A+P L Midterm Pt 3 Flashcards
Outline the five steps required for hemostasis following damage to a blood vessel.
1.Vasoconstriction
What happens: The blood vessels constrict (narrow) to reduce blood flow and limit blood loss.
Why it matters: This helps minimize the amount of blood that escapes the body at
the site of injury.
- Platelet Plug Formation
What happens: Platelets (small blood cells) are attracted to the site of injury. They become sticky and clump together to form a temporary “platelet plug” that covers the wound.
Why it matters: This plug helps block further blood flow and provides a foundation for the next steps in clot formation. - Coagulation (Clotting)
What happens: Coagulation factors (proteins in the blood) are activated, leading to the conversion of fibrinogen into fibrin. Fibrin strands form a mesh that solidifies the blood clot.
Why it matters: The fibrin mesh strengthens the platelet plug and forms a stable blood clot, effectively sealing the wound. - Clot Retraction
What happens: The clot contracts, which helps reduce the size of the wound and further seals the vessel.
Why it matters: Clot retraction helps stabilize the clot and promotes healing by reducing the space that needs to be repaired. - Fibrinolysis
What happens: After the vessel is sufficiently healed, the clot is dissolved by fibrinolysis. The clot is broken down by an enzyme called plasmin.
Why it matters: This step removes the clot once the blood vessel has healed and normal blood flow is restored.
Describe the contributions of the intrinsic and extrinsic pathways to the common pathway of coagulation.
Extrinsic Pathway: Activated by tissue damage, quickly activates Factor X to start clotting.
Intrinsic Pathway: Activated by blood vessel damage, amplifies the clotting process and generates more Factor Xa.
Both pathways lead to the common pathway, where Factor Xa activates thrombin, forming a stable blood clot.
Differentiate between a thrombus and an embolus. What are the potential clinical consequences of each?
Thrombus: A clot formed locally in a vessel that can block blood flow.
Consequences: Localized blockage, tissue damage (e.g., heart attack, DVT).
Embolus: A clot or foreign material that moves to another part of the body and causes blockage in smaller vessels.
Consequences: This can lead to pulmonary embolism, stroke, or organ damage.
Name the four chambers of the heart and describe their respective roles in circulation.
Right Atrium: Receives deoxygenated blood from the body.
Right Ventricle: Pumps deoxygenated blood to the lungs.
Left Atrium: Receives oxygenated blood from the lungs.
Left Ventricle: Pumps oxygenated blood to the body.
What arteries supply blood to the myocardium? Why is this blood supply critical?
Coronary arteries (right and left) supply oxygenated blood to the heart muscle.
This blood supply is critical for heart muscle function and preventing damage from lack of oxygen.
What is the serous membrane covering the outer surface of the heart called, and what is its function?
The serous membrane covering the outer surface of the heart is called the epicardium.
Function:
Protection: The epicardium provides a protective layer for the heart.
Lubrication: It produces serous fluid that helps reduce friction between the heart and the surrounding structures as the heart beats.
List the principal heart valves and describe their functions in controlling blood flow.
Tricuspid and Mitral Valves: Control blood flow between the atria and ventricles.
Pulmonary and Aortic Valves: Control blood flow from the ventricles into the arteries (pulmonary artery and aorta).
These valves ensure unidirectional blood flow through the heart and prevent backflow.
Identify the key landmarks of an electrocardiogram (ECG), including each wave and its significance.
P Wave: Atrial depolarization (atrial contraction).
QRS Complex: Ventricular depolarization (ventricular contraction).
T Wave: Ventricular repolarization (ventricular relaxation).
PR Interval: Time for impulse to travel through the atria and AV node.
ST Segment: Indicates ventricular contraction and recovery.
QT Interval: Duration of ventricular depolarization and repolarization.
Explain the source and physiological significance of the heart sounds.
- First Heart Sound (S1) – “Lub”
Source:
Caused by the closing of the mitral and tricuspid valves (the atrioventricular valves) at the beginning of systole (when the heart contracts).
Physiological Significance:
Marks the start of ventricular contraction and the beginning of the pumping phase. It helps prevent backflow of blood into the atria.
- Second Heart Sound (S2) – “Dub”
Source:
Caused by the closing of the aortic and pulmonary valves (the semilunar valves) at the beginning of diastole (when the heart relaxes).
Physiological Significance:
Marks the end of ventricular contraction and the beginning of ventricular relaxation. It prevents the backflow of blood into the ventricles.
