Overview
Why needed?
 Origin:

 Blood vessels form from mesoderm
 Blood produced 2 wks after vessels are
formed, during the 5th week of life
What is blood?
Connective tissue?
Different from others
 Matrix not a solid or semi-solid
material
 Matrix of blood is plasma
 watery substance
 Yellowish
○ 90% Water
○ 7% protein
○ 1% minerals
○ 2% other materials incl.
atmospheric gases, chem signals,
and nutrients
More on plasma
Contains:
 Atmospheric gases:
 oxygen, carbon dioxide,
and nitrogen

Comprises 55% of
blood volume
Formed elements
(= Cellular components)
Remaining 45% of blood
volume:
 Erythrocytes (RBCs)
 Leukocytes (WBCs)
 Thrombocytes (platelets)
Hematocrit
Calculates the volume of
red blood cells making
up the blood
Included in a CBC
FYI: CBC (on medical
shows) = complete blood
count
Complete Blood Count includes…
Hematocrit
 The number of RBCs
 The number of WBCs
 The total amount of hemoglobin in the blood
Also provides information about the following
measurements:
 Average red blood cell size (MCV)
 Hemoglobin amount per red blood cell (MCH)
 The amount of hemoglobin relative to the size of the
cell (hemoglobin concentration) per red blood cell
(MCHC)
 The platelet count is also usually included in the
CBC.

Can you answer these questions?
What is the blood composed of?
 Why is the blood unlike any other
connective tissue?
 What does a hematocrit tell you?

Red Blood Cells


No mature nucleus (lost in dev.)
No DNA, so….
○ Use enzymes to carry out their tasks
 Reticulocytes (immature RBC) – have mesh-like network
of rRNA… become mature in ~24 hours
○ Live max 120 days
○ No way to repair & replace damaged cellular components

Appear red b/c of hemoglobin
○ Contains iron  facilitates transport of
O2 and CO2
 4.8 million RBC/mm3 in women
 5.4 million RBC/mm3 in men
Blood Type
Genetic
 Determined by the antigens on the surface of the
RBC membrane
 A,B,O blood group system most common (30
possible in full blood type classification!)
 Blood will attack “non-self”

 Important to match blood types for transfusions

Therefore…
 AB universal acceptor
 O universal donor-has no proteins on the membrane
Rh Factor
The “D” protein
 Most are positive (depends on geography)
 If a woman is negative and conceives with a
positive man, problems can arise—
erythroblastosis fetalis

This can lead to anemia, a condition marked by weakness
and fatigue. Severe anemia can lead to heart failure and
death. The breakdown of RBC leads to the buildup of
bilirubin which can lead to jaundice and brain damage.
Prevention of erythroblastosis
fetalis

Treat negative mothers with Rhogam, a
preventative measure
 Prevents formation of antibodies to Rh
molecule
Given whenever there is a possibility of
fetal blood mixing with maternal blood
following childbirth, abortion,
miscarriage, prenatal testing.
 Once sensitized the woman will always
react against Rh+ cells

Can you answer these questions?
1.
2.
3.
4.
5.
6.
How are RBCs different from most other
cells?
How does the lack of a nucleus affect
RBCs lifespan?
What is hemoglobin and what does it do?
Why are RBCs red?
What is blood type? What do the different
blood types mean?
Why is it dangerous for an Rh- woman to
have an Rh+ baby?
White Blood Cells
WBC : RBC ratio = 1 : 500 or 1000
 Use blood, lymph to move from bone
marrow to the tissues
 5 types (differential WBC count
measures them)






Neutrophils (Most abundant)
Lymphocytes
Eosinophils
Monocytes
Basophils (Least abundant)
Agranulocytes
AKA : Mononuclear
Lack visible granules in
cytoplasm

Granulocytes
Noticeable granules that
produce specialized
secretions for fighting
infection
Nucleus is polymorphic,
lobed, unusually shaped
Monocytes
Lymphocytes
T & B cells
Eosinophils, basophils,
neutrophils
Neutrophils
Granulocyte
 Most common WBC
 Nucleus = 2-5 lobes
 Found in the blood
 First responders in the inflammation
response due to environmental
exposure, some cancers, bacterial
infection
  Predominant cell in pus

Eosinophils
Granulocyte
 5% of WBCs
 Bi-lobed nucleus
 Combats parasitic infections (protists, worms)
 Secretions produced related to allergies
 Normally in thymus GI, ovaries, testes, spleen,
uterus, lymph nodes
 NOT in lungs, esophagus, or skin  if found
here, indicates disease/pathology

Basophils
Granulocyte (least common)
 Susceptible to basic dyes
 Large, bi-lobed nucleus (similar to mast cells)

 Granules obscure the nucleus
 “Bas-ically all granules”
Involved in allergies.
 Stores, secrete histamine & heparin
(anticoagulant)
 Found where allergic reactions are taking place

Agranulocytes
Lymphocytes
 “Immune” cells:

 NK (natural killer) cells (no prior activation needed)
 T lymphocytes (mature in thymus)
○ Helper: direct immune response
○ Cytotoxic: release cytotoxin to kill pathogen infected
cells
 B lymphocytes (mature in bone marrow): Use
antibodies to neutralize pathogens
Monocytes
Agranulocyte
 Largest of WBCs

- shaped nucleus

 Mono = kissing = Love = heart
Many vesicles in cytoplasm for processing
pathogens
 Perform phagocytosis - uptake & digestion of
pathogens

 Fragments of “eaten” pathogen signal T-
lymphocytes to the area
Platelets
Cell fragments derived
from larger cells called
megakaryocytes.
 Have “sticky” proteins
 Reduce blood flow to an affected area.
 Reduce blood loss

Sensitive to many types of hazardous
chemicals and pollutants
Can you answer these questions?
Describe the characteristics & functions
of all granulocytes, agranulocytes, and
platelets.
 Compare and contrast the structure &
function of RBCs and WBCs
 Why are platelets called the “Band-Aids”
of the blood?

Carry oxygen from the lungs to the body
 Carry carbon dioxide from the body to
the lungs

Alveoli-where gas
exchange happens in
the lungs
 RBC in the capillaries that surround the
alveoli oxygen enters

 Only if the partial pressure of oxygen outside
is higher than inside

In cytoplasm of RBC oxygen binds to
Hemoglobin

Four oxygen molecules bind to
hemoglobin (w/ the iron)
 Carries CO2 also;
 binds to a different area than O2

Percent saturation:
 amount of oxygen that is dissolved
in a solution of hemoglobin
molecules
 O2 sats = 98% or above

Similar to with myoglobin in
muscle
 Greater affinity for oxygen
 Hemoglobin collects oxygen a low
partial pressures

In the tissues the oxygen is released and
carbon dioxide enters the RBC, binds to
Hemoglobin.
 Partial pressures of the gases must appropriate
 Some cellular wastes stimulate the release of the
oxygen from the hemoglobin
○ Allows RBC to give more O2 to tissues w/ high
metabolic needs
Carried 3 ways in the blood
1. Carried in the blood as a gas (10%)
2. Binds to empty hemoglobin: carbaminohemoglobin
3. As a bicarbonate ion (HCO3-)
○ CO2 can dissolve in water, forming bicarbonate ion
○ Dissolves in the blood plasma
 Carbonic anhydrase: enzyme in RBC that stim’s the formation
of carbonic anhydrase, which dissociates to form bicarbonate
ions and H+ ions
- Eventually excreted
Diffusion: High concentration  low
concentration
 For Oxygen:

 Partial pressure is higher in blood than in
tissues

For Carbon Dioxide:
 Partial pressure is higher in tissues than in
blood
Occurs when the CO2 is extremely high
in the environment or the blood
 Acute: high levels in the air
 Subacute: toxicity caused by the body’s
failure to eliminate carbon dioxide

 Decreases blood’s pH (what kind of acid
does CO2 form when it dissolves in water?)
○ Carbonic acid!
What is the purpose of RBCs?
 Where does oxygen bind to the Hb
molecule?
 Where does Hb collect oxygen? Then
what happens?
 Describe the partial pressures that must
be present for oxygen to diffuse from
RBC to tissues and for carbon dioxide to
move to the cells?


In general:
 Fight infections & disease
 Granulocytes:
○ granules of toxic chemicals that kill
microorganisms
○ regulate reactions to foreign materials in the
body
Pass through capillaries to
tissues to with infections.
 Attracted to affected areas by factors
secreted by damaged cells/tissues
 Stick to injured tissues, use phagocytosis to
engulf remains of bacteria and damaged cells
 Secretes antibiotics-harms/kills bacteria
 Secretes other chemicals that stim.

 Inflammation ↑ blood flow to the area & ↑ WBC
concentration
Secretions defend against
parasitic infections esp. protists
& worms
 ↑ in eosinophils = parasitic infection
 Granules contain major basic protein to kill the
parasites
 Secrete chemicals associated w/ allergies

Secrete histamine  stim the
immune response
 Overproduction of histamine  runny nose,
sneezing, watery eyes
 Mast cells (special kind of basophil)

 Cause inflammation of tissues
 Secrete chemical that attract neutrophils
 Found in walls of small bl. vessels
Clear granules give cytoplasm
a grey appearance
 When they leave the bone marrow they
become either:

 Circulating monocytes
○ Detect infections in blood
○ Bone growth & maintenance
 Tissue monocytes (macrophages)
○ Remove dead cells
○ Attack microorganisms that are difficult to kill (fungi)
Stay tuned! We’ll
talk about it later….for now,
they carry out most of the
duties of the immune system

Which WBC is in charge of engulfing
bacteria?
 Which WBC is in charge of protecting us
from parasites?
 Which WBC differentiates into cells that assist
in bone growth and maintenance or are
macrophages that protect against fungal
infections?
 Which WBC secretes major basic protein?


Blood clotting
 Platelets adhere to injured area
 Activation of blood clot formation

Important that clot forms by injury only
 Intact cells secrete prostacyclin (prevents platelet
activation)
1.) BV damaged, releases “distress chemicals”
2.) Clotting factors stim. other factors that indicates presence of
damaged tissues
a.) platelets stick to damaged tissues & each other
b.) Platelets secrete prothrombin activator & Ca2+
- Catalyze conversion of prothrombin to thrombin
c.) Thrombin causes fibrinogen  fibrin
d.) Fibrin forms a sticky mesh that adheres to thrombocytes
and other blood components (clot)
- Clot forms a barrier that prevents blood loss & impedes
the passage of microorganisms into tissues
- Calcium ions = catalyze PT to T
- Vitamin K = synthesis of clotting factors
Prothrombin
Thrombin
Fibrinogen
Fibrin
So the blood doesn’t clot unintentionally!
 They aren’t permanent
 Plasminogenplasmin (digests fibrin and
dissolves a clot)
 Healthy cells near the clot secrete TPA
(tissue plasminogen activator)dissolves
fibrin as well.

Can you answer these questions?
1.) What is the purpose of prostacyclin?
2.) What is the purpose of a clot?
3.) What are the steps of the clotting
cascade?
4.) What is the role of calcium and vitamin K
in clot formation?
5.) Why is the clot cascade so complex?
6.) What do plasmin and tissue plasminogen
have in common? What’s the difference?
Adults: bone marrow
 Embryo: Liver

 Different forms of Hb throughout development
allow fetus to adapt to varying metabolic needs
for oxygen
11 million/sec in an adult
 1 WBC produced for every ~500 RBCs

Adults: bone marrow
 Embryo: Liver
 11 million/sec in an adult
 1 WBC produced for every 700 RBCs

GF
Myeloid
stem cell
(progenitor)
Hematopoietic stem cell
Or
Multipotent stem cell
Or
Pluripotent stem cell
GF
Lymphoid
stem cell
(progenitor)
The life history of erythrocytes
(RBCs)

Blood oxygen decreases
 Stimulates erythropoietin production from
kidneys and liver
Erythropoietin  Erythropoiesis in
red bone marrow (where is this
found?)
 Immature erythrocytes have a large
nucleus
 Hb production begins in basophilic
erythroblasts
 Reticulocytes: lose nucleus, after 1-2
days in circulation lose organelles

If the need for oxygen is great,
erythropoiesis will occur at an
increased rate.
 This means an increased amount of
polychromatic erythroblasts will enter
the blood stream
 Erythropoiesis of a single erythrocyte
takes approximately 4 days


Normal bone marrow has an abundance
of newly formed RBCs and
megakaryocytes (which produce
platelets)
Removed by macrophages
 Globin (protein) is broken into individual
amino acids & recycled
 Iron is recycled
 Parts of the molecule are converted to
bilirubin

 Processed in liver, secreted in bile in small
intestine
○ Bacteria convert into pigments feces color
○ Some excreted in urine yellow color

Lifespan = 13-20 days
 Destroyed in lymphatic system

When released from bone marrow called
stabs or bands
 Esp. neutrophils b/c their nuclei aren’t lobed,
yet, and look like a rod (stab = German for
rod) or bands
Functions of Lymphatic System
1.) Maintain fluid balance in the tissues
○ 30L fluid from capillaries to interstitial and only
27L pass from interstitial back into capillaries
qd (every day)
○ If fluid left in the body  tissue damage
○ 3L fluid enter lymph capillaries, called lymph
 Then to lymph vessels & return to blood
2.) Absorb fats & other substances from
digestive tract (chyle)
3.) Defense
○ Nodes filter lymph & spleen filters blood of
microorganisms & foreign substances
Lymphatic System Structures

Lymph
 Like plasma: ions, nutrients,
wastes from interstitial spaces
 Hormones, enzymes from cells in
tissues


Lymphocytes
Lymph vessels
○ Flow of lymph produced by gravity
or skeletal muscle, passively drains
to lower body from upper
○ Valves-no backflow
○ Lymphatic trunks drain lymph from
larger areas of body
 Clusters of lymphatic tissue
Lymphatic System Structures

Lymph nodes
 Collections of lymphatic
tissue covered by
connective-tissue
capsules
 Eliminate antigens from
lymph as lymph flows
thru the node.
 In groups along the
larger lymphatic vessels
Lymph node structure

2 divisions: Cortex (outer) & Medulla (inner)
 Cortex
○ Has “compartments” called lymphatic nodules
○ 2 layers: inner layer called germinal center where Blymphocytes are found. In the “wall” surrounding the
germinal center is where T-lymphocytes are found.
○ Nodules are sep’d by trabeculae—extensions of the
capsule—fibrous covering of the node
○ Cortical sinus: spaces where lymph flows through
 Medulla
○ Medullary sinus = space where lymph flows throught he
center of the node, contains macrophages
○ Medullary cord = contains lymphocytes
Lymphatic System Structures

Tonsils
 Swollen cluster of lymphatic tissue in throat
 Form protective ring of lymphatic tissue around the openings
between the nasal and oral cavities & pharynx
 Provide protection against bac and other harmful material
 Eventually disappear in adults

Spleen
 Detects and responds to foreign substances in the blood
 Destroys worn out red blood cells
 Acts as a blood reservoir
 Structure
○ Left side of the extreme superior, posterior corner of ab cavity
○ White pulp: Contains T & B lymphocytes
 Assist body with infections that require a large immune response
○ Red pulp: removes old/damaged RBCs
Lymphatic System Structure

Thymus
 Deep to manubrium
 In newborn, extends length of thorax & grows until
puberty, then decreases in size
 Function
○ Produce lymphocytes that move to other lymph
tissues, but most degenerate before moving on
○ Produces secretions that mature T-lymphocytes
 Can’t destroy normal body cells (Self-tolerance)
Immunity words to know:

Antigen: a substance that can
induce an immune response.
Hapten: A molecule that can cause an
immune response when attached to
blood proteins.
 Two ways the immune system can
respond to disease:

 Innate immunity
 Acquired immunity
Why an immune system?
We are outnumbered! Viruses and
bacteria are everywhere!
 Humans offer limitless resources for
pathogens

 Energy
 Reproductive potential

Getting into the body isn’t easy!
Meet the enemy

Bacteria
 Free-living
 Not all are bad!
 Pathogenic ones produce toxins that
damage human tissue

Viruses
 Obligate parasites
 Hijack human cells; convert to virus-
producers, killing host cell in the process

(And fungi, protozoa too…)
A human fortress: Prevention
Skin is thick – hard to penetrate
 Produces substances that deter invasion:

 Skin pH (not favorable)
 Mucus (sticky trap)
 Lysozymes (digest bacteria)

Specialized traps around vulnerable areas
(Eyes, nose, mouth)
 Cilia sweep away invaders that are
trapped
 Stomach acid kills ingested invaders
…but we do get sick!

Enter through weak points:
 Food
 Nose
 Break in skin/scrapes

Cells are damaged/destroyed
 Dying cells release distress chemicals
(histamine)
○ Triggers inflammation (blood vessel dilation,
increased blood flow)
○ Draws defensive cells to area (generalized white
blood cells)
How do we tell “friend” from
“foe”?

All cells present antigens – surface
protein molecules that identify identity
 (antigen = antibody generator)

Immune system reacts to foreign
antigens
A complex system!
Several “lines” of defense:
1. Barriers (First line of defense)
2. Generalized defenders (Second line of
defense)
3. Specific defenders AND memory (Third
line of defense)
Consist of:
 Several types of cells
 Proteins
The Complement System
Part of second line of defense
 Free-flowing proteins found in blood
 Quickly reach site of invasion
 React to antigens
 When activated, can

 Trigger inflammation
 Attract “eater cells” (macrophages)
 Coat pathogen (make macrophages’ job easier)
 Kill intruder directly
Phagocytes
Find and “eat” bacteria, viruses,
dead/injured body cells by
phagocytosis
 3 types:

 Neutrophils
 Macrophages
 Dendritic cells
Neutrophils
Often first to site of infection
 Numerous
 Short lifespan
 “Pus” in infected wounds chiefly
composed of neutrophils

Macrophage
“Big eaters”
 Slower to respond to invader than
neutrophil

 Larger, longer-lived, more capable
Help alert rest of immune system to
invader
 Start as monocytes; become
macrophages when entering
bloodstream

Dendritic cells
“Eater” cells
 Help with immune system activation –
act as antigen-presenting cells
 Filter bodily fluids to clear foreign
organisms and particles

Lymphocytes: Third Line of
Defense
T and B cells
 Originate in bone marrow
 Migrate to lymph nodes, spleen, thymus
to mature
 Lymph vessels

 transport, store lymphocytes
 Feeds cells into body
 Filter out dead cells/invading organisms
Receptors

Each lymphatic cell contains surface
receptors
 Recognize foreign antigens
 Specialized for a particular antigen
T cells
Two types: helper and killer
 T = thymus
 Mature here

Helper T cell
Main regulator of third line of defense
 Primary task: activate B cells and killer T
cells
 Activated by macrophages/dendritic cells
(antigen presentation)

Killer T cell
Attacks body cells infected by
pathogen, cancer cells
 Receptors used to determine if each cell
encountered is self/non-self (compare
to accepted receptors, MHC)

B lymphocyte cell
Searches for antigens matching receptor
 If a match is found…

 Connects to antigen
 Triggering signal set off…
○ T helper proteins help fully activate B cell
 Produces 1000’s of clones: differentiate into
plasma cells or B memory cells
Plasma Cell
Produces antibodies
 Responds to same antigen matched by
B cell receptor

 Seek out intruders, help destroy them
 Release tens of thousands/second
Antibodies
Y-shaped
 Attach to matching antigens

 Enhance phagocytosis of macrophages (label for
capture)
 Neutralize toxins
 Incapacitate viruses (coat surface proteins)
 Group pathogens by linking (agglutination)
Immunoglobins
IgG: most common, fight general infections, pass
from mom to child in pregnancy (G= mom’s gift)
 IgA: in mucous membranes of the digestive
system, milk, tears, saliva (A= a lot of mucus)
 IgM: natural defenses against general bacterial
infections (M=most bacteria)
 IgE: stim basophils and mast cells to defend
against parasites fungi and worms (E=eeww!)
 IgD: on membranes of B-lymphocytes, form
plasma and memory cells (D=defend blood)

Memory cells
Prolonged lifespan
 “Remember” specific intruders
 Both B and T cells have memory cells
 Helps trigger immune system to respond
more quickly if invader reappears

Inflammation
Outcome of acquired immune response
 Increases blood circulation to affected area





Bv’s dialate to increase blood flow
Immune cells go to injured area
Immune resp. takes place at the site it’s needed
Tissues = red and warm b/c of the blood that enters
the area, ↑ in temp = anti-microbial
 Pain from pressure of swollen tissues on nerve
endings
 Normal functions return when the tissue is fully
recovered
Natural Immunity

Natural: exposed to foreign antigens as a part of
everyday life.
 Active immunity – body responds to foreign antigens
and develops immunity using B and T lymphocytes
 Passive immunity –
○ Embryological development when antibodies (Ig’s) from
the mother’s blood stream are passed to the fetus
○ Breastfeeding – baby receives antibodies via milk
Artificial Immunity

Active: Immunization
 Therapeutic exposure to antigens
 Stimulates the primary response by introducing
pathogenic material (inactivated, attenuated, or partial)
into the body
 Vaccines are typically used for viruses! Antibiotics are
only for bacteria

Passive: Antibody Transfer
 Patient receives (via injection) large amounts of
antibodies to fight disease
○ Globulin injections can remove certain microorganisms
from the body.
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The Lymphatic System and the Blood

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