleus almost completely fills the cell
• Light blue cytoplasm forms a ring around the nucleus
• There are subclasses with distinct immune functions; their
numbers rise in diverse infections and immune responses

Monocytes

Agranulocytes
• The largest of the WBCs, with a large nucleus
• Migrate from blood into connective tissues, where they
transform into larger cells called macrophages
• Destroy dead cells, microorganisms, foreign material
• Alert immune system to invading pathogens
• Numbers are increased in inflammation and viral infections

• 3% to 8%

Leukopoiesis

production of white blood cells

Some HSCs differentiate into distinct types of colony-forming
units, which then produce any of three cell lines:

1. Myeloblast line produces granulocytes

2. Monoblast line produces monocytes

3. Lymphoblast line produces lymphocytes

Anemia

RBC or hemoglobin deficiency

Three main causes:

1. Reduced erythropoiesis

• Iron-deficiency anemia – not enough iron in the diet

• Pernicious anemia – autoimmune; destroys stomach tissue that
  normally produces intrinsic factor

• Kidney disease – inadequate erythropoietin production

2. Rapid RBC destruction

• Hemolytic anemia – RBCs are destroyed faster than they are
  made

3. Hemorrhage

• Hemorrhagic anemia – caused by trauma, hemophilia, ruptured
  aneurysm, heavy menstruation

Hypoxia

deficiency of oxygen in the tissues

Polycythemia

too many RBCs

Leukopenia

too few WBCs

Leukocytosis

too many WBCs

• Differential WBC count – blood test that measures the
  relative counts of the different types of WBCs

Leukemia

Cancer of the WBCs
• Classified as myeloid or lymphoid, chronic or acute
• Myeloid leukemia – uncontrolled granulocyte production
• Lymphoid leukemia – uncontrolled lymphocyte or monocyte
production
• Acute – rapid onset and progression; can cause death within a few
months
• Chronic – develops slowly

Complete blood count

blood test that includes:
• Hematocrit, hemoglobin concentration, total RBC, WBC
and platelet counts
• RBC size

Differential WBC count

what percentage of the WBCs is made up of the individual WBC types

Platelets

Circulating fragments of bone marrow cells called
megakaryocytes

• Formed elements but not cells

• Second most abundant formed element after RBCs

Structure:

Have a complex internal structure that includes:
• Lysosomes, mitochondria, cytoskeleton
• Granules filled with platelet secretions
• Channels that open to the platelet surface (open canalicular
system)

Platelet Functions

1. Secrete vasoconstrictors

• Cause spasmodic contraction of broken vessels

• Help reduce blood loss

2. Stick together to form platelet plugs

• Temporarily seal breaks in injured vessels

3. Secrete clotting factors

• promote clotting

4. Initiate formation of a clot-dissolving enzyme

• Dissolves blood clots that are no longer needed

5. Secrete growth factors

• Stimulate mitosis in fibroblasts and smooth muscle

• Help maintain and repair blood vessels

Thrombopoiesis

Platelet production

• Some hematopoietic stem cells differentiate into
  megakaryocytes

  • Huge cells (visible to the naked eye)

  • Have multiple chromosomes

• 25 to 40% of platelets are stored in the spleen

  • The rest circulate; live for 5 or 6 days

Proplatelets

Arise from processes extending from megakaryocyte into blood
vessel lumen

• Further fragment into individual platelets

Hemostasis

Control (cessation) of bleeding

3 stages:

1. Vascular Spasm

• Prompt constriction of the broken vessel

• Narrows the opening and reduces blood loss

• Triggered partly by serotonin, a vasoconstrictor secreted by
  platelets

2. Platelet Plug

• Sticky mass of platelets that close small breaks in vessel

• Platelets adhere to collagen of broken vessel walls

• Spiny pseudopods adhere other platelets, vessel wall

• Contracts to pull wall together

3. Coagulation (clotting)

• The last but most effective defense against bleeding

• Involves many chemical reactions and many clotting factors

  • Most function as enzymes that activate other enzymes in a cascading chain that ultimately produces fibrin from fibrinogen

Platelet-derived growth factor (PDGF)

After the leak is sealed, platelets secrete

• When clot no longer needed, platelets secrete a protein
  that initiates a reaction chain that leads to plasmin, a
  fibrin-digesting enzyme

Coagulation

formed elements are stuck together by fibrin

Agglutination

RBCs stuck together by antibody molecules

Hemophilia

• Hereditary lack of a single protein in the cascade
• Inability to clot and control bleeding
• Most patients lack factor VIII

Thrombosis

Abnormal clotting of blood in an unbroken vessel
• Causes most strokes and heart attacks

Thrombus (clot)

May grow large enough to obstruct vessel

Embolus

A piece of a thrombus that breaks off and travels in bloodstream
• May lodge in an artery and block blood flow
• If vessel supplies a vital organ, may result in an infarction (tissue
death)

Thromboembolism

Traveling blood clot
• High mortality if occurs in the coronary, cerebral, and pulmonary
arteries

T or F:

Hemoglobin binds equal percentages of oxygen and carbon dioxide.

False

T or F:

Monocytes differentiate into large phagocytic cells.

True

Leukopoiesis begins with the differentiation of?

hematopoietic stem cells

A deficiency of _____ can cause pernicious anemia

Vitamin B12

Where do most RBCs die?

Spleen

Most strokes and heart attacks are caused by the abnormal clotting of blood in an unbroken vessel. Moreover, a piece of the _______ may break loose and begin to travel in the bloodstream as a/an _______

thrombus; embolus

All these can cause leukopenia except?

Dehydration

What would happen If all the hemoglobin contained in RBCs was released into the plasma?

It would significantly increase blood osmolarity.

What is more likely to cause anemia than any of the other factors below?

Kidney disease

Which of the following is not a consequence of anemia?

Blood viscosity is increased

Component of Plasma

• proteins

• Electrolytes

• Nutrients

• Wastes

• Hormones

• Blood gases

Formed elements

• leukocytes

• Platelets

• Erythrocytes

  
  

Will the number of the given cell type increase, decrease, or not be affected by the given situation?

Increase

• Neutrophils: bacterial infection

• Erythrocytes: high altitude

• Basophils: chronic allergies

• Eosinophils: tapeworm infection

Relatively No Change

• Erythrocytes: viral infection

Decrease

• Erythrocytes: iron deficiency

• Erythrocytes: decreased erythropoietin

• Erythrocytes: hemorrhaging

Which of the following characteristics of a red blood cell increases its ability to carry oxygen to the tissues?

• The cytoplasm of an RBC contains 33% hemoglobin.

• RBCs lose nearly all their organelles during their development.

• RBCs lack mitochondria and rely on anaerobic fermentation to produce their own ATP.

Type AB+

• Can receive blood from blood types A, B, AB, and O

• Expresses the A and B antigens

• Expresses the Rh factor

• Lacks antibodies to A and B antigens

Type O-

• Can donate blood to blood types A, B, AB, and O

• Lacks A and B antigens

• Expresses antibodies to A and B antigen

• Does not express the Rh factor

The buffy coat does not contain _______

erythrocytes

What is the most abundant protein in plasma?

Albumin

An individual has type B, Rh-positive blood. The individual has ____ antigens and can produce anti- ______ antibodies.

B and D; A

Antigen presenting cells can be _______ or __________

macrophages; dendritic cells

The overall cessation of bleeding is specifically called ______

hemostasis

The structural framework of the blood clot is formed by ______

fibrin