lpn-c unit two anatomy and physiology of the circulatory, pulmonary, and renal system
TRANSCRIPT
LPN-CLPN-C
Unit Two
Anatomy and Physiology of the Circulatory,
Pulmonary, and Renal System
Circulatory, Circulatory, Pulmonary, Pulmonary, and Renal and Renal
SystemSystem
The HeartThe Heart
The HeartThe HeartApex◦Points forward, downward, and to the left at the 4th or 5th intercostal space
Base◦“Broad” side that faces upward
The heart is 12cm long and 8cm wide at its base, and is 6cm thick
The heart weighs an average of 280g, and weighs more in men than in women
The layers of the heart are the pericardium, epicardium, myocardium, and endocardium
The Heart (cont’d)The Heart (cont’d)The pericardium is a fibroserous sac
that surrounds the heart and the roots of the great vessels; it provides the heart with physical protection and a barrier to infection
The epicardium is known as the visceral layer, and covers the entire heart and great vessels; the epicardium also forms the parietal layer that lines the pericardium
The myocardium is the muscular portion of the heart, which forms the walls of the atria and ventricles
The Heart (cont’d)The Heart (cont’d)The endocardium is a thin, 3-layered membrane that lines the heart.◦Inner layer = smooth endothelial cells supported by connective tissue
◦Middle layer = dense connective tissue
◦Outer layer = irregularly arranged connective cells
There are 4 chambers of the heart◦Right and left atrium◦Right and left ventricle
The Heart (cont’d)The Heart (cont’d)The right atrium receives deoxygenated blood from the superior vena cava, inferior vena cava, and coronary sinus
The left atrium receives oxygenated blood from the pulmonary veins
Blood is emptied into the ventricles from the atria during diastole
The ventricles are thick, muscular walls that make up the bulk of the heart
A septum separates the ventricles and extends between the atria, dividing the heart into the right and left sides
The Heart (cont’d)The Heart (cont’d)The great vessels of the heart are the superior vena cava, the inferior vena cava, the coronary sinus, pulmonary arteries, pulmonary veins, and the aorta
Superior Vena Cava◦2nd largest vein in the body◦Returns deoxygenated blood from the upper half of the body to the right atrium
◦2cm in diameter and 7cm longInferior Vena Cava◦Returns deoxygenated blood to the heart from parts of the body below the diaphragm
The Heart (cont’d)The Heart (cont’d)Coronary Sinus◦Drains 5 coronary veins through a single semilunar valve
◦Coronary veins include the great cardiac vein, the small cardiac vein, the middle cardiac vein, the posterior vein of the left ventricle, and the oblique vein of the left atrium
Pulmonary Arteries◦Deoxygenated blood leaves the right heart through the pulmonary artery, which divides into the left pulmonary artery (which enters the left lung) and the right pulmonary artery (which enters deoxygenated blood into the right lung)
The Heart (cont’d)The Heart (cont’d)
Pulmonary Veins◦One of two pairs of large vessels that return oxygenated blood from each lung to the left atrium of the heart
Aorta◦The main trunk of arterial circulation; consists of 4 parts
◦Ascending aorta◦Arch of the aorta◦Thoracic aorta◦Abdominal aorta
The Heart (cont’d)The Heart (cont’d)Valves of the heart --Atrioventricular (AV) valves◦Control the flow of blood between the atria and the ventricles
◦Form cusps: 2 on the left side of the heart (bicuspid, or mitral, valve) and 3 on the right side of the heart (tricuspid valve)
◦Supported by papillary muscles, which project from the walls of the ventricles, and chordae tendinae, which are chord-like structures that prevent the AV valves from reverting into the atria during systole
The Heart (cont’d)The Heart (cont’d)Valves of the heart --Semilunar valves◦The aortic valve controls the flow of blood into the aorta
◦The pulmonic (or pulmonary) valve controls the flow of blood into the pulmonary artery
The Heart (cont’d)The Heart (cont’d)Blood supply of the heart –2 coronary arteries that arise from the coronary sinus, just above the aortic valve
The left coronary artery extends for 3½cm, then divides into the anterior descending artery and the circumflex branch◦Anterior descending artery
Passes between the two ventricles Forms diagonal branches, which supply the
left ventricle Forms perforating branches, which supply
the anterior portion of the heart
The Heart (cont’d)The Heart (cont’d)Blood supply of the heart –◦Circumflex branch
Passes through the left and moves posteriorly in the groove that separates the left atrium and ventricle
Forms branches that supply the left lateral wall of the left ventricle
The right coronary artery lies in the right AV groove, and its branches supply the right ventricle; the right coronary artery moves to the back of the heart, where it forms the posterior descending artery, which supplies the interventricular septum, AV node, and posterior papillary muscle
The Heart (cont’d)The Heart (cont’d)The conduction system –Sinoatrial (SA) node◦Pacemaker of the heart◦Located in the right atrium, next to the superior vena cava
◦Impulses initiated at the SA node at an intrinsic rate of 60-100 beats per minute
Atrioventricular (AV) node◦Connects the two conduction systems
Atrial activity Ventricular activity
◦Provides a “one-way” conduction between the atria and ventricles
The Heart (cont’d)The Heart (cont’d)The conduction system –Bundle of His (AV Bundle)◦Causes a delay in conduction that provides a mechanical advantage by allowing the atria to complete their ejection of blood before ventricular contraction begins
◦Penetrates into the ventricles and divides into the right and left bundle branches
◦The bundle branches subdivide into the Purkinje fibers, which branch out and supply the outer walls of the ventricles
◦The Purkinje system supplies rapid conduction and excitation of the right and left ventricles
The Heart (cont’d)The Heart (cont’d)The physiology of the cardiac cycle –The cardiac cycle refers to the events related to the flow of blood that occur from the beginning of one heartbeat to the beginning of the next; used to describe the pumping action of the heart◦Isometric ventricular relaxation = both ventricles are relaxed and both AV and semilunar valves are closed
◦Ventricular filling = AV valves open and blood fills the ventricles
◦Ventricular contraction = blood is forced out of the ventricles
The Heart (cont’d)The Heart (cont’d)The physiology of the cardiac cycle –Systole = contraction of the ventricles◦Atrial systole is the contraction of the atria of the heart that precedes ventricular contraction by a fraction of a second
◦Ventricular systole is the contraction of the ventricles, which begins with the closure of the AV valves
Diastole = relaxation of the ventricles during which they are filling with blood◦Ventricular diastole marks the closure of the semilunar valves; this constitutes ventricular filling
The Heart (cont’d)The Heart (cont’d)The physiology of cardiac output –Cardiac output = the output of blood by the heart per minute; determined by the stroke volume and the heart rate
Heart rate = the frequency with which blood is ejected from the heart; as the heart rate increases, cardiac output tends to increase
Stroke volume = the amount of blood pumped by the left ventricle of the heart in one contraction; this is not all the blood contained in the ventricle
The Heart (cont’d)The Heart (cont’d)The physiology of cardiac output –Preload = the amount of blood that the heart must pump with each beat at the end of diastole; measured by central venous pressure or “pulmonary wedge pressure”
Afterload = the pressure or tension that impedes the flow of blood out of the heart
Cardiac contractility = the ability of muscle tissue to contract when its thick (myosin) and thin (actin) filaments slide past each other
The Heart (cont’d)The Heart (cont’d)Heart rate regulation –Autonomic regulation of cardiac function◦Parasympathetic nervous system
Regulates heart rate through the vagus nerve: increased vagal activity produces a slowing of the heart rate
Acts to conserve energy, promote bowel/bladder elimination, pupil contraction, etc
◦Sympathetic nervous system Excitatory influence on heart rate and
contractility Increases blood pressure and blood
sugar, dilates bronchioles and pupils (i.e. “fight-or-flight” response)
The Heart (cont’d)The Heart (cont’d)Heart rate regulation –Electrolytes◦Sodium
Due to fluid retention in the blood vessels from high levels of sodium (hypernatremia), the heart has to work harder to pump blood to the body
◦Potassium Both hypo- and hyperkalemia can have
profound effects on cardiac contractility High levels of serum potassium can result
in tachycardia, then bradycardia, and death
Low levels of serum potassium can result in bradycardia and death
Important electrolyte for patients on diuretics or heart medications
The Heart (cont’d)The Heart (cont’d)Heart rate regulation –Electrolytes◦Calcium
Necessary for muscle contractility, cardiac function, neural transmission, and blood clotting
Body Temperature◦Hyperthermia can lead to tachycardia, cardiac dysrhythmias, labile blood pressure, postural instability
◦Hypothermia can result in a gradual decline in heart rate and cardiac output Blood pressure initially rises, then falls Dysrhythmias Ventricular fibrillation
The Heart (cont’d)The Heart (cont’d)Heart rate regulation –Emotions: the average person’s heart rate increases with any intense emotion, including anger, fear, happiness, and anxiety
Gender: a woman’s heart rate is typically higher than that of a man because the female heart is smaller, requiring more beats to pump the same amount of blood
Age: the heart rate decreases with age; the average heart rate is 60-80 beats per minute, whereas an infant’s is much faster and an elderly person’s is slower
The Heart (cont’d)The Heart (cont’d)Veins and arteries –
What is the Difference?Arteries take blood away from the heart, whereas veins bring blood back to the heart; generally speaking, blood found in arteries is oxygenated, and blood found in veins is deoxygenated; the exception is the pulmonary arteries, which carry deoxygenated blood from the heart to the lungs, and the pulmonary veins, which carry oxygenated blood from the lungs to the heart
The Heart (cont’d)The Heart (cont’d)Veins and arteries –Arteries◦Tough, elastic tubes that divide into smaller vessels as they move away from the heart
◦Must be able to withstand immense pressure as they receive blood directly from the heart
◦The largest artery in the body is the aorta, which originates from the heart and branches out into smaller arteries
◦The smallest arteries are termed arterioles◦Intra-arterial pressure is the force applied against the walls of the arteries as the heart pumps blood through the body
The Heart (cont’d)The Heart (cont’d)Veins and arteries –Veins◦Elastic vessels that transport blood to the heart
◦The smallest veins in the body are called venules
◦Venules receive blood from the arteries via arterioles and capillaries, then branch into larger veins which carry the blood to the largest vein in the body, the vena cava
◦The vena cava transports blood directly to the right atrium of the heart
◦Intravenous pressure is the pressure in the veins and is difficult to measure noninvasively
Veins Arteries
The Heart (cont’d)The Heart (cont’d)Veins and arteries –Venous and arterial walls◦The walls of both the arteries and the veins consist of 3 layers, the tunica adventitia, tunica media, and tunica intima
◦In arteries, the tunica intima has an elastic membrane lining
◦In most veins, the tunica intima contains valves, which are flap-like structures that allow blood to flow in only one direction
Capillaries are located within the tissues of the body and transport blood from the arterioles to the venules; walls are very thin
Identify the location of veins in the upper torso commonly used for central line and peripheral
line insertion:
JugularSubclavian
Superior Vena CavaBasilic
CephalicDorsal Metacarpal
1) Digital dorsal vein2) Dorsal metacarpal vein3) Dorsal venous network4) Cephalic vein5) Basilic vein
The LungsThe Lungs
The LungsThe LungsThe respiratory system consists of air passages where gas exchange takes place
Air passages are divided into conducting airways and respiratory tissues◦Conducting airways are passages through which air moves as it passes into and out of the lungs; consists of the mouth, nasal passages, nasopharynx, larynx, and the tracheobronchial tree (trachea, bronchi, and bronchioles)
◦Respiratory tissues are the functional unit of the lungs; this is where gas exchange actually occurs; consists of the respiratory bronchioles, alveoli, and pulmonary capillaries
The Lungs (cont’d)The Lungs (cont’d)Conducting airways --Air is warmed, filtered, and humidified as it passes through the conducting airways
The trachea divides to form the right and left primary bronchi
The primary bronchi divide into secondary (or lobular) bronchi, which supply each of the lobes of the lung
The secondary bronchi branch to form smaller bronchi, which are named terminal bronchioles; these are the smallest of the conducting airways
The Lungs (cont’d)The Lungs (cont’d)Respiratory tissues --The lungs are the functional structures of the respiratory system; they activate substances such as bradykinin, which is a potent vasodilator, and convert angiotensin 1 to angiotensin 2 (which is a potent vasoconstrictor)
If the lungs are the functional structures of the respiratory system, then lobules are the functional units of the lungs; lobules consist of respiratory bronchioles, alveoli, and pulmonary capillaries
The Lungs (cont’d)The Lungs (cont’d)Respiratory tissues --Oxygen from the alveoli diffuses across the alveolar capillary membrane into the blood; carbon dioxide from the blood diffuses into the alveoli
The Lungs (cont’d)The Lungs (cont’d)Inhalation and exhalation --Inhalation (inspiration): the diaphragm, assisted by external intercostal muscles, causes the size of the chest cavity to increase; intrathoracic pressure becomes more negative; air is drawn into the lungs
Exhalation (expiration): occurs as the elastic components of the chest wall and lung structures that were stretched during inspiration recoil, which causes the size of the chest cavity to decrease and the intrathoracic pressure to increase
The Lungs (cont’d)The Lungs (cont’d)Inhalation and exhalation --The act of breathing normally is effortless and does not require conscious thought
Normal rate of respiration is usually between 16-18 breaths per minute, which is approximately 1 breath for every 4 heartbeats
In normal breathing, expiration is largely passive, and is accomplished within 4-6 seconds
Movements are smooth, with equal expansion bilaterally
The Lungs (cont’d)The Lungs (cont’d)Inhalation and exhalation --Gender plays a role in the act of breathing◦In men, respiratory movements are diaphragmatic
◦In women, there is greater movement of the intercostal muscles
When breathing becomes labored, the accessory muscles of the neck are used, and nostrils may flare
The suffix “pnea” refers to breathing◦Tachypnea = rapid breathing◦Hyperpnea = increased rate/depth of breathing
The Lungs (cont’d)The Lungs (cont’d)Inhalation and exhalation –Hyperventilation causes excessive intake of oxygen and excessive elimination of carbon dioxide; leads to dizziness, faintness, and numbness to the fingers and toes
Hypoventilation is ventilation that is inadequate for alveolar-capillary exchange of carbon dioxide and oxygen; causes increased PaCO2 and hypoxia
The Lungs (cont’d)The Lungs (cont’d)Breath sounds --“Normal” breath sounds = bronchial sounds, bronchiovesicular sounds, and vesicular sounds
Abnormal (or adventitious) breath sounds are those that can not be categorized as “normal”◦Stridor = intense, continuous monophonic wheezes that are accentuated during inspiration; stridor can often be heard without a stethoscope; indicates upper airway obstruction
The Lungs (cont’d)The Lungs (cont’d)Breath sounds –Abnormal breath sounds –◦Wheezes (or rhonchi) = continuous musical tones most commonly heard at the end of inspiration or early expiration; indicate narrowed airway due to a thickening of reactive airway walls, or collapse of airways due to pressure from surrounding pulmonary disease
◦Pleural friction rub = low-pitched, grating or creaking sound that occurs when inflamed pleural surfaces rub together during respiration; more often heard on inspiration than expiration; may indicate pleural effusion, pneumothorax, bacterial pneumonia
The Lungs (cont’d)The Lungs (cont’d)Breath sounds –Abnormal breath sounds –◦Crackles (or rales) = discontinuous, explosive, popping sounds that originate within the airways; more common during inspiration than expiration; indicates accumulation of fluid secretions or exudate within the airways, or inflammation and edema in the pulmonary tissue Fine crackles = soft, high-pitched, and
very brief Course crackles = louder, lower in pitch,
and last longer than fine crackles
The Lungs (cont’d)The Lungs (cont’d)Breath sounds --Dyspnea = breathlessness, shortness of breath; this is a subjective sensation or a person’s perception of difficulty in breathing that includes the perception of labored breathing and the reaction to that sensation; observed in at least 3 major cardiopulmonary disease states◦Primary lung disease (pneumonia, asthma, emphysema)
◦Heart disease (pulmonary congestion)◦Neuromuscular disease (muscular dystrophy)
The Lungs (cont’d)The Lungs (cont’d)Breath sounds --Cheyne-Stokes respirations:
characterized by apnea, then deep, rapid breathing in a repeating cycle; results from decreased sensitivity to concentration of blood gases
Respiratory terms –P = pressurePO2 = partial pressure of oxygen
(partial pressure = the pressure that one component of a mixture of gases would exert if it were alone in a container)
PCO2 = partial pressure of carbon dioxide
The Lungs (cont’d)The Lungs (cont’d)Respiratory terms –SpO2 = peripheral oxygen
saturationSaO2 = arterial oxygen
saturationMonitoring respiratory status –Pulse oximetry measures oxygen
saturation (SpO2) and documents peripheral oxygen availability
X-ray identifies conditions compromising respiratory status, such as pneumonia
The KidneysThe Kidneys
The KidneysThe KidneysThe function of the kidneys is to
filter blood, selectively reabsorb the substances that are needed to maintain constancy of body fluid, and excrete metabolic waste
The kidneys are smaller than a fist, process approximately 1700L of blood, and combine its waste products into approximately 1.5L of urine
Responsible for long term regulation of arterial pressure through sodium and water balance
Activation of vitamin D (important for intestinal absorption of calcium)
The KidneysThe KidneysErythropoietin production (stimulates bone marrow production of red blood cells)
Initiates enzymatic processes related to biochemical synthesis of angiotensin 2, which is a vasoconstrictor hormone that increases sodium reabsorption via the proximal tubule
Nephrons are the functional unit of the kidney◦There are 1 million nephrons per kidney◦Each nephron is divided into 4 segments: the proximal convoluted tubule, the Loop of Henle, the distal convoluted tubule, and the collecting tubule
The Kidneys (cont’d)The Kidneys (cont’d)The proximal convoluted tubule drains the Bowman’s capsule
The Loop of Henle is a thin looped structure
The distal convoluted tubule is a distal coiled portion of the nephron
The collecting tubule joins with several tubules to collect the filtrate; urine concentration occurs in the collecting tubule under the influence of antidiuretic hormone
The Kidneys (cont’d)The Kidneys (cont’d)Antidiuretic hormone (ADH), also known as vasopressin, increases water retention by the kidneys, produces vasoconstriction of blood vessels, and is involved in the stress response through fluid loss
ADH maintains extracellular volume by returning water to the vascular compartment, producing concentrated urine by removing water from the tubular filtrate
The Kidneys (cont’d)The Kidneys (cont’d)Each nephron consists of a glomerulus, which is the site of blood filtration, electrolyte reabsorption, and elimination of unneeded materials
The glomerulus consists of a compact tuft of capillaries encased in a thin, double-walled capsule called the Bowman’s capsule
Blood flows into the glomerular capillaries from the afferent arteriole, and flows out of the glomerular capillaries into the efferent arteriole
The Kidneys (cont’d)The Kidneys (cont’d)Urine is typically clear and amber-colored, and consists of approximately 95% water and 5% dissolved solids
The kidneys normally produce an average of 1.5L of urine each day
Turbidity (cloudiness/haziness) of urine is clear to slightly hazy
Urine that is dark in color indicates high specific gravity with a small output of urine
Specific gravity compares the density of urine to that of water; provides information about hydration status and kidney function
The Kidneys (cont’d)The Kidneys (cont’d)The specific gravity of urine is 1.010
– 1.025 with normal fluid intakeHealthy kidneys can produce
concentrated urine with a specific gravity of 1.030 – 1.040
During periods of marked hydration, specific gravity can approach 1.000
Diminished renal function results in a loss of renal concentration ability, and specific gravity may fall to levels of 1.006 – 1.010
Urine pH ranges from 4.5 – 8, with an average of 6
The Kidneys (cont’d)The Kidneys (cont’d)
Blood chemistry –Blood urea nitrogen: 8.0 – 20.0 mg/dL
Creatinine: 0.7 – 1.5 mg/dLSodium: 135 – 145 mEq/LChloride: 98 – 106 mEq/LPotassium: 3.5 – 5.0 mEq/LCarbon dioxide: 24 – 29 mEq/L
The Kidneys (cont’d)The Kidneys (cont’d)Blood chemistry –Serum creatinine reflects the glomerular filtration rate (GFR)◦Product of creatine metabolism in muscles
◦The formation and release of creatinine is relatively constant and proportional to the amount of muscle mass
◦Creatinine clearance declines with age (decrease in muscle mass)
◦Indicator of renal function loss (i.e. if creatinine level doubles, the GFR and renal function has probably fallen to ½ its normal state)