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SOMAPL1C — The Heart

OBJ 2683 — Medical Vocabulary: The Cardiovascular System / Heart

Define medical vocabulary components related to the cardiovascular system and the heart.

Question 1 of 16

The root atrion means "hall." Which structure is named from this root?

A. Ventricle
B. Auricle
C. Atrium
D. Septum
E. Apex

Question 2 of 16

The root ventricle derives from the Latin word meaning:

A. Little wall
B. Little belly
C. Entry chamber
D. Half moon
E. Little ear

Question 3 of 16

The root auris means "ear." Which cardiac structure is named from this root because of its ear-like shape?

Question 4 of 16

The prefix bi- means "two." A valve is called bicuspid because it has:

A. Two papillary muscles
B. Two chordae tendineae
C. Two cusps (flaps)
D. Two chambers
E. Two layers of connective tissue

Question 5 of 16

The root bradys means "slow." A patient with a heart rate below 60 bpm is said to have:

Question 6 of 16

The root tachys means "swift." A heart rate of 100 bpm or more is called:

Question 7 of 16

The root luna means "moon." The pulmonary and aortic valves are called semilunar because their cusps are shaped like:

A. Full moons
B. Half-moons (crescents)
C. Stars
D. Triangles
E. Discs

Question 8 of 16

The root mitre refers to "a bishop's hat." The left AV valve is called the mitral valve because its shape resembles:

A. A crescent
B. A nipple
C. A wall
D. A bishop's hat
E. A point

Question 9 of 16

The root septum means "wall." Which two structures are separated by septa in the heart?

A. The two atria are separated by the interatrial septum

B. The ventricles are separated by the interventricular septum

C. The pericardial layers are separated by the cardiac septum

D. The coronary arteries are separated by a vascular septum

E. The valves are separated by the fibrous septum

Question 10 of 16

The root papilla means "nipple-shaped elevation." Papillary muscles are cone-shaped projections in the ventricle that connect to:

Question 11 of 16

The root diastole means "expansion." During diastole, the heart chamber:

A. Contracts and ejects blood
B. Reaches maximum pressure
C. Relaxes and fills with blood
D. Closes its semilunar valves
E. Depolarizes rapidly

Question 12 of 16

The root systole means "a drawing together." During systole, the heart chamber:

A. Contracts and squeezes blood into the next chamber or vessel
B. Expands to receive incoming blood
C. Repolarizes
D. Reduces pressure to open AV valves
E. Passively fills from venous return

Question 13 of 16

The root anastomosis means "outlet." Coronary anastomoses are interconnections between coronary arteries that ensure:

A. Blood is directed only through one pathway at a time
B. Alternate pathways exist for the blood supply to reach cardiac muscle
C. The coronary sinus drains into the left atrium
D. Ventricular pressures remain stable
E. The SA node receives a dedicated blood supply

Question 14 of 16

The root -gram means "record." An electrocardiogram (ECG) is a recording of:

Question 15 of 16

The prefix tri- means "three." The tricuspid valve is named for having three:

Question 16 of 16

The root cuspis means "point." The cusps of AV valves are flaps of fibrous tissue that:

A. Generate action potentials in the nodal cells
B. Provide structural support to the myocardium
C. Store calcium ions during diastole
D. Ensure one-way blood flow from atria into ventricles
E. Connect the AV node to the bundle branches

OBJ 2684 — Location and General Features of the Heart

Identify the location and general features of the heart.

Question 1 of 8

The heart lies near the anterior chest wall, directly behind which bony structure?

Question 2 of 8

The heart is enclosed by which connective tissue mass located between the two pleural cavities?

A. Pleura
B. Peritoneum
C. Mediastinum
D. Pericardium
E. Diaphragm

Question 3 of 8

Because the heart is rotated slightly toward the left, the anterior surface of the heart is primarily composed of which two chambers?

A. Left atrium and left ventricle
B. Right atrium and right ventricle
C. Left atrium and right ventricle
D. Right atrium and left ventricle
E. Both atria only

Question 4 of 8

The deep groove that marks the boundary between the atria and the ventricles on the external surface of the heart is the:

Question 5 of 8

The great vessels connect to the heart at the superior end called the base. The inferior, pointed tip is called the:

Question 6 of 8

When an atrium is not filled with blood, its outer portion deflates into a lumpy, wrinkled flap. This structure is called the:

A. Sulcus
B. Trabeculae carneae
C. Fossa ovalis
D. Auricle
E. Cusp

Question 7 of 8

Which of the following structures or tissues are found in the mediastinum? Select all that apply.

A. Heart

B. Great vessels

C. Trachea

D. Thymus

E. Stomach

Question 8 of 8

The heart beats approximately 100,000 times per day and pumps roughly how many liters of blood?

A. 800 liters
B. 1,000 liters
C. 8,000 liters
D. 80 liters
E. 500 liters

OBJ 2685 — Layers of the Heart Wall

Identify the three layers of the heart wall and their characteristics.

Question 1 of 8

From outer to inner, the three layers of the heart wall are:

A. Epicardium → myocardium → endocardium
B. Endocardium → myocardium → epicardium
C. Myocardium → epicardium → endocardium
D. Pericardium → epicardium → myocardium
E. Epicardium → endocardium → myocardium

Question 2 of 8

The epicardium is also known by which other name?

Question 3 of 8

The myocardium is the muscular wall of the heart. Its cardiac muscle tissue forms bands that wrap around the atria and spiral into the walls of the ventricles. This arrangement results in which type of contractions?

A. Slow, weak contractions that preserve myocardial oxygen
B. Tetanic contractions that maximize stroke volume
C. Squeezing and twisting contractions that increase pumping efficiency
D. Isometric contractions that do not change chamber volume
E. Peristaltic contractions directed toward the apex

Question 4 of 8

The inner surface of the heart — including the heart valves — is lined by a simple squamous epithelium called the:

Question 5 of 8

At intercalated discs, cardiac muscle cells are held together by desmosomes and linked by gap junctions. What specific function do the gap junctions serve?

A. Convey the mechanical force of contraction from cell to cell
B. Anchor the cell to the extracellular matrix
C. Store calcium ions between contractions
D. Allow ions and small molecules to pass between cells so action potentials travel rapidly from cell to cell
E. Regulate ATP production in the mitochondria

Question 6 of 8

The connective tissues of the heart serve three functions. Which of the following are correct? Select all that apply.

A. Support cardiac muscle fibers, blood vessels, and nerves of the myocardium

B. Add strength and prevent overexpansion of the heart

C. Help the heart return to normal shape after contractions

D. Generate the electrical impulse that initiates each heartbeat

E. Produce pericardial fluid to lubricate the heart surface

Question 7 of 8

The pericardial sac is made of a dense network of collagen fibers. What is the function of this sac?

A. It generates the force that initiates atrial contraction
B. It stabilizes the positions of the pericardium, heart, and associated vessels in the mediastinum
C. It insulates the atria from the ventricles electrically
D. It is the site of coronary artery origin
E. It stores oxygenated blood between beats

Question 8 of 8

Cardiac muscle cells are almost totally dependent on aerobic metabolism. Which two energy reserves do they store to support this metabolic demand?

A. Glycogen

B. Lipids

C. Creatine phosphate

D. Lactic acid

E. ATP synthase

OBJ 2686 — Blood Flow Through the Heart

Trace blood flow through the heart: major vessels, chambers, and valves.

Question 1 of 10

Blood returning from the systemic circuit enters the right atrium through which vessels? Select all that apply.

A. Superior vena cava

B. Inferior vena cava

C. Coronary sinus

D. Pulmonary veins

E. Aorta

Question 2 of 10

Blood flows from the right atrium into the right ventricle through the right AV valve. This valve is also called the:

Question 3 of 10

Blood leaving the right ventricle enters the pulmonary circuit. Which valve guards the entrance to the pulmonary trunk?

A. Aortic semilunar valve
B. Tricuspid valve
C. Pulmonary semilunar valve
D. Mitral valve
E. Bicuspid valve

Question 4 of 10

After gas exchange in the lungs, oxygenated blood returns to the heart through the pulmonary veins and enters the:

A. Right atrium
B. Right ventricle
C. Left atrium
D. Left ventricle
E. Coronary sinus

Question 5 of 10

Blood moves from the left atrium into the left ventricle through the left AV valve. This valve has two cusps and is also called the bicuspid valve or:

Question 6 of 10

Blood leaving the left ventricle passes through the aortic semilunar valve and enters the systemic circuit via the:

Question 7 of 10

The wall of the left ventricle must generate four to six times more pressure than the right ventricle. Why?

A. It receives more blood per beat than the right ventricle
B. It supplies the pulmonary circuit, which is longer
C. It has a thinner wall that must compensate with higher pressure
D. It must push blood around the entire systemic circuit, which is far more resistant than the pulmonary circuit
E. It contains more myoglobin and therefore contracts more forcefully

Question 8 of 10

The chordae tendineae and papillary muscles prevent the AV valve cusps from swinging into the atrium during ventricular contraction. If papillary muscles fail to contract, what happens?

A. The semilunar valves will also fail to open
B. Blood regurgitates back into the atrium because the cusps are not held in place
C. The right ventricle compensates by increasing stroke volume
D. Blood flow into the pulmonary trunk increases
E. The fossa ovalis reopens to equalize pressures

Question 9 of 10

The semilunar valves do not require muscular bracing like the AV valves. When the semilunar valves close, their three cusps support each other to prevent backflow. They support each other like:

A. A drawbridge
B. A lever arm
C. The legs of a tripod
D. A pair of hinges
E. A bellows

Question 10 of 10

The cardiac skeleton physically isolates the atrial muscle tissue from the ventricular muscle tissue. Why is this isolation clinically important?

A. It prevents the coronary arteries from receiving excessive blood flow
B. It ensures the semilunar valves do not open during diastole
C. It allows the myocardium to function without autonomic input
D. It allows the timing of ventricular contraction relative to atrial contraction to be precisely controlled through the AV node
E. It prevents pericardial fluid from entering the chambers

OBJ 2687 — Action Potentials: Skeletal vs. Cardiac Muscle

Identify the differences in action potentials and twitch contractions between skeletal and cardiac muscle.

Question 1 of 8

Step 1 of a cardiac action potential is rapid depolarization. What ion and what type of channel cause this?

A. Sodium ions enter through voltage-gated sodium channels
B. Calcium ions enter through voltage-gated calcium channels
C. Potassium ions exit through leak channels
D. Chloride ions enter through ligand-gated channels
E. Sodium ions exit through ATP-dependent pumps

Question 2 of 8

During the plateau phase of the cardiac action potential, voltage-gated calcium channels open and extracellular calcium enters. The plateau serves two purposes — what are they?

A. Delays repolarization by maintaining transmembrane potential near 0 mV

B. Initiates contraction by raising intracellular calcium

C. Opens the AV node to allow signal transmission

D. Closes the pulmonary semilunar valve

E. Activates the sodium-potassium pump

Question 3 of 8

Repolarization in a cardiac muscle cell is caused by which ion movement?

A. Calcium ions re-entering the cell
B. Sodium ions exiting through voltage-gated channels
C. Potassium ions rushing out of the cell as calcium channels close
D. Chloride ions entering the cell
E. ATP hydrolysis driving potassium inward

Question 4 of 8

A skeletal muscle action potential lasts approximately 10 milliseconds. How long does the cardiac muscle cell action potential last?

A. 10–20 milliseconds
B. 50–75 milliseconds
C. 100–150 milliseconds
D. 250–300 milliseconds
E. 500–600 milliseconds

Question 5 of 8

In skeletal muscle, twitches can stack on top of each other until tension reaches a sustained peak called tetanus. Why can tetanus NOT occur in cardiac muscle?

A. Cardiac muscle has no troponin and cannot bind calcium
B. Cardiac muscle receives too little neural stimulation
C. The refractory period of cardiac muscle lasts until relaxation is already underway, so twitches cannot summate
D. Cardiac sarcomeres are too short to support sustained contraction
E. The sarcoplasmic reticulum reclaims calcium too quickly

Question 6 of 8

Due to its long refractory period, a normal cardiac muscle cell is limited to a maximum contraction rate of approximately:

A. 60 contractions per minute
B. 100 contractions per minute
C. 200 contractions per minute
D. 300 contractions per minute
E. 400 contractions per minute

Question 7 of 8

In a cardiac muscle cell, extracellular calcium that enters during the plateau phase triggers an additional release of calcium from which intracellular structure?

Question 8 of 8

A patient is given a calcium channel blocker that prevents extracellular calcium from entering cardiac muscle cells. Based on how the cardiac action potential works, which phase would be most directly eliminated or shortened?

A. Rapid depolarization — sodium influx would stop
B. Repolarization — potassium efflux would be blocked
C. The plateau — calcium entry that maintains near-zero transmembrane potential would be blocked, shortening or eliminating the plateau and reducing contraction force
D. The resting potential — the cell would remain permanently depolarized
E. Automaticity — the SA node would stop firing

OBJ 2688 — The Conducting System of the Heart

Identify the components and functions of the cardiac conducting system.

Question 1 of 9

The property that allows cardiac muscle tissue to contract on its own without neural or hormonal stimulation is called:

Question 2 of 9

The normal cardiac pacemaker is located in the sinoatrial (SA) node. Where exactly in the heart is the SA node found?

A. In the interventricular septum near the apex
B. In the posterior wall of the right atrium near the entrance of the superior vena cava
C. In the floor of the left atrium near the pulmonary veins
D. In the AV bundle between the two ventricles
E. Along the inner wall of the left ventricle near the Purkinje fibers

Question 3 of 9

SA node pacemaker cells normally generate 70–80 action potentials per minute. If the SA node fails and the AV node takes over as the backup pacemaker, what heart rate would result?

A. 70–80 bpm — same as the SA node
B. 40–60 bpm — the AV node depolarizes more slowly
C. 100–120 bpm — the AV node fires faster without SA inhibition
D. 0 bpm — the heart cannot function without SA node input
E. 200 bpm — the ventricular cells take over and fire at maximum rate

Question 4 of 9

Trace the correct sequence of the conducting system from the SA node to the ventricular myocardium.

A. SA node → AV node → AV bundle → bundle branches → Purkinje fibers
B. SA node → bundle branches → AV node → Purkinje fibers → AV bundle
C. AV node → SA node → AV bundle → Purkinje fibers → bundle branches
D. SA node → Purkinje fibers → AV node → bundle branches → AV bundle
E. SA node → AV bundle → AV node → bundle branches → Purkinje fibers

Question 5 of 9

There is a 100-millisecond delay at the AV node before the impulse continues to the AV bundle. What is the clinical importance of this delay?

A. It allows the Purkinje fibers time to reset their refractory period
B. It prevents the SA node from sending a second impulse
C. It ensures the atria contract and blood moves into the ventricles before the ventricles are stimulated to contract
D. It generates the QRS complex on the electrocardiogram
E. It allows coronary artery filling to occur before systole

Question 6 of 9

The AV bundle is also known as the:

Question 7 of 9

An abnormal conducting cell or ventricular muscle cell that generates action potentials rapidly enough to override the SA or AV node is called an:

Question 8 of 9

On the electrocardiogram, the P wave represents atrial depolarization. The QRS complex represents ventricular depolarization. The T wave represents:

A. Atrial repolarization
B. Ventricular depolarization
C. AV node delay
D. Ventricular repolarization
E. Purkinje fiber activation

Question 9 of 9

Extending the P–R interval on an ECG to more than 200 milliseconds is clinically significant because it can indicate:

A. Decreased ventricular mass
B. Ventricular hypertrophy
C. Atrial repolarization occurring simultaneously with depolarization
D. Damage to the conducting pathways or AV node
E. SA node firing at an abnormally fast rate

OBJ 2689 — The Cardiac Cycle and Heart Sounds

Communicate the events of the cardiac cycle and relate heart sounds to specific events.

Question 1 of 8

The cardiac cycle begins with atrial systole. At the start of a cycle, the atria are filled with blood and the ventricles are partially filled. What does atrial systole accomplish?

A. It closes the AV valves to prevent backflow
B. It opens the semilunar valves to eject blood into the arterial trunks
C. It contracts the atria to completely fill the ventricles with blood
D. It repolarizes the ventricular myocardium
E. It generates the P wave on the ECG during the same event as valve closure

Question 2 of 8

As ventricular systole begins, rising ventricular pressure closes the AV valves. But blood cannot yet enter the arterial trunks. What must happen before the semilunar valves open?

A. The atria must complete their repolarization
B. The papillary muscles must fully relax
C. The pericardial fluid pressure must equalize
D. Ventricular pressure must rise above the pressure already in the arterial trunks
E. The coronary sinus must drain completely

Question 3 of 8

Ventricular systole in a resting adult lasts approximately how long?

A. 100 milliseconds
B. 175 milliseconds
C. 270 milliseconds
D. 400 milliseconds
E. 800 milliseconds

Question 4 of 8

When ventricular diastole begins, ventricular pressure falls below arterial pressure. This closes the semilunar valves. When ventricular pressure falls below atrial pressure, which valves open?

Question 5 of 8

By the time the next atrial systole begins, the ventricles are roughly what percentage filled with blood?

A. 30 percent
B. 50 percent
C. 70 percent
D. 90 percent
E. 100 percent

Question 6 of 8

The first heart sound ("lubb") is produced by which specific event?

A. The semilunar valves closing at the start of diastole
B. The AV valves closing and the semilunar valves opening at the start of ventricular systole
C. Blood flowing from the atria into the relaxed ventricles
D. Atrial contraction pushing blood into the ventricles
E. The Purkinje fibers depolarizing the ventricular myocardium

Question 7 of 8

The second heart sound ("dupp") occurs at the beginning of ventricular diastole. What causes it?

A. The AV valves opening
B. The AV valves closing
C. Atrial systole beginning
D. The semilunar valves closing
E. Blood entering the coronary arteries

Question 8 of 8

During ventricular diastole — late phase — all four chambers are relaxed and the ventricles fill passively. If the atria were so severely damaged they could no longer function, would the person survive? Why?

A. Yes — because the ventricles are already 70% filled passively before atrial systole contributes, so atrial contraction makes a relatively minor contribution to ventricular volume
B. No — because ventricular filling depends entirely on atrial contraction to push blood across the AV valves
C. No — because the SA node is located in the right atrium and would stop the entire conducting system
D. Yes — because the semilunar valves can redirect blood flow around the non-functional atria
E. Only if ventricular systole is also reduced proportionally

OBJ 2690 — Stroke Volume and Cardiac Output

Define stroke volume and cardiac output and identify the factors that influence these values.

Question 1 of 8

The formula for cardiac output is CO = HR × SV. If heart rate is 75 bpm and stroke volume is 80 mL per beat, what is the cardiac output?

A. 750 mL/min
B. 3,000 mL/min
C. 5,000 mL/min
D. 6,000 mL/min
E. 9,000 mL/min

Question 2 of 8

The Frank–Starling principle states that the greater the volume of blood entering the ventricles (stretching the myocardium), the more powerful the contraction and the greater the stroke volume. This is summarized as:

A. More resistance = more output
B. Faster rate = lower volume
C. Less stretch = greater force
D. More in = more out
E. Higher rate = higher stroke volume

Question 3 of 8

The atrial reflex (Bainbridge reflex) adjusts heart rate in response to increased venous return. What is the mechanism?

A. Blood entering the right atrium activates parasympathetic fibers, slowing the SA node
B. Blood entering the right atrium stretches stretch receptors in the atrial walls, triggering increased sympathetic activity, which causes the SA node to depolarize faster and raises heart rate
C. Blood entering the left ventricle stimulates baroreceptors to inhibit the cardioacceleratory center
D. Stretch of the ventricular wall directly opens voltage-gated sodium channels in the SA node
E. Venous pressure directly pushes on the AV node to increase its firing rate

Question 4 of 8

Norepinephrine released by sympathetic neurons increases stroke volume. Acetylcholine released by parasympathetic neurons decreases it. What is the primary site of the greatest reduction in contractile force from parasympathetic stimulation?

A. The left ventricle, which has the densest parasympathetic innervation
B. The right ventricle
C. The atria, because parasympathetic innervation of the ventricles is relatively limited
D. The Purkinje fibers
E. The coronary arteries

Question 5 of 8

Which hormones increase both heart rate AND force of contraction? Select all that apply.

A. Epinephrine

B. Norepinephrine (from adrenal medullae)

C. Thyroid hormones

D. Glucagon

E. Acetylcholine

Question 6 of 8

Hypercalcemia (elevated extracellular calcium) causes cardiac muscle contractions to become extremely excitable, powerful, and prolonged. In extreme cases, the heart can go into extended contraction. What is this fatal condition called?

A. Cardiac tamponade
B. Ventricular fibrillation
C. Bradycardia
D. Extended state of contraction (tetany of the heart)
E. Heart block

Question 7 of 8

Why is a very rapid heart rate potentially dangerous even though it increases rate?

A. As heart rate rises, ventricular filling time (diastole) shortens, so the ventricles do not fill adequately and stroke volume falls, reducing actual cardiac output
B. A fast rate blocks norepinephrine receptors in the SA node
C. A fast rate causes the cardiac skeleton to stiffen and reduce valve function
D. A fast rate causes hypercalcemia in the sarcoplasmic reticulum
E. A fast rate activates the cardioinhibitory center to send inhibitory signals

Question 8 of 8

The cardiac centers in which brainstem structure contain both the cardioacceleratory center (sympathetic) and the cardioinhibitory center (parasympathetic)?

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Ch. 11 — Blood

Medical Vocabulary — Blood (Ch. 11)

Define the medical vocabulary components related to the cardiovascular system: blood.

Root / Term	Meaning	Clinical Example
agglutinins	gluing	agglutinization (RBC clumping in transfusion reaction)
embolos	plug	embolus (drifting clot blocking a vessel)
erythros	red	erythrocyte (red blood cell)
haima	blood	hemostasis (halting blood loss)
hypo- / oxy-	below / presence of oxygen	hypoxia (low tissue oxygen levels)
karyon	nucleus	megakaryocyte (giant nucleus cell → platelets)
leukos	white	leukocyte (white blood cell)
megas	big	megakaryocyte
myelos	marrow	myeloid tissue (red bone marrow)
-osis	condition / increase	leukocytosis (excess WBCs)
penia	poverty / deficiency	leukopenia (too few WBCs)
poiesis	making	hemopoiesis (blood cell production)
punctura	a piercing	venipuncture (blood draw from vein)
stasis	halt	hemostasis (stopping bleeding)
thrombos	clot	thrombocyte (platelet)
vena	vein	venipuncture

Components and Major Functions of Blood

Identify the important components and major functions of blood.

Blood is a specialized fluid connective tissue — cells suspended in a fluid matrix called plasma. Whole blood = plasma + formed elements.

Component	Approximate % of Whole Blood
Plasma	~55%
Formed elements (RBCs, WBCs, platelets)	~45%

Transport — dissolved gases (O₂, CO₂), nutrients, hormones, and metabolic wastes
Regulate pH and ion composition — diffusion between blood and interstitial fluid eliminates local ion imbalances; blood absorbs and neutralizes acids such as lactic acid
Restrict fluid losses — clotting enzymes and factors respond to vessel damage and initiate blood clotting
Defend against toxins and pathogens — transports WBCs, delivers antibodies to infection sites
Stabilize body temperature — absorbs heat from active skeletal muscles; redirects warm blood to or away from skin surface

Property	Value
Temperature	~38°C (100.4°F) — slightly above body temperature
Viscosity	5× that of water — from dissolved proteins and formed elements
pH	7.35–7.45 (slightly alkaline)
Adult volume	Males: 5–6 L \| Females: 4–5 L

Blood Collection — Venipuncture

Fresh blood is most commonly drawn from the median cubital vein (anterior elbow surface). Superficial veins are easy to locate, vein walls are thin, and low venous pressure means the puncture seals quickly.

Plasma — Composition and Functions

Communicate the composition and functions of plasma.

Plasma makes up ~55% of whole blood volume. It is ~92% water. The remaining 8% includes plasma proteins, electrolytes, organic nutrients, and organic wastes.

Protein	% of Plasma Proteins	Function
Albumins	~60%	Major contributors to plasma osmotic pressure; bind and transport lipids
Globulins	~35%	Antibodies (immunoglobulins) attack pathogens; transport globulins bind ions, hormones, small molecules; lipoproteins transport insoluble lipids
Fibrinogen	~4%	Blood clotting — converts to insoluble fibrin strands that form the clot framework

The liver synthesizes more than 90% of all plasma proteins, including all albumins, all fibrinogen, and most globulins. Antibodies (immunoglobulins) are produced by plasma cells of the lymphatic system.

Electrolytes — Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, HCO₃⁻, HPO₄²⁻, SO₄²⁻; essential for vital cellular activities
Organic nutrients — glucose, amino acids, fatty acids, cholesterol, vitamins; used for ATP production, growth, and maintenance
Organic wastes — urea, uric acid, creatinine, bilirubin, ammonium ions; carried to sites of breakdown or excretion

Plasma vs. Serum

When fibrinogen and other clotting proteins are removed from plasma (as happens when a blood sample clots), the remaining fluid is called serum. Serum has the same composition as plasma minus the clotting proteins.

Origin and Production of Formed Elements (Hemopoiesis)

Communicate the origin and production of the formed elements in blood.

Hemopoiesis is the process by which all formed elements are produced. In adults, it occurs exclusively in red bone marrow (myeloid tissue) located in the vertebrae, sternum, ribs, scapulae, pelvis, and proximal limb bones.

All formed elements arise from divisions of hemocytoblasts — multipotent stem cells present in red bone marrow.

Stem Cell Line	Formed Elements Produced
Myeloid stem cells	Red blood cells, platelets, neutrophils, eosinophils, basophils, monocytes
Lymphoid stem cells	Lymphocytes (migrate to thymus, spleen, lymph nodes for development)

Colony-stimulating factors (CSFs) — hormones that regulate production of WBCs other than lymphocytes; four CSFs identified, each targeting specific stem cell lines
Erythropoietin (EPO) — released by the kidneys when tissue oxygen (O₂) is low; stimulates RBC production specifically
Thymosins — from the thymus gland; promote differentiation of T-cell lymphocytes in immature individuals

Yellow Bone Marrow Reserve

Areas not producing blood cells contain yellow bone marrow (fatty tissue). Under extreme stimulation — severe sustained blood loss — yellow marrow can convert to red marrow to increase RBC formation rate.

Red Blood Cells — Characteristics and Functions

Communicate the characteristics and functions of red blood cells, hemoglobin structure and function, RBC recycling, and erythropoiesis.

Biconcave disc — large surface area to volume ratio maximizes diffusion rate between cytoplasm and surrounding plasma; enables flexing through narrow capillaries
No nucleus, no ribosomes, no mitochondria after maturation — cannot divide or synthesize proteins
Obtain energy by anaerobic metabolism only — ensures O₂ carried to peripheral tissues is not "stolen" by the RBC's own mitochondria
Life span: ~120 days; ~1% replaced daily; ~3 million new RBCs enter circulation per second

The hematocrit is the percentage of whole blood volume occupied by formed elements (essentially RBCs). Normal values: males avg 46% (range 40–54), females avg 42% (range 37–47). Androgens stimulate RBC production; estrogens do not — explaining the sex difference.

Hemoglobin makes up >95% of RBC intracellular proteins. Each Hb molecule has 4 globular protein subunits, each containing one heme molecule with an iron ion (Fe²⁺) that reversibly binds one O₂ molecule.

Location	Hemoglobin State	Blood Color
Lungs (high O₂)	Oxyhemoglobin — all heme sites occupied by O₂	Bright red
Peripheral tissues (low O₂, high CO₂)	Deoxyhemoglobin — O₂ released; globin binds CO₂	Dark red / burgundy

Macrophages in liver, spleen, and bone marrow engulf old/damaged RBCs before they hemolyze (90% of RBCs); remaining 10% hemolyze in the bloodstream
Globin chains → broken into amino acids → metabolized by macrophage or recycled into bloodstream
Heme → iron stripped out → heme ring converted to biliverdin (green pigment) → then to bilirubin (orange-yellow pigment) → released into bloodstream → bound to albumin → liver → excreted in bile → large intestine → bacteria convert to urobilins/stercobilins (color of feces and urine)
Iron (Fe²⁺) → stored in macrophage OR released into bloodstream bound to transferrin (plasma transport protein) → developing RBCs in red bone marrow absorb iron and amino acids to synthesize new Hb

Clinical Link — Jaundice

If bile ducts are blocked (e.g., by gallstones), bilirubin diffuses into peripheral tissues, causing yellow coloration of the skin and eyes — jaundice.

RBC formation occurs only in red bone marrow. Developmental sequence: hemocytoblast → myeloid stem cell → proerythroblast → erythroblasts (actively synthesizing Hb) → erythroblast ejects nucleus → reticulocyte → enters bloodstream → matures into erythrocyte within 24 hours.

EPO regulation loop: tissue hypoxia → kidneys release EPO → EPO stimulates erythroblast division rate AND accelerates hemoglobin synthesis → more RBCs → improved O₂ delivery → hypoxia resolved.

Requirements for normal erythropoiesis: amino acids, iron, vitamin B₁₂ (requires intrinsic factor from stomach for absorption), vitamin B₆, folic acid. Deficiency of B₁₂ → pernicious anemia.

Blood Types — ABO and Rh Systems

Communicate the factors which determine a person's blood type and why blood types are important.

Blood type is determined by the presence or absence of specific surface antigens (agglutinogens) on RBC membranes. Genetic makeup determines which antigens appear. RBCs have at least 50 surface antigen types; three are clinically most important: A, B, and Rh (D).

Blood Type	Antigens on RBCs	Antibodies in Plasma	U.S. Prevalence (approx.)
A+	A only	Anti-B	34%
B+	B only	Anti-A	9%
AB+	A and B	Neither	3%
O+	Neither	Both anti-A and anti-B	38%

Rh positive (Rh+) = Rh antigen present on RBCs. Rh negative (Rh−) = absent. Anti-Rh antibodies do NOT normally exist in Rh− plasma — they only form after sensitization (exposure to Rh+ blood through transfusion or pregnancy).

When incompatible blood is transfused, antibodies in the recipient's plasma bind to antigens on donated RBCs → agglutination (clumping) → hemolysis → clumps and fragments plug small vessels in kidneys, lungs, heart, or brain → tissue damage or death.

In emergencies, Type O− blood is used as a universal donor because O− RBCs lack A, B, and Rh antigens — cannot trigger common cross-reactions.

Hemolytic Disease of the Newborn (HDN) — Erythroblastosis Fetalis

An Rh− mother carrying an Rh+ fetus: delivery exposes the mother to fetal Rh antigens → she produces anti-Rh antibodies. A second Rh+ pregnancy → massive anti-Rh antibody response → antibodies cross placenta → attack and hemolyze fetal RBCs → severe fetal anemia → immature RBCs (erythroblasts) flood circulation → erythroblastosis fetalis.

White Blood Cells — Types, Structures, Functions

Identify the various white blood cells on the basis of their structures and functions.

WBCs (leukocytes) are larger than RBCs, have a nucleus, and lack hemoglobin. All WBCs share four functional characteristics: amoeboid movement (gliding through tissues), diapedesis (squeezing through capillary walls), positive chemotaxis (attracted to chemical signals from pathogens/damaged tissue), and most are phagocytic.

Normal WBC count: 6,000–9,000/μL. Circulating WBCs represent a small fraction — most are in connective tissues and lymphatic organs.

Cell	% of WBCs	Nucleus	Granules	Function
Neutrophils	50–70%	2–5 lobes ("beads on a string")	Neutral — don't stain strongly	First responders to infection; phagocytize bacteria; form pus; short life span ~10 hrs
Eosinophils	2–4%	2 lobes	Deep red (stain with eosin)	Attack antibody-coated targets; release cytotoxic enzymes + nitric oxide; numbers spike in parasitic infection and allergic reactions
Basophils	<1%	Bilobed (obscured)	Deep purple-blue (basic dyes)	Migrate to injury sites; release histamine (enhances inflammation) and heparin (prevents clotting); attract eosinophils and other basophils

Cell	% of WBCs	Nucleus	Function
Monocytes	2–8%	Large, kidney-bean or oval shaped	Largest WBC; circulate ~24 hrs then enter tissues to become free macrophages; aggressive phagocytes; release chemicals that attract other phagocytes and fibroblasts; fibroblasts produce scar tissue to wall off injured areas
Lymphocytes	20–40%	Large nucleus; thin cytoplasm halo	Specific defenses — some attack foreign/abnormal cells directly (T cells); others secrete antibodies (B cells/plasma cells); survive months to decades

Term	Meaning	Significance
Differential count	Number of each WBC type per 100 WBCs	Reveals infections, inflammation, allergies, cancer
Leukopenia	Reduced WBC numbers	Impaired immune defense
Leukocytosis	Excessive WBC numbers	Infection, inflammation; extreme (>100,000/μL) → leukemia

Hemostasis — Mechanisms Reducing Blood Loss

Communicate the mechanisms that reduce blood loss after an injury.

Hemostasis (haima = blood + stasis = halt) is the process that stops bleeding and prevents fluid loss through damaged vessel walls, while establishing a framework for tissue repair. It consists of three overlapping phases.

Vessel wall damage triggers contraction of smooth muscle in the vessel wall → vascular spasm → vessel diameter decreases → blood flow slows or stops. Endothelial cells at the injury site become "sticky" — in small capillaries, cells can adhere and block the opening completely.

Platelets attach to sticky endothelium and exposed collagen fibers of the damaged vessel → platelets aggregate and stick to each other → platelet plug forms. If damage is minor, the platelet plug alone may seal the break. Platelets are derived from megakaryocytes in red bone marrow and circulate for 9–12 days.

A cascade of clotting factor activations converts circulating fibrinogen into insoluble fibrin. Fibrin strands trap RBCs and platelets → blood clot seals the damaged vessel.

Pathway	Trigger	Speed	Role
Extrinsic pathway	Tissue factor released by damaged endothelium + Ca²⁺ + Factor VII	Fast (~15 sec)	Initiates clotting rapidly after injury
Intrinsic pathway	Proenzymes exposed to collagen at injury site + platelet factor	Slower	Reinforces and enlarges the clot
Common pathway	Both extrinsic and intrinsic pathways activate Factor X	—	Factor X → prothrombinase → prothrombin → thrombin → fibrinogen → fibrin

Both calcium ions and vitamin K are required throughout the clotting cascade. Vitamin K deficiency disables the common pathway. Roughly half of required vitamin K comes from diet; the rest is synthesized by intestinal bacteria.

Clot retraction — platelets contract after the fibrin network forms, pulling torn vessel edges closer together and reducing the area of damage.

Fibrinolysis — as tissue repairs proceed, thrombin and t-PA (tissue plasminogen activator, released by damaged tissue) activate plasminogen → plasmin → digests fibrin strands → clot dissolves.

Ch. 12 — The Heart

Medical Vocabulary — The Heart (Ch. 12)

Define the medical vocabulary components related to the cardiovascular system: the heart.

Root / Term	Meaning	Clinical Example
anastomosis	outlet / interconnection	anastomoses (interconnections between coronary arteries)
atrion	hall / entry chamber	atrium (entry chamber of heart)
auris	ear	auricle (ear-shaped atrial appendage)
bi-	two	bicuspid valve (two cusps — the mitral valve)
bradys	slow	bradycardia (heart rate <60 bpm)
cuspis	point	bicuspid / tricuspid valve (cusps = flaps)
diastole	expansion / relaxation	diastole (relaxation and filling phase)
-gram	record	electrocardiogram (ECG — record of cardiac electrical events)
luna	moon	semilunar valve (half-moon shaped cusps)
mitre	bishop's hat	mitral valve (left AV valve = bicuspid)
papilla	nipple-shaped elevation	papillary muscles (anchor chordae tendineae)
semi-	half	semilunar valve (pulmonary and aortic)
septum	wall / partition	interatrial septum, interventricular septum
systole	drawing together / contraction	systole (contraction phase of cardiac cycle)
tachys	swift	tachycardia (heart rate >100 bpm)
tri-	three	tricuspid valve (three cusps — right AV valve)
ventricle	little belly	ventricle (pumping chamber)

Heart Location and General Features

Identify the location and general features of the heart.

The heart lies in the mediastinum — the connective tissue mass between the two pleural cavities — directly behind the sternum on the anterior chest wall. It is roughly the size of a clenched fist (~12.5 cm base to apex) and sits at an angle rotated left, so the anterior surface is primarily right atrium and right ventricle.

The heart is surrounded by the pericardial cavity, lined by the pericardium — a serous membrane with two layers:

Visceral pericardium (epicardium) — covers the outer heart surface
Parietal pericardium — lines the inner surface of the pericardial sac surrounding the heart

Pericardial fluid between these layers acts as a lubricant, reducing friction as the heart beats.

Landmark	Location / Significance
Base	Superior — where great vessels attach
Apex	Inferior pointed tip
Coronary sulcus	Deep groove (filled with fat) marking atria–ventricle boundary; contains coronary arteries and veins
Anterior interventricular sulcus	Marks boundary between left and right ventricles (anterior surface)
Posterior interventricular sulcus	Marks boundary between left and right ventricles (posterior surface)
Auricles	Wrinkled flap-like appendages on atria when not fully filled with blood

Right atrium → right ventricle (pulmonary circuit) | Left atrium → left ventricle (systemic circuit). Atria and ventricles are separated internally by the interatrial septum and interventricular septum respectively.

The left and right coronary arteries originate at the aortic sinuses at the base of the aorta — the highest pressure point in the systemic circuit, ensuring constant flow to active cardiac muscle. Arterial anastomoses (interconnections) between coronary branches provide alternate flow paths if one branch is compromised. Venous drainage → great and middle cardiac veins → coronary sinus → right atrium.

Layers of the Heart Wall

Identify the layers of the heart wall.

Layer	Tissue Composition	Notes
Epicardium (visceral pericardium)	Exposed epithelium + underlying areolar tissue	Covers outer heart surface; continuous with pericardial fluid-producing serous membrane
Myocardium	Cardiac muscle tissue + blood vessels + nerves	Thickest layer; muscle bands wrap around atria and spiral into ventricular walls — creates squeezing/twisting contraction for efficient pumping
Endocardium	Simple squamous epithelium (endothelium) + areolar tissue	Lines all inner surfaces including valve surfaces; continuous with the endothelium of attached great vessels

Smaller than skeletal muscle fibers; single centrally located nucleus
Abundant mitochondria and myoglobin — almost totally dependent on aerobic metabolism
Energy reserves stored as glycogen and lipids
Connected at intercalated discs:
- Desmosomes — interlock membranes; transmit contractile force cell-to-cell
- Gap junctions — allow ion and small molecule movement; enable action potentials to spread rapidly from cell to cell

Dense bands of tough elastic connective tissue encircle the bases of the pulmonary trunk, aorta, and all four heart valves. Functions: stabilizes valve positions; provides structural support; electrically isolates atrial muscle from ventricular muscle — critical because it means the timing of ventricular contraction relative to atrial contraction can be precisely controlled through the AV node.

Blood Flow Through the Heart

Communicate the flow of blood through the heart, identifying the major blood vessels, chambers, and heart valves.

Superior vena cava, inferior vena cava, coronary sinus → deliver deoxygenated systemic blood to the right atrium
Right atrium → through the tricuspid valve (right AV valve) — 3 fibrous cusps braced by chordae tendineae and papillary muscles → right ventricle
Right ventricle contracts → through the pulmonary semilunar valve → pulmonary trunk → left and right pulmonary arteries → lungs (gas exchange)
Pulmonary veins (2 from each lung; 4 total) → deliver oxygenated blood to left atrium
Left atrium → through the bicuspid valve (mitral / left AV valve) — 2 cusps, also braced by chordae tendineae and papillary muscles → left ventricle
Left ventricle contracts → through the aortic semilunar valve → ascending aorta → systemic circuit

Valve Type	Location	Open When	Closed When
AV valves (tricuspid + bicuspid/mitral)	Between atria and ventricles	Ventricles relaxed (diastole) — blood flows atria → ventricles	Ventricles contract (systole) — chordae tendineae + papillary muscles prevent inversion into atria
Semilunar valves (pulmonary + aortic)	Between ventricles and great vessels	Ventricular pressure exceeds arterial pressure	Ventricular pressure falls — 3 symmetric cusps support each other like tripod legs, preventing backflow

The left ventricle has a massively thick muscular wall and is round in cross-section — it must generate 4–6× more pressure than the right ventricle to push blood around the entire systemic circuit. The right ventricle has a thin wall and acts like a bellows pump — it only needs to push blood to the nearby lungs through the low-resistance pulmonary circuit. Both ventricles eject equal volumes of blood per beat.

Action Potentials — Skeletal vs. Cardiac Muscle

Identify the differences in the action potentials and twitch contractions of skeletal muscle fibers and cardiac muscle cells.

Feature	Skeletal Muscle Fiber	Cardiac Muscle Cell
Action potential duration	~10 msec	250–300 msec (25–30× longer)
Plateau phase	Absent — rapid repolarization follows depolarization	Present — Ca²⁺ entry delays repolarization for ~175 msec
Ca²⁺ source for contraction	Sarcoplasmic reticulum (SR) only	SR + extracellular Ca²⁺ (enters through voltage-gated Ca²⁺ channels during plateau)
Refractory period	Short — ends before peak twitch tension	Long — continues until relaxation begins
Tetanus possible?	Yes — twitches summate at high stimulation rates	No — refractory period prevents summation; a heart in tetany cannot pump blood
Maximum contraction rate	~500+/min	~200/min

Rapid Depolarization — voltage-gated Na⁺ channels open → Na⁺ rushes in → membrane potential rises to ~+30 mV → Na⁺ channels close (duration: 3–5 msec)
Plateau — voltage-gated Ca²⁺ channels open → Ca²⁺ enters sarcoplasm → delays repolarization (entering positive charges balance K⁺ loss) → Ca²⁺ also triggers additional Ca²⁺ release from SR → sustained contraction (duration: ~175 msec)
Repolarization — Ca²⁺ channels close → K⁺ channels open → K⁺ exits → resting potential restored (duration: 75 msec)

Conducting System of the Heart

Identify the components and functions of the conducting system of the heart.

Cardiac muscle contracts on its own without neural or hormonal stimulation — a property called automaticity (autorhythmicity). The conducting system initiates and coordinates contractions so atria contract before ventricles, and ventricles contract in a wave from apex to base.

SA node (sinoatrial node) — "cardiac pacemaker"; embedded in posterior right atrial wall near the SVC; pacemaker cells depolarize spontaneously at 70–80 action potentials/min → sets intrinsic heart rate (Time = 0)
Internodal pathways — conducting cells in atrial walls spread impulse across both atria → atria contract together (Elapsed: 50 msec)
AV node (atrioventricular node) — floor of right atrium near coronary sinus opening; impulse slows here for a 100 msec delay — critical to allow atria to finish contracting and blood to enter ventricles before ventricular contraction begins. Backup pacemaker rate: 40–60 bpm if SA node fails (Elapsed: 150 msec)
AV bundle (Bundle of His) — only electrical connection between atria and ventricles (cardiac skeleton electrically isolates them everywhere else); travels down interventricular septum → divides into left and right bundle branches (Elapsed: 175 msec)
Purkinje fibers — distribute impulse to all ventricular myocardium; contraction begins at apex and spreads toward base → blood pushed up and out into great vessels (Elapsed: 225 msec)

ECG Feature	Electrical Event	Mechanical Result
P wave (small)	Atrial depolarization	Atria begin contracting ~100 msec after P wave start
QRS complex (large)	Ventricular depolarization (atrial repolarization masked here)	Ventricles begin contracting shortly after R wave peak
T wave (smaller)	Ventricular repolarization	Ventricles relax
P-R interval >200 msec	Prolonged AV node conduction	Indicates AV node or conduction pathway damage
Q-T interval	One complete ventricular depolarization + repolarization cycle	Prolonged Q-T = electrolyte disturbance, ischemia, congenital defect risk

Ectopic Pacemakers

If an abnormal conducting cell generates action potentials faster than the SA node, it can override normal pacing and disrupt the coordinated sequence — an ectopic pacemaker. Identified by ECG analysis.

The Cardiac Cycle and Heart Sounds

Communicate the events of the cardiac cycle and relate heart sounds to specific events in the cycle.

Cardiac cycle = the period from the start of one heartbeat to the start of the next. At 75 bpm, each cycle lasts ~800 msec. Systole = contraction; diastole = relaxation. Fluid moves from higher pressure to lower pressure — valves ensure one-way flow.

Phase	Timing	Events	Valve Status
Atrial systole	0–100 msec	Atria contract; force remaining blood into ventricles (ventricles already ~70% filled passively)	AV valves open; semilunar valves closed
Ventricular systole — phase 1	100–150 msec	Ventricular contraction begins; pressure rises → AV valves close; not yet enough pressure to open semilunar valves	AV valves closed; semilunar valves still closed
Ventricular systole — phase 2	150–370 msec	Ventricular pressure exceeds arterial pressure → semilunar valves open; blood ejected into aorta and pulmonary trunk	AV valves closed; semilunar valves open
Ventricular diastole — early	370 msec+	Ventricles relax; pressure drops below arterial pressure → semilunar valves close; blood flows into relaxed atria	All valves briefly closed; then AV valves open as ventricular pressure drops below atrial pressure
Ventricular diastole — late	Until next cycle	All chambers relaxed; ventricles fill passively from atria (~70% of filling occurs here before next atrial systole)	AV valves open; semilunar valves closed

Sound	Cause	Marks
S1 — "lubb"	AV valves closing + semilunar valves opening	Start of ventricular systole; longer than S2
S2 — "dupp"	Semilunar valves closing	Start of ventricular diastole
S3 and S4 (faint)	Blood flowing into ventricles and atrial contraction	Usually not heard in healthy adults; not associated with valve closure

Stroke Volume and Cardiac Output

Communicate the definition of stroke volume and cardiac output, and the factors that influence these values.

Stroke volume (SV) = the amount of blood ejected by one ventricle per heartbeat.

Cardiac output (CO) = the amount of blood pumped by the left ventricle per minute.

CO (mL/min) = Heart Rate (beats/min) × Stroke Volume (mL/beat)

Example: 75 bpm × 80 mL/beat = 6,000 mL/min (6 L/min) — approximately the total adult blood volume circulated each minute at rest. Maximum CO can reach 30 L/min when both HR and SV increase together (500–700% increase possible).

Frank-Starling principle: the greater the venous return → more ventricular stretch → more powerful contraction → greater SV. "More in = more out." Balances output between left and right ventricles under varying conditions.

Atrial (Bainbridge) reflex: increased venous return stretches the right atrial wall → stretch receptors → sympathetic → SA node depolarizes faster → HR increases.

Division	Neurotransmitter	Effect on HR	Effect on SV (contractility)
Sympathetic	NE (+ adrenal E/NE)	Increases (faster SA node depolarization)	Increases (stronger ventricular contraction)
Parasympathetic	ACh (vagus nerve)	Decreases	Decreases (mainly atrial; limited ventricular innervation)

Both divisions are tonically active — cutting the vagus nerve increases HR; sympathetic blockers slow it. The cardioacceleratory center (medulla) governs sympathetic; the cardioinhibitory center (medulla) governs parasympathetic.

Epinephrine + norepinephrine (adrenal medullae) — increase both HR and contractile force
Thyroid hormones + glucagon — increase contractile force

Condition	Effect
Hypercalcemia (↑ Ca²⁺)	Prolonged powerful contractions; extreme cases → fatal sustained contraction
Hypocalcemia (↓ Ca²⁺)	Weak contractions; may cease altogether
Hyperkalemia (↑ K⁺)	Weak, irregular contractions (alters SA node resting potential)
Hypokalemia (↓ K⁺)	Reduced heart rate
↑ Body temperature	Increases HR and contractile force (fever makes heart "race")
↓ Body temperature	Slows SA node depolarization; reduces HR and contractility

Medical Vocabulary

Components & Functions of Blood

Plasma Composition & Function

Origin of Formed Elements

Red Blood Cells

Blood Types

White Blood Cells

Hemostasis & Blood Loss Control

OBJ 2683 — Medical Vocabulary: The Cardiovascular System / Heart

OBJ 2684 — Location and General Features of the Heart

OBJ 2685 — Layers of the Heart Wall

OBJ 2686 — Blood Flow Through the Heart

OBJ 2687 — Action Potentials: Skeletal vs. Cardiac Muscle

OBJ 2688 — The Conducting System of the Heart

OBJ 2689 — The Cardiac Cycle and Heart Sounds

OBJ 2690 — Stroke Volume and Cardiac Output

★ Final Score — SOMAPL1C: The Heart

Medical Vocabulary — Blood (Ch. 11)

Components and Major Functions of Blood

Plasma — Composition and Functions

Origin and Production of Formed Elements (Hemopoiesis)

Red Blood Cells — Characteristics and Functions

Blood Types — ABO and Rh Systems

White Blood Cells — Types, Structures, Functions

Hemostasis — Mechanisms Reducing Blood Loss

Medical Vocabulary — The Heart (Ch. 12)

Heart Location and General Features

Layers of the Heart Wall

Blood Flow Through the Heart

Action Potentials — Skeletal vs. Cardiac Muscle

Conducting System of the Heart

The Cardiac Cycle and Heart Sounds

Stroke Volume and Cardiac Output