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Respiratory System, Blood
The Respiratory System
Major Functions:
Supply body with O2 for cellular respiration and dispose of CO2, a waste product for cellular respiration
Speech
Nasal passages have chemoreceptors involved with the sense of smell (olfaction)
Four Processes Involved With Respiration:
Pulmonary Ventilation (breathing): movement of air into and out of lungs
External Respiration: exchange of O2 and CO2 between lungs and blood
Transport of O2 and CO2 in blood by the circulatory system
Internal Respiration: exchange of O2 and CO2 between systemic blood vessels and tissues
Major Organs
Upper respiratory
Nose and nasal cavity
Paranasal sinuses
Pharynx
Lower respiratory
Larynx
Trachea
Bronchi and branches
Lungs and alveoli
Upper Respiratory System
The Nose
Nose is only external portion of respiratory system
Functions of the nose:
Provides an airway for respiration
Mositens and warms entering air
Filters and cleans inspired air
Serves as resonating chamber for speech
Houses olfactory receptors
The Nasal Cavity
Nasal Vestibule: nasal cavity superior to nostrils
Lined with hairs that filter coarse particles from inspired air
Rest of nasal cavity lined with mucous membranes
Olfactory mucosa: lines superior region of nasal cavity and contains olfactory epithelium
Respiratory mucosa: pseudostratified ciliated columnar epithelium that contains goblet cells and rests on lamina propria that contains many seromucous glands
Seromucous glands contain mucus-secreting mucous cells and serous cells which secrete watery fluid that contains lysozyme and defensins
Ciliated cells sweep contaminated mucus posteriorly towards throat
Paranasal sinuses
Paranasal sinuses form ring around nasal cavities
Located in frontal, sphenoid, ethmoid, and maxillary bones
Functions:
Lighten skull
Secrete mucus
Help to warm and moisten air
Homeostatic Imbalance
Rhinitis
Inflammation of nasal mucosa
Viral infection or allergies
Nasal mucosa is continuous with mucosa of respiratory tract, so infections spread from nose to throat to chest
Can also spread to tear ducts and paranasal sinuses, causing blockage of sinus passageways
Can lead to absorption of air, producing a vacuum, resulting in sinus headache
The Pharynx
A funnel-shaped muscular tube that connects the nasal cavity and mouth to larynx and esophagus
Three regions
Nasopharynx
Oropharynx
Laryngopharynx
Nasopharynx
Air passageway posterior to the nasal cavity
Lining contains pseudostratified columnar epithelium
Soft palate and uvula close nasopharynx during swallowing
Pharyngeal tonsils : located on posterior wall
Pharyngotmpanic tubes : drain and equalize pressure in middle ear and open into lateral walls
Oropharynx
Passageway for food and air from level of soft palate to epiglottis
Lining consists of stratified squamous epithelium
Palatine tonsils located in the lateral walls near the soft palate
Lingual tonsil is located on posterior surface of tongue
Laryngopharynx
Passageway for food and air
Posterior to upright epiglottis
Extends to larynx, where it is continuous with esophagus
Lined with stratified squamous epithelium
Homeostatic Imbalances
Infected and swollen adenoids can block air passage in nasopharynx, making it necessary to breathe through the mouth
As a result, air is not properly moistened, warmed, or filtered before reaching lungs
When adenoids are chronically enlarged, both speech and sleep may be disturbed
Lower Respiratory System
Broken into two zones
Respiratory zone : site of gas exchange
Consists of microscopic structures such as respiratory bronchioles, alveolar ducts, and
Conducting zone : Conduits that transport gas to and from gas exchange sites
Includes all other respiratory structures
Cleanses, warms, and humidifies air
The Larynx
Larynx (voice box) extends from 3rd to 6th cervical vertebra and attaches to hyoid bone
Opens into laryngopharynx and is continuous with trachea
Houses vocal folds
Framework of consists of cartilages connected by membranes and ligaments
Three functions of larynx:
Provides open airway
Routes air and food into proper channels
Voice production
Epiglottis
Consists of elastic cartilage (not hyaline)
Covers laryngeal inlet during swallowing
Covered in taste bud–containing mucosa
Vocal folds
Vocal ligaments : form core of vocal folds (true vocal cords)
Contain elastic fibers that appear white because of lack of blood vessels
Glottis : opening between vocal folds
Folds vibrate to produce sound as air rushes up from lungs through the glottis
Vestibular folds (false vocal cords)
Superior to vocal folds
No part in sound production
Help to close glottis during swallowing
Voice Production
Speech : intermittent release of expired air during opening and closing of glottis
Pitch : is determined by length and tension of vocal cords
Loudness : depends upon force of air
Chambers of pharynx and oral, nasal, and sinus cavities amplify and enhance sound quality
Sound is “shaped” into language by muscles of pharynx, tongue, soft palate, and lips
Homeostatic Imbalance
Laryngitis : inflammation of the vocal folds that causes the vocal folds to swell, interfering with vibrations
Results in changes to vocal tone, causing hoarseness; in severe cases, speaking is limited to a whisper
Laryngitis is most often caused by viral infections but may also be due to overuse of the voice, very dry air, bacterial infections, tumors on the vocal folds, or inhalation of irritating chemicals
Trachea
It is about 4 inches long, 3/4 inch in diameter, and very flexible
Extends from larynx to behind the heart, where it divides into two main bronchi
Wall composed of three layers
Mucosa : ciliated pseudostratified epithelium with goblet cells
Submucosa : connective tissue with seromucous glands supported by C-shaped cartilage rings that prevent collapse of trachea
Adventitia : outermost layer made of connective tissue
Homeostatic Imbalance
Smoking inhibits and ultimately destorys cilia
Without ciliaey activity, coughing is only way to prevent mucus from accumulating in lungs
Reason smokers with respiratory congestion should avoid medications that inhibit cough reflex
Tracheal obstruction is life threatening: many people have suffocated after choking on a piece of food that suddenly closed off their trachea
Heimlich maneuver : procedure in which air in victim’s lungs is used to “pop out,” or expel, an obstructing piece of food
Maneuver is simple to learn and easy to do but is best learned by demonstration; when done incorrectly, may lead to cracked ribs
The Bronchi and Subdivisions
Air passages undergo 23 orders of branching
Branching referred to as bronchial tree
At the tips of the bronchial tree, conducting zone structures give rise to respiratory zone structures
Conducting zone structures
Trachea divides to form right and left main (primary) bronchi
Each main bronchus enters hilum (enterance) of one lung
Each main bronchus then branches into lobar (secondary) bronchi
Three on right and two on left
Each lobar bronchus supplies one lobe
Each lobar bronchus branches into segmental (tertiary) bonchi
Segmental bronchi divide repeatedly
Branches become smaller and smaller
Bronchioles: less than 1 mm in diameter
Terminal bronchioles: smallest of all branches
Less than 0.5 mm in diameter
In conducting zone, from bronchi to bronchioles, changes occur
Support structures chnage
Cartilage rings become irregular plates
In bronchioles, elastic fibers replace cartilage altogether
Epithelium type changes
Pseudostratified columnar gives way to cuboidal
Cilia and goblet cells become more sparse
Amount of smooth muscle increases
Allows bronchioles to provide substantial resistance to air passage - during parasympathetic response: less oxygen is needed, hence bronchoconstriction
Respiratory zone structures
Respiratory zone begins where terminal bronchioles feed into respiratory bronchioles, which lead into alveolar ducts and finally into alveolar sacs (saccules)
Alveolar sacs contain clusters of alveoli
~300 million alveoli make up most of lung volume
Sites of actual gas exchange
Respiratory membrane
Blood air barrier that consists of alveolar and capillary walls along with thei fused basement membrane
Very thin (~0.5 μm); allows gas exchange across membrane by simple diffusion
Alveolar walls consist of:
Single layer of squamous epithelium (type I alveolar cells)
Scattered cuboidal type II alveolar cells secrete surfactant and antimicrobial proteins
Other significant features of alveoli:
Surrounded by fine elastic fibers and pulmonary capillaries
Alveolar pores connect adjacent alveoli
Equalize air pressure throughout lung
Provide alternate routes in case of blockages
Alveolar macrophages keep alveolar surfaces sterile
2 million dead macrophages/hour carried by cilia to throat and swallowed
Lungs
Left lung: separated into superior and inferior lobes
Smaller than right because of position of heart
Cardiac notch: concavity for heart to fit into
Right lung: separated into superior, middle, and inferior lobes
Each lobe further divided into bronchopulmonary segments
Separated by connective tissue
Each segment is served by its own artery, vein, and bronchus
If one segment is diseased, it can be individually removed
Lungs are mostly composed of alveoli; the rest consists of stroma (elastic connective tissue that makes the supportive framework of an organ), elastic connective tissue
Makes lungs very elastic and spongy which allows for expansion and recoil
The Lungs have Two Circulations
Pulmonary circulation
Pulmonary arteries deliver systemic venous blood from heart to lungs for oxygenation
Branch profusely to feed into pulmonary capillary networks
Pulmonary veins carry oxygenated blood from respiratory zones back to heart
Low-pressure, high-volume system
Bronchial circulation
Bronchial arteries provide oxygenated blood to lung tissue
Part of systemic circulation, so are high pressure, low volume
Supply all lung tissue except alveoli
Pulmonary veins carry most venous blood back to heart
The Pleurae
Pleurae: thin, double-layered serosal membrane that divides thoracic cavity into two pleural compartments and mediastinum
Parietal pleura :
membrane on thoracic wall, superior face of diaphragm, around heart, and between lungs
Visceral pleura:
membrane on external lung surface
Pleural fluid fills slitlike pleural cavity between two pleurae
Provides lubrication and surface tension that assists in expansion and recoil of lungs
Homeostatic Imbalance
Pleurisy: inflammation of pleurae that often results from pneumonia
Inflamed pleurae become rough, resulting in friction and stabbing pain with each breath
Pleurae may produce excessive amounts of fluid, which may exert pressure on lungs, hindering breathing
Respiratory Physiology
Pulmonary Ventilation
A mechanical process that depends on volume changes in the thoracic cavity.
volumes changes lead to pressure changes, and pressure changes lead to the flow of gasses to equalize the pressure
Consists of two phases
Inspiration: gases flow into lungs
Expiration: gases exit lungs
Boyle’s Law
The pressure of gas in a closed space varies inversely with its volume (at a constant temp)
Gases always fill the container they are in
If amount of gas is the same and container size is reduced pressure will increase
Mathematically:
P1V1 = P2V2
Inspiration
Active process : involving inspiratory muscles (diaphragm and external intercostals)
Action of the diaphragm : when dome-shaped diaphragm contracts, it moves inferiorly and flattens out
Results in increase in thoracic volume
Action of intercostal muscles : when external intercostals contract, rib cage is lifted up and out
Results in increase in thoracic volume
As thoracic cavity volume increases lungs are stretched as they are pulled out with thoracic cage
Causes intrapulmonary pressure to drop
Because of difference between atmospheric and intrapulmonary pressure, air flows into lungs, down its pressure gradient, until Ppul = Patm
Expiration
Expiration normally is passive process
Inspiratory muscles relax, thoracic cavity volume decreases, and lungs recoil
Volume decrease causes intrapulmonary pressure (Ppul) to increase
Ppul > Patm so air flows out of lungs down its pressure gradient until Ppul = Patm
Forced expiration is an active process that uses oblique and transverse abdominal muscles, as well as internal intercostal muscles
Homeostatic Imbalance – Airway Resistance
As airway resistance rises, breathing movements become more strenuous
Severe constriction or obstruction of bronchioles:
Can prevent life-sustaining ventilation
Can occur during acute asthma attacks and stop ventilation
Epinephrine dilates bronchioles, reduces air resistance
Gas Exchange
Gas exchange occurs between lungs and blood as well as blood and tissues
External respiration: diffusion of gases between blood and lungs
Internal respiration: diffusion of gases between blood and tissues
Both processes are subject to:
Basic Properties of gases
Composition of alveolar gas
Basic Properties of Gases
Dalton’s law of partial pressures
Total pressure exerted by mixture of gases is equal to sum of pressures exerted by each gas
Partial pressure
Pressure exerted by each gas in mixture
Directly proportional to its percentage in mixture
Total atmospheric pressure equals 760 mm Hg
Nitrogen makes up ~78.6% of air; therefore, partial pressure of nitrogen, PN2, can be calculated:
Oxygen makes up 20.9% of air, so PO2 equals:
Air also contains 0.04% CO2, 0.5% water vapor, and insignificant amounts of other gases
At high altitudes, particle pressures declines, but at lower altitudes (under water), partial pressures increase significantly
Henry’s Law
For gas mixtures in contact with liquids:
Each gas will dissolve in the liquid in proportion to its partial pressure
At equilibrium, partial pressures in the two phases will be equal
Amount of each gas that will dissolve depends on:
Solubility: CO2 is 20x more soluble i water than O2, and little N2 will dissolve
Temperature: as temperature of liquid rises, solubility decreases
Composition of Alveolar Gas
Alveoli contain more CO2 and water vapor than atmospheric air because of:
Gas exchanges in lungs (O2 diffuses out of lung, and CO2 diffuses into lung)
Humidification of air by conducting passages
Mixing of alveolar gas with each breath
Newly inspired air mixes with air that was left in passageways between breaths
External Respiration
External respiration (pulmonary gas exchange) involves the exchange of O2 and CO2 across respiratory membranes
Exchange is influenced by:
Thickness and surface area of repirtatory membrane
Partial pressure gradients and gas solubilities
Partial pressure gradients and gas solubilites
Drives oxygen flow into blood
Steep partial pressure gradient from O2 exists between blood and lungs
Partial pressure graident crom CO2 is less steep
Though gradient is not as steep, CO2 still diffuses in equal amounts with oxygen
Reason is that CO2 is 20× more soluble in plasma and alveolar fluid than oxygen
Thickness and surface area of the respiratory membrane
Respiratory membranes are very thin
0.5 to 1 μm thick
The total surface area of the alveoli is 40× the surface area of the skin
Homeostatic Imbalance
Effective thickness of respiratory membrane increases dramatically if the lungs become waterlogged and edematous
Seen in pneumonia or left heart failure
The 0.75 seconds that red blood cells spend in transit through pulmonary capillaries may not be enough for adequate gas exchange
Result: body tissues suffer from oxygen deprivation
Certain pulmonary diseases drastically reduce alveolar surface area
Example: in emphysema, walls of adjacent alveoli break down, and alveolar chambers enlarge
Tumors, mucus, or inflammatory material also can reduce surface area by blocking gas flow into alveoli
Internal Respiration
Interal respiration involves capillary gas exchange in body tisses
Partial pressures and diffusion gradients are reversed compared to external respiration
Tissue PO2 is always lower than in arterial blood PO2 , so oxygen moves from blood to tissues
Tissue PCO2 is always higher than arterial blood PCO2, so CO2 moves from tissues into blood
Transport of Gasses
Oxygen Transport
Oxygen is not very soluble in our plasma so Molecular O2 is carried in blood in two ways:
1.5% is dissolved in plasma
98.5% is loosely bound to each Fe (iron) of hemoglobin (Hb) in red blood cells
Each hemoglobin molecule is composed of four polypeptide chains, each with a iron-containing heme group
So each hemoglobin can transport four oxygen molecules
The attraction between O2 and hemoglobin is affected by:
Po2
the higher the Po2 the more oxygen will bind with hemoglobin
when the RBCs arrive at a cell where the Po2 is low the hemoglobin releases the oxygen, which then diffuses into the cell
The next four factors alter hemoglobin’s shape causing the release of O2:
Temperature - higher hastens release
Pco2- higher partial pressure of CO2 hastens release
pH (level of acidity) - increased acidity = release
BPG (Bisphosphoglycerate) - a by-product of glycolysis
These four factors all cause the release of O2 when they are high and they are all at their highest inside cells
Homeostatic Imbalance
Hypoxia (or hypoxemia): inadequate O2 delivery to tissues; can result in cyanosis
Hypoxia is based on cause:
Anemic hypoxia: too few RBCs or abnormal or too little Hb
Ishcemic hypoxia: impaired or blocked circulation
Histotoxic hypoxia: cells unable to use O2, as in metabolic poisons
Hypoxemic hypoxia: abnormal ventilation; pulmonary disease
Carbon monoxide posioning: especially from fire or engines
Hemoglobin has a 200× greater affinity for carbon monoxide than oxygen
Carbon Dioxide Transport
CO2 is transported in blood in three forms:
7 to 10% dissolved in plasma as Pco2
20% of CO2 is bound to hemoglobin
70% is transported as bicarbonate ions (HCO3-) in plasma
Formation of bicarbonate involves CO2 combining with water to form carbonic acid (H2CO3), which quickly dissociates into bicarbonate and H+
The influence of CO2 on blood pH
the level of CO2 is your blood affects the pH of your blood
excess CO2 leads to respiratory acidosis
insufficient CO2 leads to respiratory alkalosis
We are very intolerant of even slight pH changes, therefore we control blood CO2 levels by controlling the expiration rate
The major factor (by far) which determines the rate of your breathing is the CO2 level of your blood.
Blood
the life-sustaining transport vehicle of the cardiovascular system
Functions:
Transport
Delivering oxygen and nutrients to body cells
Transporting metabolic wastes to lungs and kidneys for elimination
Transporting hormones from endocrine organs to target organs
Regulation
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
Preventing blood loss
Plasma proteins and platelets in blood initiate clot formation
Preventing infection
Agents of immunity are carried in blood
Antibodies
Complement proteins
White blood cells
Composition of Blood
Blood is the only fluid tissue in body
Type of connective tissue
Matrix is nonliving fluid called plasma
Cells are living blood cells called formed elements
Erythrocytes (red blood cells)
Leukocytes (white blood cells)
Platelets
Plasma- (almost 55% of volume) the liquid portion
plasma is about 90% water, plus various solutes like:
nutrients, gases, hormones, waste, and plasma proteins
Plasma proteins are most abundant solutes
Remain in blood; not take up by cells
Proteins produced mostly by liver
Albumin: makes 60% of plasma proteins
Functions as carrier of other molecules, as blood buffer, and contributes to plasma osmotic pressure
Plasma (and its solutes) are free to diffuse in and out of blood vessels and the name of this liquid changes with location:
plasma- when it is inside the circulatory system
interstitial fluid- when it is in intercellular spaces bathing cells
lymph- when it is in the lymph vessels
Formed elements- cells and cell fragments
Erythrocytes (RBCs)- are essentially just bags of hemoglobin
they have no nucleus, do not reproduce and undergo very little metabolic activity
Three features make for efficient gas transport:
Biconcave shape offers huge surface area relative to volume for gas exchange
Hemoglobin makes up 97% of cell volume (not counting water)
RBCs have no mitochondria
ATP production is anaerobic, so they do not consume O2 they transport
Function of Erythrocytes
RBCs are dedicated to respiratory gas transport
Hemoglobin binds reversibly with oxygen
Hemoglobin consists of red heme pigment bound to the protein globin
Globin is composed of four polypeptide chains
Two alpha and two beta chains
A heme pigment is bonded to each globin chain
Gives blood red color
Each heme’s central ion atom binds one Oxygen
Each Hb molecule can transport four O2
Each RBC contains 250 million Hb molecules
Production of Erythrocytes
Hematopoiesis : formation of all blood cells
Occurs in red bone marrow; composed of reticular connective tissue and blood sinusoids
In adult, found in axial skeleton, girdles, and proximal epiphyses of humerus and femur
Hematopoietic stem cells (hemocytoblasts)
Stem cell that gives rise to all formed elements
Hormones and growth factors push cell toward specific pathway of blood cell development
RBCs have a lifespan of about 120 days, therefore you must produce greater than 2 million per second just to break even
Eryhropoiesis- erythrocyte production
rate of production is hormonally controlled by the kidneys which release a hormone, erythropoietin, whenever their cells become hypoxic
Dietary requirements for erythropoiesis
Amino acids, lipids, and carbohydrates
Iron: available from diet
65% of iron is found in hemoglobin, with the rest in liver, spleen, and bone marrow
Vitamin B12 and folic acid are necessary for DNA synthesis for rapidly dividing cells such as developing RBCs
Leukocytes
General Structure and Functional Characteristics
Leukocytes are only formed element that is complete cell with nuclei and organelles
Make up <1% of total blood volume
Function in defense against disease
Transported in the blood but can leave capillaries via diapedesis
Leukocytes grouped into two major categories:
Granulocytes: contain visible cytoplasmic granules
Agranulocytes: do not contain visible cytoplasmic granules
they squeeze between the capillary’s endothelial cells -> RBCs cannot
they can travel around between cells by what is called amoeboid motion
WBCs migrate toward injured or infected tissue by following the trail of chemicals released by damaged cells or by invaders
a process is called chemotaxis
Granulocytes: three types
Neutrophils
Most numerous WBCs
Very phagocytic
Referred to as “bacteria slayers”
Kill microbes by process called respiratory burst
Cell synthesizes potent oxidizing substances (bleach or hydrogen peroxide)
Esoinophils
Account for 2–4% of all leukocytes
Red-staining granules contain digestive enzymes
Release enzymes on lage parasitic worms, digesting their surface
Also play role in promoting inflammation in allergies and asthma; are beneficial as well as immune response modulators
Asthma: a respiratory condition marked by spasms in the bronchi of the lungs, causing difficulty in breathing. Airways narrow as inflammation induces contracting of the smooth muscle. This can make breathing difficult. It usually results from an allergic reaction or other forms of hypersensitivity.
High levels of eosinophils can cause inflammation in the airways, affecting the sinuses and nasal passages as well as the lower airways.
Basophils
Rarest WBCs, accounting for only 0.5–1% of leukocytes
Large, purplish black (basophilic) granules contain histamine
Histamine : inflammatory chemical that acts as vasodilator and attracts WBCs to inflamed sites
Are functionally similar to mast cells
Agranulocytes - lack visible cytoplasmic granules
Lymphocytes
Second most numerous WBC, accounts for 25%
Mostly found in lymphoid tissue (example: lymph nodes, spleen), but a few circulate in blood
Crucial to immunity
Two types of lymphocytes
T lymphocytes (T cells) : act against virus-infected cells and tumor cells
B lymphocytes (B cells) : give rise to plasma cells, which produce antibodies
Monocytes
Largest of all leukocytes; 3–8% of all WBCs
Dark purple-staining, U- or kidney-shaped nuclei
Leave circulation, enter tissues, and differentiate into macrophages
Actively phagocytic cells; crucial against viruses intarcellular bacterial parasites, and chronic infections
Activate lymphocytes to mount an immune response
Platelets: fragments of cells
Contain several chemicals involved in clotting process
Function: form temporary platelet plug that helps seal breaks in blood vessels
Circulating platelets are kept inactive and mobile
Hemostasis- prevention of blood loss
3 phases:
Vascular spasm
results from damage to the smooth muscle in the walls of blood vessels, or platelets
causes a releases of chemicals which causes a release of chemicals which causes vasoconstriction
the tunica media and smooth muscle encircling veins/arteries, constricts -> reducing blood flow and loss; lasts about 30 min.
Platelet Plug Formation
if platelets come in contact with collagen fibers in a damaged vessel’s walls…a chemical change occurs
the platelets become sticky, clinging to each other and to the damaged area forming a plug
Coagulation - forming a clot
a clot is a mesh of protein fibers in which formed elements are trapped
a series of reactions begins simultaneously with platelet plug formation
essentially liquid protein fibers that are present in blood plasma solidify and form a mesh over the damaged area creating a “permanent plug” (until healing occurs)
meanwhile the fibers in the plug shrink, tightening and closing the wound
Clotting in an unbroken vessel
the clot is called a thrombus unless it breaks free and moves through the blood and then it is called an embolus
if it drifts until it blocks a smaller vessel, this is an embolism
may lead to heart attack, stroke, pulmonary embolism, or tissue death
Infarction = obstruction of the blood supply to an organ or region of tissue, typically by a thrombus or embolus, causing local death of the tissue; can cause heart attack etc.
Human Blood Groups
Erythrocyte membranes bear different many antigens
Antigen : anything perceived as foreign that can generate an immune response
Erythrocyte antigens are referred to as agglutiongens because they promote agglutination
Mismatched transfused blood is perceived as foreign and may be agglutinated and destroyed
Potentially fatal reaction
NOTE: Only red blood cell transfusions are included in this context, and does NOT include the plasa in the transfusion
Humans have at least 30 naturally occurring RBC antigens
Presence or absence of each antigen is used to classify blood cells into different groups
Antigens of ABO and Rh bloo groups cause most vigorous transfusion reactions; therefore, they are major groups typed
ABO Blood Groups
Based on presence or absence of two aggultinogens (A and B) on surface of RBCs
Type A : has only A agglutinogen
Type B : has only B agglutinogen
Type AB : has both A and B agglutinogens
Type O : has neither A nor B agglutinogens
Blood may contain preformed anti-A or anti- B antibodies (agglutinins
Type A : has anti-B agglutinins
Type B : has anti-A agglutinins
Type AB : has no agglutinins
Type O : has both anti-A and anti-B agglutinins
These agglutinins act against transfused red blood cells with antigens not present on recipient's red blood cells
Rh Blood Group
Rh+ indicates presence of D agglutinogen (one of the “Rh” factors
85% Americans are Rh+
Rh- indicates absence of D agglutinogen
Anti-D antibodies are not spontaneously formed in Rh– individuals
Anti-D antibodies form if Rh– individual receives Rh+ blood, or Rh– mom is carrying Rh+ fetus
If an Rh- recieves Rh+ blood, either from a transfusion or from carrying an Rh+ fetus, the immune system becomes sensitized and begins producing anti-D (anti-Rh) antibodies
Hemolysis does not occur after the first transfusion because it takes time for the body to react and start making antibodies
Second exposure to Rh+ blood will result in typical transfusion reaction
Rh Blood Group and Pregnancy
Hemolytic disease of newborn only occurs in Rh– mom with Rh+ fetus
First pregnancy: Rh– mom exposed to Rh+ blood of fetus during delivery; first baby born healthy, but mother synthesizes anti-Rh antibodies
Second pregnancy: Mom’s anti-Rh antibodies cross placenta and destroy RBCs of Rh+ baby
Treatment involves:
Baby treated with prebirth transfusions and exchange transfusions after birth
RhoGAM serum is a medicine that stops the mother’s blood from making antibodies that attack Rh+ blood cells: prevents Rh- mother’s immune system from becoming sensitized during the first pregancy
Blood Transfusions
Cardiovascular system minimizes effects of blood loss by:
reducing volume of affected blood vessels
stepping up production of RBCs
Body can compensate for only so much blood loss
Loss of 15–30% causes paleness and weakness
Loss of more than 30% results in potentially fatal severe shock
Transfusing Red Blood Cells
Whole-blood transfusions: are used only when blood loss is rapid and substantial
Infusions of packed red blood cells, or PRBCs (plasma and WBCs removed), are preferred to restore oxygen-carrying capacity
Blood banks usually separate donated blood into components; shelf life of blood is about 35 days
Human blood groups of donated blood must be determined because transfusion reactions can be fatal
Transfusion Reactions
Occur if mismatched blood is infused
Donor’s cells are attacked by recipient’s plasma agglutinins
Agglutinate and clog small vessels
Rupture and release hemoglobin into bloodstream
Result in:
Diminished oxygen-carrying capacity
Decreased blood flow beyond blocked vessel
Hemoglobin in kidney tubules can lead to renal failure
Symptoms: fever, chills, low blood pressure, rapid heartbeat, nausea, vomiting
Treatment: preventing kidney damage with fluids and diuretics to wash out hemoglobin
Cardiovascular System- Blood vessels
Blood vessels
Delivery system of dynamic structures that begins and ends at heart
Work with lymphatic system to circulate fluids
Arteries : carry blood away from heart; oxygenated except for pulmonary circulation and umbilical vessels of fetus (where deoxygenated blood leaves the heart and head’s back to mother’s blood)
Capillaries : direct contact with tissue cells; directly serve cellular needs
Veins : carry blood toward heart; deoxygenated except for pulmonary circulation and umbilical vessels of fetus (where oxygenated blood from mother goes toward the heart of fetus)
Structure of Blood Vessel Wall
All vessels consist of a lumen, central blood-containing space, surrounded by a wall
Walls of all vessels, except capillaries, have three layers, or tunics:
Tunica intima
Tunica media
Tunica externa
Capillaries have endothelium only
Tunica intima
Innermost layer that is in “intimate” contact with blood
Endothelium: simple squamous epithelium that lines lumen of all vessels
Continuous with endocardium
Slick surface reduces friction
Subendothelial layer: connective tissue basement membrane
Tunica media
Middle layer composed mostly of smooth muscle and sheets of elastin
Nerve fibers innervate this layer, controlling:
Vasconstriction: decreased lumen diameter
Vasodilation: increased lumen diameter
Tunica externa
Outermost layer of wall composed mostly of loose collagen fibers that protect and reinforce wall and anchor it to surrounding structures
Arteries
Types of Arteries
Elastic Arteries: thick-walled with large, low-resistance lumen
Arota and its major branches: also called conducting arteries because they conduct blood from heart to medium sized vessels
Elastin found in all three tunics, mostly tunica media
Contain substantial smooth muscle, but inactive in vasoconstriction
Act as pressure reservoirs that expand and recoil as blood is ejected from heart
Allows for continous blood flow downstream between heartbeats
Muscular Arteries
Elastic arteries give rise to muscular arteries
Also called distributing arteries because they deliver blood to body organs
Diameters range from pinky-finger size to pencil-lead size
Account for most of named arteries
Have thickest tunica media with more smooth muscle, but less elastic tissue
Active in vasoconstriction
Arterioles
Smallest of all arteries
Larger arterioles contain all three tunics
Smaller arterioles are mostly single layer of smooth muscle surrounding endothelial cells
Control flow into capillary beds via vasodilation and vasoconstriction of smooth muscle
Also called resistance arteries because changing diameters change resistance to blood flow
Lead to capillary beds
Capillaries
Microscopic vessels; diameters so small only single RBC can pass through at a time
Walls just thin tunica intima; in smallest vessels, one cell forms entire circumference
Pericytes: spider-shaped stem cells help stabilize capillary walls, control permeability, and play a role in vessel repair
Functions: exchange of gases, nutrients, wastes, hormones, etc., between blood and interstitial fluid
Types of Capillaries
Continous capillaries
Abundant in skin, muscles, lungs, and CNS
Continuous capillaries of brain are unique
Form blood brain barrier, totally enclosed with tight junctions and no intercellular clefts
Fenestrated capillary
Found in areas involved in active filtration (kidneys), absorption (intestines), or endocrine hormone secretion
Endothelial cells contain Swiss cheese–like pores called fenestrations
Allow for increased permeability
Fenestrations usually covered with very thin diaphragm of extraceullular glycoproteins, but has little effect on solute and fluid movement
Sinusoidal capiilaries
Fewer tight junctions; usually fenestrated with larger intercellular clefts; incomplete basement membranes
Found only in the liver, bone marrow, spleen, and adrenal medulla
Blood flow is sluggish—allows time for modification of large molecules and blood cells that pass between blood and tissue
Contain macrophages in lining to capture and destroy foreign invaders
Capillary Beds
Capillary bed: interwoven network of capillaries between arterioles and venules
True capillaries: 10 to 100 exchange vessels per capillary bed
Precapillary sphincters regulate blood flow into true capillaries
Regulated by local chemical conditions and vasomotor nerves
Capillary Exchange of Gases and Nutrients
Many molecules pass by diffusion between blood and interstitial fluid
Move down their concentration gradients
Molecules use four different routes to cross capillary:
Diffuse directly through endothelial membranes
Example: lipid-soluble molecules such as respiratory gases
Pass through clefts
Example: water-soluble solutes
Pass through fenestrations
Example: water-soluble solutes
Active transport via pinocytotic vesicles
Example: larger molecules, such as proteins
Bulk Flow
Fluid is forced out clefts of capillaries at arterial end, and most returns to blood at venous end
Direction and amount of fluid flow depend on two opposing forces
Hydrostatic pressure
Force exerted by fluid pressing against wall
Capillary blood pressure that tends to force fluids through capillary walls
Greater at arterial end of bed than at venule end
Colloid osmotic pressure
Capillary colloid osmotic pressure is a “sucking” pressure created by nondiffusible plasma proteins pulling water back in to capillary
Veins
Veins:
Carry blood toward the heart
Formed when venules (small veins) converge
Have all tunics, but thinner walls with large lumens compared with corresponding arteries
Tunica media is thin, but tunica externa is thick
Large lumen and thin walls make veins good storage vessels
Called capacitance vessels (blood reservoirs) because they contain up to 65% of blood supply
Blood pressure lower than in arteries, so adaptations ensure return of blood to heart
Large-diameter lumens offer little resistance
2 factors that assist in venous blood flow:
Valves
veins have backflow-preventing valves (if faulty they become varicose veins)
Muscle Contractions
when the skeletal muscles which surround veins contract, they squeeze the veins, pushing blood from valve to valve
Pulse
The alternating expansion and elastic recoil of artery wall
so it is a reflection of ventricular systole and diastole
pulse = heart rate = ~70-80 bpm (beats per min)
Blood Pressure
the pressure (as measured in standardized arteries) exerted by the left ventricle during systole, and the pressure remaining during ventricular diastole
average BP for a young adult is 120/80 (systolic/diastolic)
sytolic BP is the force during contraction
diastolic BP is the force during relaxation
the difference between the two numbers is a measure of the arteries elastic recoil and it thus is indicative of the condition or health of the artery
Major Factors Influencing Blood Pressure:
Cardiac output- the blood flow of the entire circulation; affected by heart rate and strength of contraction can be regulated both neurally and hormonally
Blood volume- by regulating the water content of blood plasma the kidneys regulate the blood’s volume and therefore its pressure
this is accomplished through several hormones
Resistance- by dilating (getting bigger), or constricting, blood vessels will alter pressure
likewise blood can be diverted (moved) to or from areas affecting its pressure
many hormonal and neural controls are involved
Problems with blood pressure:
Hypotension- low blood pressure
Below 100 systolic
Hypertension- high blood pressure
Above 130/90
The Cardiovascular System: The Heart
Heart Anatomy
The Pulmonary and Systemic Circuits
Heart is a transport system consisting of two side-by-side pumps
Right side receives oxygen-poor blood from tissues
Pumps blood to lungs to get rid of CO2, pick up O2, via pulmonary circuit
Left side receives oxygenated blood from lungs
Pumps blood to body tissues via systemic circuit
Receiving chambers of heart
Right atrium
Receives blood returning from systemic circuit
Left atrium
Receives blood returning from pulmonary circuit
Pumping chambers of heart
Right ventricle
Pumps blood through pulmonary circuit
Left ventricle
Pumps blood through systemic circuit
Size and Location
Approximately the size of a fist
Weighs less than 1 pound
Location
In mediastinum between second rib and fifth intercostal space
On superior surface of diaphragm
Two-thirds of heart to left of midsternal line
Anterior to vertebral column, posterior to sternum
Coverings of the Heart
Pericardium:
Superficial fibrous pericardium: functions to protect, anchor heart to surrounding structures, and prevent overfilling
Deep two-layered serous pericardium
Parietal layer lines internal surface of fibrous pericardium layer lines internal surface of fibrous pericardium
Visceral layer layer (epicardium) on external surface of heart
Two layers separated by fluid-filled pericardial cavity (decreases friction)
Three Layers of Heart Wall
Epicardium: visceral layer of serous pericardium
Myocardium: circular or spiral bundles of contractile cardiac muscle cells
Cardiac skeleton: crisscrossing, interlacing layer of connective tissue
Anchors cardia muscle fibers
Supports great vessels and valves
Limits spread of action potientals
Endocardium: innermost layer; is continuous with endothelial lining of blood vessels
Lines heart chambers and covers cardiac skeleton of valves
Chambers and Associated Great Vessels
Internal features
Four chambers
Two superior atria
Two inferior ventricles
Interatrial septum: separates atria
Fossa ovalis: remnant of foramen ovale of fetal heart
Interventricular septum: separates ventricles
Foramen ovale: Before a baby is born, it does not use its lungs to get blood rich in oxygen. Instead, this blood comes from the mother’s placenta and is delivered through the umbilical cord. The foramen ovale makes it possible for the blood to go from the veins to the right side of the fetus’ heart, and then directly to the left side of the heart, bypassing the pulmonary circuit.
Surface features
Coronary sulcus (atrioventricular groove)
Encircles junction of atria and ventricles
Anterior interventricular sulcus
Anterior position of interventricular septum
Posterior interventricular sulcus
Landmark on posteroinferior surface
Atria: the receiving chambers
Small, thin-walled chambers; contribute little to propulsion of blood
Auricles: appendages that increase atrial volume
Right atrium: receives deoxygenated blood from body
Three veins empty into right atrium:
Superior vena cava: returns blood from body regions above the diaphragm
Inferior vena cava: returns blood from body regions below the diaphragm
Coronary sinus: returns blood from coronary circulation
Left atrium: receives oxygenated blood from lungs
Four pulmonary veins return blood from lungs
Ventricles: the discharging chambers
Make up most of the volume of heart
Thicker walls than atria
Right ventricle
Pumps blood into pulmonary trunk
Left ventricle
Pumps blood into aorta (largest artery in body)
Papillary muscles: project into ventricular cavity
Anchor chordae tendineae that are attached to atrioventricular valves
Heart Valves
Ensure unidirectional blood flow through heart
Open and close in response to pressure changes
Two major types of valves
Atrioventricular valves: located between atria and ventricles
Semilunar valves: located between ventricles and major arteries
No valves are found between major veins and atria; not a problem because:
Inertia of incoming blood prevents backflow
Heart contractions compress venous openings
Atrioventricular (AV) Valves
Two atrioventricular (AV) valves prevent backflow into atria when ventricles contract
Tricuspid valve (right AV valve): made up of three cusps and lies between right atria and ventricle
Bicuspid (also, Mitral) valve (left AV valve): made up of two cusps and lies between left atria and ventricle
Chordae tendineae: anchor cusps of AV valves to papillary muscles that function to:
Hold valve flaps in closed position
Prevents flaps from everting back into atria
Semilunar (SL) valves
Two semilunar (SL) valves prevent backflow from major arteries back into ventricles
Open and close in response to pressure changes
Each valve consists of three cusps that roughly resemble a half moon
Pulomary semilunar valve: located between right ventricle and pulmonary trunk
Aortic semilunar valve: located between left ventricle and aorta
Homeostatic Imbalance
Two conditions severely weaken heart:
Incompetent valve
Blood backflows so heart repumps same blood over and over
Valvular stenosis
Stiff flaps that constrict opneing
Heart needs to exert more force to pump blood
Defective valve can be replaced with mechanical, animal, or cadaver valve
Pathway of Blood Through Heart
Right side of the heart
Superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (vein in coronary circulation)→
Right atrium→
Tricuspid valve→
Right ventricle→
Pulmonary semilunar valve →
Pulmonary trunk→
Pulmonary arteries→
Lungs – Pulmonary circulation
Left side of the heart
Four pulmonary veins →
Left atrium→
Bicuspid valve→
Left ventricle→
Aortic semilunar valve→
Aorta→
Systemic circulation
Equal volumes of blood are pumped to pulmonary and systemic circuits
Pulmonary circuit is short, low-pressure circulation
Systemic circuit is long, high-friction circulation
Anatomy of ventricles reflects differences
Left ventricle walls are 3× thicker than right
Pumps with greater pressure
Coronary Circulation
Coronary circulation
Functional blood supply to heart muscle itself
Shortest circulation in body
Delivered when heart is relaxed
Left ventricle receives most of coronary blood supply
Coronary arteries
Both left and right coronary arteries arise from base of aorta and supply arterial blood to heart
Both encircle heart in coronary sulcus
Branching of coronary arteries varies among individuals
Coronary veins
Cardiac veins collect blood from capillary beds
Coronary sinus empties into right atrium; formed by merging cardiac veins
Homeostatic Imbalance
Angina pectoris
Thoracic pain caused by fleeting deficiency in blood delivery to myocardium
Cells are weakened
Myocardial infraction (heart attack)
Prolonged coronary blockage
Areas of cell death are repaired with noncontractile scar tissue
Cardiac Muscle Fibers
Microscopic Anatomy
Cardiac muscle cells: striated, short, branched, fat, interconnected
One central nucleus (at most, 2 nuclei)
Contain numerous large mitochondria (25–35% of cell volume) that afford resistance to fatigue
Rest of volume composed of sarcomeres
Intercalated discs are connecting junctions between cardiac cells that contain:
Desmosomes: filaments hold cells together; prevent cells from separating during contraction
Gap junctions: allow ions to pass from cell to cell; electrically couple adjacent cells
Allows heart to be a functional syncytium, a single coordinated unit
Electrical Events of the Heart
Heart depolarizes and contracts without nervous system stimulation
The Intrinsic Conduction System
Coordinated heartbeat is a function of:
Presence of gap junctions
Intrinsic cardiac conduction system
Network of noncontractile (autorhythmic) cells
Initiate and distribute impulses to coordinate depolarization and contraction of heart
“Intrinsic” = originating and included wholly within an organ or part
Sequence of Excitation
Cardiac pacemaker cells pass impulses, in following order, across heart in ~0.22 seconds
Sinoatrial (SA) node
Pacemaker of heart in right atrial wall
Depolarizes faster than rest of myocardium
Generates impulses about 75×/minute (sinus rhythm)
Inherent rate of 100×/minute tempered by extrinsic factors, such as when running to catch a bus
Impulse spreads across atria, and to AV node
Atrioventricular (AV) node
In inferior interatrial septum
Delays impulses approximately 0.1 second
Because fibers are smaller in diameter, have fewer gap junctions
Allows atrial contraction prior to ventricular contraction
Atrioventricular (AV) bundle
In superior interventricular septum
Only electrical connection between atria and ventricles
Atria and ventricles not connected via gap junctions
Atria and ventricles not connected via gap junctions
Two pathways in interventricular septum
Carry impulses toward apex of heart
Subendocardial conducting network
Complete pathway through interventricular septum into apex and ventricular walls
More elaborate on left side of heart
Ventricular contraction immediately follows from apex toward atria
Process from initiation at SA node to complete contraction takes ~0.22 seconds
Homeostatic Imbalance
Defects in intrinsic conduction system may cause:
Arrhythmias: irregular heart rhythms
Uncoordinated atrial and ventricular contractions
Fibrillation: rapid, irregular contractions
Heart becomes useless for pumping blood, causing circulation to cease; may result in brain death
Treatment: defibrillation interrupts chaotic twitching, giving heart “clean slate” to start regular, normal depolarizations
To reach ventricles, impulse must pass through AV node
If AV node is defective, may cause a heart block
Few impulses (partial block) or no impulses (total block) reach ventricles
Ventricles beat at their own intrinsic rate
Too slow to maintain adequate circulation
Treatment: artificial pacemaker, which recouples atria and ventricles
Electrocardiography
Electrocardiograph can detect electrical currents generated by heart
Electrocardiogram (ECG or EKG) is a graphic recording of electrical activity
Composite of all action potentials (cause muscle contraction) at given time; not a tracing of a single AP
Electrodes are placed at various points on body to measure voltage differences
12 lead ECG is most typical, which is an electrocardiogram that gathers information from 12 different areas of the heart
Main features:
P wave: depolarization of SA node and atria
Depolarization - contraction occurs
QRS complex: ventricular depolarization and atrial repolarization
T wave: ventricular repolarization
P-R interval: beginning of atrial excitation to beginning of ventricular excitation
S-T segment: entire ventricular myocardium depolarized
Q-T interval: beginning of ventricular depolarization through ventricular repolarization
Homeostatic Imbalance
Changes in patterns or timing of ECG may reveal diseased or damaged heart, or problems with heart’s conduction system
Problems that can be detected:
Enlarged R waves may indicate enlarged ventricles
Elevated or depressed S-T segment indicates cardiac ischemia
Ischemia = inadequate blood supply
Prolonged Q-T interval reveals a repolarization abnormality that increases risk of ventricular arrhythmias
Junctional blocks, blocks, flutters, and fibrillations are also detected on ECG
Mechanical Events of Heart
Mechanical Events
Systole: period of heart contraction
Diastole: period of heart relaxation
Cardiac cycle: blood flow through heart during one complete heartbeat
Atrial systole and diastole are followed by ventricular systole and diastole
Cycle represents series of pressure and blood volume changes
Mechanical events follow electrical events seen on ECG
Three phases of the cardiac cycle (following left side, starting with total relaxation)
Ventricular filling
Pressure is low; 80% of blood passively flows from atria through open AV valves into ventricles from atria (SL valves closed)
Atrial depolarization triggers atrial systole (P wave), atria contract, pushing remaining 20% of blood into ventricle
Depolarization spreads to ventricles (QRS wave)
Artia finish contracting and return to diastole while ventricles begin systole
Ventricular systole
Artia relax; ventricles begin to contract
Rising ventricular pressure causes closing of AV vavles
Ventricular pressure exceeds pressure in large arteries, forcing SL valves open
Isovolumetric relaxation: early diastole
Following ventricular repolarization (T wave), ventricles are relaxed; atria are relaxed and filling
Backflow of blood in aorta and pulmonary trunk closes SL valves
Ventricles are totally closed chambers (isovolumetric, or “unchanging volume”)
When atrial pressure exceeds ventricular pressure, AV valves open; cycle begins again
Regulation of Heart Rate
Heart rate can be regulated by:
Autonomic Nervous System
Sympathetic nervous system can be activated by emotional or physical stressors
Norepinephrine is released causes:
Pacemaker to fire more rapidly, increasing HR
Increased contractility
Parasympathetic nervous system opposes sympathetic effects
Acetylcholine hyperpolarizes pacemaker cells by opening K+ channels, which slows HR
Has little to no effect on contracility
Chemical regulation
Hormones
Epinephrine from adrenal medulla increases heart rate and contractility
Thyroxine (the T4 thyroid hormone) increases heart rate; enhances effects of norepinephrine and epinephrine
Ions
Intra- and extracellular ion concentrations (e.g., Ca2+ and K+) must be maintained for normal heart function
Imbalances are very dangerous to heart
Other factors that influence heart rate
Age
Fetus has fastest HR; declines with age
Gender
Females have faster HR than males
Exercise
Increases HR
Trained athletes can have slow HR
Body temperature
HR increases with increased body temperature
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