All flashcards - unit 5

Lymphoid Organs and Tissues

Provide structural basis of immune system

House phagocytic cells and lymphocytes

Structures include spleen, thymus, tonsils, lymph nodes, other lymphoid tissues

Lymphoid Cells

Lymphocytes main warriors of immune system

Arise in red bone marrow

Mature into one of two main varieties

T cells (T lymphocytes)

B cells (B lymphocytes)

Lymphocytes

T cells and B cells protect against antigens

Anything body perceives as foreign

Bacteria and bacterial toxins, viruses, mismatched RBCs, cancer cells

T cells

Manage immune response

Attack and destroy infected cells

B cells

Produce plasma cells, which secrete antibodies

Antibodies mark antigens for destruction by phagocytosis or other means

Macrophages

phagocytize foreign substances; help activate T cells

Dendritic cells

capture antigens and deliver them to lymph nodes; activate T cells

Reticular cells

produce reticular fiber stroma that supports other cells in lymphoid organs

Spleen

Largest lymphoid organ

Served by splenic artery and vein, which enter and exit at the hilum

Functions

Site of lymphocyte proliferation and immune surveillance and response

Cleanses blood of aged cells and platelets, macrophages remove debris

Spleen: Additional Functions

Stores breakdown products of RBCs (e.g., iron) for later reuse

Stores blood platelets and monocytes

May be site of fetal erythrocyte production (normally ceases before birth)

Encased by fibrous capsule; has trabeculae

Contains lymphocytes, macrophages, and huge numbers of erythrocytes

Plasma

non-living fluid matrix

Formed elements

living blood "cells" suspended in plasma

Erythrocytes

red blood cells, or RBCs

Leukocytes

white blood cells, or WBCs

Platelets

Spun tube of blood yields three layers

Plasma on top (~55%)

Erythrocytes on bottom (~45%)

WBCs and platelets in Buffy coat (< 1%)

Cytoplasmic fragments

Normal = 150,000 – 400,000 platelets /ml of blood

Form temporary platelet plug that helps seal breaks in blood vessels

Circulating platelets kept inactive and mobile by nitric oxide (NO) and prostacyclin from endothelial cells lining blood vessels

Age quickly; degenerate in about 10 days

Hematocrit

Percent of blood volume that is RBCs

47% ± 5% for males; 42% ± 5% for females

Physical Characteristics and Volume

Sticky, opaque fluid with metallic taste

Color varies with O2 content

High O2 - scarlet; Low O2 - dark red

pH 7.35-7.45

~8% of body weight

Average volume

5-6 L for males; 4-5 L for females

Functions of Blood

Distributing substances

Regulating blood levels of substances

Protection

Distribution Function

Delivering O2 and nutrients to body cells

Transporting metabolic wastes to lungs and kidneys for elimination

Transporting hormones from endocrine organs to target organs

Regulation Functions

Maintaining body temperature by absorbing and distributing heat

Maintaining normal pH using buffers; alkaline reserve of bicarbonate ions

Maintaining adequate fluid volume in circulatory system

Protection Functions

Preventing blood loss

Plasma proteins and platelets initiate clot formation

Preventing infection

Antibodies

Complement proteins

WBCs

Blood Plasma

90% water

Over 100 dissolved solutes

Nutrients, gases, hormones, wastes, proteins, inorganic ions

Plasma proteins most abundant solutes

Remain in blood; not taken up by cells

Proteins produced mostly by liver

60% albumin; 36% globulins; 4% fibrinogen

Albumin

60% of plasma protein

Functions

Substance carrier

Blood buffer

Major contributor of plasma osmotic pressure

Erythrocytes

Biconcave discs, anucleate, essentially no organelles

Diameters larger than some capillaries

Filled with hemoglobin (Hb) for gas transport

Contain plasma membrane protein spectrin and other proteins

Spectrin provides flexibility to change shape

Major factor contributing to blood viscosity

Structural characteristics contribute to gas transport

Biconcave shape—huge surface area relative to volume

>97% hemoglobin (not counting water)

No mitochondria; ATP production anaerobic; do not consume O2 they transport

structure gives function

Eyrthrocyte Functions

RBCs dedicated to respiratory gas transport

Hemoglobin binds reversibly with oxygen

Normal values

Males - 13-18g/100ml; Females - 12-16 g/100ml

Hemoglobin (Hb)

O2 loading in lungs

Produces oxyhemoglobin (ruby red)

O2 unloading in tissues

Produces deoxyhemoglobin or reduced hemoglobin (dark red)

Blood is NEVER blue

CO2 loading in tissues

20% of CO2 in blood binds to Hb → carbaminohemoglobin

Hematopoiesis

Blood cell formation in red bone marrow

In adult, found in axial skeleton, girdles, and proximal epiphysis of humerus and femur

Hormone Erythropoietin (EPO)

Direct stimulus for erythropoiesis

Always small amount in blood to maintain basal rate

High RBC or O2 levels depress production

Released by kidneys (some from liver) in response to hypoxia

Dialysis patients have low RBC counts

Causes of hypoxia

Decreased RBC numbers due to hemorrhage or increased destruction

Insufficient hemoglobin per RBC (e.g., iron deficiency)

Reduced availability of O2 (e.g., high altitudes)

Effects of EPO

Rapid maturation of committed marrow cells

Increased circulating reticulocyte count in 1–2 days

Some athletes abuse artificial EPO

Dangerous consequences

More blood = heart has to work harder

Testosterone enhances EPO production, resulting in higher RBC counts in males

Fate and Destruction of Erythrocytes

Life span: 100–120 days

No protein synthesis, growth, division

Old RBCs become fragile; Hb begins to degenerate

Get trapped in smaller circulatory channels especially in spleen

Macrophages engulf dying RBCs in spleen

Heme and globin are separated

Iron salvaged for reuse

Heme degraded to yellow pigment bilirubin

Liver secretes bilirubin (in bile) into intestines

Degraded to pigment urobilinogen

Pigment leaves body in feces as stercobilin

Globin metabolized into amino acids

Released into circulation

Erythrocyte Disorders - Anemia

Anemia- deficiency in RBCs

Blood has abnormally low O2-carrying capacity

Sign rather than disease itself = symptom

Blood O2 levels cannot support normal metabolism

Accompanied by fatigue, pallor, shortness of breath, and chills

Causes of Hemorrhagic Anemia

Blood loss rapid (e.g., stab wound)

Treated by blood replacement

Causes of Chronic hemorrhagic anemia

Slight but persistent blood loss

Hemorrhoids, bleeding ulcer

Primary problem treated

Causes of Anemia: Low RBC Production - Iron Definciency Anemia

Caused by hemorrhagic anemia, low iron intake, or impaired absorption

Microcytic, hypochromic RBCs

Iron supplements to treat

Causes of Anemia: Low RBC Production - Renal Anemia

Lack of EPO hormone

Often accompanies kidney disease

Treated with synthetic EPO

*renal =kidney

Causes of Anemia: High RBC Destruction

Hemolytic anemias

Premature RBC lysis (lysis= cell membrane ruptures... cells dies)

Caused by

Hemoglobin abnormalities

Incompatible transfusions (you are A blood and are given B blood as a transfusion)

Infections

Causes of Anemia: High RBC Destruction (Sickle cell anemia)

Black people of African malarial belt and descendants

Malaria

Kills 1 million each year

Sickle-cell gene

Two copies → Sickle-cell anemia

One copy → Sickle-cell trait; milder disease; better chance to survive malaria

Sickle Cell Treatment

Acute crisis treated with transfusions; inhaled nitric oxide

Preventing sickling

Hydroxyurea induces fetal hemoglobin (which does not sickle) formation

Blocking RBC ion channels

Stem cell transplants

Gene therapy

Leukocytes

Make up <1% of total blood volume

4,800 - 10,800 WBCs/μl blood

Function in defense against disease

Leukocytosis:

WBC count over 11,000/mm3

Normal response to infection

Neutrophils

Most numerous WBCs

3-6 lobes in nucleus; twice size of RBCs

Very phagocytic—"bacteria slayers"

Lymphocytes

Second most numerous WBC

Large, dark-purple, circular nuclei with thin rim of blue cytoplasm

Mostly in lymphoid tissue (e.g., lymph nodes, spleen); few circulate in blood

Crucial to immunity

Two types

T lymphocytes (T cells) act against virus-infected cells and tumor cells

B lymphocytes (B cells) give rise to plasma cells, which produce antibodies

Leukocyte disorders

Leukopenia

Abnormally low WBC count—drug induced

Leukemias

all fatal if untreated

Cancer → overproduction of abnormal WBCs

Named according to abnormal WBC clone involved

Myeloid leukemia involves myeloblast descendants

Lymphocytic leukemia involves lymphocytes

Acute leukemia derives from stem cells; primarily affects children

Chronic leukemia more prevalent in older people

Leukemia

Cancerous leukocytes fill red bone marrow

Other lines crowded out → anemia; bleeding

Immature nonfunctional WBCs in bloodstream

Death from internal hemorrhage; overwhelming infections

Treatments

Irradiation, antileukemic drugs; stem cell transplants

Hemostasis

Fast series of reactions for stoppage of bleeding

Requires clotting factors, and substances released by platelets and injured tissues

Three steps

Vascular spasm

Platelet plug formation

Coagulation (blood clotting)

Hemostasis: Vascular Spasm

Vasoconstriction of damaged blood vessel

Triggers

Direct injury to vascular smooth muscle

Chemicals released by endothelial cells and platelets

Pain reflexes

Most effective in smaller blood vessels

Hemostasis: Platelet Plug Formation

Positive feedback cycle

Damaged endothelium exposes collagen fibers

Platelets stick to collagen fibers via plasma protein von Willebrand factor

Swell, become spiked and sticky, and release chemical messengers

ADP causes more platelets to stick and release their contents

Serotonin and thromboxane A2 enhance vascular spasm and platelet aggregation

Hemostasis: Coagulation

Blood transformed from liquid to gel

Series of reactions using clotting factors (procoagulants)

Factors Preventing Undesirable Clotting

Platelet adhesion is prevented by

Smooth endothelium of blood vessels prevents platelets from clinging

Antithrombic substances nitric oxide and prostacyclin secreted by endothelial cells

Disorders of Hemostasis

Thromboembolic disorders:

undesirable clot formation

Disorders of Hemostasis

Bleeding disorders

abnormalities that prevent normal clot formation

Disorders of Hemostasis

Disseminated Intravascular Coagulation (DIC)

abnormal blood clotting in small vessels throughout the body that cuts off the supply of oxygen to distal tissues, resulting in damage to body organs

Blood Clotting Conditions - Thrombus

clot that develops and persists in unbroken blood vessel

May block circulation leading to tissue death

Blood Clotting Conditions - Embolus

thrombus freely floating in bloodstream

Blood Clotting Conditions - Embolism

embolus obstructing a vessel

E.g., pulmonary and cerebral emboli

Risk factors - atherosclerosis, inflammation, slowly flowing blood or blood stasis from immobility

Anticoagulant Drugs

Aspirin

antiprostaglandin that inhibits thromboxane A2

Anticoagulant drugs - heparin

Anticoagulant used clinically for pre- and postoperative cardiac care

Anticoagulant drugs - Warfarin

Used for those prone to atrial fibrillation

Interferes with action of vitamin K

Anticoagulant Drugs - Dabigatran

directly inhibits thrombin

Hemophilia

includes several similar hereditary bleeding disorders

Hemophilia A: most common type (77% of all cases); factor VIII deficiency

Hemophilia B: factor IX deficiency

Hemophilia C: mild type; factor XI deficiency

Symptoms include prolonged bleeding, especially into joint cavities

Treated with plasma transfusions and injection of missing factors

Increased hepatitis and HIV risk

Blood Tranfusions

Whole-blood transfusions used when blood loss rapid and substantial

Packed red cells (plasma and WBCs removed) transfused to restore oxygen-carrying capacity

Transfusion of incompatible blood can be fatal

Human Blood Groups

RBC membranes bear 30 types of glycoprotein antigens

Anything perceived as foreign; generates an immune response

Promoters of agglutination; called agglutinogens

Mismatched transfused blood perceived as foreign

May be agglutinated and destroyed; can be fatal

Presence or absence of each antigen is used to classify blood cells into different groups

ABO blood groups

Types A, B, AB, and O

Based on presence or absence of two agglutinogens (A and B) on surface of RBCs

Blood may contain preformed anti-A or anti-B antibodies (agglutinins)

Act against transfused RBCs with ABO antigens not present on recipient's RBCs

Anti-A or anti-B form in blood at about 2 months of age; adult levels by 8-10

Transfusion Reactions

Occur if mismatched blood infused

Donor's cells

Attacked by recipient's plasma agglutinins

Agglutinate and clog small vessels

Rupture and release hemoglobin into bloodstream

Result in

Diminished oxygen-carrying capacity

Diminished blood flow beyond blocked vessels

Hemoglobin in kidney tubules → renal failure

Symptoms

Fever, chills, low blood pressure, rapid heartbeat, nausea, vomiting

Treatment

Preventing kidney damage

Fluids and diuretics to wash out hemoglobin

Tranfusions

Type O universal donor

No A or B antigens

Type AB universal recipient

No anti-A or anti-B antibodies

Misleading - other agglutinogens cause transfusion reactions

Autologous transfusions

Patient predonates

Blood Typing

Mixing RBCs with antibodies against its agglutinogen(s) causes clumping of RBCs

Done for ABO and for Rh factor

Cross Matching

Mix recipient's serum with donor RBCs

Mix recipient's RBCs with donor serum

Restoring Blood Volume

Death from shock may result from low blood volume

Volume must be replaced immediately with

Normal saline or multiple-electrolyte solution (Ringer's solution) that mimics plasma electrolyte composition

Plasma expanders (e.g., purified human serum albumin, hetastarch, and dextran)

Mimic osmotic properties of albumin

More expensive and may cause significant complications

Diagnostic Blood Tests

Hematocrit - test for anemia

Blood glucose tests - diabetes

Microscopic examination reveals variations in size and shape of RBCs, indications of anemias

Superior Vena Cava

A vein that is the second largest vein in the human body and returns blood to the right atrium of the heart from the upper half of the body.

left atrium

receives oxygenated blood from the lungs

right atrium

Receives deoxygenated blood from the body

Inferior Vena Cava

A vein that is the largest vein in the human body and returns blood to the right atrium of the heart from bodily parts below the diaphragm.

Right Pulmonary Artery

takes blood from the right ventricle to the right lung

Left Pulmonary Artery

carries poor oxygenated blood from the right ventricle to the left lung.

Tricuspid Valve

valve between the right atrium and the right ventricle

Bicuspid Valve

valve between the left atrium and the left ventricle.

Aortic Valve

The semilunar valve separating the aorta from the left ventricle that prevents blood from flowing back into the left ventricle.

Chordae Tendineae

thin bands of fibrous tissue that attach to the valves in the heart and prevent them from inverting

Interventricular Septum

separates the two ventricles

Epicardium

outer layer of the heart

Myocardium

muscular, middle layer of the heart

Endocardium

inner lining of the heart

Coronary Arteries/Veins

Bring nutrients and blood to the heart; removes waste products

Aortic Arch

a curved blood vessel from which arteries branch to the head and neck.

Aorta

The large arterial trunk that carries blood from the heart to be distributed by branch arteries through the body.

Right Pulmonary Vein

transports oxygenated blood from the right lung to the left atrium

Left Pulmonary Vein

transports oxygenated blood from the left lung to the left atrium

Right Ventricle

pumps deoxygenated blood to the lungs

Left Ventricle

pumps oxygenated blood to the body

Apex

the highest point

Pulmonary Valve

valve positioned between the right ventricle and the pulmonary artery

Trabeculae Carneae

muscular ridges on the internal surface of the ventricles

sinoatrial node

A small mass of tissue that is made up of Purkinje fibers, ganglion cells, and nerve fibers, that is embedded in the musculature of the right atrium, and that originates the impulses stimulating the heartbeat -- called also S-A node, sinus node.

brachiocephalic artery delivers blood to

head, neck and upper extremities

Endocrinology

Study of hormones and endocrine organs; controls reproduction, growth, electrolyte balance, and more

Exocrine glands

Produce non-hormonal substances like sweat and saliva, have ducts

Endocrine glands

Produce hormones, lack ducts; include pituitary, thyroid, adrenal, and more

Chemical Messengers

Include hormones, autocrines, and paracrines; hormones travel in blood